1 00:00:01,240 --> 00:00:06,133 So to really get a sense for these objects nothing is better than an actual 2 00:00:06,133 --> 00:00:09,044 tour luckily a virtual tour to a black hole. 3 00:00:09,044 --> 00:00:13,813 Our tour guide is Andy Hamilton of Colorado University who has generously 4 00:00:13,813 --> 00:00:16,848 let us use these beautiful simulations he's made. 5 00:00:16,848 --> 00:00:19,760 So we're, we're er, going to approach this 6 00:00:19,760 --> 00:00:25,695 Little system of stars we got a 60 solar mass blue main sequence star with some 7 00:00:25,695 --> 00:00:31,631 other e smaller stars and orbiting in a binary system with this blue star is a 30 8 00:00:31,631 --> 00:00:35,780 solar mass black hole, which of course we can't see and 9 00:00:35,780 --> 00:00:39,551 30 solar masses tells us that its Schwarzschild radius is 30 times the sun 10 00:00:39,551 --> 00:00:43,050 mass, three kilometers. And this is an image of our trajectory. 11 00:00:43,050 --> 00:00:47,040 We are going to be in free fall, so we're going to be accelerated towards 12 00:00:47,040 --> 00:00:50,921 the system and fall into an unstable orbit at, two Schwarzschild radii. 13 00:00:50,921 --> 00:00:54,638 That is a zero energy orbit, so you can actually freely fall without 14 00:00:54,638 --> 00:00:56,934 any engine power into that unstable orbit. 15 00:00:56,934 --> 00:01:00,160 You don't want to miss, because if you miss by a little bit, 16 00:01:00,160 --> 00:01:04,677 you either could fly, flown back off to infinity or fall into the black hole. 17 00:01:04,677 --> 00:01:09,316 of course since it's virtual, we'll manage to survive it either way. 18 00:01:09,316 --> 00:01:14,465 But let's start by approaching this system from a distance and see what the 19 00:01:14,465 --> 00:01:17,446 effects are of coming close to a black hole. 20 00:01:17,446 --> 00:01:22,933 So, I start the simulation and we are falling from a 100 million kilometers. As 21 00:01:22,933 --> 00:01:28,217 we approach at about a 100 Schwarzschild radii, the lensing of the black hole 22 00:01:28,217 --> 00:01:33,728 produces what is called an Einstein ring. The hole, a doughnut-shaped image of the 23 00:01:33,728 --> 00:01:38,967 blue star, which is formed by light lensing and bending all around the black 24 00:01:38,967 --> 00:01:41,862 hole. And as we get nearer we see multiple 25 00:01:41,862 --> 00:01:47,199 lensed images of all of the stars, because remember we are now at The, this 26 00:01:47,199 --> 00:01:52,608 clip ends at three Schwarzschild radii, the last stable orbit. deflection of 27 00:01:52,608 --> 00:01:57,153 light is significant and we see these multiple lensing effects. 28 00:01:57,153 --> 00:02:01,437 Notice that on the bottom, on the horizon itself the 29 00:02:01,437 --> 00:02:06,401 animator has superimposed this nice red grid for us. Of course the actual horizon 30 00:02:06,401 --> 00:02:11,121 does not have a red grid on it and if it did you would not be able to see it. 31 00:02:11,121 --> 00:02:15,105 But this just tells you where the Schwarzschild horizon is, and the 32 00:02:15,105 --> 00:02:20,132 interesting property is that because of the deflection of light note that you can 33 00:02:20,132 --> 00:02:25,097 see both poles of the horizon. So you can see all the way around it because light 34 00:02:25,097 --> 00:02:28,897 is so greatly deflected. anA so that was us at the last stable 35 00:02:28,897 --> 00:02:32,330 orbit, at three Schwarzschild radii, but that is for sissies. We are heading down 36 00:02:32,330 --> 00:02:37,431 to two Schwarzschild radius orbit. We are now orbiting the black hole at two 37 00:02:37,431 --> 00:02:41,135 Schwarzschild radii. We see all of the enhanced lensing 38 00:02:41,135 --> 00:02:46,027 effects that I was talking about. We see multiple images of all of the 39 00:02:46,027 --> 00:02:49,242 stars, in the cluster. forming and disappearing. 