12 Fun Space Facts That Sound Made Up (But Aren't)

Space is big, old and strange in ways that are hard to picture. Here are twelve facts that sound invented — and the science behind each one.

1. A day on Venus is longer than its year

Venus takes about 243 Earth days to spin once on its axis, but only about 225 Earth days to orbit the Sun. So its "day" outlasts its "year". It also spins backwards compared with most planets, so on Venus the Sun would rise in the west.

2. The Moon is drifting away

Every year the Moon moves about 3.8 cm farther from Earth — roughly the rate your fingernails grow. We know this precisely because Apollo astronauts left mirrors on the surface, and observatories still bounce lasers off them today. Earth's tides are slowly transferring energy to the Moon, which also lengthens our day by a tiny fraction over millions of years.

3. Neptune was discovered with maths

In the 1840s, astronomers noticed Uranus wasn't moving quite as predicted. Urbain Le Verrier calculated where an unseen planet would have to be to tug it off course. In 1846, Johann Galle pointed a telescope at that spot and found Neptune within a degree of the prediction.

4. You couldn't stand on Jupiter

Jupiter is a gas giant. Its atmosphere gets denser and hotter the deeper you go, gradually becoming liquid, with no solid surface to land on. A probe would be crushed long before reaching anything solid at the core.

5. Jupiter could fit about 1,300 Earths

By volume, Jupiter could hold roughly 1,300 Earths, and the Sun could hold about 1.3 million. Yet the Sun is only an average-sized star.

6. A year on Mercury is 88 days — and its day is weirder

Mercury orbits the Sun in 88 Earth days and rotates once every 59 Earth days. Because it's spinning and orbiting at the same time, one full sunrise-to-sunrise "solar day" on Mercury lasts about 176 Earth days — two of its years.

7. There may be more stars than grains of sand

Astronomers estimate the observable universe contains somewhere around 10²² to 10²⁴ stars. Rough estimates for all the grains of sand on Earth's beaches are around 10¹⁸ to 10²¹. The numbers are fuzzy, but the stars very likely win.

8. Some planets might be made partly of diamond

55 Cancri e, a planet about 41 light-years away, was once proposed to be rich in carbon — possibly with layers of diamond under extreme pressure. Later observations complicated that picture, but carbon-rich worlds like it remain a real possibility.

9. Black holes aren't holes

A black hole is an enormous amount of mass squeezed into a tiny space, with gravity so strong that nothing — not even light — escapes past its event horizon. If the Sun were replaced by a black hole of the same mass, Earth's orbit wouldn't change; it would just get very dark and cold.

10. Space isn't completely empty

Even the emptiest intergalactic space contains a few atoms per cubic metre, plus radiation, including the faint cosmic microwave background left over from the early universe.

11. Footprints on the Moon could last millions of years

The Moon has no wind or water to erode the Apollo astronauts' footprints. Tiny meteorite impacts will eventually blur them, but that takes a very long time.

12. When you look up, you're looking back in time

Light takes time to travel. Sunlight is about 8 minutes old when it reaches you. Light from the nearest star system, Alpha Centauri, left over 4 years ago, and the light from distant galaxies set out billions of years ago, before Earth existed.

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