1 00:00:00,000 --> 00:00:05,642 Right now, the best estimate of when the Big Bang occurred - 2 00:00:05,642 --> 00:00:08,661 and once again, I don't like the term that much, 'cause it kind of implies 3 00:00:08,661 --> 00:00:12,562 some type of explosion, but what it really is is kind of an expansion of space 4 00:00:12,562 --> 00:00:16,067 - when space really started to expand from a singularity 5 00:00:16,067 --> 00:00:18,924 but our best estimate of when this occurred is 6 00:00:18,924 --> 00:00:25,267 13.7 billion years ago, and even though we're used to 7 00:00:25,267 --> 00:00:28,584 dealing with numbers in the billions, especially when we talk about 8 00:00:28,584 --> 00:00:31,867 large amounts of money and whatnot, this is an unbelievable amount 9 00:00:31,867 --> 00:00:34,575 of time. It seems like something that is tractable, but 10 00:00:34,575 --> 00:00:37,841 it really isn't. And in future videos, I'm actually going 11 00:00:37,841 --> 00:00:39,933 to talk about the time scales, so you can really appreciate 12 00:00:39,933 --> 00:00:42,934 how long, or even start to appreciate, or appreciate 13 00:00:42,934 --> 00:00:47,267 that we CAN'T appreciate how long 13.7 billion years is. 14 00:00:47,267 --> 00:00:50,600 And I also want to emphasize that this is 15 00:00:50,600 --> 00:00:53,522 the current best estimate. Even in my life time, even in 16 00:00:53,522 --> 00:00:56,402 my life time that I actually new about the big bang and 17 00:00:56,402 --> 00:00:58,600 that I would pay attention to what the best estimate was, 18 00:00:58,600 --> 00:01:00,442 this number's been moving around, so I suspect 19 00:01:00,442 --> 00:01:03,181 that in the future, this number might become more accurate 20 00:01:03,181 --> 00:01:05,271 or might move arround some. 21 00:01:05,271 --> 00:01:07,779 But this is our best guess. Now, with that said, I want 22 00:01:07,779 --> 00:01:10,267 to think about what this tells us about the size 23 00:01:10,267 --> 00:01:13,373 of the observable universe. 24 00:01:15,635 --> 00:01:23,548 So, if all of the expansion started 13.7 billion years ago... 25 00:01:23,548 --> 00:01:28,333 [and] all of everything we know in our 3 dimensional universe 26 00:01:28,333 --> 00:01:29,933 was in a single point, 27 00:01:29,933 --> 00:01:33,925 the longest that any photon of light could be traveling 28 00:01:33,925 --> 00:01:35,271 that's reaching us right now... 29 00:01:35,271 --> 00:01:37,593 (so, our eye is right...) 30 00:01:37,593 --> 00:01:39,915 (so, let's say that's my eye right over there) 31 00:01:39,915 --> 00:01:42,516 (that's my eyelashes, just like that) 32 00:01:42,516 --> 00:01:44,281 the longest - so, some photon of light, 33 00:01:44,281 --> 00:01:47,950 is just getting to my eye, or maybe 34 00:01:47,950 --> 00:01:50,400 it's just getting to the lense of a telescope - 35 00:01:50,400 --> 00:01:53,718 the longest that that could have been traveling 36 00:01:53,718 --> 00:01:55,902 is 13.7 billion years. 37 00:02:06,502 --> 00:02:09,498 So when we looked at that depiction 38 00:02:09,498 --> 00:02:11,267 (this, I think, was 2 or 3 videos ago) 39 00:02:11,267 --> 00:02:12,841 of the observable universe, 40 00:02:12,841 --> 00:02:15,117 I drew - it was a circle. 41 00:02:15,117 --> 00:02:17,764 It was this circle. 