1 00:00:00,000 --> 00:00:00,540 2 00:00:00,540 --> 00:00:05,594 Right now, the best estimate of when the Big Bang occurred-- 3 00:00:05,594 --> 00:00:08,010 and once again, I don't like the term that much because it 4 00:00:08,010 --> 00:00:10,255 kind of implies some type of explosion. 5 00:00:10,255 --> 00:00:12,130 But what it really is is kind of an expansion 6 00:00:12,130 --> 00:00:14,540 of space, when space started to really start 7 00:00:14,540 --> 00:00:16,420 to expand from a singularity. 8 00:00:16,420 --> 00:00:18,400 But our best estimate of when this occurred 9 00:00:18,400 --> 00:00:24,320 is 13.7 billion years ago. 10 00:00:24,320 --> 00:00:26,672 And even though we're used to dealing with numbers 11 00:00:26,672 --> 00:00:28,130 in the billions, especially when we 12 00:00:28,130 --> 00:00:30,540 talk about large amounts of money and what not, 13 00:00:30,540 --> 00:00:32,750 this is an unbelievable amount of time. 14 00:00:32,750 --> 00:00:35,580 It seems like something that is tractable, but it really isn't. 15 00:00:35,580 --> 00:00:37,830 And in future videos, I'm actually 16 00:00:37,830 --> 00:00:39,420 going to talk about the time scale. 17 00:00:39,420 --> 00:00:41,340 So we can really appreciate how long, 18 00:00:41,340 --> 00:00:43,170 or even start to appreciate, or appreciate 19 00:00:43,170 --> 00:00:47,820 that we can't appreciate how long 13.7 billion years is. 20 00:00:47,820 --> 00:00:51,510 And I also want to emphasize that this is the current best 21 00:00:51,510 --> 00:00:52,010 estimate. 22 00:00:52,010 --> 00:00:54,760 Even in my lifetime, even in my lifetime that I actually 23 00:00:54,760 --> 00:00:57,230 knew about the Big Bang and that I would pay attention 24 00:00:57,230 --> 00:00:59,360 to what the best estimate was, this number's 25 00:00:59,360 --> 00:01:00,260 been moving around. 26 00:01:00,260 --> 00:01:02,320 So I suspect that in the future, this number 27 00:01:02,320 --> 00:01:04,989 might become more accurate or might move around some. 28 00:01:04,989 --> 00:01:06,350 But this is our best guess. 29 00:01:06,350 --> 00:01:08,850 Now with that said, I want to think about what this tells us 30 00:01:08,850 --> 00:01:11,740 about the size of the observable universe. 31 00:01:11,740 --> 00:01:17,320 32 00:01:17,320 --> 00:01:22,320 So if all of the expansion started 13.7 billion years ago, 33 00:01:22,320 --> 00:01:25,870 that 13.7 billion years ago, everything 34 00:01:25,870 --> 00:01:28,320 we know in our three-dimensional universe 35 00:01:28,320 --> 00:01:31,270 was in a single point, the longest 36 00:01:31,270 --> 00:01:34,340 that any photon of light could be traveling that's reaching us 37 00:01:34,340 --> 00:01:39,720 right now-- so let's say that that is my eye right over here. 38 00:01:39,720 --> 00:01:45,800 That's my eyelashes, just like that-- so some photon of light 39 00:01:45,800 --> 00:01:47,890 is just to getting to my eye or maybe it's 40 00:01:47,890 --> 00:01:50,840 just getting to the lens of a telescope. 41 00:01:50,840 --> 00:01:52,800 The longest that that could have been traveling 42 00:01:52,800 --> 00:01:55,490 is 13.7 billion years. 43 00:01:55,490 --> 00:02:07,320 So it could be traveling 13.7 billion years. 44 00:02:07,320 --> 00:02:09,389 So when we looked at that depiction-- 45 00:02:09,389 --> 00:02:11,250 this I think was two or three videos ago, 46 00:02:11,250 --> 00:02:14,930 of the observable universe-- I drew, it was this circle. 