0:00:00.000,0:00:00.540 0:00:00.540,0:00:05.594 Right now, the best estimate[br]of when the Big Bang occurred-- 0:00:05.594,0:00:08.010 and once again, I don't like[br]the term that much because it 0:00:08.010,0:00:10.255 kind of implies some[br]type of explosion. 0:00:10.255,0:00:12.130 But what it really is[br]is kind of an expansion 0:00:12.130,0:00:14.540 of space, when space[br]started to really start 0:00:14.540,0:00:16.420 to expand from a singularity. 0:00:16.420,0:00:18.400 But our best estimate[br]of when this occurred 0:00:18.400,0:00:24.320 is 13.7 billion years ago. 0:00:24.320,0:00:26.672 And even though we're used[br]to dealing with numbers 0:00:26.672,0:00:28.130 in the billions,[br]especially when we 0:00:28.130,0:00:30.540 talk about large amounts[br]of money and what not, 0:00:30.540,0:00:32.750 this is an unbelievable[br]amount of time. 0:00:32.750,0:00:35.580 It seems like something that is[br]tractable, but it really isn't. 0:00:35.580,0:00:37.830 And in future[br]videos, I'm actually 0:00:37.830,0:00:39.420 going to talk about[br]the time scale. 0:00:39.420,0:00:41.340 So we can really[br]appreciate how long, 0:00:41.340,0:00:43.170 or even start to[br]appreciate, or appreciate 0:00:43.170,0:00:47.820 that we can't appreciate how[br]long 13.7 billion years is. 0:00:47.820,0:00:51.510 And I also want to emphasize[br]that this is the current best 0:00:51.510,0:00:52.010 estimate. 0:00:52.010,0:00:54.760 Even in my lifetime, even in[br]my lifetime that I actually 0:00:54.760,0:00:57.230 knew about the Big Bang and[br]that I would pay attention 0:00:57.230,0:00:59.360 to what the best estimate[br]was, this number's 0:00:59.360,0:01:00.260 been moving around. 0:01:00.260,0:01:02.320 So I suspect that in[br]the future, this number 0:01:02.320,0:01:04.989 might become more accurate[br]or might move around some. 0:01:04.989,0:01:06.350 But this is our best guess. 0:01:06.350,0:01:08.850 Now with that said, I want to[br]think about what this tells us 0:01:08.850,0:01:11.740 about the size of the[br]observable universe. 0:01:11.740,0:01:17.320 0:01:17.320,0:01:22.320 So if all of the expansion[br]started 13.7 billion years ago, 0:01:22.320,0:01:25.870 that 13.7 billion[br]years ago, everything 0:01:25.870,0:01:28.320 we know in our[br]three-dimensional universe 0:01:28.320,0:01:31.270 was in a single[br]point, the longest 0:01:31.270,0:01:34.340 that any photon of light could[br]be traveling that's reaching us 0:01:34.340,0:01:39.720 right now-- so let's say that[br]that is my eye right over here. 0:01:39.720,0:01:45.800 That's my eyelashes, just like[br]that-- so some photon of light 0:01:45.800,0:01:47.890 is just to getting to[br]my eye or maybe it's 0:01:47.890,0:01:50.840 just getting to the[br]lens of a telescope. 0:01:50.840,0:01:52.800 The longest that that[br]could have been traveling 0:01:52.800,0:01:55.490 is 13.7 billion years. 0:01:55.490,0:02:07.320 So it could be traveling[br]13.7 billion years. 0:02:07.320,0:02:09.389 So when we looked[br]at that depiction-- 0:02:09.389,0:02:11.250 this I think was two[br]or three videos ago, 0:02:11.250,0:02:14.930 of the observable universe--[br]I drew, it was this circle. 