42 00:02:17,764 --> 00:02:21,108 And, when we see light coming from these 43 00:02:21,108 --> 00:02:23,771 remote objects, that light is getting to us right here 44 00:02:23,771 --> 00:02:26,200 this is where we are. This is where, I guess, 45 00:02:26,200 --> 00:02:28,863 in the depiction, the remote object was, 46 00:02:28,863 --> 00:02:32,532 but the light from that remote object is just now getting to us. 47 00:02:32,532 --> 00:02:38,656 And that light took 13.7 billion years to get to us. 48 00:02:42,656 --> 00:02:45,489 Now, what I'm going to hesitate to do, 49 00:02:45,489 --> 00:02:47,533 because we're talking over such large distances 50 00:02:47,533 --> 00:02:51,533 and such large time scales ...over which 51 00:02:51,533 --> 00:02:55,380 space itself is expanding, we're going to see 52 00:02:55,380 --> 00:03:00,691 that you cannot say that this object over here - 53 00:03:00,691 --> 00:03:02,744 this is not necessarily... 54 00:03:02,759 --> 00:03:03,906 this is NOT 55 00:03:03,967 --> 00:03:04,744 (I'll put it in caps.) 56 00:03:04,744 --> 00:03:13,538 This is NOT 13.7 billion light years away! 57 00:03:13,538 --> 00:03:16,125 If we're talking about smaller time scales, 58 00:03:16,125 --> 00:03:18,043 or, I guess, smaller distances, 59 00:03:18,043 --> 00:03:19,892 you could say aproximately that. 60 00:03:19,892 --> 00:03:21,868 The expansion of the universe itself 61 00:03:21,868 --> 00:03:24,285 would not make as much of a difference. 62 00:03:24,285 --> 00:03:26,854 And let me make it even more clear. 63 00:03:26,854 --> 00:03:28,709 I'm talking about an object over there, 64 00:03:28,709 --> 00:03:31,867 but we can even talk about that coordinate in space. 65 00:03:31,867 --> 00:03:34,127 And that coordinate in (and actually I should say, 66 00:03:34,127 --> 00:03:35,722 "That coordinate in space-time." 67 00:03:35,722 --> 00:03:37,533 'Cause we're viewing it at a certain instant as well.) 68 00:03:37,533 --> 00:03:43,121 But that coordinate is not 13.7 billion light-years 69 00:03:43,121 --> 00:03:44,700 away from our current coordinate. 70 00:03:44,700 --> 00:03:46,464 And there are a couple of reasons to think about it. 71 00:03:46,464 --> 00:03:47,533 First of all, think about it. 72 00:03:47,533 --> 00:03:51,533 That light was emmitted 13.7 billion years ago. 73 00:03:51,533 --> 00:03:55,845 When that light was emmitted, we were much closer to that coordinate. 74 00:03:55,845 --> 00:03:57,842 This coordinate was much closer to that. 75 00:03:57,842 --> 00:03:59,189 Where we are in the universe now 76 00:03:59,189 --> 00:04:01,371 was much closer to that point in the universe. 77 00:04:01,371 --> 00:04:05,933 The other thing to think about is, as this - let me actually draw it. 78 00:04:05,933 --> 00:04:12,017 So let's say that - let's go three hundred thousand years 79 00:04:12,017 --> 00:04:16,867 after that initial expansion of that singularity. 80 00:04:16,867 --> 00:04:19,867 So, we're just 300,000 years into 81 00:04:19,867 --> 00:04:22,177 the universe's history, right now. 82 00:04:22,177 --> 00:04:28,214 So this is roughly 300,000 years into 83 00:04:28,214 --> 00:04:32,267 the universe's... life, I guess we could view it that way. 84 00:04:32,267 --> 00:04:34,315 And let's say at that point - well, first of all 85 00:04:34,315 --> 00:04:37,455 at that point, things haven't differentiated 86 00:04:37,455 --> 00:04:39,034 in meaningful ways yet, right now. 87 00:04:39,034 --> 00:04:41,249 We'll talk more about this when we talk about 88 00:04:41,249 --> 00:04:43,678 the cosmic microwave background radiation, 89 00:04:43,678 --> 00:04:45,015 but at this point in the universe 90 00:04:45,015 --> 00:04:48,067 it was kind of this almost uniform 91 00:04:48,067 --> 00:04:51,109 whitehot plasma of hydrogen. 