47 00:02:14,930 --> 00:02:18,270 48 00:02:18,270 --> 00:02:21,966 And when we see light coming from these remote objects-- 49 00:02:21,966 --> 00:02:23,590 that light is getting to us right here. 50 00:02:23,590 --> 00:02:24,850 This is where we are. 51 00:02:24,850 --> 00:02:27,510 This is where I guess in the depiction 52 00:02:27,510 --> 00:02:28,800 the remote object was. 53 00:02:28,800 --> 00:02:30,840 But the light from that remote object 54 00:02:30,840 --> 00:02:32,930 is just now getting to us. 55 00:02:32,930 --> 00:02:37,970 And that light took 13.7 billion years to get to us. 56 00:02:37,970 --> 00:02:43,887 57 00:02:43,887 --> 00:02:45,470 Now, what I'm going to hesitate to do, 58 00:02:45,470 --> 00:02:48,720 because we're talking over such large distances 59 00:02:48,720 --> 00:02:51,890 and we're talking on such large time scales and time scales 60 00:02:51,890 --> 00:02:55,010 over which space itself is expanding-- 61 00:02:55,010 --> 00:02:59,180 we're going to see in this video that you cannot say that this 62 00:02:59,180 --> 00:03:03,990 object over here, this is not necessarily, this is NOT, 63 00:03:03,990 --> 00:03:13,720 I'll put it in caps, this is NOT 13.7 billion light years away. 64 00:03:13,720 --> 00:03:15,990 If we were talking about smaller time scales 65 00:03:15,990 --> 00:03:18,270 or I guess smaller distances, you 66 00:03:18,270 --> 00:03:20,060 could say approximately that. 67 00:03:20,060 --> 00:03:23,784 The expansion of the universe itself would not make as much 68 00:03:23,784 --> 00:03:24,450 of a difference. 69 00:03:24,450 --> 00:03:26,870 And let me make it even more clear. 70 00:03:26,870 --> 00:03:28,720 I'm talking about an object over there. 71 00:03:28,720 --> 00:03:33,055 But we could even talk about that coordinate in space. 72 00:03:33,055 --> 00:03:35,430 And actually, I should say that coordinate in space-time, 73 00:03:35,430 --> 00:03:37,950 because we're viewing it at a certain instant as well. 74 00:03:37,950 --> 00:03:43,270 But that coordinate is not 13.7 billion light years away 75 00:03:43,270 --> 00:03:44,740 from our current coordinate. 76 00:03:44,740 --> 00:03:46,520 And there's a couple of reasons to think about it. 77 00:03:46,520 --> 00:03:48,186 First of all, think about it, that light 78 00:03:48,186 --> 00:03:51,760 was emitted 13.7 billion years ago. 79 00:03:51,760 --> 00:03:53,840 When that light was emitted, we were 80 00:03:53,840 --> 00:03:55,750 much closer to that coordinate. 81 00:03:55,750 --> 00:03:57,637 This coordinate was much closer to that. 82 00:03:57,637 --> 00:03:59,220 Where we are in the universe right now 83 00:03:59,220 --> 00:04:01,960 was much closer to that point in the universe. 84 00:04:01,960 --> 00:04:04,110 The other thing to think about is 85 00:04:04,110 --> 00:04:06,060 as this-- let me actually draw it. 86 00:04:06,060 --> 00:04:16,170 So let's go 300,000 years after that initial expansion 87 00:04:16,170 --> 00:04:17,079 of that singularity. 88 00:04:17,079 --> 00:04:21,300 So we're just 300,000 years into the universe's history 89 00:04:21,300 --> 00:04:22,890 right now. 90 00:04:22,890 --> 00:04:30,370 So this is roughly 300,000 years into the universe's life. 91 00:04:30,370 --> 00:04:33,660 I guess we could view it that way. 92 00:04:33,660 --> 00:04:37,400 And first of all, at that point things haven't differentiated 93 00:04:37,400 --> 00:04:39,130 in a meaningful way yet right now. 94 00:04:39,130 --> 00:04:40,860 And we'll talk more about this when 95 00:04:40,860 --> 00:04:43,580 we talk about the cosmic microwave background radiation. 96 00:04:43,580 --> 00:04:45,650 But at this point in the universe, 97 00:04:45,650 --> 00:04:49,900 it was kind of this almost uniform white-hot plasma 98 00:04:49,900 --> 00:04:50,400 of hydrogen. 99 00:04:50,400 --> 00:04:51,983 And then we're going to talk about it. 100 00:04:51,983 --> 00:04:53,869 It was emitting microwave radiation. 101 00:04:53,869 --> 00:04:55,910 And we'll talk more about that in a future video. 102 00:04:55,910 --> 00:05:01,090 But let's just think about two points in this early universe. 103 00:05:01,090 --> 00:05:03,597 So in this early universe, let's say you have that point. 