Myth: The Great Wall of China is the only human-made object visible from space (or the Moon).
Fact: Many human-made objects are visible from space but the Great Wall of China is not really one of them. The Great Wall isn't very wide and its colour tends to match its environment. Astronauts report that they can see it easily with a telescope or zoom lens, but not with the unaided eye.
No human-made objects are visible from the Moon without a telescope.
Myth: Until a few hundred years ago everyone thought the Earth was flat.
Fact: Educated people have known that the Earth is spherical since at least 500 B.C. Around 240 B.C., Greek mathematician Eratosthenes even made a good estimate of the circumference of the Earth.
Myth: The vacuum of space would make you explode.
Fact: If you were exposed to the vacuum of space, you'd die in less than two minutes. During that time you'd experience some bloating but no exploding.
Myth: Asteroid Belts are dangerously dense.
Fact: The popular image of an asteroid belt is that there are millions of huge rocks floating within metres of each other. In movies such as The Empire Strikes Back, it's shown to be an incredibly dangerous place for a spaceship. In reality it's not like that—although asteroid belts are relatively dense compared to the rest of space, if you were standing on an asteroid you probably couldn't even see any others because they'd be so far away. Spacecraft have passed through our own Asteroid belt many times without any problems.
Myth: Meteorites are very hot when they land.
Fact: Actually they're barely warm and quite safe to touch.
Myth: There is no gravity in space.
Fact: Technically speaking there is at least some amount of gravity throughout the entire Universe. The gravity in low Earth orbit is similar to the gravity on the ground. Objects in space float because they are weightless, which is different to being in zero gravity. The end result is basically the same but they are technically different things.
Myth: Black holes suck up everything in their vicinity.
Fact: Black holes have gravitational properties just like everything else—no worse. If our Sun was replaced with a black hole of the exact same mass, all the planets would continue to orbit in exactly the same way.
Myth: The Sun is yellow.
Fact: The Sun can appear to be yellow from the surface of the Earth, but that's because of light scattering in our atmosphere. It's actually quite white.
Myth: There is a permanent dark side of the Moon.
Fact: At any one time, half of the Moon is in shadow and half of it is in sunshine, just like on Earth. However there is no permanent dark side of the Moon any more than there is a permanent dark side of the Earth. When referring to the side of the Moon we can't see, it's better to call it the far side of the Moon, as it's not necessarily dark at all.
Myth: Mysterious artificial structures have been found on other planets.
Fact: So far we’ve only seen natural features. Some of them do resemble faces or buildings from a distance, just like some natural features do here on Earth. The famous “Face on Mars” is a good example. Many people thought this was evidence of an advanced civilization until high-resolution photos showed that it’s just a type of tableland hill called a mesa.