Octopuses have three hearts and blue blood.

Two hearts pump blood through the gills and one pumps it around the body. Their blood uses copper-based hemocyanin instead of iron-based hemoglobin, which makes it blue.

A group of flamingos is called a flamboyance.

English has many colorful collective nouns, like a parliament of owls, a crash of rhinos, and a murder of crows.

Wombats produce cube-shaped poop.

The walls of a wombat's intestine stretch unevenly, which shapes droppings into cubes. Wombats stack them on rocks and logs to mark their territory.

A shrimp's heart is in its head.

Most of a shrimp's vital organs sit in its cephalothorax, the fused head and chest section of its body.

Koalas have fingerprints that are very hard to tell apart from human ones.

Koala fingerprints have loops and whorls so similar to ours that even under a microscope they can be confused.

Elephants can recognize themselves in a mirror.

Asian elephants passed the mirror self-recognition test in 2006, a skill also shown by great apes, dolphins, and magpies.

Bottlenose dolphins call each other by name.

Each dolphin develops a signature whistle, and others copy that whistle to get its attention.

Owls can turn their heads about 270 degrees.

Owls have 14 neck vertebrae, twice as many as humans, plus special blood vessels that keep blood flowing when they twist.

Hummingbirds are the only birds that can truly fly backward.

Their shoulder joints let their wings rotate in a figure-eight pattern, so they can hover and fly in any direction.

Cats can't taste sweet things.

Cats lack a working version of the gene for the sweet taste receptor, so sugar tastes like nothing to them.

Butterflies taste with their feet.

Taste receptors on their feet tell female butterflies whether a leaf is the right plant to lay eggs on.

Crows can recognize and remember individual human faces.

In University of Washington experiments, crows scolded people wearing a mask they associated with danger for years afterward.

Polar bears have black skin under their fur.

Their fur is made of hollow, see-through hairs that scatter light and look white. The dark skin underneath absorbs heat.

Honeybees dance to tell each other where flowers are.

In the waggle dance, the angle and length of the dance show the direction and distance of food. Karl von Frisch shared a Nobel Prize in 1973 for decoding it.

Giraffes have the same number of neck bones as humans.

Both have seven neck vertebrae. A giraffe's are just much longer, each up to about 25 cm (10 in).

Sea otters sometimes hold paws while they sleep.

Floating otters hold paws or wrap themselves in kelp so they don't drift apart from their group.

A day on Venus is longer than its year.

Venus takes about 243 Earth days to spin once, but only about 225 Earth days to orbit the Sun.

On Venus, the Sun rises in the west.

Venus spins backward compared with most planets, so the Sun crosses its sky in the opposite direction.

Some neutron stars spin more than 700 times a second.

The fastest known pulsar, PSR J1748-2446ad, rotates about 716 times per second.

A teaspoon of neutron star would weigh about a billion tons on Earth.

Neutron stars pack more mass than the Sun into a ball about 20 km (12 miles) across.

Footprints left on the Moon could last for millions of years.

The Moon has no wind or rain to erase them. Only tiny meteorite impacts slowly wear them down.

Jupiter has the shortest day of any planet.

Jupiter spins once every 9 hours and 56 minutes, despite being the largest planet.

Saturn is less dense than water.

Saturn's average density is about 0.69 grams per cubic centimeter, lower than water's 1. It has no surface to float on, though.

Sunsets on Mars are blue.

Fine Martian dust scatters blue light forward, so the sky glows blue around the setting Sun.

Sunlight takes about 8 minutes and 20 seconds to reach Earth.

The Sun is about 150 million km (93 million miles) away, and light travels about 300,000 km per second.

About 1.3 million Earths could fit inside the Sun.

The Sun's diameter is about 109 times Earth's, so its volume is roughly 1.3 million times larger.

Olympus Mons on Mars is about two and a half times taller than Mount Everest.

The volcano rises about 25 km (16 miles) and is about as wide as the state of Arizona.

Astronauts on the International Space Station see about 16 sunrises a day.