104 00:05:03,597 --> 00:05:05,930 And let's say you have the coordinate where we are right 105 00:05:05,930 --> 00:05:06,890 now. 106 00:05:06,890 --> 00:05:10,214 You have the coordinate where we are right now. 107 00:05:10,214 --> 00:05:12,630 And in fact, I'll just make that roughly-- I won't make it 108 00:05:12,630 --> 00:05:14,340 the center just because I think it makes it easier 109 00:05:14,340 --> 00:05:15,950 to visualize if it's not the center. 110 00:05:15,950 --> 00:05:19,080 And let's say at that very early stage in the universe, 111 00:05:19,080 --> 00:05:22,090 if you were able to just take some rulers instantaneously 112 00:05:22,090 --> 00:05:26,820 and measure that, you would measure this distance 113 00:05:26,820 --> 00:05:36,150 to be 30 million light years. 114 00:05:36,150 --> 00:05:38,050 And let's just say right at that point, 115 00:05:38,050 --> 00:05:40,140 this object over here-- I'll do it in magenta-- 116 00:05:40,140 --> 00:05:43,070 this object over here emits a photon, maybe 117 00:05:43,070 --> 00:05:45,787 in the microwave frequency range. 118 00:05:45,787 --> 00:05:48,370 And we'll see that that was the range that it was emitting in. 119 00:05:48,370 --> 00:05:50,216 But it emits a photon. 120 00:05:50,216 --> 00:05:52,340 And that photon is traveling at the speed of light. 121 00:05:52,340 --> 00:05:53,182 It is light. 122 00:05:53,182 --> 00:05:55,140 And so that photon, says, you know what, I only 123 00:05:55,140 --> 00:05:56,990 got 30 million light years to travel. 124 00:05:56,990 --> 00:05:57,790 That's not too bad. 125 00:05:57,790 --> 00:06:00,647 I'm going to get there in 30 million years. 126 00:06:00,647 --> 00:06:01,980 And I'm going to do it discrete. 127 00:06:01,980 --> 00:06:04,380 The math is more complicated than what I'm doing here. 128 00:06:04,380 --> 00:06:05,796 But I really just want to give you 129 00:06:05,796 --> 00:06:07,320 the idea of what's going on here. 130 00:06:07,320 --> 00:06:09,840 So let's just say, well, that photon 131 00:06:09,840 --> 00:06:13,870 says in about 10 million years, in roughly 10 million years, 132 00:06:13,870 --> 00:06:18,080 I should be right about at that coordinate. 133 00:06:18,080 --> 00:06:20,960 I should be about one third of the distance. 134 00:06:20,960 --> 00:06:26,080 But what happens over the course of those 10 million years? 135 00:06:26,080 --> 00:06:28,080 Well, over the course of those 10 million years, 136 00:06:28,080 --> 00:06:30,240 the universe has expanded some. 137 00:06:30,240 --> 00:06:32,730 The universe has expanded maybe a good deal. 138 00:06:32,730 --> 00:06:35,690 So let me draw the expanded universe. 139 00:06:35,690 --> 00:06:40,919 So after 10 million years, the universe might look like this. 140 00:06:40,919 --> 00:06:42,710 Actually it might even be bigger than that. 141 00:06:42,710 --> 00:06:44,760 Let me draw it like this. 142 00:06:44,760 --> 00:06:47,570 After 10 million years, the universe 143 00:06:47,570 --> 00:06:49,510 might have expanded a good bit. 144 00:06:49,510 --> 00:06:53,470 So this is 10 million years into the future. 145 00:06:53,470 --> 00:06:58,200 Still on a cosmological time scale, still almost at kind 146 00:06:58,200 --> 00:07:00,370 of the infancy of the universe because we're 147 00:07:00,370 --> 00:07:02,360 talking about 13.7 billion years. 148 00:07:02,360 --> 00:07:04,310 So let's say 10 million years. 149 00:07:04,310 --> 00:07:07,510 10 million years go by. 150 00:07:07,510 --> 00:07:09,100 The universe has expanded. 151 00:07:09,100 --> 00:07:10,980 This coordinate, where we're sitting today 152 00:07:10,980 --> 00:07:15,350 at the present time, is now all the way over here. 153 00:07:15,350 --> 00:07:19,350 That coordinate where the photon was originally emitted 154 00:07:19,350 --> 00:07:24,302 is now going to be sitting right over here. 155 00:07:24,302 --> 00:07:26,760 And that photon, it said, OK, after 10 million light years, 156 00:07:26,760 --> 00:07:28,100 I'm going to get over there. 