Earth's seasonal cycles can vary dramatically across short distances, even at the same latitudes, a new study suggests.

Researchers have compiled a detailed map of seasonal rhythms around the world, which shows that some physically close regions have dramatically different timing for seasonal variations such as the start and end of the growing season. These differences could contribute to high biodiversity in certain ecosystems, the development of new species and even the different types of coffee harvested in Colombia, the team said.

"Seasonality may often [be] thought of as a simple rhythm — winter, spring, summer, fall — but our work shows that nature's calendar is far more complex," study co-author Drew Terasaki Hart, an ecologist and data analyst at the Commonwealth Scientific and Industrial Research Organization (CSIRO) in Australia, said in a statement. "This is especially true in regions where the shape and timing of the typical local seasonal cycle differs dramatically across the landscape. This can have profound implications for ecology and evolution in these regions."

The idea of a simple, seasonal growing pattern works well for plants that grow at high latitudes, such as those in much of Europe and North America, researchers wrote in the study, published Aug. 27 in the journal Nature. But it doesn't work quite as well in arid or tropical ecosystems.

In the study, Terasaki Hart and his colleagues used 20 years' worth of satellite data that captured how plants reflected infrared light throughout the year to map vegetation's growth cycles around the world.

Areas on the slopes of mountains in tropical regions or that have a balmy Mediterranean climate frequently exhibited seasonal asynchrony, or differences in their seasonal cycles across short distances, the team found. In these areas, the availability of light and water was more important for the local plants' growth cycles than the temperature.

"Our map predicts stark geographic differences in flowering timing and genetic relatedness across a wide variety of plant and animal species," Terasaki Hart said in the statement. "It even explains the complex geography of coffee harvest seasons in Colombia — a nation where coffee farms separated by a day's drive over the mountains can have reproductive cycles as out of sync as if they were in opposite hemispheres."

These starkly different niches over short distances could explain why tropical regions have such high biodiversity, the team wrote in the study. Plant and animal species on different seasonal cycles would slowly diverge, reproducing at different times and possibly forming new species after many years.

The results could help explain how species evolve in other ecosystems, such as in river or ocean environments, as well as how environments are adapting to climate change, the researchers wrote in the study.

"We suggest exciting future directions for evolutionary biology, climate change ecology, and biodiversity research, but this way of looking at the world has interesting implications even further afield, such as in agricultural sciences or epidemiology," Terasaki Hart added.

Autumn is right around the corner for everyone in the Northern Hemisphere, while those in the Southern Hemisphere are gearing up for warmer spring weather. 

Depending on the part of the world in which you live, the season will change on either Sept. 22 or 23. That's because the equinox isn't a daylong event. Rather, the equinox is defined by the position of the Earth and the sun at a particular moment in time. 

Time zones aren't the only source of confusion concerning the date of the equinox. Further complicating our calendars, the autumnal equinox can occur anytime between Sept. 21 and 24. [Autumn Equinox: 5 Odd Facts About Fall] 

On Sept. 22 at 9:04 p.m. EDT (0104 GMT on Sept. 23), the sun will cross the celestial equator, or an imaginary line that projects Earth's equator into space. At this exact moment, the Northern and Southern hemispheres will receive an equal amount of sunshine, and the length of day and night will be approximately equal around the world — hence the term "equinox," which is derived from the Latin phrase meaning "equal night."

Most years, this happens on either Sept. 22 or 23. However, every once in a while, the autumn equinox can occur on Sept. 21 or 24. This happens because the length of a calendar year (365 days) is not equal to the time it takes for Earth to travel around the sun (365.25 days). To make up for this inconsistency, people have observed "leap years" for the last two millennia. By adding a "leap day" (Feb. 29) to the calendar every four years, we have managed to keep our seasons more or less consistent from year to year. 

However, leap years don't ensure that equinoxes always fall on the same date. "Because of leap years, the dates of the equinoxes and solstices can shift by a day or two over time, causing the start dates of the seasons to shift, too," according to The Old Farmer's Almanac. 

The last time the autumnal equinox fell on Sept. 21 was over a thousand years ago, and the last Sept. 24 equinox was in 1931, according to timeanddate.com. While it's been a long time since the equinox occurred on Sept. 21, we can expect to see it happen twice in the next century, first in 2092 and then in 2096. The next Sept. 24 equinox will be in the year 2303. (Keep in mind that these dates are based on Universal Time, so some time zones may not experience these equinoxes on the dates listed here.)

EDITOR'S NOTE: This article was updated on Sept. 19, 2022 to reflect the date and time of the 2022 autumnal equinox.

Originally published on Space.com.

More than 3.8 million babies were born each year in the United States on average from 2010 to 2020, according to the National Center for Health Statistics. But in which month are the most babies born, and why?

In the United States, the month with the largest number of births is typically August, with July a close second, Brady Hamilton, a demographer with the National Center for Health Statistics, told Live Science.

For example, August saw the greatest number of births in eight of the years from 2010 to 2020, Hamilton noted. July nabbed first place in three of those years — 2014, 2015 and 2020, he said.

Related: What is the birthday paradox?

In 2021, August was again the leading month, seeing 329,978 births, compared with an average of 350,067 births from 2010 to 2020. The smallest number of births in 2021 occurred in February, which saw 266,308 births, according to the National Center for Health Statistics.

Since the full course of a pregnancy is normally about 40 weeks, or a little more than nine months, these data suggest most children in the United States are conceived in November or December, Hamilton noted. "It's a fascinating question why that is," Hamilton said.

Reproduction appears to be seasonal in many living organisms — including plants, insects, reptiles, birds and  mammals — likely to help maximize their chances of reproduction over the course of their lifetimes, Micaela Martinez, an assistant professor of environmental health sciences at Columbia University in New York, and Kevin Bakker, previously an assistant research scientist at the University of Michigan and now a principal scientist at Merck, wrote in an essay for The Conversation.

In a 2014 study in the journal Proceedings of the Royal Society B: Biological Sciences, Martinez, Bakker and their colleagues noted that there was a clear pattern of births across latitudes in the United States: Northern states have a birth peak in June and July, whereas Southern states experience a birth peak later, in October and November.

The 2014 study found a similar pattern across the Northern Hemisphere, with peaks occurring later in the year the closer the location was to the equator. For instance, Finland saw the most births in late April, whereas Jamaica's births peaked in November.

So what could explain this correlation?

A 1990 study in the Journal of Biological Rhythms suggested the seasonality of human births may be linked with local temperature and day length. The extent to which temperature and day length may or may not change seasonally over the year depends in part on latitude, Martinez and Bakker noted. These environmental changes may influence the frequency of sex or how fertile men or women are, they noted. However, in their 2014 study, they note many other factors may play a role as well, such as income, culture, holidays and rainfall, making it challenging discussing whether and in what way temperature or day length might affect human births.

Understanding when most human births happen is more than just a matter of trivia, Hamilton said.

"If you're the birthing ward of a hospital, or a company that makes baby formula, or a diaper manufacturer, it's good to know what you might be facing over time," Hamilton said. "Further down the line, school systems may want to anticipate how many children may be coming in at a certain point in time, and health care systems would want to know what to expect in terms of inoculations."

Originally published on Live Science on July 27, 2010 and rewritten on Aug. 19, 2022.

When it's cold outside, you shiver and your teeth chatter. But why, exactly, do those shakes happen? Though it may not seem very effective, these reflexes evolved to generate heat to keep you warm.

Your body needs to keep a core temperature of about 98.6 degrees Fahrenheit (37 degrees Celsius). To prevent hypothermia — a dangerously low body temperature — the brain monitors the body's heat level very closely, Dr. Robert Glatter, an emergency physician at Lenox Hill Hospital in New York City, told Live Science.

If the skin surface gets too chilly, skin receptors send signals to the hypothalamus, an almond-size structure deep inside the brain. The goal of the hypothalamus is to keep the body balanced in a stable state called homeostasis by helping to control body temperature, blood pressure, hunger, thirst, mood and sleep, according to the Cleveland Clinic.

One warming trick the hypothalamus may set into motion is shivering. During shivering, your skeletal muscles — the muscles connected to the skeleton that help move the body — repeatedly tense and relax in speedy bursts, according to researchers at Oregon Health & Science University. These contractions and expansions may not only make your limbs quake but also cause your jaw muscles to twitch, "making your teeth chatter," Glatter said.

Related: Why do we grind our teeth?

Muscle contractions expend chemical energy. Although some of this energy gets converted to motion, much of it is lost as heat. Shivering relies on this process to warm the body, according to Britannica.

Shivering is distinct from other kinds of shaking your body may experience. For instance, the quivering that can result from danger or frightful situations "ultimately involves the fight-or-flight response and the production of adrenaline, which is designed to make us ready to respond to a threat by making us ready to spring into action to either run or fight," Glatter said. "Adrenaline makes our muscles ready to contract, so 'shivering' observed in this context is the effect of residual adrenaline making its way through our veins and throughout our bodies."

Hypoglycemia, or low blood sugar, "also leads to the release of adrenaline," Glatter noted. This can result in shaking, a tremor, a rapid heartbeat, anxiety, sweating and hunger.

Shivering is also distinct from a tremor, the kind of shaking sometimes seen with neurological disorders such as Parkinson's disease. "A tremor is an involuntary contraction of a muscle or muscles that results in a shaking type of movement typically in the hands, but can also result in leg, head and full-body movements," Glatter said. "A tremor occurs due to an abnormality in an area of the brain that controls movement of the muscles."

Originally published on Live Science on Feb. 8, 2013 and rewritten on June 23, 2022.

Sandwiched between blazing summer and chilly winter, autumn is the "cooling off" season. Nighttime arrives earlier, temperatures begin to drop and most vegetative growth decreases. Animals begin to prepare for the dearth of food that generally comes during the winter, gathering supplies or traveling to warmer climates.

The cycle of seasons is caused by Earth's tilt on its axis and the planet's orbit around the sun. When the axis points toward the sun, that hemisphere experiences summer. The hemisphere tilted away from the sun experiences winter. After Earth travels a quarter of the way around the sun, the axis is pointed along the planet's path, parallel to the star. 

From our perspective here on Earth, the sun travels along an imaginary line called the ecliptic, which marks the plane in which the planets orbit the sun. Another imaginary line is the celestial equator, which is a projection of Earth's equator into space. For half the year, during summer in the Northern Hemisphere, the sun appears to move along the ecliptic north of the celestial equator. During the other half of the year, it appears to be south of the celestial equator. 

The exact moment when the sun appears to arrive at the intersection of the ecliptic and the celestial equator is when autumn begins. At Earth's equator, the sun is directly overhead at noon.

These moments in time are called equinoxes, and the length of daylight and nighttime are approximately the same, according to the National Maritime Museum. The word "equinox is derived from two Latin words: aequus (equal) and nox (night). 

Day and night are not exactly 12 hours each. Because of the way the sun's light refracts in Earth's atmosphere, we can actually see the sun for a few minutes before its disk rises and for a few minutes after it has truly set. Thus, daylight on any given day lasts roughly six or seven minutes longer than it seemingly should. 

The different definitions of autumn

The autumnal equinox is the beginning of "astronomical autumn," which ends with the start of winter. In the Northern Hemisphere, that is from around Sept. 23 to about Dec. 21, though it varies from year to year, according to the MET Office. In the Southern Hemisphere, the season runs from about March 20 to June 21. 

Weather forecasters and some countries define the season as "meteorological autumn" by the three months in which the weather changes. In the Northern Hemisphere, this is September, October and November. In the Southern Hemisphere, meteorological autumn occurs in March, April and May.

Falling temperatures

Autumn brings a nip in the air. How much of a change is felt depends on the location of the area on Earth. Regions near the equator experience fairly constant temperatures throughout the year, while those farther north or south experience greater variations. This is because the equator gets a consistent amount of sun. Far northern and southern regions get less sun due to the curvature of the sun, according to the Atmospheric Radiation Measurement (ARM) program.

For the continental United States, temperatures during autumn (September through November) average 55.9 degrees Fahrenheit (13.3. degrees Celsius), according to the NOAA — which is a 2.1 F (1.2 C) increase above the 20th-century average. 

What's in a name?

Autumn, of course, is also known as fall, primarily in the United States. Ambivalence over the name of the third season of the year reflects its status as a relatively new concept. Many cultures only recognized two seasons, such winter and summer or winter and spring.

The period of transition between summer and winter came to be known as "harvest." "Autumn," a Latin word, first appeared in English in the late 14th century, and gradually gained on "harvest." In the 17th century, "fall" came into use, almost certainly as a poetic complement to "spring," according to the book "Folk Taxonomies in Early English" (Fairleigh Dickinson University Press, 2003) by Earl R. Anderson

Why do leaves change color?

In response to chilly temperatures and the changes in daylight, leaves stop producing green-tinted chlorophyll, which allows them to capture sunlight and make energy. Because chlorophyll is sensitive to the cold, certain weather conditions like early frosts will turn off production more quickly. 

Meanwhile, orange and yellow pigments called carotenoids – also found in orange carrots – shine through the leaves' washed out green. The red color in some leaves comes from anthocyanins, which unlike carotenoids, are only produced in the fall, according to the State University of New York College of Environment. They also give color to strawberries, red apples, and plums. 

But red leaves are also signal of distress. If you see leaves of a tree turning red early, in late August, the tree is most likely suffering from a fungus or perhaps a ding from a reckless driver. 

Autumn in different cultures

Autumn is generally regarded as the end of the growing season. Also known as the harvest season, autumn ushers in a time of celebration for many farming cultures when they gathered in their crops.

"Autumn, or fall, is rich with different festivals which mainly celebrate the return of light, harvest, and, like spring, rebirth through death," Cristina De Rossi, an anthropologist at Barnet and Southgate College in London, told Live Science. For example, the harvest festival in the United Kingdom is a time when people give thanks for the fruits of the land and collect food to donate to those in need.  

"Harvest celebrations tend to combine giving thanks with prayers for future abundance, to propitiate the god(s) and ensure successful crops," said De Rossi. Another example of this would be Thanksgiving, which is celebrated in the United States. It is a historical commemoration, but it has a spiritual dimension strongly associated with homecoming and giving praise for what has been bestowed upon us, explained De Rossi. 

De Rossi also points out these celebrations as further examples of fall's ties with giving thanks and rebirth:

• The Jewish festival of Sukkot, which commemorates the time spent in exile by giving thanks. 
• Halloween (All Hallows Eve) celebrations on Oct. 31 remind people of the connection with death, the spirits of those who have left this earth, and thus rebirth.  
• On the following day, Christians, especially Catholics, celebrate All Hallows Day, or All Saints' Day, when people visit their departed and bring flower to their graves.  
• In Mexico, the living celebrate their ancestors during the Day of the Dead on Nov. 2. 

Additional resources

For more on the science of autumn check out the State University of New York College of Environmental Science and Forestry webpage on: Why Leaves Change Color and NOAA's webpage on the changing seasons. 

Bibliography

• Empty Hayley Dixon, "When does Autumn really start?" The Telegraph, September 2013. 
• U.S. Department of Agriculture, "Science of fall colors", Forest Service, accessed March 2022. 
• NOAA, "Meteorological Versus Astronomical Seasons", September 2016. 
• Danielle Wesley, "First signs of autumn", Woodland Trust, August 2019. 
• Lee Mohon, "September Equinox 2021 is Coming!", NASA, September 2021. 

Summer is the warmest season of the year, falling between spring and autumn. Temperatures over the period differ based upon the location on the Earth; regions near the equator are typically warmer than those lying near the poles. This is because, due to the curve of the Earth, these places receive the most sunlight, according to Pedagogy in Action. The areas around the Earth's poles also have ice, which reflect a lot of the sun's rays.  

The summer equinox occurs when the sun passes directly above the equator because of the tilt of the Earth. When the seasons are based on the Earth's position in relation to the sun, it is called astronomical summer. In the Northern Hemisphere, astronomical summer happens on or around June 21. The North Pole is tilted at the greatest angle toward the sun at this time. In the Southern Hemisphere, summer occurs on or around Dec. 22, according to the National Oceanic and Atmospheric Administration (NOAA), when the South Pole is tilted toward the sun. 

Astronomical summer runs from the summer solstice until the autumn equinox. The summer solstice is the day of the year in which the sun is up the longest, while the equinox occurs when night and day are approximately the same length. 

There is another definition for summer, though. A meteorological season is defined as the 12 months of the year being divided up into four seasons  with three months each, NOAA states. June, July and August are considered summer, north of the equator, and December, January and February are summer to the south. During these months, temperatures tend to be higher than over the rest of the year.

Weather problems during summer

Weather in the summer grows warmer, and in some areas, the heat translates to drier temperatures. This hot, dry time of year can lead to droughts, where water is in short supply. Heat waves, times of excessively hot weather that include spikes in temperature, can also occur during the summer. Both can create a number of problems for people and wildlife. 

However, in many tropical regions, summer is the time of the "wet season," which is defined as a month where average precipitation is 60 millimeters (2.4 inches) or more, according to The British Geographer . Vegetative growth increases during this time period. If winds are changing, the increased rainfall can also usher in monsoon season, a time of violent rainy storms.

Avoid dehydration

Many deaths during summer are caused by dehydration, especially during heat waves. The Centers for Disease Control and Prevention (CDC) has found that heat waves are the deadliest extreme weather events in the United States. Staying hydrated is especially important when temperatures soar. A Huffington Post article quoted registered dietician and nutritionist Luaren Minchen as saying that “The exact amounts [of water] vary person to person, but 2 to 4 liters for active adults is a general target range to aim for to stay adequately hydrated". ). People doing vigorous exercise should drink even more.

The worst summers in history

The excessive temperatures and dry weather often associated with summer, as well as the violent monsoons, often causes rising death tolls. 

In London, 1858, temperature wasn't the only unbearable problem for the city of London in the summer of 1858. Water closets had become the new rage, and much of the raw sewage made its way to the Thames River. When the heat spiked, the stench blanketed the city. The noxious odor was only the beginning; many still drank from the river, and thousands died from diseases. In 1865, a newly designed sewer system helped prevent a repeat of the stinky summer, according to The History Channel.

Between 1923 and 1924, the town of Marble Bar in Western Australia set a world record when the 160 days between Oct. 31, 1923, and April 7, 1924, reached temperatures above 100 degrees Fahrenheit (37.7 Celsius), according to the Australian Broadcasting Commission.

Coming on the tail end of the Great Depression, the 1930s saw several years of drought and dust storms across the central United States called the Dust Bowl, 1930s. The initial drought turned farmers' fields into dust that blew across the country, occasionally traveling all the way to the Atlantic Ocean. In 1936, heat waves added to discomfort, with Yuma, Arizona, experiencing 101 consistent days of temperatures over 100 degrees F (37.7 C).

In the Chicago heat wave of 1995, approximately 739 people died   over the course of five days when the temperature hit 106 F (41 C) in July 1995, according to the University of Chicago Press. Excessive humidity caused temperatures to seem higher than 120. As more and more people cranked up the air conditioner, power grids reached their maximum capacity and burned out. This created even more problems for hospitals struggling with the increased patient load. 

In July and August, 2003, rising temperatures in Europe claimed more than 70,000 lives, according to an article in the journal Comptes Rendus Biologies. Temperatures climbed over 100 degrees, and were later determined to be higher than any summer since A.D. 1500. The high death toll makes this the most fatal heat wave in recorded history.

The world's second deadliest heat wave occurred only a few years later in Russia. With a high of 111 F (43.9 C), the excessive heat also sparked the worst drought in 130 years and fires across the country. Approximately 56,000 people died over the course of three weeks, many of them from drowning after swimming in unsafe locations or while intoxicated.

According to The Independent, the India's second deadliest heat wave occurred in India in April and May of 2015. It resulted in over 2,000 deaths from temperatures ranging 113F (45C) to 116.6F (47C), which is about 37.4 F (3C) to 44.6F (7C) higher than normal.

The hottest summer on record

2014 had the hottest summer on record, according to  NOAA's National Climatic Data Center. Extreme heat waves may become the norm in many areas. Most scientists agree that global heat records are being broken due to human created global warming, according to NASA.  However, rising temperatures won't make the world a summer-like place at all times of the year.

"There will always be seasons, and the weather will always fluctuate from day to day, month to month, and year to year," Adam Sobel, Columbia professor, atmospheric scientist and author of "Storm Surge" (Harper Wave, 2014), told Live Science. "Global warming won't change that; it will just make all the seasons a little warmer, on average, than they would have been otherwise." 

