1 00:00:23,600 --> 00:00:31,360 Near a black hole space and time do some very strange things because the black holes are probably the most 2 00:00:31,360 --> 00:00:39,280 violent places we know of in the universe. This river provides a beautiful analogy of what happens 3 00:00:39,280 --> 00:00:42,760 to space and time as you get closer and closer to the black hole. 4 00:00:47,840 --> 00:00:51,080 Now upstream the water is flowing pretty slowly. 5 00:00:51,080 --> 00:00:54,440 Let's imagine that it is flowing at three kilometers per hour 6 00:00:54,440 --> 00:01:00,520 and I can swim at 4, so I can swim faster than the flow and can easily escape 7 00:01:16,000 --> 00:01:19,520 But as you go further, further down the stream towards 8 00:01:19,520 --> 00:01:23,520 the waterfall in the distance, the river flows faster and faster. 9 00:01:43,280 --> 00:01:48,640 Imagine that I decided to jump in the river just there at the edge of the falls 10 00:01:48,640 --> 00:01:52,640 The water is flowing far faster than I could swim. 11 00:01:52,640 --> 00:01:55,720 So, no matter what I did, no matter how hard I tried 12 00:01:55,720 --> 00:01:59,560 I would not be able to swim back upstream 13 00:01:59,560 --> 00:02:04,480 I would be carried inextricably towards the edge and I would vanish over the falls 14 00:02:20,760 --> 00:02:23,480 Well, it's the same close to the black hole, 15 00:02:23,480 --> 00:02:28,520 because the space flows faster, faster and faster 16 00:02:28,520 --> 00:02:30,000 towards the black hole. 17 00:02:30,000 --> 00:02:36,160 Literally, this stuff, my space that I am in, flowing over the edge into the black hole. 18 00:02:36,160 --> 00:02:42,920 And then, at a very special point, called the event horizon, the space is flowing 19 00:02:42,920 --> 00:02:45,960 at the speed of light into the black hole. 20 00:02:50,800 --> 00:02:57,280 Light itself, travelling at 300.000km per second is not going fast enough to escape the flow 21 00:02:57,280 --> 00:03:01,280 and light itself will plunge into the black hole. 22 00:03:16,160 --> 00:03:22,840 Well, as you fall into the black hole, across the event horizon, then if you were going feet first, your feet will be 23 00:03:22,840 --> 00:03:27,160 accelerating faster than your head, so you'll be stretched 24 00:03:27,160 --> 00:03:31,271 and you'll be quite literally spaghettified. 25 00:03:37,760 --> 00:03:39,520 Now as you get right into the center, 26 00:03:39,520 --> 00:03:43,771 Then our understanding of the laws of physics breaks down. 27 00:03:43,786 --> 00:03:48,120 Our best theory of space and time, Einstein's theory of general relativity 28 00:03:48,120 --> 00:03:51,800 says that space and time become infinitely curved, that 29 00:03:51,800 --> 00:03:55,551 the center of the hole becomes infinitely dense 30 00:03:56,469 --> 00:03:59,920 That place is called the singularity and it is the place 31 00:03:59,920 --> 00:04:05,160 where our understanding of the Universe stops.