We all know that Stephen Hawking has worked on some of the biggest questions about our cosmos.
But what are those ideas?
What's at the centre of a black hole?
Black holes are incredibly dense objects with such strong gravity that nothing, not even light, can escape their pull.
Hawking worked with physicist Roger Penrose to show that if you were able to travel to the centre of a black hole, you'd find something called a 'singularity'.
In a singularity, so much matter is squashed into such a small space that the force of gravity becomes infinite.
Everything is crushed into a point of infinite density, punching a hole through the fabric of the universe, and tearing up the rulebook of physics as we know it.
It's pretty frightening stuff.
What happens at the edge of a black hole?
You might think that a vacuum is empty.
But it's not. At least, not according to quantum theory.
It's fizzing with particles and anti-particles that pop into existence from nowhere and then disappear.
When this happens at the edge of a black hole, one of the pair of particles can fall in, leaving the other to escape.
This tiny stream of escaping particles is known as, ''Hawking radiation.''
Now, those particles that fell into the black hole, they have a negative mass, and cause the black hole to get smaller, and smaller, until it disappears.
It will take a while, in fact a very long while, but in its final moments a black hole will explode with the energy of a million nuclear bombs – leaving nothing behind.
So why is Stephen Hawking our most famous living scientist?
Well, he showed that at one point everything in our universe was squeezed into a singularity, which then exploded into the Big Bang, eventually forming galaxies, stars, planets, you, me, and everything in existence!
That was the beginning of our universe.
And I suppose the incredible thing is that he came up with all these profound, provocative insights without the convenience of being able to write anything down.