The history of summer and the U.S. road trip

Summer is road trip time. Hundreds of thousands of families and friends take advantage of sunny, warm weather and hit the road, heading for beaches and lakes, national parks and reserves. "Utilizing the summer as time away, listening to music, watching the scenery go by, we reenergize. Road trips are about reconnecting with family, friends and ourselves. People’s fondest memories about childhood are usually linked to summers, vacation and family road trips," Talia Wagner, a Los Angeles based marriage and family therapist told Live Science.

The summer road trip is deeply rooted in American culture. It began in the aftermath of World War II, American society experienced many changes to everyday living. At roughly the same time that the infrastructure of roads and highways underwent increased development and improvements, cars became more affordable and attainable to the average family. This culmination fueled the popularity of the summer road trip, explained Wagner.

"Road trips came to symbolize freedom and independence, values that Americans hold dear. It is no wonder then that every summer, when children are out of school and the rising heat makes us restless, people start thinking about vacations," said Wagner.

Additional resources

To discover more about the worst heat waves in history, try this article from The Telegraph. Or you can read The Farmer's Almanac exploration of the first day of summer 2022.

Bibliography

• Pedagogy in Action
• National Oceanic and Atmospheric Administration (NOAA)
• The British Geographer
• Centers for Disease Control and Prevention (CDC)
• Kristen Adaway "You're Definitely Not Drinking Enough Water This Summer" Huffington Post, 2018 
• Heatwaves Throughout History - History Channel
• Australian Broadcasting Commission
• University of Chicago Press
• Comptes Rendus Biologies
• Ben Tufft: "Extreme temperatures kill more than 2,000 people in India's second deadliest heat wave" The Independent, 2015
• NOAA's National Climatic Data Center
• Scientific Consensus: Earth's Climate is Warming

Spring is the season during which the natural world revives and reinvigorates after the colder winter months. During spring, dormant plants begin to grow again, new seedlings sprout out of the ground and hibernating animals awake. 

What most people call spring relies on the astronomical definition of the word. Defined by the angle of Earth's tilt toward the sun, astronomical spring relies on equinoxes and solstices to define it. Spring is generally considered the period between the spring equinox and the summer solstice. 

Equinoxes are days during the year when day and night are almost equal. There are two equinoxes each calendar year, one in the spring and one in the fall. The spring, or vernal, equinox occurs around March 20 in the Northern Hemisphere and around Sept. 22 in the Southern Hemisphere.

According to the National Oceanic and Atmospheric Administration (NOAA), spring is one of two times when the Earth's axis is not pointed toward or away from the sun. In the Northern Hemisphere, the North Pole is tipped at its greatest angle toward the sun during the summer solstice, which occurs around June 21. In the Southern Hemisphere, around December 21, it is the South Pole's turn to be nearer. 

As such, in the Northern Hemisphere, astronomical spring runs from March 21 to June 21, while in the Southern Hemisphere it encompasses Sept. 21 to Dec. 21, though the dates may shift slightly from year to year.

The air may lose its winter chill before the middle of March or September, though. Weather forecasters define meteorological spring as a three-month period based on rising temperatures. North of the equator, meteorological spring takes place in March, April and May, while in the south it is characterized by the months of September, October and November, according to NOAA.

Spring awakening

In the hemisphere that is tilted closer to the sun, temperatures become warmer. Warmer temperatures means the ground, which may have frozen over the winter months, grows softer and more yielding to plants. Spring is often marked by increased rainfall, which helps to water the infant seeds taking root in the ground.

Animals that spent the winter in hibernation come out of their dens, while those that traveled to warmer regions return. Many animals give birth in the spring. Winter coats are shed by those that sported them, and some animals may change coloration to blend in with their new surroundings.

The rising rainfall of spring may bring with it an increase in flooding as melting snow overwhelms rivers. Spring may also boast storms, as warm air from the equator combines with still-cool air farther north or south.

Tornadoes are common during the spring in the United States as air of different temperatures combine. The world's deadliest tornado occurred April 26, 1989, in Bangladesh. It left a mile (1.6 kilometer) wide path for 10 miles (16 k), killing 1,300 people and leaving 80,000 people homeless, according to The Weather Channel.

One of the first signs that spring has sprung are the presence of tree buds. A plant’s buds act as a shield for the delicate flowers inside. Flowers of different shapes, sizes and forms come with individual and distinct protection. Throughout winter these buds remain closed and dormant, surviving the cold until their time comes to thrive in the spring, making a vibrant emergence from their compact casing. While it’s usually easy to distinguish a species from its distinct flowers, buds can have more subtle differences. This visual guide to the more common tree buds should help you identify them.

Here’s how to identify them:

A time of celebration

Many cultures celebrate the return of spring, the blossoming of nature or the rise of the vernal equinox.

In Japan, the annual blossoming of cherry trees has become a significant national event. Hanami, or cherry blossom viewing, is a time for festivals and gatherings at parks and shrines, according to the Japan National Tourism Organization. Cherry blossoms, or sakura, symbolize the transience of life, which is a major theme in Buddhism.

People of the Jewish faith celebrate Passover, which commemorates when the Jewish people were freed from slavery to Egypt, according to History. The day falls on the first full moon after the northern spring equinox and lasts for seven days.

Spring in many countries with a strong Christian tradition is marked by Easter, which celebrates the resurrection of Jesus Christ and his triumph over physical death. However, it has roots in older traditions.

"Easter is derived from a much older celebration of fertility and rebirth, the Celtic festival of Ostara," Cristina De Rossi, an anthropologist at Barnet and Southgate College in London, told Live Science. "The bunnies and the eggs are symbolic of fertility and reproduction." 

Albania celebrates Dita e Verës on March 14, which also stems from pagan roots. Pilgrimages were once made to the peaks of the Albanian mountains, where prayers were offered to the Sun God for a prosperous year.

Mayday celebrations are common around Europe. The Maypole dance is a popular folk festival, particularly in parts of Germany and the United Kingdom. "The pole symbolizes sacred trees, the world axis, the phallus, growth and regeneration," said De Rossi.

Additional resources

For more information about Earth's seasons here’s a handy guide by the California Academy of Science. Also, check out the MET Office’s "10 facts about spring" for some rapid-fire facts. 

Bibliography

National Weather Service, ”Why do we have seasons”, accessed in March 2022.

Met office, “The Equinox and Solstice”, accessed in March 2022. 

Encyclopedia Britannica, “Spring”, accessed in March 2022. 

National Trust, “7 signs of spring everyone should know”, accessed March 2022.

Winter, the coldest season of the year, comes between autumn and spring. It is associated with plunging temperatures and icy weather, but its impact and timing change according to location. The farther an area lies from the equator, the colder temperatures it experiences. Temperatures in equatorial regions stay relatively constant despite the shifting seasons. This is because, due to the curve of the Earth, the equatorial areas get more sunlight, according to the BBC.

Shifting time frames

Most people think the coldest season begins during the winter solstice, but there are in fact two definitions of winter. 

Astronomical winter — what most people think of as winter — is defined by Earth's position around the sun and ranges from the winter solstice to the vernal equinox. The winter solstice marks the time when the sun passes directly over the equator. In the Northern Hemisphere, it falls around December 21, and in the Southern Hemisphere it occurs around June 21, according to the National Oceanic and Atmospheric Association (NOAA). It is the shortest day of the year, and has been noted and celebrated by a wide variety of cultures around the world. 

At the time of the winter solstice, the corresponding pole is tipped about 23.5 degrees away from the sun, according to the NWS. On that day in the Northern Hemisphere, the North Pole is farther from the heat-producing star, while the Southern Hemisphere, which experiences summer, is closer. 

But anyone who regularly engages in winter sports might tell you that winter weather tends to fall before the middle of December or June. Meteorological winter falls sooner, spanning the three-month period from December to March, according to NOAA. It is based on the annual temperature cycle and the calendar rather than Earth's journey around the sun. 

Winter in the hemispheres

People living in the Northern Hemisphere are more likely to experience a colder winter than those in the Southern Hemisphere, according to physicist Dr. Christopher Baird. In fact, all of the coldest countries in the world are located in the Northern Hemisphere. These include Kazakhstan, Russia, Greenland, Canada, the United States, Iceland, Finland, Estonia and Mongolia, according to Earth & World. (Though not a country, Antarctica, in the Southern Hemisphere, is technically the coldest region on Earth.)

So why do so many countries in the Northern Hemisphere get much colder than those in the Southern Hemisphere? This occurs because there are a few major differences between the two hemispheres when it comes to factors that affect climate, according to Public Broadcasting Service (PBS): the size of a land mass, how close the land is to a polar region and the amount of ocean coverage. 

First, there are larger masses of land at higher latitudes in the Northern Hemisphere, even within the Arctic Circle, such as Greenland, the northern parts of Norway, Sweden, Finland and Iceland and the frigid tundras of North America, Europe and Asia. According to World Atlas, 68%of Earth’s land is in the Northern Hemisphere. 

In contrast, the bigger land masses in the Southern Hemisphere are closer to the equator and no countries are located on or below the Antarctic Circle — only the frozen unpopulated continent of Antarctica. 

Another important temperature moderator is the ocean. Oceans cover 81% of the Southern Hemisphere, compared to only 61% in the Northern Hemisphere, according to the book "Atmospheric Temperature Profiles of the Northern Hemisphere" (Springer, 2012). All of this water, which stores and conducts heat better than land, helps keep temperatures somewhat warmer and more stable.

Adapting to the weather

Winter brings many changes to the world around it. During winter, some animals migrate, which means moving to another area for a season's time. Usually, animals go south to warmer areas during the winter, according to the book "Animal Movement Across Scales". In response to global warming, some bird species now arrive in spring breeding grounds earlier, and lay eggs earlier, according to a report by the World Wildlife Fund (WWF). In Europe, some birds that normally migrate have stopped migrating altogether, according to the report. 

Species movement has to do with changes in habitat, as well, Keith Peterman, a professor of chemistry at York College of Pennsylvania, and Gregory Foy, an associate professor of chemistry at York College of Pennsylvania, explained to Live Science. Migration isn't just about staying warm. Animals can be forced out of their normal habitat because of changes in their food supply and introduction of new bacteria or viruses (due to the change in climate) where they have poor resistance.

Other animals begin a period of hibernation during the winter, passing much of the season in a near-sleep state. Because many plants die or are dormant, animals may stockpile food to help them through winter periods, according to World Atlas.

In addition to changing their locations and habits, some animals may also change their appearance. Animals such as hares and foxes may change their coloration to blend into snowy landscapes better, according to the journal Biological Reviews. For example, the snowshoe hair is brown during warm months, but then turns white to blend in with the snow, according to National Geographic. Other animals might grow thicker fur to help them to stay warm.

Extreme temperatures and unusual winters

Antarctica currently boasts the lowest temperature on record. On Aug. 10, 2010, scientists recorded a temperature of minus 136 degrees F (minus 93.2 degrees C) on Antarctica's East Antarctic Plateau, according to NASA. 

The lowest temperature in the United States was set in Alaska on Jan. 23, 1971, according to The Weather Channel. The mercury plummeted to minus 80 F (minus 62 C) in Prospect Creek, north of Fairbanks. 

Although winter tends to be a hard time for animals and humans alike, some winters host more extreme weather than others. Some of the extreme storms are listed below:

Known as the Storm of the Century, a storm system that formed over the Gulf of Mexico in March 1993 blanketed the Eastern United States with snowfall, scattered tornadoes and hurricane-force winds of up to 120 mph (193 km/h), according to NOAA. The storm affected 26 states, with snow falling as far south as the usually sunny Jacksonville, Florida. Drifts piled up as high as 35 feet (11 meters), and many Southern states, unprepared for the need for large-scale snow removal, shut down completely.

In Feb. 2012, a deadly cold wave ravaged Europe, causing more than 800 deaths. Temperatures reached as low as minus 38.6 degrees Fahrenheit (minus 39.2 Celsius), and snow blanketed several countries, setting records for many of them. The second-longest river in Europe, the Danube, froze, as did the canals of Venice. Northern Africa also felt the breath of the storm, with snow covering parts of the Sahara. More than 100,000 people were trapped by snow and ice.

On Nov. 11, 1940, the "Armistice Day blizzard" quickly plunged temperatures from 60 degrees down to single digits in less than 24 hours, according to the Star Tribune. Hurricane-force winds — up to 80 mph (129 km/h) — pushed snow into 20-foot drifts across the Midwest. The surprise weather change claimed 49 lives, many of them duck hunters trapped in remote areas.

In March 1888, a snowstorm blanketed the northeastern United States, from Maine down to Washington, D.C., with 55 inches (139.7 centimeters) of snow, according to the History Channel. Over four feet (1.2 meters) of snow dropped in Connecticut and Massachusetts, while New York and New Jersey boasted almost three and a half feet (one meter). The storm sank 200 ships and killed 400 people, according to the New England Historical Society.

In the winter of 1783, temperatures dropped significantly in Europe, reaching as low as 3.6 degrees F (2 degrees C).

Historically, the Little Ice Age, which occurred between the 14th and 19th centuries, was a significant  period of extreme cold, according to the American Geophysical Union. Several volcanic eruptions triggered the expansion of Arctic sea ice and set off a chain reaction of lower temperatures around the world, according to a study published in the journal Geophysical Research Letters. 

The climate has been tied to many trends and events, according to the History Channel, including the Black Death, the Thirty Years' War, witch hunts on both sides of the Atlantic, the French Revolution and the invention of the bicycle.

Staying warm

Cold winters can quickly bring on life-threatening medical conditions, such as hypothermia. Hypothermia is when a human's body temperature drops below 95 F (35 C), according to the Mayo Clinic. Cold temperatures and wind chill can make a person's body temperature drop in just minutes. 

The cold temperatures can also cause frostbite, the freezing of skin and tissue. Cold temperatures are just one factor when it comes to frostbite susceptibility. "Other factors also come into play including the age/size of the individual (e.g., quicker onset in small children) or if an individual has less than optimal circulation to distal body parts such as hands/finger/feet/toes," said Dr. Nicholas Lorenzo, the chief medical officer with MeMD, a web-based health services provider. 

To avoid hypothermia and frostbite, it is important to keep all skin covered and dry during cold weather. Once a person has hypothermia or frostbite, the primary treatment is rewarming the patient.

Additional resources

To find out when the midpoint of winter is, read this article by SPACE.com. Additionally, you can read more about the temperatures in Antarctica at the British Antarctic Survey website.

Bibliography

"Atmospheric Temperature Profiles of the Northern Hemisphere". Young Yee, Kueyson Y. Yee, Erik Y. Yee. Springer Science & Business Media (2012). https://books.google.com/books?id=vU7onXXCVc4C&printsec

"Animal Movement Across Scales". Chapman, B. B., Hulthén, K., Wellenreuther, M., Hansson, L. A., Nilsson, J. Å., & Brönmark, C. (2014). https://www.researchgate.net/profile/Christer-Broenmark/publication/299888982

"Function and underlying mechanisms of seasonal colour moulting in mammals and birds: what keeps them changing in a warming world?" Biological Reviews (2018). https://onlinelibrary.wiley.com/doi/full/10.1111/brv.12405

"Unusual Volcanic Episode Rapidly Triggered Little Ice Age Researchers Find". American Geophysical Union (2012). https://news.agu.org/press-release/unusual-volcanic-episode-rapidly-triggered-little-ice-age-researchers-find/

Seasons are periods of the year with distinct weather conditions and day lengths. 

The four seasons — winter, spring, summer, autumn — can vary significantly in characteristics and can prompt changes in the world around them. Here, we explore the seasons of the year in more detail. 

Attributes of the seasons may vary by location, but there are still broad definitions that cross most of the boundaries.

Spring

In the spring, seeds take root and vegetation begins to grow. The weather is warmer and often wetter. Animals wake or return from warmer climates, often with newborns. Melting snow from the previous season, along with increased rainfall, can cause flooding along waterways, according to the Federal Emergency Management Agency (FEMA).  

Summer

In the summer, temperatures may increase to the hottest of the year. If they spike too high, heat waves or droughts may cause trouble for people, animals, and plants. For example, in the summer of 2003, the high temperatures claimed more than 30,000 lives, according to Encyclopedia Britannica. Rainfall may increase in some areas, as well. Others may receive less water, and forest fires may become more frequent.

Autumn (Fall)

In the autumn, or fall, temperatures cool again. Plants may begin to grow dormant. Animals might prepare themselves for the upcoming cold weather, storing food or traveling to warmer regions. 

Various cultures have celebrated bountiful harvests with annual festivals. Thanksgiving is a good example. "Thanksgiving in the United States is a historical commemoration but it has a spiritual dimension strongly associated with homecoming and giving praise for what has been bestowed upon us," Cristina De Rossi, an anthropologist at Barnet and Southgate College in London, told Live Science.  

Winter

Winter often brings a chill. Some areas may experience snow or ice, while others see only cold rain. Animals find ways to warm themselves and may have changed their appearance to adapt. "In a similar way to the Autumnal theme, Winter festivals celebrate the return of the light during a time of deepest physical darkness," said De Rossi. The Indian festival of Diwali, for example, which takes place between October and November, celebrates the triumph of righteousness, and light over darkness. 

Seasons are not the same everywhere

The timing and characteristics of the seasons depend upon the location on Earth. Regions near the equator experience fairly constant temperatures throughout the year, with balmy winters barely discernible from warm summers. This is because it gets fairly constant light from the sun, due to its position on the outer curve of the Earth, according to the Atmospheric Radiation Measurement (ARM) program.

For areas to the north and south, the seasons can change more significantly. People closer to the poles might experience icier, more frigid winters, while those closer to the equator might suffer hotter summers. 

Other factors can also affect the weather and temperature over the seasons; some areas experience dry summers as temperatures spike, while others might call summer their "wet season." A wet season is when a majority of a country or region's annual precipitation occurs, according to the Met Office. Mountainous regions might experience more snowfall than plains within the same latitude, while oceanfront property could see an increase in violent tropical storms as the weather shifts.

The time of year a region experiences a season depends on whether it is in the northern or southern hemisphere. The Southern Hemisphere experiences winter while its northern neighbors encounter summer; the north sees the slow blossom of spring while the south brings in the autumn harvest.

What causes the seasons?

The cycle of seasons is caused by our planet's tilt toward the sun. The Earth spins around an (invisible) axis. At different times during the year, the northern or southern axis is closer to the sun. During these times, the hemisphere tipped toward the star experiences summer, while the hemisphere tilted away from the sun experiences winter, according to NOAA.

At other locations in Earth's annual journey, the axis is not tilted toward or away from the sun. During these times of the year, the hemispheres experience spring and autumn.

The astronomical definition of the seasons relates to specific points in Earth's trip around the sun. The summer and winter solstice, the longest and shortest day of the year, occurs when Earth's axis is either closest or farthest from the sun. The summer solstice in the Northern Hemisphere occurs around June 21, the same day as the winter solstice in the Southern Hemisphere, according to NOAA. The south's summer solstice occurs around December 21, the winter solstice for the north. In both hemispheres, the summer solstice marks the first day of astronomical summer, while the winter solstice is considered the first day of astronomical winter.

Equinoxes are another significant day during Earth's journey around the sun. On these days, the planet's axis is pointed parallel to the sun, rather than toward or away from it. Day and night during the equinoxes are supposed to be close to equal. The spring, or vernal, equinox for the northern hemisphere takes place around March 20, the same day as the south's autumnal equinox. The vernal equinox in the southern hemisphere occurs around September 20, when people in the north celebrate the autumnal equinox. The vernal equinox marks the first day of astronomical spring for a hemisphere, while the autumnal equinox ushers in the first day of fall.

But changes in the weather often precede these significant points. The meteorological seasons focus on these changes, fitting the seasons to the three months that best usher them in. December to February marks meteorological winter in the Northern Hemisphere and meteorological summer in the southern. March, April, and May are lauded as spring or autumn, depending on the location, while June through August are the months of summer for the north and winter for the south. September, October, and November conclude the cycle, ushering in fall in northern regions and spring in southern, according to NOAA.

The seasons can bring a wide variety to the year for those locations that experience them in full. The weather in each one may allow people to engage in activities that they cannot perform in others — skiing in the winter, swimming in the summer. Each season brings with it its own potential dangers, but also its own particular brand of beauty.

Additional resources

Explore the seasons in more detail with this educational material from Lumen Learning. Earth is not the only planet with seasons, if you would like to learn more about seasons on other planets check out this article from NASA.  Discover what causes the seasons with this informative piece from the National Weather Service. 

Bibliography

• De Paor, Declan G., et al. "Exploring the reasons for the seasons using Google Earth, 3D models, and plots." International Journal of Digital Earth 10.6 (2017): 582-603. 
• Khavrus, Vyacheslav, and Ihor Shelevytsky. "Geometry and the physics of seasons." Physics Education 47.6 (2012): 680. 
• Yolen, Jane. Ring of Earth: A Child's Book of Seasons. StarWalk Kids Media, 2014. 

