1 00:00:08,160 --> 00:00:10,980 The phone content is provided under a Creative Commons 2 00:00:10,980 --> 00:00:12,100 license. 3 00:00:12,100 --> 00:00:14,400 Your support will help MIT OpenCourseWare 4 00:00:14,400 --> 00:00:18,790 continue to offer high quality educational resources for free. 5 00:00:18,790 --> 00:00:21,390 To make a donation or view additional materials 6 00:00:21,390 --> 00:00:25,350 from hundreds of MIT courses, visit MIT OpenCourseWare 7 00:00:25,350 --> 00:00:28,570 at ocw.mit.edu. 8 00:00:28,570 --> 00:00:30,630 NICHOLAS DIBELLA: So I hope I've impressed you 9 00:00:30,630 --> 00:00:32,820 all over the past couple of weeks about how 10 00:00:32,820 --> 00:00:35,580 interesting the universe is. 11 00:00:35,580 --> 00:00:38,750 If it's infinite, if the universe is an infinite thing, 12 00:00:38,750 --> 00:00:41,417 which all her observations seem to indicate that it is, 13 00:00:41,417 --> 00:00:43,500 we're all consistent with the idea of the universe 14 00:00:43,500 --> 00:00:47,520 being infinite, than anything that is possible happens. 15 00:00:47,520 --> 00:00:50,170 So we exist here. 16 00:00:50,170 --> 00:00:52,470 We humans exist on this planet we call Earth. 17 00:00:52,470 --> 00:00:54,820 So we're obviously possible. 18 00:00:54,820 --> 00:00:56,539 And so we obviously happen. 19 00:00:56,539 --> 00:00:58,080 But in an infinite universe, not only 20 00:00:58,080 --> 00:00:59,704 does everything that's possible happen, 21 00:00:59,704 --> 00:01:01,512 it happens infinitely many times. 22 00:01:01,512 --> 00:01:02,970 So, in particular, we should expect 23 00:01:02,970 --> 00:01:06,740 to find infinitely many copies of this planets, 24 00:01:06,740 --> 00:01:09,180 and infinitely many copies of this room, these chairs 25 00:01:09,180 --> 00:01:12,870 in the exact configuration here, with you, and so forth, and so 26 00:01:12,870 --> 00:01:14,500 on. 27 00:01:14,500 --> 00:01:18,000 So if the universe is infinite, obviously there 28 00:01:18,000 --> 00:01:22,620 should be infinitely many intelligent extraterrestrial 29 00:01:22,620 --> 00:01:24,340 civilizations. 30 00:01:24,340 --> 00:01:27,600 That's just a simple consequence of assuming 31 00:01:27,600 --> 00:01:31,290 that the universe is infinite. 32 00:01:31,290 --> 00:01:33,540 Now, I mentioned last time that it's 33 00:01:33,540 --> 00:01:37,830 important to distinguish between the whole universe, which 34 00:01:37,830 --> 00:01:40,680 is the whole universe, and the observed universe, which is 35 00:01:40,680 --> 00:01:44,430 only just a small part of it. 36 00:01:44,430 --> 00:01:47,010 The universe has a finite age. 37 00:01:47,010 --> 00:01:49,260 It's about 14 billion years old. 38 00:01:49,260 --> 00:01:54,825 And since then, light has only had a certain amount of time 39 00:01:54,825 --> 00:01:57,033 to reach us from all the galaxies and all the objects 40 00:01:57,033 --> 00:01:58,080 in the universe. 41 00:01:58,080 --> 00:02:01,810 And it hasn't had time to reach us from everything. 42 00:02:01,810 --> 00:02:04,463 We're gradually seeing more and more of the universe. 43 00:02:04,463 --> 00:02:07,384 But there's only a finite amount of stuff that we can see. 44 00:02:07,384 --> 00:02:09,300 And the finite amount of stuff that we can see 45 00:02:09,300 --> 00:02:11,820 forms the observed universe. 46 00:02:11,820 --> 00:02:14,160 And it's obviously not infinite. 47 00:02:14,160 --> 00:02:15,750 We can't possibly see the infinitude 48 00:02:15,750 --> 00:02:17,200 of the whole universe. 49 00:02:17,200 --> 00:02:21,420 But the observed universe is still pretty big. 50 00:02:21,420 --> 00:02:25,800 The observed universe has a diameter of about 80 billion 51 00:02:25,800 --> 00:02:27,390 light years across. 52 00:02:27,390 --> 00:02:31,350 And a light year is how far light travels in a year. 53 00:02:31,350 --> 00:02:38,100 So 80 billion light years comes out to about 500,000 billion, 54 00:02:38,100 --> 00:02:39,330 billion miles. 55 00:02:39,330 --> 00:02:42,500 So that's five, followed by 23 zeros. 56 00:02:42,500 --> 00:02:47,510 And that's how many miles across the observed universe. 57 00:02:47,510 --> 00:02:50,100 That's equivalent to making a trip across the equator 58 00:02:50,100 --> 00:02:55,860 of the Earth six, followed by 19 zeros, so 60 billion, 59 00:02:55,860 --> 00:02:57,540 billion times. 60 00:02:57,540 --> 00:03:01,320 So the observed universe is pretty big. 61 00:03:01,320 --> 00:03:04,660 Now, much of the universe is empty space. 62 00:03:04,660 --> 00:03:07,830 But not all of it is, obviously, because we 63 00:03:07,830 --> 00:03:09,750 see galaxies and so forth. 64 00:03:12,750 --> 00:03:15,330 So in fact, there are about 100 billion galaxies 65 00:03:15,330 --> 00:03:17,832 that we see in the observed universe. 66 00:03:42,460 --> 00:03:45,290 For those of you who don't know scientific notation, 67 00:03:45,290 --> 00:03:47,890 this 10 with the subscript 11, just means 1, 68 00:03:47,890 --> 00:03:49,330 followed by 11 zeroes. 69 00:03:52,540 --> 00:03:54,860 That's a lot of galaxies. 70 00:03:54,860 --> 00:03:59,650 And each one of these galaxies has about 100 billion stars 71 00:03:59,650 --> 00:04:00,940 inside of it. 72 00:04:00,940 --> 00:04:04,660 So 10 to the 11th stars in each galaxy. 73 00:04:12,690 --> 00:04:14,380 So if you ask, how many stars are there 74 00:04:14,380 --> 00:04:15,650 in the observed universe? 75 00:04:15,650 --> 00:04:18,180 You just take these two numbers, multiply them together. 76 00:04:18,180 --> 00:04:25,147 And you get 10 to the 22 stars in the observed universe. 77 00:04:31,480 --> 00:04:34,770 Now, you might wonder, how many planets are there 78 00:04:34,770 --> 00:04:35,949 in the observed universe? 79 00:04:35,949 --> 00:04:37,490 Well, we don't know how many of these 80 00:04:37,490 --> 00:04:41,330 stars actually have planetary systems like our own. 81 00:04:41,330 --> 00:04:47,400 But we've observed actually about on the order 82 00:04:47,400 --> 00:04:52,740 of 300 or so additional planets outside of our solar system, 83 00:04:52,740 --> 00:04:53,760 extra-solar planets. 84 00:04:53,760 --> 00:04:55,377 We call them exoplanets. 85 00:04:55,377 --> 00:04:57,210 And we've been able to come up with a number 86 00:04:57,210 --> 00:05:00,180 of the proportion of stars that actually have planets. 87 00:05:00,180 --> 00:05:06,000 And so we get a number of something like 30% of stars 88 00:05:06,000 --> 00:05:06,870 also have planets. 89 00:05:19,720 --> 00:05:21,550 Let's assume, for just simplicity, 90 00:05:21,550 --> 00:05:23,650 that each star has one planet. 91 00:05:23,650 --> 00:05:29,380 So that gives us 30% of this number, which is 3, times 10 92 00:05:29,380 --> 00:05:30,415 to the 21 planets. 93 00:05:34,580 --> 00:05:37,995 Now, how many of these planets could possibly support life? 94 00:05:37,995 --> 00:05:39,370 That's another important question 95 00:05:39,370 --> 00:05:42,190 that you might be wondering about. 96 00:05:42,190 --> 00:05:44,420 We also don't know the answer to this question. 97 00:05:44,420 --> 00:05:49,643 But a reasonable guess is that 1% of planets are habitable. 98 00:06:01,000 --> 00:06:05,365 So this gives 3, times 10 to the 19th habitable planets. 99 00:06:15,830 --> 00:06:19,150 Now, how many of these habitable planets actually 100 00:06:19,150 --> 00:06:21,230 go on to develop life? 101 00:06:21,230 --> 00:06:22,480 I mean, they can develop life. 102 00:06:22,480 --> 00:06:23,750 But do they? 103 00:06:23,750 --> 00:06:26,740 We also don't know that answer. 104 00:06:26,740 --> 00:06:30,910 But you can make a reasonable guess 105 00:06:30,910 --> 00:06:33,760 that maybe 10% of planets that can support life, 106 00:06:33,760 --> 00:06:37,490 do support life, so just 10% of this number. 107 00:06:37,490 --> 00:06:51,130 So that gives 3, times 10 to the 18th planets with life 108 00:06:51,130 --> 00:06:54,470 in the observed universe. 109 00:06:54,470 --> 00:06:56,574 If the universe is infinite, you would expect 110 00:06:56,574 --> 00:06:57,740 there to be infinitely many. 111 00:06:57,740 --> 00:06:59,239 But in the observed universe, that's 112 00:06:59,239 --> 00:07:01,914 certainly a lot of planets with life. 113 00:07:01,914 --> 00:07:03,455 Now, an even more important question, 114 00:07:03,455 --> 00:07:07,340 and a more interesting question, and a much harder question, 115 00:07:07,340 --> 00:07:10,430 is how many of these planets with life 116 00:07:10,430 --> 00:07:12,200 have intelligent life? 117 00:07:12,200 --> 00:07:14,000 I mean, not just life to begin with-- life 118 00:07:14,000 --> 00:07:14,916 can be very primitive. 119 00:07:14,916 --> 00:07:16,730 It can be in the form of bacteria, 120 00:07:16,730 --> 00:07:19,320 or single-celled things. 121 00:07:19,320 --> 00:07:23,900 But how many of these planets actually have intelligent life? 122 00:07:23,900 --> 00:07:25,750 We have no idea of that answer. 123 00:07:25,750 --> 00:07:31,047 But you can make a couple of guesses. 124 00:07:31,047 --> 00:07:32,630 I mean, just look at the sheer number. 125 00:07:32,630 --> 00:07:36,449 3 times 10 to the 18th, that's three billion, 126 00:07:36,449 --> 00:07:37,740 billion planets that have life. 127 00:07:41,000 --> 00:07:45,380 Let's suppose that 1% of them have intelligent life. 128 00:07:45,380 --> 00:07:55,080 If 1% have intelligent life, that 129 00:07:55,080 --> 00:08:01,380 gives rise to 3 times 10 to the 16th intelligent alien species 130 00:08:01,380 --> 00:08:03,003 in the observed universe. 131 00:08:14,120 --> 00:08:19,190 Of course, the number could be much, much smaller than this. 132 00:08:19,190 --> 00:08:27,790 So what if it's, say, 0.000000001%? 133 00:08:27,790 --> 00:08:30,815 That's 1, 2, 3, 4, 5, 6, 7-- 134 00:08:34,112 --> 00:08:37,989 let's make another 0, 1% have intelligence. 135 00:08:40,760 --> 00:08:46,470 So this is 10 to the minus 10. 136 00:08:54,009 --> 00:08:56,050 That's the proportion that have intelligent life. 137 00:08:56,050 --> 00:08:58,220 So you just take this number, and multiply by that. 138 00:09:00,980 --> 00:09:11,840 And you get 3 times 10 to the 8th intelligence alien species, 139 00:09:11,840 --> 00:09:17,291 or 300 million alien species that are intelligent. 140 00:09:20,380 --> 00:09:22,790 So this very simple. 141 00:09:22,790 --> 00:09:23,633 Yes, question? 142 00:09:23,633 --> 00:09:25,008 AUDIENCE: What would you consider 143 00:09:25,008 --> 00:09:27,377 intelligent [? life? ?] 144 00:09:27,377 --> 00:09:29,460 NICHOLAS DIBELLA: Yeah, so that's a good question. 145 00:09:29,460 --> 00:09:31,800 So what defines intelligent life? 146 00:09:31,800 --> 00:09:34,785 They should be able to solve problems. 147 00:09:37,510 --> 00:09:40,120 Basically, do the things that we can do. 148 00:09:40,120 --> 00:09:43,420 I mean, what kind of things can we do? 149 00:09:43,420 --> 00:09:45,156 We can build stuff. 150 00:09:45,156 --> 00:09:46,530 There are a bunch of chairs here. 151 00:09:46,530 --> 00:09:47,946 AUDIENCE: Beavers can build stuff. 152 00:09:47,946 --> 00:09:49,492 NICHOLAS DIBELLA: What's that? 153 00:09:49,492 --> 00:09:52,080 Yeah, OK, build complicated stuff. 154 00:09:55,170 --> 00:09:57,550 For the purpose of our discussion, 155 00:09:57,550 --> 00:10:00,940 let's just say a species is intelligent 156 00:10:00,940 --> 00:10:04,520 if it can, essentially, do all the stuff that we can do. 157 00:10:04,520 --> 00:10:07,269 I mean, it's a hard question, how you define intelligent. 158 00:10:07,269 --> 00:10:09,060 AUDIENCE: It's just like, where [INAUDIBLE] 159 00:10:09,060 --> 00:10:10,820 finding intelligence [INAUDIBLE] 160 00:10:10,820 --> 00:10:12,854 NICHOLAS DIBELLA: Right, right. 161 00:10:12,854 --> 00:10:14,270 AUDIENCE: There could be something 162 00:10:14,270 --> 00:10:17,415 that could be even more intelligent than us. 163 00:10:17,415 --> 00:10:18,790 And then we'd have to [INAUDIBLE] 164 00:10:18,790 --> 00:10:22,070 NICHOLAS DIBELLA: Yeah, yeah, so there could be something-- 165 00:10:22,070 --> 00:10:25,544 so by our standards, maybe a super intelligent civilization 166 00:10:25,544 --> 00:10:26,960 would not be judged as intelligent 167 00:10:26,960 --> 00:10:29,990 by us, just because we have no idea how to judge them. 168 00:10:29,990 --> 00:10:33,030 Yeah, that's certainly possible. 169 00:10:33,030 --> 00:10:34,890 That's a hard question. 170 00:10:34,890 --> 00:10:38,150 That would lead to an entire other discussion 171 00:10:38,150 --> 00:10:41,000 of this whole business. 172 00:10:43,760 --> 00:10:46,770 For now, we can define intelligent 173 00:10:46,770 --> 00:10:49,460 in kind of an operational way, in terms of what they do, 174 00:10:49,460 --> 00:10:51,240 rather than in terms of how they think. 