THE universe is full of holes. Black holes.
Well, they’re not really holes – it’s a bit of a misleading name, to be honest. Black holes are not holes as we understand the term – they’re not filled with nothing. In fact, they’re anything but empty.
A black hole is what we call it when a huge amount of matter has been packed tight into a small space. Think of it as three of our suns, all squeezed together into a space small enough to fit a city in. A bit squashed, truth be told.
All that dense matter produces a gravitational field so strong that it draws everything close towards it and nothing can escape – not even light. Hence the darkness. But black holes don’t ‘suck’ like a vacuum cleaner (they are not vacuums) – instead, things fall into them.
We can’t see a black hole with any of our telescopes, but we know they are there because we can see their effect on other things – such as when they pull apart stars. They are immensely powerful, and there are billions of them in the universe, probably millions in our own Milky Way.
As far as we understand it, a black hole is formed when a massive star dies. Small stars don’t produce enough mass to create one. When the star burns up the last of its fuel, it collapses in on itself. When it pulls in matter from outside itself, such as dust and other stars, it becomes even bigger.
Sometimes, when matter is drawn into a black hole, it hits what is known as the event horizon – the boundary at the edge of the black hole – and is sent back outwards like a ricochet, creating huge jets of material which we can see with our telescopes.
So what would happen to you if you fell into a black hole? Well, I think it’s a safe bet to say you’d be dead long before you got there, but for argument’s sake let’s imagine it. One theory is you would be stretched into a string-like being; another that you would burn up in fire. Let’s just say we’ve not got close enough yet to find out.
Black holes can be any size – scientists think the smallest ones are as small as one atom, but with the mass of a mountain. Imagine that – you could have dozens in your pocket! The biggest, called supermassive black holes, could be as big as 20 of our suns.
But don’t worry, black holes don’t travel around the universe, so there won’t be one approaching earth any time soon. And our own sun is too small to create one, so we’re OK there, too. Phew!