Spring will officially arrive on Saturday morning (March 20) with the occurrence of the vernal equinox.

That occurs when the sun will be positioned directly over the Earth's equator at 09:37 Universal Time; 5:37 a.m. Eastern Daylight Time or 2:37 a.m. Pacific Daylight Time. At that particular moment, the sun will appear to shine directly overhead from a point 5 miles (8 kilometers) south of Meru, in Kenya; a city of approximately 241,000 residents. 

Until the occurrence of the summer solstice on June 20, the sun will appear to migrate northward and the length of daylight in the Northern Hemisphere will continue to increase. As the altitude of the midday sun gets progressively higher, the arc that it takes across the sky will also increase. On the date of the equinox, the sun will rise due east and will set due west. But during the coming days and weeks, as the sun's direct rays are concentrated more and more on the Northern Hemisphere, its rising and setting positions will become increasingly oriented more to the north of due east and north of due west.  

Related: The 2020 vernal equinox was the earliest spring in 124 years

Your clenched fist held at arm's length measures roughly 10 degrees in width. On the first day of summer, as seen from mid-northern latitudes, the sun will be rising not due east, but 33 degrees (or a bit more than "three fists") to the north (left) of due east. And a bit more than 15 hours later, it will be setting not due west, but 33 degrees to the north (right) of due west. 

Our seasons take place because as our planet revolves around the sun, its axis is tilted at a 23.5-degree angle. This tilt causes different latitudes on Earth to receive varying amounts of heat and light from the sun throughout the course of the year. For the Northern Hemisphere, the June solstice marks the start of the summer season and occurs when the direct rays of the sun shine down on that part of the globe 23.5 degrees north of the equator — the so-called Tropic of Cancer. The December solstice marks the beginning of winter, when the direct rays of the sun are shining down on that part of the globe 23.5 degrees south of the equator — called the Tropic of Capricorn. 

The March and September equinoxes occur when both the Northern and Southern Hemispheres equally face the sun and all parts of the world have the sun above the horizon for exactly 12 hours, and below the horizon for exactly 12 hours.  

Equal days and equal nights: The equinox.       

Well … that's not exactly true.

Inequal day and night

A complication revolving around the vernal equinox concerns the length of day versus night.  Since grammar school we all have been taught that on the first days of spring and autumn, that day and night are equal to exactly 12 hours all over the world. Yet, if you check the calculations made by the U.S. Naval Observatory or the sunrise/sunset tables in any reputable almanac, you will find that this is not so. In fact, on the days of the spring and fall equinox the length of time that the sun is above the horizon is actually longer than the time it spends out of sight below the horizon by several minutes.

Every year around this time, almost like clockwork, I will get an email from someone who was studying the weather page of his or her newspaper, looking at the section listing the times of sunrise and sunset and noticing that something appears to be wrong. The difference in the number of hours separating sunrise and sunset on the day of equinox are not equal at all.

Check out New York City. As the table below shows, days and nights are equal not on the equinox, but actually, a few days earlier, on Saint Patrick's Day (March 17):

One factor is that the moments of sunrise and sunset are considered when the top of the sun, and not its center, is on the horizon. This alone would make the time of sunrise and sunset a little more than 12 hours apart on these days. The sun's apparent diameter is roughly equal to half a degree.

It's an illusion 

But the main reason that this happens can be attributed to our atmosphere; it acts like a lens and refracts (bends) its light above the edge of the horizon. In their calculations of sunrise and sunset times, the U.S. Naval Observatory routinely uses 34 minutes of arc for the angle of refraction and 16 minutes of arc for the semi diameter of the Sun's disc. In other words, the geometric center of the sun is actually 0.83º below a flat and unobstructed horizon at the moment of sunrise. 

Or, put in another way, when you watch the sun either coming up above the horizon at sunrise or going down below the horizon at sunset, you are actually looking at an illusion – the sun is not really there, but actually is below the horizon.

As a result, we actually end up seeing the sun for a few minutes before its disk actually rises and for a few minutes after it has actually set.  Thus, thanks to atmospheric refraction, the length of daylight on any given day is increased by approximately six or seven minutes.

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Follow us on Twitter @Spacedotcom and on Facebook.   

The Sphinx had a "distinctive astronomical" moment with the sun during the spring equinox when, in a shining flourish, the sun set on the shoulder of the half-man, half-lion statue on March 19, according to the Egypt Ministry of Antiquities.

This phenomenon happens only twice a year, during the spring in March and the fall equinox in September, according to the ministry. 

During the equinox, Earth's axis doesn't point toward or away from the sun, meaning that the Northern and Southern hemispheres receive equal amounts of the sun's light. In other words, the day and the night are equal in length.

Related: Day and night are perfectly balanced in spring equinox photo snapped from space

It's well known that cats enjoy basking in the sun, and the 241-foot (74 meters) tall Sphinx is no exception. The mythical half-man, half-lion is carved out of limestone bedrock. Its face might show the likeness of Pharaoh Khafre, the fourth king of ancient Egypt's 4th dynasty (2575 B.C. to 2465 B.C.), who had the second and third Pyramids of Giza built, according to Encyclopedia Britannica.  

The Sphinx is also strategically placed for the summer solstice in June, when the sun sets between the pyramids of pharaohs Khufu and Khafre.

The Sphinx's position during the equinoxes and summer solstice suggests that the ancient Egyptians purposefully positioned the hybrid lion-man statue. "This phenomenon proves that archaeologists were wrong when they said that the ancient Egyptians had found an ancient rock by accident and turned it into a statue of a human face and a non-human body," the Egypt Ministry of Antiquities wrote in a Facebook post. 

Other ancient cultures also built large monuments that captured the fleeting moments during the solstices and equinoxes, including Stonehenge in England, a "calendar-rock" in Sicily, a Neolithic henge in Germany and a Maya city in what is now Tulum, Mexico.

• 6 ancient tributes to the winter solstice
• Earth pictures: Iconic images of Earth from space
• Black marble Images: Earth at night

Originally published on Live Science.

A man in North Carolina died from a rare "brain-eating" amoeba infection after swimming in a lake at a local water park, according to news reports.

The 59-year-old man became ill after visiting Fantasy Lake Water Park, a man-made lake in Cumberland County, on July 12, according to The New York Times.

The man tested positive for Naegleria fowleri, a single-celled organism that's naturally found in warm freshwater, such as lakes and rivers, the North Carolina Department of Health and Human Services (NCDHH) said in a statement. In the U.S., most infections occur in southern states, particularly during the summer months after it has been hot for prolonged periods, which raises the water temperature, NCDHH said. [5 Key Facts About Brain-Eating Amoeba]

Swallowing Naegleria fowleri in water will not cause an infection. But if water containing this amoeba goes up the nose, the organism can enter the brain and be fatal — the amoeba destroys brain tissue, which results in brain swelling and usually death, according to the Centers for Disease Control and Prevention (CDC).

Still, infections are extremely rare. From 1962 to 2018, there were just 145 cases of Naegleria fowleri reported in the U.S., according to NCDHH. But the illness has a high fatality rate — of the 145 cases, just 4 people survived.

"Our sympathies are with the family and loved ones," epidemiologist Dr. Zack Moore said in the statement. "People should be aware that this organism is present in warm freshwater lakes, rivers and hot springs across North Carolina, so be mindful as you swim or enjoy water sports."

There is no rapid test for Naegleria fowleri in water — identifying the organism can take weeks, according to the CDC. This means that people who go swimming in warm freshwater should assume that there is a low risk of infection, the CDC says.

If you choose to go swimming in warm freshwater, you can try to avoid having water go up your nose by holding your nose closed, using nose clips or keeping your head above water, the CDC says. People can also lower their risk by avoiding swimming in warm freshwater during periods of particularly high water temperature and low water levels, the NCDHH said.

In 2016, an 18-year-old woman from Ohio died from Naegleria fowleri after going white-water rafting at an outdoor recreation center in North Carolina.

• 10 Bizarre Diseases You Can Get Outdoors
• 8 Awful Parasite Infections That Will Make Your Skin Crawl
• 27 Devastating Infectious Diseases

Originally published on Live Science.

Summer is the most common season for U.S. teens and adults to try illegal or recreational drugs for the first time, a new study finds.

The study researchers analyzed information from more than 394,000 Americans ages 12 and older who completed a yearly survey on drug use between 2011 and 2017. Participants were asked whether they had used certain drugs — including LSD, marijuana, cocaine and ecstasy (also known as MDMA or molly) — and what month and year they initiated use.

During the summer (June through August), more people first tried these drugs, compared with other times of year. The findings were published today (July 23) in the Journal of General Internal Medicine. [7 Common Summer Health Concerns]

For example, 34% of people who said they'd begun using LSD in the previous two years had first tried the drug during the summer months. And among those respondents who had recently started using marijuana, cocaine or ecstasy, about 30% had initiated use during the summer. That compares with fewer than 25% of recent initiates of LSD, marijaua, cocaine or ecstasy who said they'd started using the drugs during each of the other three seasons of the year.

The researchers hypothesized that the uptick in drug initiation during the summer months may be due, in part, to people having more leisure time during the summer. Outdoor social activities, such as musical festivals, are more common in the summer and may increase a person's chances of exposure to drugs or the individual's willingness to use them, the authors wrote in the study.

"Parents and educators who are concerned about their kids need to educate them year-round about potential risks associated with drug use, but special emphasis appears to be needed before or during summer months, when rates of initiation increase," study senior author Joseph Palamar, an associate professor in the Department of Population Health at the New York University School of Medicine, said in a statement.

First-time drug users may be unfamiliar with the drugs' effects, which may put these individuals at higher risk of harm, the authors said.

Still, the problem of illegal drug use isn't going away anytime soon, and each year, millions of Americans try LSD, marijuana, cocaine or ecstasy for the first time.

People who do decide to use illegal or recreational drugs for the first time should educate themselves about the drugs' side effects, Palamar said. He also recommended having the company of trusted friends when using a drug for the first time and making sure to drink enough fluids and get enough rest to avoid dehydration, exhaustion and heat stroke.

More research is needed to determine why summer is a risk factor for drug initiation, as well as the particular situations that lead people to use drugs for the first time, the authors said.

• 6 Party Drugs That May Have Health Benefits
• 9 Weird Ways You Can Test Positive for Drugs
• Trippy Tales: The History of 8 Hallucinogens

Originally published on Live Science.

Before you fire off a bunch of bottle rockets this July Fourth, spare a thought for your fingers, toes and other extremities. Injuries from fireworks send thousands of Americans to the emergency room around this time of year, new data shows.

According to the U.S. Consumer Product Safety Commission (CPSC), there were an estimated 9,100 fireworks-related injuries treated in U.S. emergency rooms in 2018; and of these, about 5,600 occurred in the one-month period around July Fourth (from June 22 to July 22). That's about 190 injuries per day around July Fourth.

In addition, at least five people died from fireworks-related injuries in 2018, and four of these deaths occurred during the week of July Fourth, the CSPC said. [The Weirdest Fireworks Injuries Ever]

The CSPC also warned against letting children use fireworks: Overall, the highest rate of fireworks-related injuries occurred among children ages 10 to 14 years old.

"Don't make the emergency room part of your holiday; don't let children play with fireworks."," Dr. Sarah Combs, an emergency room doctor from Children's National Medical Center in Washington, D.C., said in a statement. About 44% of overall injuries were burns, most commonly to the hands, fingers and arms, the CPSC said.

Firecrackers were the No. 1 cause of people's fireworks-related injuries, accounting for nearly 20% of injuries. And sparklers were a major cause of injuries for young children, accounting for more than half of total injuries among those under age 5.

Sparklers may seem innocent enough, but they can reach temperatures of around 2,000 degrees Fahrenheit (1,093 degrees Celsius), the CPSC said. "At those high temperatures, within two to three seconds [a] child can sustain what we call a 'full thickness' third-degree burn down to the bone," Combs said at a news conference on Wednesday (June 26).

Among the five fireworks-related deaths that occured in 2018, all involved the use of reloadable aerial devices, such as mortar-shell fireworks. All of the victims were males ages 16 to 49.

In one case, an 18-year-old man in Iowa launched mortar shells from a tube taped to a helmet on this head. But one of the ignited shells got stuck in the tube and didn't launch. It soon exploded on top of the victim's head, causing him to fall to the ground. The man was taken to the hospital, but died the next day due to his injuries, the CSPC said.

The agency has received a total of 121 report of fireworks-related deaths from 2003 to 2018.

To prevent injuries and deaths related to fireworks, the CSPC recommends the following:

• Make sure consumer fireworks are legal in your area before buying them.
• Never use professional-grade fireworks.
• Don't buy fireworks that are packaged in brown paper, as this is often a sign that the fireworks were made for professional displays.
• Never let young children play with or ignite fireworks, including sparklers.
• Never try to relight or handle malfunctioning fireworks.
• Never place any part of your body directly over a fireworks device when lighting the fuse. Move to a safe distance immediately after lighting fireworks.
• Keep a bucket of water close by in case of fire.
• When fireworks have completed burning, douse the product with water from a bucket or hose before discarding.

Originally published on Live Science.

• 50 Fabulous 4th of July Facts: History of Independence
• Science of Summer: How Do Fireworks Work?
• 5 Dazzling Facts About Fireworks

Originally published on Live Science.

As the weather warms and pollen begins its dance across the sky, some people's bodies hurl them into a storm of watery eyes, runny noses and sneezing fits.

But sometimes the spring and summer months also bring bouts of tiredness. Can people with allergies also blame this on seasonal allergens? The answer is yes; there are several ways that seasonal allergies can make us feel low on energy.

An allergy or allergic reaction is, by definition, a fight that the body puts up when it's faced with a foreign invader, such as pollen, said Dr. Kara Wada, an allergist and immunologist at The Ohio State University Wexner Medical Center. [Can You Learn Anything While You Sleep?]

"The body expends a lot of energy in making all of the cells, proteins and all of the other substances" that build up during an allergic response, also known as inflammation, she said.

This energy expenditure wears out the body and "some of the same chemical signals … in addition to fighting off what it sees as an enemy, makes you feel unwell" and rundown, she said. This effect in seasonal allergies is like a watered-down version of the extreme tiredness that can overtake people who eat something they're allergic to.

Allergies can also indirectly cause you to feel tired by robbing you of sleep. "It's not uncommon to hear that people have poorer quality sleep from their allergies," Wada told Live Science, especially "if their nose is so stuffed up they have to breathe from their mouth or [if] post-nasal drip wakes them up in the middle of the night."

Why exactly do allergies make sleeping challenging? In essence, the body fights what it deems as foreign substances in the body by sending its little molecular army to the site of the invasion, causing inflammation there. Inflammation or swelling of the lymphatic tissue behind the nose, called the adenoids, could lead to a person breathing with their mouth open, which, in turn, can disrupt sleep, said Dr. Gloria Riefkohl, a pediatrician at Nicklaus Children's Hospital in Miami.

This disruption happens because when the adenoids get larger, they can cause obstruction in nasal passageways, which can reduce the amount of oxygen we need to breathe comfortably, said Dr. Priyanka Seshadri, a pediatric resident also at Nicklaus Children's Hospital.

"Seasonal allergies can definitely also affect concentration," she said. "Kids could be misdiagnosed with ADHD [attention-deficit/hyperactivity disorder] or a learning disability when sometimes it is just really bad allergies."

"Especially if you're not getting good quality sleep, we know that that can result in not as clear thinking, not as much focus," Wada said. "That's not going to lead to being your best self [while trying to work]."

Finally, people can become drowsy while trying to cure their allergies. The most common allergy-fighting medications are called antihistamines (histamines are a chemical the body releases during allergic reactions). But a common side effect of some of these medications, such as diphenhydramine (brand name Benadryl), is drowsiness, Riefkohl said.

• Booze Snooze: Why Does Alcohol Make You Sleepy, Then Alert?
• Why Are Pollen Allergies So Common?
• Why Do People Get Sick When the Seasons Change?

Originally published on Live Science.

Summer doesn't begin for two more days, but oceanographers and climatologists are already sounding the alarm about stunning, dangerous ice melts going on right now in Greenland, according to the Agence France-Presse (AFP).

The vast island nation locks away enough fresh water in its ice sheet to raise global sea levels by 20 feet (6 meters), according to the NSIDC. It's Earth's second-largest deposit of land-based ice after Antarctica. And research shows that in recent years its ice has melted faster than ever before. This month, as temperatures in northwestern Greenland approach all-time highs, researchers are encountering unusual, surprising levels of melting ice in the region, according to the AFP.

"There was a dry winter and then recently [there has been] warm air, clear skies and sun — all preconditions for an early melting," Ruth Mottram, a climatologist at the Danish Meteorological Institute (DMI), told the AFP. [How Do Greenhouse Gases Work?]

Mottram and colleagues found that Greenland lost 4.1 billion tons (3.7 billion metric tons) of ice on June 17 alone, and that 41 billion tons (37 billion metric tons) of ice have melted on the island since the start of the month.

The most significant concern here, according to the AFP, is how early this is all happening. Greenland experiences annual ice melt and growth cycles (though usually, unlike in recent years, they've more or less balanced each other out); but in 2019, the melting season began in early May. That's a month earlier than is typical and something that's happened only once before in the historical record, in 2016.

That means that not only is the ice melting very fast, it has more time to melt this summer than it would in a climate system that wasn’t so unbalanced. Since 1972, Greenland has contributed about half an inch (1.4 centimeters) to sea-level rise. But as humanity now pumps far more greenhouse gases into the air than at any time in the 20th century, that process is speeding up. Long melt seasons like this one seem to lead to much greater contributions to sea-level rise than in previous decades.

"It's possible that we could break the records set in 2012 for both lowest Arctic sea-ice extent ... and for record high Greenland ice-sheet melt," Mottram said, as reported by the AFP.

In addition to the global consequences of the ice melt, locals in Greenland are encountering a terrain completely transformed from its usual state. A viral photo showed a group of sled dog teams that were forced to turn back after encountering a usually solid stretch of ice that had liquified on the surface.

• The Coldest Places on Earth
• The 8 Hottest Places on Earth
• 10 Tsunamis That Changed History

Originally published on Live Science.

On Wednesday evening (May 1), a man plummeted into Hawaii's Kīlauea caldera — and survived.

The man had climbed over a railing at the Steaming Bluff overlook to get closer to the edge of the cliff, which dropped down 300 feet (91 meters) into the caldera. At about 6:30 p.m. local time, he lost his footing and fell, according to a statement from the National Park Service.

A search team found the man a couple of hours later "alive, but seriously injured," according to the statement. He had fallen onto a narrow ledge about 70 feet (21 m) down from the cliff's edge. Using ropes, a stretcher and a helicopter, the rescue team airlifted the man to Hilo Medical Center. [Photos: Fiery Lava from Kilauea Volcano Erupts on Hawaii's Big Island]

Army officials said he was a Schofield Barracks soldier who was on a training mission in Pohakuloa, Hawaii. The 32-year-old man was in stable condition on Thursday, according to Hawaii News Now. 

Kīlauea, though not currently erupting, is one of the most active volcanoes on the planet — just last year, a large eruption destroyed 700 homes and forced thousands of people to evacuate. 

"Visitors should never cross safety barriers, especially around dangerous and destabilized cliff edges," John Broward, the chief ranger at Hawaii Volcanoes National Park, said in the statement. "Crossing safety barriers and entering closed areas can result in serious injuries and death."

• The 11 Biggest Volcanic Eruptions in History
• Big Blasts: History's 10 Most Destructive Volcanoes
• 10 Most Hazardous Countries For Volcanoes (Photos)

Originally published on Live Science.

DEET works because mosquitoes can taste your body with their legs, and it makes them think your skin tastes super gross, according to a new study.

The chemical has long been known to be the most effective mosquito repellent available, but researchers weren't sure why or how it worked. The new study, available online in advance of publication May 6 in the journal Cell Current Biology, showed that DEET doesn't taste especially gross to mosquitoes' mouths. Rather, they really don't like the way it feels to the tongue-like cells on their feet.

"We were confident then that DEET was doing something interesting and fairly unique on the surface of the skin," lead study author Emily Dennis, a neurogeneticist at Princeton University, said in a statement. (Dennis was a graduate student at Rockefeller University when she did the DEET research.)

