Empires have shaped human history, often growing from a single city or cultural group into territories spanning continents.

Some empires rose through conquest, and others grew through trade or shrewd alliances. Their borders, captured in maps described by historians or revealed by long-forgotten burials and artifacts, show just how far their influences once reached.

Whether you’re a casual history fan or a devoted scholar of the ancient to modern world, this quiz offers a chance to test your knowledge of bygone empires and the lands they once ruled.

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—Ancient Egypt quiz: Test your smarts about pyramids, hieroglyphs and King Tut

—Roman emperor quiz: Test your knowledge of the rulers of the ancient empire

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Rainforests are some of the most important and diverse ecosystems on Earth. Found across several continents, these vast forests are home to millions of plants and animal species, many of which can't be found anywhere else. Many rainforests, both tropical and temperate, also play a crucial role in regulating the planet's climate by absorbing carbon dioxide and producing oxygen.

Rainforests vary immensely in size. Some stretch across multiple countries and cover millions of square miles, while others are much smaller but still support incredible biodiversity. Understanding the relative size of these rainforests helps us appreciate their role on our planet and the challenges involved in preserving them.

In this quiz, you'll test your knowledge by sorting the top 10 biggest rainforests from largest to smallest. Click on and drag the blue rectangles to place them in the right order. Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button.

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Earth quiz: What do you know about our planet's most amazing features?

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As placental mammals, humans give birth to live young. Pregnancy begins on the first day of the last menstrual period, roughly two weeks before conception.

A human pregnancy consists of three trimesters and generally lasts around nine months. But how much do you know about how babies develop? For example, did you know some cell types appear only during pregnancy, or that hair usually grows thicker and lusher during pregnancy due to hormones, but that this extra hair falls out months later after giving birth?

Think you can conceive of all things related to pregnancies? Take this quiz to find out if you can deliver! Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Good luck!

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• Human evolution quiz: What do you know about Homo sapiens?
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Ancient armies fought with a variety of weapons, each shaped by the materials, tactics and cultures of their time. From swords to guns to catapults, each weapon played a unique role in the military strategies of the past. Many of these weapons now survive only in pieces. Yet even the smallest fragments give clues to how these devices were used and by whom.

Whether you're a casual history fan or devoted scholar of ancient warfare, this quiz offers a chance to see the past in a new way. Go ahead; test your knowledge!

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• Ancient Egypt quiz: Test your smarts about pyramids, hieroglyphs and King Tut
• Roman emperor quiz: Test your knowledge on the rulers of the ancient empire
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Earth is rocky, wet and older than the hills. But do you know its secrets? For instance, why do deserts form next to oceans, and what's the oldest river in the world? Or even facts that might get asked during a quiz night, like which continent is the largest? Test your Earth knowledge now by taking this quiz.

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• US volcano quiz: How many can you name in 10 minutes?
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NASA's Artemis II mission, which shot humanity back to the moon for the first time in over 50 years, has captivated people around the world. As part of NASA's Artemis program, the 10-day flight tested key systems designed to return astronauts to the lunar surface, where NASA says it will establish a lunar base that will act as a staging post for future missions to Mars.

Data from the mission will be used to advance our understanding of human health in space, including the impacts on sleep and the effects of increased radiation and microgravity on health. The four Artemis II crewmembers were also trained in geology to make observations of the lunar surface, including identifying impact craters and ancient lava flows.

How much do you remember about humanity's greatest adventure in half a century? Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Good luck!

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• Moon quiz: What do you know about our nearest celestial neighbor?
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Octopuses are a useful reminder that complex life can be organized in very different ways. With no backbone, their anatomy departs sharply from the body plans many people are familiar with. They are classified as cephalopods, a class of animals that includes squid, nautiluses and cuttlefish.

Octopuses can rapidly change the color and texture of their skin, manipulate objects with remarkable dexterity, and navigate environments that demand both flexibility and control. Scientists study these traits because they offer insight into how perception, movement and problem-solving evolved in invertebrates.

Think you know everything there is to know about octopuses? Take our quiz to find out.

