1 00:00:00,520 --> 00:00:04,440 Speaker 1: What exactly does figuring out if aliens exist have to 2 00:00:04,519 --> 00:00:07,680 Speaker 1: do with the end of the world. Well, it turns 3 00:00:07,720 --> 00:00:10,360 Speaker 1: out that the odd emptiness that we find in the 4 00:00:10,440 --> 00:00:13,840 Speaker 1: universe can give us clues about what may have gone 5 00:00:13,840 --> 00:00:17,440 Speaker 1: on or didn't go on before we humans came along. 6 00:00:18,440 --> 00:00:22,480 Speaker 1: Did something bad happen? And if so, might it happen 7 00:00:22,520 --> 00:00:26,279 Speaker 1: to us two? Looking around for signs of whether we're 8 00:00:26,320 --> 00:00:29,760 Speaker 1: the only intelligent life to have ever evolved can help 9 00:00:29,800 --> 00:00:33,720 Speaker 1: answer those questions. And when you look at it, the 10 00:00:33,840 --> 00:00:38,080 Speaker 1: universe does seem amazingly large for Earth to be the 11 00:00:38,200 --> 00:00:42,199 Speaker 1: only planet with life on it. Consider it like this. 12 00:00:43,440 --> 00:00:47,040 Speaker 1: Let's say that you're a photon, a tiny packet of light, 13 00:00:47,680 --> 00:00:50,400 Speaker 1: and one day you had the wherewithal this set out 14 00:00:50,440 --> 00:00:54,320 Speaker 1: to travel across the universe. You would find that, perhaps 15 00:00:54,320 --> 00:00:57,120 Speaker 1: to your great surprise, such a trip would take you 16 00:00:57,200 --> 00:01:02,640 Speaker 1: around fifty billion years. Yes, you, light, which can travel 17 00:01:02,680 --> 00:01:05,640 Speaker 1: at the speed of light, would take fifty billion years 18 00:01:05,640 --> 00:01:07,960 Speaker 1: to cross from one side of the universe to the other. 19 00:01:08,680 --> 00:01:10,720 Speaker 1: At least that's how long it would appear to take 20 00:01:10,760 --> 00:01:14,520 Speaker 1: you to as humans. And this is just the observable universe. 21 00:01:14,720 --> 00:01:16,760 Speaker 1: The amount of the universe that light like you has 22 00:01:16,760 --> 00:01:19,960 Speaker 1: had time to travel across since the Big Bang. Within 23 00:01:20,000 --> 00:01:23,399 Speaker 1: that vast space, there are anywhere from one billion to 24 00:01:23,600 --> 00:01:27,760 Speaker 1: two trillion galaxies by our current causes, at least of 25 00:01:27,800 --> 00:01:30,040 Speaker 1: which our own Milky Way is on the larger side 26 00:01:30,080 --> 00:01:33,199 Speaker 1: of the spectrum. There are larger but there are also 27 00:01:33,240 --> 00:01:36,600 Speaker 1: a lot of smaller ones too. Within these billions or 28 00:01:36,640 --> 00:01:41,160 Speaker 1: trillions of galaxies are billions and billions and billions of stars, 29 00:01:41,319 --> 00:01:45,920 Speaker 1: and probably exponentially more planets. The total number of planets 30 00:01:45,920 --> 00:01:48,880 Speaker 1: and stars in our universe, the total number of places 31 00:01:48,880 --> 00:01:53,480 Speaker 1: for life to exist, is mind bogglingly large. And so 32 00:01:53,600 --> 00:01:57,040 Speaker 1: you packet of light or wavelength, depending on your mood, 33 00:01:57,600 --> 00:02:00,320 Speaker 1: might think to yourself, as you traveled across the verse 34 00:02:00,360 --> 00:02:03,040 Speaker 1: and saw that the Earth is the only planet that 35 00:02:03,240 --> 00:02:05,920 Speaker 1: is home to intelligent life. Out of the attend to 36 00:02:05,960 --> 00:02:08,600 Speaker 1: the who knows what power planets that could host life, 37 00:02:09,360 --> 00:02:12,360 Speaker 1: You might think to yourself, in your little photon voice, 38 00:02:13,080 --> 00:02:18,320 Speaker 1: what waste are we alone in the universe? And if 39 00:02:18,360 --> 00:02:21,400 Speaker 1: we are alone, why? These are the questions at the 40 00:02:21,400 --> 00:02:24,360 Speaker 1: heart of the Fermi paradox, and they continue to nag 41 00:02:24,400 --> 00:02:27,480 Speaker 1: at us. The answer is plainly obvious if you look 42 00:02:27,520 --> 00:02:30,160 Speaker 1: at it, but it depends on how you look at it. 43 00:02:30,840 --> 00:02:33,639 Speaker 1: With the Fermi paradox, the same thing can look very 44 00:02:33,639 --> 00:02:36,480 Speaker 1: different to any two people. And it's not just the 45 00:02:36,520 --> 00:02:41,400 Speaker 1: paradox itself. Even the evidence is equally ambiguous. It's all 46 00:02:41,440 --> 00:02:45,000 Speaker 1: like one big contradem words that have two meanings that 47 00:02:45,040 --> 00:02:48,440 Speaker 1: are the opposite of one another, like how weather can 48 00:02:48,480 --> 00:02:51,880 Speaker 1: mean both to wear away and to withstand something. The 49 00:02:51,919 --> 00:02:54,560 Speaker 1: size of our empty universe can mean that we are 50 00:02:54,600 --> 00:02:59,240 Speaker 1: both alone or one of many. Another example of this 51 00:02:59,400 --> 00:03:03,680 Speaker 1: ambiguity is the very presence of life on Earth, something 52 00:03:03,680 --> 00:03:05,600 Speaker 1: that people who believe that we're not alone in the 53 00:03:05,680 --> 00:03:08,440 Speaker 1: universe point to. His evidence is that life here on 54 00:03:08,480 --> 00:03:11,239 Speaker 1: Earth seems to have emerged the first chance that it had. 55 00:03:12,280 --> 00:03:15,919 Speaker 1: The famous astronomer and science writer Carl Sagan was one 56 00:03:15,960 --> 00:03:18,720 Speaker 1: of those people. He was an optimist when it came 57 00:03:18,760 --> 00:03:22,560 Speaker 1: to the family paradox. He believed that life was out there, 58 00:03:22,800 --> 00:03:26,560 Speaker 1: we just hadn't found it yet. Sagan pointed to evidence 59 00:03:26,560 --> 00:03:29,280 Speaker 1: from the fossil record that here on Earth life began 60 00:03:29,320 --> 00:03:32,880 Speaker 1: as early as five hundred million years after the Earth form. 61 00:03:32,960 --> 00:03:35,840 Speaker 1: It was almost like it was waiting to emerge, and 62 00:03:35,920 --> 00:03:38,960 Speaker 1: since it emerged quickly here on Earth, it stands to 63 00:03:39,000 --> 00:03:42,040 Speaker 1: reason that life should emerge wherever it gets the chance, 64 00:03:42,200 --> 00:03:45,880 Speaker 1: anywhere in our universe. When you take into account the 65 00:03:45,920 --> 00:03:48,480 Speaker 1: idea that there are perhaps three hundred billion stars in 66 00:03:48,520 --> 00:03:51,960 Speaker 1: the Milky Way alone, even if some small fraction of 67 00:03:52,000 --> 00:03:55,280 Speaker 1: those have habitable planets that could host life, then we 68 00:03:55,320 --> 00:03:58,680 Speaker 1: should expect to encounter it sometime soon as we spread 69 00:03:58,680 --> 00:04:02,600 Speaker 1: out to explore the country side around planet Earth. But 70 00:04:02,640 --> 00:04:04,960 Speaker 1: there's a problem with basing our view of the rest 71 00:04:05,040 --> 00:04:08,600 Speaker 1: of the universe on our own existence. The idea that 72 00:04:08,640 --> 00:04:11,560 Speaker 1: we can gain insight into our universe from our existence 73 00:04:11,640 --> 00:04:15,120 Speaker 1: is called the anthropic principle, and it's vulnerable to a 74 00:04:15,200 --> 00:04:20,080 Speaker 1: logical fallacy called selection bias. Being the only intelligent life 75 00:04:20,080 --> 00:04:22,840 Speaker 1: in the universe, we're the only data point in our 76 00:04:22,920 --> 00:04:26,360 Speaker 1: data set, and so we tend to skew the results 77 00:04:26,360 --> 00:04:29,440 Speaker 1: a little bit. It's hard to resist the temptation of 78 00:04:29,520 --> 00:04:33,320 Speaker 1: cherry picking the data when there's only one cherry. Yes, 79 00:04:33,360 --> 00:04:37,159 Speaker 1: of course, life can arise. Our very existence proves that fact. 80 00:04:37,600 --> 00:04:40,200 Speaker 1: But what it does not prove is that the emergence 81 00:04:40,200 --> 00:04:44,680 Speaker 1: of intelligent life or any life, really is easy or inevitable. 82 00:04:45,440 --> 00:04:48,839 Speaker 1: What if, instead, life emerging in our universe is really, 83 00:04:49,320 --> 00:04:55,400 Speaker 1: really really hard. Perhaps the existence of living, breathing, intelligent 84 00:04:55,480 --> 00:04:58,120 Speaker 1: things here on Earth doesn't show the emergence of life 85 00:04:58,160 --> 00:05:01,600 Speaker 1: is inevitable. Perhaps as shows that it was the singularly 86 00:05:01,680 --> 00:05:05,320 Speaker 1: most unlikely event in the history of our entire universe. 