0:02:14.930,0:02:18.270 0:02:18.270,0:02:21.966 And when we see light coming[br]from these remote objects-- 0:02:21.966,0:02:23.590 that light is getting[br]to us right here. 0:02:23.590,0:02:24.850 This is where we are. 0:02:24.850,0:02:27.510 This is where I guess[br]in the depiction 0:02:27.510,0:02:28.800 the remote object was. 0:02:28.800,0:02:30.840 But the light from[br]that remote object 0:02:30.840,0:02:32.930 is just now getting to us. 0:02:32.930,0:02:37.970 And that light took 13.7[br]billion years to get to us. 0:02:37.970,0:02:43.887 0:02:43.887,0:02:45.470 Now, what I'm going[br]to hesitate to do, 0:02:45.470,0:02:48.720 because we're talking[br]over such large distances 0:02:48.720,0:02:51.890 and we're talking on such large[br]time scales and time scales 0:02:51.890,0:02:55.010 over which space[br]itself is expanding-- 0:02:55.010,0:02:59.180 we're going to see in this video[br]that you cannot say that this 0:02:59.180,0:03:03.990 object over here, this is[br]not necessarily, this is NOT, 0:03:03.990,0:03:13.720 I'll put it in caps, this is NOT[br]13.7 billion light years away. 0:03:13.720,0:03:15.990 If we were talking about[br]smaller time scales 0:03:15.990,0:03:18.270 or I guess smaller[br]distances, you 0:03:18.270,0:03:20.060 could say approximately that. 0:03:20.060,0:03:23.784 The expansion of the universe[br]itself would not make as much 0:03:23.784,0:03:24.450 of a difference. 0:03:24.450,0:03:26.870 And let me make it[br]even more clear. 0:03:26.870,0:03:28.720 I'm talking about an[br]object over there. 0:03:28.720,0:03:33.055 But we could even talk about[br]that coordinate in space. 0:03:33.055,0:03:35.430 And actually, I should say[br]that coordinate in space-time, 0:03:35.430,0:03:37.950 because we're viewing it at[br]a certain instant as well. 0:03:37.950,0:03:43.270 But that coordinate is not[br]13.7 billion light years away 0:03:43.270,0:03:44.740 from our current coordinate. 0:03:44.740,0:03:46.520 And there's a couple of[br]reasons to think about it. 0:03:46.520,0:03:48.186 First of all, think[br]about it, that light 0:03:48.186,0:03:51.760 was emitted 13.7[br]billion years ago. 0:03:51.760,0:03:53.840 When that light was[br]emitted, we were 0:03:53.840,0:03:55.750 much closer to that coordinate. 0:03:55.750,0:03:57.637 This coordinate was[br]much closer to that. 0:03:57.637,0:03:59.220 Where we are in the[br]universe right now 0:03:59.220,0:04:01.960 was much closer to that[br]point in the universe. 0:04:01.960,0:04:04.110 The other thing[br]to think about is 0:04:04.110,0:04:06.060 as this-- let me[br]actually draw it. 0:04:06.060,0:04:16.170 So let's go 300,000 years[br]after that initial expansion 0:04:16.170,0:04:17.079 of that singularity. 0:04:17.079,0:04:21.300 So we're just 300,000 years[br]into the universe's history 0:04:21.300,0:04:22.890 right now. 0:04:22.890,0:04:30.370 So this is roughly 300,000[br]years into the universe's life. 0:04:30.370,0:04:33.660 I guess we could[br]view it that way. 0:04:33.660,0:04:37.400 And first of all, at that point[br]things haven't differentiated 0:04:37.400,0:04:39.130 in a meaningful[br]way yet right now. 0:04:39.130,0:04:40.860 And we'll talk more[br]about this when 0:04:40.860,0:04:43.580 we talk about the cosmic[br]microwave background radiation. 0:04:43.580,0:04:45.650 But at this point[br]in the universe, 0:04:45.650,0:04:49.900 it was kind of this almost[br]uniform white-hot plasma 0:04:49.900,0:04:50.400 of hydrogen. 0:04:50.400,0:04:51.983 And then we're going[br]to talk about it. 0:04:51.983,0:04:53.869 It was emitting[br]microwave radiation. 0:04:53.869,0:04:55.910 And we'll talk more about[br]that in a future video. 0:04:55.910,0:05:01.090 But let's just think about two[br]points in this early universe. 