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While devices like smartphones and laptops are ubiquitous now, these machines weren't always so common. The origins of computing go back well before the advent of electronic machines. From the abacus in ancient times to Electronic Numerical Integrator and Computer (ENIAC) in 1946, the history of computers is broad, with machines taking on all sorts of shapes and sizes over centuries of development.

In modern times, personal computers have shrunk in size and weight to become sleeker and portable. At the same time, we have larger computing and more powerful systems like supercomputers that boast incredible power, and quantum computers that promise to usher in an entirely new computing paradigm.

Think you know everything there is to know about the world of computers? Take our quiz to find out. Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button!

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The Americas have been home to humans for tens of thousands of years, with the first people arriving during the last ice age, when woolly mammoths, giant sloths and saber-toothed cats roamed the land.

These Indigenous Americans left behind clues about their lives, including prehistoric footprints of a caregiver and a squirmy toddler in what is now New Mexico and a heartbreaking cremation burial of a 3-year-old child in what is now Alaska.

But how much do you know about the first people to reach the Americas? Take our quiz to find out.

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If you love puzzles and science, you've come to the right place. With our new daily puzzle, you have six attempts to guess the science word of the day and complete the word chain.

After every guess, letters that appear in the word will get a yellow chain link, and if they're in the right place the link will go green. Get them all right and you'll earn a space on our leaderboard.

Let us know how you scored by leaving a comment below (but no spoilers please), and be sure to check back every day for a new word. Good luck!

The world of science news never sleeps, but even we need to take a break every now and then. And what better way than to give our collective brains a good workout with sudoku?

The rules are simple: Each row, column and 3 x 3 box must contain the numbers 1 to 9, with no repeats. Sounds simple, right? Sometimes it is; other times, it's a little more challenging. (That's when tapping the hints button comes in handy.) Regardless, it's a great way to step back for a bit and crunch some numbers.

We have three new sudoku puzzles of varying difficulties every day — easy, medium and hard — so be sure to bookmark this page and try a new challenge. Enjoy!

Easy, 36-45 clues

Medium, 28-35 clues

Hard, 17-27 clues

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Our species, Homo sapiens, has been evolving for more than 300,000 years, but the story of human origins starts much earlier. Since evolving from the common ancestor that we share with our closest living relatives, chimpanzees and bonobos, there have been many different species along the human lineage — known as hominins.

Scientists who study human origins and evolution, called paleoanthropologists, sometimes find new hominin fossils that give us a glimpse into our evolutionary history. And advances in the analysis of ancient proteins are helping to identify which species a fossil belongs to, and whether they were male or female. We now know there were large periods of time when multiple hominin species shared the landscape, and that sometimes they mated.

How much do you know about the origins and evolution of our closest evolutionary relatives? Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Good luck!

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• Human evolution quiz: What do you know about Homo sapiens?
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The fearsome Tyrannosaurus rex is perhaps the most iconic dinosaur that ever lived. Ever since the discovery of the first T. rex fossil in Hell Creek, Montana, in 1902, this gigantic predator — with its terrifying teeth and strangely tiny arms — has fascinated people of all ages, and played a starring role in books and films, including the Jurassic Park movies, as well as taking pride of place in museums around the world.

Yet, our picture of how this dinosaur looked and lived has changed markedly thanks to more than a century of scientific discoveries. Think you know everything there is to know about the king of the dinosaurs? Well, start the quiz below to find out if your knowledge is dino-mite or a faded fossil.

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Editor's note: This article was updated on Jan. 8 at 5:00 a.m. ET to correct a conversion in a question answer.

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Spanning over 2.2 million acres (890,000 hectares), Yellowstone National Park is stuffed full of stupendous scenery created by volcanoes and earthquakes or carved out by ice and water.This rich environment also creates a home for a multitude of wildlife, but how much do you really know about it? Start the quiz below to find out if your knowledge is steaming hot like a geyser or stuck back in the ice age.

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Primates — the mammalian group that includes humans — are found pretty much everywhere on Earth, from equatorial rainforests to scientific research stations in Antarctica. This hugely diverse order appeared before the dinosaurs went extinct, with wild populations of non-human primates evolving to live in niches across three continents — Asia, Africa and Central/South America.