That's because, while DEET tastes bitter to mosquitoes that drink it, it doesn't taste any more bitter than other bitter chemicals. And Dennis had previously worked on a team that showed that DEET doesn't keep mosquitoes from landing on people. Only once the mosquitoes land, the researchers showed, does the effect of the repellent kick in and drive the mosquitoes away. [Googly Eyes: Photos of Striking Wasp Faces]

This new work had six stages:

First, the researchers offered mosquitoes one of three foods: sugar water, sugar water mixed with DEET or sugar water mixed with another bitter chemical. The insects preferred the plain sugar water to either chemical mixture, but didn't distinguish between DEET and the bitter substance.

Second, they slathered the skin of their arms in the bitter chemical at very high concentrations. The mosquitoes, they found, were still happy to land on the skin, puncture through it, and drink the clean blood beneath.

Third, they offered the mosquitoes a serving of warm blood protected by a skin-like membrane. When the DEET or other bitter substances were mixed into that blood, they found, the mosquitoes didn't drink it.

Fourth, they tested those compounds on the surface of the membrane with clean blood beneath. Bitters on the membrane weren't effective at stopping the insects from drinking. But with a layer of DEET on the membrane, the mosquitoes still landed on it but immediately took off.

Fifth, they offered the mosquitoes blood beneath a patch of DEET-coated skin that was too small for them to simultaneously drink from and touch with their legs. The mosquitoes still drank, suggesting that they weren't just reacting to the way DEET felt to their mouthparts.

Sixth, and finally, they used a special glue to partially block the taste buds on the mosquitoes' legs. The insects still drank blood beneath DEET-coated skin, albeit less often, suggesting that the legs in particular were experiencing the repelling sensation when DEET worked.

So when you're outside, coated in DEET, know this: You still smell good enough to mosquitoes. They still want to drink your warm blood. But your skin tastes super gross to their legs.

• Gallery: Out-of-This-World Images of Insects
• Goliath Birdeater: Images of a Colossal Spider
• The Cutest Bugs in The World

Originally published on Live Science.

Winter is not coming to the northern hemisphere — and we have our planet's tilt to thank.

Earth's axis is slightly tilted as it rotates around the sun. This means that the sun's rays don't hit our planet equally: If the rays directly hit the northern hemisphere, it spells winter for the southern hemisphere, and vice versa. Because the Earth is titled, as it orbits the sun, certain latitudes of the planet receive more or less sunlight during each season. [5 Real-Life Inspirations for 'Game of Thrones' Characters]

But what if the seasons — and specifically, winter — lasted for years on our planet like they do on "Game of Thrones"?

It depends on how it happened, said Christopher Walcek, a senior research associate at the University of Alabany's Atmospheric Sciences Research Center. In other words, to answer the question, you'd need to know what caused winter to last for years.

It could happen (though it wouldn't) if our planet fell into an orbit farther from the sun (nope) or stopped orbiting entirely in mid-February (this might happen… just kidding).

Let's say the latter happened, and the northern hemisphere wound up permanently tilted away from the sun.

In that case, in the northern hemisphere, the days would be short, the nights would long — and you'd have a high frequency of snow storms. Because the warmer weather wouldn't roll around to melt the snow, it would begin to accumulate, Walcek told Live Science.

After just a couple of years, lingering winter weather would cause major ecosystem changes, he said.

Deciduous trees and plants that normally sprout in the spring wouldn't do so; this would have ramifications for the rest of the food chain. "Bears and squirrels wouldn't be able to eat and would starve, deer would similarly be culled," Walcek said.

As animals adjusted to reduced sunlight and availability of energy, "populations of [every species] would be reduced to a much lower level," he said.

For example, many animals spend the months of winter preserving their energy through various means as food becomes scarce.

Take frogs and turtles. They survive the winter season by lowering their metabolic rate so that they don't need to eat. These animals pretty much become "behaviorally inactive" during this time, said Jon Costanzo, an adjunct professor of biology at Miami University. But "there are limits to how long they can survive without feeding," he said.

If winter went on and on, frogs and turtles would deplete their energy reserves and, being unable to feed, die of starvation. Or, metabolic waste products that accumulate in the body during the winter would build up, reaching toxic levels.

"Frogs and turtles that live in seasonally cold places are very well-adapted to survive the winter, even a particularly long one," Costanzo told Live Science. "However, it is doubtful that they could survive a hibernation that lasts multiple years."

Winter in Westeros is long, but it does usually end after a couple of years. But what if our world just got stuck on winter, and the cold lasted for millennia?

That would look like an ice age, Walcek said. But even ice ages have seasons, so let's imagine a seasonless ice age.

Within hundreds of thousands of years, huge ice sheets and glaciers would form over massive parts of land, and would plow over villages and valleys, the researcher said. "If you stop [the Earth's rotation] in the middle of February, here in the northern hemisphere, probably within about a thousand years you'd see huge ice sheets form over Europe and over Canada."

Places like New York City would likely be on the edge of an ice sheet. There would be "huge changes to the whole food chain of every animal and plant," Walcek said. People would take more to hunting, leaving behind hopes of growing plants under packs of snow, he said.

But physics won't allow this to happen so... happy spring!

Editor's note: This article was corrected on April 14 to clarify that the Earth's tilt does not change as it rotates the sun.

• Photos: 33 Stunning Locations Where 'Game of Thrones' Was Filmed
• Move Over, 'Game of Thrones,' Here Are 9 Real-Life 'Dragons'
• Winter: The Coldest Season

Originally published on Live Science.

SPF facial moisturizers can block the sun's dangerous ultraviolet rays as effectively as comparable sunscreens, but only if you use them correctly. And according to a new paper published today (April 3) in the journal PLOS One, you probably don't.

Sun-blocking moisturizers are popular beauty products, often marketed as "anti-aging" products. (Protecting skin from UV rays with any sunscreen will keep it looking younger as well as help protect it from cancer, as Live Science has previously reported.) But the researchers behind the new paper found that people are significantly less careful about achieving full coverage using moisturizers than they are with sunscreen, exposing vulnerable patches of skin to UV rays.

The new findings are based on an experiment conducted on 84 college students at the University of Liverpool in the United Kingdom. [5 Things You Didn't Know About Sunscreen]

Researchers gave each student either sunscreen or SPF moisturizer, with the instructions to simply apply the product to their face. After applying, the students filled out a questionnaire in which they were asked whether they had applied the substance to "all areas" of their faces. On a later date, the researchers repeated the experiment, giving the sunscreen students moisturizer and the moisturizer students sunscreen.

In both cases, an overwhelming majority of the subjects believed that they had successfully covered their entire faces.

But photos told a different story. Using a UV camera under UV lamps, the researchers imaged the students' faces. These photos showed where exactly the sunscreen or moisturized was applied. When using sunscreen, the students missed an average of 11.1 percent of their faces, the researchers found. But using moisturizer, the students missed an average 16.6 percent of their faces.

The main problem? Folks were skipping their eyelids.The students were prone to pass over that sensitive skin area when using either product, but they skipped it most often when using moisturizer.

Interestingly, darker-skinned students tended to do dramatically better than lighter-skinned students at covering their eyelids in both cases. And men did significantly better than women.

No group was exactly good at covering their eyelids, though, and subjects tended to miss other parts of their faces as well.

Based on these results, the researchers suggested, it's probably a better idea to use sunscreens than SPF moisturizers.

But in either case, it's definitely a good idea to make sure you cover your whole face, including your eyelids.

• The 7 Biggest Mysteries of the Human Body
• Strange Designs: 5 Weird Ways Tattoos Affect Your Health
• 7 Beauty Trends That Are Bad for Your Health

Originally published on Live Science.

An annual celestial alignment between Earth and the sun known as the spring equinox, occurs today (March 20) at 5:58 p.m. ET, announcing that the seasons are shifting and spring is on the way.

And this year, the equinox brings another celestial marvel — a spectacular supermoon. This phenomenon — when the full moon appears larger than usual — takes place during the moon's closest approach to Earth; tonight's supermoon will be the first in 19 years to coincide with a spring equinox. [6 Signs Spring Has Sprung]

The Virtual Telescope Project will livestream the supermoon as it rises over the skyline of Rome, Italy, at 5:45 p.m. local time (12:45 p.m. ET).

Twice in a year, the Earth reaches a point during its annual journey around the sun when the Northern and Southern hemispheres — the two planetary zones bisected by the equator — receive the same amount of daylight, a phenomenon called an equinox, or "equal night" in Latin. 

In the Northern Hemisphere, what is known as the spring equinox also marks the beginning of fall in the Southern Hemisphere. The Northern Hemisphere's autumnal equinox — which will take place six months later, on Sept. 23 — heralds the coming of spring south of the equator.

Because Earth orbits the sun while tilted on its axis at about 23.5 degrees, daylight is almost always distributed unequally across the planet. Depending on Earth's orbital position, either the Northern Hemisphere or the Southern is illuminated longer during a 24-hour cycle, C. Alex Young, associate director for science in the Heliophysics Science Division at NASA's Goddard Space Flight Center, told Live Science. 

"During two special times twice a year, the tilt is actually perpendicular to the sun, which means that Earth is equally illuminated in the Northern and Southern hemispheres," Young said.

Ancient observations

It's uncertain when ancient civilizations first became aware of this phenomenon, though humans have been creating structures to observe the changing positions of the sun in the sky and its relationship to the seasons for thousands of years, Young said. Today, spacecraft offer views of Earth that easily capture the distribution of light across the planet's surface at any given time of the year. And when an equinox occurs, "you can see this effect quite well," Young said.

"Earth's tilt has an effect during other times of the year — you see more light in the Northern Hemisphere or more light in the Southern Hemisphere, depending on the time of year. And then during the equinoxes you see that the Northern and Southern hemispheres are equally lit up," he said.  

These long-range views of Earth offer an important "big picture" understanding of our planet that can only be obtained by looking at it from a distance, Young told Live Science.

"Once we were able to put satellites into space we were able to see the extent of cloud cover, landmasses, bodies of water. It's given us a new perspective on this very complicated and very vital system," he said.  

• Earth from Above: 101 Stunning Images from Orbit
• Way to Be Weird, Earth: 10 Strange Findings About Our Planet
• Vernal Equinox: First Day of Spring Seen from Space (Photo)

Originally published on Live Science.

Historic floods across the Midwest have left three dead, prompted mass evacuations, and drowned cities.

The floods aren’t isolated incidents, however: Two giant waves of water are rolling down from the country's far-northern middle expanse. One wave is following the path of the Missouri River toward the Mississippi River, carrying with it big chunks of ice. The second wave is taking a similar path down the Mississippi River from Minnesota. Both are the result of a long winter of heavy snowfall in Minnesota and the Dakotas followed by a short, sharp melt.

Both floods are more or less each one giant wave traveling at the speeds of their rivers, said Darone Jones, director of the Water Prediction Operations Division (WPOD) at the National Weather Service’s National Water Center (NWC) in Alabama.

The North Dakota wave traveled down the Missouri River to Nebraska and yesterday (March 18) reached northwestern Missouri. After passing Kansas City it will turn left, following the river, and make its way toward the joining of the Missouri and Mississippi rivers in St. Louis. [Top 10 Ways to Destroy Earth]

The Minnesota wave is taking the more straightforward route down the Mississippi River through Iowa, past St. Louis and into the ocean. Along the way, both waves should lose some water, so the downstream floods may not be as intense as those upstream.

It takes about 28 days for a drop of water originating in North Dakota to make its way down the Missouri River to the ocean, Jones told Live Science. This series of floods is the result of excess water swelling the northern stretches of the Missouri River following a sudden melting event last week.

Snowpack, melting

The WPOD has known that there was a lot of potential meltwater in the northern Midwest in the form of snowpack, Jones said. The whole region had a very rough winter.

(Figuring out how much potential meltwater there is isn't just a matter of seeing how high the snow is piled, but weighing it, Jones added. Light, fluffy snow doesn't produce as much water when it melts as heavier, more tightly packed snow.)

Indeed, the NWC has a spring flooding forecast due for release at the end of this week that will warn (perhaps too late) that this winter dumped a lot of heavy snow in the northern Plains and Midwest, creating significant flooding risks. But the extent of flooding is a factor of how fast the snow melts, not just how much snow is up there, Jones said.

Thanks to a strong storm system last week, the snow is melting very fast. That storm dumped heavy snow on Colorado and then turned into rain over North Dakota and Minnesota, Jones said. That rain was very cold, but still warm enough to trigger a sudden snowmelt. Ultimately, a couple inches of rainwater across a wide area combined with several inches of snowmelt to produce this intense flood wave.

And the chunks of ice in the flood make things worse, Jones said. Periodically, they clump up as the flood moves south, creating temporary ice dams. Those dams cause water to back up behind them, worsening the flooding before they break and release the wave again.

Forecasters aren't sure yet just how bad this flood season will be, Jones added. That depends a lot on whether there are many more sudden melting events like the one that caused this wave, he said, or whether the region has a chance to warm slowly.

• 12 Strangest Sites on Google Earth
• Mightiest Floods of the Mississippi River
• Gallery: Most Famous Waterfalls in the US

Originally published on Live Science.

An instrument called Atmospheric Infrared Sounder, or AIRS, on the Aqua satellite has been measuring the temperature of air masses across the United States. Aqua itself launched in 2002 and carries a half dozen different instruments designed to study parts of the water cycle, including evaporation, cloud formation and precipitation.

The AIRS instrument focuses on temperature measurements, making it a helpful tool for looking at this week's frigid weather and its cause, the so-called polar vortex phenomenon in which cold Arctic air sneaks farther south than usual.

The new NASA visualization of the instrument's data shows measurements gathered between Jan. 20 and Jan. 29. Temperatures as low as minus 40 degrees Fahrenheit (minus 40 degrees Celsius) are on display in purple, and can be seen stretching as far south as South Dakota, Iowa and northern Illinois. Everything in pale blue and "colder" colors represents temperatures below the freezing point of water, 32 degrees Fahrenheit (0 degrees Celsius).

If you live in the regions currently subject to this frigid air, be sure to bundle up and keep an eye on local weather forecasts until the cold retreats.

Email Meghan Bartels at mbartels@space.com or follow her @meghanbartels. Follow us @Spacedotcom and Facebook. Original article on Space.com .

It might be cold enough in Chicago right now to make the ground shake.

Local news station WGN reported today (Jan. 30) that its viewers had heard "frost quakes" in the city overnight. And though the reports in Chicago are still unconfirmed, frost quakes are indeed a real thing.

Frost quakes, or "cryoseisms," occur when water trapped underground freezes suddenly as the temperature drops, causing it to expand. (Water expands as it freezes.) All that rapidly expanding water underground can split rocks and put stress on the soil, causing loud booms. Frost quakes are fairly rare events and difficult to positively identify. A huge blast that shook northwest Calgary, Canada, in 2014 was widely attributed to a loud cryoseism, but researchers never confirmed that as the cause. [9 Tips for Exercising in Winter Weather]

Charles Mott, a meteorologist at the National Weather Service (NWS) office serving Chicago, told Live Science he hasn't personally heard any frost quakes in recent days, but added "that has to do with being inside all day."

But Mott said that there's been some chatter about the possibility of them around the office, and that he has no reason to doubt WGN's report.

For a frost quake to occur, at least three conditions are required, according to "Frost Quakes: Forecasting the Unanticipated Clatter," published online in 2015 in the meteorology journal Weatherwise. First, rain or snowmelt saturates the ground with water. Second, there's little to no snow on the ground, which otherwise blankets the soil and protects it from sudden temperature changes. Third, the temperature rapidly drops, freezing the earth.

There's some evidence that frost quakes have become more common recently, at least in the Toronto area. The authors of "Forecasting the Unanticipated Clatter" published a different paper online in June 2016 suggesting that this increase might be the result of the changing climate. Warmer, wetter air masses have become more common in the area over the winter, leaving the ground wet and free of snow. When those air masses do turn frigid, frost quakes can result.

It's unclear if frost quakes are occurring elsewhere in areas impacted by the current polar vortex event. But meteorologists in the Grand Forks, North Dakota, NWS office laughed when contacted by Live Science with the question and said they'd never heard the term "frost quake" before.

("Cryoseisms" rang a bell, one forecaster said, but he was unsure of the details and would "have to google it, just like you.")

Brent Hewett, a meteorologist at the NWS office in the Twin Cities region of Minnesota, said that there had been no reports of cryoseisms in that area, probably because there's snow on the ground.

• The 9 Biggest Unsolved Mysteries in Physics
• The Large Numbers That Define the Universe
• Twisted Physics: 7 Mind-Blowing Findings

Originally published on Live Science.

On Sunday, as much of the country plunged into polar temperatures, President Donald Trump took the opportunity to make a dig at climate science on Twitter.

"Be careful and try staying in your house," he tweeted. "Large parts of the Country are suffering from tremendous amounts of snow and near record setting cold. Amazing how big this system is. Wouldn't be bad to have a little of that good old fashioned Global Warming right now!"

Perhaps unsurprisingly for a president who has flirted with the idea that climate change is a hoax, Trump doesn't have global warming's effects quite right. Indeed, even as the globe gets hotter on average, some localities could see bigger winter storms. [The Reality of Climate Change: 10 Myths Busted]

Climate versus weather

The first problem is mixing up climate and weather. This is a perennial issue in his rhetoric; in 2016, he pointed to an unusually warm day in 1898 as evidence that the globe isn't overall getting hotter. That weather record was set in only two spots, Oregon and Maryland, making it pretty meaningless to the question of climate, which deals in long-term trends the globe over.

And the long-term trend isn't pretty. According to the U.S. National Climatic Data Center, there has not been a single month in which the average surface temperature on Earth has dipped below the 1901 to 2000 average since … 1985. (The National Oceanic and Atmospheric Administration's repository of this data is offline due to the government shutdown, but The Conversation has more detail on the numbers.)

A warming globe doesn't mean that winter will cease to exist, though scientists are already noting trends toward fairly mild winter temperatures. The Climate Science Special Report (CSSR), spearheaded by federal scientists, found that between 1986 and 2016 alone, average annual temperatures over the contiguous United States increased by 1.2 degrees Fahrenheit (0.7 degrees Celsius). Meanwhile, cold waves have become less prevalent, while heat waves have become more common. And high-temperature records are far outstripping record lows.

The future of cold

So what about winter storms? They certainly still exist, but climate scientists predict that Americans will experience even fewer cold waves in the future, with "cold waves" defined as six-day periods in which the temperatures are below the 10th percentile of the temperature range for that area. Alaska will see the greatest decline in cold waves, according to the CSSR, while the Northeast will see the least extreme decline.

Snow cover, snow depth and extreme snowfall are also on the decline across the southern and western United States, according to the CSSR. The Northeast is something of an anomaly: Extreme snowfall has increased in parts of the northern United States. Interestingly, the warming climate can sometimes actually trigger extreme snowfall events, because warmer air can carry more moisture. Meanders in the jet stream that channel frigid air down from the Arctic can then create the conditions for monster blizzards. Unfortunately, as climate change alters the polar regions, these jet stream changes may become more common. The result could be a sort of "feast or famine" situation for winter storms: As overall snowfall declines (and parches the already-arid West), some areas — particularly the Northeast — could see more individual extreme precipitation events.

It's worth noting that all of the trends caused by climate change are also overlaid on top of shorter-scale atmospheric patterns. For example, the famous ocean atmosphere pattern El Niño, which involves a warmer-than-usual central or eastern Pacific, alters winter weather across the United States. Typically, it brings wet, chilly weather to the southern half of the country and warmer, drier weather to much of the northern half. As of Jan. 10, the U.S. Climate Prediction Center forecasted that El Niño has a 65 percent chance of forming by the early spring.

• In Photos: Frozen Lakes in Winter
• 8 Ways Global Warming Is Already Changing the World
• Earth from Above: 101 Stunning Images from Orbit

Originally published on Live Science.

A major snowstorm has begun its trek across the United States, according to The Weather Channel, with significant snowfall already underway in the Dakotas, Minnesota and Iowa. Over the course of the weekend, it's expected to impact much of the Midwest and Northeast, and send rain into the Southeast.

The National Weather Service (NWS), where forecasters are working without pay due to the government shutdown, attributed the large storm to two factors. First, a low-pressure system, the sort of air mass typically responsible for storm activity, has moved over the continent from the Pacific Ocean. After crossing the Rockies (where it already caused some snowfall) it was "re-energized" over the Plains Friday (Jan. 18). At the same time, a "strong surge" of Arctic air (likely from the weakening of the polar vortex) has moved down through Canada and merged with the system, creating a very wide air mass with the capacity to produce lots of snow. [The Snowiest Places on Earth]

"Six to 10 inches of snow ^[are] forecast for parts of the Midwest, but the highest snow totals are expected for [upstate New York and New England], where 1 to 2 feet of snow ^[are] forecast," the NWS said.