0:05:01.090,0:05:03.597 So in this early universe,[br]let's say you have that point. 0:05:03.597,0:05:05.930 And let's say you have the[br]coordinate where we are right 0:05:05.930,0:05:06.890 now. 0:05:06.890,0:05:10.214 You have the coordinate[br]where we are right now. 0:05:10.214,0:05:12.630 And in fact, I'll just make[br]that roughly-- I won't make it 0:05:12.630,0:05:14.340 the center just because I[br]think it makes it easier 0:05:14.340,0:05:15.950 to visualize if[br]it's not the center. 0:05:15.950,0:05:19.080 And let's say at that very[br]early stage in the universe, 0:05:19.080,0:05:22.090 if you were able to just take[br]some rulers instantaneously 0:05:22.090,0:05:26.820 and measure that, you[br]would measure this distance 0:05:26.820,0:05:36.150 to be 30 million light years. 0:05:36.150,0:05:38.050 And let's just say[br]right at that point, 0:05:38.050,0:05:40.140 this object over here--[br]I'll do it in magenta-- 0:05:40.140,0:05:43.070 this object over here[br]emits a photon, maybe 0:05:43.070,0:05:45.787 in the microwave[br]frequency range. 0:05:45.787,0:05:48.370 And we'll see that that was the[br]range that it was emitting in. 0:05:48.370,0:05:50.216 But it emits a photon. 0:05:50.216,0:05:52.340 And that photon is traveling[br]at the speed of light. 0:05:52.340,0:05:53.182 It is light. 0:05:53.182,0:05:55.140 And so that photon, says,[br]you know what, I only 0:05:55.140,0:05:56.990 got 30 million light[br]years to travel. 0:05:56.990,0:05:57.790 That's not too bad. 0:05:57.790,0:06:00.647 I'm going to get there[br]in 30 million years. 0:06:00.647,0:06:01.980 And I'm going to do it discrete. 0:06:01.980,0:06:04.380 The math is more complicated[br]than what I'm doing here. 0:06:04.380,0:06:05.796 But I really just[br]want to give you 0:06:05.796,0:06:07.320 the idea of what's[br]going on here. 0:06:07.320,0:06:09.840 So let's just say,[br]well, that photon 0:06:09.840,0:06:13.870 says in about 10 million years,[br]in roughly 10 million years, 0:06:13.870,0:06:18.080 I should be right about[br]at that coordinate. 0:06:18.080,0:06:20.960 I should be about one[br]third of the distance. 0:06:20.960,0:06:26.080 But what happens over the course[br]of those 10 million years? 0:06:26.080,0:06:28.080 Well, over the course of[br]those 10 million years, 0:06:28.080,0:06:30.240 the universe has expanded some. 0:06:30.240,0:06:32.730 The universe has expanded[br]maybe a good deal. 0:06:32.730,0:06:35.690 So let me draw the[br]expanded universe. 0:06:35.690,0:06:40.919 So after 10 million years, the[br]universe might look like this. 0:06:40.919,0:06:42.710 Actually it might even[br]be bigger than that. 0:06:42.710,0:06:44.760 Let me draw it like this. 0:06:44.760,0:06:47.570 After 10 million[br]years, the universe 0:06:47.570,0:06:49.510 might have expanded a good bit. 0:06:49.510,0:06:53.470 So this is 10 million[br]years into the future. 0:06:53.470,0:06:58.200 Still on a cosmological time[br]scale, still almost at kind 0:06:58.200,0:07:00.370 of the infancy of the[br]universe because we're 0:07:00.370,0:07:02.360 talking about 13.7[br]billion years. 0:07:02.360,0:07:04.310 So let's say 10 million years. 0:07:04.310,0:07:07.510 10 million years go by. 0:07:07.510,0:07:09.100 The universe has expanded. 