157 00:07:28,100 --> 00:07:29,300 And I'm approximating. 158 00:07:29,300 --> 00:07:30,800 I'm doing it in a very discrete way. 159 00:07:30,800 --> 00:07:32,890 But I really just want to give you the idea. 160 00:07:32,890 --> 00:07:35,280 So that coordinate, where the photon roughly 161 00:07:35,280 --> 00:07:38,340 gets in 10 million light years, is about right over here. 162 00:07:38,340 --> 00:07:39,760 The whole universe has expanded. 163 00:07:39,760 --> 00:07:42,860 All the coordinates have gotten further away from each other. 164 00:07:42,860 --> 00:07:44,180 Now, what just happened here? 165 00:07:44,180 --> 00:07:45,420 The universe has expanded. 166 00:07:45,420 --> 00:07:49,240 This distance that was 30 million light years now-- 167 00:07:49,240 --> 00:07:52,000 and I'm just making rough numbers here. 168 00:07:52,000 --> 00:07:53,640 I don't know the actual numbers here. 169 00:07:53,640 --> 00:07:55,690 Now, it is actually-- this is really just 170 00:07:55,690 --> 00:08:01,130 for the sake of giving you the idea of why-- well, giving you 171 00:08:01,130 --> 00:08:03,100 the intuition of what's going on. 172 00:08:03,100 --> 00:08:08,180 This distance now is no longer 30 million light years. 173 00:08:08,180 --> 00:08:10,240 Maybe it's 100 million. 174 00:08:10,240 --> 00:08:16,167 So this is now 100 million light years away from each other. 175 00:08:16,167 --> 00:08:17,250 The universe is expanding. 176 00:08:17,250 --> 00:08:20,909 These coordinates, the space is actually spreading out. 177 00:08:20,909 --> 00:08:22,700 You could imagine it's kind of a trampoline 178 00:08:22,700 --> 00:08:23,866 or the surface of a balloon. 179 00:08:23,866 --> 00:08:25,490 It's getting stretched thin. 180 00:08:25,490 --> 00:08:27,640 And so this coordinate where the light happens 181 00:08:27,640 --> 00:08:29,940 to be after 10 million years, it has 182 00:08:29,940 --> 00:08:32,179 been traveling for 10 million years, 183 00:08:32,179 --> 00:08:33,824 but it's gone a much larger distance. 184 00:08:33,824 --> 00:08:37,539 185 00:08:37,539 --> 00:08:40,440 That distance now might be on the order of-- maybe 186 00:08:40,440 --> 00:08:42,510 it's on the order of 30 million light years. 187 00:08:42,510 --> 00:08:44,100 And the math isn't exact here. 188 00:08:44,100 --> 00:08:47,620 I haven't done the math to figure it out. 189 00:08:47,620 --> 00:08:50,360 So it's done 30 million light years. 190 00:08:50,360 --> 00:08:53,900 And actually I shouldn't even make it the same proportion. 191 00:08:53,900 --> 00:08:56,592 Because the distance it's gone and the distance it has to go, 192 00:08:56,592 --> 00:08:58,050 because of the stretching, it's not 193 00:08:58,050 --> 00:08:59,714 going to be completely linear. 194 00:08:59,714 --> 00:09:02,380 At least when I'm thinking about it in my head, it shouldn't be, 195 00:09:02,380 --> 00:09:02,960 I think. 196 00:09:02,960 --> 00:09:06,340 But I'm going to make a hard statement about that. 197 00:09:06,340 --> 00:09:10,500 But the distance that it reversed, maybe this distance 198 00:09:10,500 --> 00:09:15,790 right here is now 20 million light years 199 00:09:15,790 --> 00:09:16,920 because it got there. 200 00:09:16,920 --> 00:09:20,960 Every time it moved some distance, the space that it 201 00:09:20,960 --> 00:09:23,020 had traversed is now stretched. 202 00:09:23,020 --> 00:09:27,660 So even though its traveled for 10 million years, 203 00:09:27,660 --> 00:09:29,640 the space that it traversed is no longer 204 00:09:29,640 --> 00:09:31,360 just 10 million light years. 205 00:09:31,360 --> 00:09:34,130 It's now stretched to 20 million light years. 