Some of the most significant problems associated with the storm may fall along the transition zone between snow and rain, where the cold Arctic mass meets the warmer air to the south. In those areas, particularly the Ohio Valley and the mid-Atlantic, strong winds, sleet and freezing rain are all likely, according to the NWS.

New York City is expected to see snow, but details are still uncertain.

After the storm passes, a long period of deep cold is expected, which could pose problems, especially for anyone who loses power during the storm. And there's a real threat of widespread power losses according to The Weather Channel, thanks to the combination of heavy ice accumulation and strong winds.

• Animal Gallery: Fun in the Snow
• Hurricanes from Above: See Nature's Biggest Storms
• Best National Parks to Visit During Winter

Originally published on Live Science.

The blast of Arctic weather headed for the United States this weekend could be a first sign of still worse things to come this winter, with signs that a circular low-pressure system of swirling winds that normally keeps frigid air locked up at the North Pole has been disrupted and split into smaller parts.

The disruption in this counterclockwise-spinning beast, called the polar vortex, is thought to be caused in part by a warm summer over the Arctic and a relatively cold fall over Siberia. The result for the United States and northern Europe? A severe winter lasting throughout February and possibly into March.

Meteorologist Judah Cohen agreed that the breaking up of the polar vortex could be the culprit for the coming storm. Cohen, the director of seasonal forecasting for the weather risk management company Atmospheric and Environmental Research (AER), based in Lexington, Massachusetts, told Live Science that the coming snowstorms in the United States this weekend are consistent with weather models that predicted severe wintry weather to come in the coming weeks. [Infographic: Earth's Atmosphere Top to Bottom]

The weather models suggested that the disruptions would follow the pattern of polar vortex disruptions seen during the northern winter last year, which resulted in freezing weather across the United States in December and January, and a severe cold snap in March over the United Kingdom.

"This pattern looks much more active, [with] more winter type storms and Arctic outbreaks — I think I would attribute it to definitely being a polar vortex disruption, because it is very consistent with what we've seen in the past," Cohen said.

Polar winds

The northern polar vortex is a fast-flowing stream of air that circles the North Pole in the upper parts of the atmosphere, known as the stratosphere, about 20 miles (32 kilometers) above the surface.

A similar polar vortex exists over the South Pole, but it is the northern polar vortex that can bring severe winter weather to the United States and Europe.

When the northern polar vortex is strong, Cohen explained, it keeps most of the air cooled by the Arctic in the polar region, resulting in mild winter temperatures in the middle latitudes of the eastern United States, and in northern Europe and Asia.

But when the polar vortex weakens, the once-trapped cold air can meander throughout the top of the Northern Hemisphere, bringing polar temperatures and extreme winter weather to lower latitudes, he said.

"Think of the polar vortex as a spinning top, and where the polar vortex goes so goes the cold air," Cohen said. "A strong polar vortex is a fast, tightly spinning top centered over the North Pole, keeping all the cold air with it close by over the Arctic. [But] a weak or perturbed polar vortex is a spinning top that has been banged or bumped into an object multiple times … the top slows down and wobbles and can meander from its location."

As for what knocked into this spinning top, Cohen points, in part, to summer warming in the Arctic region and a relatively cold fall in Siberia.

"I have argued that Arctic change has certainly been a contributor," he said. "The loss of sea ice, especially in the Barents and Kara seas, which are near Scandinavia in north-west Russia … and also an increasing trend in Siberian snow cover in October, I think that has also been contributing.

Winter weather

In recent days, weather scientists have seen the northern polar vortex split into three smaller parts, which have now changed into two giant patches of polar winds in the stratosphere — one over northern Canada and one over central Russia.

Snowstorms have been forecast today (Jan. 18) and tomorrow (Jan. 19) for the central Plains and Midwest of the United States, as part of what's being called winter storm Harper; and the winter weather is expected to hit the mid-Atlantic and Northeast of the United States later in the weekend.

Cohen said these patterns followed the weather patterns seen last winter, which was exceptionally cold in the United States over the New Year and the first weeks of 2018.

But he warned that a cold snap isn't a foregone conclusion; the winter weather could still turn out to be relatively mild if the polar vortex returns to its normal configuration in the coming weeks.

"Right now, the weather looks like it is very consistent with our expectations of how the weather would transition following these type of events, but we'll see," he said. "These [weather patterns] tend to be episodic, so it doesn't come all down once … not every day will be below normal, and we will not have snow every day."

Cohen added, "[But] I think at least through the end of February, and I would think probably into early March, there will be kind of a skewing of the probabilities or the frequency of severe winter weather."

• On Ice: Stunning Images of Canadian Arctic
• The 10 Worst Blizzards in US History
• Image Gallery: Life at the North Pole

Original article on Live Science.

As it gets colder and we start bundling up in jackets and earmuffs, most of us tend to stop thinking about our sun exposure. After all, how much damage can the weak winter sun cause if you're already covered up from head to toe?

But the sun's rays can be just as harmful when it's cold and cloudy outside. "Any exposed area of your body can still get sunburned," Dr. Apple Bodemer, an associate professor of dermatology at the University of Wisconsin-Madison, told Live Science.

Whether you spend a day on the slopes, skating on a pond or shoveling snow out of your driveway, your face is still getting exposed to the sun's radiation in the form of ultraviolet (UV) light, according to Bodemer. When those UV rays penetrate deep into your skin cells, they can cause DNA damage, she said. [Do Animals Ever Get Sunburned?]

The sun's long ultraviolet A (UVA) waves can cause premature aging, sunspots and wrinkles, while its short ultraviolet B (UVB) rays are notorious for causing skin reddening and burns. (Ultraviolet C, or UVC rays are a third and even shorter type of ultraviolet radiation that is mostly absorbed by the Earth's ozone layer).

Skin damage caused by UV exposure increases over time. "Your skin is like the meter in a taxi cab," said Dr. Darrell Rigel, a clinical professor of dermatology at New York University. "As you get more radiation, the meter goes forward, and the more that happens, or the stronger the radiation, the faster the meter goes."

Eventually, UV-related skin damage can lead to skin cancer. It's the most common type of cancer in the United States. About 3.3 million Americans are diagnosed with basal and squamous cell skin cancers each year, according to the American Cancer Society.

Snow and ice can also make sun damage worse. They reflect up to 80 percent of UV rays that reach the ground, according to the Skin Cancer Foundation. That means that you get hit from two angles: first from the sky and second from the ground, as the rays rebound. And skiers and snowboarders increase their risk of getting sunburned even more because UV exposure increases at higher altitudes.

"Our atmosphere helps scatter some of the UV radiation," Bodemer said. "When you're up at a high altitude, there's not as much atmosphere and you will get more intense UV radiation exposure."

The overall amount of UV rays decreases slightly in the winter because of the angle that the sun's rays hit the Earth, Bodemer said. But people who are exposed to the winter sun — especially those who are prone to burning in the summer — are still at risk of getting a sunburn, she said.

Certain creams and medications, such as retinol products and chemical peels, can also make the skin more photosensitive. Rigel told Live Science. And even tetracycline-based antibiotics, including those prescribed for treating acne or a cold, can increase your sun-sensitivity.

"In general, the biggest factor for sun-sensitivity is how pale your skin is," he said. "But, the reality is that even the darkest [skinned] individual can get sun damage. They might not get it as quickly because they have more natural protection, but even dark-skinned individuals get skin cancer."

Luckily, the solution for protecting your skin is simple: Wear sunscreen every day. Rigel recommended using sunscreen with a sun protection factor (SPF) of at least 30, and going higher if you're planning a vacation at high altitudes. As a rule of thumb, SPF 30 will block 97 percent of UVB rays; SPF 50 will block 98 percent of UVB rays; And SPF 100 will block 99 percent of UVB rays, Dr. Steven Wang, the director of Dermatologic Surgery and Dermatology at Memorial Sloan Kettering Cancer Center in Basking Ridge, New Jersey, told the Skin Cancer Foundation. And, no matter what kind of sunscreen you use, it's important to apply SPF about once every 2 hours, Wang added.

Rigel also suggested looking for sunscreens labeled "broad spectrum" — to protect against both UVB and UVA rays — as well as sunscreens that are water resistant for up to 80 minutes. That way, you can go about your day without it wearing off too quickly.

You don't have to hibernate indoors as long as you protect yourself when you go out, Rigel said. "It always pays to protect yourself."

• Why Does the Body Tan?
• How Does Sunscreen Work?
• Do Humans Have Hair on the Undersides of Their Arms?

Original article on Live Science.

You need your lips to talk, take duck-face selfies and kiss your loved ones. That's why dry, chapped lips can not only be itchy and painful, they can sometimes be downright embarrassing. But repeatedly applying lip balms and products may not help your case.

Lip balms provide only temporary comfort, and some types can make scaly lips even drier.

That's because, in part, when the thin film of moisture from the lip balm evaporates, it dehydrates your lips even more. "It starts a vicious cycle," Dr. Leah Jacob, an assistant professor of dermatology at Tulane University, told Live Science. [Why Are Lips Red?]

Many of us have to deal with scaly lips, especially in the cold and dry winter, so doctors and beauty pros recommend we treat our lips, as well as the rest of our skin. "Any part of our body that is not covered in the wintertime is going to be subjected to the elements," said Dr. Crystal Aguh, an assistant professor of dermatology at Johns Hopkins University. "People tend to get very dry hands in the winter because we're wearing long-sleeved shirts and jackets, but we're not necessarily covering our hands."

Likewise, people rarely cover their faces and lips during the wintertime, and so those tend to dry out, too, Aguh told Live Science.

Although lips look very different from the rest of our skin, they’re actually quite similar, Aguh said. Just like the rest of our skin, the lips are made up of three layers of cells: the outermost layer of mostly dead cells, known as the stratum corneum, the epidermis and the dermis, which sits below it.The main difference is that these layers — especially the stratum corneum, which forms a protective barrier over the others — is much thinner in the lips and, therefore, more vulnerable to damage.

Additionally, lips don't have any hair follicles or oil glands of their own. Instead, the oil from glands around our lips provide moisture. Licking your lips or applying a thin gloss, balm or anything out of a tube to supplement that moisture may sound like a good idea, but it can be the worst thing you do for them because it can lead to further dehydration, Jacob said.

Some lip balms contain ingredients that can be irritating or drying. Menthol, salicylic acid, cinnamic aldehyde and peppermint flavors are all culprits, Jacob said. "A lot of people don't have any problems with these ingredients, but people with sensitive skin or allergies may be more sensitive to these on their lips, as well," she said.

Shiny glosses and oils are also thought to intensify damage from the sun's ultraviolet (UV) rays, focusing the rays the way a magnifying glass may channel a beam of light onto your lips. But because lips have less melanin — the pigment that gives skin its color — the skin cells in your lips are more likely to sustain sun damage if you use shiny lip products, Jacob said.

Jacob recommends using a thick, emollient lip balm or ointment with SPF in it to truly protect your lips. Glycerin or plain old petroleum jelly are good ingredients to look for, she noted. You can also try using a humidifier at home, which will replenish moisture in the air and, eventually, in your lips. And drink more water to stay hydrated from the inside out.

• How Much Does Your Skin Weigh?
• Is House Dust Mostly Dead Skin?
• What Is Cellulitis?

Original article on Live Science.

Fall Mysteries Solved

'Tis the season of colorful leaves, mulled cider and — dare we say it? — pumpkin spice. Fall spans from the autumn equinox, when the sun is directly over the equator and the length of day and night are equal, to the winter solstice, when the sun is at its most northerly and the Northern Hemisphere's day is at its shortest.

There's more to fall than cable-knit sweaters and harvest feasts, though. Plenty of curious questions come with the season. Read on for the most intriguing "Life's Little Mysteries" that we've gathered over years of watching the season come and go.

Why does fall have two names?

Summer is summer, spring is spring, but fall is … autumn? It's likely that the reason the harvest season has two names is that fall was the last season to really get a name in English. Before the late 14th century, fall was known as "harvest" in English. Then, the Latin "autumn" appeared. It wasn't until the 17th century that people began using "fall." Coincidentally, this wasn't long before the colonization of North America by English speakers. "Autumn" remained the primary term in Britain, while Americans tended to adopt "fall."

Why is your nose running so much?

Fall ushers in the start of flu season, but that's not the only reason the season might be hard on the airways. According to the National Institutes of Health, autumn can be a prime time for seasonal allergies. Pollen counts may fall, but mold counts in the air rise as rotting leaves and dying vegetation decompose. Dry indoor air can exacerbate sniffly symptoms by irritating the lining of the nose, according to Dr. Jay M. Portnoy, chief of allergy, asthma and immunology at Children's Mercy in Kansas City, Missouri.

Why do the leaves change color?

For a few brief weeks in fall, the world is a riot of color (at least if you live where deciduous trees are common). Leaves change color in the fall because, in response to shortening daylight hours, trees stop producing chlorophyll. Without the overwhelming green of chlorophyll to drown them out, other pigments become visible. Carotenoids make yellows and oranges, while reds are due to pigments called anthocyanins. These may help shield the tree's cells from harmful UV rays or otherwise help protect trees from the stress of cooler temperatures.

Why do I have to turn my clock back?

Blame the British. Daylight saving time was first adopted by the British Parliament in 1916, after a proposal in 1907 by a builder named William Willet, who got his inspiration, in part, from a satirical pamphlet published by Ben Franklin in 1784. Willet wanted to change the clocks by 20-minute increments over the course of a month in spring and fall. When Parliament finally did decide to adopt the time change, it was as a wartime effort to keep people's activities aligned with maximum daylight to save coal. The U.S. adopted the measure from 1918 to 1919, kicking the time-change decision to the states afterward. This created a patchwork of confusing time zones until the Uniform Time Act of 1966 created more-consistent rules.

Why does the rain smell so good?

Before it gets cold enough for white, fluffy flakes, autumn may bring sweet-smelling rains. Why does fresh rain smell so good?

One reason is "petrichor," a fragrance that arises from water hitting soil-dwelling bacteria and plant oils after a dry spell. Another might be ozone, which can form during lightning storms and which smells a bit like chlorine.

Why is it so gloomy out?

Fall's moody weather may bring dark clouds, heavy with rain. But why are rain clouds so dark, anyway?

The reason is that rain clouds tend to be a lot thicker than the puffy, harmless clouds that are unlikely to spawn showers. The larger the droplets of water in a cloud, the better they are at absorbing sunlight. Tiny, misty droplets in a fluffy, white cloud scatter light from across the spectrum — giving those clouds their white hue. Bigger droplets in heavier clouds also scatter light, but they do it so well that by the time the sunlight reaches the bottom of the cloud, there isn't much left for the eye to catch. As a result, the base of a thick rain cloud looks dark and ominous.

Why does fall look different in Europe?

Fall colors in North America and eastern Asia are often punctuated by fiery bursts of red. But in Europe, yellows dominate and red is rare. Why? It likely has to do with the evolution of deciduous trees over the past 35 million years, scientists say. Mountain chains running north to south dominate North America and eastern Asia. As ice ages and warm periods cycled over the last 35 million years, trees were able to march north and south along valleys and ridges to find the ecological niches that suited them. So were their insect pests. This likely resulted in an evolutionary arms race that led to the evolution of protective red pigments called anthocyanins.

In Europe, mountain chains have a more east-west orientation (think of the Alps). These high peaks kept trees and insects quarantined. If it got too cold for them, they simply died. The pressure to develop anthocyanins simply wasn't as strong, so few species evolved vermillion hues.

What's going on with my Siberian hamster's testicles?

OK, this might not fall under the category of "frequently asked question" for fall or otherwise. Still, the shrinking testes of the male Siberian hamster are one of the odder seasonal cycles that autumn brings. These high-altitude rodents have a very brief mating season in the summer. Their testes swell up to 17 times larger during the longest days of the year compared to the shortest, a seasonal change that is controlled by the hormone kisspeptin. So as the days shorten this fall, spare a thought for the Siberian hamster.

What's the difference between light and dark turkey meat?

White meat or dark? If you've ever wondered why you're asked to ponder this question as grandpa carves the turkey, the answer is a protein called myoglobin.

Myoglobin is to muscle as hemoglobin is to blood. It's a dark-colored protein that binds to oxygen. Myoglobin hangs on to oxygen in frequently used muscle tissue so that those muscles always have a supply of energy. In domestic turkeys, the most commonly used muscles are in the legs — thus, dark-meat thighs and drumsticks.

Is my Thanksgiving travel going to irradiate me?

We make no guarantees about the health effects of yet another 2-hour flight delay, but a cross-country trip to grandma's house is pretty low-risk, radiation-wise.

Flying puts the human body at a much higher altitude than it's used to. Up above the clouds, there is less atmosphere than on the ground, so high-radiation cosmic rays are more common. Luckily, a New York-to-Los Angeles flight exposes a person to only between 2 and 5 millirems of radiation, half of the 10 millirems received in a chest X-ray. The annual "normal" radiation dose from background radiation is about 620 millirems a year, according to the U.S. Nuclear Regulatory Commission, so a cross-country flight doesn't move the needle significantly.

Is this turkey dinner going to knock me out?

You've probably felt pretty sleepy after Thanksgiving dinner. And, if you're like many Americans, you've probably blamed it on that dang turkey. This food contains a relatively high amount of the compound tryptophan, which converts into the sleep hormone melatonin in the body. High concentrations of tryptophan in isolation may indeed make a person sleepy. Tryptophan supplements were common sleep aids in the 1980s, but they were banned in 1991 after being linked to a painful flu-like illness called eosinophilia-myalgia syndrome.

Your drowsiness after Thanksgiving dinner, though, probably comes from the work of eating mountains of carbohydrates, which prompt the release of insulin, and drinking alcohol, which depresses the nervous system.

What happens when you drop a turkey from a plane?

First, the answer: You get in trouble. Second, the real question: Why is this a question? The answer is Yellville, Arkansas.

This town of just over 1,000 residents in north-central Arkansas was long famous for its Turkey Trot festival in which a local pilot dropped live turkeys from a small plane about 500 feet (150 meters) up. Domestic turkeys can't fly, but they can flap, so most (but not all) of the birds were able to slow themselves enough to survive the experience. According to Arkansas' KY3 TV station, the tradition started after World War II as an effort to bolster the local turkey population; for the first few years, turkeys were simply dropped from the courthouse roof.

The plane-dropping practice has been controversial since at least the 1980s, and the People for the Ethical Treatment of Animals (PETA) weighed in against the practice in 2011. The event went back to the courthouse roof for a few years, before some local rebels started with the airplanes again, according to the Encyclopedia of Arkansas. An exasperated Yellville Chamber of Commerce announced in 2018 that it would no longer sponsor the festival. The local Rotary Club took over, giving Yellville one last chance.

"If somebody drops a turkey," the club's committee chair told KY3, "they have killed Turkey Trot. There will not be another one."

The festival took place on Oct. 12 and Oct. 13, 2018. There are no reports that anyone dropped a turkey.

Most of the United States can look forward to a mild winter with above-average temperatures, particularly in Alaska, Hawaii and the northern and western states, experts with the National Oceanic and Atmospheric Administration (NOAA) announced today (Oct. 18).

Officials with NOAA's Climate Prediction Center (CPC) shared their predictions at a news conference, describing the outlook for winter precipitation and temperatures in the U.S. from December 2018 through February 2019.

Below-average temperatures are expected to be scarce in every part of the U.S., but there's likely to be plenty of snow or rain, with wetter-than-average conditions predicted for the southern part of the country and up into the mid-Atlantic states, according to the NOAA winter outlook. [In Photos: Best National Parks to Visit During Winter]

A developing El Niño — part of an ocean-climate cycle that can influence weather — could also leave its mark on the winter weather, as El Niño typically brings wetter conditions to the southern U.S., while shaping warm, dry conditions in the North, Mike Halpert, the CPC's deputy director, explained at the news conference.

Northern Florida and southern Georgia have the highest probability of experiencing a wetter-than-average winter, according to the report.

Though El Niño is still taking shape, there's a very good chance — about 70 to 75 percent — that it will emerge over the next few months and persist through the winter, Halpert said. El Niño is part of a climate cycle known as the El Niño Southern Oscillation (ENSO); during El Niño, warm Pacific Ocean waters shift to the eastern coast of South America. In a strong El Niño year, ocean temperatures are even warmer than average. This phenomenon heats the air above the water and sets up a feedback loop between the sea and the atmosphere, which can dramatically impact weather patterns.

A powerful El Niño can bring unusually warm winter temperatures to the U.S. The winter of 2015 to 2016, which took place during the strongest El Niño in 60 years, was the warmest winter on record for the continental U.S., Halpert said.

However, this year's El Niño is anticipated to be much weaker than that, he added.

As for drought predictions, some relief is expected in Arizona, New Mexico, the southern parts of Colorado and Utah, and the coastal Pacific Northwest.

