WEBVTT 1 00:00:03.399 --> 00:00:07.719 Welcome to Bedtime Astronomy. Explore the wonders of the cosmos 2 00:00:07.759 --> 00:00:12.279 with our soothing Bedtime Astronomie podcast. Each episode offers a 3 00:00:12.359 --> 00:00:16.320 gentle journey through the stars, planets, and beyond, perfect for 4 00:00:16.399 --> 00:00:20.239 unwinding after a long day. Let's travel through the mysteries 5 00:00:20.239 --> 00:00:22.440 of the universe as you drift off into a peaceful 6 00:00:22.480 --> 00:00:23.800 slumber under the night sky. 7 00:00:26.879 --> 00:00:29.199 Are we alone in the universe? I mean, it's a 8 00:00:29.359 --> 00:00:32.560 huge question, isn't it something humans have probably asked forever 9 00:00:32.640 --> 00:00:33.799 looking up at the night sky. 10 00:00:34.000 --> 00:00:37.880 Absolutely, it taps into something really fundamental about our place 11 00:00:37.960 --> 00:00:38.799 in the cosmos. 12 00:00:39.000 --> 00:00:42.000 For so long it felt, you know, purely philosophical or 13 00:00:42.320 --> 00:00:46.200 maybe just science fiction fodder. But it seems like actual 14 00:00:46.280 --> 00:00:49.679 scientific research is starting to weigh in, maybe giving us 15 00:00:49.679 --> 00:00:52.200 a more well, a more precise answer. 16 00:00:52.439 --> 00:00:55.719 That's right. Recent studies are trying to model the probabilities 17 00:00:55.759 --> 00:00:59.520 based on what we know about planets, stars, and life itself. 18 00:01:00.079 --> 00:01:04.200 Sure that's emerging is maybe a bit surprising, Perhaps not 19 00:01:04.239 --> 00:01:06.400 the crowded galaxy we sometimes imagine. 20 00:01:06.480 --> 00:01:09.159 It certainly suggests the odds might be steeper than we thought, 21 00:01:09.480 --> 00:01:12.159 especially for technological civilizations like ours. 22 00:01:12.319 --> 00:01:14.239 Okay, so that's what we're exploring today. We're going to 23 00:01:14.280 --> 00:01:17.680 look at some really fascinating findings about well, the incredible 24 00:01:17.719 --> 00:01:22.719 odds stacked against finding other technological civilizations just in our 25 00:01:22.760 --> 00:01:24.599 own galaxy, the Milky Way. 26 00:01:24.879 --> 00:01:28.120 Yeah, looking at the specific conditions needed, the planetary set up, 27 00:01:28.159 --> 00:01:29.239 the atmosphere, and the. 28 00:01:29.200 --> 00:01:33.159 Time scales, almost unimaginable amounts of time involved for life 29 00:01:33.200 --> 00:01:36.560 not just to appear, but to get to a technological stage. 30 00:01:36.680 --> 00:01:38.439 Exactly. It's a multi layered challenge. 31 00:01:38.480 --> 00:01:42.120 So get ready because our discussion today might just shift 32 00:01:42.159 --> 00:01:43.840 how you think about those little lights in the sky. 33 00:01:44.319 --> 00:01:47.799 We'll touch on how rare, how incredibly far away, and 34 00:01:47.840 --> 00:01:51.519 maybe how astonishingly old any cosmic neighbors might actually be. 35 00:01:51.599 --> 00:01:52.959 It puts things in perspective. 36 00:01:53.120 --> 00:01:56.000 Okay, let's unpack this. Then. We've all seen the movies, right, 37 00:01:56.040 --> 00:02:01.319 Star Trek, Star Wars, alien civilizations just jump away. But 38 00:02:01.359 --> 00:02:05.120 when we talk about actually finding another civilization, what kind 39 00:02:05.159 --> 00:02:07.599 of distances, what kind of time scales are we really 40 00:02:07.719 --> 00:02:09.719 up against? According to this new. 41 00:02:09.560 --> 00:02:13.240 Research, well, the scale is the first major hurdle. The 42 00:02:13.319 --> 00:02:16.280 reality based on these models is far more daunting than 43 00:02:16.280 --> 00:02:19.159 fiction suggests. Right, And it's not just the distance, although 44 00:02:19.199 --> 00:02:23.319 that's enormous. What's really fascinating or maybe sobering, is how 45 00:02:23.319 --> 00:02:26.520 the sheer scale of space and time compound the challenge 46 00:02:26.560 --> 00:02:30.199 as well. It's not enough to just find life or 47 00:02:30.240 --> 00:02:34.039 even evidence that life existed somewhere else, sometime else. For 48 00:02:34.199 --> 00:02:37.280 us to detect another technological civilization, they need to be 49 00:02:37.319 --> 00:02:39.800 existing concurrently with us right now. 50 00:02:40.039 --> 00:02:42.719 Ah Okay, So they can't be long gone, and they 51 00:02:42.719 --> 00:02:44.960 can't be millions of years in the future. They have 52 00:02:45.039 --> 00:02:48.240 to overlap with our tiny window of technological. 