Primates don't just live in lots of places; there are also hundreds of species and subspecies. In fact, the order primates is the fourth most biodiverse mammal order in the animal kingdom — yet the majority (62.6%) of primates are threatened with extinction.

Scientists researching primates, called "primatologists," have learned a lot over the years about our closest evolutionary relatives. For example, did you know that chimps have opposable big toes, or that not all monkeys can swing through the trees? Or even that there are some primates that are neither monkeys nor apes?

Fancy yourself a primatologist? Put your knowledge to the test below!

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Each week, Live Science highlights an interesting medical case report in its Diagnostic Dilemma series. We describe the patient and their symptoms, the testing and history-taking that revealed their diagnosis, their course of treatment and their ultimate health outcomes. We also highlight what makes the case unique, whether it's the rarity of the diagnosis, the unusual constellation of symptoms, or a novel therapeutic approach.

How many Diagnostic Dilemmas have you read — and can you guess the diagnosis? Take our quiz that draws from the cases we highlighted in 2025 and see if you can figure out each patient’s ailment. Tell us how you got on in the comments below.

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Whether you're cooking up chemistry, getting physical with physics or bending your mind over mathematics, one thing that remains constant is, well, constants. Some numbers are so fundamental to the way we conduct science that we'd be lost without them, and their discovery has helped us better understand the world around us.

So how many of these key figures do you know? Try our new quiz and find out. We'll be dropping another number in the mix every day for you to guess, and if you prove yourself to be a numberphile, maybe you'll make it to the top of our leaderboard. All you need to do is register and your score will be saved, and be sure to leave a comment and share how you got on (but no spoilers please).

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—Live Science crossword: Test your knowledge on all things science with our weekly, free puzzle!

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Archaeologists need to have excellent attention to detail. They'll examine the curve of a potsherd, measure the precise angle of a carved block of stone, or perceive a barely visible hole in a bone to identify important details about our collective human history.

Think you've got what it takes to be an archaeologist? Let's see how well you can identify some of the world's most famous artifacts from just a sliver of the image. No whip or fedora needed — but keep an eye out for snakes!

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• Ancient Egypt quiz: Test your smarts about pyramids, hieroglyphs and King Tut
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Television and internet ads regularly extol the classic beauty of gold jewelry and dazzling shine of cut gemstones. While we're all familiar with the precious gems — diamonds, sapphires, rubies and emeralds — there are hundreds more semiprecious gemstones, according to the International Gem Society. And sometimes even organic materials that are made into jewelry (like pearls) are considered gemstones.

Many gemstones are crafted into jewelry using gold, a soft, malleable element. Although gold is a relatively rare metal, scientists aren't sure exactly how much of it exists in the world — or how much is left to mine.

Think you're as brilliant as a multifaceted diamond? Start the quiz below, my ever-lovely jewels, to find out if you're stuck in an onyx night or if your sky is opalite.

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You'll rock this!

Discover more science quizzes

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If you walk into a grocery store, you'll likely see piles of fruits and vegetables waiting to be purchased. But these foods didn't always look this way; many were domesticated — that is, selectively grown for certain characteristics — over hundreds if not thousands of years to be large and extra tasty.

These eatables each arose in a unique environment. So, do you know where apples and pumpkins emerged? What about potatoes, cherries and lemons? Aromatic treats made from beans, like chocolate and coffee, were also cultivated by humans. Take our quiz to see if you can nail down the origin of 15 fruits, vegetables and beans.

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The human skeleton — our internal framework that includes bones and cartilage — evolved over millions of years. It comprises an axial skeleton, which consists of the skull and the spine, as well as an appendicular skeleton, which includes the shoulders, hips, arms and legs.

One of the main functions of the skeleton is to protect our squishy internal organs, but another important function is to help us move; bones act as levers with the assistance of muscles, tendons and ligaments.

Our jaws and teeth are also part of our skeleton, helping us eat and talk. From the top of our parietal bones to the bottom of our tiniest toe phalanges, our skeletons are a key part of our everyday lives.

How much do you know about your skeleton? Start our spine-tingling quiz below to find out.

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No guts, no glory!

