Transcript

BRIAN COX

Near a black hole, space and time do some very strange things, because black holes are probably the most violent places we know of in the universe. This river provides a beautiful analogy for what happens to space and time as you get closer and closer to the black hole.

[MUSIC PLAYING]

Now, upstream the water is flowing pretty slowly. Let’s imagine that it’s flowing at three kilometers per hour, and I can swim at four. So I can swim faster than the flow, and can easily escape.

[BIRDS CHIRPING]

But, as you go further and further downstream towards the waterfall in the distance, the river flows faster and faster.

[MUSIC PLAYING]

Imagine I was to decide to jump into the river, just there on 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 inexorably towards the edge. And I would vanish over the falls.

Well, it’s the same close to a black hole, because space flows faster, and faster, and faster towards the black hole.

Literally, this stuff, my space that I’m in, flowing over the edge into the black hole. And at the very special point called the ‘event horizon’, space is flowing at the speed of light into the black hole.

Light itself, travelling at 300,000 kilometres per second, is not going fast enough to escape the flow. And light itself will plunge into the black hole.

[RUSHING WATER]