175 00:10:51,240 --> 00:10:58,220 So if they can build vehicles that can travel long distances, 176 00:10:58,220 --> 00:11:00,210 if they can build computers that can compute, 177 00:11:00,210 --> 00:11:04,850 if they can build rocket ships, if they can figure out science, 178 00:11:04,850 --> 00:11:07,740 if they can do science, that's probably 179 00:11:07,740 --> 00:11:12,590 another important characteristic of things that are intelligent. 180 00:11:12,590 --> 00:11:13,820 Yeah? 181 00:11:13,820 --> 00:11:16,295 AUDIENCE: Can you give an accurate estimate 182 00:11:16,295 --> 00:11:23,395 on how many intelligent species of life on this galaxy? 183 00:11:23,395 --> 00:11:24,770 NICHOLAS DIBELLA: In this galaxy? 184 00:11:24,770 --> 00:11:25,730 Well, let's assume-- 185 00:11:25,730 --> 00:11:27,305 AUDIENCE: [INAUDIBLE]. 186 00:11:27,305 --> 00:11:28,930 NICHOLAS DIBELLA: In your star galaxy-- 187 00:11:28,930 --> 00:11:32,710 yes, so there are about 10 to the 11 galaxies 188 00:11:32,710 --> 00:11:34,230 in the observed universe. 189 00:11:34,230 --> 00:11:38,190 So we can approximate them all as being about the same. 190 00:11:38,190 --> 00:11:40,740 So 300 million in all-- 191 00:11:44,175 --> 00:11:46,550 with this really low probability of intelligence arising, 192 00:11:46,550 --> 00:11:48,280 300 million in all. 193 00:11:48,280 --> 00:11:52,250 And then you divide that by 10 of the 11th. 194 00:11:52,250 --> 00:11:55,830 So that gives you about 1 in 1,000. 195 00:11:55,830 --> 00:11:59,000 So 1 intelligent species for every 1,000 galaxies, 196 00:11:59,000 --> 00:12:01,490 that's with this low estimate of intelligent life arising. 197 00:12:01,490 --> 00:12:03,110 With this larger estimate, you get 3 198 00:12:03,110 --> 00:12:06,470 to the 16th, divided by 10 of the 11th. 199 00:12:06,470 --> 00:12:08,810 So that's 3, times 10 to the 5. 200 00:12:08,810 --> 00:12:10,295 So 300,000 intelligent-- 201 00:12:10,295 --> 00:12:11,450 AUDIENCE: [INAUDIBLE]. 202 00:12:14,600 --> 00:12:19,110 NICHOLAS DIBELLA: So, yeah, there's an important question. 203 00:12:19,110 --> 00:12:21,080 With some estimates, you get a high number 204 00:12:21,080 --> 00:12:23,030 of intelligent species. 205 00:12:23,030 --> 00:12:24,980 With other estimates of this number, 206 00:12:24,980 --> 00:12:29,180 you get a smaller number of intelligent species. 207 00:12:29,180 --> 00:12:34,250 But in both cases, there's still a lot of intelligent features 208 00:12:34,250 --> 00:12:37,400 that we would expect to see in the universe. 209 00:12:37,400 --> 00:12:39,890 And, yet, we don't seem to see any of them. 210 00:12:39,890 --> 00:12:41,840 So there's the big question. 211 00:12:41,840 --> 00:12:43,036 Where is everybody? 212 00:13:08,828 --> 00:13:11,320 Where is everybody? 213 00:13:11,320 --> 00:13:13,360 And this is called the Fermi Paradox. 214 00:13:22,530 --> 00:13:26,132 Who first explicitly asked the question, 215 00:13:26,132 --> 00:13:27,840 where is everybody, when he was referring 216 00:13:27,840 --> 00:13:31,559 to the expected number of alien civilizations 217 00:13:31,559 --> 00:13:33,600 that there should be, and that we should observe. 218 00:13:36,980 --> 00:13:40,950 Enrico Fermi was one of the great physicists 219 00:13:40,950 --> 00:13:44,350 of the 20th century. 220 00:13:44,350 --> 00:13:46,520 It was named after-- 221 00:13:46,520 --> 00:13:47,850 I don't think he started it. 222 00:13:47,850 --> 00:13:51,830 But it was named after him, Fermi Lab. 223 00:13:51,830 --> 00:13:56,280 He was an Italian physicist, originally from Italy. 224 00:13:56,280 --> 00:14:00,300 And he was one of the very few physicists that 225 00:14:00,300 --> 00:14:03,480 was both a brilliant theoretical physicist 226 00:14:03,480 --> 00:14:05,640 and a brilliant experimental physicist. 227 00:14:05,640 --> 00:14:07,210 Those are very hard to come by. 228 00:14:07,210 --> 00:14:11,160 And in today's world of physics, that's even rarer, because now 229 00:14:11,160 --> 00:14:12,970 the fields have diversified so much 230 00:14:12,970 --> 00:14:15,090 that it's really hard to be an expert in one field 231 00:14:15,090 --> 00:14:16,880 and an expert in the other field. 232 00:14:16,880 --> 00:14:18,120 But Fermi was both of them. 233 00:14:18,120 --> 00:14:20,670 So he was really like the uber physicist. 234 00:14:26,070 --> 00:14:27,310 So, yeah, where is everybody? 235 00:14:27,310 --> 00:14:31,520 Does anybody have an explanation? 236 00:14:31,520 --> 00:14:40,609 AUDIENCE: [INAUDIBLE] 237 00:14:40,609 --> 00:14:42,150 NICHOLAS DIBELLA: So your explanation 238 00:14:42,150 --> 00:14:43,890 is that they're there. 239 00:14:43,890 --> 00:14:45,960 But we just have a hard time seeing them. 240 00:14:45,960 --> 00:14:49,430 We just can't see them, essentially. 241 00:14:49,430 --> 00:14:50,070 Yes? 242 00:14:50,070 --> 00:14:51,320 AUDIENCE: Maybe they all died. 243 00:14:51,320 --> 00:14:52,903 NICHOLAS DIBELLA: Maybe they all died. 244 00:14:52,903 --> 00:14:55,090 That's possible. 245 00:14:55,090 --> 00:14:55,590 Yes? 246 00:14:55,590 --> 00:14:57,307 AUDIENCE: [INAUDIBLE]. 247 00:14:57,307 --> 00:14:59,140 NICHOLAS DIBELLA: Maybe they haven't reached 248 00:14:59,140 --> 00:15:00,160 our level of technology. 249 00:15:00,160 --> 00:15:03,040 Yeah, maybe we're the super race. 250 00:15:07,542 --> 00:15:09,375 Maybe they're too advanced for us to detect. 251 00:15:09,375 --> 00:15:10,950 Like, maybe they are omitting some kind of signals. 252 00:15:10,950 --> 00:15:12,630 But we just can't understand it. 253 00:15:12,630 --> 00:15:13,734 Yeah. 254 00:15:13,734 --> 00:15:17,430 AUDIENCE: This is kind of weird, but have you 255 00:15:17,430 --> 00:15:20,392 ever considered that they have found us 256 00:15:20,392 --> 00:15:21,600 but don't want to talk to us? 257 00:15:21,600 --> 00:15:23,070 NICHOLAS DIBELLA: The aliens have found us. 258 00:15:23,070 --> 00:15:24,300 But they don't want to talk to us. 259 00:15:24,300 --> 00:15:25,674 Like, maybe they're observing us. 260 00:15:25,674 --> 00:15:28,140 But they're not going to talk to us. 261 00:15:28,140 --> 00:15:42,016 AUDIENCE: [INAUDIBLE] 262 00:15:42,016 --> 00:15:44,140 NICHOLAS DIBELLA: Yeah, that's another possibility. 263 00:15:47,160 --> 00:15:48,740 I guess they kind of look down on us. 264 00:15:48,740 --> 00:15:51,080 They don't want to contact us. 265 00:15:51,080 --> 00:15:54,410 And they prevent us from being able to contact them. 266 00:15:54,410 --> 00:15:57,660 Yeah, that's another possibility. 267 00:15:57,660 --> 00:15:59,530 Any other explanations? 268 00:16:03,290 --> 00:16:06,800 So there are essentially three explanations 269 00:16:06,800 --> 00:16:10,580 that people tend to give for this paradox. 270 00:16:10,580 --> 00:16:12,690 A paradox is just a contradiction between-- 271 00:16:12,690 --> 00:16:14,334 an apparent contradiction. 272 00:16:14,334 --> 00:16:15,500 You expect to see one thing. 273 00:16:15,500 --> 00:16:17,217 But you actually see another thing. 274 00:16:17,217 --> 00:16:18,800 There should be some reason behind it. 275 00:16:18,800 --> 00:16:21,970 That's just where the paradox is. 276 00:16:21,970 --> 00:16:24,440 And there are essentially three explanations 277 00:16:24,440 --> 00:16:28,820 that people seem to give for the paradox. 278 00:16:28,820 --> 00:16:31,970 The first is that they are here. 279 00:16:31,970 --> 00:16:34,610 The aliens are here. 280 00:16:34,610 --> 00:16:37,670 There are a lot of people that believe 281 00:16:37,670 --> 00:16:41,060 that we have been visited by alien spacecraft, 282 00:16:41,060 --> 00:16:43,680 and they're meddling in our affairs. 283 00:16:43,680 --> 00:16:45,500 In fact, you can look at the polls. 284 00:16:45,500 --> 00:16:48,470 Something like 3/4 of Americans-- 285 00:16:51,220 --> 00:16:54,790 that was terrestrial in nature, not extraterrestrial. 286 00:16:54,790 --> 00:16:57,310 Something like 3/4 of Americans, or even more, 287 00:16:57,310 --> 00:16:59,600 believe that we have been visited by aliens. 288 00:16:59,600 --> 00:17:02,932 And they are currently meddling in our affairs, 289 00:17:02,932 --> 00:17:05,140 you know, freaking us out, doing all this crazy stuff 290 00:17:05,140 --> 00:17:06,400 that we can't explain. 291 00:17:06,400 --> 00:17:06,991 Yeah? 292 00:17:06,991 --> 00:17:09,343 AUDIENCE: [INAUDIBLE] 293 00:17:09,343 --> 00:17:10,843 NICHOLAS DIBELLA: What if they what? 294 00:17:10,843 --> 00:17:18,962 AUDIENCE: [INAUDIBLE] 295 00:17:18,962 --> 00:17:20,920 NICHOLAS DIBELLA: Maybe they live in the ocean. 296 00:17:20,920 --> 00:17:22,970 Yeah, maybe. 297 00:17:22,970 --> 00:17:23,757 Yes? 298 00:17:23,757 --> 00:17:26,274 AUDIENCE: [INAUDIBLE] 299 00:17:26,274 --> 00:17:28,690 NICHOLAS DIBELLA: What if we were sucked into a black hole 300 00:17:28,690 --> 00:17:30,314 and we can't hear them because of that? 301 00:17:30,314 --> 00:17:35,940 AUDIENCE: [INAUDIBLE] 302 00:17:35,940 --> 00:17:38,500 NICHOLAS DIBELLA: Yes, and this is 303 00:17:38,500 --> 00:17:39,960 another excellent explanation. 304 00:17:39,960 --> 00:17:42,310 So maybe they got sucked into a black hole. 305 00:17:42,310 --> 00:17:43,965 And they were trying to contact us. 306 00:17:43,965 --> 00:17:45,840 But the light couldn't escape the black hole. 307 00:17:45,840 --> 00:17:47,800 Nothing can escape a black hole. 308 00:17:47,800 --> 00:17:50,290 Yeah, that's another conceivable equation. 309 00:17:50,290 --> 00:17:55,030 I guess that would go under the disaster scenario, something 310 00:17:55,030 --> 00:17:57,827 for one reason or another, they get effectively destroyed. 311 00:17:57,827 --> 00:18:00,160 I mean, not really destroyed, but effectively destroyed. 312 00:18:00,160 --> 00:18:01,606 Yeah? 313 00:18:01,606 --> 00:18:05,462 AUDIENCE: If you put a bomb in a black hole, 314 00:18:05,462 --> 00:18:10,054 would the bomb explode [INAUDIBLE] 315 00:18:10,054 --> 00:18:12,470 NICHOLAS DIBELLA: The bomb would explode in a sort of way, 316 00:18:12,470 --> 00:18:14,290 in the black hole. 317 00:18:14,290 --> 00:18:17,080 So anything inside a black hole is being constantly attracted 318 00:18:17,080 --> 00:18:18,740 to the center. 319 00:18:18,740 --> 00:18:20,440 And so you can imagine-- 320 00:18:20,440 --> 00:18:23,740 you can kind of imagine throwing a bomb off a plane, 321 00:18:23,740 --> 00:18:25,790 and looking at the explosion like that. 322 00:18:25,790 --> 00:18:28,390 It's falling down. 323 00:18:28,390 --> 00:18:30,360 Although I don't-- 324 00:18:30,360 --> 00:18:32,110 AUDIENCE: But you would never see 325 00:18:32,110 --> 00:18:33,080 it explode if you were outside the black hole. 326 00:18:33,080 --> 00:18:34,380 NICHOLAS DIBELLA: Yeah, if you're outside the block hole, 327 00:18:34,380 --> 00:18:35,296 you wouldn't see that. 328 00:18:35,296 --> 00:18:36,516 But, anyway-- 329 00:18:36,516 --> 00:18:38,800 AUDIENCE: [INAUDIBLE]. 330 00:18:38,800 --> 00:18:41,346 NICHOLAS DIBELLA: Yeah, then they 331 00:18:41,346 --> 00:18:43,220 could see it if you're inside the black hole. 332 00:18:43,220 --> 00:18:45,710 But what we're talking about with aliens today. 333 00:18:45,710 --> 00:18:52,790 Black holes will have to wait, probably next week, next week. 334 00:18:52,790 --> 00:19:00,460 So the first time exploration that people give is they exist. 335 00:19:00,460 --> 00:19:01,390 And they are here. 336 00:19:10,490 --> 00:19:16,210 Now, we've all heard stories of people talking 337 00:19:16,210 --> 00:19:19,540 about reported sightings of UFOs that they 338 00:19:19,540 --> 00:19:21,550 think are flying saucers. 339 00:19:21,550 --> 00:19:26,200 And maybe we even hear stories where people are abducted by-- 340 00:19:26,200 --> 00:19:28,540 I was about to black holes-- 341 00:19:28,540 --> 00:19:31,640 people were abducted by aliens. 342 00:19:31,640 --> 00:19:34,240 We've all heard these stories. 343 00:19:34,240 --> 00:19:35,920 I won't really spend a whole lot of time 344 00:19:35,920 --> 00:19:40,630 on this first explanation, because, fortunately 345 00:19:40,630 --> 00:19:44,110 or unfortunately, most of these stories, most 346 00:19:44,110 --> 00:19:48,580 of these pieces of evidence that people claim are 347 00:19:48,580 --> 00:19:52,660 due to are extraterrestrials can be easily explained away. 348 00:19:52,660 --> 00:19:55,600 They can be reproducible. 349 00:19:55,600 --> 00:20:01,556 For example, maybe you see some kind of a weird light 350 00:20:01,556 --> 00:20:03,430 in the sky, some kind of a weird shape moving 351 00:20:03,430 --> 00:20:06,100 in a weird sort of way. 352 00:20:06,100 --> 00:20:09,110 And they said, well, hey, maybe that's an extraterrestrial. 