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—Conspiracy theory quiz: Test your knowledge of unfounded beliefs, from flat Earth to lizard people

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Your heart pumps blood from your head to your toes, provides cells with fresh oxygen, and removes waste products. Located in the middle of your chest and tilted slightly to the left, your heart pushes out about 1.5 gallons (5.7 liters) of blood every minute to over 60,000 miles (97,000 kilometers) of blood vessels.

When things go wrong with the heart and circulatory system, the consequences can be dire. Cardiovascular disease is the leading cause of death for both men and women in the U.S., where about 1 in 3 deaths is attributable to heart disease. In the U.S. alone, one person dies every 34 seconds from cardiovascular disease, and heart disease costs the country over $400 billion annually.

The heart is undoubtedly one of the most important organs in the human body, and there's a lot to learn about it. So don't skip a beat, and take our quiz to test your knowledge of the heart.

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King Tutankhamun ruled over ancient Egypt during the New Kingdom, in the aftermath of his father — the revolutionary Akhenaten. He ruled from childhood and died young, at around 18, earning him the modern nickname of the boy king. It seems he died suddenly and unexpectedly, so was hastily buried in a tomb jam-packed with treasures.

When his unlooted tomb was unearthed in 1922, the discovery captivated the world. Since then, King Tut's artifacts and mummy have been extensively studied. So, how much do you know about the 18th-dynasty pharaoh? Take our quiz to find out.

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—Ancient Egypt quiz: Test your smarts about pyramids, hieroglyphs and King Tut

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On Sept. 19, 1991, hikers were crossing a pass over the Ötztal valley in the Alps when they stumbled upon a human body that was partly exposed in the ice. The hikers alerted the authorities, who spent several days extracting the mummified corpse from the melting ice. When archaeologists finally got a look at it, they realized the mummy was not a missing 20th-century hiker but rather millennia-old human remains. The body of the middle-aged man who died around 3300 B.C. would become known as Ötzi or the Iceman who revealed what everyday life was like during the Copper Age.

Think you know a lot about Ötzi's Copper Age life and manner of death? Start the quiz below to find out if your knowledge of this famous mummy is solid or on thin ice.

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—Mummy quiz: Can you unwrap these ancient Egyptian mysteries?

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The human body is a powerful machine, and nothing exemplifies it more than sports and athletic achievements. Every year, athletes are getting faster, stronger and fitter, smashing long-established world records and raising the bar for generations to come. They are the definition of 'impossible is nothing' and a constant source of inspiration for millions of people worldwide.

Our question is, how much do you know about some of the greatest athletic achievements of all time? This quiz will help you find out whether your knowledge of sports records is up to scratch.

Below, you will find 10 questions related to different aspects of human strength and endurance. Let's see if you can name the fastest 100-meter dash, the longest breath hold underwater or the highest jump ever recorded. We know it is a lot of numbers and stats to go through but hints are available if you click the yellow button!

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Julius Caesar decided to invade Britain in 55 B.C. as a strategic military move, since he thought the Britons were conspiring with the Gauls against him. But he hit immediate resistance when landing in what is now England and failed to conquer any territory.

For the next century, Roman emperors tried unsuccessfully to make inroads into Britain. But in A.D. 43, Emperor Claudius launched a series of campaigns that resulted in the Romans establishing a capital at Camulodunum, now called Colchester.

The Romans suppressed a series of uprisings led by Celtic chiefs and, under Emperor Hadrian, built a defensible wall across the new northern frontier of the Roman Empire in A.D. 122. Even though Caesar got tossed out of England, the country is full of evidence the Romans ruled the province of Britannia for nearly four centuries.

Think you're an encyclopedia of Britannia? Start the quiz below to find out if you're a font of Roman knowledge or if you'll end up in ruins.

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Spiders: they're creepy, they're crawly and they’re undeniably fascinating. With around 50,000 known species worldwide, spiders have adapted to nearly every environment on Earth; we're talking deserts, caves, rainforests and even underwater. Whether they send a shiver down your spine or make your senses tingle, there's more to these eight-legged enigmas than meets the eye.

As scary as they can appear — often starring in horror movies and our nightmares — most spiders tend to avoid humans and would much rather scurry away than attack. In fact, spiders are some of nature's most skilled engineers, survivalists and hunters. From questionable courtship rituals to elite hunting strategies, we can't help but be amazed by these adaptable arthropods.