0:07:09.100,0:07:10.980 This coordinate, where[br]we're sitting today 0:07:10.980,0:07:15.350 at the present time, is[br]now all the way over here. 0:07:15.350,0:07:19.350 That coordinate where the[br]photon was originally emitted 0:07:19.350,0:07:24.302 is now going to be[br]sitting right over here. 0:07:24.302,0:07:26.760 And that photon, it said, OK,[br]after 10 million light years, 0:07:26.760,0:07:28.100 I'm going to get over there. 0:07:28.100,0:07:29.300 And I'm approximating. 0:07:29.300,0:07:30.800 I'm doing it in a[br]very discrete way. 0:07:30.800,0:07:32.890 But I really just want[br]to give you the idea. 0:07:32.890,0:07:35.280 So that coordinate,[br]where the photon roughly 0:07:35.280,0:07:38.340 gets in 10 million light years,[br]is about right over here. 0:07:38.340,0:07:39.760 The whole universe has expanded. 0:07:39.760,0:07:42.860 All the coordinates have gotten[br]further away from each other. 0:07:42.860,0:07:44.180 Now, what just happened here? 0:07:44.180,0:07:45.420 The universe has expanded. 0:07:45.420,0:07:49.240 This distance that was 30[br]million light years now-- 0:07:49.240,0:07:52.000 and I'm just making[br]rough numbers here. 0:07:52.000,0:07:53.640 I don't know the[br]actual numbers here. 0:07:53.640,0:07:55.690 Now, it is actually--[br]this is really just 0:07:55.690,0:08:01.130 for the sake of giving you the[br]idea of why-- well, giving you 0:08:01.130,0:08:03.100 the intuition of[br]what's going on. 0:08:03.100,0:08:08.180 This distance now is no[br]longer 30 million light years. 0:08:08.180,0:08:10.240 Maybe it's 100 million. 0:08:10.240,0:08:16.167 So this is now 100 million light[br]years away from each other. 0:08:16.167,0:08:17.250 The universe is expanding. 0:08:17.250,0:08:20.909 These coordinates, the space[br]is actually spreading out. 0:08:20.909,0:08:22.700 You could imagine it's[br]kind of a trampoline 0:08:22.700,0:08:23.866 or the surface of a balloon. 0:08:23.866,0:08:25.490 It's getting stretched thin. 0:08:25.490,0:08:27.640 And so this coordinate[br]where the light happens 0:08:27.640,0:08:29.940 to be after 10[br]million years, it has 0:08:29.940,0:08:32.179 been traveling for[br]10 million years, 0:08:32.179,0:08:33.824 but it's gone a much[br]larger distance. 0:08:33.824,0:08:37.539 0:08:37.539,0:08:40.440 That distance now might[br]be on the order of-- maybe 0:08:40.440,0:08:42.510 it's on the order of[br]30 million light years. 0:08:42.510,0:08:44.100 And the math isn't exact here. 0:08:44.100,0:08:47.620 I haven't done the[br]math to figure it out. 0:08:47.620,0:08:50.360 So it's done 30[br]million light years. 0:08:50.360,0:08:53.900 And actually I shouldn't even[br]make it the same proportion. 0:08:53.900,0:08:56.592 Because the distance it's gone[br]and the distance it has to go, 0:08:56.592,0:08:58.050 because of the[br]stretching, it's not 0:08:58.050,0:08:59.714 going to be completely linear. 0:08:59.714,0:09:02.380 At least when I'm thinking about[br]it in my head, it shouldn't be, 0:09:02.380,0:09:02.960 I think. 0:09:02.960,0:09:06.340 But I'm going to make a[br]hard statement about that. 0:09:06.340,0:09:10.500 But the distance that it[br]reversed, maybe this distance 0:09:10.500,0:09:15.790 right here is now 20[br]million light years 0:09:15.790,0:09:16.920 because it got there. 0:09:16.920,0:09:20.960 Every time it moved some[br]distance, the space that it 0:09:20.960,0:09:23.020 had traversed is now stretched. 0:09:23.020,0:09:27.660 So even though its traveled[br]for 10 million years, 0:09:27.660,0:09:29.640 the space that it[br]traversed is no longer 0:09:29.640,0:09:31.360 just 10 million light years. 