87 00:05:11,400 --> 00:05:13,720 Speaker 1: If you could crack open a strand of your DNA 88 00:05:14,200 --> 00:05:17,839 Speaker 1: and read the pairs of adenine, guanine, cite of scene 89 00:05:17,880 --> 00:05:21,159 Speaker 1: and dimin the ones and zeros of your genetic code, 90 00:05:21,800 --> 00:05:24,800 Speaker 1: you would find a history of life on Earth written 91 00:05:24,839 --> 00:05:28,480 Speaker 1: into it. Not only does your DNA contain the blueprints 92 00:05:28,520 --> 00:05:31,120 Speaker 1: for making a full version of you, but if you 93 00:05:31,160 --> 00:05:33,920 Speaker 1: look at it correctly, it also bears the marks of 94 00:05:33,920 --> 00:05:37,360 Speaker 1: those who have come before you. You'll find your parents genes, 95 00:05:37,440 --> 00:05:40,080 Speaker 1: of course, and their parents. But as you go further 96 00:05:40,160 --> 00:05:43,200 Speaker 1: back in time, you'll also find the contributions of all 97 00:05:43,200 --> 00:05:46,520 Speaker 1: of the animals in bacteria that ever reproduced along the 98 00:05:46,600 --> 00:05:49,800 Speaker 1: last several billion years to form a connected chain of 99 00:05:49,839 --> 00:05:54,120 Speaker 1: life that eventually led to you. But you'll find that 100 00:05:54,160 --> 00:05:56,320 Speaker 1: you run into a wall the further you go back. 101 00:05:57,200 --> 00:05:59,520 Speaker 1: There's a point beyond which we can no longer read 102 00:05:59,560 --> 00:06:03,080 Speaker 1: the taves of our DNA. It ends right before we 103 00:06:03,120 --> 00:06:05,240 Speaker 1: get to the emergence of life here on Earth the 104 00:06:05,360 --> 00:06:08,760 Speaker 1: very beginning. That is to say, no one is sure 105 00:06:09,279 --> 00:06:14,680 Speaker 1: how life began as it stands now, the general consensus 106 00:06:14,680 --> 00:06:19,200 Speaker 1: among sciences the concept of a biogenesis, that life emerged 107 00:06:19,240 --> 00:06:23,400 Speaker 1: from nothing nothing living anyway, let's go back to the 108 00:06:23,480 --> 00:06:27,680 Speaker 1: early Earth. About five million years after it formed, the 109 00:06:27,720 --> 00:06:31,040 Speaker 1: surfaces just begun to cool enough that solid clay ground 110 00:06:31,040 --> 00:06:33,440 Speaker 1: has begun to form, and with the cooling off, the 111 00:06:33,560 --> 00:06:37,360 Speaker 1: muggy atmosphere cooled as well, condensing in the rain that 112 00:06:37,480 --> 00:06:40,200 Speaker 1: began to collect in pools which would become the peatree 113 00:06:40,279 --> 00:06:44,120 Speaker 1: dishes where life took its first steps. But to get 114 00:06:44,200 --> 00:06:48,680 Speaker 1: from here to life, something extremely unlikely had to happen. 115 00:06:49,600 --> 00:06:54,520 Speaker 1: Plain old, lifeless molecules had to spontaneously arrange themselves into 116 00:06:54,560 --> 00:06:58,920 Speaker 1: new forms that became the building blocks of life. At 117 00:06:58,960 --> 00:07:01,560 Speaker 1: this point, there was nothing but raw materials on Earth, 118 00:07:01,880 --> 00:07:04,560 Speaker 1: and we have to get from here to living organisms. 119 00:07:05,400 --> 00:07:08,320 Speaker 1: That means that not only do you have a functioning organism, 120 00:07:08,400 --> 00:07:10,960 Speaker 1: it has to carry with it the encoded instructions to 121 00:07:11,000 --> 00:07:13,440 Speaker 1: make a copy of itself, and some way to read 122 00:07:13,440 --> 00:07:16,840 Speaker 1: those instructions and actually make that copy. It's like the 123 00:07:16,920 --> 00:07:20,080 Speaker 1: idea of putting some plastic pellets and metal shavings into 124 00:07:20,080 --> 00:07:23,360 Speaker 1: a bucket and expecting an autonomous three D printer to 125 00:07:23,440 --> 00:07:27,480 Speaker 1: form from it, or more to the point, it would 126 00:07:27,520 --> 00:07:31,200 Speaker 1: be like the idea of rotting meat growing maggots. For 127 00:07:31,240 --> 00:07:34,040 Speaker 1: a long time, humans thought that this kind of thing 128 00:07:34,240 --> 00:07:38,720 Speaker 1: spontaneous generation, was how some life arose. Prior to when 129 00:07:38,760 --> 00:07:41,960 Speaker 1: science took up the mantle of explaining our universe, people 130 00:07:42,000 --> 00:07:45,200 Speaker 1: relied on their everyday observations to explain occurrence is like 131 00:07:45,240 --> 00:07:48,600 Speaker 1: maggots growing on rotting meat, seeming to appear out of nowhere. 132 00:07:49,440 --> 00:07:52,000 Speaker 1: It seemed just as likely as anything that maggots could 133 00:07:52,040 --> 00:07:56,559 Speaker 1: spontaneously generate, or baby mice from grain, which was another 134 00:07:56,600 --> 00:08:00,200 Speaker 1: common folk belief. But eventually scientists figured out a way 135 00:08:00,200 --> 00:08:03,560 Speaker 1: to disprove this idea, which really gained support when we 136 00:08:03,600 --> 00:08:07,480 Speaker 1: realized that tiny, unseen life lived around us everywhere and 137 00:08:07,480 --> 00:08:08,960 Speaker 1: that it had a hand in a lot of the 138 00:08:09,040 --> 00:08:13,120 Speaker 1: things that we saw. Germ theory was developed and the 139 00:08:13,200 --> 00:08:17,920 Speaker 1: concept of spontaneous generation was abandoned. That is until the 140 00:08:18,000 --> 00:08:22,040 Speaker 1: nineteen fifties, when researchers started working hard on figuring out 141 00:08:22,160 --> 00:08:26,200 Speaker 1: how life on Earth might have come about. Spontaneous generation 142 00:08:26,520 --> 00:08:32,400 Speaker 1: made an unexpected comeback. A biogenesis holds that quadrillions upon 143 00:08:32,520 --> 00:08:36,480 Speaker 1: quintillions of simple molecules present in Earth's early atmosphere and 144 00:08:36,559 --> 00:08:40,880 Speaker 1: oceans randomly configured themselves into a mind bending number of 145 00:08:40,920 --> 00:08:45,600 Speaker 1: different combinations. Some of these abominably large number of combinations 146 00:08:45,600 --> 00:08:49,600 Speaker 1: happen to create useful complex molecules like amino acids, which 147 00:08:49,600 --> 00:08:53,640 Speaker 1: are the precursors for proteins. Now, it's one thing to 148 00:08:53,720 --> 00:08:58,320 Speaker 1: form simple molecules to randomly combined to form more complex molecules, 149 00:08:58,360 --> 00:09:01,280 Speaker 1: but there is still the issue of replication. Ship If 150 00:09:01,320 --> 00:09:04,120 Speaker 1: those molecules don't make a younger copy of themselves, that 151 00:09:04,240 --> 00:09:07,880 Speaker 1: innovative chemical chain is broken and the new molecule loses 152 00:09:07,920 --> 00:09:10,160 Speaker 1: the chance to continue to evolve in a new and 153 00:09:10,240 --> 00:09:13,840 Speaker 1: even more complex things. And this is the point where 154 00:09:13,840 --> 00:09:17,760 Speaker 1: science is currently stuck. Somehow, they say, some of those 155 00:09:17,800 --> 00:09:21,760 Speaker 1: molecules managed to form a stable string of nuclear times, 156 00:09:21,800 --> 00:09:25,760 Speaker 1: probably r N, a ribonucleic acid which is capable of 157 00:09:25,760 --> 00:09:30,040 Speaker 1: doing two very important things. It can encode information in 158 00:09:30,080 --> 00:09:33,319 Speaker 1: its nuclear tide chain, and it can also transcribe those 159 00:09:33,360 --> 00:09:36,880 Speaker 1: nuclear tides to produce proteins. And once you have proteins, 160 00:09:37,200 --> 00:09:39,600 Speaker 1: you can do all sorts of things that supports life. 161 00:09:40,800 --> 00:09:45,320 Speaker 1: Back in two organic chemists Stanley Miller and Herald Urray 162 00:09:45,640 --> 00:09:48,199 Speaker 1: saw it to show that this was possible by recreating 163 00:09:48,200 --> 00:09:51,680 Speaker 1: the conditions of earlier Earth. In a flask. They simulated 164 00:09:51,720 --> 00:09:54,400 Speaker 1: a primitive ocean and built an atmosphere out of the 165 00:09:54,480 --> 00:09:57,000 Speaker 1: gases thought back in the fifties to have been present 166 00:09:57,000 --> 00:10:00,040 Speaker 1: on Earth soon after it formed. They mimicked why in 167 00:10:00,280 --> 00:10:03,800 Speaker 1: storms with the flickering electrical current, and when Miller inspected 168 00:10:03,800 --> 00:10:07,520 Speaker 1: the broth that resulted, he found that nineteen amino acids 169 00:10:07,520 --> 00:10:12,640 Speaker 1: and amans, the precursors to proteins, had assembled spontaneously. It 170 00:10:12,679 --> 00:10:15,520 Speaker 1: seems that Miller had shown that when the conditions were right, 171 00:10:15,880 --> 00:10:20,480 Speaker 1: the foundations for life would arise. But lately the idea 172 00:10:20,559 --> 00:10:25,680 Speaker 1: that a biogenesis just happened randomly is falling out of favor. Instead, 173 00:10:26,000 --> 00:10:28,640 Speaker 1: some scientists have begun to suspect that there is some 174 00:10:28,760 --> 00:10:32,400 Speaker 1: set of organizing principles that serves as a driving force 175 00:10:32,520 --> 00:10:35,920 Speaker 