353 00:20:09,110 --> 00:20:13,360 It's just visiting us doing something. 354 00:20:13,360 --> 00:20:14,650 That's certainly possible. 355 00:20:14,650 --> 00:20:18,820 But we should try to first make simple explanations 356 00:20:18,820 --> 00:20:21,472 in trying to explain the things that we observe. 357 00:20:21,472 --> 00:20:22,930 Explanations of things that we know 358 00:20:22,930 --> 00:20:29,440 exist, things that we can reliably use to explain. 359 00:20:29,440 --> 00:20:32,230 It could certainly be that on that day 360 00:20:32,230 --> 00:20:37,420 there were unusual atmospheric conditions, for example, 361 00:20:37,420 --> 00:20:39,850 and you had light from the headlight of a car being 362 00:20:39,850 --> 00:20:41,827 refracted in a weird sort of way to produce 363 00:20:41,827 --> 00:20:43,410 some kind of a weird light in the sky. 364 00:20:43,410 --> 00:20:46,840 That's certainly possible. 365 00:20:46,840 --> 00:20:49,600 It could also be that the person was observing 366 00:20:49,600 --> 00:20:52,362 some kind of plane, or some kind of a weather balloon, 367 00:20:52,362 --> 00:20:53,320 or something like that. 368 00:20:57,826 --> 00:20:59,200 A lot of these sightings are very 369 00:20:59,200 --> 00:21:03,174 easy to explain on the basis of terrestrial intelligence, 370 00:21:03,174 --> 00:21:05,340 as opposed to extraterrestrial intelligence, or even 371 00:21:05,340 --> 00:21:06,580 terrestrial non-intelligence. 372 00:21:06,580 --> 00:21:07,913 They could be naturally created. 373 00:21:10,660 --> 00:21:14,094 Photos and videos, those are easy to duplicate. 374 00:21:14,094 --> 00:21:15,760 And definitely with today's' technology, 375 00:21:15,760 --> 00:21:20,080 with Photoshop and all that, it's very easy to fool even 376 00:21:20,080 --> 00:21:23,080 an expert on-- 377 00:21:23,080 --> 00:21:24,944 you present an expert with a video, and say, 378 00:21:24,944 --> 00:21:26,610 I want you to test the validity of this. 379 00:21:26,610 --> 00:21:27,550 See if this is valid. 380 00:21:27,550 --> 00:21:30,050 See if this is a valid UFO sighting. 381 00:21:30,050 --> 00:21:32,390 Well, UFO just stands for unidentified flying object. 382 00:21:32,390 --> 00:21:33,931 So anything you see in the sky that's 383 00:21:33,931 --> 00:21:36,730 flying that's an object that you just can't identify, 384 00:21:36,730 --> 00:21:38,940 you just don't know what it is, that's a UFO. 385 00:21:38,940 --> 00:21:42,355 Whether it's a flying saucer, is another piece of business. 386 00:21:42,355 --> 00:21:43,780 AUDIENCE: [INAUDIBLE]. 387 00:21:46,630 --> 00:21:49,132 NICHOLAS DIBELLA: What do you call an unidentified person? 388 00:21:49,132 --> 00:21:53,100 AUDIENCE: [INAUDIBLE]. 389 00:21:53,100 --> 00:21:55,590 NICHOLAS DIBELLA: An unidentified un-flying object. 390 00:21:55,590 --> 00:21:57,240 I don't know. 391 00:21:57,240 --> 00:21:59,700 You can call it whenever you want. 392 00:21:59,700 --> 00:22:01,410 I mean, before I met you, you were 393 00:22:01,410 --> 00:22:03,510 an unidentified non-flying object. 394 00:22:03,510 --> 00:22:08,340 So, anyway, so it's very easy to duplicate 395 00:22:08,340 --> 00:22:11,070 a lot of these findings, a lot of these sightings 396 00:22:11,070 --> 00:22:13,610 that people have. 397 00:22:13,610 --> 00:22:16,110 I guess not so much for the alien abductions 398 00:22:16,110 --> 00:22:18,989 that people claim to have, but we have mental institutions 399 00:22:18,989 --> 00:22:19,530 for a reason. 400 00:22:22,080 --> 00:22:24,900 No offense, no offense, if I hurt anybody's feelings 401 00:22:24,900 --> 00:22:27,400 in here. 402 00:22:27,400 --> 00:22:29,400 So it's really easy to duplicate these findings. 403 00:22:32,280 --> 00:22:34,080 Almost all of UFO sightings that people 404 00:22:34,080 --> 00:22:36,300 claim to have seen throughout the year 405 00:22:36,300 --> 00:22:38,822 can be duplicated or understood in some sort of way. 406 00:22:38,822 --> 00:22:40,280 But at the end of the year, there's 407 00:22:40,280 --> 00:22:45,510 still some small portion of cases that go unexplained. 408 00:22:45,510 --> 00:22:46,900 But why should-- 409 00:22:46,900 --> 00:22:50,310 OK, maybe you want an explanation for everything. 410 00:22:50,310 --> 00:22:54,960 But I personally think that's a little bit unreasonable. 411 00:22:54,960 --> 00:22:57,450 There are many things in the world that we 412 00:22:57,450 --> 00:22:58,700 don't have an explanation for. 413 00:23:01,340 --> 00:23:04,110 But we're pretty sure that if we spent the time and effort 414 00:23:04,110 --> 00:23:06,906 working on it that we would have an explanation for it. 415 00:23:06,906 --> 00:23:08,640 For example, if you look at the back 416 00:23:08,640 --> 00:23:13,217 of the classroom, the shades, something happened to them. 417 00:23:13,217 --> 00:23:14,550 Who knows what happened to them? 418 00:23:17,190 --> 00:23:21,105 I could try to get funding to research why that's the case. 419 00:23:24,000 --> 00:23:27,590 Maybe that could be a research project that I engage in. 420 00:23:27,590 --> 00:23:29,330 But do you think that would be worth it? 421 00:23:29,330 --> 00:23:31,496 Do you think maybe I should try to really understand 422 00:23:31,496 --> 00:23:33,865 what happened there, or work on something else, 423 00:23:33,865 --> 00:23:35,865 like trying to understand the nature of reality? 424 00:23:39,180 --> 00:23:41,330 Maybe you're odd, or statistically abnormal, 425 00:23:41,330 --> 00:23:43,655 to think that I should try to figure that out. 426 00:23:43,655 --> 00:23:45,780 There are a lot of things in the world that we just 427 00:23:45,780 --> 00:23:46,946 don't have explanations for. 428 00:23:46,946 --> 00:23:51,870 I mean, police they don't solve every single murder mystery 429 00:23:51,870 --> 00:23:53,700 they come across every year. 430 00:23:53,700 --> 00:23:56,450 There are some things that they just can't explain. 431 00:23:56,450 --> 00:23:57,670 They don't know who did it. 432 00:23:57,670 --> 00:23:59,295 They don't know who pulled the trigger. 433 00:24:02,287 --> 00:24:03,870 Some people demand for an explanation. 434 00:24:03,870 --> 00:24:06,324 But a lot of times we just don't get explanations. 435 00:24:06,324 --> 00:24:07,740 I mean, we don't think that it was 436 00:24:07,740 --> 00:24:10,170 some kind of an extraterrestrial intelligence that 437 00:24:10,170 --> 00:24:15,271 was responsible for the death of the parrots, or whatever. 438 00:24:15,271 --> 00:24:16,770 A lot of things just go unexplained. 439 00:24:16,770 --> 00:24:18,630 The world is just so big and so complex 440 00:24:18,630 --> 00:24:22,290 that life is too short to try to figure out what happened. 441 00:24:22,290 --> 00:24:24,520 Why did this happen? 442 00:24:24,520 --> 00:24:27,240 We're able to explain almost all of the things 443 00:24:27,240 --> 00:24:30,720 we observe, at least with the UFOs. 444 00:24:30,720 --> 00:24:33,214 And so it's reasonable to think that if we 445 00:24:33,214 --> 00:24:35,130 spent the time, and the effort, and the money, 446 00:24:35,130 --> 00:24:37,200 that we could figure things out. 447 00:24:37,200 --> 00:24:39,740 I think that's a reasonable position to take. 448 00:24:39,740 --> 00:24:46,830 But you should think about yourself. 449 00:24:46,830 --> 00:24:50,640 If you want, you should check out check out 450 00:24:50,640 --> 00:24:52,650 the files of UFO sightings. 451 00:24:52,650 --> 00:24:57,420 And see for yourself if it really 452 00:24:57,420 --> 00:25:00,330 tells a consistent story, if the data 453 00:25:00,330 --> 00:25:04,540 indicates it must be an extraterrestrial origin. 454 00:25:04,540 --> 00:25:07,800 So form your own opinions is what I'm trying to say. 455 00:25:10,850 --> 00:25:14,150 Any questions about what I think about? 456 00:25:14,150 --> 00:25:16,620 I have to admit, that's my own bias 457 00:25:16,620 --> 00:25:21,100 that I have kind of formed in regard to terrestrial sightings 458 00:25:21,100 --> 00:25:23,950 of extraterrestrial things. 459 00:25:23,950 --> 00:25:25,700 But you're free to have other opinions. 460 00:25:25,700 --> 00:25:28,650 Maybe you have very emotional experiences, 461 00:25:28,650 --> 00:25:30,683 and very vivid experiences. 462 00:25:33,490 --> 00:25:36,910 OK, so I won't be spending much more time 463 00:25:36,910 --> 00:25:40,320 on this first type of explanation, 464 00:25:40,320 --> 00:25:42,970 they exist and they are here. 465 00:25:42,970 --> 00:25:45,804 But I think there's a lot more to be learned. 466 00:25:45,804 --> 00:25:47,470 And there's a much more interesting type 467 00:25:47,470 --> 00:25:50,050 of explanation, which is that they exist. 468 00:25:55,150 --> 00:25:56,320 But they're not here. 469 00:25:56,320 --> 00:25:59,050 They exist, not here. 470 00:26:04,200 --> 00:26:10,751 Or let's say, they exist, but they haven't communicated. 471 00:26:19,409 --> 00:26:24,940 I should add in parentheses, yet, seemingly. 472 00:26:39,700 --> 00:26:43,360 So there are really two different observations 473 00:26:43,360 --> 00:26:44,760 in the Fermi paradox. 474 00:26:44,760 --> 00:26:46,755 One is that they don't seem to be here. 475 00:26:49,670 --> 00:26:52,690 I don't think anyone in this audience is an alien. 476 00:26:52,690 --> 00:26:54,540 You don't look like an alien. 477 00:26:54,540 --> 00:26:56,510 They don't seem to be here. 478 00:26:56,510 --> 00:27:01,470 But they also don't seem to be there in the stars, in the sky. 479 00:27:01,470 --> 00:27:03,720 So we need some kind of an explanation. 480 00:27:03,720 --> 00:27:08,130 So, first, let's try to understand why if they exist, 481 00:27:08,130 --> 00:27:11,140 why they're not here. 482 00:27:11,140 --> 00:27:13,016 So it's possible-- it's conceivable 483 00:27:13,016 --> 00:27:14,640 that an explanation is that it's simply 484 00:27:14,640 --> 00:27:19,080 impossible to travel the great distances to get here. 485 00:27:19,080 --> 00:27:23,190 Maybe it's physically impossible to get from one star system 486 00:27:23,190 --> 00:27:25,740 to a very far away other star system. 487 00:27:25,740 --> 00:27:28,220 Maybe that's the case. 488 00:27:28,220 --> 00:27:31,050 But it's probably not the case. 489 00:27:31,050 --> 00:27:31,900 Sorry? 490 00:27:31,900 --> 00:27:35,065 AUDIENCE: [INAUDIBLE]. 491 00:27:35,065 --> 00:27:37,440 NICHOLAS DIBELLA: Maybe they can exist in our atmosphere. 492 00:27:37,440 --> 00:27:38,510 Maybe that's another possibility. 493 00:27:38,510 --> 00:27:40,340 I would think that if they're advanced enough 494 00:27:40,340 --> 00:27:42,923 to figure out how to get there, they could probably figure out 495 00:27:42,923 --> 00:27:45,270 how to get inside our atmosphere, or least tell us, 496 00:27:45,270 --> 00:27:47,420 hey we're here. 497 00:27:47,420 --> 00:27:48,922 Come outside the planet. 498 00:27:48,922 --> 00:27:49,755 Let's play in space. 499 00:27:54,260 --> 00:27:56,390 There's nothing in the laws of physics that 500 00:27:56,390 --> 00:27:59,210 forbid interstellar travel. 501 00:27:59,210 --> 00:28:02,230 I mean, in principle we could do it today, with the rocket ships 502 00:28:02,230 --> 00:28:04,340 that we have now. 503 00:28:04,340 --> 00:28:06,925 But it would take a long time. 504 00:28:06,925 --> 00:28:09,050 To get to the nearest star, it would take something 505 00:28:09,050 --> 00:28:11,990 like 100,000 years. 506 00:28:11,990 --> 00:28:14,690 But there's nothing, in principle, that 507 00:28:14,690 --> 00:28:16,469 forbids interstellar travel. 508 00:28:16,469 --> 00:28:18,135 The laws of physics definitely allow it. 509 00:28:18,135 --> 00:28:21,710 It's more of an engineering problem 510 00:28:21,710 --> 00:28:26,340 to get to a far away star system in a short amount of time. 511 00:28:26,340 --> 00:28:28,610 So maybe the reason they're not here 512 00:28:28,610 --> 00:28:30,800 is not that it's impossible to get here, 513 00:28:30,800 --> 00:28:34,660 but just that they haven't had time to get here. 514 00:28:34,660 --> 00:28:37,590 That seems like a reasonable explanation. 515 00:28:37,590 --> 00:28:39,590 Certainly, if they have technology like our own, 516 00:28:39,590 --> 00:28:42,700 100,000 years it would take to get here, 517 00:28:42,700 --> 00:28:45,270 that's a long amount of time. 518 00:28:45,270 --> 00:28:48,530 At least it seems like it, when we think about it at first. 519 00:28:51,647 --> 00:28:52,730 But let's figure this out. 520 00:28:52,730 --> 00:28:54,146 Let's think about it more closely. 521 00:28:57,420 --> 00:29:00,200 So the galaxy is about-- 522 00:29:10,980 --> 00:29:15,460 OK, so let me backtrack a little bit. 523 00:29:15,460 --> 00:29:19,750 So we as a species, homo sapiens, sapiens, 524 00:29:19,750 --> 00:29:24,700 we've been around for about a million years, give or take 525 00:29:24,700 --> 00:29:26,950 a million years. 