But drought conditions are expected to persist in the northern Plains states; in Southern California and the interior parts of the Pacific Northwest; and in the central Rockies, the central Plains states and the central Great Basin.

While there is always a certain amount of uncertainty in long-term weather and drought predictions such as these, the track record for the accuracy of the CPC seasonal outlooks is about 40 percent, up from a previous estimate of 30 percent, Halpert said.

"That's the general level for these type of forecasts," he added.

Originally publishedon Live Science.

Whether you catch a cold this winter or make it through the season scot-free may depend in part on how many "stressors" your nose and airway passages encounter, a new study suggests.

The research looked at two defense mechanisms that cells in a person's airway use to protect themselves from threats: one that protects against viruses like the common cold virus and another that protects against "oxidative stress." This form of cell damage is triggered by viruses and other irritants, such as cigarette smoke or pollen.

The study found that there's a trade-off between these two defenses: more protection against oxidative stress damage (for example, damage induced by cigarette smoke) means less protection against invaders like rhinovirus, which is the main cause of colds. [7 Absolutely Horrible Head Infections]

"Your airway lining protects against viruses but also other harmful substances that enter airways," senior study author Dr. Ellen Foxman, an assistant professor of laboratory medicine at Yale School of Medicine in New Haven, Connecticut, said in a statement. "The airway does pretty well if it encounters one stressor at a time. But when there are two different stressors, there's a trade-off," Foxman explained. "What we found is that when your airway is trying to deal with another stress type, it can adapt, but the cost is susceptibility to rhinovirus infection."

The study was published Sept. 11 in the journal Cell Reports.

Defense "trade-off"

Respiratory viruses cause an estimated 500 million colds and 2 million hospitalizations in the United States every year, the researchers said. However, some people can be exposed to a virus without getting sick, because the cells that line their airways clear the virus before it causes symptoms. But for other people, this clearance doesn't happen, and they wind up sick.

To better understand why some people get sick from cold viruses while others escape illness, the researchers examined airway cells from healthy human donors. The cells were obtained from the lining of people's nasal passages or of their lungs.

Researchers found that the nasal cells had a stronger inherent defense response to viruses, while the lung cells had a stronger defense against oxidative stress.

Later experiments revealed that there was indeed a trade-off between these two defense mechanisms. For example, when the researchers exposed nasal cells to cigarette smoke to trigger an oxidative-stress response, the cells became more susceptible to rhinovirus.

"They survive the cigarette smoke but can't fight the virus as well," Foxman said. "And the virus grows better."

The finding might explain why cigarette smokers tend to be more susceptible to rhinovirus infection compared to people who don't smoke, the researchers said.

The results also suggest that finding ways to protect the cells lining the airway from oxidative stress "may lead to effective strategies to enhance natural defense against rhinovirus infection," the researchers concluded. However, more studies will be needed to investigate this idea.

Original article on Live Science.

Scorching summer days can be tough without air conditioning, and you might find yourself searching for ways to stay cool, including using a fan at night. But is it healthy to sleep with a fan on?

Some recent headlines have made sleeping with a fan on sound downright dangerous. "Why Sleeping with Your Fan on Could Be Seriously Damaging Your Health," read one recent headline from the Mirror. "Sleeping with a Bedside Fan Could Pose Health Risks," read another, from LifeZette.

But experts say the reality is not that dire.

"There's nothing about a fan that's toxic," said Dr. Len Horovitz, a pulmonologist at Lenox Hill Hospital in New York City. "There's nothing wrong with circulating air." [7 Common Summer Health Concerns]

Indeed, sleep is very important, and you don't want to be sweating all night, Horovitz told Live Science.

But anything that causes rapid air movement, including a fan, can evaporate moisture from your mouth and nasal passages, drying them out, he said. Fans may also circulate dust, which could bother people, particularly if they have allergies.

If you do sleep with a fan on, Horovitz said it's a good idea to keep it at a safe distance from your bed and not have it blowing right on you. To guard against dust and other allergens, Horovitz recommended keeping an air filter in the bedroom. He also recommended performing daily sinus irrigation with saline, which can help with dry nasal passages, congestion and other nasal problems.

Cold air can also cause muscle contractions, and so exposure to this air at night may lead to a stiff neck in the morning. But Horovitz said this is more of a problem with air conditioning that's left on at night than it is with fans. If you do sleep with air conditioning on at night, Horovitz said the air shouldn't be blowing directly on you and the setting shouldn't be lower than 68 degrees Fahrenheit (20 degrees Celsius).

Original article on Live Science.

Beachgoers on Sanibel Island in Florida experienced a rare sight last weekend as they watched crashing waves pummel the ocean's largest fish. The carcass of the 21-foot-long (6.5 meters) whale shark was discovered tumbling in the surf around 7:30 a.m. on Sunday (June 22), the Fort Myers News-Press reported. Experts are unsure what killed the enormous animal, but they suspect it could have been red tide, a type of harmful algal bloom.  

No matter the cause of death, a whale shark washing ashore is highly unordinary. "It's unusual even on a worldwide scale," said Bob Hueter, a shark biologist and director of the Center for Shark Research at Mote Marine Laboratory in Florida. "In southwest Florida, I'm not aware of any case at least in the 30 years I've been here."

The beached whale shark was a male that had died only days earlier, the Fort Myers News-Press reported. Based on its size, Hueter estimates the animal was no more than 20 years old. [In Images: Tale of an Injured Whale Shark]

Whale sharks (Rhincodon typus) are the largest fish in the sea and can weigh up to 60 tons (54 metric tons), according to National Geographic. These giants aren't predatory and instead are filter feeders. They open their wide mouths and suck in large amounts of water, and then push the water out through their gills, leaving plankton, shrimp, tiny fish and crustaceans behind.  

Whale sharks are found in large numbers off the Yucatan Peninsula this time of year, and occasionally one or two will make their way a little farther north, close to Florida. But this year, Hueter said that he's been hearing of several more whale shark sightings off the southwest Florida coast than he has in the past. "It seems like the animals are hanging around longer this summer," he said. "At the same time, we've had a very persistent red tide along this coast."

Red tide is the common name for a harmful algal bloom, which occurs when there's a higher-than-normal concentration of microscopic marine algae in the water. The blooms happen about every year off the Florida coast and are most often caused by Karenia brevis; this marine algae, which can turn water a reddish color, produces toxins that are harmful to fish and other marine animals, according to the Florida Fish and Wildlife Conservation Commission. 

"It's not impossible that this animal encountered a bloom of the red tide that, no doubt, would cause problems," Hueter said. He explained that red tides are known to start offshore in the sediment, and then rise up through the water column, where whale sharks and other marine animals are feeding.

Biologists with the Bailey-Matthews National Shell Museum in Sanibel took tissue samples of the shark to help determine if red tide is, in fact, what caused the animal's death. For now, authorities have decided to leave the shark on the beach and let nature take its course, the Fort Myers News-Press reported.

Original article on Live Science

With summer in full swing, many people are dutifully applying their sunscreen before heading outside. But your sunscreen may not be protecting you as much as you think, a new study suggests.

This isn't due to any fault of the product, though, but rather to the way people apply sunscreen — consumers tend not to apply sunscreen in a thick enough layer to get the full benefits, the researchers say.

The study, published July 24 in the journal Acta Dermato-Venereology, found that, when sunscreen with a sun-protection factor (SPF) of 50 is applied in a "typical" way (that is, in a relatively thin layer), it provides at best only 40 percent of the expected protection.

"There is no dispute that sunscreen provides important protection against the cancer-causing impact of the sun's ultraviolet rays," lead study author Antony Young, a professor at St. John's Institute of Dermatology at King's College London in the United Kingdom, said in a statement. "However, what this research shows is that the way sunscreen is applied plays an important role in determining how effective it is," Young said. [5 Things You Didn't Know About Sunscreen]

It's known that applying too little sunscreen can result in sunburns and skin damage. But the new study is one of the first to assess how much DNA damage occurs in the skin when people apply sunscreen in a "typical" way — that is, when they apply less than the amount used when manufacturers test sunscreens to determine their SPF rating. That amount, according to the study, is 2 milligrams per centimeter squared (mg/cm^2).

The study involved 16 people with fair skin who were exposed to ultraviolet radiation (UVR) to simulate sunlight. (Just a small part of the participants' skin was exposed.) Sunscreen was applied to participants' skin at various thicknesses, ranging from 0.75 mg/cm^2 (considered "typical" use), up to the recommended 2 mg/cm^2. Some participants were exposed to the UVR for five consecutive days, to mimic typical vacation conditions. The researchers also varied the dose of UVR exposure, ranging from low to high intensity.

At the end of the experiment, the researchers took biopsies of the skin that was exposed to the UVR. The biopsies showed that, after repeated UVR exposure, there was considerable DNA damage on areas that received no sun protection, even though the dose of UVR used on these areas was very low. (For ethical reasons, the dose of radiation used on unprotected skin was a minimal dose that would not induce sunburn.)

In fact, just one day's worth of low-dose UVR exposure to an area without sunscreen resulted in more DNA damage than five days' worth of high-dose UVR exposure to an area with sunscreen applied at recommended thickness, the researchers said.

DNA damage was somewhat reduced when sunscreen was applied at a thickness of 0.75 mg/cm^2, and it was considerably reduced when sunscreen was applied at a thickness of 2mg/cm^2.

Overall, the findings "demonstrate that public health messages must stress better sunscreen application to get maximal benefit," the researchers wrote.

To apply the right thickness of sunscreen, people need to use about 35 milliliters (ml) — or 1.2 ounces — of sunscreen for their whole body, according to a 2002 paper on the topic published in JAMA Dermatology. When the size of each body part is considered, people should apply a little more than half a teaspoon (3 ml) to their head and neck; a little more than half a teaspoon to each arm; a little more than a teaspoon (6 ml) to each leg and a little more than a teaspoon each to their chest and back, the JAMA Dermatology paper said.

The researchers also recommend that people use a higher SPF than they think is necessary, given that consumers tend to apply too little sunscreen.

"In theory, an SPF of 15 should be sufficient [to protect people's skin], but we know that in real-world situations, we need the additional protection offered by a higher SPF" of 30 or more, Nina Goad, of the British Association of Dermatologists, said in the statement. (SPF is a measure of how well a sunscreen protects against UVB rays, which cause sunburn.)

The findings also show that people shouldn't rely on sunscreen alone for sun protection, and that "we should also use clothing and shade," said Goad, who was not involved in the study.

Original article on Live Science.

Every spring, thousands of barnacle geese make a grand migration from their temperate winter habitat in northern Europe and northwestern Russia to their summer nesting grounds in the Arctic. It's a journey of more than 1,800 miles (3,000 kilometers) that usually takes about a month, but new research has found that rising temperatures in the Arctic are pressuring the geese to make the trip in a grueling one-week sprint.

Barnacle geese (Branta leucopsis) are medium-size water birds found in Europe, Russia, the United Kingdom, Wales and the Arctic, according to the National Audubon Society. Until recent years, the timing of the birds' spring migration meant they arrived in the Arctic right as the snowmelt exposed their nesting sites and initiated plant growth. The birds would almost immediately lay their eggs, which would then hatch 30 or so days later, right at the peak season for plant growth — perfect timing for hungry, growing goslings. [Photos: Birds Evolved from Dinosaurs, Museum Exhibit Shows]

But in the past few decades, scientists noticed that things have changed. Temperatures in the Arctic have been getting warmer earlier and earlier in the season — by about a day per year — and this is putting significant pressure on the migrating barnacle geese.

The geese are trying to keep up with these environmental changes, but they're struggling. Scientists have found that the geese still leave at about the same time every year, but the animals have shortened their travel time to the Arctic. A trip that used to take about a month now takes the geese only about a week, as the birds will spend less time at their stopover sites or will skip them altogether and just keep flying.  

Instead of promptly laying their eggs as they usually do when they arrive at their Arctic nesting grounds, the exhausted geese need more than a week to recuperate and build up enough energy before they can start nesting. By the time the animals are ready to lay their eggs, the grasses and plants the birds feed on have been growing for a few weeks. As a result, goslings emerge from their eggs after the peak growing season rather than during it, and that's causing the young birds' survival rate to decline.  

The researchers predicted that barnacle geese may not be able to keep up with a continually warming climate and, as a consequence, their population may suffer. However, the researchers also pointed out that geese are a social species, and if enough individuals leave earlier, the rest may follow.

The study was published online July 19 in the journal Current Biology.

Original article on Live Science.

Investigate and explore

During the hottest summer days, science museums can provide a cool break from the steamy temperatures outdoors — as an afternoon "getaway" in your hometown, a weekend day trip or part of an extended vacation.

Science centers, natural history museums and interactive spaces offer exhibits and programs that appeal to a range of ages. They provide opportunities for the entire family to explore exciting mysteries about the world around them, in a variety of displays that let you investigate and do activities together.

From immersive theater projections that hurtle you through space and time, to reconstructions of creatures that lived millions of years ago, here are some destinations for curious minds seeking a closer look at the many marvels that populate the planet under your feet, the sky above your head, the cosmos beyond the solar system and the inside of your body.

Museum of Science (Boston)

The Museum of Science features more than 700 permanent exhibits with numerous opportunities for hands-on, experiential learning about natural history, nanotechnology, engineering and energy.

If visitors crave an electrifying indoor lightning display, they can visit the museum's "Theater of Electricity" and encounter the world's largest air-insulated Van de Graaff generator, which hurls crackling bolts capable of sparking anyone's curiosity about storms and safety.

Temporary exhibits offered this summer include "Space: An Out-of-Gravity Experience," introducing visitors to the "sights, sounds, and smells" experienced by an astronaut living and working in microgravity on the International Space Station; and "Crocs: Ancient Predators in a Modern World," exploring the evolution and biology of crocodilians, the water-dwelling, fearsome reptile group that includes alligators and crocodiles.

American Museum of Natural History (New York City)

Dinosaur halls? Check. Suspended blue whale in an immense, dimly lit space populated with scenes of ocean life? Check. A round-trip ticket to the end of the universe and back in the planetarium theater? Check. New York's iconic American Museum of Natural History has a lot to offer — spectacular fossils, rare minerals, anthropology collections representing cultures worldwide, and hall after hall of dioramas that act as windows into the lives of animals around the world.

Fans of the popular "Night at the Museum" movies can search for some of the famous exhibits that come to life in the film, such as the T. rex, located in the Hall of Saurischian Dinosaurs; the Easter Island head that served as the model for "Dum-Dum," in the Margaret Mead Hall of Pacific Peoples; and Neanderthals in the Hall of Human Origins. Visitors can even pose for a selfie with a seated statue of Theodore Roosevelt in the Roosevelt Rotunda.

This summer, the interactive exhibit "Our Senses" challenges visitors to take a closer look at all the ways in which their sight, smell, hearing, taste and touch enable them to experience and interpret the world around them. An exhibit on the human microbiome, "Inside You," explains how trillions of microbes that live on and inside our bodies coexist with us to keep us healthy. And the space show "Dark Universe" offers a breathtaking tour of the cosmos, narrated by astrophysicist Neil deGrasse Tyson, to explore one of the universe's biggest mysteries — dark matter.

National Museum of Natural History (Washington, D.C.)

At the National Museum of Natural History, 124 million objects await you, including the Hope Diamond — the largest blue diamond in the world — a living coral reef and a collection of mummies. Permanent exhibitions cover earth sciences, dinosaur fossils, human diversity, and animals and their ecosystems, to name a few.

Inside FossiLab — a real fossil laboratory in one of the museum's public spaces — visitors can watch paleontologists as they unpack, clean, conserve and document new fossil arrivals and samples from the museum's extensive collection.

Like insects? The museum's Insect Zoo features live demonstrations, tarantula feedings, and opportunities to observe a number of insects and other arthropods, some of which are available for visitors to hold and touch.

Among the museum's temporary exhibits are, "Outbreak: Epidemics in a Connected World," showing visitors the causes of disease outbreaks in the modern world, as well as the methods for tracking and containing epidemics; and "Narwhal: Revealing an Arctic Legend," showcasing the biology and habits of this iconic ocean mammal, exploring its connection to Inuit culture, and diving deep into the icy Arctic habitat where narwhals live.

Fernbank Museum of Natural History (Atlanta)

With every step you take at the Fernbank Museum of Natural History, you're walking on fossils. The museum's floors, made up of 40,000 limestone tiles, hold the fossil remains of animals that lived more than 150 million years ago, in a shallow reef.

Fernbank is home to fossils representing some of the world's largest dinosaurs, and hosts Atlanta's biggest IMAX screen. Their collections and displays offer an introduction to Georgia's natural history as well as an overview of cultures, traditions and artifacts from around the world.

Curious about the science of the food on your table? The exhibit, "Food: Our Global Kitchen," open through August 19, offers summer visitors a chance to learn about the origins and history of different crops, spices and produce; the cultural traditions that shape our meals and how we share them with others; and the challenges of feeding more than 7 billion people in a warming world.

The Field Museum (Chicago)

Does the prospect of visiting the largest T. rex ever found appeal to you? How about exploring an Egyptian tomb, or witnessing DNA research? If that sounds exciting, a visit to The Field Museum is well worth your time, with exhibits that inspire an appreciation for nature and human culture.

Visitors can even experience a bug-size view of the world in the "Underground Adventure" exhibit, an immersive environment that offers an entirely new perspective on tiny creatures and how they live underground.

This summer, prepare to discover the dinosaurs that lived in what is now the coldest and most forbidding landscape on the planet — Antarctica. But 255 million years ago, Antarctica was covered in lush forests, and diverse populations of dinosaurs roamed the verdant landscape. "Antarctic Dinosaurs" introduces dozens of extinct species, including four dinosaur species that aren’t found anywhere else on Earth, and showcases the techniques and technologies used by the paleontologists who excavate and study these ancient animals.

La Brea Tar Pits and Museum (Los Angeles)

It's not every day that you can visit a museum that's also a dig site, where down-and-dirty paleontology is taking place on its very grounds. Mammal fossils on display at the La Brea Tar Pits and Museum emerged from — where else? — tar pits, which are just a short walk from the main museum building. Some of the tar pits are in the process of being excavated, with paleontologists working to extract the remains of ancient animals and plants buried there.

Inside the museum, more than 1 million ice-age fossils from the tar pits are on display, including mammoths, saber-toothed cats and dire wolves. At the center is the Fossil Lab, a large room surrounded by glass where visitors can watch preparators as they clean and assemble fossils, from the miniscule to the massive, and the museum offers behind-the-scenes tours that provide an up-close view of how researchers prepare and study these objects from the distant past.

As you stroll around outside, you may encounter small patches of ancient tar near the larger pits that were former excavation sites. Tours of the park's dig sites — past and present — offer a unique perspective of Los Angeles many thousands of years ago.

California Academy of Sciences (San Francisco)

The California Academy of Sciences promises "a daily dose of wonder," and is the only location on the planet where you can find a natural history museum, a planetarium and an aquarium under the same roof.

As if that weren't enough, there's also an educational play space for toddlers, and a Project Lab — a window into the research that takes place every day, involving 60 scientists and hundreds of researchers.

There are plenty of opportunities for hands-on experiences, such as touching sea creatures in the Discovery Tidepool, and handling pelts, shells and other specimens in the Naturalist Center. Stop by the Osher Rainforest exhibit — the biggest rainforest exhibit in the world — and drink in the rainbow of hues found in a variety of plants and animals that are native to the Amazonian rainforest, all housed in a temperature-controlled glass dome measuring 90 feet (27 meters) in diameter.

Planning an outdoor adventure this summer? Just make sure you steer clear of these frightening fungi, beastly bacteria and deadly diseases.

This story was updated on July 2, 2018.

Intro

Venturing outside in the cold this winter, with record-breaking low temperatures stretching from Maine to southern Florida, may take some courage, but these recent lows are nothing compared to the ones on this list.

Check out the places in the world that hold the records for the coldest temperatures ever measured on Earth.

International Falls, Minnesota, United States (- 40 Fahrenheit/- 40 Celsius)

International Falls is so serious about its status as one of the coldest places in the continental United States that it has actually taken another town to court over the title.

In 2002, International Falls took Fraser, Colorado, to court in order to finally settle who had claim to the title "Icebox of the Nation," according to a report from the BBC. They now celebrate that win by hosting the annual four-day Icebox Days festival, which includes events such as frozen turkey bowling, snow-sculpting and candlelit skiing.

While it is in fact only the second coldest place in the continental United States, International Falls boasts the lowest average temperature in the country, hovering between 32 and 36 degrees F (0 and 2 degrees C).