53 00:02:47.599 --> 00:02:51.000 Existence precisely, and that is a huge constraint. So when 54 00:02:51.000 --> 00:02:55.599 we delve into the numbers from recent studies, well they 55 00:02:55.599 --> 00:02:56.560 give us some estimates. 56 00:02:56.639 --> 00:02:57.240 Let's hear them. 57 00:02:57.319 --> 00:03:01.039 Okay. So the estimate for the closest technol logical species 58 00:03:01.080 --> 00:03:05.000 to us in the entire Milky Way galaxy could be 59 00:03:05.039 --> 00:03:07.639 as far as thirty three thousand light years away. 60 00:03:07.680 --> 00:03:09.199 Thirty three thousand light years. 61 00:03:09.240 --> 00:03:10.479 Thirty three thousand light years. 62 00:03:10.680 --> 00:03:12.719 Wow, Okay. Put that in perspective for us, how far 63 00:03:12.759 --> 00:03:13.280 is that really? 64 00:03:13.360 --> 00:03:16.319 Well, think about this. Our own solar system is roughly 65 00:03:16.479 --> 00:03:18.879 twenty seven thousand light years from the center of the 66 00:03:18.919 --> 00:03:22.599 Milky Way. Okay, So thirty three thousand light years means well, 67 00:03:22.639 --> 00:03:25.719 it means our nearest technological neighbors could easily be on 68 00:03:25.759 --> 00:03:27.400 the other side of the galaxy from us. 69 00:03:27.400 --> 00:03:30.039 The other side, so not just a different neighborhood, but 70 00:03:30.159 --> 00:03:32.319 a whole different continent cosmically. 71 00:03:31.919 --> 00:03:35.800 Speaking, exactly. Imagine trying to shout across a continent and 72 00:03:35.840 --> 00:03:38.960 hoping someone hears you. Now, not ten thousand years ago. 73 00:03:39.520 --> 00:03:42.759 Light itself takes thirty three thousand years to make that journey, So. 74 00:03:42.800 --> 00:03:45.120 Any signal we send takes that long to get there, 75 00:03:45.360 --> 00:03:47.639 and any signal they send takes that long get here. 76 00:03:47.960 --> 00:03:49.680 Communication isn't exactly. 77 00:03:49.360 --> 00:03:52.919 Real time, not even close. It's profoundly ancient by the 78 00:03:52.919 --> 00:03:56.759 time it arrives. It really paints a picture of potentially 79 00:03:56.800 --> 00:03:59.120 extreme isolation even within our own galaxy. 80 00:03:59.199 --> 00:04:02.919 Okay, thirty three thousand light years that distance alone is 81 00:04:03.919 --> 00:04:07.479 mind boggling. But then you mentioned this concurrency thing. They 82 00:04:07.479 --> 00:04:09.919 have to be there, now, how does that layer on top? 83 00:04:10.120 --> 00:04:12.400 Ah, That's where it gets even trickier, because for a 84 00:04:12.439 --> 00:04:15.360 civilization to exist at the same time as us, even 85 00:04:15.400 --> 00:04:19.160 across that vast distance, it needs to be incredibly long lived. 86 00:04:18.959 --> 00:04:21.360 Right, because they had to start existing long enough ago 87 00:04:21.399 --> 00:04:23.959 for their light or signals to reach us now, and 88 00:04:24.000 --> 00:04:25.959 they have to still be existing exactly. 89 00:04:26.160 --> 00:04:30.199 And this research, using planetary models and astrophysical data, tries 90 00:04:30.199 --> 00:04:33.040 to estimate how long lived they'd need to be. The 91 00:04:33.120 --> 00:04:37.040 minimum suggested survival time is two hundred and eighty thousand years. 92 00:04:37.240 --> 00:04:41.639 Two hundred and eighty thousand years minimum minimum, and potentially 93 00:04:41.879 --> 00:04:47.240 millions of years millions. Yeah, for a technological civilization to survive. 94 00:04:47.160 --> 00:04:52.120 Yes, think about what that implies. A species evolves intelligence, 95 00:04:52.199 --> 00:04:56.199 develops technology, and then manages to sustain itself at society, 96 00:04:56.199 --> 00:04:59.639 it's technology for hundreds of thousands, maybe millions of years. 