526 00:29:26,950 --> 00:29:31,067 And that's just the blink of an eye on a cosmic timescale. 527 00:29:31,067 --> 00:29:32,650 Compared with the age of the universe, 528 00:29:32,650 --> 00:29:38,550 compared with 14 billion years, it's less than 1,000th of that 529 00:29:38,550 --> 00:29:39,050 time. 530 00:29:39,050 --> 00:29:41,962 It's a very small amount of time. 531 00:29:41,962 --> 00:29:43,670 Also compared with the age of the galaxy, 532 00:29:43,670 --> 00:29:46,187 the galaxy is about the age of the universe, 533 00:29:46,187 --> 00:29:47,020 maybe a little less. 534 00:29:47,020 --> 00:29:49,210 Maybe it's 10 billion years old or so. 535 00:29:49,210 --> 00:29:52,510 Compared with the age of the galaxy, 536 00:29:52,510 --> 00:29:57,010 the time span of our existence is also very small. 537 00:29:57,010 --> 00:30:00,610 Now, there doesn't seem to be anything special about the time 538 00:30:00,610 --> 00:30:03,530 that we came into existence. 539 00:30:03,530 --> 00:30:09,620 We certainly needed time to develop from the things present 540 00:30:09,620 --> 00:30:11,010 in the very early Earth. 541 00:30:11,010 --> 00:30:13,210 It takes a long time for evolution 542 00:30:13,210 --> 00:30:16,820 to happen, and to produce intelligent species 543 00:30:16,820 --> 00:30:18,030 like our own. 544 00:30:18,030 --> 00:30:20,800 For example we have very good evidence 545 00:30:20,800 --> 00:30:24,530 that indicates that the earth is about 4.5 billion years old. 546 00:30:24,530 --> 00:30:31,900 So it took about 4.5 billion years for humans 547 00:30:31,900 --> 00:30:33,610 to eventually form. 548 00:30:33,610 --> 00:30:36,130 But there doesn't seem to be anything special about the time 549 00:30:36,130 --> 00:30:37,212 when Earth formed. 550 00:30:37,212 --> 00:30:38,920 There doesn't seem to be anything special 551 00:30:38,920 --> 00:30:43,030 about 4.5 billion years ago. 552 00:30:43,030 --> 00:30:48,190 It seems perfectly plausible to speculate 553 00:30:48,190 --> 00:30:51,850 that before 4.5 billion years ago, other planets formed, 554 00:30:51,850 --> 00:30:57,460 other Earth-like planets formed, and other human-like species 555 00:30:57,460 --> 00:30:58,780 came into being. 556 00:30:58,780 --> 00:31:04,690 So let's assume that one extraterrestrial species 557 00:31:04,690 --> 00:31:12,010 of intelligent life formed a billion years before Earth 558 00:31:12,010 --> 00:31:14,440 came into being, let's say. 559 00:31:14,440 --> 00:31:19,390 Or let's say intelligent beings came into existence 560 00:31:19,390 --> 00:31:23,260 a billion years ago, so I guess 900 million years 561 00:31:23,260 --> 00:31:25,810 before humans came into being. 562 00:31:25,810 --> 00:31:30,760 So let's say there's one extraterrestrial, at least 563 00:31:30,760 --> 00:31:32,838 one extraterrestrial civilization-- 564 00:31:47,000 --> 00:32:00,650 intelligent, very important-- originates 1 billion years ago. 565 00:32:06,940 --> 00:32:21,940 And then-- civilization, civilization. 566 00:32:21,940 --> 00:32:25,400 Have I removed all the spoonerisms? 567 00:32:25,400 --> 00:32:28,790 OK, that's an example of a spoonerism. 568 00:32:28,790 --> 00:32:30,170 Yeah, I think so. 569 00:32:30,170 --> 00:32:33,220 It's one of those weird linguistic things. 570 00:32:33,220 --> 00:32:36,050 So let's assume that one intelligent extraterrestrial 571 00:32:36,050 --> 00:32:40,070 civilization originated one billion years ago. 572 00:32:40,070 --> 00:32:44,630 Now, it's conceivable that the civilization 573 00:32:44,630 --> 00:32:50,210 will want to expand once it has the ability to. 574 00:32:50,210 --> 00:32:54,480 They might want to colonize the galaxy, say. 575 00:32:54,480 --> 00:32:57,320 Now, I'm not going to claim to know anything 576 00:32:57,320 --> 00:32:58,410 about alien psychology. 577 00:32:58,410 --> 00:33:01,400 I have no idea how aliens think. 578 00:33:01,400 --> 00:33:05,749 I have hard enough time trying to figure out how humans think. 579 00:33:05,749 --> 00:33:07,790 Even our experts, we don't know how humans think. 580 00:33:07,790 --> 00:33:10,832 So we have no idea how aliens might think. 581 00:33:10,832 --> 00:33:13,040 But it's conceivable to think that maybe, eventually, 582 00:33:13,040 --> 00:33:15,530 they'd want to leave their own star system, 583 00:33:15,530 --> 00:33:20,164 maybe for reasons of curiosity, maybe because they have to. 584 00:33:20,164 --> 00:33:21,830 Maybe there's an overpopulation problem, 585 00:33:21,830 --> 00:33:23,700 and they just have to expand outwards, 586 00:33:23,700 --> 00:33:24,616 they have to disburse. 587 00:33:27,470 --> 00:33:30,240 Maybe their own star, their own sun, runs out of fuel. 588 00:33:30,240 --> 00:33:33,950 And they have to find another sun. 589 00:33:33,950 --> 00:33:35,216 Who knows? 590 00:33:35,216 --> 00:33:37,340 It's totally conceivable to think that, eventually, 591 00:33:37,340 --> 00:33:40,070 an extraterrestrial civilization will want to colonize 592 00:33:40,070 --> 00:33:41,977 the galaxy, at least one. 593 00:33:41,977 --> 00:33:43,352 It's totally conceivable to think 594 00:33:43,352 --> 00:33:45,410 at least one extraterrestrial civilization will 595 00:33:45,410 --> 00:33:46,250 want to colonize. 596 00:33:46,250 --> 00:33:47,250 AUDIENCE: [INAUDIBLE]. 597 00:33:52,750 --> 00:33:54,820 NICHOLAS DIBELLA: Well, that depends. 598 00:33:54,820 --> 00:33:58,270 So that depends on the numbers that you put inside. 599 00:34:03,500 --> 00:34:05,960 Nobody knows what these two probabilities are. 600 00:34:08,750 --> 00:34:12,139 But you can speculate that maybe this is a significant number 601 00:34:12,139 --> 00:34:15,040 of civilizations in the galaxy. 602 00:34:15,040 --> 00:34:16,639 This is just another hypothesis. 603 00:34:16,639 --> 00:34:18,539 This is just one type of explanation 604 00:34:18,539 --> 00:34:19,414 to the Fermi paradox. 605 00:34:22,150 --> 00:34:28,699 So let's assume that there's one extraterrestrial civilization 606 00:34:28,699 --> 00:34:31,205 that's intelligent that originated a billion years ago. 607 00:34:31,205 --> 00:34:33,080 And then once they had sufficient technology, 608 00:34:33,080 --> 00:34:36,380 they decided to start colonizing the galaxy. 609 00:34:36,380 --> 00:34:40,242 So let's suppose that the way they do this is they-- 610 00:34:40,242 --> 00:34:41,450 let's say this is the galaxy. 611 00:34:44,402 --> 00:34:45,500 It doesn't look like that. 612 00:34:45,500 --> 00:34:47,090 But let's assume that's the galaxy. 613 00:34:47,090 --> 00:34:52,699 Let's say they started here, their original star system. 614 00:34:52,699 --> 00:34:54,909 They're are a bunch of other stars. 615 00:34:59,570 --> 00:35:04,030 Take this number, multiply by approximately 10 billion. 616 00:35:04,030 --> 00:35:11,960 And so then we can imagine what happened 617 00:35:11,960 --> 00:35:14,300 is that you start sending colonies outwards. 618 00:35:17,480 --> 00:35:19,790 So you have one group, one fleet maybe, 619 00:35:19,790 --> 00:35:22,170 one fleet that goes to this star. 620 00:35:22,170 --> 00:35:24,757 And then maybe they go to there. 621 00:35:24,757 --> 00:35:27,090 And at the same time, you have another fleet going here, 622 00:35:27,090 --> 00:35:28,850 which goes to there, and goes to there. 623 00:35:28,850 --> 00:35:30,130 This goes to there. 624 00:35:30,130 --> 00:35:33,660 This takes care of that guy, so on, and so forth. 625 00:35:33,660 --> 00:35:35,870 So there's a wave of colonization 626 00:35:35,870 --> 00:35:38,245 that happens, some kind of a wave that 627 00:35:38,245 --> 00:35:39,620 eventually gets the whole galaxy, 628 00:35:39,620 --> 00:35:42,142 eventually covers everything. 629 00:35:42,142 --> 00:35:43,850 Now, you can calculate how long it should 630 00:35:43,850 --> 00:35:47,240 take to colonize the galaxy. 631 00:35:47,240 --> 00:35:51,630 You can just feed in some numbers, and get an answer. 632 00:35:51,630 --> 00:35:57,230 So I said with our current technology, the best we can-- 633 00:35:57,230 --> 00:36:00,170 the fastest that we can accelerate rocket ships 634 00:36:00,170 --> 00:36:04,320 is about a percent of a percent of the speed of light, 635 00:36:04,320 --> 00:36:07,662 which is not very fast. 636 00:36:07,662 --> 00:36:09,620 But it's totally conceivable that in the future 637 00:36:09,620 --> 00:36:13,340 we'll be able to accelerate rocket ships much 638 00:36:13,340 --> 00:36:18,140 faster than that, maybe 1% of the speed of light. 639 00:36:18,140 --> 00:36:21,477 That would be a significant improvement. 640 00:36:21,477 --> 00:36:23,060 With current technology, we definitely 641 00:36:23,060 --> 00:36:24,470 can't do anything like that. 642 00:36:24,470 --> 00:36:27,050 But with the known laws of physics that we have, 643 00:36:27,050 --> 00:36:30,860 we can definitely hypothesize certain types of methods 644 00:36:30,860 --> 00:36:34,909 that people would use to get things going that fast. 645 00:36:34,909 --> 00:36:36,950 One attractive possibility that people talk about 646 00:36:36,950 --> 00:36:41,910 is to use some kind of an anti-matter fuel. 647 00:36:41,910 --> 00:36:44,707 So there are two kinds of things. 648 00:36:44,707 --> 00:36:47,040 At least, there are two kinds of things in the universe. 649 00:36:47,040 --> 00:36:49,220 There is matter, and there's anti-matter. 650 00:36:49,220 --> 00:36:50,710 For example, you have an electron, 651 00:36:50,710 --> 00:36:52,330 you have an anti-electron. 652 00:36:52,330 --> 00:36:55,400 An anti-electron is exactly like an electron every way, 653 00:36:55,400 --> 00:36:58,637 except that it has the opposite electric charge. 654 00:36:58,637 --> 00:37:00,470 So an electron has negative electric charge. 655 00:37:00,470 --> 00:37:02,930 An anti-electron has positive electric charge. 656 00:37:02,930 --> 00:37:06,800 And for every kind of particle of matter that you talk about, 657 00:37:06,800 --> 00:37:09,380 there is an associated anti-particle. 658 00:37:09,380 --> 00:37:11,870 And what happens when you take a particle 659 00:37:11,870 --> 00:37:13,880 with its anti-particle, you put them together, 660 00:37:13,880 --> 00:37:15,421 what happens is that they annihilate. 661 00:37:15,421 --> 00:37:18,894 And they give out a lot of energy. 662 00:37:18,894 --> 00:37:20,560 And so you might want to use this energy 663 00:37:20,560 --> 00:37:23,690 as a thrust in your rocket. 664 00:37:23,690 --> 00:37:26,030 And it turns out that you can get pretty high speeds 665 00:37:26,030 --> 00:37:30,370 with an anti-matter rocket. 666 00:37:30,370 --> 00:37:31,186 Yes? 667 00:37:31,186 --> 00:37:32,584 AUDIENCE: [INAUDIBLE]. 668 00:37:35,380 --> 00:37:37,380 NICHOLAS DIBELLA: So would the rocket eventually 669 00:37:37,380 --> 00:37:38,300 consume itself? 670 00:37:38,300 --> 00:37:39,258 You have to be careful. 671 00:37:44,870 --> 00:37:47,120 If you have a rocket built out of matter, 672 00:37:47,120 --> 00:37:49,620 make sure that the anti-matter doesn't leak onto the rocket. 673 00:37:49,620 --> 00:37:51,770 Or if you built the rocket out of anti-matter, 674 00:37:51,770 --> 00:37:54,103 make sure that the matter doesn't leak on to the rocket. 675 00:37:54,103 --> 00:37:57,140 So you have to be careful the way that it uses fuel. 676 00:37:57,140 --> 00:37:58,625 AUDIENCE: [INAUDIBLE]. 677 00:38:01,652 --> 00:38:03,110 NICHOLAS DIBELLA: Eventually, we'll 678 00:38:03,110 --> 00:38:09,020 be so smart we'll work out the kinks. 679 00:38:09,020 --> 00:38:13,790 You might also want to use some kind of a fusion thrust. 680 00:38:13,790 --> 00:38:19,167 For example, between all the stars and all the galaxies, 681 00:38:19,167 --> 00:38:21,500 it's mostly empty space, but not completely empty space. 682 00:38:21,500 --> 00:38:23,270 There is some matter. 683 00:38:23,270 --> 00:38:29,700 In fact, there's about one hydrogen atom per cubic meter. 684 00:38:29,700 --> 00:38:32,570 And so there's a little bit of matter. 685 00:38:32,570 --> 00:38:35,590 And you can imagine scooping up the hydrogen 686 00:38:35,590 --> 00:38:38,480 as you travel through space. 687 00:38:38,480 --> 00:38:41,030 And if you have fusion technology, 688 00:38:41,030 --> 00:38:43,760 then you can take these hydrogen atoms 689 00:38:43,760 --> 00:38:46,220 that you pick up, fuse them together, cause fusion 690 00:38:46,220 --> 00:38:47,150 to occur. 691 00:38:47,150 --> 00:38:50,390 And it's going to give off a lot of energy. 692 00:38:50,390 --> 00:38:53,670 And you can use that energy to propel yourself. 