Stanley, Idaho, United States (-52.6 Fahrenheit/-47 Celsius)

The title of coldest place in the continental United States belongs to Stanley, Idaho, a town 130 miles (209 km) east of Boise. In addition to its record cold temperature, the town also holds claim to the highest number of coldest days between 1995 and 2005, according to a report by the BBC.

Situated within the Rockies, Stanley is surrounded by the White Cloud, the Boulder and the Sawtooth Mountain Ranges all of which contain peaks over 10,000 feet (3,048 m). The town is also surrounded by three national forests: the Boise, Challis and Sawtooth.

Prospect Creek, Alaska, United States (-78.16 Fahrenheit/-62.1 Celsius)

Prospect Creek is a very small settlement approximately 180 miles (290 km) north of Fairbanks, Alaska.

Originally, it was home to mining expeditions and the home base for the 27,000 people building the Alaskan Pipeline. Since the completion of the pipeline in 1977, there is little activity in the area.

Prospect Creek is known for having the lowest recorded temperature in the United States. In January of 1971, the record low temperature of nearly minus 80 degrees F (minus 62 degrees C) was recorded. Despite these frigid temperatures the oil in the pipeline doesn't freeze due to 4-inch-thick (10 centimeters) fiberglass thermal insulation, according to the Alaska Pipeline Operation Company.

Snag, Yukon Territory, Canada (-83.02 Fahrenheit/-63.9 Celsius)

Snag in the Yukon Territory holds the record for the coldest temperature ever recorded in North America. The village is located in the bowl-shaped valley of the White River, including Snag Creek, for which it was named in 1898.

In 1947, when the coldest temperature was recorded, the village of Snag boasted a population of eight to 10 natives and fur traders. The emergency landing strip and weather station staff of 15 to 20 meteorologists, radio operators and aircraft maintenance men rounded out the population.

The temperature was so cold that day that the meteorologists working at the station had to carve a new notch in the case of the thermometer and send the whole thing to be analyzed in order to determine the exact temperature, according to the Alaska Science Forum.

Yakutsk, Siberia (-83.92 Fahrenheit/-64.4 Celsius)

Yakutsk, the capital of the Russian republic of Yakutia, is one of the oldest cities in Siberia. It sits on the western bank of the Lena River, but winters are severe enough that even the frozen river is able to act as a seasonal road.

In 1822, Yakutsk was officially designated a city, today Yakutsk is a major administrative, industrial, cultural and research center, despite being six time zones away from Moscow.

Even local folklore is focused around how cold the place is. Every element on the periodic table can be found in the region, and local legend explains how that came to be: The god of creation had been flying around the world to distribute riches and natural resources, but when he got to Yakutia he got so cold that his hands went numb and he dropped everything, according to a report from The Independent.

Verkhoyansk, Siberia (-93.64 Fahrenheit/-69.8 Celsius)

Verkhoyansk is also a Siberian town located near the Arctic Circle. A river port, a fur-collecting depot, and the center of a reindeer-raising area, the town was founded in 1638, and was a place of political exile until 1917.

In addition to being the third coldest place in the world, it is also officially the third smallest town in Russia. There is a bright side though; while Verkhoyansk does have some of the most frigid winters in the world it has a remarkably wide range of temperatures between the seasons. Average monthly temperatures range from minus 50.4 degrees F (minus 45.8 degrees C) in January to 62 degrees F (16.9 degrees C) in July.

Oymyakon, Siberia (-96.16 Fahrenheit/-71.2 Celsius)

Oymyakon, in Siberia, holds the record for being the coldest permanently inhabited place on earth.

The village, which sits 217 miles (350 km) below the Arctic Circle, is home to more than 210,000 people, despite its ground being in a constant state of permafrost. Oymyakon's school shuts only when temperatures fall below minus 61 degrees F (minus degrees 52 C), and residents reportedly leave their vehicles running all day to keep them drivable, according to a report from the BBC.

Along with Verkhoyansk and Yakutsk, Oymyakon can be found in a region that was formerly nicknamed "Stalin's Death Ring," as it was one of the destinations for political exiles of the Soviet regime.

East Antarctic Plateau (-148 degrees Fahrenheit/-100 degrees Celsius)

The coldest place on Earth is on a frozen ice ridge of the East Antarctic Plateau between the summits Dome Argus and Dome Fuji, where researchers measured temperatures that reached minus 148 degrees Fahrenheit (minus 100 degrees Celsius). Not only was this the lowest temperature ever recorded on the planet, but it's also likely as cold as it can possibly get.

Scientists analyzed satellite data gathered between 2004 and 2016, during the dark winter months of July and August. Previously, in 2013, analysis of this data pinpointed record cold temperatures of minus 135 degrees F (minus 93 degrees C). But the data was recently recalibrated with updated readings from weather stations on the ground, incorporating atmospheric dryness. The new calculations found that drier air could drive temperatures down even further, by about 9 degrees F (5 degrees C), researchers reported in a study published June 25, 2018.

Pockets of this extreme cold were found in 100 sites in depressions atop the East Antarctic Plateau at an elevation of 12,467 feet (3,800 meters), the highest part of the ice sheet.

Leaving a water bottle sitting in your car sounds benign enough. But on a hot, summer day, the plastic can act as a lens, focusing light into a high-energy beam that's intense enough to burn material like car-seat upholstery.

Last summer, Idaho Power shared its video of a water bottle burning two holes in a car seat. And for this year's World Cup soccer tournament, the Russian water company Holy Water is selling soccer ball-shaped water bottles that can act as perfect light-focusing lenses. In a video published by Fontanka Ru, the ball-shaped bottle is seen focusing light so well that it ignites a box of matches and burns a hole in laminate flooring. [Photos: Top 10 Greatest Explosions Ever]

"The water bottle is acting like a lens that's focusing the light coming through the window," Odile Madden, a materials scientist at the Getty Conservation Institute in Los Angeles, told Live Science.

Light consists of numerous photons, which are subatomic particles that travel in a straight line, Madden said. Eyeglass and microscope lenses direct the photons so they converge on a point. "You can use that to see something better, get it in focus. Or, you can focus a lot of light onto a very small point and concentrate all that energy, and that can cause melting and burning," Madden explained.

Madden witnessed the astonishing power of laser-focused light years ago, when she was experimenting with using lasers to remove clear adhesives from artwork and artifacts. She discovered that the grooves in the adhesive worked to focus the laser and "turned up the power," subsequently burning or etching pits into the glass microscope slides she was using for the experiment. She published her findings in 2005 in the journal Lasers in the Conservation of Artworks. 

Everything lined up just right

What surprised Madden about the water bottle examples is that the light passes through the car window first, yet there's still enough heat left to go through the bottle and cause burning. "Conceivably, this would be worse on a hot day or if the window were down, because the window filters the light," she said.

"This is a good illustration of just how much energy there is coming from the sun," said Michael Doutre, a chemist at the Getty Conservation Institute who works with Madden in GCI's Modern and Contemporary Art Research Initiative, which studies plastic, among other materials. "We think of this as a cheap water bottle, but we're unintentionally creating an optically almost-perfect shape" for a lens, Doutre told Live Science.  

Doutre said that even after the sunlight passes through the car window, it hits the seat with about 600 watts per square meter of energy — about the same amount of energy from a small electric space heater — but focused on a tiny point that's smaller than a millimeter. A couple of seconds of that focused sunlight can easily heat up vinyl seat material to its decomposition temperature, thereby causing burning, Doutre explained.

But both scientists think it's unlikely that the water bottle could cause the seats to actually catch fire. That's because car materials, including seats, are made to be fire-retardant and self-extinguishing, said Madden. The plastic material many car seats are made out of, polyvinyl chloride, or PVC, doesn't propagate flames well, she said.

For burning to occur, the liquid in the bottle must be clear, so enough light can pass through it; this means that soda and juice drinkers can leave their bottles in the sun if they want — unless the soda is clear. A transparent bottle holding a clear carbonated liquid, like sparkling water or lime soda, could allow light to pass through just like a regular water bottle. "If you get the bubbles on the side, it would gather the light a little bit, but fundamentally it wouldn't really change anything," Doutre said.

For a water bottle to cause a fire, everything must line up perfectly: a smooth, spherical, transparent bottle full of a clear liquid that's placed at just the right point from both the light source and the flammable focal point. Both scientists said they suspect that the chances of that happening by accident are slim.

Nonetheless, said Doutre, "I'm not going to put a water bottle on a stack of paper anymore."  

Original article on Live Science.

A trip to the beach can be the perfect way to pass a summer's day. But as you search for a spot to place your towel, you should know you're not just sharing the sand with fellow beach lovers — you're sharing it with some pretty creepy critters, too. Although most microbes in the sand are harmless, some are linked with disease. Here are five types of pathogens found in sand.

Hookworms

Walking barefoot on a tropical beach may sound idyllic, but in some areas, you'll want to be wary of hookworms, which are parasites that can infect both people and animals. Some species of hookworm that typically infect cats and dogs can be transmitted to people through sand or contaminated soil, according to the Centers for Disease Control and Prevention (CDC).

This happens when infected animals defecate in sand or soil and pass hookworm eggs in their stool. People can then become infected if they walk barefoot or lie down on the infested sand or soil, the CDC says. Indeed, a Canadian couple recently revealed that they contracted hookworms in their feet while walking barefoot on a Caribbean beach. (These hookworms are typically found in tropical or subtropical regions.)

The hookworm larvae can burrow into unprotected skin and then crawl around in the top layers of skin. However, because humans aren't the normal hosts for these hookworms, the parasites usually don't live more than six weeks in people, the CDC says.

MRSA

The superbug MRSA is particularly problematic in hospitals, but the bacteria can also be found out in the environment, including on beaches, studies have found.

MRSA, which stands for methicillin-resistant Staphylococcus aureus, is a type of staph bacteria that can cause skin infections and is resistant to several antibiotics. Some people can carry staph bacteria or even MRSA on their skin or in their noses without showing symptoms. (In the United States, about one-third of the population carries staph and 2 percent carries MRSA without showing symptoms.) But in other cases, such as when a person gets a cut or wound in their skin, the bacteria causes an infection.

A number of studies have found staph bacteria and MRSA in seawater and in sand. For example, a 2012 study in the journal Water Research analyzed water and sand samples from three Southern California beaches, finding staph bacteria in 53 percent of beach sand samples and MRSA bacteria in 2.7 percent of sand samples.

It's unclear whether that amount of staph and MRSA bacteria in sand poses a health risk to beachgoers, and researchers have called for more studies to look into this question. But in the meantime, showering after a stint on the beach or in the ocean should help provide protection against staph and MRSA infection, the researchers of the 2012 study said.

Stomach bugs

You might have heard that swimming in ocean water could get you sick with a stomach bug. Indeed, health officials monitor water quality at beaches and close these beaches when bacteria levels are too high, in order to prevent illness. But what about bacteria in the sand?

Beach sand can also harbor a number of bacteria that can cause gastroenteritis, or stomach infections that lead to diarrhea, nausea and vomiting. A 2012 study in the journal Applied and Environmental Microbiology, which analyzed sand from 53 California beaches, found Escherichia coli and Enterococcus — bacteria typically found in human intestines — as well as Salmonella and Campylobacter, which are sometimes causes of food poisoning.

But could these bacteria in sand really make you sick? Maybe — a 2009 study that surveyed more than 27,000 Americans who visited the beach found that people who reported digging in the sand or being buried in the sand were more likely to develop gastrointestinal illness shortly after their beach trip than those who didn't report these activities. However, the researchers noted that their study couldn't prove that bacteria in sand caused the people's gastrointestinal illnesses.

Fungi

The fungus is among us at the beach, too. Types of fungi that cause skin and nail infections — which belong to a broad group known as "dermatophytes" — have been found on beaches. They may spread through direct contact with people, animals or sand, according to the American Society for Microbiology (ASM).

Common beach dermatophytes include Trichophyton mentagrophytes and Trichophyton rubrum, which can be causes of ringworm, athlete's foot and jock itch, according to ASM.

Other types of fungi found at beaches include species of Aspergillus, which may cause lung infections, and Candida, which can cause yeast infections. However, infections with Aspergillus andCandida are more common among people with weakened immune systems, ASM said.

Roundworms

At beaches that allow dogs, the sand might harbor Toxocara canis, a parasitic roundworm that typically infects canines, according to ASM. People can become infected with T. canis by accidentally swallowing soil that has been contaminated with dog feces that contain T. canis eggs, according to the CDC.

Still, the risk of catching this parasite from beach sand is unclear. However, a study in France conducted in the 1990s found T. canis to be a common parasite on beaches, and another study, this one in Australia, found no T. canis eggs in more than 250 samples from beaches and parks that allowed dogs.

Because this parasite is more commonly found in puppies than in older dogs, the Australian study concluded that the major risk of T. canis to humans is from environments where puppies are found.

Original article on Live Science.

Imagine a summer breeze. What smells are wafting in the wind? It could be the salty smell of the ocean, a burger sizzling on the grill or, if you're poolside, the chemical stench of chlorine.

Of course, chlorine is a necessary element for summer fun; after all, you wouldn't want to take a dip in a swimming pool without it. The chemical helps keep us safe from an otherwise bacteria-filled soup of pool water and pee. (Fun fact: That swimming-pool smell you associate with chlorine isn't actually chlorine at all but a compound called trichloramine, which forms when chlorine reacts with pee and sweat.)

But is chlorine dangerous?

It's true that "too much chlorine can cause a lot of [skin] irritation," said Dr. Ana Duarte, the director of dermatology at Nicklaus Children's Hospital in Miami. But the amounts that are used in swimming pools are typically not a cause for worry, she noted. [How to Fix 9 Common Skin Problems]

An overchlorinated pool, on the other hand, can cause eye irritation, dry out the hair and skin (by stripping them of natural oils), and sometimes cause color-treated hair to turn shades of green, Duarte told Live Science. Because of this, it's important to have the right levels of chlorine in the pool, she said.

Excess chlorine in the pool can sometimes also cause small amounts of vapor to come out of the water, which "can trigger [a person's] asthma," Duarte said, though she noted that she doesn't think this effect is too common.

"Perhaps it could happen in a freshly chlorinated pool or a super-chlorinated [one]," she said. But as overeager swimmers may recall, pools are typically closed right after pool keepers chlorinate the water so that some of those vapors can diffuse, she said. (In high concentrations, chlorine gas is known to be very poisonous. In World War I, for example, chlorine gas was used as a chemical weapon. Inhaling large amounts of the gas is poisonous and could cause what's called a pulmonary edema, or fluid buildup in the lungs, according to the New York State Department of Health.)

Recommendations from a dermatologist

In general, swimmers need not worry about chlorine. "If you're in a pool situation, in general, it's safe," Duarte said. "And if you do get a little bit of minor irritation, you can certainly shower off right after the pool and apply a good moisturizer to replenish some of those natural oils" that the chlorine may have stripped away.

Even if you don't rinse off, the consequences won't be dire, she said: You may end up with a bit of dry skin, or brittleness in your hair.

People who spend a lot of time in the pool, such as competitive swimmers or pool-loving kids, could have more of their natural oils stripped off their skin, in which case moisturizing can be very helpful, Duarte said. She specifically recommended using cream or ointment moisturizers rather than lotions. She also suggested using moisturizers that contain ceramides, which are natural oils in our skin.

To ward off eye irritation while swimming, "you can always wear goggles," she said. "If you don't want to wear the goggles, then maybe [you can use] some lubricating eye drops afterwards."And for sensitive hair, it can sometimes help to pretreat your hair with oil before getting into the water or to wear a swimming cap, Duarte said.

And infants older than a few months need not fear the pool. Following "the immediate period after birth … everybody's skin more or less develops the same quality and the same protective barriers," Duarte said. "So, I think the main thing with small infants is definitely avoiding peak sun hours and enjoying the pool early, and [making] sure the kids have swimming lessons and [that] they're supervised." Those things worry doctors more than the chlorine, she added.

Indeed, perhaps a more pressing concern is that globe of warmth that shines on us day after day. Don't forget to put on sunscreen and make sure you reapply, especially if you're swimming, Duarte said.

Originally published on Live Science.

You've just claimed a spot on the beach; the sun is rising overhead, and you're looking forward to a relaxing day of sea and sun.

And speaking of sun — you mustn't forget to apply a generous layer of protective sunblock. But when you reach for your tube of sunscreen, you notice that it's long past the stamped expiration date.

Should you use it anyway? [5 Things You Didn't Know About Sunscreens]

Sunscreens typically provide protection with active ingredients that absorb or reflect ultraviolet (UV) radiation, such as zinc oxide or titanium dioxide, and so-called "broad spectrum" products block out two types of potentially damaging UV radiation — UVA and UVB rays, the Melanoma Research Foundation reported.

Most sunscreens will remain effective up to three years after the container is opened — unless the brand's expiration date says otherwise, according to the Mayo Clinic. However, storage in hot places or exposure to moisture can break down a sunscreen's components and reduce its effectiveness even before it's "officially" expired, Dr. Lauren Ploch, a dermatologist, told Live Science in an email.

"Any ingredient in a personal care product — even inactive ones, like emulsifiers and preservatives — can degrade over time," Ploch explained. "This degradation is often accelerated by suboptimal storage conditions, so storing sunscreen in a hot car may make it ineffective even before its expiration date."

Expired sunscreen may be less effective at blocking UV rays, raising the likelihood of sunburn and an increased risk of skin cancer. But heavy creams, which generally provide better coverage and sun protection than gels or sprays, can still provide a shield between skin and sun, even if the sunblock is expired, Ploch said.

"Expired sunscreen may be better than no sunscreen, especially if the active ingredient is a physical sunblock like zinc oxide or titanium dioxide," she said.

However, sunscreens can differ widely in their composition of active ingredients and inactive ingredients, and the storage history of individual containers of sunblock can vary even more. Therefore, it's impossible to say for sure how effective an expired tube of sunscreen could be, and users would be far safer seeking an unexpired option if one is available, she said.

"I recommend borrowing sunscreen from someone else on the beach or going to a nearby store to buy something. Even small convenience stores and gas stations stock sunscreens now," Ploch said.

If you're caught without any sunscreen whatsoever, fabric can provide some protection from the sun, especially if the fabric is specially woven or treated to screen out ultraviolet rays, Ploch told Live Science. In clothing, a UPF (ultraviolet protection factor) rating describes how effectively clothing will protect you, much as SPF (sun protection factor) numbers represent the effectiveness of sunscreen.

But even UPF-treated fabric doesn't provide 100 percent protection, "so it's important to wear both sunscreen and sun-protective clothing," Ploch said.

Original article on Live Science.

Is it safe to get a "base tan" in the summer?

No. There is no safe amount of tanning.

Tanning isn't bad for you just because it comes with the risk of burning, which can cause skin cancer. Tanning is bad for you because your body doesn't even begin to tan until dangerous ultraviolet (UV) rays have pierced your skin and started to mess with your DNA. 

And that alone significantly increases the risk of skin cancer, said Dr. Roxana Daneshjou, a dermatology resident at the Stanford University School of Medicine. [5 Things You Must Know About Skin Cancer]

"There's really no such thing as safe tanning, other than … putting a fake color on your skin," Daneshjou told Live Science. "Fairer-skinned people may not even tan until they burn."

And while burning represents a more significant danger — because it means that skin cells have become so sun-damaged that they die — the skin damage that begins at the very start of the tanning process is still dangerous, Daneshjou said.

"Some people say, 'Well, I should tan, because that extra melanin will protect me.' But that logic doesn't make sense. You're doing so much damage just to get that little bit of protection," she said.

Melanin is a pigment found in skin cells that's produced when UV rays hit the skin. The more melanin produced, the darker the tan. (And people with more melanin in their skin have darker skin tones.)

It's true that melanin can protect the body to some extent against UV rays — it absorbs UV rays to a point, acting as the skin's natural sunscreen, Daneshjou said. But the process of adding an extra dose of melanin to the skin — in other words, tanning — is actually a defense mechanism that begins only after damage has been done.

Daneshjou also noted that people who tan for aesthetic reasons are hurting themselves in the long run. [7 Beauty Trends That Are Bad for Your Health]

Dermatologists break down the dangerous portion of UV light into two categories: UV-A and UV-B. Both cause the kind of DNA damage that can lead to skin cancer, but UV-A in particular can contribute to a second problem: It breaks down the natural collagen in the skin, which can lead to premature aging.

"Collagen is the support structure for the skin," Daneshjou said. Without the support structure, she said, skin wrinkles, thins and weakens, taking on a papery appearance.

No anti-aging product, even the dermatologist-recommended ones, can slow skin aging as much as simply using sunscreen in the first place, she said.