0:09:31.360,0:09:34.130 It's now stretched to[br]20 million light years. 0:09:34.130,0:09:35.890 And the space that it[br]has left to traverse 0:09:35.890,0:09:38.570 is no longer only 20[br]million light years. 0:09:38.570,0:09:41.420 It might now be 80[br]million light years. 0:09:41.420,0:09:44.410 It is now 80[br]million light years. 0:09:44.410,0:09:47.060 And so this photon might[br]be getting frustrated. 0:09:47.060,0:09:48.880 There's an optimistic[br]way of viewing it. 0:09:48.880,0:09:50.670 It is like, wow, I[br]was able to cover 0:09:50.670,0:09:53.387 20 million light years[br]in only 10 million years. 0:09:53.387,0:09:55.720 It looks like I'm moving[br]faster than the speed of light. 0:09:55.720,0:09:58.270 The reality is it's not[br]because the space coordinates 0:09:58.270,0:10:00.610 themselves are spreading out. 0:10:00.610,0:10:01.630 Those are getting thin. 0:10:01.630,0:10:04.496 So the photon is just moving[br]at the speed of light. 0:10:04.496,0:10:05.870 But the distance[br]that it actually 0:10:05.870,0:10:10.090 traversed in 10 million[br]years is more than 10 million 0:10:10.090,0:10:10.590 light years. 0:10:10.590,0:10:12.090 It's 20 million light years. 0:10:12.090,0:10:15.480 So you can't just[br]multiply a rate times time 0:10:15.480,0:10:19.090 on these cosmological scales,[br]especially when the coordinates 0:10:19.090,0:10:23.100 themselves, the distance[br]coordinates are actually 0:10:23.100,0:10:24.690 moving away from each other. 0:10:24.690,0:10:27.430 But I think you see,[br]or maybe you might see, 0:10:27.430,0:10:29.520 where this is going. 0:10:29.520,0:10:33.150 OK, this photon says, oh, in[br]another-- let me write this. 0:10:33.150,0:10:35.430 This is 80 million light[br]years-- in another 40 million 0:10:35.430,0:10:40.190 light years, maybe I'm[br]going to get over here. 0:10:40.190,0:10:43.110 But the reality is over that[br]next 40 million light years-- 0:10:43.110,0:10:47.440 sorry, in 40 million years,[br]I might get right over here, 0:10:47.440,0:10:49.650 because this is 80[br]million light years. 0:10:49.650,0:10:52.420 But the reality is[br]after 40 million years-- 0:10:52.420,0:10:56.030 so another 40 million years[br]go by-- now, all of a sudden, 0:10:56.030,0:10:59.750 the universe has[br]expanded even more. 0:10:59.750,0:11:01.710 I won't even draw[br]the whole bubble. 0:11:01.710,0:11:04.680 But the place where the[br]photon was emitted from 0:11:04.680,0:11:07.630 might be over here. 0:11:07.630,0:11:11.850 And now our current[br]position is over here. 0:11:11.850,0:11:18.250 Where the light got after 10[br]million years is now over here. 0:11:18.250,0:11:24.070 And now, where the light[br]is after 40 million years, 0:11:24.070,0:11:27.500 maybe it's over here. 0:11:27.500,0:11:29.520 So now this distance,[br]the distance 0:11:29.520,0:11:32.240 between these two[br]points, when we started, 0:11:32.240,0:11:33.590 it was 10 million light years. 0:11:33.590,0:11:36.380 Then it became 20[br]million light years. 0:11:36.380,0:11:39.100 Maybe now, it's on the order[br]of-- I don't know-- maybe it's 0:11:39.100,0:11:41.140 a billion light years. 0:11:41.140,0:11:43.240 Maybe now it's a[br]billion light years. 0:11:43.240,0:11:45.512 And maybe this distance[br]over here-- and I'm 0:11:45.512,0:11:46.720 just making up these numbers. 0:11:46.720,0:11:49.450 In fact, that's probably be too[br]big for that point-- maybe this 0:11:49.450,0:11:52.010 is now 100 million light years. 