92 00:04:51,109 --> 00:04:52,966 And we're going to talk about - it was emmiting 93 00:04:52,966 --> 00:04:54,777 microwave radiation, and we'll talk more about that 94 00:04:54,777 --> 00:04:56,082 in a future video. 95 00:04:56,082 --> 00:05:00,397 But let's just think about two points in this early universe. 96 00:05:00,397 --> 00:05:03,467 So, in this early universe, let's say you have that point, 97 00:05:03,467 --> 00:05:04,808 and let's say you have 98 00:05:04,808 --> 00:05:08,495 the coordinate where we are right now. 99 00:05:10,202 --> 00:05:12,767 I won't make it the center. 100 00:05:12,767 --> 00:05:14,746 'Cause I think it makes it easier to visualize 101 00:05:14,746 --> 00:05:15,938 if it's not the center. 102 00:05:15,938 --> 00:05:18,462 And let's say that very early stage in the universe 103 00:05:18,462 --> 00:05:21,310 if you were able to just take some rullers 104 00:05:21,310 --> 00:05:22,800 instantaneously and measure that, 105 00:05:22,800 --> 00:05:26,180 you would measure this distance 106 00:05:26,703 --> 00:05:29,449 to be 30 million light-years. 107 00:05:35,187 --> 00:05:37,800 And let's just say right at that point, 108 00:05:37,800 --> 00:05:40,799 this [magenta] object over here 109 00:05:40,799 --> 00:05:43,000 emits a photon. Maybe in the microwave 110 00:05:43,000 --> 00:05:45,880 frequency range, and we'll see 111 00:05:45,880 --> 00:05:48,462 that that was the range it was emmitting in. 112 00:05:48,462 --> 00:05:50,134 But, it emits a photon. 113 00:05:50,134 --> 00:05:51,996 And that photon is traveling at the speed of light! 114 00:05:51,996 --> 00:05:53,062 It IS light! 115 00:05:53,062 --> 00:05:54,536 And so, that photon says, "Oh, you know..." 116 00:05:54,536 --> 00:05:56,902 "I only got 30 million light-years to travel." 117 00:05:56,902 --> 00:05:58,354 "That's not too bad. I'm gonna get there" 118 00:05:58,354 --> 00:06:00,252 "in thirty-million years." 119 00:06:00,252 --> 00:06:02,585 And so - and I'm going to do it descrete. 120 00:06:02,585 --> 00:06:04,656 The math is really more complicated than what I'm doing here, 121 00:06:04,656 --> 00:06:06,435 But I really just want to give you the idea 122 00:06:06,435 --> 00:06:08,010 of what's going on, here. 123 00:06:08,010 --> 00:06:10,056 So, let's just say, that photon says, 124 00:06:10,056 --> 00:06:13,069 you know, "In about ten million years, I should be" 125 00:06:14,623 --> 00:06:17,274 "right about at that coordinate." 126 00:06:17,905 --> 00:06:20,645 "I should be about one third of the distance." 127 00:06:20,645 --> 00:06:25,800 But what happens over the course of those ten million years? 128 00:06:25,800 --> 00:06:27,938 Well, over those 10 million years, 129 00:06:27,938 --> 00:06:30,118 the universe has expanded some. 130 00:06:30,118 --> 00:06:32,538 The universe has expanded, maybe, a good deal. 131 00:06:32,538 --> 00:06:35,498 So let me draw the expanded universe 132 00:06:35,498 --> 00:06:37,967 So after ten million years, the universe... 133 00:06:37,967 --> 00:06:40,654 ...might look like this. 134 00:06:41,054 --> 00:06:43,071 (Actually, it might even be bigger than that.) 135 00:06:43,071 --> 00:06:45,000 (Let me draw it like this.) 136 00:06:45,015 --> 00:06:47,132 After ten million years, 137 00:06:47,132 --> 00:06:49,470 the universe might have expanded a good bit. 138 00:06:49,470 --> 00:06:53,419 So, this is ten million years into the future. 139 00:06:53,696 --> 00:06:56,839 Still, on a cosmological time scale, 140 00:06:56,839 --> 00:07:00,104 still almost at the infancy of the universe, 141 00:07:00,104 --> 00:07:02,550 'cause we're talking about 13.7 billion years. 