Daneshjou said that to prevent these kinds of problems, dermatologists recommend everyone (light- or dark-skinned) use sunscreen (broad-spectrum products, or clearly marked as protecting against both UV-A and UV-B) year-round. UV-B exposure increases in the summer and decreases in the winter, but UV-A exposure occurs year-round. And both forms of UV light can pierce clouds and cause damage on cloudy days.

"People say, 'Oh, I don't spend time in the sun,'" Daneshjou said. But such people should still wear sunscreen. UV light pierces car windshields, and can cause damage over the course of even short walks outside.

Daneshjou said people should apply about a shot-glass worth of sunscreen to their bodies when wearing a typical summer outfit.

Originally published on Live Science.

You may want to be careful when selecting a sunscreen this summer: About two-thirds of sunscreens available in the U.S. offer subpar protection or contain ingredients that may harm your health, a new report finds.

The report, from the Environmental Working Group (EWG), reviewed 650 beach and sport sunscreens for the group's annual Guide to Sunscreens, released today (May 22). EWG is a nonprofit advocacy organization in Washington, D.C., that focuses on environmental issues and public health.

The researchers ranked sunscreens based on several criteria, including whether ingredients listed in the products are linked with health hazards and how well the products worked to block ultraviolet A (UVA) and ultraviolet B (UVB) rays, both of which can damage skin and cause skin cancer.

The report found that only one-third (33 percent) of the products reviewed met EWG's strict standards and earned a spot on the group's list of "Best Beach & Sport Sunscreens."

"The majority of sunscreens available in the U.S. aren't as good as most consumers think they are," Sonya Lunder, a senior research analyst at the EWG, said in a statement. [5 Things You Didn't Know About Sunscreen]

Hazardous ingredients

One concerning finding is that nearly 65 percent of the nonmineral sunscreens contained oxybenzone, a chemical that may act as a hormone disruptor and that has been found to damage coral reefs. (Mineral sunscreens, which contain ingredients such as zinc oxide and titanium dioxide, protect the skin through a different mechanism than nonmineral sunscreens use.) Recently, Hawaii lawmakers took steps to ban sunscreens containing oxybenzone due to the chemicals' effects on coral, although Hawaii's governor has not yet signed the bill into law.

Another concerning sunscreen ingredient is a form of vitamin A called retinyl palmitate, which has been linked with skin tumors in animal studies, the EWG said. Although the percentage of sunscreens containing retinyl palmitate has dropped by more than 50 percent since 2010, about 12 percent of sunscreens still contain the ingredient, the EWG said.

Many sunscreens in the United States also fail to offer optimal protection against UVA rays, which don't necessarily cause sunburns but may cause skin aging and increase the risk of skin cancer, the EWG said. Although most sunscreens sold today meet current standards set by the Food and Drug Administration (FDA) for UVA protection, only about half of these sunscreens could be sold in Europe, where UVA protection standards are higher, EWG said.

In the new report, the group called for the FDA to approve additional sunscreen ingredients, already available in Europe, that offer stronger UVA protection.

Sun advice

Additionally, the EWG warned consumers to be wary of sunscreens with a very high SPF, or "sunburn protection factor," value. Higher SPF sunscreens (above 50) don't necessarily offer better protection from UV-related skin damage, and consumers who use these products may develop a false sense of security and therefore spend too much time in the sun, EWG said.

"SPF values of 75, 80 or 100 lull Americans into thinking their skin is fully protected from the sun's harmful rays for extended periods of time," David Andrews, an EWG senior scientist, said in the statement. "People tend to misuse these high-SPF products, spending more time in the sun without reapplying, putting them and their families at greater risk of UV damage."

The FDA has proposed capping SPF values at "50+" but the agency hasn't finalized this rule. In 2018, the EWG found 52 products with SPFs of 70 or higher, up from 10 such products in 2007.

The EWG also recommends that consumers avoid sunscreen "sprays," which don't necessarily provide a thick and even coating of sunscreen on the skin. The group noted that the number of spray sunscreens on the market has increased 30 percent since 2007.

Finally, the researchers stressed that consumers shouldn't rely solely on sunscreen to protect against skin cancer. People should also cover up with clothing, wear hats and sunglasses, try to stay in the shade, and avoid spending too much time in the sun between 10 a.m. and 4 p.m., when its rays are most intense.

Original article on Live Science.

For those who live in colder climates, slippery ice defines winter: in skating rinks, on frozen ponds, and on dangerously slick roads and sidewalks.

But why is ice so slippery?

It turns out that scientists didn't really know the answer to that simple question until recently. But new research has shown that ice's slipperiness may be due to "extra" molecules on the surface of the ice. [The Mysterious Physics of 7 Everyday Things]

Old theories make no sense

Because ice is less dense than liquid water, its melting point is lowered under high pressures. A long-standing theory says that this is what causes ice to be slippery: As you step on it, the pressure of your weight causes the top layer to melt into water.

"I think everybody agrees that this cannot possibly be, " Mischa Bonn, director of the molecular spectroscopy department at the Max Planck Institute for Polymer Research in Germany, told Live Science. "The pressures would need to be so extreme, you can't even achieve it by putting an elephant on high heels."

Another theory says that the heat created by frictionwhen you move across the ice produces the layer of water. However, ice is not only slippery when you are moving, as anyone who tries to stand on ice skatesfor the first time quickly discovers.

Even if pressure or friction melted the ice, could a layer of water explain the slipperiness? Daniel Bonn, a physicist at the University of Amsterdam in the Netherlands, doesn't think so.

"The water-layer theory doesn't make much sense," Bonn told Live Science. "If you spill some water on your kitchen floor, it becomes slippery but not very slippery ... Just a layer of water will not do it."

Loose molecules

Mischa and Daniel Bonn, who are brothers, published a paper May 9th in the Journal of Chemical Physicsdescribing the surface of ice. Rather than a layer of liquid wateron the surface of ice, they found, there were loose water molecules. Mischa Bonn compared it to a dance floor that is "filled with marbles or ball bearings." Slipping across the surface of the ice is simply "rolling" on these molecular marbles.

Ice has a very regular, neat crystal structure, where each water molecule in the crystal is attached to three others. The molecules on the surface, however, can only be attached to two others. Being so weakly bonded to the crystal allows these surface molecules to tumble, and attaching and detaching themselves to various sites on the crystal as they move.

Even though slipping on iceis caused by essentially rolling over these water molecules, this layer of molecules is not the same as a layer of liquid water. These molecules and the slipperiness exist at temperatures far below water’s freezing point. In fact, the way these molecules move so freely and diffuse across the surface actually makes them look more like a gas, Daniel Bonn said.

"For me, it's a gas — a two-dimensional gas rather than a three-dimensional liquid," he told Live Science.

But if ice is slippery because of loose surface molecules, is ice uniquely slippery? Not really, said Martin Truffer, a physics professor at the University of Alaska Fairbanks. It is not so much the nature of ice that is unique but rather our relation to it, he said.

"What's unusual about ice is, we usually encounter it so close to the melting point, " Truffer told Live Science. "It's really the only material where we have the gas phase, the liquid phase and the solid phase within the normal climate range that we live in."

Truffer, who lives in Fairbanks, Alaska, has experienced ice very far from the melting point: When it gets to minus 40 degrees Fahrenheit (minus 40 degrees Celsius), he said, the snow "becomes like sandpaper." Truffer's observation lines up with what the Bonns found. At ultralow temperatures, the molecules on the surface don't have as much energy to break and create bonds as they roll around, so the ice becomes nonslippery.

The temperature for maximum slipperiness, according to their research data, is around 19 degrees F (minus 7 degrees C).

But some people already knew that; it's the temperature most indoorspeed-skating rinks have been using for years.

Original article on Live Science.

As average temperatures rise across the planet, the frozen Arctic is heating up faster than anywhere else.

With that warmth comes a surprising twist: Unusually warm Arctic winter temperatures are linked to bitter cold and snow in other parts of the Northern Hemisphere, such as the northeastern U.S., parts of northern Europe and northern Asia, according to an analysis of 66 years' worth of climate data.  

And the relationship between Arctic warmth and severe winter weather was strongest in in the northeastern U.S. — in fact, a temperature spike in the Arctic meant that the U.S. Northeast was two to four times more likely than usual to experience a bout of extreme winter weather, the scientists reported in a new study. [The 10 Worst Blizzards in US History]

Past climate projections predicted that, in a warming world, winters would be the seasons to heat up the fastest — and yet recent winters in the Northern Hemisphere were more severe than scientists anticipated, said Judah Cohen, the study's lead author and director of seasonal forecasting at Atmospheric and Environmental Research, an organization that assesses risks from weather events and climate change.

To understand what might be driving these unusual episodes, Cohen and his colleagues looked at pulses of warmth in the Arctic during winter months, to see how they lined up against weather anomalies elsewhere in the globe.

"When the Arctic pulse is warm, you tend to get an increase in occurrences of extreme winter weather across the midlatitudes, including the eastern U.S., northern Europe and northern Asia," Cohen told Live Science.

The relationship between spiking Arctic warmth and pockets of cold to the south was "really, really strong" — and it was strongest in the eastern U.S., Cohen said.

Since 1990, the eastern U.S. has been visited by winter storms so severe that they earned highly dramatic nicknames, such as "Snowzilla," "Snowmaggeddon" and "Snowpocalypse." The increase in incidences of extreme storms with heavy snowfall corresponded with periods of excessive Arctic warmth, the study authors wrote.

Disruption comes in waves

How does this relationship work? As the scientists' observations reflected only the comparison of weather patterns over time — and not what was driving them— the researchers could not conclude that a warmer Arctic was directly responsible for harsh winter storms in the U.S., they reported in the study.

But answers may lie in another atmospheric disturbance linked to a warming Arctic, Cohen said.

According to the study, data from past decades showed that fall snow cover in Siberia increased as the Arctic warmed, which cooled northeastern Eurasia. Meanwhile, melting sea ice fueled warmer temperatures in northwestern Eurasia.

These air-temperature changes close to the surface led to similar changes higher up in the atmosphere. This, in turn, affected the jet stream — a conveyer belt of wind that carries warm air and moisture around the globe — by increasing its "waviness," making jetstream waves dive farther south and stretch farther to the north. In turn, this extra amplification can alter the movement of cold air masses near the pole, otherwise known as the polar vortex, Cohen explained.

And this disturbance of the polar vortex could end up shaping conditions that worsen winter weather in the U.S.

"The cold air that's normally confined to the Arctic, it's kind of dammed in by the polar vortex itself — because winds normally blow from west to east inside the polar vortex, so it acts as barrier, keeps the cold air to the north and the mild air to the south," Cohen said. "When it breaks down, the cold air that's penned up in the Arctic spills to lower latitudes, and that's when you get those episodes of severe winter weather."

Arctic scientists like to say that "what happens in the Arctic doesn't stay in the Arctic," but the interconnectivity between Earth's dynamic atmospheric systems is no laughing matter, Cohen said. The complexity of these systems is reflected in emerging disruptions that are likely the products of climate change, though there is still much to be learned about how climate change could shape weather patterns around the world, the study authors reported.  

"I'd argue that our expectations for climate change were overly simplistic," Cohen said. "It was kind of expected that if you warm the Arctic, the only thing that's going to lead to is just milder temperatures everywhere — and that's not a complete picture."

The findings were published online today (March 13) in the journal Nature Communications.

Original article on Live Science.

A powerful storm is on track to strike the U.S. East Coast tomorrow, the second nor'easter to visit the area in two weeks. The storm will arrive tonight (March 6) at 10 p.m. EST and will last until 4 a.m. on Thursday (March 8), according to a winter storm warning issued today (March 6) by the National Weather Service (NWS).

But will this storm soak the region with rain or bury it in snow?

"Substantial snow accumulations" could blanket New York City and parts of Long Island, New Jersey, Connecticut and the Hudson Valley, the NWS reported. However, exact amounts of snowfall are a little harder to pin down, and estimates for some areas range from nearly 18 inches (46 centimeters) to as little as 5 inches (13 cm), according to the NWS.

Why is tomorrow's snowfall proving so tough to predict? [Weirdo Weather: 7 Rare Weather Events]

For this storm's forecast, agreement among weather models is actually above average, but "the devil is in the details," Stephen DiRienzo, a meteorologist with the NWS, told Live Science in an email.

"The greatest uncertainty in the forecast is along the rain/snow transition line, which for this storm extends from Philadelphia to New York to Boston," DiRienzo explained.

"Oftentimes, there is literally a straight edge to the boundary between rain and snow, and so on the snowy side there may be large accumulations of snow, with none on the rainy side of the boundary. So, where that line between rain and snow sets up, that will determine tomorrow's weather for millions of people," he said in the email.

In this case, the storm shifting to the southeast would mean that major northeastern cities would experience substantial snowfall, while a shift to the northwest would douse those cities with heavy rainfall, DiRienzo said.

That explains the variability in NWS maps showing potential snowfall: The high-end map estimates 10 inches (25 cm) of snowfall for New York City, while the low-end map predicts 0 inches (0 cm). The prediction is similar for Boston, with a snowfall range from a high of 7 inches down to 0 inches (18 to 0 cm).

"At this point, we're just slightly unsure of the exact axis of the heaviest snowfall," Michael Musher, a meteorologist with the Weather Prediction Center at the National Oceanographic and Atmospheric Administration (NOAA), told Live Science.

"There's always variability in each system — it just depends on its development and orientation," Musher said.

Various computer models have forecast similar movements for the storm — what remains to be seen is how well they can forecast temperature from the ground up into the upper atmosphere, which could affect the position of the rain/snow transition line, DiRienzo said.

To track these temperatures, weather balloons are deployed by the NWS twice daily — at 7 a.m. and 7 p.m. local time — from about half of the agency's offices, ascending to heights of over 100,000 feet (30 kilometers). The data gathered closer to the storm's arrival, such as data from the weather balloons slated to go up tonight and early tomorrow morning, will help provide more-accurate estimates of where the storm's heaviest snow will fall, DiRienzo said in the email.

"The computer models will give a forecast of expected temperatures in the atmosphere during tomorrow's storm, but those 7 a.m. balloon launches will be critical to determining where the rain-snow line sets up, and therefore, what weather millions of people can expect," he said.

Original article on Live Science.

There's an added challenge at the 2018 Winter Olympics, according to news reports: an outbreak of norovirus.

More than 40 security guards have fallen ill with the stomach bug, The Washington Post reported yesterday (Feb. 6). In an effort to stop the spread of the virus, more than 1,200 people have been quarantined while they are tested for the disease, according to the Post.

The highly contagious stomach virus, which causes diarrhea and vomiting, is notorious for spreading easily at close-quarter events, Live Science previously reported, including on cruise ships and at conventions.

One reason that norovirus is so contagious is that the symptoms — including vomiting — come on very quickly, Dr. Amesh Adalja, a senior scholar at the Johns Hopkins Center for Health Security in Baltimore, told Live Science in 2016. That means that people may vomit in places they normally wouldn't, thereby spreading virus particles to others, Adalja said.

What's more, these particles can survive for days outside the body, he added.

And it doesn't take much to get a person sick: Coming into contact with as few as 18 norovirus particles can make a person ill, according to the Centers for Disease Control and Prevention (CDC). Once infected, a person can shed billions of these particles, the CDC says.

The Pyeongchang Organizing Committee is investigating the source of the virus and how it spread, according to The Washington Post. The security guards who fell ill were all staying at a youth center in the mountains near Pyeongchang, the Post said.

Read more at The Washington Post.

Originally published on Live Science.

Chicago in the wintertime is an unforgiving place. Want to move around town? Don't own a car? Prepare to stand on a raised train platform for 10 minutes, and try to expose as little of your skin as possible to the raw, blasting wind. Is the temperature below zero again? Here's a weak outdoor heat lamp on the platform; be grateful for it.

I found myself on one of those platforms, shivering under one of those lamps, last Saturday (Dec. 30) as the temperature dipped to 3 degrees Fahrenheit (minus 16 degrees Celsius). I'd just come from lunch, during which I'd hijacked one of the restaurant's outlets to charge my phone up to 100 percent of its battery capacity; my next destination was downtown, in an area with which I was unfamiliar, and I was making sure to have my GPS at hand for guidance. And yet, when I pulled my device out of my pocket on that platform to check my route, the charge had already plummeted: The readout in the top-right corner of my screen blinked red, "1% ...1% ...1%." Moments later, the device was dead.

Why?

The short answer is that batteries rely on chemical reactions to work, and freezing temperatures slow or stop those reactions.

Lithium-ion batteries, the commonplace rechargeables that power much of our modern lives and live inside almost every cellphone, discharge electric current as individual lithium ions move through solution from one end of the battery (the anode) to the other end (the cathode). When the battery is drained, all of those ions are embedded in porous graphite in the cathode. When it's fully charged, they're all embedded in the anode, according to Ann Marie Sastry, co-founder and CEO of Sakti3, a Michigan-based battery technology startup, who spoke to Live Science for a past article.

Chemists don't have a good idea of exactly how cold slows the reactions that take place inside lithium-ion batteries. "The exact mechanisms leading to poor performance of lithium-ion batteries at cold temperatures are still not well understood," a team of battery engineers wrote in a paper in the Journal of The Electrochemical Society in 2011.

But it's broadly true that extreme cold slows the reactions in batteries of all types to a crawl.

When my phone's charge meter read "1%" on that platform, all of the ions hadn't suddenly jumped to the cathode. In fact, cold temperatures prevent the kind of slow discharge battery ions do under room temperatures, as the engineering website Lithiumpros.com explains. But because the bitter cold had slowed or stopped the reaction inside the battery, it discharged less current than the phone needed to keep working, chemist Anne Marie Helmenstine, who has a Ph.D. in biomedical sciences and has taught chemistry at various academic levels, wrote in 2017 on thoughtco.com. The phone interpreted that weak discharge as a sign that the battery was nearly dead, and shut itself off shortly afterward.

Fortunately, I didn't attempt to recharge my battery while the phone was still frozen. Under very cold temperatures, as Lawrence Berkeley National Laboratory chemist Stephen J. Harris wrote on his website, the lithium-ion charging process can fail horribly. Under normal conditions, applying an electric current to the battery would transport ions back into the pores in the anode's graphite. When the battery is frozen, though, the ions don't enter the graphite. Instead, they exit the solution and plate across the surface of the graphite as solid lithium. That process can wreck the performance and life of a battery.

When my phone did warm up again, it proved it didn't need a charge anyway; it just required warm enough temperatures to enable the reaction. As I pressed the power button on the newly heated device, it turned on, and the battery meter read "94%."

The ions hadn't gone anywhere. They just couldn't move properly in the cold.

Originally published on Live Science.

Do humans have a shedding season? According to an analysis of Google searches for "hair loss," that may be the case: A new study finds that these searches spike in the summer and fall.

Hair loss searches were greatest in the summer in both hemispheres of the globe, followed closely by the number of searches in the fall, according to the study, published yesterday (Oct. 24) in the British Journal of Dermatology. The searches for hair loss reached a low during the spring.

Though Google searches for hair loss do not necessarily mean that the person who did the search has hair loss, the findings "back up the results of smaller studies involving patients that showed greater [hair loss] in the summer months," said senior study author Dr. Shawn Kwatra, an assistant professor of dermatology at Johns Hopkins University School of Medicine. [The 7 Biggest Mysteries of the Human Body]

Ultimately, the findings suggest that people "can expect to have more [hair loss] in the fall and summer," Kwatra told Live Science.

The researchers looked at data from 2004 to 2016 from eight countries around the world, covering both the northern and southern hemispheres: the United States, the United Kingdom, India, Canada, Australia, South Africa, New Zealand and Mauritius (an island in the Indian Ocean). To avoid any ambiguity in the search analysis, the researchers included only English-speaking countries.

For countries in the Northern Hemisphere, the researchers defined spring as March, April and May; summer as June, July and August; fall as September, October and November; and winter as December, January and February. In the Southern Hemisphere countries, the seasons were the opposite, such that the northern spring was the southern fall and the northern summer was the southern winter, and so on.

Previous studies have suggested that there may be a link between seasonality and hair loss, the researchers wrote. For example, earlier research has shown that people have the highest rates of "telogen" hairs in the summer, and the lowest rates of these hairs in the winter. Telogen hairs refers to hairs in their final stage of growth. (There are three stages of hair growth.) Hairs in the telogen stage are most likely to fall out.

Monthly temperature data for the eight countries were obtained from the National Oceanic and Atmospheric Administration.

Though "temperature was associated with hair loss, there are likely other factors, such as UV index, that may help to explain the relationship between seasonality and hair loss," Kwatra said. The UV index refers to the strength of ultraviolet rays outdoors; it's possible that UV rays could influence hair loss, according to the study. 

Originally published on Live Science.