The station circles Earth about every 90 minutes at roughly 28,000 km/h (17,500 mph).

Astronauts can grow up to 3 percent taller in space.

Without gravity compressing it, the spine stretches out. They shrink back after returning to Earth.

Uranus spins on its side.

Its axis is tilted about 98 degrees, probably because of a giant collision long ago, so it rolls around the Sun like a ball.

Neptune completed its first orbit since its discovery in 2011.

A year on Neptune lasts about 165 Earth years, and it was discovered in 1846.

The Moon is drifting away from Earth by about 3.8 cm a year.

Lasers bounced off mirrors left by Apollo astronauts measure the distance precisely. It's about as fast as your fingernails grow.

Bananas are slightly radioactive.

They contain potassium, and a tiny fraction of natural potassium is radioactive potassium-40. You'd need to eat millions at once for it to be harmful.

Lightning can heat the air to about five times hotter than the Sun's surface.

A lightning bolt can heat the air around it to roughly 27,000 °C (50,000 °F) for a split second.

Sound travels more than four times faster in water than in air.

Sound moves about 1,480 meters per second in water versus about 343 in air, because water molecules are packed closer together.

Gallium is a metal that can melt in your hand.

Gallium melts at about 30 °C (86 °F), below body temperature.

Ice floats because water expands when it freezes.

Frozen water takes up about 9 percent more space, making ice less dense than liquid water. That's why lakes freeze from the top down.

Diamonds and pencil lead are made of the same element.

Both diamond and graphite are pure carbon. The difference is how the carbon atoms are arranged.

Helium was discovered in the Sun before it was found on Earth.

Astronomers spotted its signature in sunlight during an 1868 eclipse. It wasn't isolated on Earth until 1895.

Water can boil and freeze at the same time.

At its triple point, 0.01 °C and very low pressure, water exists as solid, liquid, and gas all at once.

Nothing can be colder than absolute zero.

Absolute zero, −273.15 °C (−459.67 °F), is the temperature at which particles have the least possible energy.

Pure water is a poor conductor of electricity.

It's the minerals and salts dissolved in everyday water that let electricity flow through it.

Rainbows are actually full circles.

From the ground, the horizon hides the lower half. From a plane, you can sometimes see the whole ring.

Earth's inner core is about as hot as the surface of the Sun.

The inner core is estimated at around 5,000 to 6,000 °C, similar to the Sun's surface temperature of about 5,500 °C.

Liquid oxygen is pale blue.

Oxygen molecules absorb a little red light, which gives liquid and solid oxygen a light blue color.

An average fluffy cumulus cloud weighs about 500 tonnes.

A typical cumulus cloud holds about half a gram of water in each cubic meter, spread across a billion cubic meters of air.

Sealed honey can last for decades or even centuries.

Honey is low in water and naturally acidic, so bacteria and mold can't grow in it.

Your body contains enough iron to make a small nail.

An adult body holds about 3 to 4 grams of iron, mostly in the hemoglobin that carries oxygen in red blood cells.

Babies have more bones than adults.

Babies are born with around 270 to 300 bones and cartilage pieces. Many fuse together, leaving adults with 206.

Your skin is your largest organ.

An adult's skin covers about 2 square meters (22 square feet) and weighs several kilograms.

You're about 1 cm taller in the morning than at night.

During the day, gravity squeezes the cushioning discs in your spine. They expand again while you sleep.

The smallest bone in your body is in your ear.

The stapes, or stirrup bone, is about 3 mm long and helps carry sound vibrations to your inner ear.

Your heart beats about 100,000 times a day.

At around 70 beats a minute, that adds up to more than 2.5 billion beats in an average lifetime.

Your brain uses about 20 percent of your body's energy.

The brain is only about 2 percent of your body weight, but it burns a fifth of the energy you use at rest.

Your small intestine is about 6 meters (20 feet) long.

It's folded up in your belly, and tiny finger-like villi give it a surface area of roughly 30 square meters.

Babies are born with kneecaps made of cartilage.

Their kneecaps slowly turn to bone between about ages 2 and 6.