693 00:38:53,670 --> 00:38:55,250 So there are a lot of different ways 694 00:38:55,250 --> 00:38:56,958 that people have thought of to get things 695 00:38:56,958 --> 00:38:59,736 going at a very high speed. 696 00:38:59,736 --> 00:39:02,360 We're not good enough engineers to figure out how to do it yet. 697 00:39:02,360 --> 00:39:03,440 I mean, we figured out how to do it. 698 00:39:03,440 --> 00:39:04,290 We know the science. 699 00:39:04,290 --> 00:39:06,019 But it's really an engineering problem. 700 00:39:06,019 --> 00:39:07,310 We don't know how to do it yet. 701 00:39:07,310 --> 00:39:10,400 But it's totally conceivable that in a million years 702 00:39:10,400 --> 00:39:12,650 we'll be able to do it, if we're still alive. 703 00:39:12,650 --> 00:39:14,150 That's something conceivable, right? 704 00:39:14,150 --> 00:39:16,994 A million years-- maybe not 100 years, maybe not 200 years, 705 00:39:16,994 --> 00:39:19,490 but a million years. 706 00:39:19,490 --> 00:39:22,460 So maybe these intelligent extraterrestrials 707 00:39:22,460 --> 00:39:25,380 got to our intelligence at a billion years ago, 708 00:39:25,380 --> 00:39:27,260 and then it took them another million years 709 00:39:27,260 --> 00:39:31,012 to get up to 1% of the speed of light. 710 00:39:31,012 --> 00:39:32,790 That was startling. 711 00:39:32,790 --> 00:39:33,990 AUDIENCE: [INAUDIBLE]. 712 00:39:33,990 --> 00:39:34,948 NICHOLAS DIBELLA: What? 713 00:39:34,948 --> 00:39:37,790 AUDIENCE: [INAUDIBLE]. 714 00:39:37,790 --> 00:39:40,220 NICHOLAS DIBELLA: The loud noise just startled me. 715 00:39:40,220 --> 00:39:43,380 I wasn't expecting it. 716 00:39:43,380 --> 00:39:46,370 So let's say that after-- 717 00:39:46,370 --> 00:39:47,870 so takes them a million years to get 718 00:39:47,870 --> 00:39:51,980 to this point of intelligence where 719 00:39:51,980 --> 00:39:55,560 they can travel at 0.01 times the speed of light, 1% 720 00:39:55,560 --> 00:39:57,350 the speed of light. 721 00:39:57,350 --> 00:39:59,040 So, eventually, they're able to travel 722 00:39:59,040 --> 00:40:02,030 at 1% of the speed of light. 723 00:40:02,030 --> 00:40:08,540 And so this wave front, this wave of colonization, 724 00:40:08,540 --> 00:40:12,040 eventually goes upwards at about 0.01 times the speed of light, 725 00:40:12,040 --> 00:40:13,850 about 1% the speed of light. 726 00:40:13,850 --> 00:40:21,220 So let's assume that the colonies, they travel-- 727 00:40:21,220 --> 00:40:23,335 not the colonies, the fleets. 728 00:40:23,335 --> 00:40:25,040 I'll call them fleets. 729 00:40:25,040 --> 00:40:36,497 The fleets travel at 1% of the speed of light. 730 00:40:40,900 --> 00:40:44,550 And if they only take short breaks 731 00:40:44,550 --> 00:40:47,870 before reaching one star system before moving into the next, 732 00:40:47,870 --> 00:40:49,620 let's say it's very short, then the amount 733 00:40:49,620 --> 00:40:52,410 of time it would take them to get across the entire galaxy 734 00:40:52,410 --> 00:40:56,550 is just this distance, divided by that speed. 735 00:40:56,550 --> 00:41:00,180 Whoops, I forgot to write down a distance. 736 00:41:00,180 --> 00:41:04,800 So the galaxy is about 100,000 light years across. 737 00:41:04,800 --> 00:41:07,680 That's important to know-- 738 00:41:07,680 --> 00:41:09,330 our galaxy, the Milky Way galaxy. 739 00:41:21,200 --> 00:41:24,920 So if you take this distance, divided by this speed, then 740 00:41:24,920 --> 00:41:26,787 how long would it take? 741 00:41:26,787 --> 00:41:27,620 What does that give? 742 00:41:27,620 --> 00:41:31,670 How long would it take to get across the whole galaxy? 743 00:41:31,670 --> 00:41:32,770 So 10 million years. 744 00:41:49,171 --> 00:41:53,130 And 10 million years certainly sounds 745 00:41:53,130 --> 00:41:55,010 like a long amount of time. 746 00:41:55,010 --> 00:41:58,090 But on a galactic time scale, in a cosmic time scale, 747 00:41:58,090 --> 00:42:00,090 it's really nothing. 748 00:42:00,090 --> 00:42:01,739 This is supposed to happen-- 749 00:42:01,739 --> 00:42:03,280 so they originated billion years ago. 750 00:42:03,280 --> 00:42:04,530 And then we said it took them 1 million years 751 00:42:04,530 --> 00:42:07,215 to get this technology, and then 10 more million years 752 00:42:07,215 --> 00:42:09,100 to colonize a galaxy. 753 00:42:09,100 --> 00:42:10,100 So all of this happened. 754 00:42:10,100 --> 00:42:11,474 They colonized the entire galaxy. 755 00:42:14,240 --> 00:42:15,240 How long would that be-- 756 00:42:15,240 --> 00:42:21,480 1 million 11 years, so 989 million years ago, 757 00:42:21,480 --> 00:42:26,220 the entire galaxy was colonized, if these assumptions are right. 758 00:42:29,380 --> 00:42:30,730 But where are they? 759 00:42:33,930 --> 00:42:35,520 Our galaxy, the Milky Way galaxy. 760 00:42:38,580 --> 00:42:41,250 But we don't seem to see them anywhere here. 761 00:42:41,250 --> 00:42:44,040 So let's look at our assumptions again. 762 00:42:47,000 --> 00:42:48,464 This seems plausible. 763 00:42:48,464 --> 00:42:49,880 It seems plausible to think that-- 764 00:42:49,880 --> 00:42:51,460 the galaxy is very big. 765 00:42:51,460 --> 00:42:55,770 And it seems like there would be a chance for intelligent life 766 00:42:55,770 --> 00:43:00,240 to arise a billion years ago, as opposed to a million years ago. 767 00:43:00,240 --> 00:43:02,880 This seems plausible. 768 00:43:02,880 --> 00:43:05,400 The fleets travel at 1% of the speed of light. 769 00:43:05,400 --> 00:43:08,035 Eventually, we'll probably be able to do that. 770 00:43:08,035 --> 00:43:10,500 The galaxy is 100,000 light years across. 771 00:43:10,500 --> 00:43:12,436 We've measured that. 772 00:43:12,436 --> 00:43:13,560 And I didn't write it down. 773 00:43:13,560 --> 00:43:20,570 But I assume that the colonizers, 774 00:43:20,570 --> 00:43:24,150 they don't spend a lot of time before quickly moving on. 775 00:43:24,150 --> 00:43:25,690 So they don't spend time to rest. 776 00:43:25,690 --> 00:43:27,800 They don't spend time to do anything else. 777 00:43:27,800 --> 00:43:30,960 So maybe that assumption is flawed. 778 00:43:30,960 --> 00:43:34,050 So let's say that between each voyage, 779 00:43:34,050 --> 00:43:38,040 they rest for the amount of time that the voyage takes. 780 00:43:38,040 --> 00:43:40,770 So that would effectively double the whole time 781 00:43:40,770 --> 00:43:42,330 to do the whole trip. 782 00:43:42,330 --> 00:43:46,020 So if they did that, if they rested the amount of time 783 00:43:46,020 --> 00:43:48,780 each voyage takes, that would lead to 20 million years 784 00:43:48,780 --> 00:43:50,430 to colonize the galaxy. 785 00:43:50,430 --> 00:43:58,439 And that was 969 million years ago. 786 00:43:58,439 --> 00:43:59,730 That was still a long time ago. 787 00:43:59,730 --> 00:44:01,000 Where are they? 788 00:44:01,000 --> 00:44:04,130 So maybe that assumption is still flawed. 789 00:44:04,130 --> 00:44:08,260 It seems like that's possibly the most flawed assumption, 790 00:44:08,260 --> 00:44:11,100 in addition to how they would travel. 791 00:44:11,100 --> 00:44:13,620 Maybe it takes them a really long time 792 00:44:13,620 --> 00:44:16,590 before they can really colonize, and really settle, 793 00:44:16,590 --> 00:44:21,690 on a planetary system. 794 00:44:21,690 --> 00:44:22,815 Maybe it takes a long time. 795 00:44:22,815 --> 00:44:24,315 It takes a really long time for them 796 00:44:24,315 --> 00:44:26,955 to settle, and then eventually get all the stuff, and leave. 797 00:44:30,570 --> 00:44:33,130 Maybe they only send a few people to each star system. 798 00:44:33,130 --> 00:44:37,180 Then they let it get it to a certain population. 799 00:44:37,180 --> 00:44:39,180 See if they wait a certain number of generations 800 00:44:39,180 --> 00:44:43,789 before the next wave of colonization gets sent down. 801 00:44:43,789 --> 00:44:46,080 If you make the colonization process sufficiently slow, 802 00:44:46,080 --> 00:44:48,360 then obviously you can get a number much larger 803 00:44:48,360 --> 00:44:51,130 than 10 million or 20 million years. 804 00:44:51,130 --> 00:44:55,230 In fact, you can get a number as large as you want. 805 00:44:55,230 --> 00:44:57,680 So maybe that's the explanation. 806 00:45:00,840 --> 00:45:03,750 Extraterrestrial intelligence does exist. 807 00:45:03,750 --> 00:45:05,749 But they haven't had time to reach us. 808 00:45:05,749 --> 00:45:07,290 Not because they lack the technology, 809 00:45:07,290 --> 00:45:10,650 but because it takes long to colonize. 810 00:45:10,650 --> 00:45:14,500 Maybe that's the explanation. 811 00:45:14,500 --> 00:45:22,110 But it's also conceivable that they don't even 812 00:45:22,110 --> 00:45:23,940 want to colonize the galaxy. 813 00:45:23,940 --> 00:45:26,810 They might not be interested in our system, 814 00:45:26,810 --> 00:45:28,347 or our solar system. 815 00:45:28,347 --> 00:45:29,430 We think it's interesting. 816 00:45:29,430 --> 00:45:30,757 We think they want to visit us. 817 00:45:30,757 --> 00:45:31,840 I mean, we're intelligent. 818 00:45:31,840 --> 00:45:32,630 We're smart. 819 00:45:32,630 --> 00:45:34,171 But maybe they don't maybe they don't 820 00:45:34,171 --> 00:45:37,020 see any value in visiting. 821 00:45:42,760 --> 00:45:45,100 Maybe it's too expensive. 822 00:45:45,100 --> 00:45:46,360 That's another possibility. 823 00:45:46,360 --> 00:45:49,690 Maybe it's too expensive to do this large scale 824 00:45:49,690 --> 00:45:51,790 kind of a colonization. 825 00:45:51,790 --> 00:45:55,510 But this would have to be true for 826 00:45:55,510 --> 00:45:59,830 every single intelligent civilization that 827 00:45:59,830 --> 00:46:01,390 formed in our galaxy's past. 828 00:46:01,390 --> 00:46:03,180 I mean, if it's impossible for one, 829 00:46:03,180 --> 00:46:05,010 it might be possible for another. 830 00:46:05,010 --> 00:46:06,760 They might not take as long colonizing it. 831 00:46:06,760 --> 00:46:11,020 They might not take as long getting settled on the planets 832 00:46:11,020 --> 00:46:12,970 before they move outward again. 833 00:46:12,970 --> 00:46:15,880 This would have to be true for every single civilization that 834 00:46:15,880 --> 00:46:17,020 formed in the galaxy. 835 00:46:17,020 --> 00:46:19,870 None of them were able to reach us in time. 836 00:46:22,690 --> 00:46:23,530 Who knows? 837 00:46:23,530 --> 00:46:24,370 Nobody really knows. 838 00:46:27,735 --> 00:46:29,110 We have a hard time understanding 839 00:46:29,110 --> 00:46:32,896 how our intelligence works. 840 00:46:32,896 --> 00:46:34,270 We have a hard time understanding 841 00:46:34,270 --> 00:46:36,831 how an extraterrestrial intelligence. 842 00:46:36,831 --> 00:46:38,830 So we must have a really hard time understanding 843 00:46:38,830 --> 00:46:41,590 how all extraterrestrial intelligence works. 844 00:46:46,380 --> 00:46:48,820 So maybe it's actually impossible for them 845 00:46:48,820 --> 00:46:52,600 to get here in time. 846 00:46:52,600 --> 00:46:54,850 It seems possible for them to get here in principle. 847 00:46:54,850 --> 00:46:57,910 But maybe they just don't have the amount of time to get here. 848 00:46:57,910 --> 00:47:00,550 So we don't see them here. 849 00:47:00,550 --> 00:47:03,880 So that would explain the first part of why they're not here. 850 00:47:03,880 --> 00:47:05,980 It just takes too long to get here. 851 00:47:05,980 --> 00:47:07,810 That would explain that part. 852 00:47:07,810 --> 00:47:11,860 But it doesn't explain why we don't seem to see them. 853 00:47:11,860 --> 00:47:15,310 There's been an industry of searching 854 00:47:15,310 --> 00:47:18,320 for signs of infinite intelligence 855 00:47:18,320 --> 00:47:21,760 now that's been going on for over 40 years. 856 00:47:21,760 --> 00:47:24,260 We've been pointing our telescopes in the sky. 857 00:47:24,260 --> 00:47:27,220 We've been trying to look for signals that might indicate 858 00:47:27,220 --> 00:47:31,420 that some signs of intelligent life besides our own 859 00:47:31,420 --> 00:47:35,064 exists out there in the universe-- 860 00:47:35,064 --> 00:47:35,980 the observed universe. 861 00:47:35,980 --> 00:47:38,770 We can't see the whole universe. 862 00:47:38,770 --> 00:47:42,350 And so this search has been going on for a long time. 863 00:47:42,350 --> 00:47:46,530 Definitely the most well known search that has been going on 864 00:47:46,530 --> 00:47:51,670 is known as SETI, which stands for Search for Extraterrestrial 865 00:47:51,670 --> 00:47:53,650 Intelligence, SETI. 866 00:47:53,650 --> 00:47:56,720 That's been going on for a long time. 867 00:47:56,720 --> 00:47:58,930 But they've never found any clear signs 868 00:47:58,930 --> 00:48:02,240 of extraterrestrial intelligence. 