97 00:05:00.199 --> 00:05:02.519 To us, Yeah, I mean how long we've been technological? 98 00:05:02.879 --> 00:05:05.680 A few centuries since the Industrial Revolution, maybe a few 99 00:05:05.720 --> 00:05:06.920 millennia with writing in. 100 00:05:06.959 --> 00:05:10.240 Cities, it's a blink of an eye. In comparison, to 101 00:05:10.319 --> 00:05:13.720 imagine a civilization lasting for say two hundred and eighty 102 00:05:13.759 --> 00:05:18.199 thousand years or ten million years requires contemplating a level 103 00:05:18.199 --> 00:05:22.319 of stability, resilience, resource management, problem solving on a scale 104 00:05:22.319 --> 00:05:23.399 we can barely conceive of. 105 00:05:23.639 --> 00:05:25.720 It suggests they would have had to overcome challenges we 106 00:05:25.720 --> 00:05:28.439 haven't even faced yet or are maybe facing right now. 107 00:05:28.560 --> 00:05:31.240 Precisely, it's not just about finding life. It's about finding 108 00:05:31.279 --> 00:05:35.959 a civilization that has somehow mastered long term survival against 109 00:05:36.079 --> 00:05:40.079 cosmic and potentially self inflicted threats. Well, it's a profound constraint. 110 00:05:40.160 --> 00:05:42.040 So it really hammers home that this isn't just a 111 00:05:42.079 --> 00:05:45.160 spatial search looking for a needle in a cosmic haystack. 112 00:05:45.720 --> 00:05:48.319 It's also a temporal one, a needle that might have 113 00:05:48.399 --> 00:05:51.639 existed ages ago, or might exist ages from now, or 114 00:05:51.680 --> 00:05:54.040 as maybe on the completely other side of the haystack 115 00:05:54.160 --> 00:05:56.439 right now, but has to have been there for an 116 00:05:56.480 --> 00:05:57.560 incredibly long time. 117 00:05:57.600 --> 00:06:00.399 That's a good way to put it. Concurrent exists is 118 00:06:00.439 --> 00:06:03.439 the key, and it demands exceptional longevity. 119 00:06:03.639 --> 00:06:06.439 Okay, so let's zoom in a bit. Forget the vast 120 00:06:06.519 --> 00:06:09.800 distances in times for a moment. What about the place itself? 121 00:06:10.079 --> 00:06:13.439 The planet? What makes a planet even capable of hosting 122 00:06:13.480 --> 00:06:16.240 such a long lived civilization. It can't just be any 123 00:06:16.319 --> 00:06:18.959 random planet, surely, what's the recipe? 124 00:06:19.079 --> 00:06:22.240 No, absolutely not, and you've hit on the next crucial layer. 125 00:06:22.279 --> 00:06:25.480 It's far more than just say, having liquid water, although 126 00:06:25.480 --> 00:06:27.399 that's generally considered essential, right. 127 00:06:27.319 --> 00:06:28.480 The fall of the water approach. 128 00:06:28.680 --> 00:06:31.879 Yeah, but this research we're exploring today really emphasizes the 129 00:06:31.959 --> 00:06:35.920 strong odds against finding truly earth like worlds capable of 130 00:06:35.959 --> 00:06:40.759 supporting complex technological life over billions of years. It boils 131 00:06:40.800 --> 00:06:43.920 down to a few critical, interconnected factors. 132 00:06:43.519 --> 00:06:46.079 Like a cosmic recipe, where everything has to be just right. 133 00:06:46.199 --> 00:06:50.240 Exactly, perfect measurements, perfect temperatures, perfect chemistry, all sustained for 134 00:06:50.319 --> 00:06:54.160 geological ages. Let's look at some of those key ingredients, 135 00:06:54.199 --> 00:06:56.360 starting with something quite fundamental to Earth. 136 00:06:56.720 --> 00:07:00.800 Okay, plate tectonics, plate techtics like earthquakes in volcanoes. How 137 00:07:00.800 --> 00:07:02.279 does that relate to alien life. 138 00:07:02.439 --> 00:07:05.480 Well, we tend to see the surface effects the dramatic stuff. 139 00:07:05.839 --> 00:07:09.639 But plate tectonics, the slow movement of continental plates, is 140 00:07:09.720 --> 00:07:13.759 actually vital for regulating Earth's long term climate. It acts 141 00:07:13.800 --> 00:07:17.399 like a planetary thermostat the thermosat. How it's mainly through 142 00:07:17.439 --> 00:07:21.680 its role in the carbon silicate cycle. Basically CO two 143 00:07:21.800 --> 00:07:25.120 in the atmosphere dissolves in rain water, making it slightly acidic. 