142 00:07:02,550 --> 00:07:06,875 So let's say 10 million years go by. 143 00:07:07,644 --> 00:07:09,363 The universe has expanded. 144 00:07:09,363 --> 00:07:12,062 This coordinate where we're sitting at present 145 00:07:12,062 --> 00:07:15,460 is now all the way over here. 146 00:07:15,460 --> 00:07:18,774 That coordinate where the photon was 147 00:07:18,774 --> 00:07:21,425 originally emitted is now 148 00:07:21,425 --> 00:07:23,839 going to be sitting right over here. 149 00:07:23,839 --> 00:07:25,604 And that photon has said, "Ok," 150 00:07:25,604 --> 00:07:27,479 "After ten million light-years [sic] I'm going to get" 151 00:07:27,479 --> 00:07:28,887 "over there," 152 00:07:28,887 --> 00:07:30,454 And, you know, I'm aproximating and I'm doing it 153 00:07:30,454 --> 00:07:32,604 in a very descrete way - I really just want to give you the idea. 154 00:07:32,604 --> 00:07:35,600 So that coordinate, roughly where the photon 155 00:07:35,600 --> 00:07:37,210 gets in ten million light years 156 00:07:37,210 --> 00:07:38,915 Is about right over here. 157 00:07:38,915 --> 00:07:39,877 The whole universe has expanded. 158 00:07:39,877 --> 00:07:42,704 All the coordinates have gotten further apart. 159 00:07:42,704 --> 00:07:44,129 Now what just happened here? 160 00:07:44,129 --> 00:07:45,462 The universe has expanded. 161 00:07:45,462 --> 00:07:47,720 This distance that was 30 million light-years 162 00:07:47,720 --> 00:07:51,853 now - and I'm just making rough numbers - 163 00:07:51,853 --> 00:07:56,467 now it is actually - this is really just for the sake of 164 00:07:56,467 --> 00:08:01,946 giving you the idea of why... giving you the intuition 165 00:08:01,946 --> 00:08:03,773 of what's going on - 166 00:08:03,773 --> 00:08:06,333 This distance now is no longer 30 million light-years 167 00:08:06,333 --> 00:08:09,215 Maybe it's a hundred million. 168 00:08:10,399 --> 00:08:15,476 So this is now a hundred million light-years. 169 00:08:15,476 --> 00:08:17,878 The universe is expanding. 170 00:08:17,878 --> 00:08:21,080 The space is actually spreading out. 171 00:08:21,080 --> 00:08:22,952 You can imagine it's kind of a trampoline, 172 00:08:22,952 --> 00:08:25,197 or the surface of a baloon - getting stretched thin. 173 00:08:25,197 --> 00:08:28,169 And so this coordinate where the light happens to be 174 00:08:28,169 --> 00:08:29,237 after ten million years, 175 00:08:29,237 --> 00:08:31,420 it has been traveling for ten million years, 176 00:08:31,420 --> 00:08:33,867 but it's gone a much larger distance! 177 00:08:33,867 --> 00:08:39,000 It has now gone - that distance might be 178 00:08:39,000 --> 00:08:42,707 on the order of maybe 30 million light years. 179 00:08:42,707 --> 00:08:44,098 And the math isn't exact, here. 180 00:08:44,098 --> 00:08:46,652 I haven't done the math to figure it out. 181 00:08:46,652 --> 00:08:49,903 But the point here - so, it's done 30 million light-years. 182 00:08:49,903 --> 00:08:52,503 And actually, I shouldn't even make it 183 00:08:52,503 --> 00:08:55,243 the same proportion, because the distance it's gone 184 00:08:55,243 --> 00:08:56,636 and the distance it has to go, 185 00:08:56,636 --> 00:08:58,333 because of the stretching, it's not going to be 186 00:08:58,333 --> 00:09:01,652 completely linear. At least, when I'm thinking about it 187 00:09:01,652 --> 00:09:02,999 in my head, it shouldn't be, I think. 