1: for life to emerge. Just like how gravity will draw 176 00:10:35,960 --> 00:10:39,520 Speaker 1: a ball downhill, or how magnets will always repel or 177 00:10:39,559 --> 00:10:42,640 Speaker 1: attract one another when they're close together, there is some 178 00:10:42,760 --> 00:10:46,839 Speaker 1: fundamental governing force of nature that causes life to assemble 179 00:10:47,120 --> 00:10:51,120 Speaker 1: along predictable lines. We just haven't figured out what that 180 00:10:51,200 --> 00:10:54,800 Speaker 1: force or those lines are yet. This is a pretty 181 00:10:54,840 --> 00:10:57,599 Speaker 1: surprising idea if you think of it. One of the 182 00:10:57,679 --> 00:11:00,720 Speaker 1: laws of the universe, the second law of therm mom dynamics, 183 00:11:01,120 --> 00:11:05,840 Speaker 1: is that things tend towards disorder, not order. The idea that, 184 00:11:05,840 --> 00:11:09,120 Speaker 1: when presented with the right conditions, dead molecules in the 185 00:11:09,240 --> 00:11:13,120 Speaker 1: universe will organize themselves into something living and breathing runs 186 00:11:13,320 --> 00:11:16,959 Speaker 1: totally counter to that, and this new view also includes 187 00:11:17,000 --> 00:11:21,360 Speaker 1: evolutionary biology as one stretch of these organizing principles of life. 188 00:11:22,280 --> 00:11:26,280 Speaker 1: So the idea is that molecules arrange themselves into self replicating, 189 00:11:26,520 --> 00:11:31,480 Speaker 1: metabolizing parts that form increasingly complex beings that eventually include 190 00:11:31,480 --> 00:11:35,079 Speaker 1: you and me, which makes you wonder what the end 191 00:11:35,120 --> 00:11:55,240 Speaker 1: point is. To some people, the idea that life arose 192 00:11:55,320 --> 00:11:59,160 Speaker 1: from simple dead molecules that just happened to randomly assemble 193 00:11:59,240 --> 00:12:03,560 Speaker 1: themselves in the living things is just too unlikely to accept, 194 00:12:04,520 --> 00:12:07,160 Speaker 1: And even if we do accept that this is precisely 195 00:12:07,240 --> 00:12:10,120 Speaker 1: how life arose on Earth, the idea that it could 196 00:12:10,160 --> 00:12:14,920 Speaker 1: ever happen again anywhere else is too improbable. That virtually 197 00:12:15,000 --> 00:12:19,360 Speaker 1: proves that we humans are alone in the universe. One 198 00:12:19,400 --> 00:12:22,960 Speaker 1: issue people raise is time. They say that Earth just 199 00:12:23,040 --> 00:12:25,600 Speaker 1: simply hasn't been around long enough for all of that 200 00:12:26,000 --> 00:12:30,040 Speaker 1: random chemical trial and error to have taken place. The 201 00:12:30,120 --> 00:12:34,840 Speaker 1: idea that life organizes along some unknown universal principles definitely 202 00:12:34,840 --> 00:12:38,079 Speaker 1: addresses that idea of time, and so does pant spermia. 203 00:12:38,840 --> 00:12:42,440 Speaker 1: Pant Spermia is a concept from astrobiology, and it says 204 00:12:42,520 --> 00:12:45,120 Speaker 1: that the seeds of life are all over the universe 205 00:12:45,160 --> 00:12:48,719 Speaker 1: in abundance everywhere. They can be found on board asteroids 206 00:12:48,720 --> 00:12:51,920 Speaker 1: and other celestial objects, and that these seeds of life 207 00:12:51,920 --> 00:12:56,760 Speaker 1: are constantly bombarding planets all over the universe. If the 208 00:12:56,800 --> 00:12:59,520 Speaker 1: conditions on the planet happen to be right, well, then 209 00:12:59,559 --> 00:13:02,280 Speaker 1: those sea needs of life will germinate and grow into 210 00:13:02,480 --> 00:13:06,920 Speaker 1: something new and living. This certainly addresses the issue of time. 211 00:13:07,600 --> 00:13:10,280 Speaker 1: Life could have evolved elsewhere in the universe, which is 212 00:13:10,320 --> 00:13:13,080 Speaker 1: billions of years older than Earth, and then spread to 213 00:13:13,120 --> 00:13:17,520 Speaker 1: our planet aboard an asteroid. We've recently found that some 214 00:13:17,600 --> 00:13:21,000 Speaker 1: chemical precursors to life can be found on celestial objects 215 00:13:21,000 --> 00:13:23,920 Speaker 1: like asteroids, and that they're able to survive re entry 216 00:13:24,000 --> 00:13:26,960 Speaker 1: into an atmosphere, which can get pretty hot. This is 217 00:13:27,000 --> 00:13:30,080 Speaker 1: important because it's widely accepted that an atmosphere is a 218 00:13:30,120 --> 00:13:34,400 Speaker 1: precondition for life to emerge. If you take pants bermia, 219 00:13:34,520 --> 00:13:36,800 Speaker 1: and you take the recent view that life follows some 220 00:13:36,960 --> 00:13:40,800 Speaker 1: organizing principles as immutable as the laws of physics, then 221 00:13:40,840 --> 00:13:43,920 Speaker 1: you arrive at a conclusion that Earth is just another 222 00:13:43,960 --> 00:13:46,640 Speaker 1: place that happened to have the right conditions when a 223 00:13:46,760 --> 00:13:50,160 Speaker 1: rock bearing the precursors to life landed around four billion 224 00:13:50,240 --> 00:13:54,520 Speaker 1: years ago. In this view, then of course life is 225 00:13:54,559 --> 00:13:58,400 Speaker 1: abundant in the universe. But then we find ourselves right 226 00:13:58,440 --> 00:14:03,160 Speaker 1: back to where we started. Where is everybody? Perhaps the 227 00:14:03,200 --> 00:14:06,400 Speaker 1: best answer to that comes not from an astrobiologist or 228 00:14:06,440 --> 00:14:11,160 Speaker 1: an astronomer, but from an economist named Robin Hansen, who 229 00:14:11,200 --> 00:14:15,520 Speaker 1: proposed that there must be something, some incredibly difficult step 230 00:14:15,720 --> 00:14:18,480 Speaker 1: between the point where dead matter forms life and the 231 00:14:18,520 --> 00:14:23,240 Speaker 1: point where intelligent life becomes a galactically colonizing civilization that 232 00:14:23,360 --> 00:14:27,760 Speaker 1: no species has ever been able to overcome. He calls 233 00:14:27,760 --> 00:14:30,760 Speaker 1: it the great filter. Every piece of matter in the 234 00:14:30,800 --> 00:14:32,640 Speaker 1: universe is the sort of thing that could have started 235 00:14:32,640 --> 00:14:37,600 Speaker 1: that process, started life, and then advanced life, etcetera. But 236 00:14:38,760 --> 00:14:41,440 Speaker 1: so far nothing out there has done that. So the 237 00:14:41,480 --> 00:14:45,280 Speaker 1: great filter is whatever is in the way, whatever makes 238 00:14:45,280 --> 00:14:48,120 Speaker 1: it hard for any one piece of ordinary dead matter 239 00:14:48,280 --> 00:14:52,720 Speaker 1: to produce expanding, lasting life. There's surely a countless number 240 00:14:52,720 --> 00:14:55,200 Speaker 1: of steps along the path from dead matter to the 241 00:14:55,240 --> 00:14:59,360 Speaker 1: emergence of a galactically visible civilization. But the Great Filter 242 00:14:59,480 --> 00:15:02,800 Speaker 1: high Path says, supposes that a handful of them are really, 243 00:15:03,320 --> 00:15:06,640 Speaker 1: really hard, and that one of them in particular must 244 00:15:06,680 --> 00:15:10,000 Speaker 1: be so hard that is thus far prevented any life 245 00:15:10,200 --> 00:15:15,960 Speaker 1: from reaching galactic proportions. This is Oxford University philosopher Toby 246 00:15:16,160 --> 00:15:19,040 Speaker 1: ord if there were a hundred pieces you needed to 247 00:15:19,040 --> 00:15:21,640 Speaker 1: get into the right order in order to create something 248 00:15:21,800 --> 00:15:26,280 Speaker 1: that obeyed natural selection and and was it the basic 249 00:15:26,400 --> 00:15:31,080 Speaker 1: level needed to actually bootstrap up towards complex life, then 250 00:15:31,080 --> 00:15:34,600 Speaker 1: there are a hundred factorial ways you could arrange those pieces. 