144 00:07:25.879 --> 00:07:30.040 This rain whethers silicate rocks on land, washing dissolved carbon 145 00:07:30.040 --> 00:07:33.240 and minerals into the oceans. Okay, in the oceans, tiny 146 00:07:33.319 --> 00:07:36.000 organisms use some of that dissolves stuff to build shells, 147 00:07:36.079 --> 00:07:40.000 mostly calcium carbonate. When they die, their shells sinc forming 148 00:07:40.040 --> 00:07:42.560 sediment locking away carbon on the ocean floor. 149 00:07:42.800 --> 00:07:45.040 So it pulls CO two out of the air over time. 150 00:07:45.319 --> 00:07:50.680 Yes, But then plate tectonics comes in through subduction where 151 00:07:50.800 --> 00:07:54.399 one plate slides under another. These carbon rich sediments get 152 00:07:54.519 --> 00:07:58.279 dragged down into the earth mantle over millions of years. 153 00:07:58.600 --> 00:08:01.000 The heat and pressure release. It's the CO two which 154 00:08:01.000 --> 00:08:04.439 eventually comes back out into the atmosphere through volcanic eruptions. 155 00:08:04.560 --> 00:08:07.319 Ah. So it recycles the carbon, It pulls it out 156 00:08:07.360 --> 00:08:10.319 when there's too much, releases it when there's too little. 157 00:08:10.480 --> 00:08:15.439 Exactly, it's this incredibly slow but effective feedback loop. It 158 00:08:15.480 --> 00:08:18.639 prevents Earth from getting stuck in a runaway greenhouse like Venus, 159 00:08:18.759 --> 00:08:21.600 or freezing over completely like Mars might have done. It 160 00:08:21.680 --> 00:08:24.720 keeps a climate relatively stable over hundreds of millions of years, 161 00:08:24.759 --> 00:08:27.319 which is crucial for complex life to evolve. 162 00:08:27.399 --> 00:08:30.920 Wow. So plate tectonics isn't just about geology, it's about 163 00:08:30.959 --> 00:08:34.799 long term habitability. But you mentioned even with this system 164 00:08:35.120 --> 00:08:37.360 there's a potential problem a ticking clock. 165 00:08:37.600 --> 00:08:39.840 Yeah, that's the intriguing part. It's a great system, but 166 00:08:39.879 --> 00:08:43.200 it might not be perfectly balanced forever over very long 167 00:08:43.240 --> 00:08:45.759 time scales. There seems to be a natural tendency for 168 00:08:45.879 --> 00:08:47.960 more CO two to get locked away in rocks, then 169 00:08:48.039 --> 00:08:50.559 gets recycled back out through volcanism. 170 00:08:50.080 --> 00:08:51.360 Like a slow leak in the system. 171 00:08:51.679 --> 00:08:55.919 Kind of Yeah, a slow geological sequestration of CO two, 172 00:08:56.759 --> 00:09:00.200 And this leads to an inherent ticking clock on planetary habitability, 173 00:09:00.320 --> 00:09:03.480 at least for life like ours. Oh so well on Earth. 174 00:09:03.720 --> 00:09:07.960 The projection suggests that because of this slow depletion, atmospheric 175 00:09:08.000 --> 00:09:11.480 CO two levels will eventually drop too low for photosynthesis 176 00:09:11.480 --> 00:09:13.639 as we know it to continue efficiently. 177 00:09:13.679 --> 00:09:16.320 Photosynthesis will stop the basis of most of our food 178 00:09:16.360 --> 00:09:17.159 chain eventually. 179 00:09:17.240 --> 00:09:20.320 Yes, the estimates vary, but it could be somewhere between 180 00:09:20.519 --> 00:09:23.360 say two hundred million and maybe up to a billion 181 00:09:23.399 --> 00:09:25.960 years from now. Doctor Scherf, one of the researchers we're 182 00:09:26.000 --> 00:09:29.080 drawing on, puts it bluntly. At some point enough carbon 183 00:09:29.120 --> 00:09:32.159 dioxide will be drawn from the atmosphere so that photosynthesis 184 00:09:32.200 --> 00:09:33.120 will stop working. 185 00:09:33.320 --> 00:09:36.080 Wow, So the planet's own life support system had that 186 00:09:36.159 --> 00:09:39.080 kind of built in expiry date for complex life. 187 00:09:38.759 --> 00:09:41.840 For oxygen producing photosynthesis. It seems so, And this has 188 00:09:42.000 --> 00:09:45.440 huge implications for finding et well. If a planet doesn't 189 00:09:45.480 --> 00:09:47.960 have clate tectonics to regulate CO two in the first place, 190 00:09:48.240 --> 00:09:52.000 it might become uninhabitable much faster, or even if it does, 191 00:09:52.159 --> 00:09:55.159 like Earth, maybe this CO two depletion clock runs faster 192 00:09:55.279 --> 00:09:58.399 under different conditions. It means the window of time during 193 00:09:58.399 --> 00:10:01.039 which a planet can support comple flex life, let alone 194 00:10:01.080 --> 00:10:04.960 technological life needing billions of years to evolve, might be 195 00:10:05.080 --> 00:10:06.600 much narrower than we thought. 