188 00:09:02,999 --> 00:09:05,000 But I'm not going to make a hard statement 189 00:09:05,000 --> 00:09:05,800 about that. 190 00:09:05,800 --> 00:09:08,067 But the distance that it traversed - maybe 191 00:09:08,067 --> 00:09:13,308 this distance right here is now 20 million light-years 192 00:09:13,308 --> 00:09:18,000 ...because every time it moved some distance, 193 00:09:18,000 --> 00:09:21,800 the space that it had traversed is now stretched. 194 00:09:21,800 --> 00:09:27,194 So even though it's travelled for 10 million years, 195 00:09:27,194 --> 00:09:30,000 the space that it traversed is no longer just 196 00:09:30,000 --> 00:09:31,652 10 million light-years. 197 00:09:31,652 --> 00:09:33,933 It's now stretched to 20 million light years. 198 00:09:33,933 --> 00:09:36,067 And the space that it has left to traverse 199 00:09:36,067 --> 00:09:38,339 is no longer only 20 million light-years. 200 00:09:38,339 --> 00:09:40,986 It might now be 80 million light-years. 201 00:09:43,940 --> 00:09:46,931 And so, this photon might be getting frustrated. 202 00:09:46,931 --> 00:09:49,021 There's an optimistic way of viewing it, is like, 203 00:09:49,021 --> 00:09:52,179 "Wow! I was able to cover 20 million light-years" 204 00:09:52,179 --> 00:09:53,898 "in only ten million years." 205 00:09:53,898 --> 00:09:56,003 "It looks like I'm moving faster than the speed of light." 206 00:09:56,003 --> 00:09:58,867 The reality is, it's not, because the space coordinates themselves 207 00:09:58,867 --> 00:10:00,677 are spreading out. 208 00:10:00,677 --> 00:10:03,231 Those are getting thin. So, the photon is just moving 209 00:10:03,231 --> 00:10:05,925 at the speed of light. But the distance that it actually 210 00:10:05,925 --> 00:10:08,267 traversed in ten million years is more than 211 00:10:08,267 --> 00:10:10,847 ten million light-years. 212 00:10:10,847 --> 00:10:12,519 It's 20 million light-years. 213 00:10:12,519 --> 00:10:15,677 So, you can't just multiply rate by time 214 00:10:15,677 --> 00:10:17,163 on these cosmological scales, here. 215 00:10:17,163 --> 00:10:19,671 Especially when the coordinates themselves 216 00:10:19,671 --> 00:10:23,525 are actually moving away from each other. 217 00:10:23,525 --> 00:10:28,333 But I think you might see where this is going. 218 00:10:28,333 --> 00:10:30,863 Now this photon says, "Oh," 219 00:10:30,863 --> 00:10:35,321 "In another 40 million light years [sic]," 220 00:10:35,321 --> 00:10:40,012 "maybe I'm going to get over here." 221 00:10:40,012 --> 00:10:42,984 But the reality is over that next 40 million years, 222 00:10:42,984 --> 00:10:48,092 it might get right over here, 223 00:10:48,092 --> 00:10:50,507 'cause this is 80 million light years. 224 00:10:50,507 --> 00:10:54,269 The reality is, after 40 million years, 225 00:10:54,269 --> 00:10:55,989 so, another 40 million years go by... 226 00:10:55,989 --> 00:10:58,049 Now, all of a sudden, the universe has expanded 227 00:10:58,049 --> 00:11:00,000 even more! 228 00:11:00,000 --> 00:11:01,840 I won't even draw the whole bubble, 229 00:11:01,840 --> 00:11:04,285 but the place where the photon was emitted from 230 00:11:04,285 --> 00:11:06,575 might be over here, 231 00:11:06,575 --> 00:11:12,292 and now our current position is over here, 232 00:11:12,292 --> 00:11:16,678 where the light got after ten million years 233 00:11:16,678 --> 00:11:18,456 is now over here, 234 00:11:18,456 --> 00:11:23,431 and now where the light is after 40 million years, 235 00:11:23,431 --> 00:11:26,131 is maybe over here. 236 00:11:26,131 --> 00:11:31,456 So, now this distance between these two points: 237 00:11:31,456 --> 00:11:33,852 when we started, it was 10 million light years, 238 00:11:33,852 --> 00:11:36,003 then it became 20 million light-years 239 00:11:36,003 --> 00:11:38,944 maybe now it's on the order of - I dont' know 240 00:11:38,944 --> 00:11:41,777 maybe it's a billion light years! 