251 00:15:34,600 --> 00:15:37,200 Speaker 1: That's that's more than uh tends to the power of 252 00:15:37,240 --> 00:15:40,240 Speaker 1: a hundred different possibilities. And then it just turns out 253 00:15:40,320 --> 00:15:43,160 Speaker 1: you need an incredibly rare event to get there. The 254 00:15:43,200 --> 00:15:46,960 Speaker 1: Great Filter offers two possible solutions to the question posed 255 00:15:46,960 --> 00:15:52,520 Speaker 1: by the Fermi paradox. Whereas everybody everybody never existed, or 256 00:15:52,600 --> 00:15:57,040 Speaker 1: everybody is dead, if the Great Filter is in our past, 257 00:15:57,440 --> 00:16:00,040 Speaker 1: it says pretty strongly that we are the first and 258 00:16:00,240 --> 00:16:04,880 Speaker 1: only intelligent life that exists in the universe. If that's true, 259 00:16:05,360 --> 00:16:09,000 Speaker 1: then by the Great Filter, there is something, some step, 260 00:16:09,360 --> 00:16:12,320 Speaker 1: some right of passage you could call it, that has 261 00:16:12,360 --> 00:16:16,080 Speaker 1: prevented every other life from reaching the point that we're at. 262 00:16:17,360 --> 00:16:19,640 Speaker 1: And if that's the case, then we are the only 263 00:16:19,680 --> 00:16:23,880 Speaker 1: life to have made it through the Great Filter. That 264 00:16:23,960 --> 00:16:27,080 Speaker 1: means that we can be optimistic about our future. We 265 00:16:27,200 --> 00:16:29,480 Speaker 1: made it through that right of passage that has kept 266 00:16:29,520 --> 00:16:33,240 Speaker 1: every other attempt at life from evolving. It means our big, 267 00:16:33,360 --> 00:16:37,000 Speaker 1: vast universe isn't wasted on us. It's just waiting there 268 00:16:37,040 --> 00:16:40,400 Speaker 1: for us to use it, and guilt free too. Since 269 00:16:40,560 --> 00:16:43,040 Speaker 1: no one else is around to use it, we have 270 00:16:43,120 --> 00:16:46,600 Speaker 1: a responsibility to put it to use. You could even say. 271 00:16:47,360 --> 00:16:51,160 Speaker 1: But there's another possibility to the Great Filter too. It 272 00:16:51,200 --> 00:16:56,320 Speaker 1: may also lie just ahead in our future. Maybe intelligent 273 00:16:56,360 --> 00:16:58,920 Speaker 1: life is a dime a dozen in the universe. But 274 00:16:59,000 --> 00:17:02,800 Speaker 1: the reason we don't see other civilizations is because they've 275 00:17:02,840 --> 00:17:07,280 Speaker 1: all died off. And if all of those intelligent civilizations 276 00:17:07,320 --> 00:17:11,679 Speaker 1: all died before any any of them could make it 277 00:17:11,720 --> 00:17:14,400 Speaker 1: off of their home planet and spread throughout the universe, 278 00:17:15,240 --> 00:17:17,840 Speaker 1: the Great Filter is a big red flag for us. 279 00:17:19,440 --> 00:17:21,399 Speaker 1: It tells us that we should expect to meet the 280 00:17:21,440 --> 00:17:25,920 Speaker 1: same fate that every other intelligent life has. The Great 281 00:17:25,960 --> 00:17:29,000 Speaker 1: Filter will spell the end of the world for us too. 282 00:17:30,600 --> 00:17:33,120 Speaker 1: To answer the question of whether we face imminent doom 283 00:17:33,240 --> 00:17:36,159 Speaker 1: or not, we have to look at the evolution of life, 284 00:17:36,800 --> 00:17:39,240 Speaker 1: and to do that we have no choice but to 285 00:17:39,320 --> 00:17:41,920 Speaker 1: turn to the one place where we know life evolved. 286 00:17:42,840 --> 00:17:45,320 Speaker 1: At the risk of falling victim to the selection bias, 287 00:17:45,800 --> 00:17:49,840 Speaker 1: we have to look to Earth for clues. We've already 288 00:17:49,840 --> 00:17:53,200 Speaker 1: talked about how utterly improbable the origin of life appears 289 00:17:53,200 --> 00:17:56,359 Speaker 1: to have been, but it's probably best to start looking 290 00:17:56,520 --> 00:18:02,560 Speaker 1: even further back than that. If life emerged on Earth, 291 00:18:02,640 --> 00:18:05,240 Speaker 1: that means that the conditions were right for life on Earth. 292 00:18:05,720 --> 00:18:08,520 Speaker 1: That's the one day to point we have ipso fact, though, 293 00:18:09,200 --> 00:18:11,440 Speaker 1: so the best way to find out what conditions life 294 00:18:11,440 --> 00:18:14,320 Speaker 1: requires is to look at the conditions of our planet. 295 00:18:15,040 --> 00:18:19,240 Speaker 1: And it turns out that Earth has some spectacularly peculiar 296 00:18:19,320 --> 00:18:24,040 Speaker 1: characteristics that make it ripe for life. So peculiar, in fact, 297 00:18:24,480 --> 00:18:27,000 Speaker 1: that a pair of researchers named Peter Ward and Donald 298 00:18:27,000 --> 00:18:29,680 Speaker 1: Brownlee rolled all of them up into what they call 299 00:18:29,720 --> 00:18:32,880 Speaker 1: the rare Earth hypothesis. It's just what it sounds like 300 00:18:33,280 --> 00:18:36,679 Speaker 1: when you add up all of its peculiarities. Earth is 301 00:18:36,720 --> 00:18:41,120 Speaker 1: not like other planets. First, Earth happened to form around 302 00:18:41,119 --> 00:18:43,640 Speaker 1: the right kind of star. Our son is a main 303 00:18:43,720 --> 00:18:47,040 Speaker 1: sequence star, which means it produces light and heat by 304 00:18:47,080 --> 00:18:51,560 Speaker 1: fusing hydrogen into helium. Main Sequence stars aren't rare. They 305 00:18:51,600 --> 00:18:54,680 Speaker 1: make up about nine of stars. But our Son also 306 00:18:54,720 --> 00:18:57,359 Speaker 1: happened to be of the right size too. It's not 307 00:18:57,480 --> 00:18:59,520 Speaker 1: so large that it will use up its fuel in 308 00:18:59,600 --> 00:19:03,000 Speaker 1: just a few billion years. That means that the Sun's slow, 309 00:19:03,080 --> 00:19:05,720 Speaker 1: steady burn would go on long enough to give life 310 00:19:05,760 --> 00:19:09,119 Speaker 1: time to develop. The Sun also isn't too small to 311 00:19:09,160 --> 00:19:12,960 Speaker 1: support life either. It is you could say, just right 312 00:19:13,040 --> 00:19:16,280 Speaker 1: for life. Our Sun has also placed in a really 313 00:19:16,320 --> 00:19:19,440 Speaker 1: great spot in our galaxy. We happen to be located 314 00:19:19,440 --> 00:19:21,679 Speaker 1: out in the country, in a bit of a backwater 315 00:19:21,760 --> 00:19:24,400 Speaker 1: when it comes to the Milky Way, about twenty eight 316 00:19:24,440 --> 00:19:27,480 Speaker 1: thousand light years from the galactic center, in a galaxy 317 00:19:27,520 --> 00:19:31,920 Speaker 1: that's one thousand light years across. For decades, study presumed 318 00:19:31,920 --> 00:19:33,880 Speaker 1: that the center of the galaxy would be the most 319 00:19:33,920 --> 00:19:37,000 Speaker 1: happening spot. That's where the most stars tend to be, 320 00:19:37,359 --> 00:19:42,080 Speaker 1: and more stars would be more potentially habitable planets. Civilizations 321 00:19:42,119 --> 00:19:44,440 Speaker 1: that arose in the center might even be in contact 322 00:19:44,480 --> 00:19:47,560 Speaker 1: with one another, forming something of a galactic urban area. 323 00:19:48,760 --> 00:19:51,679 Speaker 1: But recently it's become clear that the galactic center might 324 00:19:51,680 --> 00:19:55,200 Speaker 1: not be so flourishing. After all. There are more stars, sure, 325 00:19:55,800 --> 00:19:58,960 Speaker 1: but more stars also means that there are more collapsing stars, 326 00:19:59,359 --> 00:20:01,840 Speaker 1: which release bursts of energy that can burn away the 327 00:20:01,880 --> 00:20:05,680 Speaker 1: atmosphere of any planets in the vicinity, So the galactic 328 00:20:05,720 --> 00:20:08,680 Speaker 1: center might actually be less of a bustling urban area 329 00:20:09,000 --> 00:20:13,280 Speaker 1: and more like sterile and dead. Our Sun is pretty 330 00:20:13,320 --> 00:20:15,760 Speaker 1: far away from the galactic center, way out past the 331 00:20:15,800 --> 00:20:19,600 Speaker 1: suburbs where nothing much happens. In other words, that's good 332 00:20:19,720 --> 00:20:21,879 Speaker 1: for life on Earth because it means that it cuts 333 00:20:21,920 --> 00:20:25,280 Speaker 1: down on the number of sterilization events as life developed 334 00:20:25,280 --> 00:20:28,520 Speaker 1: over Earth's history, giving it a good chance of succeeding. 335 00:20:29,600 --> 00:20:32,119 Speaker 1: And Earth just so happens to be located within the 336 00:20:32,160 --> 00:20:35,040 Speaker 1: Sun's goldilocks zone that I mentioned in the last episode. 