Tooth enamel is the hardest substance in the human body.

Enamel is about 96 percent mineral, but it can't regrow once it's damaged.

Your left lung is smaller than your right lung.

The left lung has two lobes instead of three, making room for your heart.

Your stomach lining replaces itself every few days.

The cells lining your stomach are renewed every three to five days, protecting it from its own acid.

Fingernails grow two to three times faster than toenails.

Fingernails grow about 3.5 mm a month. Nails on your dominant hand tend to grow a little faster.

The human body gives off a faint glow.

Japanese researchers found in 2009 that people emit visible light, but it's about 1,000 times too weak for our eyes to see.

You blink around 15 to 20 times a minute.

Each blink spreads tears across your eye to keep it clean and moist. You blink less when staring at a screen.

Oxford University is older than the Aztec Empire.

Teaching at Oxford was underway by 1096. The Aztecs founded their capital, Tenochtitlan, in 1325.

The shortest war in history lasted under an hour.

The Anglo-Zanzibar War of August 27, 1896, ended after about 38 to 45 minutes.

Cleopatra lived closer in time to the Moon landing than to the building of the Great Pyramid.

The Great Pyramid was built around 2560 BC. Cleopatra died in 30 BC, about 2,000 years before Apollo 11 landed in 1969.

Woolly mammoths were still alive when the Great Pyramid was built.

A small population survived on Russia's Wrangel Island until about 4,000 years ago.

Some ancient Roman concrete has survived in seawater for 2,000 years.

Roman builders mixed lime with volcanic ash, which reacts with seawater to form new minerals that strengthen it over time.

Vikings reached North America about 500 years before Columbus.

Tree rings from wood cut at L'Anse aux Meadows in Newfoundland date Norse activity there to the year 1021.

The Eiffel Tower was supposed to be temporary.

It was built for the 1889 World's Fair with a 20-year permit. It survived partly because it was useful as a radio antenna.

The oldest surviving photograph needed an exposure of hours or even days.

Joseph Nicéphore Niépce made "View from the Window at Le Gras" around 1826 or 1827.

The Statue of Liberty used to be a shiny copper-brown color.

Its copper skin slowly reacted with the air and turned green over about 30 years after it was unveiled in 1886.

The Hundred Years' War lasted 116 years.

The conflict between England and France ran from 1337 to 1453, with long breaks in the fighting.

In 1752, Britain and its colonies skipped 11 days.

When they switched to the Gregorian calendar, September 2 was followed directly by September 14.

The University of al-Qarawiyyin in Morocco was founded in 859.

Founded by Fatima al-Fihri in Fez, it is often called the oldest existing university in the world.

Nintendo was founded in 1889 as a playing card company.

It started out making hanafuda, traditional Japanese playing cards, long before video games existed.

Ketchup was sold as medicine in the 1830s.

An American doctor, John Cook Bennett, promoted tomato ketchup as a cure for indigestion, and it was sold in pill form.

Canada has more lakes than any other country.

Canada is home to more than half of all the world's lakes.

Africa is the only continent in all four hemispheres.

Both the equator and the prime meridian cross Africa, so it sits in the north, south, east, and west.

Russia spans 11 time zones.

From Kaliningrad in the west to Kamchatka in the far east, Russia is about 9,000 km (5,600 miles) wide.

Antarctica is the largest desert on Earth.

A desert is defined by low precipitation, not heat. Antarctica gets very little snow or rain across about 14 million square km.

Australia is wider than the Moon.

Australia is about 4,000 km (2,500 miles) from east to west. The Moon is about 3,475 km (2,160 miles) across.

Alaska is the northernmost, westernmost, and easternmost US state.

Alaska's Aleutian Islands cross the 180th meridian, so some of them lie in the Eastern Hemisphere.

The shore of the Dead Sea is the lowest land on Earth.

It lies about 430 meters (1,410 feet) below sea level, and the level keeps dropping each year.

Mount Everest is still getting taller.

The collision of the Indian and Eurasian plates pushes the Himalayas up by a few millimeters a year.

