WEBVTT

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

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violent places we know of in the universe. This river provides a beautiful analogy of what happens

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to space and time as you get closer and closer to the black hole.

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Now upstream the water is flowing pretty slowly.

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Let's imagine it is flowing at three kilometers per hour

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and I can swim at 4, so I can swim faster than the flow and can easily escape

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But as you go further, further down the stream towards

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the waterfall in the distance, the river flows faster and faster.

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Imagine that I decided to jump in the river just there at the edge of the falls

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The water is flowing far faster than I could swim.

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So, no matter what I did, no matter how hard I tried

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I would not be able to swim back upstream

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I would be carried inextrably towards the edge and I would vanish over the falls

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Well, it's the same close to the black hole,

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because the space flows faster, faster and faster

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towards the black hole.

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Literally, this stuff, my space that I am in, flowing over the edge into the black hole.

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And then, a very special point, called an event horizon, the space is flowing

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at the speed of light into the black hole.

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Light itself, travelling at 3000km per second is not going fast enough to escape the flow

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and light itself will plunge into the black hole.

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Well, as you fall into the black hole, across the event horizon, then if you were going feet first, your feet will be

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accelerating faster than your head, so you'll be stretched

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and you'll be quite literally spaghettified

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Now as you get right into the center,

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Then our understanding of physics breaks down.

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Our best theory of space and time, Einstein's theory of general relativity

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says that space and time become infinitely curved, that

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the center of the hole becomes infinitely dense

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That place is called the singularity and it is the place

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where our understanding of the Universe stops.