337 00:20:35,760 --> 00:20:37,680 Speaker 1: If it was a little nearer the Sun and about 338 00:20:37,680 --> 00:20:40,359 Speaker 1: one and a half million kilometers closer, it would be 339 00:20:40,400 --> 00:20:44,200 Speaker 1: too hot to support life, and much further away Earth 340 00:20:44,240 --> 00:20:47,320 Speaker 1: would be too cold for it. It also turns out 341 00:20:47,400 --> 00:20:50,320 Speaker 1: that where Earth is positioned in the Solar System is 342 00:20:50,400 --> 00:20:54,280 Speaker 1: hugely important to giving life a fighting chance. Earth is 343 00:20:54,320 --> 00:20:57,280 Speaker 1: the third rock from the Sun, with five others between 344 00:20:57,400 --> 00:20:59,920 Speaker 1: us and the rest of the galaxy. Six if the 345 00:21:00,080 --> 00:21:02,720 Speaker 1: math that suggests there's a planet nine out there turns 346 00:21:02,720 --> 00:21:05,600 Speaker 1: out to be correct, or if you continue to count 347 00:21:05,600 --> 00:21:09,240 Speaker 1: hapless Pluto, the Sun and the planets in our Solar 348 00:21:09,280 --> 00:21:12,760 Speaker 1: System formed from a massive cloud of cosmic dust, that 349 00:21:12,920 --> 00:21:15,080 Speaker 1: same stuff that might have blown up so many alien 350 00:21:15,119 --> 00:21:18,960 Speaker 1: pilots traveling between the stars. We still aren't quite sure 351 00:21:18,960 --> 00:21:23,320 Speaker 1: exactly how the planets formed. One model astoundingly suggested that 352 00:21:23,320 --> 00:21:25,919 Speaker 1: they could have formed in as little as a thousand years, 353 00:21:26,720 --> 00:21:28,919 Speaker 1: but the birth of the Solar System was likely a 354 00:21:28,920 --> 00:21:31,280 Speaker 1: free for all grab of the elements that make up 355 00:21:31,320 --> 00:21:36,240 Speaker 1: the planets today. Initially, astronomers presumed that the planets formed 356 00:21:36,280 --> 00:21:39,480 Speaker 1: in their current arrangement, but lately it's become clear that 357 00:21:39,480 --> 00:21:42,639 Speaker 1: that probably wasn't the case. The planets may have actually 358 00:21:42,680 --> 00:21:45,960 Speaker 1: moved around and migrated from one spot to another in 359 00:21:46,000 --> 00:21:49,040 Speaker 1: the early life of the Solar System before settling into 360 00:21:49,080 --> 00:21:52,800 Speaker 1: the arrangement that we see them in today. If that's correct, 361 00:21:53,119 --> 00:21:56,520 Speaker 1: then we were astoundingly lucky that Jupiter ended up where 362 00:21:56,520 --> 00:22:04,880 Speaker 1: it didn't. Jupiter is a gas giant made up largely 363 00:22:04,920 --> 00:22:07,520 Speaker 1: of hydrogen and helium with a metal and ice core. 364 00:22:07,920 --> 00:22:10,520 Speaker 1: It's like a Sun that never started burning because it 365 00:22:10,600 --> 00:22:13,399 Speaker 1: lacked the mass needed for gravity to kick start fusion. 366 00:22:14,280 --> 00:22:20,520 Speaker 1: But Jupiter is massive, truly, you could fit around within it. 367 00:22:20,520 --> 00:22:23,840 Speaker 1: It's the most massive planet in our Solar System, and 368 00:22:23,880 --> 00:22:26,760 Speaker 1: because of its mass and its position between Earth and 369 00:22:26,760 --> 00:22:30,800 Speaker 1: the chaos of the interstellar space outside of our Solar System, 370 00:22:31,000 --> 00:22:34,240 Speaker 1: Jupiter acts as a huge defensive guard for our planet. 371 00:22:34,800 --> 00:22:37,919 Speaker 1: When asteroids or comets or other flotsam and jetsam bent 372 00:22:38,000 --> 00:22:42,600 Speaker 1: on destruction in oer our Solar System, Jupiter's extraordinary gravitational 373 00:22:42,680 --> 00:22:46,200 Speaker 1: pull draws them into its orbit and slingshots them out 374 00:22:46,320 --> 00:22:49,880 Speaker 1: back into space. Without Jupiter to run interference for Earth, 375 00:22:50,480 --> 00:22:53,400 Speaker 1: it would have a steady diet of life ending bombardments 376 00:22:53,440 --> 00:22:59,520 Speaker 1: from space. So thanks Jupiter. This is astronomer Donald brown Lee. 377 00:23:00,040 --> 00:23:01,520 Speaker 1: He's one of the guys who came up with the 378 00:23:01,600 --> 00:23:08,600 Speaker 1: rare Earth hypothesis. Jupers are actually pretty rare uh planets 379 00:23:09,480 --> 00:23:13,359 Speaker 1: and um uh so uh in terms of rare Earth. 380 00:23:13,440 --> 00:23:16,040 Speaker 1: You know whether it was juper is good or bad. 381 00:23:16,200 --> 00:23:20,520 Speaker 1: Typical planet as systems probably don't have jupers. Our moon, too, 382 00:23:20,560 --> 00:23:23,399 Speaker 1: seems to have played a number of factors and fostering 383 00:23:23,440 --> 00:23:28,080 Speaker 1: life on Earth. Our moon's pretty unusual itself as far 384 00:23:28,119 --> 00:23:30,960 Speaker 1: as moons go. It's enormous. It's about one point to 385 00:23:31,160 --> 00:23:33,880 Speaker 1: percent the mass of the Earth and doesn't sound like much. 386 00:23:34,200 --> 00:23:37,240 Speaker 1: But other planets moons like Phobos and Demos, which or 387 00:23:37,240 --> 00:23:40,880 Speaker 1: a bit Mars, are closer to asteroids in size. Our 388 00:23:40,960 --> 00:23:44,320 Speaker 1: moon more resembles a small planet, and because it's so big, 389 00:23:44,600 --> 00:23:48,120 Speaker 1: it has some very peculiar effects on Earth. For one, 390 00:23:48,160 --> 00:23:52,120 Speaker 1: it stabilizes our planet. The Earth doesn't sit upright as 391 00:23:52,119 --> 00:23:55,480 Speaker 1: it spins around on its axis. It's tilted actually at 392 00:23:55,480 --> 00:23:59,159 Speaker 1: about a twenty three degree angle. Because of this tilt, 393 00:23:59,280 --> 00:24:03,359 Speaker 1: we have seas which create predictable variations in the temperature 394 00:24:03,440 --> 00:24:05,800 Speaker 1: of regions on Earth over the course of the year. 395 00:24:06,920 --> 00:24:09,639 Speaker 1: So when you think about the difference between winter and summer, 396 00:24:09,960 --> 00:24:12,359 Speaker 1: you get a good idea how much variation a tilt 397 00:24:12,400 --> 00:24:15,199 Speaker 1: can create. And add more of an angle to the 398 00:24:15,240 --> 00:24:18,280 Speaker 1: tilt and the Earth and the temperature variations would become 399 00:24:18,320 --> 00:24:21,840 Speaker 1: more severe. Since during winter or hemisphere would be further 400 00:24:21,880 --> 00:24:24,440 Speaker 1: away than it is now from the Sun and much 401 00:24:24,480 --> 00:24:27,720 Speaker 1: closer in the summer. And if you added in some wobble, 402 00:24:27,960 --> 00:24:30,760 Speaker 1: like if the tilt of the Earth wasn't stable and fluctuated, 403 00:24:31,200 --> 00:24:34,320 Speaker 1: all of these wild swings and temperature could make it 404 00:24:34,440 --> 00:24:38,000 Speaker 1: very difficult for life to take hold. The Moon's mass 405 00:24:38,040 --> 00:24:41,280 Speaker 1: actually exerts gravity over Earth and keeps it stable, not 406 00:24:41,440 --> 00:24:44,399 Speaker 1: wobbling or tilting more than it does, and allowing for 407 00:24:44,480 --> 00:24:49,480 Speaker 1: a nice, gradual, predictable and not two varying seasonal temperature 408 00:24:49,520 --> 00:24:52,600 Speaker 1: shifts that we even have a moon appears to be 409 00:24:52,640 --> 00:24:55,640 Speaker 1: a fluke itself. The current view is that the Moon 410 00:24:55,760 --> 00:24:58,520 Speaker 1: was calved off from Earth following a head on collision 411 00:24:58,520 --> 00:25:01,399 Speaker 1: in the Earth's early history with a planetoid about the 412 00:25:01,440 --> 00:25:04,800 Speaker 1: size of Mars called Thea, which the Earth likely absorbed. 413 00:25:05,640 --> 00:25:09,520 Speaker 1: This giant impact hypothesis explains a lot. The Moon is 414 00:25:09,600 --> 00:25:12,760 Speaker 1: unusually large and unusually close to us because it was 415 00:25:12,840 --> 00:25:16,000 Speaker 1: created of a mixture of Earth and that fateful planetoid. 416 00:25:17,000 --> 00:25:19,760 Speaker 1: Because the Moon is so close to Earth, it's tidally 417 00:25:19,840 --> 00:25:23,360 Speaker 1: locked and orbit around us. It doesn't spin on its axis, 418 00:25:23,600 --> 00:25:25,679 Speaker 1: which is why we always see the same side of 419 00:25:25,680 --> 00:25:28,840 Speaker 1: the Moon as it orbits us. This is an important 420 00:25:28,840 --> 00:25:31,840 Speaker 1: feature because it also creates the tide you're on Earth. 421 00:25:33,440 --> 00:25:36,600 Speaker 1: As the Moon orbits Earth, it pulls the oceans toward it, 422 00:25:37,119 --> 00:25:39,520 Speaker 1: stretching them out on the ends and narrowing them in 423 00:25:39,560 --> 00:25:42,919 Speaker 1: the middle. We hear on our planet experience this as 424 00:25:43,000 --> 00:25:45,360 Speaker 1: low tide or high tide, depending on where you are. 425 00:25:46,119 --> 00:25:48,520 Speaker 1: And it was in these tidal pools of young Earth's 426 00:25:48,520 --> 00:25:56,160 Speaker 1: oceans where some people think life began. When those ancient 427 00:25:56,240 --> 00:25:59,520 Speaker 1: tides came in, they deposited a flood of molecules into 428 00:25:59,560 --> 00:26:02,760 Speaker 1: the tidle pools, and as they withdrew and the water 429 00:26:02,800 --> 00:26:06,880 Speaker 1: evaporated in the sun, the increasing concentration of salt could 430 00:26:06,880 --> 00:26:10,560 Speaker 1: have provided just the right laboratory conditions where those earliest 431 00:26:10,600 --> 00:26:14,040 Speaker 1: chemicals could combine. Without a moon as large and as 432 00:26:14,080 --> 00:26:17,080 Speaker 1: close as ours is, these tides could not have existed 433 00:26:17,119 --> 00:26:19,800 Speaker 1: on Earth, and those early proteins would have lacked that 434 00:26:19,880 --> 00:26:23,719 Speaker 1: kind of natural peatrie dish. So the moon itself is 435 00:26:23,760 --> 00:26:27,440 Speaker 1: a collection of exquisite coincidences that supported life on Earth. 