So, are you a true arach-nerd or will you get caught in a web of lies? Brave this quiz to test your spider smarts, if you dare.

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Do you think you've got decent science knowledge? It's time to put your gray matter to the test with our weekly, free science crossword puzzle.

We've spent hours carefully writing our puzzles to make sure they are challenging but accessible to people of all ages and scientific backgrounds, with answers ranging from unusual animals and ancient rulers, to fundamental theories and Nobel Prize-winning scientists. Don't expect it to be easy, but it will be fun!

All you have to do to play is register once and then you should be logged in for next time, and if you need a hint tap the question mark next to the clue to reveal a letter.

Be sure to share this with your friends, and if you want more fun and games, you can also try out one of our amazing science quizzes on more than 50 different topics.

Note: Our crosswords are currently best experienced on desktop.

Previous science crosswords

Want to try your luck with our previous crossword puzzles? The most recent ones can be found below, but you can access the full list of science crosswords here.

—#54: Egyptian pharaoh who died at 18 — 6 down

—#53: Ancient supercontinent — 11 across

—#52: The moon's other name — 2 down

—#51: Largest rodent on Earth — 4 down

—#50: Longest-serving president in US history — 1 across

The historical area called Mesopotamia, meaning "land between two rivers" in ancient Greek, refers broadly to the territory between the Tigris and Euphrates rivers. Mesopotamia encompassed what today are Iraq, eastern Syria, southeast Turkey, and parts of Iran and Kuwait. Beginning around 10,000 B.C., Mesopotamia became a hotbed of cultural developments, including agriculture, mathematics and the wheel. So it's no surprise that some of the world's earliest empires also arose here.

The Sumerian civilization began around 5500 B.C. in south-central Iraq, boasting important city-states such as Ur. The Akkadian Empire eclipsed Sumer around 2300 B.C., dramatically expanding the old borders — and drafting numerous salacious riddles. And then around 800 B.C., the middling city of Assur capitalized on free trade and became a significant power at the heart of the Assyrian Empire. All of these cultures left their mark on the region.

Is your knowledge of the ancient Near East as solid as a cuneiform tablet, or will this "cradle of civilization" test make you cry like a "Baby"lon? Start the quiz below to find out.

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—Ancient Maya quiz: What do you know about the civilization that built pyramids across Mesoamerica?

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The ancient Celts were a collection of tribes that roamed Europe for centuries, reaching as far east as what is now Turkey. Best known from the writings of Julius Caesar, who recorded information on his war with the Gauls — a tribe that lived around modern-day France — the Celts are often depicted as violent, fierce and scruffy. But this picture has been filtered through ancient Roman and Greek authors who knew little about these groups, which spoke different languages and had complex cultures.

There's also no universal definition of who counted as an ancient Celt. Some historians count only continental tribes as Celtic, while others view the Brittonic-speaking tribes in the British Isles, such as the Durotriges and Iceni, as Celts as well. The association of the Celts with only the British Isles — and with Ireland in particular — that often persists today is a Renaissance invention.

Are you up to date on your knowledge of the Celts? Take our quiz to find out.

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—Ancient Maya quiz: What do you know about the civilization that built pyramids across Mesoamerica?

The ancient Maya civilization stretched throughout Central America and lasted for nearly three millennia. Although never unified into one massive empire, the Maya controlled dozens of city-states, also known as "polities," which arose when people settled in permanent villages and began to cultivate maize. The ancient Maya are well known for their pyramids and for their series of calendars — one of which convinced many people that the world would end in an apocalypse on Dec. 21, 2012. While the ancient political system collapsed between A.D. 800 and 1000, the society did not. Today, more than 7 million Maya live in their original homelands and beyond.

Are you up to date on recent research on the ancient Maya? Take our quiz to find out.

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Birds have run, swum and flown around Earth since the dinosaur age, and they've hunted for food and raised their fuzzy chicks for generation after generation.

These feathery creatures now live on every continent, sometimes migrating thousands of miles to seasonal destinations. You can often hear their birdsong as they trill, chirp and whistle, thanks to the syrinx, a vocal organ that has two independent sound sources, unlike the single one found in humans.

