Near a black hole space and time do some very strange things because the black holes are probably the most
violent places we know of in the universe. This river provides a beautiful analogy of what happens
to space and time as you get closer and closer to the black hole.
Now upstream the water is flowing pretty slowly.
Let's imagine it is flowing at three kilometers per hour
and I can swim at 4, so I can swim faster than the flow and can easily escape
But as you go further, further down the stream towards
the waterfall in the distance, the river flows faster and faster.
Imagine that I decided to jump in the river just there at the edge of the falls
The water is flowing far faster than I could swim.
So, no matter what I did, no matter how hard I tried
I would not be able to swim back upstream
I would be carried inextrably towards the edge and I would vanish over the falls
Well, it's the same close to the black hole,
because the space flows faster, faster and faster
towards the black hole.
Literally, this stuff, my space that I am in, flowing over the edge into the black hole.
And then, a very special point, called an event horizon, the space is flowing
at the speed of light into the black hole.
Light itself, travelling at 3000km per second is not going fast enough to escape the flow
and light itself will plunge into the black hole.
Well, as you fall into the black hole, across the event horizon, then if you were going feet first, your feet will be
accelerating faster than your head, so you'll be stretched
and you'll be quite literally spaghettified
Now as you get right into the center,
Then our understanding of physics breaks down.
Our best theory of space and time, Einstein's theory of general relativity
says that space and time become infinitely curved, that
the center of the hole becomes infinitely dense
That place is called the singularity and it is the place
where our understanding of the Universe stops.