Vatican City is the world's smallest country.

It covers about 0.44 square km (110 acres), smaller than many city parks.

Lake Baikal holds about a fifth of the world's unfrozen fresh surface water.

The Siberian lake is also the world's deepest, at about 1,640 meters (5,390 feet), and one of the oldest, at over 25 million years.

The Pacific Ocean is bigger than all of Earth's land put together.

The Pacific covers about 165 million square km, while all land totals about 149 million.

About 6 in 10 people on Earth live in Asia.

Asia has around 4.8 billion people, including the two most populous countries, India and China.

Indonesia is made up of more than 17,000 islands.

Only around 6,000 of them are inhabited.

The nearest people to Point Nemo are often astronauts.

Point Nemo in the South Pacific is about 2,700 km (1,670 miles) from the nearest land. The International Space Station orbits only about 400 km overhead.

Bananas are berries, but strawberries aren't.

Botanically, a berry develops from one flower with one ovary. Strawberries form from a flower with many ovaries, and their "seeds" are actually tiny fruits.

The world's tallest known tree is about 116 meters (380 feet) tall.

Hyperion, a coast redwood in California, was found in 2006. Its exact location is kept secret to protect it.

Some bamboo can grow almost a meter in a single day.

Certain species have been measured growing up to 91 cm (35 inches) in 24 hours.

A bristlecone pine named Methuselah is more than 4,800 years old.

It grows in California's White Mountains and was already old when the Great Pyramid was built.

A single aspen grove in Utah is one living organism.

Pando is one clone of about 47,000 stems connected by a shared root system, and weighs around 6,000 tonnes.

Young sunflowers follow the Sun, but grown-up ones don't.

Young plants turn east to west during the day and reset at night. Mature flowers stay facing east, which warms them and attracts more bees.

Mushrooms are more closely related to animals than to plants.

Fungi and animals share a common ancestor that split from the plant lineage over a billion years ago.

The corpse flower smells like rotting meat.

The titan arum uses the stench to attract carrion beetles and flies. Its giant bloom lasts only a day or two.

A Venus flytrap counts before it snaps shut.

The trap closes only if trigger hairs are touched twice within about 20 seconds, so raindrops don't fool it.

One of the largest living things on Earth is a fungus.

A honey fungus in Oregon's Blue Mountains spreads underground across nearly 10 square km (about 2,400 acres).

A strawberry has about 200 seeds on the outside.

Each "seed" is actually a tiny fruit called an achene, with a seed inside.

The deepest point in the ocean could swallow Mount Everest with room to spare.

The Challenger Deep in the Mariana Trench is about 10,900 meters (35,800 feet) deep, more than 2 km deeper than Everest is tall.

Blue whales are the largest animals known to have ever lived.

They grow up to about 30 meters (98 feet) long and can weigh more than 150 tonnes, bigger than any dinosaur.

A blue whale's heart weighs about 180 kg (400 pounds).

That's about the weight of two adult men. When a blue whale dives deep, its heart can slow to just two beats a minute.

Male seahorses give birth.

The female lays her eggs in the male's pouch, where he fertilizes and carries them until they hatch.

Jellyfish have been around for more than 500 million years.

They are older than dinosaurs, trees, and even sharks.

One jellyfish can turn back into a baby.

When stressed or injured, Turritopsis dohrnii can revert to its juvenile polyp stage and start its life over.

About half the oxygen we breathe comes from the ocean.

Tiny drifting plants called phytoplankton make it through photosynthesis.

Greenland sharks can live for at least 270 years.

Scientists used radiocarbon dating on their eyes in 2016. The oldest one studied may have been around 400 years old.

Sea stars have no brain and no blood.

They pump seawater through their bodies instead of blood and use a network of nerves instead of a brain.

The ocean holds about 97 percent of Earth's water.

Most of the rest is frozen in ice caps and glaciers, leaving less than 1 percent as fresh liquid water.

Coral reefs cover less than 1 percent of the ocean floor.

Yet they support about a quarter of all known marine species.