869 00:48:02,240 --> 00:48:06,702 So now, we need to explain, well, why don't we 870 00:48:06,702 --> 00:48:07,660 seem to hear from them? 871 00:48:07,660 --> 00:48:11,149 We need to explain that now. 872 00:48:11,149 --> 00:48:12,940 Does anybody have an explanation for why we 873 00:48:12,940 --> 00:48:14,978 don't seem to hear from them? 874 00:48:14,978 --> 00:48:16,460 AUDIENCE: [INAUDIBLE]. 875 00:48:32,869 --> 00:48:34,660 NICHOLAS DIBELLA: The way of talking to us, 876 00:48:34,660 --> 00:48:36,490 the way of sending signals to us, 877 00:48:36,490 --> 00:48:39,284 is not restricted to just answering our calls. 878 00:48:39,284 --> 00:48:41,200 They could be signaling us before we even have 879 00:48:41,200 --> 00:48:43,060 the technology to signal them. 880 00:48:43,060 --> 00:48:44,435 They don't have to wait for us. 881 00:48:44,435 --> 00:48:46,810 They could have been sending stuff for millions of years, 882 00:48:46,810 --> 00:48:49,720 for all we know. 883 00:48:49,720 --> 00:48:50,522 Yes? 884 00:48:50,522 --> 00:48:51,938 AUDIENCE: [INAUDIBLE]. 885 00:48:54,800 --> 00:48:56,550 NICHOLAS DIBELLA: Maybe they're surrounded 886 00:48:56,550 --> 00:49:02,550 by mini black holes that prevent them from reaching us. 887 00:49:02,550 --> 00:49:07,350 Maybe, but I don't think there's much observational evidence 888 00:49:07,350 --> 00:49:12,020 for a whole slew of mini black holes 889 00:49:12,020 --> 00:49:16,300 permeating through the whole galaxy eating civilizations, 890 00:49:16,300 --> 00:49:17,671 not much evidence for that. 891 00:49:17,671 --> 00:49:18,170 Yes? 892 00:49:18,170 --> 00:49:19,565 AUDIENCE: [INAUDIBLE]. 893 00:49:22,820 --> 00:49:26,970 NICHOLAS DIBELLA: Oh yeah, so that's a valid criticism 894 00:49:26,970 --> 00:49:27,810 against the program. 895 00:49:30,640 --> 00:49:35,880 So the way we've been trying to search for these signals 896 00:49:35,880 --> 00:49:37,875 has been through electromagnetic waves. 897 00:49:37,875 --> 00:49:39,250 We've been trying to find signals 898 00:49:39,250 --> 00:49:40,620 in electromagnetic waves-- 899 00:49:40,620 --> 00:49:45,090 so radio waves, microwaves, visible light, things, red, 900 00:49:45,090 --> 00:49:48,440 blue, gamma rays, x-rays. 901 00:49:48,440 --> 00:49:50,117 These are all electromagnetic waves. 902 00:49:50,117 --> 00:49:52,200 And we've primarily been looking into radio waves. 903 00:49:52,200 --> 00:49:58,250 We've also looked in optical, visible light. 904 00:49:58,250 --> 00:50:02,960 But we haven't seen any clear signs from these signals. 905 00:50:02,960 --> 00:50:06,780 We haven't seen any signals in these electromagnetic waves 906 00:50:06,780 --> 00:50:07,930 that we've been receiving. 907 00:50:07,930 --> 00:50:09,555 And we've been looking for a long time. 908 00:50:09,555 --> 00:50:11,790 So it's possible that maybe-- 909 00:50:11,790 --> 00:50:14,672 well, maybe we're not even looking at them the right way. 910 00:50:14,672 --> 00:50:16,380 Maybe they don't send signals in the form 911 00:50:16,380 --> 00:50:19,470 of electromagnetic waves. 912 00:50:19,470 --> 00:50:21,600 There are other possibilities. 913 00:50:21,600 --> 00:50:24,150 Electromagnetic waves seem like the natural choice 914 00:50:24,150 --> 00:50:26,432 of sending signals to us. 915 00:50:26,432 --> 00:50:28,140 Electromagnetic waves travel at the speed 916 00:50:28,140 --> 00:50:32,580 of light, which is theoretically the fastest you can go. 917 00:50:32,580 --> 00:50:34,860 But maybe they don't use electromagnetic waves. 918 00:50:34,860 --> 00:50:37,500 Maybe they use gravitational waves. 919 00:50:37,500 --> 00:50:40,500 Gravitational waves are similar to electromagnetic waves. 920 00:50:40,500 --> 00:50:42,680 They also travel at the speed of light. 921 00:50:42,680 --> 00:50:44,300 But they're also very different. 922 00:50:44,300 --> 00:50:45,990 The way to produce a gravitational wave 923 00:50:45,990 --> 00:50:49,620 is to take a mass, and basically to shake it. 924 00:50:52,380 --> 00:50:54,530 And that produces gravitational waves. 925 00:50:54,530 --> 00:50:57,270 The problem with that is that gravitational waves 926 00:50:57,270 --> 00:50:59,620 are extremely weak. 927 00:50:59,620 --> 00:51:03,440 In fact, to date nobody has ever-- 928 00:51:03,440 --> 00:51:06,480 we as a civilization, we have never directly detected 929 00:51:06,480 --> 00:51:08,200 gravitational waves. 930 00:51:08,200 --> 00:51:10,110 They're just so weak. 931 00:51:10,110 --> 00:51:12,460 People are certainly trying. 932 00:51:12,460 --> 00:51:15,110 And we may very well detect the first gravitational wave 933 00:51:15,110 --> 00:51:16,380 in five years or so. 934 00:51:16,380 --> 00:51:17,785 It's definitely possible. 935 00:51:20,750 --> 00:51:22,654 But we haven't to date. 936 00:51:22,654 --> 00:51:24,570 We've indirectly observed gravitational waves. 937 00:51:24,570 --> 00:51:25,980 We are pretty sure they exist. 938 00:51:25,980 --> 00:51:27,515 We're very sure they exist. 939 00:51:27,515 --> 00:51:29,640 There are consequences of Einstein's general theory 940 00:51:29,640 --> 00:51:30,247 of relativity. 941 00:51:30,247 --> 00:51:31,830 But we've never directly observed one. 942 00:51:31,830 --> 00:51:34,560 So it's possible that aliens, for one reason or another, 943 00:51:34,560 --> 00:51:38,610 are sending signals encoded in gravitational waves. 944 00:51:38,610 --> 00:51:43,092 And we just have no chance of seeing those signals at all, 945 00:51:43,092 --> 00:51:44,300 because we can't detect them. 946 00:51:44,300 --> 00:51:51,480 So maybe the aliens, they prefer to use gravitational waves, 947 00:51:51,480 --> 00:51:54,480 because they only want to communicate with civilizations 948 00:51:54,480 --> 00:51:57,840 that are elite enough to have developed the technology 949 00:51:57,840 --> 00:51:59,639 to detect gravitational waves. 950 00:51:59,639 --> 00:52:00,180 I don't know. 951 00:52:00,180 --> 00:52:02,110 Who knows? 952 00:52:02,110 --> 00:52:02,859 Yes? 953 00:52:02,859 --> 00:52:04,296 AUDIENCE: [INAUDIBLE]. 954 00:52:11,010 --> 00:52:13,860 NICHOLAS DIBELLA: So what physical conditions 955 00:52:13,860 --> 00:52:17,892 can produce detectable gravitational waves, 956 00:52:17,892 --> 00:52:18,600 is your question? 957 00:52:22,230 --> 00:52:25,380 Well, it certainly won't detect this. 958 00:52:25,380 --> 00:52:29,700 Only the most violent disturbances 959 00:52:29,700 --> 00:52:32,130 in matter can you really detect, at least 960 00:52:32,130 --> 00:52:36,964 today do we have any chance of hoping to detect. 961 00:52:36,964 --> 00:52:38,380 I don't know a whole lot about it. 962 00:52:38,380 --> 00:52:41,910 But I think we might be able to detect 963 00:52:41,910 --> 00:52:43,559 collisions between black holes. 964 00:52:43,559 --> 00:52:44,100 I'm not sure. 965 00:52:44,100 --> 00:52:45,690 I don't really know too much about it. 966 00:52:45,690 --> 00:52:49,860 But they have to be the most violent disturbances 967 00:52:49,860 --> 00:52:55,630 in matter, definitely nothing that we can create right now. 968 00:52:55,630 --> 00:52:59,109 So that's another thing about the extraterrestrial 969 00:52:59,109 --> 00:52:59,650 intelligence. 970 00:52:59,650 --> 00:53:07,220 They would have to be able to create very strong disturbances 971 00:53:07,220 --> 00:53:10,140 in gravitational fields to produce 972 00:53:10,140 --> 00:53:12,220 detectable gravitational waves. 973 00:53:12,220 --> 00:53:17,850 Although, maybe they purposely choose 974 00:53:17,850 --> 00:53:21,029 not to produce very strong gravitational waves, 975 00:53:21,029 --> 00:53:22,570 and just want to give us a hard time. 976 00:53:22,570 --> 00:53:24,190 They want to give us a challenge. 977 00:53:24,190 --> 00:53:25,800 So only if they are advanced enough 978 00:53:25,800 --> 00:53:28,140 to take these gravitational waves this weak will we 979 00:53:28,140 --> 00:53:29,160 communicate with them. 980 00:53:29,160 --> 00:53:30,279 Who knows? 981 00:53:30,279 --> 00:53:32,320 But they might be using these gravitational waves 982 00:53:32,320 --> 00:53:33,670 to communicate with us. 983 00:53:33,670 --> 00:53:35,461 AUDIENCE: How weak are gravitational waves? 984 00:53:35,461 --> 00:53:37,792 Say, you smashed two planets together. 985 00:53:37,792 --> 00:53:39,750 NICHOLAS DIBELLA: Smashed two flames together-- 986 00:53:39,750 --> 00:53:40,860 planets. 987 00:53:40,860 --> 00:53:43,080 I don't think that would produce detectable-- 988 00:53:43,080 --> 00:53:47,850 I mean, I always forget the numbers. 989 00:53:47,850 --> 00:53:53,830 But if you sent a gravitational wave of reasonable strength 990 00:53:53,830 --> 00:53:57,850 through maybe it's like a million-- 991 00:53:57,850 --> 00:54:00,490 I don't know, like 100 light years of lead, 992 00:54:00,490 --> 00:54:06,590 then it would only be like 50% diminished. 993 00:54:06,590 --> 00:54:08,340 I don't have the numbers offhand. 994 00:54:08,340 --> 00:54:14,540 But they're so weak that they're very, 995 00:54:14,540 --> 00:54:19,050 very, very, very, slightly interact with matter 996 00:54:19,050 --> 00:54:20,740 that it's just so hard to detect them. 997 00:54:23,730 --> 00:54:27,730 And there's actually another means of communication 998 00:54:27,730 --> 00:54:30,130 that they might use, which is similarly weak. 999 00:54:30,130 --> 00:54:33,730 They might use neutrinos. 1000 00:54:33,730 --> 00:54:36,880 Neutrinos are these very, very light particles. 1001 00:54:36,880 --> 00:54:40,930 They travel very fast, not as fast as the speed of light, 1002 00:54:40,930 --> 00:54:42,550 slightly less. 1003 00:54:42,550 --> 00:54:43,870 But they travel very fast. 1004 00:54:43,870 --> 00:54:45,190 And they're very light. 1005 00:54:45,190 --> 00:54:48,550 And they're very weakly interacting. 1006 00:54:48,550 --> 00:54:51,500 I do have the numbers for the neutrinos. 1007 00:54:51,500 --> 00:54:56,240 So these are written somewhere. 1008 00:54:56,240 --> 00:55:00,970 Yeah, so if you sent some neutrinos 1009 00:55:00,970 --> 00:55:04,690 through 1,000 light years of lead-- 1010 00:55:04,690 --> 00:55:06,840 it would take about 1,000 light years of lead 1011 00:55:06,840 --> 00:55:09,910 to have a significant chance of stopping a neutrino. 1012 00:55:09,910 --> 00:55:11,840 That's how weak neutrinos are. 1013 00:55:11,840 --> 00:55:14,940 And gravitational waves are even weaker than that. 1014 00:55:14,940 --> 00:55:17,650 We have detected neutrinos. 1015 00:55:17,650 --> 00:55:20,710 Now, we have neutrino detectors, where we essentially 1016 00:55:20,710 --> 00:55:22,984 make the neutrinos travel through a lot of matter 1017 00:55:22,984 --> 00:55:25,150 before we can detect them is essentially what we do. 1018 00:55:25,150 --> 00:55:26,816 But we are able to detect neutrinos now. 1019 00:55:26,816 --> 00:55:28,660 We have neutrino telescopes. 1020 00:55:31,690 --> 00:55:35,890 But we probably wouldn't be able to detect any neutrino 1021 00:55:35,890 --> 00:55:37,990 signals if they send any. 1022 00:55:37,990 --> 00:55:40,240 So it's totally possible that we're not looking 1023 00:55:40,240 --> 00:55:41,920 at the sky the right way. 1024 00:55:41,920 --> 00:55:44,010 We're just looking at electromagnetic waves. 1025 00:55:44,010 --> 00:55:45,718 We're not looking at gravitational waves, 1026 00:55:45,718 --> 00:55:47,290 or neutrinos. 1027 00:55:47,290 --> 00:55:50,010 Or maybe they use tachyons. 1028 00:55:50,010 --> 00:55:51,940 Tachyons are hypothetical particles 1029 00:55:51,940 --> 00:55:56,420 that actually travel faster than light, which might exist. 1030 00:55:56,420 --> 00:55:57,910 We've never detected them. 1031 00:55:57,910 --> 00:55:59,830 According to relativity, strictly speaking, 1032 00:55:59,830 --> 00:56:02,687 you can't take a particle and accelerate it up 1033 00:56:02,687 --> 00:56:05,020 to the speed of light, and then past the speed of light. 1034 00:56:05,020 --> 00:56:06,811 It would take an infinite amount of energy. 1035 00:56:06,811 --> 00:56:08,020 But you can have particles-- 1036 00:56:08,020 --> 00:56:09,895 I mean, special relativity doesn't forbid it. 1037 00:56:09,895 --> 00:56:12,010 You could have particles that always travel faster 1038 00:56:12,010 --> 00:56:13,010 than the speed of light. 1039 00:56:13,010 --> 00:56:15,590 They're called tachyons. 1040 00:56:15,590 --> 00:56:17,660 We've never detected a tachyon. 1041 00:56:17,660 --> 00:56:20,145 We have no evidence at all that tachyons exist. 1042 00:56:20,145 --> 00:56:21,520 But you can think, maybe they do. 1043 00:56:25,709 --> 00:56:27,250 We have no idea of manipulating them, 1044 00:56:27,250 --> 00:56:28,570 because we don't even know they exist. 