196 00:10:06.840 --> 00:10:09.879 So you need the geology, the thermostat. Yeah, but even 197 00:10:09.960 --> 00:10:14.080 then the fuel for life, the CO two slowly runs out. 198 00:10:14.159 --> 00:10:17.799 That really emphasizes the fragility. Okay, So the geology sets 199 00:10:17.840 --> 00:10:21.039 the stage, regulates the climate. But what about the air itself, 200 00:10:21.159 --> 00:10:22.440 the atmospheric mix. 201 00:10:22.519 --> 00:10:25.600 Right, because even with the right temperature regulation, the specific 202 00:10:25.639 --> 00:10:28.879 composition of the atmosphere is absolutely critical, not just for 203 00:10:28.960 --> 00:10:31.399 life to exist, but for its complexity and its potential 204 00:10:31.399 --> 00:10:32.080 for technology. 205 00:10:32.120 --> 00:10:36.159 Okay, Earth's atmosphere is mostly nitrogen, then oxygen, tiny bit 206 00:10:36.240 --> 00:10:36.960 of CO two. 207 00:10:36.840 --> 00:10:40.159 Yep, about seventy eight percent nitrogen twenty one percent oxygen, 208 00:10:40.200 --> 00:10:43.440 and that crucial tiny fraction of CO two around point 209 00:10:43.559 --> 00:10:45.639 zero four two percent, which keeps us warm via the 210 00:10:45.679 --> 00:10:46.440 greenhouse effect. 211 00:10:46.519 --> 00:10:48.480 But that CO two level is delicate, right. 212 00:10:48.679 --> 00:10:53.080 Extremely delicate. Too much CO two and a planet overheats 213 00:10:53.679 --> 00:10:57.759 think venus a runaway greenhouse effect, ocean's boiled away surface 214 00:10:57.840 --> 00:11:01.039 hot enough to melt lead. Or maybe the atmosphere just 215 00:11:01.039 --> 00:11:04.159 becomes too dense and toxic for familiar life into little 216 00:11:04.200 --> 00:11:07.039 too little, and the planet freezes. It can't retain enough 217 00:11:07.080 --> 00:11:09.840 heat from its star, so you need that sweet spot. 218 00:11:10.080 --> 00:11:12.240 So the research looked at different CO two levels. 219 00:11:12.279 --> 00:11:15.639 It did, and interestingly, it explored a scenario where a 220 00:11:15.639 --> 00:11:18.039 planet might have more CO two than Earth but could 221 00:11:18.039 --> 00:11:19.480 still be habitable for longer. 222 00:11:19.600 --> 00:11:21.200 How would that work? Wouldn't it overheat? 223 00:11:22.200 --> 00:11:25.320 Not necessarily if other factors compensate. The model suggest a 224 00:11:25.360 --> 00:11:28.799 planet with say ten percent carbon dioxide much higher than Earth's, 225 00:11:28.799 --> 00:11:32.080 could potentially maintain its biosphere its capacity for life for 226 00:11:32.120 --> 00:11:34.559 a staggering four point two billion years. 227 00:11:34.399 --> 00:11:37.120 Longer than Earth's projected habitable lifestam. 228 00:11:36.759 --> 00:11:40.799 Potentially, yes, but there's a catch, always a catch, right 229 00:11:41.519 --> 00:11:44.480 to avoid a runaway greenhouse with that much CO two, 230 00:11:44.840 --> 00:11:47.480 the planet would need to be significantly farther away from 231 00:11:47.480 --> 00:11:50.279 its star than Earth is from the Sun, or its 232 00:11:50.279 --> 00:11:53.799 star would need to be dimmer younger. Perhaps the extra 233 00:11:53.879 --> 00:11:56.120 CO two provides a thicker blanket, so you need less 234 00:11:56.120 --> 00:11:57.240 heat from the star. 235 00:11:57.159 --> 00:12:00.960 Okay, so location, location, location matters MATT precisely to the 236 00:12:01.000 --> 00:12:02.559 atmospheric CO two exactly. 