40 00:02:49,242 --> 00:02:53,506 If you want to know the proper time period of orbit is about four 41 00:02:53,506 --> 00:02:56,607 milliseconds. first to someone viewing us from far 42 00:02:56,607 --> 00:03:00,526 away, it's a factor of two. Note what a two Schwarzschild radii. 43 00:03:00,526 --> 00:03:03,919 The gravitational redshift factor is a square root of two, 44 00:03:03,919 --> 00:03:08,600 but there's another square root of two because we are moving at about 0.7 times 45 00:03:08,600 --> 00:03:12,753 the speed of light to maintain this orbit at two Schwarzschild radii. 46 00:03:12,753 --> 00:03:17,258 You can compute both of those things. So looking from afar, we would appear to 47 00:03:17,258 --> 00:03:21,821 be orbiting at every eight milliseconds, where in fact we think we're orbiting 48 00:03:21,821 --> 00:03:25,327 every 4 milliseconds. The tidal forces at this point are I 49 00:03:25,327 --> 00:03:29,370 believe a thou- a 100 times G. So your feet are pulling on your head 50 00:03:29,370 --> 00:03:33,469 with 100 times their weight. You're getting a little bit uncomfortable, I 51 00:03:33,469 --> 00:03:36,373 should think, and then these white dots are a probe 52 00:03:36,373 --> 00:03:40,074 that is being dropped conveniently, 400 kilometers ahead of us. 53 00:03:40,074 --> 00:03:43,092 down onto the surface of the black hole from rest, 54 00:03:43,092 --> 00:03:47,476 and as we approach it we see it falling down because it's dropped ahead of us in 55 00:03:47,476 --> 00:03:51,462 orbit and we see it falling down. And what we see is A, this probe is a 56 00:03:51,462 --> 00:03:55,631 sphere and we see this tidal force stretching it out till it's no longer 57 00:03:55,631 --> 00:03:58,902 anything like a sphere. And second of all, we see there as it 58 00:03:58,902 --> 00:04:02,658 would fall, as it approaches the Schwarzschild horizon, 59 00:04:02,658 --> 00:04:06,838 it is reddened and slows down. The bit that is closest to the horizon 60 00:04:06,838 --> 00:04:11,018 appears to stop falling first, and eventually, it turns red, and merges 61 00:04:11,018 --> 00:04:14,531 with the horizon. We can't see it because the red shift is 62 00:04:14,531 --> 00:04:18,542 infinite, even between the Schwarzschild horizon and the orbit at two 63 00:04:18,542 --> 00:04:22,150 Schwarzschild radii where we are. And now, 64 00:04:22,150 --> 00:04:26,060 well this is unstable, but not dangerous enough for us. 65 00:04:26,060 --> 00:04:30,011 We're not here for the tourist version. We're going all the way. 66 00:04:30,011 --> 00:04:34,998 We're going to fire the boosters slow ourselves down slightly and land on, well 67 00:04:34,998 --> 00:04:38,939 not land, but penetrate through the surface of the black hole. 68 00:04:38,939 --> 00:04:44,043 We just cross the horizon, and at the point that we cross the horizon within 69 00:04:44,043 --> 00:04:48,500 about a tenth of a millisecond, we are going to be in the, hitting the 70 00:04:48,500 --> 00:04:51,408 singularity for a 30 solar mass black hole. 71 00:04:51,408 --> 00:04:56,511 The g-forces at the Schwarzschild of radii, radius for this 30 solar mass 72 00:04:56,511 --> 00:05:00,905 black hole are a million g. So we have long since been decomposed, 73 00:05:00,905 --> 00:05:06,035 and as we fall through the horizon, we will meet anybody who fell through 74 00:05:06,035 --> 00:05:09,624 just before us, and we have a tenth of a millisecond to 75 00:05:09,624 --> 00:05:14,844 have a deep conversation with them before we hit the singularity and everything 76 00:05:14,844 --> 00:05:18,041 ends. So this was a quick tour of a black hole. 77 00:05:18,041 --> 00:05:19,477 And you lived to tell.