Facts — True and Verifiable

Forty-two facts chosen to be surprising and checkable — each is grouped by topic and phrased so you can verify it yourself. Numbers are best public estimates; where experts disagree (river lengths, for instance) we say so. Today's single fact lives on the Knowledge hub.

Space

• A day on Venus is longer than its year: it spins once every 243 Earth days while orbiting the Sun in 225.

• Neutron stars are so dense that a sugar-cube-sized piece of one would weigh about a billion tonnes on Earth.

• Saturn's average density is lower than water's — in a big enough ocean, the planet would float.

• Sunlight takes about 8 minutes 20 seconds to reach Earth, but only about 4 seconds to reach Jupiter.

• There are more trees on Earth (about 3 trillion) than stars in the Milky Way (100–400 billion).

• The footprints astronauts left on the Moon in 1969 will likely remain for millions of years — there is no wind or water to erase them.

Earth

• The deepest point in the ocean, Challenger Deep, is about 10,935 m — Mount Everest could sit there with over 2 km of water above it.

• About 95% of the world's earthquakes happen along the edges of the Pacific plate, the ring of fire.

• A single lightning bolt can heat the air around it to roughly 30,000 °C — about five times hotter than the Sun's surface.

• Rivers carry about 11 billion tonnes of sediment into the sea every year, slowly rebuilding coastlines.

• Antarctica holds about 60% of the world's fresh water, locked in ice up to 4 km thick.

Life

• An octopus has three hearts, eight arms and blue copper-based blood.

• Honey does not spoil: sealed jars found in 3,000-year-old Egyptian tombs were still edible.

• A blue whale's tongue can weigh as much as an elephant, and its heart can be heard from 3 km away in water.

• Trees can communicate and share nutrients through underground fungal networks scientists call the wood-wide web.

• Sharks existed before trees: the oldest shark fossils are about 450 million years old, trees appear in the record around 350 million.

• Bananas are slightly radioactive because of naturally occurring potassium-40 — nowhere near enough to harm you.

Body

• Your body makes about 25 billion new red blood cells every day, each living roughly 120 days.

• The human nose can distinguish over a trillion different smells, according to a 2014 Science study.

• Stomach acid is strong enough to dissolve metal; the stomach lining renews itself constantly to survive it.

• You are about 1 cm taller in the morning — spinal discs compress through the day as you stand.

• The brain uses about 20% of the body's energy despite being only 2% of its weight.

History

• The Ottoman Empire lasted over 600 years (1299–1922) — longer than the Roman Empire in the west lasted.

• Oxford University is older than the Aztec Empire: teaching began at Oxford by 1096, Tenochtitlan was founded in 1325.

• The last public execution by guillotine in France was in 1977 — the death penalty itself ended there in 1981.

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

• Iceland's parliament, the Althing, founded in 930 AD, is one of the oldest surviving parliaments on Earth.

Geography

• Russia spans 11 time zones — more than any other country; it takes a full day to cross by train from Kaliningrad to Vladivostok.

• Canada has more lakes than the rest of the world combined — over 2 million of them.

• The distance from London to New York is greater than from New York to the North Pole.

• Africa is roughly three times the size of Greenland, yet flat maps make them look similar — that is the Mercator projection trick.

• Chile is about 4,300 km long but averages under 180 km wide — the longest north-south country on Earth.

Math

• Zero as a number was formalised in India by the 7th century; Brahmagupta gave rules for computing with it in 628 AD.

• There are more ways to shuffle a deck of 52 cards (52! ≈ 8×10^67) than seconds the Earth has existed.

• The Pythagorean theorem was known to Babylonian scribes over a thousand years before Pythagoras was born.

• A pizza slice is mathematically a sector, and doubling a pizza's radius quadruples its area — size maths matters on the menu.

• The 1976 Four Colour Theorem was the major proof finished by computer — every map needs at most four colours.

Human world

• About 7,000 living languages are spoken today; roughly 40% are endangered, most of them small Indigenous tongues.

• The Great Wall of China is not one wall but many walls built over 2,000 years, totalling over 20,000 km of sections.

• Mount Everest grows about 4 mm taller every year because the Indian plate still pushes into Asia.

• Paper was invented in China during the Han dynasty, roughly 2,000 years before it reached Western Europe.

• The internal-combustion engine did not beat the horse overnight: cars only passed horses as the main US transport around 1915.