0:11:52.010,0:11:55.390 This is now 100[br]million light years. 0:11:55.390,0:11:59.050 And now, maybe[br]this distance right 0:11:59.050,0:12:01.730 here is-- I don't know--[br]500 million light years. 0:12:01.730,0:12:04.080 And maybe now the total[br]distance between the two points 0:12:04.080,0:12:05.950 is a billion light years. 0:12:05.950,0:12:08.730 So as you can see, the photon[br]might getting frustrated. 0:12:08.730,0:12:10.230 As it covers more[br]and more distance, 0:12:10.230,0:12:13.200 it looks back and says, wow,[br]in only 50 million years, 0:12:13.200,0:12:16.020 I've been able to cover[br]600 million light years. 0:12:16.020,0:12:16.910 That's pretty good. 0:12:16.910,0:12:18.701 But it's frustrated[br]because what it thought 0:12:18.701,0:12:22.510 was it only had to cover[br]30 million light years 0:12:22.510,0:12:23.050 in distance. 0:12:23.050,0:12:25.070 That keeps stretching[br]out because space 0:12:25.070,0:12:26.560 itself is stretching. 0:12:26.560,0:12:32.190 So the reality, just going[br]to the original idea, 0:12:32.190,0:12:36.050 this photon that is[br]just reaching us, 0:12:36.050,0:12:38.870 that's been traveling[br]for-- let's say 0:12:38.870,0:12:41.690 it's been traveling[br]for 13.4 billion years. 0:12:41.690,0:12:43.180 So it's reaching us is just now. 0:12:43.180,0:12:46.690 So let me just fast[br]forward 13.4 billion years 0:12:46.690,0:12:49.620 from this point now to[br]get to the present day. 0:12:49.620,0:12:54.842 So if I draw the whole visible[br]universe right over here, 0:12:54.842,0:12:56.300 this point right[br]over here is going 0:12:56.300,0:13:00.340 to be-- where it was emitted[br]from is right over there. 0:13:00.340,0:13:04.890 We are sitting right over there. 0:13:04.890,0:13:06.640 And actually, let me[br]make something clear. 0:13:06.640,0:13:08.770 If I'm drawing the whole[br]observable universe, 0:13:08.770,0:13:10.922 the center actually[br]should be where we are. 0:13:10.922,0:13:12.630 Because we can observe[br]an equal distance. 0:13:12.630,0:13:14.640 If things aren't[br]really strange, we 0:13:14.640,0:13:16.620 can observe an equal[br]distance in any direction. 0:13:16.620,0:13:19.210 So actually maybe we should[br]put us at the center. 0:13:19.210,0:13:21.650 So if this was the entire[br]observable universe, 0:13:21.650,0:13:26.180 and the photon was emitted from[br]here 13.4 billion years ago-- 0:13:26.180,0:13:29.800 so 300,000 years after[br]that initial Big Bang, 0:13:29.800,0:13:35.620 and it's just getting[br]to us, it is true 0:13:35.620,0:13:41.150 that the photon[br]has been traveling 0:13:41.150,0:13:47.050 for 13.7 billion years. 0:13:47.050,0:13:50.900 But what's kind of nutty about[br]it is this object, since we've 0:13:50.900,0:13:53.970 been expanding away from each[br]other, this object is now, 0:13:53.970,0:13:56.180 in our best[br]estimates, this object 0:13:56.180,0:14:06.420 is going to be about 46 billion[br]light years away from us. 0:14:06.420,0:14:08.785 0:14:08.785,0:14:10.160 And I want to make[br]it very clear. 0:14:10.160,0:14:13.220 This object is now 46 billion[br]light years away from us. 0:14:13.220,0:14:16.781 When we just use light to[br]observe it, it looks like, 0:14:16.781,0:14:18.530 just based on light[br]years, hey, this light 0:14:18.530,0:14:21.280 has been traveling 13.7[br]billion years to reach us. 0:14:21.280,0:14:22.981 That's our only way[br]of kind with light 0:14:22.981,0:14:24.480 to kind of think[br]about the distance. 