Myths

Myths and big questions

Black holes star in a lot of films. Here is what the scientists actually say.

How this site works. Every fact is in our own words and linked to its source, beside it. Where good sources disagree, we show each version in a “Sources differ” box.

1. MythBlack holes suck everything in, like cosmic vacuum cleaners.

   FactBlack holes are not cosmic vacuum cleaners. They don’t suck in other matter: from far enough away, their gravity acts just like that of anything else with the same mass. NASA

2. MythBlack holes are holes.

   FactBlack holes aren’t really holes. They are huge amounts of matter packed into very small spaces. NASA

3. MythBlack holes are tunnels to other universes.

   FactBlack holes are not wormholes. They don’t give shortcuts between places in space, or portals to other dimensions or universes. NASA

4. MythA black hole could swallow a whole galaxy.

   FactA black hole cannot eat a whole galaxy. Even a supermassive one’s reach is nowhere near big enough. NASA, 10 questions

5. MythOne day black holes will swallow the whole universe.

   FactThe universe won’t all be swallowed: each black hole’s zone of strong gravity is small compared with a galaxy, and the universe is big and expanding. NASA, 10 questions

6. MythIf the Sun became a black hole, the planets would fall in.

   FactIf the Sun were swapped for a black hole of the same mass, the planets would stay in their orbits, though the solar system would get a lot colder. NASA

7. MythThe Sun will become a black hole.

   FactThe Sun will never become a black hole. It isn’t massive enough to explode, and will end its life as a white dwarf. NASA, 10 questions

8. MythBlack holes are rare.

   FactBlack holes are not rare. Most galaxies the size of the Milky Way have a giant one at their centre. NASA

9. MythThe Milky Way’s black hole will pull Earth in.

   FactThere is no danger of Earth being pulled in. NASA, 10 questions

10. MythWhen things fall in, their gravity disappears.

    FactMatter that falls in adds to the black hole’s mass. Its gravity doesn’t disappear from the universe. NASA, 10 questions

11. MythBlack holes last for ever.

    FactThe physicist Stephen Hawking proposed that black holes also slowly shrink, because they lose tiny amounts of energy, now called Hawking radiation. NASA, 10 questions For most black holes we know about, shrinking noticeably would take much longer than the entire age of the universe. NASA, 10 questions

12. MythTelescopes can see black holes directly.

    FactTelescopes don’t see black holes themselves. They see what happens around them: hot gas, orbiting stars and bent light. NASA

13. MythBlack holes are only bad news for the universe.

    FactThe exploding stars that leave black holes behind spread elements needed for life, such as carbon, nitrogen and oxygen. In a sense, NASA says, we owe our existence to them. NASA, 10 questions

Big open questions

Which came first, the galaxy or its black hole, is still one of the great puzzles of the universe. NASA, 10 questions

A quasar is a supermassive black hole with gas pouring in so fast that it gives out a thousand times more energy than its whole galaxy. NASA, 10 questions

Black holes are much studied but not fully understood. Nobody knows, for example, what matter looks like inside the event horizon. NASA

Nobody has yet found definite proof that primordial black holes ever existed. NASA, types