250 Surprising Facts: Animals, Science, Space, History & Everyday Life

Babies are born with around 270 to 300 bones. Many of them fuse together as they grow, leaving adults with 206.

The liver is the only internal organ that can regrow itself. It can return to nearly full size even after a large part of it has been removed.

The femur, or thigh bone, is the longest and strongest bone in the human body.

Tooth enamel is the hardest substance in your body, but it cannot repair itself because it contains no living cells.

About a quarter of your bones are in your feet: 26 in each foot, or 52 of the body's 206 bones.

Skin is the body's largest organ. An adult's skin covers roughly 1.5 to 2 square metres.

Fingernails grow about three times faster than toenails.

Most people blink around 15 to 20 times a minute, which adds up to more than 14,000 blinks in a waking day.

Your heart beats about 100,000 times a day and more than 2.5 billion times in an average lifetime.

Your blood vessels could wrap around the Earth more than twice

If you laid out every artery, vein and tiny capillary in an adult's body end to end, they would stretch for roughly 100,000 kilometres. That is about two and a half times around the planet at the equator. Most of that length comes from capillaries, which are so thin that red blood cells have to pass through them in single file.

It's impossible to hum while holding your nose closed, because humming needs air to escape through your nose.

A 2018 study found that a tightly knotted necktie can reduce blood flow to the brain by up to 7.5%.

About 10% of people in the world are left-handed.

The human eye can tell apart roughly a million different colours.

Your body sheds tens of thousands of dead skin cells every minute.

The smallest bone in your body is the stapes in your middle ear, about 3 millimetres long.

Humans glow faintly in the dark. A 2009 study found the body gives off visible light, but it is about 1,000 times too weak for our eyes to see.

Scientists estimate the adult human body contains around 37 trillion cells.

A red blood cell lives for about 120 days before it is recycled.

Penicillin was first called "mould juice"

In 1928, Scottish scientist Alexander Fleming came back from a holiday to find mould growing on one of his lab dishes, and the bacteria around it had died. Before naming it penicillin, he called the bacteria-killing liquid "mould juice". Other scientists later found a way to mass-produce it during the Second World War. It became the first widely used antibiotic and has saved millions of lives.

In the 1660s, Isaac Newton split sunlight into colours with a prism. He later arranged those colours in a circle, creating one of the first colour wheels.

In the 1800s, some people swallowed small amounts of arsenic, a deadly poison, in the belief that it would improve their skin.

A Venus flytrap only snaps shut when an insect touches its trigger hairs twice within about 20 seconds. This stops it wasting energy on raindrops.

Water expands by about 9% when it freezes, which is why ice floats.

Diamonds and the graphite in pencils are made of exactly the same thing: pure carbon, arranged differently.

Sound travels about four times faster through water than through air.

Bananas are slightly radioactive because they contain potassium, but you would need to eat millions at once for it to be harmful.

Your fingerprints form before you are born, and even identical twins have different ones.

The adult human body is about 60% water.

Your stomach lining renews itself every few days

Your stomach makes hydrochloric acid strong enough to break down tough foods and kill many germs. To stop the stomach from digesting itself, a thick layer of mucus coats its walls, and the cells of the inner lining are constantly replaced. Many of them last only a few days before fresh ones take over.

You are slightly taller in the morning than at night, because the discs in your spine compress as you move around during the day.

Babies are born without bony kneecaps. Their kneecaps start out as soft cartilage and harden over the first few years.

Your nose and sinuses produce roughly a litre of mucus every day. Most of it is swallowed without you noticing.

You will spend about a third of your life asleep.

Yawning is contagious, and seeing, hearing or even reading about a yawn can set you off.

Botanically speaking, bananas are berries but strawberries are not.

The tiny specks on a strawberry are not exactly seeds. Each one is a separate small fruit called an achene, with a seed inside.

Avocados are fruits. Botanists classify them as large berries with a single seed.

Tomatoes are fruits too, but in 1893 the US Supreme Court ruled that they should be taxed as vegetables.

Lightning is about five times hotter than the surface of the Sun

A bolt of lightning can heat the air around it to roughly 30,000°C in a fraction of a second. The surface of the Sun is about 5,500°C. That sudden heat makes the air expand explosively, which is the sound we hear as thunder. Across the planet, lightning strikes around 40 to 50 times every second.

Peanuts are not true nuts. They are legumes, related to beans and peas, and they grow underground.

Almonds, peaches, cherries and plums all belong to the same plant family.

Ripe bananas glow blue under ultraviolet light.

A watermelon is about 92% water.

A pineapple plant takes around two years to produce a single pineapple.

In the 1830s, ketchup was sold in the United States as a medicine, in the form of "tomato pills".

Honey can stay edible for an extremely long time, because it is low in water and naturally acidic, which stops germs from growing.

Your sense of smell is closely linked to memory, which is why a scent can instantly bring back an old moment.

Humans are born with a strong grasping reflex, and newborns can grip a finger tightly enough to briefly hold up their own weight.

One man had the hiccups for 68 years

In 1922, an American farmer named Charles Osborne started hiccupping while lifting a heavy pig, and he didn't stop for 68 years. He hiccupped an estimated 430 million times before they finally stopped in 1990, about a year before he died. He holds the record for the longest attack of hiccups, yet he still married twice and raised eight children.