237 00:12:02.799 --> 00:12:05.720 In contrast that ten percent CO two scenario with one 238 00:12:05.759 --> 00:12:09.519 having just one percent CO two, that planet's biosphere might 239 00:12:09.639 --> 00:12:12.559 only last a maximum of three point one billion years 240 00:12:12.600 --> 00:12:16.480 before CO two depletion becomes critical. So the initial amount 241 00:12:16.480 --> 00:12:19.039 of CO two interacting with the planet's geology and its 242 00:12:19.120 --> 00:12:22.120 distance from the star sets a fundamental limit on how 243 00:12:22.159 --> 00:12:24.000 long complex life might have to evolve. 244 00:12:24.159 --> 00:12:27.799 It's such a fine tune system geology, atmosphere, orbit. Yeah, 245 00:12:27.840 --> 00:12:30.600 I'll have to align perfectly. Okay, Well you mentioned oxygen two. 246 00:12:30.679 --> 00:12:33.200 Obviously we needed to breathe. How does that factor into 247 00:12:33.200 --> 00:12:34.480 the technology side? Ah? 248 00:12:34.559 --> 00:12:38.240 Yes, Oxygen is fascinating because it's not just about respiration 249 00:12:38.320 --> 00:12:41.759 for complex animals, which definitely need higher oxygen levels than microbes. 250 00:12:42.120 --> 00:12:45.759 It's about something even more fundamental for technology. Fire. Fire 251 00:12:46.159 --> 00:12:48.960 studies show that if the oxygen concentration in an atmosphere 252 00:12:49.000 --> 00:12:53.279 drops blow about eighteen percent, you can't have open air combustion. 253 00:12:53.639 --> 00:12:55.480 We really like a match wouldn't. 254 00:12:55.200 --> 00:12:58.480 Light exactly, A match wouldn't light, Wood wouldn't burn reliably 255 00:12:58.480 --> 00:13:00.559 in the open air. You couldn't sustain a camp fire, 256 00:13:00.879 --> 00:13:03.759 let alone the intense heat needed for things like smelting 257 00:13:03.840 --> 00:13:04.279 metal in. 258 00:13:04.279 --> 00:13:05.919 A furnace, and without fire. 259 00:13:06.120 --> 00:13:09.159 Without fire, the path to technology as we know it 260 00:13:09.240 --> 00:13:12.360 hits a dead end very early on. Think about it. 261 00:13:12.559 --> 00:13:16.440 The Bronze Age, the Iron age. They fundamentally depended on 262 00:13:16.519 --> 00:13:19.759 harnessing fire to extract metals from ore and forge them 263 00:13:19.759 --> 00:13:24.759 into tools, weapons, structures, metalworking, no metalworking, no steam engines, 264 00:13:24.799 --> 00:13:29.360 later on, no complex machinery, probably no advanced chemistry. It's 265 00:13:29.360 --> 00:13:31.960 hard to even imagine building a radio telescope or a 266 00:13:32.000 --> 00:13:35.000 spacecraft without the foundational technology that fire enabled. 267 00:13:35.200 --> 00:13:37.440 So you need enough oxygen not just to breathe, but 268 00:13:37.480 --> 00:13:41.480 specifically above that eighteen percent threshold to even get basic 269 00:13:41.559 --> 00:13:44.480 metallurgy off the ground, which seems like a prerequisite for 270 00:13:44.600 --> 00:13:45.600 any advanced attack. 271 00:13:45.840 --> 00:13:51.200 Precisely, it's another critical bottleneck. The atmosphere needs enough oxygen 272 00:13:51.240 --> 00:13:53.879 for complex life and enough for the key tool that 273 00:13:53.960 --> 00:13:55.799 unlocks advanced material science. 274 00:13:56.759 --> 00:13:59.159 Fire. So let me see you've got this straight. We 275 00:13:59.200 --> 00:14:03.200 need a planet with plate tectonics for long term climate stability. 276 00:14:03.799 --> 00:14:06.960 We need a very specific CO two level balanced with 277 00:14:07.039 --> 00:14:09.799 its distance from the star to keep temperatures right and 278 00:14:09.840 --> 00:14:13.960 sustain photosynthesis for potentially billions of years, and we need 279 00:14:14.000 --> 00:14:16.759 oxygen levels high enough, probably over eighteen percent, not just 280 00:14:16.759 --> 00:14:20.919 for complex animals, but crucially for fire enabling metallurgy and technology. 281 00:14:21.000 --> 00:14:23.559 That sums it up pretty well. It's an incredibly specific 282 00:14:23.679 --> 00:14:26.159 and likely quite fragile set of circumstances. 