206 00:09:34,130 --> 00:09:35,890 And the space that it has left to traverse 207 00:09:35,890 --> 00:09:38,570 is no longer only 20 million light years. 208 00:09:38,570 --> 00:09:41,420 It might now be 80 million light years. 209 00:09:41,420 --> 00:09:44,410 It is now 80 million light years. 210 00:09:44,410 --> 00:09:47,060 And so this photon might be getting frustrated. 211 00:09:47,060 --> 00:09:48,880 There's an optimistic way of viewing it. 212 00:09:48,880 --> 00:09:50,670 It is like, wow, I was able to cover 213 00:09:50,670 --> 00:09:53,387 20 million light years in only 10 million years. 214 00:09:53,387 --> 00:09:55,720 It looks like I'm moving faster than the speed of light. 215 00:09:55,720 --> 00:09:58,270 The reality is it's not because the space coordinates 216 00:09:58,270 --> 00:10:00,610 themselves are spreading out. 217 00:10:00,610 --> 00:10:01,630 Those are getting thin. 218 00:10:01,630 --> 00:10:04,496 So the photon is just moving at the speed of light. 219 00:10:04,496 --> 00:10:05,870 But the distance that it actually 220 00:10:05,870 --> 00:10:10,090 traversed in 10 million years is more than 10 million 221 00:10:10,090 --> 00:10:10,590 light years. 222 00:10:10,590 --> 00:10:12,090 It's 20 million light years. 223 00:10:12,090 --> 00:10:15,480 So you can't just multiply a rate times time 224 00:10:15,480 --> 00:10:19,090 on these cosmological scales, especially when the coordinates 225 00:10:19,090 --> 00:10:23,100 themselves, the distance coordinates are actually 226 00:10:23,100 --> 00:10:24,690 moving away from each other. 227 00:10:24,690 --> 00:10:27,430 But I think you see, or maybe you might see, 228 00:10:27,430 --> 00:10:29,520 where this is going. 229 00:10:29,520 --> 00:10:33,150 OK, this photon says, oh, in another-- let me write this. 230 00:10:33,150 --> 00:10:35,430 This is 80 million light years-- in another 40 million 231 00:10:35,430 --> 00:10:40,190 light years, maybe I'm going to get over here. 232 00:10:40,190 --> 00:10:43,110 But the reality is over that next 40 million light years-- 233 00:10:43,110 --> 00:10:47,440 sorry, in 40 million years, I might get right over here, 234 00:10:47,440 --> 00:10:49,650 because this is 80 million light years. 235 00:10:49,650 --> 00:10:52,420 But the reality is after 40 million years-- 236 00:10:52,420 --> 00:10:56,030 so another 40 million years go by-- now, all of a sudden, 237 00:10:56,030 --> 00:10:59,750 the universe has expanded even more. 238 00:10:59,750 --> 00:11:01,710 I won't even draw the whole bubble. 239 00:11:01,710 --> 00:11:04,680 But the place where the photon was emitted from 240 00:11:04,680 --> 00:11:07,630 might be over here. 241 00:11:07,630 --> 00:11:11,850 And now our current position is over here. 242 00:11:11,850 --> 00:11:18,250 Where the light got after 10 million years is now over here. 243 00:11:18,250 --> 00:11:24,070 And now, where the light is after 40 million years, 244 00:11:24,070 --> 00:11:27,500 maybe it's over here. 245 00:11:27,500 --> 00:11:29,520 So now this distance, the distance 246 00:11:29,520 --> 00:11:32,240 between these two points, when we started, 247 00:11:32,240 --> 00:11:33,590 it was 10 million light years. 248 00:11:33,590 --> 00:11:36,380 Then it became 20 million light years. 249 00:11:36,380 --> 00:11:39,100 Maybe now, it's on the order of-- I don't know-- maybe it's 250 00:11:39,100 --> 00:11:41,140 a billion light years. 251 00:11:41,140 --> 00:11:43,240 Maybe now it's a billion light years. 252 00:11:43,240 --> 00:11:45,512 And maybe this distance over here-- and I'm 253 00:11:45,512 --> 00:11:46,720 just making up these numbers. 254 00:11:46,720 --> 00:11:49,450 In fact, that's probably be too big for that point-- maybe this 255 00:11:49,450 --> 00:11:52,010 is now 100 million light years. 