Science has proved that some bird species are extraordinarily smart. For example, crows understand the concept of zero, and an African gray parrot named Alex had a vocabulary of over 100 words. Birds can also dance to a beat and use tools.

But how much do you actually know about birds? Take our quiz to find out.

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• Big cats quiz: Can you get the lion's share of these questions right?
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Paws what you're doing, it's time for the ultimate cat quiz.

Cats are adorable. Fact! From their squishy "toe beans" to their swishy tails, they've made their way into our homes and our hearts. They're one of the world's most popular pets, but how much do we really know about our fluffy friends?

Our cuddly (and sometimes not so cuddly) companions have been intertwined with human lives for millennia: the ancient Egyptians were obsessed with cats, you've probably heard of the famous Schrödinger's cat thought experiment, and if you've been on the internet long enough, you'll have come across cat celebrities like the lovable Grumpy Cat and Lil BUB.

Yet, despite thousands of years together, there are many cat questions left unanswered. Why do they purr? What do their miaows and chattering actually mean? And who really domesticated who?

Take the quiz below to find out if you're the cat's whiskers or just kitten yourself. Only the cleverest of kitties will land on their feet in this quiz. Pspspsps… check out our big cats quiz too!

If you need a hint, click the yellow button. Good luck!

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—Animal quiz: Test yourself on these fun animal trivia questions

—Big cats quiz: Can you get the lion's share of these questions right?

—Mammoth quiz: Test your knowledge of the ice age beasts

"Big cats" are living members of the genus Panthera. There are five big cat species, including lions and tigers.

They are found on most continents — including Africa, Asia and South America — and in various types of environment, such as savannas and jungles. Like all felids (cats), they are carnivorous.

Big cats often sit at the top of the food chain, which means they have a large impact on ecosystems, mostly resulting from predation, which helps to keep animal populations in check. To preserve energy, big cats have evolved to lie in wait for their prey before pouncing to make a kill.

Big cats are some of the most charismatic creatures on Earth, but how much do you know about these fierce predators? Put your head in the lion's mouth and take our quiz to find out.

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Hakuna matata!

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The ancient Romans were unaware of the massive danger posed by a volcano in their midst, so when Mount Vesuvius erupted in A.D. 79, thousands of people scrambled to escape several small seaside towns.

As the largest town closest to the volcano, Pompeii suffered the most damage and was essentially wiped off the map. It was rediscovered in the late 16th century, but it wasn't until 1763 that the city was conclusively identified as Pompeii, when the Latin inscription rei publicae Pompeianorum — the state of Pompeii — was discovered at the site. Archaeological excavations at Pompeii continue to this day, with experts finding groundbreaking new information about the people who lived there in the first century and their tragic ends.

Are you up to date on recent research on Pompeii? Time to carpe diem and veni, vidi, vici our quiz!

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—Stone Age quiz: What do you know about the Paleolithic, Mesolithic and Neolithic?

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The Stone Age was a prehistoric period that lasted more than 3 million years, from the point when human ancestors began using stone tools until the time we invented metalworking.

Archaeologists often break up this lengthy time span into three periods — the Paleolithic (3.3 million to 12,000 years ago), the Mesolithic (12,000 to 10,000 years ago), and the Neolithic (10,000 to 4,000 years ago) — although there is regional variation in dates.

While the Paleolithic period involved a nomadic lifestyle and the invention of stone tools, the Neolithic period was ushered in with the development of agriculture and settled communities.

Are you up to date on recent research on the Stone Age? Don't take your knowledge for granite — try your best to rock our gneiss little quiz.

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. May the quartz be with you!

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The Vikings loom large in European history thanks to their impressive seafaring skills and penchant for raiding. For around three centuries, Vikings pillaged and plundered their way around the North Atlantic Ocean, as well as parts of Africa, Eastern Europe and Russia. But historians are still not sure exactly why the Vikings voyaged so far and wide, offering explanations from innovations in sailing technology to trade, and even to lonely Viking men who wanted to secure brides and concubines.

If you think you know a lot about these pillaging people, can you crack our Norse code? Or will you go berserker trying?

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. It's time to make like the Vikings and charge ahead!