283 00:14:26.200 --> 00:14:31.159 It really makes Earth feel well, exceptionally fortunate, almost impossibly so. Okay, so, 284 00:14:31.240 --> 00:14:34.120 even if a planet somehow wins this incredible cosmic lottery 285 00:14:34.120 --> 00:14:37.200 and has all these conditions aligned, what's the next big 286 00:14:37.279 --> 00:14:41.200 hurdle for a technological civilization to actually be detectable bias? 287 00:14:41.600 --> 00:14:44.320 Well, winning the planetary lottery is just stage one. Stage 288 00:14:44.360 --> 00:14:47.480 two is time, specifically the enormous amount of time it 289 00:14:47.519 --> 00:14:49.720 takes for technological life to evolve in the first place, 290 00:14:49.759 --> 00:14:53.519 and then crucially, the time it manages to persist. Persist 291 00:14:53.559 --> 00:14:58.159 you mean survive, survive, Yes, survive itself, survive cosmic accidents, 292 00:14:58.519 --> 00:15:00.879 survive for long enough to own relap with us. 293 00:15:00.919 --> 00:15:03.120 Okay, how long did it take here on Earth? 294 00:15:03.200 --> 00:15:06.320 Well, our planet is about four point five billion years old, 295 00:15:06.720 --> 00:15:10.000 and technological life really only emerged in the last tiny 296 00:15:10.039 --> 00:15:12.919 fraction of that time, so it took roughly four point 297 00:15:12.960 --> 00:15:16.480 five billion years of evolution through countless steps in stages. 298 00:15:16.559 --> 00:15:17.679 That's a huge amount of time. 299 00:15:17.840 --> 00:15:20.960 It is. Think of the milestones the origin of life 300 00:15:21.039 --> 00:15:24.559 itself from non life that's a biogenesis, than the evolution 301 00:15:24.639 --> 00:15:28.399 of photosynthesis, which changed the whole atmosphere. Then the leap 302 00:15:28.440 --> 00:15:33.480 to multicellular life from single cells, then complex animals, nervous systems, 303 00:15:33.600 --> 00:15:37.799 intelligence tool use. Each step took hundreds of millions, sometimes 304 00:15:37.840 --> 00:15:39.600 billions of years, and there's. 305 00:15:39.440 --> 00:15:41.600 No guarantee that sequence happens everywhere, or it takes the 306 00:15:41.639 --> 00:15:45.159 same amount of time absolutely not, which brings us to longevity. 307 00:15:45.559 --> 00:15:50.039 The longer technological species manages to survive after it develops technology, 308 00:15:50.240 --> 00:15:52.440 the greater the chance it exists at the same time 309 00:15:52.440 --> 00:15:55.759 as another civilization like us. This is where that idea 310 00:15:55.759 --> 00:15:58.279 of the great filter often comes up, the idea that 311 00:15:58.279 --> 00:16:00.720 there are these huge hurdle's life to overcome. 312 00:16:00.879 --> 00:16:04.240 Exactly maybe the filter is behind us, like the origin 313 00:16:04.279 --> 00:16:07.399 of life or complex cells, meaning life itself is rare, 314 00:16:07.879 --> 00:16:09.679 or maybe the filter is ahead of us, meaning that 315 00:16:09.720 --> 00:16:14.240 becoming technological is relatively easy, but surviving with technology for 316 00:16:14.279 --> 00:16:16.519 a long time is extremely hard. 317 00:16:16.919 --> 00:16:20.279 And this research suggests the survival part is key very key. 318 00:16:20.399 --> 00:16:23.519 The calculations done by Shurf and Lammer really drive this home. 319 00:16:23.840 --> 00:16:26.960 Remember that planet with ten percent CO two potentially habitable 320 00:16:27.039 --> 00:16:28.480 for four point two billion years. 321 00:16:28.519 --> 00:16:30.039 Yeah, the one farther from its star. 322 00:16:30.159 --> 00:16:33.879 Right Even on such a potentially long lasting habitable world, 323 00:16:33.960 --> 00:16:37.759 for there to be just one other technological civilization in 324 00:16:37.799 --> 00:16:39.759 the Milky Way at the same time as us, that 325 00:16:39.879 --> 00:16:43.039 civilization would need to have survived on average for at 326 00:16:43.120 --> 00:16:45.759 least two hundred and eighty thousand years just for. 327 00:16:45.840 --> 00:16:48.759 One other civilization to exist concurrently. 328 00:16:48.879 --> 00:16:52.440 Yes, minimum average life span two hundred eighty thousand years. 329 00:16:52.480 --> 00:16:56.919 Think about that, maintaining stability, avoiding self destruction, managing resources, 330 00:16:56.919 --> 00:16:59.519 weather in cosmic storms for over a quarter of a 331 00:16:59.519 --> 00:17:00.240 million year. 332 00:17:00.360 --> 00:17:04.599 That puts our few centuries of industrial society into perspective chromatically. 