256 00:11:52,010 --> 00:11:55,390 This is now 100 million light years. 257 00:11:55,390 --> 00:11:59,050 And now, maybe this distance right 258 00:11:59,050 --> 00:12:01,730 here is-- I don't know-- 500 million light years. 259 00:12:01,730 --> 00:12:04,080 And maybe now the total distance between the two points 260 00:12:04,080 --> 00:12:05,950 is a billion light years. 261 00:12:05,950 --> 00:12:08,730 So as you can see, the photon might getting frustrated. 262 00:12:08,730 --> 00:12:10,230 As it covers more and more distance, 263 00:12:10,230 --> 00:12:13,200 it looks back and says, wow, in only 50 million years, 264 00:12:13,200 --> 00:12:16,020 I've been able to cover 600 million light years. 265 00:12:16,020 --> 00:12:16,910 That's pretty good. 266 00:12:16,910 --> 00:12:18,701 But it's frustrated because what it thought 267 00:12:18,701 --> 00:12:22,510 was it only had to cover 30 million light years 268 00:12:22,510 --> 00:12:23,050 in distance. 269 00:12:23,050 --> 00:12:25,070 That keeps stretching out because space 270 00:12:25,070 --> 00:12:26,560 itself is stretching. 271 00:12:26,560 --> 00:12:32,190 So the reality, just going to the original idea, 272 00:12:32,190 --> 00:12:36,050 this photon that is just reaching us, 273 00:12:36,050 --> 00:12:38,870 that's been traveling for-- let's say 274 00:12:38,870 --> 00:12:41,690 it's been traveling for 13.4 billion years. 275 00:12:41,690 --> 00:12:43,180 So it's reaching us is just now. 276 00:12:43,180 --> 00:12:46,690 So let me just fast forward 13.4 billion years 277 00:12:46,690 --> 00:12:49,620 from this point now to get to the present day. 278 00:12:49,620 --> 00:12:54,842 So if I draw the whole visible universe right over here, 279 00:12:54,842 --> 00:12:56,300 this point right over here is going 280 00:12:56,300 --> 00:13:00,340 to be-- where it was emitted from is right over there. 281 00:13:00,340 --> 00:13:04,890 We are sitting right over there. 282 00:13:04,890 --> 00:13:06,640 And actually, let me make something clear. 283 00:13:06,640 --> 00:13:08,770 If I'm drawing the whole observable universe, 284 00:13:08,770 --> 00:13:10,922 the center actually should be where we are. 285 00:13:10,922 --> 00:13:12,630 Because we can observe an equal distance. 286 00:13:12,630 --> 00:13:14,640 If things aren't really strange, we 287 00:13:14,640 --> 00:13:16,620 can observe an equal distance in any direction. 288 00:13:16,620 --> 00:13:19,210 So actually maybe we should put us at the center. 289 00:13:19,210 --> 00:13:21,650 So if this was the entire observable universe, 290 00:13:21,650 --> 00:13:26,180 and the photon was emitted from here 13.4 billion years ago-- 291 00:13:26,180 --> 00:13:29,800 so 300,000 years after that initial Big Bang, 292 00:13:29,800 --> 00:13:35,620 and it's just getting to us, it is true 293 00:13:35,620 --> 00:13:41,150 that the photon has been traveling 294 00:13:41,150 --> 00:13:47,050 for 13.7 billion years. 295 00:13:47,050 --> 00:13:50,900 But what's kind of nutty about it is this object, since we've 296 00:13:50,900 --> 00:13:53,970 been expanding away from each other, this object is now, 297 00:13:53,970 --> 00:13:56,180 in our best estimates, this object 298 00:13:56,180 --> 00:14:06,420 is going to be about 46 billion light years away from us. 299 00:14:06,420 --> 00:14:08,785 300 00:14:08,785 --> 00:14:10,160 And I want to make it very clear. 301 00:14:10,160 --> 00:14:13,220 This object is now 46 billion light years away from us. 302 00:14:13,220 --> 00:14:16,781 When we just use light to observe it, it looks like, 303 00:14:16,781 --> 00:14:18,530 just based on light years, hey, this light 304 00:14:18,530 --> 00:14:21,280 has been traveling 13.7 billion years to reach us. 305 00:14:21,280 --> 00:14:22,981 That's our only way of kind with light 306 00:14:22,981 --> 00:14:24,480 to kind of think about the distance. 