The Great Barrier Reef is the largest structure built by living things.

It stretches about 2,300 km (1,400 miles) along Australia's coast and can be seen from orbit.

A fish has been filmed more than 8,300 meters deep.

In 2022, scientists filmed a snailfish 8,336 meters down in the Izu-Ogasawara Trench off Japan.

The Bay of Fundy has the highest tides in the world.

The difference between high and low tide in this Canadian bay can reach about 16 meters (53 feet).

Sea turtles use Earth's magnetic field to find their way home.

Many females return to lay eggs on the same beach where they hatched decades earlier.

Peanuts aren't nuts.

Peanuts are legumes, like peas and beans, and they grow underground.

Early carrots were purple or yellow, not orange.

Orange carrots were developed later, and Dutch growers made them popular in the 1600s.

Avocados are berries.

Botanically, an avocado is a single-seeded berry.

Pineapples take about two years to grow.

Each plant usually produces just one pineapple at a time, after 18 to 24 months.

Apples float because they're about a quarter air.

That's why apple bobbing works.

Chocolate started out as a bitter drink.

People in Mesoamerica were drinking cacao more than 3,000 years ago, often with chili and without sugar.

Each cashew nut grows out of the bottom of a fruit.

The cashew apple is edible, and the nut hangs below it in a shell containing an irritating oil.

Potatoes were the first vegetable grown in space.

In 1995, potato plants were grown aboard the Space Shuttle Columbia.

Saffron is the world's most expensive spice by weight.

Each crocus flower makes just three threads, picked by hand. It takes over 100,000 flowers to make a kilogram.

Cucumbers are about 96 percent water.

That makes them one of the most water-rich foods you can eat.

White chocolate contains no cocoa solids.

It's made from cocoa butter, sugar, and milk, which is why it isn't brown.

Popcorn pops because of steam.

Water inside each kernel turns to steam, building pressure until the hull bursts and the starch puffs out.

Birds can't feel the heat of chili peppers.

Birds lack the pain receptor that reacts to capsaicin, so they eat chilies and spread the seeds.

A worker honeybee makes only about a twelfth of a teaspoon of honey in its whole life.

A single jar of honey takes the work of hundreds of bees visiting around 2 million flowers.

The dot over a lowercase i or j is called a tittle.

The word comes from the Latin titulus, meaning a small mark or inscription.

"Run" has more than 600 meanings in the Oxford English Dictionary.

It overtook "set" as the English word with the most senses.

"The quick brown fox jumps over the lazy dog" uses every letter of the alphabet.

A sentence that does this is called a pangram, and this one has long been used to test typewriters and fonts.

"Bookkeeper" has three double letters in a row.

Oo, kk, and ee appear back-to-back, as they also do in "bookkeeping".

The ampersand (&) was once treated as the 27th letter of the alphabet.

Its name comes from children reciting "and per se and" at the end of the ABCs. The symbol itself comes from the Latin word et.

"Goodbye" comes from "God be with ye."

The phrase shortened over centuries, with "good" replacing "God" by analogy with "good day".

Papua New Guinea has more languages than any other country.

About 840 languages are spoken there, more than 10 percent of all languages on Earth.

"Nice" used to mean foolish.

The word comes from the Latin nescius, meaning ignorant. Its meaning shifted over centuries to pleasant.

"Hangry" was added to the Oxford English Dictionary in 2018.

The blend of hungry and angry had been in use for decades before.

Shakespeare's works are the earliest known source for many English words.

Words such as "eyeball", "swagger", and "bedroom" first appear in writing in his plays.

The Hawaiian alphabet has just 13 letters.

It has five vowels and eight consonants, including the ʻokina, a glottal stop.

"Uncopyrightable" is one of the longest English words with no repeated letters.

All 15 of its letters are different.

E is the most common letter in English.

It makes up about 11 percent of the letters in a typical English dictionary.

Mandarin Chinese has the most native speakers, but English has the most speakers overall.

Counting second-language learners, around 1.5 billion people speak English.

The fax machine was invented before the telephone.