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We spend a large portion of our lives sleeping. That might seem like an evolutionary disadvantage, given sleep leaves us immobile and potentially vulnerable to attacks for hours on end — but evidence suggests we have many key physiological functions tied to sleep, and disruptions in sleep are linked to a wide range of health problems, including a higher risk of death.

What's more, as we sleep, we often dream. In this way, sleep unlocks an experience that we can't access during our waking hours.

In the quiz below, test your knowledge of the science of sleeping, as well as the dreams that unfold during sleep. Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button, and let us know your score in the comments.

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Snakes are limbless reptiles that are found on every continent except Antarctica, having adapted to a wide range of environments. They are amazing creatures with some jaw-dropping abilities, and they play a critical role in many food webs.

While most snakes are completely harmless, some inspire dread for good reason. Globally, 5.4 million people are bitten by snakes every year, resulting in between 80,000 and 140,000 annual deaths, according to the World Health Organization.

Of the 4,000 snake species in the world, only about 600 are venomous, though not all of those pose a threat to humans. That doesn't stop some people from developing ophidiophobia, or an intense fear of snakes, which is one of the most common phobias.

Without further ado, how much do you know about snakes?

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button, and let us know your score in the comments. Good luck!

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Behold, the human brain: Often compared to a computer, the body's most complex organ operates using a code of electrical and chemical signals. These signals transmit through wires, nodes and networks to process and store information.

Through these operations, the brain directs our unconscious bodily functions, such as our appetites and levels of wakefulness, as well as "higher order" cognitive abilities — solving problems, generating ideas, planning for the future. The brain has inherent plasticity, meaning it dynamically responds to novel information and literally restructures itself to accommodate new memories and new interpretations of the world around us.

Scientists are still unraveling the brain's inner workings, but over the decades, they've learned quite a lot about what makes the organ tick. Check out the quiz below to test your knowledge of the human brain and its many unique features.

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button, and let us know your score in the comments.

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Half a century ago, Chinese farmers stumbled upon an enormous underground mausoleum full of life-size clay people, animals and military equipment. Archaeologists think that the tomb may be an entire replica of the Chinese city of Xi'an built to honor the first emperor of China, Qin Shi Huang, who died in 210 B.C.

Excavations within the tomb over the past five decades have continued to reveal more chambers full of statues, weapons, and skeletons of both humans and animals. But the actual grave of Emperor Qin, who conquered six warring states and unified China, has remained untouched for over two millennia.

What else do you know about the Terracotta Army, which the Chinese often call the "eighth wonder of the world"? Time to marshal your knowledge of dynastic China and take our quiz!

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Keep calm and soldier on!

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Is there anybody out there? Are we really alone in the universe, or are aliens just patiently waiting for us to become advanced enough to be worth speaking to?

There are so many mysteries about who or what might live among the stars, and whether they are advanced planet-hopping civilizations or microbes quietly doing what microbes do on a nearby moon. But some questions are easier to answer.

This extraterrestrial quiz is your chance to show whether you know the facts from the fiction about otherworldly entities, or if it's all alien to you. Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button, and let us know your score in the comments.

Related: 32 strange places scientists are looking for aliens

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As one of the most famous scientists of the 20th century, Albert Einstein has become synonymous with genius. He taught himself geometry and calculus while living in Germany in his teens before training in Switzerland to become a math teacher. Unable to find a teaching position, Einstein bounced around until he completed a doctorate in physics in 1905 and began publishing groundbreaking scientific papers that ultimately changed the world.

But Einstein had other interests that are less well known — he was a staunch pacifist, invented an early refrigerator and called himself a "deeply religious non-believer." What do you know about the man, the myth, the genius Einstein? Time to take a quantum leap, because this quiz will test what you know about the famous physicist!

Related: 32 fun and random facts about Albert Einstein

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. Consider the gravity of the situation and be sure to ace this quiz at the speed of light!

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On March 14 mathematicians everywhere enjoy a slice of pie as they recite the digits of math's most famous constant. Pi, defined as the ratio between the circumference of a circle and its diameter, is what's known as an irrational number. Despite its ubiquity, not only across math but also in fields as varied as medicine, space exploration, and geography, this number can't be written as a fraction and is instead expressed as a decimal with digits going on forever.