307 00:14:24,480 --> 00:14:27,740 So maybe it's 13.4 or whatever-- I 308 00:14:27,740 --> 00:14:31,340 keep changing the decimal-- but 13.4 billion light years away. 309 00:14:31,340 --> 00:14:36,600 But the reality is if you had a ruler today, light year rulers, 310 00:14:36,600 --> 00:14:38,570 this space here has stretched so much 311 00:14:38,570 --> 00:14:41,702 that this is now 46 billion light years. 312 00:14:41,702 --> 00:14:43,160 And just to give you a hint of when 313 00:14:43,160 --> 00:14:45,100 we talk about the cosmic microwave background 314 00:14:45,100 --> 00:14:47,959 radiation, what will this point in space 315 00:14:47,959 --> 00:14:49,500 look like, this thing that's actually 316 00:14:49,500 --> 00:14:52,010 46 billion light years away, but the photon only 317 00:14:52,010 --> 00:14:54,540 took 13.7 billion years to reach us? 318 00:14:54,540 --> 00:14:56,120 What will this look like? 319 00:14:56,120 --> 00:14:59,610 Well, when we say look like, it's 320 00:14:59,610 --> 00:15:02,340 based on the photons that are reaching us right now. 321 00:15:02,340 --> 00:15:05,350 Those photons left 13.4 billion years ago. 322 00:15:05,350 --> 00:15:07,090 So those photons are the photons being 323 00:15:07,090 --> 00:15:10,040 emitted from this primitive structure, 324 00:15:10,040 --> 00:15:16,460 from this white-hot haze of hydrogen plasma. 325 00:15:16,460 --> 00:15:19,240 So what we're going to see is this white-hot haze. 326 00:15:19,240 --> 00:15:26,930 So we're going to see this kind of white-hot plasma, white hot, 327 00:15:26,930 --> 00:15:28,790 undifferentiated not differentiated 328 00:15:28,790 --> 00:15:32,550 into proper stable atoms, much less stars and galaxies, 329 00:15:32,550 --> 00:15:33,710 but white hot. 330 00:15:33,710 --> 00:15:36,220 We're going to see this white-hot plasma. 331 00:15:36,220 --> 00:15:38,640 The reality today is that point in space 332 00:15:38,640 --> 00:15:40,190 that's 46 billion years from now, 333 00:15:40,190 --> 00:15:45,160 it's probably differentiated into stable atoms, and stars, 334 00:15:45,160 --> 00:15:46,780 and planets, and galaxies. 335 00:15:46,780 --> 00:15:49,020 And frankly, if that person, that person, 336 00:15:49,020 --> 00:15:51,210 if there is a civilization there right now 337 00:15:51,210 --> 00:15:52,700 and if they're sitting right there, and they're observing 338 00:15:52,700 --> 00:15:54,610 photons being emitted from our coordinate, 339 00:15:54,610 --> 00:15:56,530 from our point in space right now, 340 00:15:56,530 --> 00:15:57,920 they're not going to see us. 341 00:15:57,920 --> 00:16:01,810 They're going to see us 13.4 billion years ago. 342 00:16:01,810 --> 00:16:05,140 They're going to see the super primitive state 343 00:16:05,140 --> 00:16:07,310 of our region of space when it really 344 00:16:07,310 --> 00:16:09,164 was just a white-hot plasma. 345 00:16:09,164 --> 00:16:11,580 And we're going to talk more about this in the next video. 346 00:16:11,580 --> 00:16:12,700 But think about it. 347 00:16:12,700 --> 00:16:15,510 Any photon that's coming from that period in time, 348 00:16:15,510 --> 00:16:17,670 so from any direction, that's been traveling 349 00:16:17,670 --> 00:16:21,170 for 13.4 billion years from any direction, 350 00:16:21,170 --> 00:16:23,720 it's going to come from that primitive state 351 00:16:23,720 --> 00:16:27,390 or it would have been emitted when the universe was 352 00:16:27,390 --> 00:16:29,580 in that primitive state, when it was just 353 00:16:29,580 --> 00:16:32,195 that white-hot plasma, this undifferentiated mass. 354 00:16:32,195 --> 00:16:33,570 And hopefully, that will give you 355 00:16:33,570 --> 00:16:36,480 a sense of where the cosmic microwave background 356 00:16:36,480 --> 00:16:38,920 radiation comes from.