Alexander Bain patented an early fax design in 1843, 33 years before Alexander Graham Bell's telephone patent in 1876.

The first computer bug was a real bug.

In 1947, operators of the Harvard Mark II computer found a moth stuck in a relay and taped it into the logbook.

The first webcam watched a coffee pot.

In 1991, researchers at the University of Cambridge set up a camera so they could check the coffee pot without leaving their desks.

Bubble wrap was first sold as wallpaper.

Its inventors, Alfred Fielding and Marc Chavannes, created textured wallpaper in 1957. It later found success as packaging.

The first text message said "Merry Christmas."

Engineer Neil Papworth sent it from a computer to a phone in December 1992.

The microwave oven was discovered by accident.

In 1945, Percy Spencer noticed a chocolate bar melting in his pocket while he worked near a radar magnetron.

The first YouTube video was uploaded in April 2005.

"Me at the zoo" shows co-founder Jawed Karim at the San Diego Zoo and lasts 19 seconds.

The QWERTY keyboard layout dates back to the 1870s.

It was designed for early typewriters by Christopher Latham Sholes and has stuck around ever since.

The Apollo 11 guidance computer had about 4 KB of working memory.

That's far less than a modern calculator or smartwatch, yet it helped land people on the Moon in 1969.

Velcro was inspired by burrs stuck to a dog's fur.

Swiss engineer George de Mestral studied burrs under a microscope after a walk in 1941 and copied their tiny hooks.

The @ sign was chosen for email in 1971.

Ray Tomlinson sent the first network email and picked @ to separate the user's name from the computer's name.

Post-it Notes came from a glue that wasn't sticky enough.

3M scientist Spencer Silver made a weak, reusable adhesive in 1968. A colleague later used it to keep bookmarks in his hymn book.

The first computer mouse was made of wood.

Douglas Engelbart and Bill English built it in 1964, with two metal wheels underneath.

The Super Soaker was invented by a NASA engineer.

Lonnie Johnson came up with the idea in 1982 while experimenting with a heat pump design.

A well-shuffled deck of cards is almost certainly in an order never seen before.

There are about 8 × 10⁶⁷ ways to arrange 52 cards, far more than the number of shuffles in all of history.

In a room of just 23 people, there's a better than even chance two share a birthday.

This is the birthday paradox: 23 people make 253 possible pairs, which is why the odds are higher than they feel.

111,111,111 × 111,111,111 = 12,345,678,987,654,321.

Squaring numbers made of ones creates a palindrome that counts up and back down, up to nine ones.

A googol was named by a 9-year-old.

Mathematician Edward Kasner asked his nephew Milton Sirotta to name the number 1 followed by 100 zeros.

Pi has been calculated to more than 100 trillion digits.

Only about 40 digits are needed to calculate the circumference of the observable universe to the width of an atom.

"Forty" is the only number whose letters are in alphabetical order.

F, o, r, t, y appear in order in the alphabet. No other number spelled in English does this.

Every odd number spelled in English contains the letter e.

One, three, five, seven, and nine all contain an e, and every odd number ends in one of them.

Folding paper 42 times would, in theory, reach the Moon.

Each fold doubles the thickness. A 0.1 mm sheet folded 42 times would be about 440,000 km thick.

0.999... repeating equals exactly 1.

One way to see it: one third is 0.333..., and three thirds are 0.999..., which equals 1.

There are more possible chess games than atoms in the observable universe.

Claude Shannon estimated about 10¹²⁰ possible games, compared with about 10⁸⁰ atoms.

There are infinitely many prime numbers.

The Greek mathematician Euclid proved it around 300 BC.

Roman numerals have no symbol for zero.

The Romans had no need for zero as a placeholder. The modern zero came from India and spread through the Arab world.

Adding the numbers 1 to 100 gives 5,050.

Pair 1 with 100, 2 with 99, and so on: that's 50 pairs that each add up to 101.

Honeycombs are hexagons because it's the most efficient shape.

Hexagons divide a surface into equal cells using the least wall material. Mathematician Thomas Hales proved it in 1999.