1045 00:56:28,570 --> 00:56:29,680 But maybe they do exist, and aliens 1046 00:56:29,680 --> 00:56:30,780 know how to manipulate them. 1047 00:56:30,780 --> 00:56:32,170 And that would certainly be a much more efficient way 1048 00:56:32,170 --> 00:56:34,628 of communicating, because they can travel faster than light 1049 00:56:34,628 --> 00:56:37,030 and get to us in a quicker amount of time. 1050 00:56:37,030 --> 00:56:38,970 Who knows? 1051 00:56:38,970 --> 00:56:41,590 But it's certainly possible that we're looking 1052 00:56:41,590 --> 00:56:44,152 at the sky in the wrong way. 1053 00:56:44,152 --> 00:56:45,610 It could also be that we're looking 1054 00:56:45,610 --> 00:56:46,776 at the sky in the right way. 1055 00:56:46,776 --> 00:56:49,040 Maybe aliens are sending electromagnetic signals. 1056 00:56:49,040 --> 00:56:50,831 But we're looking at the wrong frequencies. 1057 00:56:50,831 --> 00:56:54,730 And the electromagnetic spectrum spans a wide range 1058 00:56:54,730 --> 00:57:00,290 of frequencies, from the very short wavelength gamma rays, 1059 00:57:00,290 --> 00:57:03,970 x-rays, to microwaves, to optical lights, 1060 00:57:03,970 --> 00:57:09,510 to infrared, to radio waves. 1061 00:57:09,510 --> 00:57:11,950 It forms a very vast spectrum. 1062 00:57:11,950 --> 00:57:14,795 And, mainly, we've been looking at the radio waves. 1063 00:57:14,795 --> 00:57:16,420 We've also been looking in the optical, 1064 00:57:16,420 --> 00:57:18,520 and I think maybe also gamma. 1065 00:57:18,520 --> 00:57:21,010 But we haven't been looking at that many different 1066 00:57:21,010 --> 00:57:22,990 frequencies. 1067 00:57:22,990 --> 00:57:25,990 There are certain frequencies that we 1068 00:57:25,990 --> 00:57:29,200 look at that seem natural. 1069 00:57:29,200 --> 00:57:31,690 For example, it seems reasonable to think 1070 00:57:31,690 --> 00:57:35,290 that an intelligent civilization will have discovered 1071 00:57:35,290 --> 00:57:39,210 that there's a very prominent wavelength that 1072 00:57:39,210 --> 00:57:42,910 gets emitted from hydrogen throughout the universe. 1073 00:57:42,910 --> 00:57:45,690 It's called the 21 centimeter line. 1074 00:57:45,690 --> 00:57:47,440 You would think that they know about that. 1075 00:57:47,440 --> 00:57:49,540 So maybe they would try to send something related 1076 00:57:49,540 --> 00:57:52,540 to that frequency, something related to that wavelength, 21 1077 00:57:52,540 --> 00:57:53,260 centimeters. 1078 00:57:53,260 --> 00:57:55,480 Maybe they do twice that, or three times 1079 00:57:55,480 --> 00:57:57,040 that, or pi times that. 1080 00:57:57,040 --> 00:57:59,590 Presumably, they know about pi. 1081 00:57:59,590 --> 00:58:01,510 Who knows? 1082 00:58:01,510 --> 00:58:04,360 So we've really been looking at a handful of frequencies. 1083 00:58:04,360 --> 00:58:07,259 And we haven't seen anything. 1084 00:58:07,259 --> 00:58:08,800 So maybe that means we're not looking 1085 00:58:08,800 --> 00:58:09,880 in the right frequencies. 1086 00:58:09,880 --> 00:58:14,690 Maybe we need to broaden our horizons, maybe. 1087 00:58:14,690 --> 00:58:18,820 It could also be that our search technology is just not 1088 00:58:18,820 --> 00:58:21,220 sensitive enough. 1089 00:58:21,220 --> 00:58:22,480 The universe is a big place. 1090 00:58:22,480 --> 00:58:25,120 And there are a lot of things going on in the universe. 1091 00:58:25,120 --> 00:58:27,160 And so there's a lot of noise. 1092 00:58:27,160 --> 00:58:30,184 And we need, somehow, to distinguish the noise 1093 00:58:30,184 --> 00:58:30,850 from the signal. 1094 00:58:30,850 --> 00:58:33,820 We want to see the signals that they're sending, not the noise. 1095 00:58:33,820 --> 00:58:37,360 Maybe the signal is just mushed up with the noise 1096 00:58:37,360 --> 00:58:39,599 somewhere that we can't distinguish it. 1097 00:58:39,599 --> 00:58:41,140 Maybe that's the problem, and we need 1098 00:58:41,140 --> 00:58:44,210 to increase our sensitivities. 1099 00:58:44,210 --> 00:58:46,460 So it's entirely possible that they are communicating, 1100 00:58:46,460 --> 00:58:47,620 they're trying to communicate with us. 1101 00:58:47,620 --> 00:58:49,661 Or maybe they're just inadvertently communicating 1102 00:58:49,661 --> 00:58:51,080 with us by sending signals. 1103 00:58:51,080 --> 00:58:54,109 We're just not observing them, because we're not looking 1104 00:58:54,109 --> 00:58:55,150 at the right frequencies. 1105 00:58:55,150 --> 00:58:58,300 Or we're not even looking at the right kind of thing. 1106 00:58:58,300 --> 00:59:00,300 We're not looking at electromagnetic waves. 1107 00:59:00,300 --> 00:59:01,360 And we're not looking at the right kind of thing. 1108 00:59:01,360 --> 00:59:03,310 It could be graviational waves, et cetera. 1109 00:59:03,310 --> 00:59:06,430 It could also be that we're not doing 1110 00:59:06,430 --> 00:59:08,970 sensitive enough searches. 1111 00:59:08,970 --> 00:59:12,039 So over the years, people have gradually 1112 00:59:12,039 --> 00:59:14,080 increased sensitivity, gradually increased number 1113 00:59:14,080 --> 00:59:15,040 of frequencies. 1114 00:59:15,040 --> 00:59:19,147 And this continues to expand, as the years go on. 1115 00:59:19,147 --> 00:59:21,730 And the people in SETI, they're really hopeful that eventually 1116 00:59:21,730 --> 00:59:22,563 we'll see something. 1117 00:59:22,563 --> 00:59:24,940 And so they keep expanding, expanding, expanding 1118 00:59:24,940 --> 00:59:28,390 their sensitivities and their ranges. 1119 00:59:28,390 --> 00:59:31,379 It could also be that the aliens are there, 1120 00:59:31,379 --> 00:59:32,920 and they're just not sending signals. 1121 00:59:32,920 --> 00:59:35,260 Maybe they're trying to conceal themselves. 1122 00:59:35,260 --> 00:59:38,490 Maybe they don't want their presence to be known. 1123 00:59:38,490 --> 00:59:39,490 That's also possible. 1124 00:59:42,310 --> 00:59:44,800 Or maybe we're just not looking in the right place. 1125 00:59:44,800 --> 00:59:47,180 Maybe they're not there, but they're over there. 1126 00:59:47,180 --> 00:59:48,660 That's also possible. 1127 00:59:48,660 --> 00:59:50,320 We just don't know. 1128 00:59:50,320 --> 00:59:55,720 So these other explanations of the Fermi paradox. 1129 00:59:55,720 --> 00:59:57,490 We don't know. 1130 00:59:57,490 --> 01:00:00,095 So we look at two general types of explanations 1131 01:00:00,095 --> 01:00:00,970 to the Fermi paradox. 1132 01:00:00,970 --> 01:00:02,380 Where is everybody? 1133 01:00:02,380 --> 01:00:04,630 We looked at two different explanations. 1134 01:00:04,630 --> 01:00:09,330 One is that, they do exist, and they're here. 1135 01:00:13,610 --> 01:00:17,380 The evidence for that's a little shoddy, a little skimpy. 1136 01:00:17,380 --> 01:00:19,570 But the second possibility is more intriguing, 1137 01:00:19,570 --> 01:00:21,102 more interesting in my opinion. 1138 01:00:21,102 --> 01:00:23,560 It's that they exist, but they haven't communicated with us 1139 01:00:23,560 --> 01:00:27,100 yet, seemingly. 1140 01:00:27,100 --> 01:00:29,785 Maybe it takes too long for them to get here, 1141 01:00:29,785 --> 01:00:31,980 and they just haven't gotten here yet. 1142 01:00:31,980 --> 01:00:33,040 Maybe it's too expensive. 1143 01:00:33,040 --> 01:00:36,040 Maybe they don't want to come here. 1144 01:00:36,040 --> 01:00:37,540 Who knows? 1145 01:00:37,540 --> 01:00:40,126 That would explain why they're not here. 1146 01:00:40,126 --> 01:00:41,500 We would also like to explain why 1147 01:00:41,500 --> 01:00:43,958 we don't see them in the sky, why they haven't communicated 1148 01:00:43,958 --> 01:00:45,080 with us. 1149 01:00:45,080 --> 01:00:46,426 And we don't know that for sure. 1150 01:00:46,426 --> 01:00:48,550 We don't know if they haven't communicated with us. 1151 01:00:48,550 --> 01:00:50,680 It could just be that we haven't been searching 1152 01:00:50,680 --> 01:00:52,120 for them in the right way. 1153 01:00:52,120 --> 01:00:55,660 We've been searching for them electromagnetically. 1154 01:00:55,660 --> 01:00:58,230 They could be using some other kind of signals. 1155 01:00:58,230 --> 01:01:01,620 And we've only been searching in a small window. 1156 01:01:01,620 --> 01:01:03,957 And it's totally conceivable that they 1157 01:01:03,957 --> 01:01:06,040 would try to contact us in another kind of window, 1158 01:01:06,040 --> 01:01:07,730 a different kind of frequency range. 1159 01:01:07,730 --> 01:01:10,510 It's also possible that they're just 1160 01:01:10,510 --> 01:01:14,030 hard to distinguish from the noise that we observe. 1161 01:01:14,030 --> 01:01:16,240 There's one final possibility. 1162 01:01:16,240 --> 01:01:20,080 And it's probably the darkest one, and the gloomiest. 1163 01:01:20,080 --> 01:01:32,830 It's that they don't exist. 1164 01:01:32,830 --> 01:01:35,480 This would certainly explain why we don't see them, 1165 01:01:35,480 --> 01:01:37,146 and why we don't seem to hear from them. 1166 01:01:39,140 --> 01:01:41,430 But, admittedly, it's probably the saddest one. 1167 01:01:41,430 --> 01:01:46,540 But it's a very real possibility that we have to consider. 1168 01:01:46,540 --> 01:01:50,320 And it's not only the final possibility to consider. 1169 01:01:50,320 --> 01:01:53,140 And so we might want it by process of elimination. 1170 01:01:53,140 --> 01:01:55,000 But there are a lot of reasons for thinking 1171 01:01:55,000 --> 01:01:57,160 that we are actually alone in the galaxy, 1172 01:01:57,160 --> 01:02:01,180 or we are actually alone in the observed universe. 1173 01:02:01,180 --> 01:02:04,210 It could be that life is just-- 1174 01:02:04,210 --> 01:02:07,450 intelligent life is just very, very rare. 1175 01:02:07,450 --> 01:02:10,840 Our current understanding of the way life formed, 1176 01:02:10,840 --> 01:02:12,930 our current modern understanding, 1177 01:02:12,930 --> 01:02:14,240 is through evolution. 1178 01:02:14,240 --> 01:02:17,469 So a long time ago, there existed a bunch of stuff 1179 01:02:17,469 --> 01:02:18,010 on the Earth. 1180 01:02:18,010 --> 01:02:19,310 The Earth existed. 1181 01:02:19,310 --> 01:02:20,860 There's a bunch of molecules. 1182 01:02:20,860 --> 01:02:23,380 And, occasionally, some of these molecules 1183 01:02:23,380 --> 01:02:26,140 would interact in a favorable way. 1184 01:02:26,140 --> 01:02:28,690 They're all moving around in random directions, 1185 01:02:28,690 --> 01:02:30,760 interacting with each other in random ways. 1186 01:02:30,760 --> 01:02:33,610 But, eventually, a fluke will occur, 1187 01:02:33,610 --> 01:02:35,740 a statistical fluctuation will occur. 1188 01:02:35,740 --> 01:02:37,810 And the molecules will interact in a certain way 1189 01:02:37,810 --> 01:02:39,760 to produce something that today we 1190 01:02:39,760 --> 01:02:45,050 would classify as being a meaningful sort of molecule, 1191 01:02:45,050 --> 01:02:46,780 an ingredient of life. 1192 01:02:46,780 --> 01:02:50,650 Eventually, for example, amino acids 1193 01:02:50,650 --> 01:02:58,700 formed through these random interactions of molecules. 1194 01:02:58,700 --> 01:03:01,300 Now, it's very unlikely that it does occur. 1195 01:03:01,300 --> 01:03:05,800 But, remember, if you try doing something 1196 01:03:05,800 --> 01:03:08,650 many, many times, if you wait long enough, then 1197 01:03:08,650 --> 01:03:11,200 eventually it's going to happen, regardless of how 1198 01:03:11,200 --> 01:03:12,430 small the possibility is. 1199 01:03:12,430 --> 01:03:17,360 It might be extremely small probability 1200 01:03:17,360 --> 01:03:19,820 that the amino acids do form. 1201 01:03:19,820 --> 01:03:21,680 But if you wait long enough, they do. 1202 01:03:21,680 --> 01:03:25,561 And once you get things like amino acids, 1203 01:03:25,561 --> 01:03:27,310 you can start getting more complex things. 1204 01:03:30,700 --> 01:03:33,760 Our current understanding is that eventually, 1205 01:03:33,760 --> 01:03:39,450 very simple cells forms, very primitive kinds of bacteria. 1206 01:03:39,450 --> 01:03:43,200 And then from bacteria, you had eukaryotic cells. 1207 01:03:43,200 --> 01:03:45,640 These are cells that have nuclei. 1208 01:03:45,640 --> 01:03:48,520 Then from eukaryotic cells, you get multicellular organisms, 1209 01:03:48,520 --> 01:03:49,960 things that are more complex. 1210 01:03:49,960 --> 01:03:52,720 And you wait long enough, you let this process go on 1211 01:03:52,720 --> 01:03:56,454 for 4.6 billion years, a vast amount of time, 1212 01:03:56,454 --> 01:03:58,870 it's an insane amount of time you, let this process go on, 1213 01:03:58,870 --> 01:04:00,940 you let these random processes occur 1214 01:04:00,940 --> 01:04:05,360 for a vast amount of time, and eventually you get this. 1215 01:04:05,360 --> 01:04:08,786 You get the wide diversity in life that you see today. 