436 00:26:28,040 --> 00:26:31,119 Speaker 1: But perhaps the most peculiar aspect of Earth is that 437 00:26:31,160 --> 00:26:34,000 Speaker 1: it has massive plates that make up the crust, which 438 00:26:34,080 --> 00:26:37,960 Speaker 1: slide along a molten bed underneath that. It, in other words, 439 00:26:38,000 --> 00:26:41,919 Speaker 1: features plate tectonics. It thought that this is a major 440 00:26:42,119 --> 00:26:46,680 Speaker 1: reason why the Earth has actually had an amazingly stable 441 00:26:47,240 --> 00:26:50,680 Speaker 1: climate for most of you know, temperatures for for most 442 00:26:50,720 --> 00:26:56,119 Speaker 1: of its uh age. So it's drastically different than Venus 443 00:26:56,240 --> 00:26:59,920 Speaker 1: or or Mars, which are famously unstable over tri lage 444 00:27:00,240 --> 00:27:02,920 Speaker 1: uh time scope. So so we really owe a lot 445 00:27:03,359 --> 00:27:06,000 Speaker 1: uh to this. We don't really know why I played 446 00:27:06,040 --> 00:27:09,919 Speaker 1: tectonics works on our on Earth. It doesn't work on Mars, 447 00:27:10,000 --> 00:27:12,240 Speaker 1: it doesn't work on vines, it doesn't work on mercury, 448 00:27:12,240 --> 00:27:15,639 Speaker 1: doesn't work on any Yeah, I mean they're there, are 449 00:27:15,640 --> 00:27:17,679 Speaker 1: you know, movements of rocks rolled to each other, but 450 00:27:17,720 --> 00:27:21,040 Speaker 1: not I played tectonics of the type that we that 451 00:27:21,119 --> 00:27:23,160 Speaker 1: we have here, So so we think it's really important. 452 00:27:23,560 --> 00:27:25,880 Speaker 1: As far as we know, Earth is the only planet 453 00:27:25,880 --> 00:27:29,440 Speaker 1: to feature plate tectonics, which actually is a massive thermostat 454 00:27:29,520 --> 00:27:34,040 Speaker 1: for the planet. When oceanic plates slide underneath the lighter 455 00:27:34,119 --> 00:27:38,600 Speaker 1: continental plates, massive amounts of the oceanic crusts is crushed 456 00:27:38,720 --> 00:27:42,520 Speaker 1: and absorbed into magma. The rock in those oceanic plates 457 00:27:42,720 --> 00:27:46,720 Speaker 1: contains huge stores of carbon dioxide, so when volcanoes release 458 00:27:46,800 --> 00:27:49,840 Speaker 1: magma from beneath the crust, it also contains some of 459 00:27:49,840 --> 00:27:52,920 Speaker 1: that CEO two, which travels as a gas up into 460 00:27:52,960 --> 00:27:57,040 Speaker 1: the atmosphere and there it hangs around and it absorbs sunlight, 461 00:27:57,400 --> 00:28:00,800 Speaker 1: which in term warms the atmosphere and eventually the planet below. 462 00:28:01,560 --> 00:28:04,280 Speaker 1: And when the planet warms, more of the oceans evaporate, 463 00:28:04,600 --> 00:28:07,879 Speaker 1: warming the atmosphere even more. When you have a warm, 464 00:28:08,280 --> 00:28:13,119 Speaker 1: wet atmosphere, you have lots of rain that rain brings 465 00:28:13,160 --> 00:28:16,399 Speaker 1: dissolves c O two back down to Earth. Rocks on 466 00:28:16,440 --> 00:28:19,040 Speaker 1: Earth are an excellent store of carbon, and when CO 467 00:28:19,359 --> 00:28:22,000 Speaker 1: two rich, rain falls on them as the knock on 468 00:28:22,080 --> 00:28:25,720 Speaker 1: effect of weathering them, meaning the wearing down definition, not 469 00:28:25,800 --> 00:28:29,119 Speaker 1: the opposite one. All of that carbon in the rocks 470 00:28:29,119 --> 00:28:31,600 Speaker 1: and rain makes its way to the sea, where it 471 00:28:31,640 --> 00:28:35,440 Speaker 1: dissolves and eventually sinks to the ocean's bottom. As more 472 00:28:35,480 --> 00:28:38,560 Speaker 1: carbon is removed from the atmosphere and stored, the planet 473 00:28:38,600 --> 00:28:42,040 Speaker 1: begins to cool again. Over time, the carbon at the 474 00:28:42,040 --> 00:28:45,640 Speaker 1: bottom of the ocean forms new oceanic plate crusts, and 475 00:28:45,720 --> 00:28:49,200 Speaker 1: eventually it will find itself along an ocean ridge where 476 00:28:49,200 --> 00:28:52,080 Speaker 1: it collides with the continental plate and the whole process 477 00:28:52,160 --> 00:28:55,080 Speaker 1: begins again, and the Earth starts to warm once more. 478 00:28:56,800 --> 00:28:59,800 Speaker 1: This unique property of Earth has kept the planet's climate 479 00:29:00,040 --> 00:29:04,040 Speaker 1: stable more or less constantly for more than four billion years, 480 00:29:04,600 --> 00:29:12,920 Speaker 1: which has allowed life on Earth to grow and flourish. 481 00:29:14,320 --> 00:29:17,120 Speaker 1: When you take all of these details together, a weird 482 00:29:17,200 --> 00:29:21,600 Speaker 1: picture of Earth emerges. It's almost freakishly perfect for life. 483 00:29:22,440 --> 00:29:26,120 Speaker 1: That's so many different variables, each at just the right temperature, 484 00:29:26,400 --> 00:29:30,600 Speaker 1: just the right location, heat time, whatever would come together 485 00:29:30,800 --> 00:29:33,960 Speaker 1: to form a stable whole seems to make Earth a 486 00:29:34,040 --> 00:29:38,080 Speaker 1: staggeringly improbable place. You couldn't ask for a better place 487 00:29:38,120 --> 00:29:42,120 Speaker 1: for life to emerge. And maybe that's the point. Maybe 488 00:29:42,120 --> 00:29:45,000 Speaker 1: the seeds of life are commonplace in the universe, but 489 00:29:45,120 --> 00:29:49,680 Speaker 1: Earth is unique. We simply don't know. We still know 490 00:29:49,800 --> 00:29:53,200 Speaker 1: so little about space, our galaxy, and the universe that 491 00:29:53,280 --> 00:29:55,960 Speaker 1: we can't say if Earth is freakishly unique or one 492 00:29:56,000 --> 00:29:58,880 Speaker 1: of many. And as we get better at deducing the 493 00:29:58,880 --> 00:30:02,360 Speaker 1: existence of habit of planets with our space telescopes, they 494 00:30:02,360 --> 00:30:05,040 Speaker 1: seem to pop out of the cosmos like a magic 495 00:30:05,080 --> 00:30:07,400 Speaker 1: eye poster does when you lose focus in just the 496 00:30:07,480 --> 00:30:10,680 Speaker 1: right way. Maybe planets that can sustain life are more 497 00:30:10,680 --> 00:30:14,920 Speaker 1: abundantly the universe than we realize perhaps assembling those seeds 498 00:30:14,920 --> 00:30:18,360 Speaker 1: into life is where the filter lies. The farther back 499 00:30:18,400 --> 00:30:22,080 Speaker 1: we look in time, the less we understand. So if 500 00:30:22,080 --> 00:30:25,000 Speaker 1: you're going to look for something that might be really hard, 501 00:30:25,120 --> 00:30:27,960 Speaker 1: harder than it seems, farther back in time is the 502 00:30:28,040 --> 00:30:32,200 Speaker 1: plausible place to look, because that's where we don't understand things. Uh, 503 00:30:32,200 --> 00:30:35,840 Speaker 1: And the very first step from completely dead matter to 504 00:30:35,960 --> 00:30:39,720 Speaker 1: some proto life that has to be the earliest step 505 00:30:39,720 --> 00:30:42,280 Speaker 1: on the one we have the least knowledge of, and 506 00:30:42,400 --> 00:30:46,320 Speaker 1: more plausibly it's the hardest step. Or perhaps not. Perhaps 507 00:30:46,400 --> 00:30:49,600 Speaker 1: right now the universe is teeming with primitive life. Perhaps 508 00:30:49,600 --> 00:30:53,520 Speaker 1: the great filter lies somewhere after that. There were, after all, 509 00:30:53,760 --> 00:30:56,520 Speaker 1: some enormous steps to get from the emergence of life 510 00:30:56,520 --> 00:30:59,360 Speaker 1: here on Earth in the moment we're sharing between us 511 00:31:00,160 --> 00:31:16,480 Speaker 1: right now, m back on the early Earth, tucked away 512 00:31:16,560 --> 00:31:19,200 Speaker 1: just so, in a solar system, tucked away just so, 513 00:31:19,400 --> 00:31:23,040 Speaker 1: in the galaxy with its volcanoes chugging away at producing 514 00:31:23,040 --> 00:31:26,680 Speaker 1: a warm atmosphere and its oceans producing a warm liquid 515 00:31:26,720 --> 00:31:30,200 Speaker 1: medium for molecules to organize into life. At some point, 516 00:31:30,920 --> 00:31:34,840 Speaker 1: one particular moment in Earth's history, all of those separate 517 00:31:34,880 --> 00:31:39,200 Speaker 1: components came together to form a full fledged living cell. 518 00:31:40,560 --> 00:31:42,800 Speaker 1: As far as we can tell, this moment happened around 519 00:31:42,840 --> 00:31:46,520 Speaker 1: three point eight billion years ago. At first, these simple, 520 00:31:46,680 --> 00:31:50,280 Speaker 1: single celled organisms were nothing more than gooey bags, with 521 00:31:50,400 --> 00:31:53,680 Speaker 1: the parts for replicating themselves and the parts for converting 522 00:31:53,680 --> 00:31:57,160 Speaker 1: food into energy all slashing together inside of the cell. 523 00:31:58,360 --> 00:32:02,560 Speaker 1: They spread by dividing into exact replicas of themselves. But 524 00:32:02,640 --> 00:32:06,040 Speaker 1: over time, over a very very long time, some new 525 00:32:06,160 --> 00:32:09,280 Speaker 1: versions of these simple cells began to appear, and they 526 00:32:09,280 --> 00:32:15,200 Speaker 1: had new specializations. Their interiors became compartmentalized, no longer slashing together, 527 00:32:15,680 --> 00:32:18,760 Speaker 1: which meant that the processes they carried out, like converting 528 00:32:18,800 --> 00:32:23,880 Speaker 1: that food to energy, became vastly more efficient. So processes 529 00:32:23,920 --> 00:32:27,240 Speaker 1: like photosynthesis were able to develop. And after they did, 530 00:32:27,720 --> 00:32:31,280 Speaker 1: the oxygen that this early cellular life excreted as waste 531 00:32:31,680 --> 00:32:35,440 Speaker 1: started to settle into the atmosphere, creating an entirely new 532 00:32:35,480 --> 00:32:38,600 Speaker 1: one that would eventually support the rise of new types 533 00:32:38,640 --> 00:32:42,400 Speaker 1: of life. Then comes the invention of sex, a new 534 00:32:42,400 --> 00:32:46,400 Speaker 1: type of reproduction where two entirely distinct individuals combined to 535 00:32:46,440 --> 00:32:49,840 Speaker 1: form a new third version of themselves. And it's about 536 00:32:49,880 --> 00:32:53,640 Speaker 1: here that natural selection cracks its knuckles and comes aboard 537 00:32:54,080 --> 00:32:57,840 Speaker 1: as the driving force of evolution here on Earth. When 538 00:32:57,960 --> 00:33:01,520 Speaker 1: natural selection is presented with new options rather than rough 539 00:33:01,600 --> 00:33:05,840 Speaker 1: copies of the same thing, new adaptations emerge much more quickly, 540 00:33:06,200 --> 00:33:11,280 Speaker 1: which kicks evolution into hyper drive. The simple celled organisms 541 00:33:11,320 --> 00:33:14,120 Speaker 1: that made up life on Earth got better at being 542 00:33:14,200 --> 00:33:19,840 Speaker 1: living things, and then for a long time nothing much changed. 543 00:33:20,680 --> 00:33:24,200 Speaker 1: It seems as if life had reached the stasis, maxed out, 544 00:33:24,600 --> 00:33:28,720 Speaker 1: come upon some invisible wall, and take into coasting. Rather 545 00:33:28,800 --> 00:33:33,440 Speaker 1: than progressing toward ever more complexity, Earth seemed content with 546 00:33:33,560 --> 00:33:38,280 Speaker 1: its fast seas teeming with specialized, extremely well adapted, single 547 00:33:38,320 --> 00:33:42,760 Speaker 1: celled organisms. After that first three hundred million years of 548 00:33:42,880 --> 00:33:46,480 Speaker 1: ceaseless innovation, life on earths stayed the same for the 549 00:33:46,520 --> 00:33:51,080 Speaker 1: next three billion years. But around five hundred million years 550 00:33:51,080 --> 00:33:56,400 Speaker 1: ago something huge happened. Life suddenly developed new ambitions, and 551 00:33:56,480 --> 00:34:01,760 Speaker 1: it exploded into new, extremely complicated and sophisticated forms. And 552 00:34:01,800 --> 00:34:07,040 Speaker 1: in geological terms, it happened overnight. Basically go from nothing 553 00:34:07,120 --> 00:34:11,560 Speaker 1: to everything. This is Dr Phoebe Cohen. She's a paleontologist 554 00:34:11,640 --> 00:34:16,440 Speaker 1: at Williams College in Massachusetts. So the vast majority of 555 00:34:16,600 --> 00:34:22,080 Speaker 1: the history of life on Earth is that of microscopic organisms. 556 00:34:22,719 --> 00:34:27,239 Speaker 1: Before the Cambrian almost all life was microscopic or at 557 00:34:27,280 --> 00:34:32,040 Speaker 1: least very very small, and ecosystems were dominated by things 558 00:34:32,080 --> 00:34:37,319 Speaker 1: like amiba and bacteria. And after the Cambrian ecosystems are 559 00:34:37,360 --> 00:34:40,839 Speaker 1: dominated by animals, um and so it's a really, really 560 00:34:40,920 --> 00:34:46,200 Speaker 1: huge shift in the biological evolution of our planet. This 561 00:34:46,280 --> 00:34:50,160 Speaker 1: sudden surge in complexity is called the Cambrian Explosion. We 562 00:34:50,200 --> 00:34:53,319 Speaker 1: aren't quite sure why it happened. It's possible it was 563 00:34:53,360 --> 00:34:56,920 Speaker 1: triggered when the widespread glaciation that covered Earth just before 564 00:34:56,920 --> 00:35:00,000 Speaker 1: it began to melt. Or perhaps it was the oxygen 565 00:35:00,000 --> 00:35:04,359 Speaker 1: and levels in the atmosphere released by photosynthesis slowly displacing 566 00:35:04,400 --> 00:35:08,359 Speaker 1: the Earth's atmosphere of carbon dioxide, ammonia, and methane. We 567 00:35:08,400 --> 00:35:11,040 Speaker 1: need lots of oxygen to power the conversion of food 568 00:35:11,040 --> 00:35:14,879 Speaker 1: to energy, and perhaps the Cambrian explosion was triggered when 569 00:35:14,920 --> 00:35:18,640 Speaker 1: atmospheric oxygen reached a critical threshold that could support more 570 00:35:18,719 --> 00:35:21,960 Speaker 1: complex life. So if you go into low oxygen areas 571 00:35:22,000 --> 00:35:24,319 Speaker 1: of the ocean today, there's plenty of animals living with 572 00:35:24,360 --> 00:35:27,160 Speaker 1: almost no oxygen, but they're not doing anything. They're very boring. 573 00:35:27,280 --> 00:35:30,040 Speaker 1: They kind of just lay there because they don't have 574 00:35:30,160 --> 00:35:33,960 Speaker 1: enough oxygen to do anything exciting. So one idea is 575 00:35:34,000 --> 00:35:36,799 Speaker 1: that oxygen did reach some sort of threshold around the 576 00:35:36,840 --> 00:35:40,719 Speaker 1: Cambrian that enabled organisms to start doing fun things like 577 00:35:40,960 --> 00:35:44,080 Speaker 1: chasing after each other and ripping each other apart, and 578 00:35:44,120 --> 00:35:46,800 Speaker 1: that that played a big role in changing sort of 579 00:35:46,840 --> 00:35:50,000 Speaker 1: the structure of ecosystems that lead to a huge diversification 580 00:35:50,719 --> 00:35:55,279 Speaker 1: um within the animal claid. Whatever the reason, half a 581 00:35:55,280 --> 00:35:58,759 Speaker 1: billion years ago, most of the complex body plans that 582 00:35:58,760 --> 00:36:02,960 Speaker 1: are still around on Earth to day suddenly arrived. It's 583 00:36:03,000 --> 00:36:06,440 Speaker 1: as if those organizing principles of life entered a new phase. 584 00:36:07,600 --> 00:36:11,280 Speaker 1: Within just thirty million years, plants made their debut on land, 585 00:36:11,880 --> 00:36:15,239 Speaker 1: and just forty million years after that, animals followed them 586 00:36:15,239 --> 00:36:18,759 Speaker 1: out of the water. It's astounding to think of, but 587 00:36:18,840 --> 00:36:22,440 Speaker 1: within a span of just seventy million years, life on 588 00:36:22,520 --> 00:36:26,680 Speaker 1: Earth went from nothing but single celled aquatic organisms to 589 00:36:26,920 --> 00:36:30,200 Speaker 1: animals that lived and moved and walked around on land. 590 00:36:31,719 --> 00:36:34,799 Speaker 1: Because life had remained so simple for so long before it, 591 00:36:35,200 --> 00:36:39,080 Speaker 1: the Cambrian explosion makes an excellent candidate for the Great Filter. 592 00:36:39,960 --> 00:36:43,880 Speaker 1: It could be so unlikely that it universally denies intelligent 593 00:36:43,960 --> 00:36:48,399 Speaker 1: life from forming evolutionarily speaking, there's never been a more 594 00:36:48,400 --> 00:36:51,800 Speaker 1: important event in the history of Earth. Following the emergence 595 00:36:51,800 --> 00:36:55,680 Speaker 1: of life, twenty of the thirty six body plans that 596 00:36:55,800 --> 00:36:58,800 Speaker 1: exist on Earth today, the plans that give shape to 597 00:36:58,920 --> 00:37:02,640 Speaker 1: squid and the ish, and humans and worms, all suddenly 598 00:37:02,640 --> 00:37:06,480 Speaker 1: appeared on Earth, and those new body plans led to 599 00:37:06,640 --> 00:37:10,840 Speaker 1: a riot of evolution. The dinosaurs rose and fell, and 600 00:37:10,920 --> 00:37:13,840 Speaker 1: small mammals emerged from their burrows and climbed the trees. 601 00:37:14,640 --> 00:37:17,279 Speaker 1: Tree dwelling apes found their way out of the savannah 602 00:37:17,600 --> 00:37:21,400 Speaker 1: and started walking upright, becoming the first contours of humans. 