In science fiction, black holes are often used for time travel - or even to power spacecraft.
But what are they actually like close up - and what would happen if Earth fell into one?
A week after gravitational waves from the merger of two black holes were detected for the first time, Kevin Pimbblet of Hull University reveals what one would actually do to Earth.
Writing on The Conversation, Pimbblet says that the intense gravity stretches objects out - known as ‘spaghettification’ - but other effects would devastate Earth first.
Pimbblet says, ‘The same gravitational effects that produced spaghettification would start to take effect here. The edge of the Earth closest to the black hole would feel a much stronger force than the far side.
‘As such, the doom of the entire planet would be at hand. We would be pulled apart.
‘Radiation is generated when the black hole is feasting on new material. To be clear: this material is still outside the event horizon which is why we can still see it. Below the event horizon is where nothing, not even light, can escape. As all the matter piles up from the feast, it will glow. It is this glow that is seen when observers look at quasars.
‘But this is a problem for anything orbiting (or near) a black hole, as it is very hot indeed. Long before we would be spaghettified, the sheer power of this radiation would fry us.
‘But don’t lose too much sleep, we’d have to be unfortunate to “hit” a black hole in the first place – and we might live on holographically after the crunch anyway.’