1216 01:04:08,786 --> 01:04:10,660 And, in particular, you get intelligent life. 1217 01:04:10,660 --> 01:04:13,730 At least for us, we got intelligent life. 1218 01:04:13,730 --> 01:04:16,810 But it could be that the way it happened here 1219 01:04:16,810 --> 01:04:18,802 is vastly improbable. 1220 01:04:18,802 --> 01:04:20,260 I mean, there are a number of steps 1221 01:04:20,260 --> 01:04:22,960 that have to occur for the evolution of intelligent life 1222 01:04:22,960 --> 01:04:25,810 to happen. 1223 01:04:25,810 --> 01:04:27,910 One of them is you have to get life from non-life, 1224 01:04:27,910 --> 01:04:28,700 some sort of way. 1225 01:04:31,270 --> 01:04:34,070 You let these random collisions happen for a long enough time, 1226 01:04:34,070 --> 01:04:37,204 they eventually get a cellular type of thing 1227 01:04:37,204 --> 01:04:38,620 from a non-cellular type of thing. 1228 01:04:38,620 --> 01:04:40,480 You get life from non-life. 1229 01:04:40,480 --> 01:04:46,130 And it could be that that's just very, very unlikely to happen. 1230 01:04:46,130 --> 01:04:48,310 And we're the only place in the whole galaxy where 1231 01:04:48,310 --> 01:04:51,970 it did happen, perhaps the only place in the whole observed 1232 01:04:51,970 --> 01:04:53,410 universe where it did happen. 1233 01:04:53,410 --> 01:04:54,034 Yes? 1234 01:04:54,034 --> 01:04:56,200 AUDIENCE: Isn't what we were talking about last week 1235 01:04:56,200 --> 01:04:58,450 with the type of multiverse, doesn't that kind of 1236 01:04:58,450 --> 01:05:00,900 prove that there's other life out there? 1237 01:05:00,900 --> 01:05:02,950 NICHOLAS DIBELLA: Well, certainly, 1238 01:05:02,950 --> 01:05:08,020 if the universe is infinite, definitely there's 1239 01:05:08,020 --> 01:05:10,209 other intelligent life out there. 1240 01:05:10,209 --> 01:05:12,250 But we don't observe the whole infinite universe. 1241 01:05:12,250 --> 01:05:14,800 We only observe a small, finite portion of it. 1242 01:05:14,800 --> 01:05:17,380 It's actually very large. 1243 01:05:17,380 --> 01:05:19,420 I threw some numbers out before. 1244 01:05:19,420 --> 01:05:23,510 But we don't observe the whole universe. 1245 01:05:23,510 --> 01:05:26,614 So we might effectively be the only intelligent life 1246 01:05:26,614 --> 01:05:27,280 in the universe. 1247 01:05:27,280 --> 01:05:29,970 At least our universe, we're the only intelligent life. 1248 01:05:29,970 --> 01:05:33,160 Or at least in our galaxy, that might be the case. 1249 01:05:33,160 --> 01:05:36,100 So there could be some kind of a-- 1250 01:05:36,100 --> 01:05:36,850 yes, it's raining. 1251 01:05:40,610 --> 01:05:43,990 There might be some kind of a really improbable step that 1252 01:05:43,990 --> 01:05:46,080 occurred in the sequence of steps that 1253 01:05:46,080 --> 01:05:47,330 had to occur for life to form. 1254 01:05:47,330 --> 01:05:49,095 Maybe it was getting life from non-life. 1255 01:05:49,095 --> 01:05:50,470 Maybe it is getting multicellular 1256 01:05:50,470 --> 01:05:52,540 from single-celled organisms. 1257 01:05:52,540 --> 01:05:59,020 Maybe it was getting big brains that was hard to occur, 1258 01:05:59,020 --> 01:06:01,661 that was very unlikely. 1259 01:06:01,661 --> 01:06:03,410 So it's reasonable to postulate that there 1260 01:06:03,410 --> 01:06:05,560 was some kind of a great filter that 1261 01:06:05,560 --> 01:06:08,860 acted on the development of our species, 1262 01:06:08,860 --> 01:06:12,100 that one or more steps had to be extremely improbable for it 1263 01:06:12,100 --> 01:06:13,030 to happen. 1264 01:06:13,030 --> 01:06:14,946 And it's so improbable that we're 1265 01:06:14,946 --> 01:06:17,320 the only intelligent life in the whole observed universe, 1266 01:06:17,320 --> 01:06:20,470 or the whole galaxy. 1267 01:06:20,470 --> 01:06:22,670 And if that's the case, that would very easily, 1268 01:06:22,670 --> 01:06:27,210 very elegantly, explain why we don't see anyone else. 1269 01:06:27,210 --> 01:06:30,330 That would explain why there's nobody else, because we're 1270 01:06:30,330 --> 01:06:30,960 the only ones. 1271 01:06:34,200 --> 01:06:34,740 We're here. 1272 01:06:34,740 --> 01:06:37,530 So it is possible for intelligent to form. 1273 01:06:37,530 --> 01:06:40,350 But it might be so improbable that we're the only ones 1274 01:06:40,350 --> 01:06:43,330 in the whole observed universe. 1275 01:06:43,330 --> 01:06:47,200 Maybe you only get one intelligent life form 1276 01:06:47,200 --> 01:06:49,750 in the volume that's equivalent to the volume 1277 01:06:49,750 --> 01:06:50,910 of our observed universe. 1278 01:06:50,910 --> 01:06:52,980 Maybe that's what happens. 1279 01:06:52,980 --> 01:06:54,430 Yes? 1280 01:06:54,430 --> 01:06:56,750 Did you have a question? 1281 01:06:56,750 --> 01:06:57,700 AUDIENCE: [INAUDIBLE]. 1282 01:07:01,560 --> 01:07:03,060 NICHOLAS DIBELLA: Yeah, so there are 1283 01:07:03,060 --> 01:07:05,940 a number of other explanations. 1284 01:07:05,940 --> 01:07:08,850 That might be part of the great filter. 1285 01:07:08,850 --> 01:07:11,520 The civilizations, they would have 1286 01:07:11,520 --> 01:07:14,760 to survive a whole bunch of possible natural catastrophes. 1287 01:07:14,760 --> 01:07:19,847 Maybe meteors were common. 1288 01:07:19,847 --> 01:07:21,180 They would have to survive that. 1289 01:07:21,180 --> 01:07:23,730 Or they would have to have to keep developing 1290 01:07:23,730 --> 01:07:27,230 so that a meteor hasn't struck yet, 1291 01:07:27,230 --> 01:07:31,426 or a supervolcano hasn't erupted yet. 1292 01:07:31,426 --> 01:07:33,390 Or probably the most interesting case 1293 01:07:33,390 --> 01:07:36,340 of a kind of a natural catastrophe 1294 01:07:36,340 --> 01:07:40,470 is what's known as gamma ray bursts. 1295 01:07:40,470 --> 01:07:43,410 So these are the most energetic things 1296 01:07:43,410 --> 01:07:44,920 that we see in the entire universe. 1297 01:07:44,920 --> 01:07:46,750 They're called gamma ray bursts. 1298 01:07:46,750 --> 01:07:50,790 They're these burst of energy, primarily gamma rays. 1299 01:07:50,790 --> 01:07:52,950 And they only last for a short amount of time. 1300 01:07:52,950 --> 01:07:54,360 But they're so energetic. 1301 01:07:54,360 --> 01:07:57,360 The amount of energy that a gamma ray burst puts out 1302 01:07:57,360 --> 01:08:00,180 in just a few seconds is equal to the amount of energy 1303 01:08:00,180 --> 01:08:03,270 that the sun produces in its entire lifetime, billions 1304 01:08:03,270 --> 01:08:04,140 of years. 1305 01:08:04,140 --> 01:08:06,720 That's how energetic these things are. 1306 01:08:06,720 --> 01:08:09,660 Now, we've only seen gamma ray bursts outside of our galaxy. 1307 01:08:09,660 --> 01:08:11,610 We've only seem them very far away. 1308 01:08:11,610 --> 01:08:15,570 But it's quite possible that any day, a gamma ray burst 1309 01:08:15,570 --> 01:08:17,470 might happen inside our galaxy. 1310 01:08:17,470 --> 01:08:20,670 We don't really know a whole lot about these things. 1311 01:08:20,670 --> 01:08:22,034 It could happen tomorrow. 1312 01:08:22,034 --> 01:08:26,020 A gamma ray burst happens, and completely annihilates us. 1313 01:08:26,020 --> 01:08:28,590 So it could be that intelligent life 1314 01:08:28,590 --> 01:08:30,750 started to form in a number of cases, 1315 01:08:30,750 --> 01:08:35,140 but got quickly killed away by some kind 1316 01:08:35,140 --> 01:08:36,327 of a natural catastrophe. 1317 01:08:36,327 --> 01:08:37,410 That's certainly possible. 1318 01:08:40,569 --> 01:08:44,790 It's also possible that once intelligence 1319 01:08:44,790 --> 01:08:49,080 reaches a certain point, then the civilization inevitably 1320 01:08:49,080 --> 01:08:51,180 destroys itself. 1321 01:08:51,180 --> 01:08:52,859 That's a very real possibility. 1322 01:08:52,859 --> 01:08:55,560 I mean, certainly-- 1323 01:08:55,560 --> 01:08:57,720 I mean, we only have one data point to look at, 1324 01:08:57,720 --> 01:09:00,115 our own civilization. 1325 01:09:02,729 --> 01:09:05,220 And we have the potential to destroy ourselves 1326 01:09:05,220 --> 01:09:06,630 many times over. 1327 01:09:06,630 --> 01:09:08,760 I mean, we have the toys. 1328 01:09:08,760 --> 01:09:11,970 We have the weapons to destroy ourselves many times. 1329 01:09:11,970 --> 01:09:16,979 And maybe most or all sufficiently advanced 1330 01:09:16,979 --> 01:09:19,229 civilizations inevitably destroy themselves 1331 01:09:19,229 --> 01:09:24,260 before they can communicate with other civilizations, 1332 01:09:24,260 --> 01:09:27,560 or before they can try to travel to see us, 1333 01:09:27,560 --> 01:09:31,359 to see other civilizations. 1334 01:09:31,359 --> 01:09:35,790 So this might be another step in the great filter. 1335 01:09:35,790 --> 01:09:38,430 It could be that the main part of the great filter 1336 01:09:38,430 --> 01:09:41,520 is actually after intelligent life forms. 1337 01:09:41,520 --> 01:09:45,000 It could be that most intelligent life destroys 1338 01:09:45,000 --> 01:09:48,010 itself after discovering weapons, for example. 1339 01:09:48,010 --> 01:09:50,580 Or they destroy their ecosystem, or something like that. 1340 01:09:53,100 --> 01:09:59,010 So I was actually reading an interesting paper recently 1341 01:09:59,010 --> 01:10:02,600 by a philosopher named Nick Bostrom, where 1342 01:10:02,600 --> 01:10:08,530 he hopes that our search for life on Mars, 1343 01:10:08,530 --> 01:10:13,800 for example, finds nothing, because the more-- 1344 01:10:13,800 --> 01:10:15,900 so suppose we found life on Mars. 1345 01:10:15,900 --> 01:10:18,850 Or maybe we found relics of life from the past. 1346 01:10:18,850 --> 01:10:25,290 Maybe we found simple bacterial type of life on Mars. 1347 01:10:25,290 --> 01:10:27,540 That would seem to indicate that it's 1348 01:10:27,540 --> 01:10:30,234 pretty easy for simple life forms to emerge. 1349 01:10:30,234 --> 01:10:31,650 And so that would seem to indicate 1350 01:10:31,650 --> 01:10:33,899 that the great filter doesn't happen at the beginning, 1351 01:10:33,899 --> 01:10:36,230 but it would happen after life is formed already. 1352 01:10:36,230 --> 01:10:38,007 So maybe it's multi-cellular. 1353 01:10:38,007 --> 01:10:39,840 Maybe that's the stage that's very unlikely. 1354 01:10:39,840 --> 01:10:42,675 Maybe that's the main part of the great filter. 1355 01:10:42,675 --> 01:10:46,200 But suppose we found bones on Mars. 1356 01:10:46,200 --> 01:10:48,540 Suppose we found bones that looked like human bones, 1357 01:10:48,540 --> 01:10:50,030 or human type bones. 1358 01:10:50,030 --> 01:10:53,640 That would be awful new for the future of humanity, 1359 01:10:53,640 --> 01:10:55,950 because that would seem to indicate that it's not 1360 01:10:55,950 --> 01:10:58,257 very hard to get to the stage where 1361 01:10:58,257 --> 01:10:59,340 you have intelligent life. 1362 01:11:03,270 --> 01:11:07,800 And if you find bones on Mars, you don't find actual living 1363 01:11:07,800 --> 01:11:11,050 life, you find dead life, then that 1364 01:11:11,050 --> 01:11:14,730 would seem to be evidence that once intelligent life forms, 1365 01:11:14,730 --> 01:11:17,560 then it gets destroyed for one reason or another. 1366 01:11:17,560 --> 01:11:21,420 So that would seem to say a little bit about our future. 1367 01:11:21,420 --> 01:11:25,710 And so it would be very bad news for us. 1368 01:11:25,710 --> 01:11:28,460 The article goes on to say, if we found bones on Mars, 1369 01:11:28,460 --> 01:11:29,960 or even if we found any kind of life 1370 01:11:29,960 --> 01:11:36,080 on Mars, the more complex life we find on Mars or anywhere 1371 01:11:36,080 --> 01:11:45,800 else, would probably lead to a lower chance of survival for us 1372 01:11:45,800 --> 01:11:46,880 in the future. 1373 01:11:46,880 --> 01:11:47,720 And that would be bad news, because we'd 1374 01:11:47,720 --> 01:11:48,928 like to live for a long time. 1375 01:11:58,880 --> 01:12:04,290 So I guess the main lesson to take away from all of this, 1376 01:12:04,290 --> 01:12:07,550 is that the Fermi paradox, it's a real problem. 1377 01:12:07,550 --> 01:12:09,560 And it's a hard one. 1378 01:12:09,560 --> 01:12:12,510 I feel the question of whether we're alone in the universe 1379 01:12:12,510 --> 01:12:14,380 is an extremely important one. 1380 01:12:14,380 --> 01:12:18,120 And it's one that we've probably all wondered in our lives. 1381 01:12:18,120 --> 01:12:19,770 We certainly don't know the answer now. 1382 01:12:19,770 --> 01:12:22,850 And we may well never know the answer. 1383 01:12:22,850 --> 01:12:26,262 But searching for the answer is certainly a fun journey. 1384 01:12:26,262 --> 01:12:27,220 And I'll end with that. 1385 01:12:27,220 --> 01:12:29,370 I'll see you next week.