1 00:00:00,627 --> 00:00:06,541 In the last video on quasars I think I sparked some interest when I think I threw out the idea of the... 2 00:00:06,541 --> 00:00:10,067 Milky Way Galaxy actually colloding with the Andromeda Galaxy. 3 00:00:10,067 --> 00:00:13,938 Which people think will happen in three to five billion years. 4 00:00:13,938 --> 00:00:20,000 I threw out in the context of maybe, maybe the super massive black holes at the core. 5 00:00:20,000 --> 00:00:24,421 The galactic cores of each of those galaxys will start getting a little bit more material when that... 6 00:00:24,421 --> 00:00:25,200 collision happens. 7 00:00:25,200 --> 00:00:26,667 And maybe quasars will happen. 8 00:00:26,667 --> 00:00:27,667 I don't know. 9 00:00:27,667 --> 00:00:31,590 But given the interest in that what I wanted to do here is kind of an unconventional thing for the Khan... 10 00:00:31,590 --> 00:00:32,123 Academy. 11 00:00:32,123 --> 00:00:33,456 And actually show a video. 12 00:00:33,456 --> 00:00:35,800 And before I play the video I have to give credit where credit is due. 13 00:00:35,800 --> 00:00:42,467 This is a super computer simulation made at the National Center for super computing applications at NASA. 14 00:00:42,467 --> 00:00:47,200 And it's by B. Robinson of Cal Tech and L. Hernquist of Harvord University. 15 00:00:47,200 --> 00:00:51,067 And what I want you to remember is this is super sped up in time. 16 00:00:51,067 --> 00:00:56,585 Just to give an idea the amount of time it takes for a star about as far away as the sun to make one... 17 00:00:56,585 --> 00:01:01,702 orbit around the galactic core is two-hundred and fifty million years. 18 00:01:01,702 --> 00:01:06,005 And you're going to see that this is happening multiple times over the course of this video. 19 00:01:06,005 --> 00:01:09,200 So this video is actually spanning billions of years. 20 00:01:09,200 --> 00:01:13,467 But when you actually speed up time like that you'll see that it really gives you the sense of the actual 21 00:01:13,467 --> 00:01:15,000 dynamics of these interactions. 22 00:01:15,000 --> 00:01:19,133 The other thing that I want to talk about before I actually start the video is to make you realise that 23 00:01:19,133 --> 00:01:23,267 when we talk about galaxies colliding it doesn't mean that the stars are colliding. 24 00:01:23,267 --> 00:01:26,133 In fact there are going to be very few stars that actually collide. 25 00:01:26,133 --> 00:01:28,667 The probability of a star, star collision is very low. 26 00:01:28,667 --> 00:01:33,667 And that's cause we learned when we learned about interstellar scale that there's mostly free space... 27 00:01:33,667 --> 00:01:34,467 inbetween stars. 28 00:01:34,467 --> 00:01:37,667 The closest star to us 4.2 light-years away. 29 00:01:37,667 --> 00:01:42,800 And that's roughly thirty-million times the diameter of the sun. 30 00:01:42,800 --> 00:01:46,600 So you have a lot more free space than star space... 31 00:01:46,600 --> 00:01:47,933 or even solar system space. 32 00:01:47,933 --> 00:01:50,667 So lets start up this animation 33 00:01:50,667 --> 00:01:51,667 It's pretty amazing. 34 00:01:51,667 --> 00:01:53,729 And what you're going to see here, so these are just the... 35 00:01:53,729 --> 00:01:57,600 obviously, so one rotation is actually 250,000,000 years give or take. 36 00:01:57,600 --> 00:02:00,600 But now you see these stars right here... 37 00:02:00,600 --> 00:02:02,067 are starting to get attracted to this core. 38 00:02:02,067 --> 00:02:04,333 And then they're actually attracted to that core. 39 00:02:04,333 --> 00:02:08,333 And then some of the stuff in that core was attracted to those stars. 40 00:02:08,333 --> 00:02:09,733 And they get pulled away. 41 00:02:09,733 --> 00:02:12,200 That was the first pass of these two galaxies. 42 00:02:12,200 --> 00:02:15,400 Some stuff is just being thrown off into intergalactic space. 43 00:02:15,400 --> 00:02:18,533 And you might worry, maybe that'll happen to the Earth. 44 00:02:18,533 --> 00:02:20,133 And there's some probability that it would happen to the Earth. 45 00:02:20,133 --> 00:02:24,267 But it really wouldn't affect what happens within those stars solar systems. 46 00:02:24,267 --> 00:02:25,733 This is happening so slow. 47 00:02:25,733 --> 00:02:27,667 You wouldn't feel like some type of acceleration or something. 48 00:02:27,667 --> 00:02:29,733 And then this is the second pass. 49 00:02:29,733 --> 00:02:35,867 They've passed one pass and this is occurring over hundreds of millions or billions of years. 50 00:02:35,867 --> 00:02:40,133 And on the second pass they finally are able to merge. 51 00:02:40,133 --> 00:02:43,000 And all of these interactions are just due to the gravity over interstellar 52 00:02:43,000 --> 00:02:45,533 Or almost, you could call it, intergalactic distances. 53 00:02:45,533 --> 00:02:51,641 You can see they merge into what could be called a Milkomeda or maybe the Andromedy Way. 54 00:02:51,641 --> 00:02:53,333 I don't know, whatever you want to call it. 55 00:02:53,333 --> 00:02:58,133 But even though they've merged a lot of the stuff has still been thrown off into intergalactic space. 56 00:02:58,133 --> 00:03:01,800 But this is a pretty amazing animation to me. 57 00:03:01,800 --> 00:03:08,267 One; it's amazing to think about how this could happen over galactic space scales... 58 00:03:08,267 --> 00:03:09,267 and time scales. 59 00:03:09,267 --> 00:03:13,467 But it's also pretty neat how a super-computer can do all the computations... 60 00:03:13,467 --> 00:03:18,133 to figure out what every particle, which is really a star, or cluster of stars, or group of stars... 61 00:03:18,133 --> 00:03:22,667 is actually doing to actually give us a sense of the actual dynamics here. 62 00:03:22,667 --> 00:03:25,841 But this is, this is pretty neat, this is pretty neat. 63 00:03:25,841 --> 00:03:27,133 Look at that. 64 00:03:27,133 --> 00:03:30,015 I mean these are, you know, every little dot is whole groups of stars. 65 00:03:30,015 --> 99:59:59,999 Thousands of stars potentially.