241 00:11:41,777 --> 00:11:45,395 And maybe this distance over here, 242 00:11:45,395 --> 00:11:47,348 and I'm just making up these numbers, 243 00:11:47,348 --> 00:11:49,716 in fact, that's probably too big for that point... 244 00:11:49,716 --> 00:11:52,869 Maybe this is now a hundred million light-years. 245 00:11:54,269 --> 00:11:59,322 And now, this distance maybe is, I dunno 246 00:12:00,122 --> 00:12:01,858 500 million light-years. 247 00:12:01,858 --> 00:12:05,925 And maybe now the total distance between the two points is a billion light years. 248 00:12:05,925 --> 00:12:08,729 So, as you can see, the photon might be getting frustrated. 249 00:12:08,729 --> 00:12:10,896 As it covers more and more distance, it looks back, 250 00:12:10,896 --> 00:12:15,933 and says, "Wow, in only 50 million years, I've been able to cover 600 million light-years," 251 00:12:15,933 --> 00:12:17,071 "That's pretty good." 252 00:12:17,071 --> 00:12:18,604 But it's frustrated, because what it thought 253 00:12:18,604 --> 00:12:22,922 it had to cover - 30 million light-years - 254 00:12:22,922 --> 00:12:24,890 that keeps stretching out. 255 00:12:24,890 --> 00:12:26,591 'cause space itself is stretching. 256 00:12:26,591 --> 00:12:30,167 So the reality, just going to the original idea, 257 00:12:30,167 --> 00:12:36,251 this photon that is just reaching us 258 00:12:36,251 --> 00:12:41,916 that has been traveling for, let's say, 13.4 billion years 259 00:12:41,916 --> 00:12:46,839 so, it's reaching us just now, so let me just fast-forward 13.4 billion years 260 00:12:46,839 --> 00:12:49,858 from this point now to get to the present day. 261 00:12:49,858 --> 00:12:55,467 So if I draw the whole visible universe right over here 262 00:12:55,467 --> 00:13:00,267 this point right over here is going to be where it was emitted from. 263 00:13:00,267 --> 00:13:05,618 We are sitting right... over there. And actually... 264 00:13:05,618 --> 00:13:08,600 Let me make something clear. If I'm drawing the whole observable universe, 265 00:13:08,600 --> 00:13:11,731 the center actually should be where we are, 'cause we can observe an equal distance 266 00:13:11,731 --> 00:13:16,733 - if things aren't really strange - we can observe an equal distance in any direction. 267 00:13:16,733 --> 00:13:19,766 So, actually, maybe we should put us at the center. 268 00:13:19,766 --> 00:13:23,748 So, this is the entire observable universe. And the photon was emitted from here 269 00:13:23,748 --> 00:13:29,703 13.4 billion years ago. So 300,000 years [sic] after that initial big bang. 270 00:13:29,703 --> 00:13:31,579 And it's just getting to us. 271 00:13:33,795 --> 00:13:45,067 It is true that the photon has been traveling for 13.7 billion years [sic]. 272 00:13:46,267 --> 00:13:52,538 But, what's kind of nutty about it is, this object, since we've been expanding away from eachother 273 00:13:52,538 --> 00:13:55,647 this object is now, in our best estimates 274 00:13:56,755 --> 00:14:03,031 46 billion light-years away from us. 275 00:14:07,877 --> 00:14:10,093 And I want to make it very clear: 276 00:14:10,093 --> 00:14:13,217 This object is NOW 46 billion light-years away. 277 00:14:13,217 --> 00:14:16,133 So when we just use light to observe it, it looks like 278 00:14:16,133 --> 00:14:20,880 just based on light years, hey, this light's been traveling 13.7 billion years to reach us, 279 00:14:20,880 --> 00:14:26,595 that's our only way, kind of, with light, to think about the distance, so maybe it's 13.4 280 00:14:26,595 --> 00:14:29,286 chuckle (I keep changing the decimal) 281 00:14:29,286 --> 00:14:32,013 but, [maybe it's] 13.4 billion light-years away. 282 00:14:32,013 --> 00:14:34,231 But the reality is, if you had a ruler today 283 00:14:34,231 --> 00:14:35,934 and, you know, light-year rulers 284 00:14:35,934 --> 00:14:39,025 this thing, the space has stretched so much 285 00:14:39,025 --> 00:14:41,446 that this is now 46 billion light-years. 