For most of us, this fundamental constant is usually approximated to 3.14, but math enthusiasts are constantly trying to push the boundaries and calculate pi to as many digits as possible.

Pi Day is celebrated on March 14th (3/14 — see what they did there?) and is the perfect occasion for mathematicians to celebrate their favourite number. Sharing math puzzles, strange pi facts, and new records is all part of the fun. So to celebrate Pi Day — or just to celebrate Pi — here's a quick quiz to test your knowledge. If you need a clue, press the yellow button.

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Elephants are Earth's largest land mammals, and with their trunks, tusks and giant ears, they're among the most recognizable and iconic animals alive today.

Known for their extraordinary intelligence, elephants are recognized as some of the world's most empathic creatures, working together in close-knit communities to help one another. They are even known to grieve and bury their dead.

But how much do you know about these giants? Take our quiz to find out. If you need a hint, tap the lightbulb in the top right corner.

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The U.S. has 63 national parks, each boasting stunning landscapes, impressive geological features and often rare ecosystems.

National parks are areas of land protected by the federal government and managed by the National Park Service (NPS). They are open to the general public, and figures show that in 2023, roughly 90 million people visited these parks.

The first national park in the U.S., which was also the first national park in the world, was established by an act of Congress in 1872. State parks and nature reserves existed before then, but the new national park was bigger and considered by the federal government to be one of America's crown jewels.

Over the next century, successive U.S. governments designated dozens of additional national parks. Many of these parks were created on confiscated Indigenous land, and there are calls today to hand it to the people who originally owned, lived and worked on it.

How many national parks can you name? You'll have 30 minutes to complete this quiz. Note that you don't need to write "national park" after each name.

Make sure you log in to add your name to the leaderboard — and if you need a hint, tap the yellow button.

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The ancient Egyptians were not the first culture to mummify their dead, but they practically perfected the practice by wrapping and preserving millions of people and animals throughout the centuries. The earliest Egyptian mummies discovered by archaeologists date to around 3500 B.C., well before the Great Pyramid of Giza was built.

Mummification was a sacred funeral rite for the ancient Egyptians, who believed that the body of the deceased needed to be preserved so that their spiritual essence could transcend into the next world. Ancient Egyptians believed the heart was the seat of the person's essence, so it was always left inside a mummy. But the process of mummification was complicated and costly, so it was typically reserved for elite members of society.

The ancient Egyptians practiced mummification for thousands of years, but it eventually faded out in Roman times because of the advent of Christianity.

What do you know about the history and practice of mummification in ancient Egypt? Unwrap your skills, because this quiz will test what you know about pyramid schemes — no bones about it!

Remember to log in to put your name on the leaderboard; hints are available if you click the yellow button. We hope you unravel these mysteries!

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For more than 60 years, humanity has been pushing the limits of ingenuity, engineering and imagination by launching people into space — and keeping them safe in the "final frontier" for prolonged periods.

During this time, we have hit major milestones, such as landing on the moon, and seen incredible individuals set some mind-blowing records. And in recent years, the advent of private space companies, like SpaceX and Blue Origin, have opened up space to a whole new group of explorers and set us on a course to venture deeper out into the solar system.

But how well do you know our spaceflight history?

This quiz of 15 questions will test your knowledge of our first steps towards the stars and the incredible astronauts who helped take them. And remember to log in to put your name on the leaderboard and click the yellow button if you need a hint!

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—Solar system quiz: How well do you know our cosmic neighborhood?

The sun is much more than a bright light in the sky. It's a giant ball of burning gas that holds our cosmic neighborhood together and without it, there would be no life on Earth.

Our home star is also much more dynamic than most people think. It constantly spits out streams of radiation into the solar system and cycles through periods of increased activity that can litter its surface with dark spots and bring potentially damaging solar storms raining down on our planet, triggering vibrant aurora displays.

We are also constantly learning new things about the sun, such as the true origin of its magnetic field and how to predict when it will violently erupt.

So how much do you know about the sun? Let's test your knowledge of our local star with these 15 questions. And remember to log in to put your name on the leaderboard and click the yellow button if you need a hint!

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