21. People have climbed Everest without oxygen
On May 8, 1978, climbers Reinhold Messner and Peter Habeler became the first to summit Everest without the aid of oxygen, according to the journal Respiratory Physiology and Neurobiology. Messner described his feelings upon reaching the top like this: "I am nothing more than a single narrow gasping lung, floating over the mists and summits."
22. Mid-ocean ridge is the longest mountain chain
To find the world's longest mountain range you'd have to look down, way down. It is called the mid-ocean ridge, and the underwater chain of volcanoes spans some 40,389 miles (65,000 km), according to NOAA. It rises an average of 18,000 feet (5.5 kilometers) above the bottom of the sea.
As lava erupts from the seafloor it creates more crust, adding to the mountain chain, which stretches around the globe.
23. Coral reefs are the largest living structures
Coral reefs support the most species per unit area of any of the planet's ecosystems, rivaling rain forests. And while they are made up of tiny coral polyps, together coral reefs are the largest living structures on Earth — a community of connected organisms — with some visible even from space, according to NOAA.
24. The Mariana Trench is the deepest spot
How low can you go? According to NOAA, the deepest point on the ocean floor is 36,200 feet (11,033 meters) below sea level in the Mariana Trench. The lowest point on Earth not covered by ocean is 8,382 feet (2,555) meters below sea level, but good luck walking there: That spot is in the Bentley Subglacial Trench in Antarctica, buried under lots and lots of ice.
25. The Dead Sea is the lowest point on land
The lowest point on land, however, is relatively accessible. It's the Dead Sea between Jordan, Israel and the West Bank, according to the European Space Agency (ESA). The surface of this super-salty lake is 1,400 feet (427 m) below sea level.
26. Lakes can explode
In Cameroon and on the border of Rwanda and the Democratic Republic of the Congo there are three deadly lakes: Nyos, Monoun and Kivu. All three are crater lakes that sit above volcanic earth. Magma below the surface releases carbon dioxide into the lakes, resulting in a deep, carbon dioxide-rich layer right above the lakebed. That carbon dioxide can be released in an explosion, asphyxiating any passersby, according to Nature.
27. We're losing fresh water
As the climate changes, glaciers are retreating and contributing to rising sea levels. It turns out that one particular glacier range is contributing a whopping 10 percent of all the meltwater in the world. That honor belongs to the Canadian Arctic, which lost a volume equivalent to 75 percent of Lake Erie between 2004 and 2009.
28. Glaciers are melting fast
Humans leave our mark on the planet in all sorts of weird ways. For example, nuclear tests in the 1950s threw a dusting of radioactivity into the atmosphere. According to the American Geophysical Union, those radioactive particles eventually fell as rain and snow, and some of that precipitation got trapped in glaciers, where it forms a little "you are here" layer for scientists trying to date the age of glacial ice.
Some glaciers are melting so fast, however, that this half-century of history is gone.
29. Earth used to be purple
It used to be purple … well, life on early Earth may have been just as purple as it is green today, suspects Shil DasSarma, a microbial geneticist at the University of Maryland. Ancient microbes, he said, might have used a molecule other than chlorophyll to harness the sun's rays, one that gave the organisms a violet hue, he suggests.
DasSarma thinks chlorophyll appeared after another light-sensitive molecule called retinal was already present on early Earth. Retinal, today found in the plum-colored membrane of a photosynthetic microbe called halobacteria, absorbs green light and reflects back red and violet light, the combination of which appears purple. The idea may explain why even though the sun transmits most of its energy in the green part of the visible spectrum, chlorophyll absorbs mainly blue and red wavelengths.
30. The planet is electric
Thunder and lightning reveal our planet's fiercer side. A single stroke of lightning can heat the air to around 54,000 degrees Fahrenheit (30,000 degrees Celsius), according to the book Energy by Don Herweck, causing the air to expand rapidly. That ballooning air creates a shock wave and ultimately a boom, better known as thunder.
Bonus fact: Did you know there are about 6,000 lightning flashes around the Earth every minute?