286 00:14:41,446 --> 00:14:43,824 And just to give you a hint of when we talk about 287 00:14:43,824 --> 00:14:45,600 the cosmic microwave background radiation, 288 00:14:45,600 --> 00:14:48,477 what will this point in space look like? 289 00:14:48,477 --> 00:14:50,990 This thing that's actually 46 billion light-years away 290 00:14:50,990 --> 00:14:54,225 but the photon only took 13.7 [sic] billion years to reach us. 291 00:14:54,225 --> 00:14:55,710 What will this look like? 292 00:14:55,710 --> 00:14:59,867 Well, when we say, "look like," it's based on 293 00:14:59,867 --> 00:15:02,304 the photons that are reaching us right now. 294 00:15:02,304 --> 00:15:05,067 Those photons left 13.4 billion years ago. 295 00:15:05,067 --> 00:15:08,016 So, those photons are the photons being emitted 296 00:15:08,016 --> 00:15:11,128 from this primitive structure, from this white-hot 297 00:15:11,128 --> 00:15:14,913 haze of hydrogen plasma. 298 00:15:15,452 --> 00:15:18,651 So what we're going to see is this white-hot haze 299 00:15:18,651 --> 00:15:23,836 - so we're going to see this kind of 300 00:15:24,036 --> 00:15:26,125 white hot plasma. 301 00:15:27,402 --> 00:15:32,384 Undifferentiated, not differentiated into proper stable atoms, much less stars and galaxies. 302 00:15:32,384 --> 00:15:36,269 But white-hot - we're going to see this white hot plasma. 303 00:15:36,269 --> 00:15:40,133 The reality today is that that point in space that's 46 billion years from now [sic] 304 00:15:40,133 --> 00:15:46,800 it's probably differentiated into stable atoms and stars and planets and galaxies. 305 00:15:46,800 --> 00:15:52,134 And frankly, if that person - if there is a civilization there right now, and they're sitting right there 306 00:15:52,134 --> 00:15:53,933 and they're observing photons being emitted 307 00:15:53,933 --> 00:15:56,400 from our coordinate, from our point in space right now [sic] 308 00:15:56,400 --> 00:15:58,729 They're not going to see us. They're going to see 309 00:15:58,729 --> 00:16:02,305 us 13.4 billion years ago. They're going to see 310 00:16:02,305 --> 00:16:06,809 the super primitive state of our region of space 311 00:16:06,809 --> 00:16:09,642 when it really was just a white-hot plasma. 312 00:16:09,642 --> 00:16:12,475 And we're going to talk more about this in the next video, but think about it. 313 00:16:12,475 --> 00:16:15,447 ANY photon that's coming from that period in time, 314 00:16:15,447 --> 00:16:17,769 so, from any direction, that's been traveling for 315 00:16:17,769 --> 00:16:20,973 13.4 billion years, from any direction, 316 00:16:20,973 --> 00:16:23,800 is going to come from that primitive state, or, 317 00:16:23,800 --> 00:16:27,986 it would have been emitted when the universe was in 318 00:16:27,986 --> 00:16:30,401 that primitive state, when it was just that white-hot 319 00:16:30,401 --> 00:16:32,800 plasma, this undifferentiated mass. 320 00:16:32,800 --> 00:16:34,488 And hopefully, that'll give you a sense of where 321 00:16:34,488 --> 00:16:38,919 the cosmic microwave background radiation comes from.