603 00:37:22,360 --> 00:37:25,520 Speaker 1: And it's about here that we arrive at another step 604 00:37:25,719 --> 00:37:28,200 Speaker 1: in the long span between the emergence of life on 605 00:37:28,239 --> 00:37:36,239 Speaker 1: Earth and us, the evolution of intelligent life. Humans tend 606 00:37:36,239 --> 00:37:39,319 Speaker 1: to think of intelligence is what differentiates us from other 607 00:37:39,440 --> 00:37:42,680 Speaker 1: life on Earth, but instead we seem more like the 608 00:37:42,760 --> 00:37:50,520 Speaker 1: current endpoint in an evolution of intelligence. Signs of intelligence, 609 00:37:50,520 --> 00:37:53,680 Speaker 1: in some form or fashion are all around us. In 610 00:37:53,719 --> 00:37:57,600 Speaker 1: two thousand eight, Japanese researchers showed that slime mold, a 611 00:37:57,719 --> 00:38:02,520 Speaker 1: unicellular organism, can learn a schedule of electric shocks when 612 00:38:02,520 --> 00:38:05,759 Speaker 1: they shocked the mold at regular intervals, and yes, they 613 00:38:05,800 --> 00:38:09,360 Speaker 1: shocked mold. The mold learned to anticipate the next shock 614 00:38:09,600 --> 00:38:13,160 Speaker 1: and recoil from it before it was delivered. The Moosta 615 00:38:13,280 --> 00:38:16,080 Speaker 1: plants have shown that they can learn to differentiate between 616 00:38:16,080 --> 00:38:20,120 Speaker 1: being dropped and being touched. Where initially the plants responded 617 00:38:20,160 --> 00:38:23,680 Speaker 1: to both experiences in the same way by curling their leaves, 618 00:38:24,120 --> 00:38:26,680 Speaker 1: after being dropped several times, they learned to keep their 619 00:38:26,719 --> 00:38:30,399 Speaker 1: leaves unfurled, and they retain this learned behavior even after 620 00:38:30,440 --> 00:38:34,200 Speaker 1: they haven't been dropped or touched for months. The use 621 00:38:34,239 --> 00:38:38,280 Speaker 1: of tools, which we imagine is quintessentially human, isn't unique 622 00:38:38,280 --> 00:38:42,800 Speaker 1: to us either. Chimpanzees use tools to make gathering food easier, 623 00:38:43,239 --> 00:38:46,320 Speaker 1: like sticks to draw termites from their mountains by the fistful, 624 00:38:46,719 --> 00:38:49,319 Speaker 1: and rocks to bash open hard shelled nuts to get 625 00:38:49,360 --> 00:38:52,560 Speaker 1: to the meat inside. But at some point we drew 626 00:38:52,600 --> 00:38:55,440 Speaker 1: away from the rest of life. In the development of 627 00:38:55,480 --> 00:38:59,680 Speaker 1: our intelligence, we became the first animals to use tools 628 00:38:59,719 --> 00:39:03,480 Speaker 1: to make other tools. This is the birth of technology. 629 00:39:04,120 --> 00:39:06,880 Speaker 1: No longer were we relegated to using only what was 630 00:39:06,920 --> 00:39:10,160 Speaker 1: found in nature. We learned to use nature to fashion 631 00:39:10,200 --> 00:39:14,319 Speaker 1: new tools to better suit our needs. We made spearheads 632 00:39:14,320 --> 00:39:17,960 Speaker 1: and axes, out of stone and learned to hunt large animals. 633 00:39:18,320 --> 00:39:21,359 Speaker 1: Meat is more energy dense than plants, and we learned 634 00:39:21,360 --> 00:39:24,399 Speaker 1: to cook food about eight hundred thousand years ago. When 635 00:39:24,440 --> 00:39:26,799 Speaker 1: we did, we unlocked a tremendous amount of nutrients and 636 00:39:26,920 --> 00:39:31,560 Speaker 1: energy that hadn't been available to us before. We developed language, 637 00:39:31,840 --> 00:39:34,720 Speaker 1: which allowed us to better coordinate ourselves and hunt together 638 00:39:35,000 --> 00:39:38,640 Speaker 1: and interact with one another more effectively. We learned to 639 00:39:38,640 --> 00:39:41,040 Speaker 1: make clothes to keep us warm as we spread out 640 00:39:41,080 --> 00:39:44,680 Speaker 1: beyond the subtropical climate we evolved in. We learned to 641 00:39:44,680 --> 00:39:47,480 Speaker 1: make boats to carry us to new places. We learned 642 00:39:47,480 --> 00:39:50,120 Speaker 1: to make ceramics to store our food. We learned to 643 00:39:50,160 --> 00:39:52,719 Speaker 1: grow crops, which led to cities in the foundation of 644 00:39:52,760 --> 00:39:55,880 Speaker 1: the modern era. And there was another quirk of that 645 00:39:55,960 --> 00:39:59,360 Speaker 1: chance collision between the planetoid THEA, and Earth, which produced 646 00:39:59,360 --> 00:40:03,040 Speaker 1: the Moon. It also produced massive deposits of minerals and 647 00:40:03,080 --> 00:40:05,840 Speaker 1: metals near the surface that humans could easily get to. 648 00:40:06,680 --> 00:40:10,239 Speaker 1: Over time, we abandon those stone tools in favor of 649 00:40:10,239 --> 00:40:13,960 Speaker 1: more reliable metal ones, and eventually we put all of 650 00:40:13,960 --> 00:40:17,919 Speaker 1: those millions of years of accumulated intelligence and technology into 651 00:40:17,960 --> 00:40:21,200 Speaker 1: ships that broke the bonds of Earth and launched the 652 00:40:21,239 --> 00:40:25,719 Speaker 1: first of our species into space. Within the astronomically short 653 00:40:25,800 --> 00:40:29,360 Speaker 1: period of about a hundred thousand years, humans left the 654 00:40:29,400 --> 00:40:33,960 Speaker 1: wild and went to space. But perhaps as unlikely as 655 00:40:34,000 --> 00:40:37,320 Speaker 1: the emergence of human intelligence may seem, it may simply 656 00:40:37,360 --> 00:40:40,640 Speaker 1: be the expected outcome of those organizing principles of life. 657 00:40:41,400 --> 00:40:44,360 Speaker 1: There are two options before us. Then, either we humans 658 00:40:44,400 --> 00:40:47,560 Speaker 1: are unique in our universe and utterly alone, or we 659 00:40:47,640 --> 00:40:51,000 Speaker 1: are not. And if there is other life elsewhere, then 660 00:40:51,040 --> 00:40:54,279 Speaker 1: that means that the great filter, the hardest step, lies 661 00:40:54,360 --> 00:40:57,839 Speaker 1: not in our past, but in our future. It means 662 00:40:57,880 --> 00:41:00,480 Speaker 1: that the challenge that lies ahead of us is more difficult, 663 00:41:00,840 --> 00:41:05,239 Speaker 1: more improbable to overcome than dead molecules organizing themselves into 664 00:41:05,320 --> 00:41:08,759 Speaker 1: living cells or apes learning to build ships to the moon, 665 00:41:09,800 --> 00:41:12,160 Speaker 1: And rather than having millions of years to try and 666 00:41:12,160 --> 00:41:15,759 Speaker 1: fail before succeeding, we will have one shot to get 667 00:41:15,800 --> 00:41:19,240 Speaker 1: it right. If the great filter lies in our future, 668 00:41:19,719 --> 00:41:22,200 Speaker 1: then it appears that we are entering it right now, 669 00:41:22,800 --> 00:41:26,160 Speaker 1: now here in the twenty one century, four point three 670 00:41:26,200 --> 00:41:29,480 Speaker 1: billion years after life emerged on Earth. We are entering 671 00:41:29,480 --> 00:41:32,719 Speaker 1: the evolutionary step that no life in the universe has 672 00:41:32,760 --> 00:41:36,760 Speaker 1: ever managed to survive. Carl Sagan had this this great 673 00:41:37,040 --> 00:41:41,240 Speaker 1: phrase about humanity has grown powerful before it's grown wise 674 00:41:41,680 --> 00:41:45,960 Speaker 1: um and our power through technology has been increasing exponentially, 675 00:41:46,600 --> 00:41:50,680 Speaker 1: but our wisdom has been maybe it's been increasing a 676 00:41:50,719 --> 00:41:55,360 Speaker 1: little bit, but suddenly not exponentially, and it's it's getting 677 00:41:55,440 --> 00:41:57,040 Speaker 1: these two things have got out of check with each other. 678 00:41:57,320 --> 00:42:00,799 Speaker 1: We've got an unsustainable level of risk. The technology that 679 00:42:00,840 --> 00:42:02,920 Speaker 1: got us to this point is taking a new shape, 680 00:42:03,239 --> 00:42:06,280 Speaker 1: one that we haven't encountered before, and it is presenting 681 00:42:06,320 --> 00:42:09,840 Speaker 1: new risks to the survival of our species and indeed 682 00:42:09,880 --> 00:42:14,319 Speaker 1: life on Earth. You right now are living in what 683 00:42:14,440 --> 00:42:17,920 Speaker 1: maybe the beginning of the most dangerous period in the 684 00:42:18,040 --> 00:42:33,600 Speaker 1: history of the human race. On the next episode of 685 00:42:33,640 --> 00:42:36,719 Speaker 1: The End of the World with Josh Clark, if we 686 00:42:36,760 --> 00:42:39,760 Speaker 1: are the only intelligent life, humans could have a bright, 687 00:42:39,880 --> 00:42:43,920 Speaker 1: long future ahead of us, a triple less civilization based 688 00:42:44,040 --> 00:42:49,560 Speaker 1: on super intelligence, super happiness, and super longevity. But between 689 00:42:49,640 --> 00:42:53,120 Speaker 1: us and that bright future lay existential risks, and they're 690 00:42:53,160 --> 00:42:55,120 Speaker 1: like nothing we've ever encountered before.