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• 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 that 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 inextricably 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, at a very special point, called the event horizon, the space is flowing

• at the speed of light into the black hole.

• Light itself, travelling at 300.000km 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 the laws 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.

Near a black hole space and time do some very strange things because the black holes are probably the most

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# Black Holes - Wonders of the Universe: Falling - BBC Two

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VoiceTube posted on 2013/04/27
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