Space Facts: Seven Planets Fit Between Earth and the Moon — and 9 Other Numbers That Will Break Your Brain

Seven planets fit in the gap between Earth and the Moon. Not metaphorically. Not scaled down. Literally: line up Mercury, Venus, Mars, Jupiter, Saturn, Uranus, and Neptune side by side. They cover roughly 380,000 kilometres. The Moon is 384,400 kilometres away.

Most people's mental model of the solar system comes from textbook diagrams — tiny planets, vast distances. But the gap between Earth and its nearest neighbour is, in solar system terms, startlingly small. Here are nine more facts that break the usual mental model.

How heavy is a neutron star?

A neutron star forms when a massive star collapses at the end of its life. The result: an object roughly 20 kilometres across — the size of a city — with the mass of 1.5 suns compressed inside it. The density is so extreme that a single teaspoon of neutron star material would weigh over a billion tonnes.

To feel how absurd that is: the entire human race weighs roughly 400 million tonnes. One teaspoon of neutron star outweighs every person alive, combined, by more than double. If you could drop that teaspoon onto Earth's surface, it would punch straight through the crust, the mantle, the core, and out the other side without meaningfully decelerating. The planet would barely notice.

How old is the sunlight hitting Earth right now?

The light reaching your face today is probably around 100,000 years old. Not 8 minutes — that's just the final leg of the journey. The Sun's core is so dense that a single photon, born in a fusion reaction, gets absorbed and re-emitted millions of times before it ever escapes the solar surface. That process takes anywhere between 10,000 and 170,000 years. Only then does the photon cross 150 million kilometres to Earth in 8 minutes and 20 seconds.

The 8 minutes is the easy part. You're being illuminated by ancient light — photons born before modern humans walked the Earth.

Is a day on Venus longer than a year on Venus?

Yes. Venus takes 243 Earth days to complete one rotation on its axis. It only takes 225 Earth days to orbit the Sun. So a Venusian "year" ends before a Venusian "day" does. You could have an entire birthday pass before sunrise arrives.

And when the sun does rise on Venus, it rises in the west and sets in the east. Venus rotates backwards — retrograde — compared to Earth. Scientists think it may have been slowly tipped over by gravitational interactions with the Sun over billions of years, or flipped by an ancient giant impact. Either way, every morning on Venus is a western sunrise, and it arrives less than twice per orbit.

How long do Apollo footprints last on the Moon?

Neil Armstrong's bootprints from July 1969 are still there. Sharp-edged. Undisturbed. They will remain visible for approximately 100 million years.

The Moon has no weather. No wind. No rain. Its atmosphere is so thin it barely qualifies as one. The only thing disturbing the lunar surface is micrometeorites — dust-grain-sized particles hitting at high speed — which erode the surface at roughly a millimetre every million years. At that rate, the Apollo landing sites will outlast the Atlantic Ocean, the Himalayas, and most of the geography that currently exists on Earth. Twelve people walked on the Moon between 1969 and 1972. Their footprints may be the most durable physical record humanity has ever left anywhere.

What does space smell like?

Astronauts returning from spacewalks consistently describe the same thing when they remove their helmets: a sharp, metallic odour on their suits. Like hot metal. Like welding fumes. Slightly charred. Not sterile emptiness — something specific and slightly unsettling.

Scientists believe the smell comes from polycyclic aromatic hydrocarbons and high-energy solar radiation reacting with suit materials during the extravehicular activity. These carbon compounds are the same class of molecules that drift through interstellar dust clouds and that seeded early Earth with pre-biological chemistry. You're smelling the raw building blocks of organic life, slightly scorched by the Sun. Learn more about how satellites observe Earth from orbit on SkyLens.

Would Saturn float in water?

Saturn's average density is 687 kilograms per cubic metre. Water's density is 1,000 kilograms per cubic metre. If you had an ocean large enough — roughly the size of a small star system — Saturn would float at the surface.

It looks imposing in photographs. In reality, it's mostly hydrogen and helium compressed into exotic states by gravity, but not densely enough to sink in water. There is no solid surface to land on. Fall into Saturn and the pressure and temperature rise steadily until you reach a deep, churning metallic hydrogen interior. The rings, the storms, the sheer visual scale — all of it is essentially a very large, elaborate weather system with nowhere to stand inside it.

How far away is space right now?

Space begins 100 kilometres above your head. That's the Kármán line — the internationally recognised boundary between Earth's atmosphere and outer space.

100 kilometres is the distance from London to Oxford. From New York City to Philadelphia. From Paris to Chartres. If a road existed pointing straight up, you could drive to space in just over an hour at highway speeds. The reason nobody does: gravity, air resistance, and the need to travel at roughly 28,000 kilometres per hour sideways to stay in orbit. The distance is nothing. The physics is everything.

Does the galaxy smell like raspberries and rum?

In a chemical sense: yes. Astronomers studying Sagittarius B2 — a massive molecular cloud near the centre of the Milky Way — detected ethyl formate, a compound that smells like raspberries, and propyl cyanide, which carries a rum-like quality. These aren't contamination artefacts. They're part of the organic chemistry that saturates giant molecular clouds throughout the galaxy.

The same clouds contain ethanol, methanol, glycolaldehyde (a simple sugar), and glycine — one of the building blocks of proteins. These clouds are trillions of kilometres across. When they collapse under gravity to form new stars and planets, they seed those worlds with ready-made organic chemistry. Earth didn't generate its biological ingredients in isolation. Some of them arrived from vast interstellar clouds that, chemically speaking, smelled like a cocktail bar.

Are you actually made of dead stars?

Yes — and not as a metaphor. Every atom in your body heavier than hydrogen was forged inside a star or ejected in a supernova explosion. The oxygen you're breathing. The calcium in your teeth. The iron in your blood. None of these elements existed before the first generation of stars lived, burned out, and exploded. The Big Bang produced hydrogen, helium, and trace amounts of lithium. That's the complete list. Everything else on the periodic table — from carbon to gold to uranium — was built inside stellar cores over billions of years, then scattered across the galaxy by supernovae.

The universe took 13.8 billion years to assemble the atoms in your hand. You are, in the most literal chemical sense, recycled stellar material — the universe looking at itself through borrowed eyes.