0:14:24.480,0:14:27.740 So maybe it's 13.4[br]or whatever-- I 0:14:27.740,0:14:31.340 keep changing the decimal-- but[br]13.4 billion light years away. 0:14:31.340,0:14:36.600 But the reality is if you had a[br]ruler today, light year rulers, 0:14:36.600,0:14:38.570 this space here has[br]stretched so much 0:14:38.570,0:14:41.702 that this is now 46[br]billion light years. 0:14:41.702,0:14:43.160 And just to give[br]you a hint of when 0:14:43.160,0:14:45.100 we talk about the cosmic[br]microwave background 0:14:45.100,0:14:47.959 radiation, what will[br]this point in space 0:14:47.959,0:14:49.500 look like, this[br]thing that's actually 0:14:49.500,0:14:52.010 46 billion light years[br]away, but the photon only 0:14:52.010,0:14:54.540 took 13.7 billion[br]years to reach us? 0:14:54.540,0:14:56.120 What will this look like? 0:14:56.120,0:14:59.610 Well, when we say[br]look like, it's 0:14:59.610,0:15:02.340 based on the photons that[br]are reaching us right now. 0:15:02.340,0:15:05.350 Those photons left[br]13.4 billion years ago. 0:15:05.350,0:15:07.090 So those photons are[br]the photons being 0:15:07.090,0:15:10.040 emitted from this[br]primitive structure, 0:15:10.040,0:15:16.460 from this white-hot[br]haze of hydrogen plasma. 0:15:16.460,0:15:19.240 So what we're going to see[br]is this white-hot haze. 0:15:19.240,0:15:26.930 So we're going to see this kind[br]of white-hot plasma, white hot, 0:15:26.930,0:15:28.790 undifferentiated[br]not differentiated 0:15:28.790,0:15:32.550 into proper stable atoms,[br]much less stars and galaxies, 0:15:32.550,0:15:33.710 but white hot. 0:15:33.710,0:15:36.220 We're going to see[br]this white-hot plasma. 0:15:36.220,0:15:38.640 The reality today is[br]that point in space 0:15:38.640,0:15:40.190 that's 46 billion[br]years from now, 0:15:40.190,0:15:45.160 it's probably differentiated[br]into stable atoms, and stars, 0:15:45.160,0:15:46.780 and planets, and galaxies. 0:15:46.780,0:15:49.020 And frankly, if that[br]person, that person, 0:15:49.020,0:15:51.210 if there is a civilization[br]there right now 0:15:51.210,0:15:52.700 and if they're sitting right[br]there, and they're observing 0:15:52.700,0:15:54.610 photons being emitted[br]from our coordinate, 0:15:54.610,0:15:56.530 from our point in[br]space right now, 0:15:56.530,0:15:57.920 they're not going to see us. 0:15:57.920,0:16:01.810 They're going to see us[br]13.4 billion years ago. 0:16:01.810,0:16:05.140 They're going to see the[br]super primitive state 0:16:05.140,0:16:07.310 of our region of[br]space when it really 0:16:07.310,0:16:09.164 was just a white-hot plasma. 0:16:09.164,0:16:11.580 And we're going to talk more[br]about this in the next video. 0:16:11.580,0:16:12.700 But think about it. 0:16:12.700,0:16:15.510 Any photon that's coming[br]from that period in time, 0:16:15.510,0:16:17.670 so from any direction,[br]that's been traveling 0:16:17.670,0:16:21.170 for 13.4 billion years[br]from any direction, 0:16:21.170,0:16:23.720 it's going to come from[br]that primitive state 0:16:23.720,0:16:27.390 or it would have been[br]emitted when the universe was 0:16:27.390,0:16:29.580 in that primitive[br]state, when it was just 0:16:29.580,0:16:32.195 that white-hot plasma,[br]this undifferentiated mass. 0:16:32.195,0:16:33.570 And hopefully,[br]that will give you 0:16:33.570,0:16:36.480 a sense of where the[br]cosmic microwave background 0:16:36.480,0:16:38.920 radiation comes from.