Did you know? — archive

Every day's set of facts, newest first.

Today

01
Botanically a banana is a berry — but a strawberry is not. A berry must grow from a single flower with one ovary, and strawberries fail that test.
02
A starfish has no brain and no blood. It pumps seawater through its body instead, and a nerve ring around its mouth coordinates its arms.
03
In seahorses it is the male that becomes pregnant. The female places her eggs in his pouch, and he carries them and releases the young.
04
Flamingos are born grey. Their pink comes from carotenoid pigments in the algae and shrimp they eat, and a bird on the wrong diet fades.
05
A garden snail has thousands of microscopic teeth on a ribbon-like tongue called a radula, which it uses to scrape its food.
06
A honeybee tells the hive where food is by dancing. The angle of her waggle signals the direction relative to the Sun, and its length signals the distance.
07
Koalas have fingerprints so like ours that under a microscope the two can be confused — the same ridged grip evolved twice, quite separately.
08
A sloth can take weeks to digest one meal of leaves. Its stomach has several chambers and its whole body runs at a low temperature to save energy.
09
A peanut is not a nut. It is a legume, closer kin to peas and beans, and it ripens underground rather than on a tree.
10
A cow's stomach has four chambers, and food returns to the mouth to be chewed again. That is how cattle break down grass most animals cannot digest.
11
Jupiter's moon Ganymede is bigger than the planet Mercury. It is the largest moon in the Solar System and the only one with its own magnetic field.
12
Uranus rolls around the Sun on its side, tilted about 98 degrees. Each pole spends roughly 42 years in sunlight and then 42 in darkness.
13
Olympus Mons on Mars rises about 22 km, roughly two and a half times the height of Mount Everest, and is so wide that its slopes curve away out of sight.
14
The Milky Way and Andromeda are falling towards each other and will merge in about 4.5 billion years. Stars sit so far apart that almost none will collide.
15
A light-year measures distance, not time. It is about 9.46 trillion km — the distance light covers in one year.
16
A year on Mercury lasts just 88 Earth days. It is the fastest planet, racing around the Sun at about 47 km per second.
17
Space is silent. Sound needs a material to travel through, and the near-vacuum between the planets holds far too few particles to carry it.
18
Apollo astronauts said moon dust smelled like spent gunpowder, once they were back inside the lander with their helmets off.
19
Water is unusual: it expands as it freezes. Ice is about 9 per cent less dense than water, which is why it floats and why lakes freeze from the top down.
20
Helium is the only element that will not freeze solid at ordinary pressure, however cold it gets. It stays liquid all the way down to absolute zero.
21
Absolute zero is −273.15°C, the point at which particles carry the least energy possible. Nothing has ever been cooled the whole way to it.
22
GPS satellites must correct for relativity. Their clocks tick slightly faster than clocks on the ground, and without the correction positions would drift by about 10 km a day.
23
Antarctica is the largest desert on Earth. A desert is defined by how little falls from the sky rather than by heat, and parts of Antarctica see almost no precipitation.
24
Lightning strikes somewhere on Earth about 44 times every second — roughly 3.8 million flashes a day, most of them over tropical land.
25
The Dead Sea is about 10 times saltier than the ocean. Its water is so dense that a swimmer floats without any effort at all.
26
The Pacific Ocean covers about a third of the Earth's surface — a greater area than all the planet's land put together.
27
The first computer bug was a real insect. In 1947 a moth was found stuck in a Harvard machine's relay, taped into the logbook and noted as the first actual case of a bug being found.
28
A baby is born with about 300 bones, while an adult has 206. Many of them fuse together as a child grows.
29
About 99 per cent of the world's international internet traffic travels through cables lying on the seabed, not through satellites.
30
Glass is mostly melted sand. Silica has to be heated to roughly 1,700°C, and adding soda lowers that enough to make everyday glassmaking practical.

Did you know? — archive

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