333 00:17:04.640 --> 00:17:07.279 So, and it gets even more stark if you hope 334 00:17:07.319 --> 00:17:10.279 for more neighbors. How So, for there to be say, 335 00:17:10.599 --> 00:17:15.319 ten technological civilizations existing concurrently in the galaxy right now, 336 00:17:15.559 --> 00:17:18.599 the calculation suggests the average lifetime of each one needs 337 00:17:18.640 --> 00:17:24.799 to be over ten million years ten million years average average. 338 00:17:24.839 --> 00:17:28.759 As doctor Scherf noted, the number of potential alien civilizations 339 00:17:28.759 --> 00:17:32.240 depends strongly upon the lifetime of a civilization. It's not 340 00:17:32.279 --> 00:17:37.279 just about evolving, it's about enduring, surviving asteroid impacts, climate shifts, 341 00:17:37.279 --> 00:17:41.960 maybe internal conflicts, resource depletion, pandemics, you name it. 342 00:17:42.160 --> 00:17:45.559 Ten million years. I can barely imagine what human society 343 00:17:45.640 --> 00:17:47.720 might look like in ten thousand years, let alone ten million. 344 00:17:47.720 --> 00:17:50.599 That get well, it suggests any civilization we do find 345 00:17:50.599 --> 00:17:52.519 is almost certain to be vastly older than us. 346 00:17:52.599 --> 00:17:55.160 That's a very strong implication of these numbers. Yes, yeah, 347 00:17:55.240 --> 00:17:58.319 they wouldn't likely be newcomers to the technological stage. They'd 348 00:17:58.319 --> 00:18:00.640 be the survivors, the ones who figured out how to 349 00:18:00.720 --> 00:18:04.359 last for time, skills that are frankly geological. That's a 350 00:18:04.400 --> 00:18:08.240 truly staggering thought. Not just aliens, but ancient aliens who've 351 00:18:08.240 --> 00:18:12.720 mastered longevity. It highlights this potential fragility. Maybe the immense 352 00:18:12.799 --> 00:18:16.799 challenge of surviving your own technological advancement. Maybe that's the 353 00:18:16.799 --> 00:18:17.359 great filter. 354 00:18:17.559 --> 00:18:20.759 It's certainly a possibility that many researchers consider the challenge 355 00:18:20.799 --> 00:18:23.960 might not be intelligence, but wisdom and sustainability. 356 00:18:24.039 --> 00:18:27.599 Okay, these numbers, these conditions, they paint a compelling picture. 357 00:18:28.200 --> 00:18:31.880 Thirty three thousand light years away, needing to survive for 358 00:18:32.160 --> 00:18:35.759 maybe millions of years on a planet with incredibly specific 359 00:18:36.319 --> 00:18:41.160 geology and atmosphere. It makes technological life seem remarkably improbable, 360 00:18:41.880 --> 00:18:44.920 but science is always learning, right. How solid are these 361 00:18:44.920 --> 00:18:46.920 figures are their big unknowns, That's a. 362 00:18:46.839 --> 00:18:49.799 Really important point, and the researchers themselves are very clear 363 00:18:49.839 --> 00:18:52.319 about this. These numbers thirty three thousand light years, two 364 00:18:52.400 --> 00:18:56.640 hundred and eighty thousand years minimum survival, the atmospheric thresholds 365 00:18:56.920 --> 00:19:02.119 based on our current best understanding of astrophysics, minitary science, geology, biology. 366 00:19:02.480 --> 00:19:05.279 There are robust estimates based on today's knowledge. 367 00:19:04.960 --> 00:19:06.279 But not absolute certainties. 368 00:19:06.599 --> 00:19:11.039 Definitely not absolutes. There are inherent uncertainties in the models, 369 00:19:11.160 --> 00:19:15.680 and new discoveries, especially about exoplanets and Earth's own deep history, 370 00:19:16.119 --> 00:19:20.440 are constantly refining our understanding. Think of these as the 371 00:19:20.440 --> 00:19:23.279 best most informed calculations we can make now. 372 00:19:23.359 --> 00:19:26.960 And are there factors that just aren't in the calculation yet, 373 00:19:26.960 --> 00:19:28.759 things we don't know enough about precisely? 374 00:19:28.920 --> 00:19:33.119 The research explicitly acknowledges several huge factors that ideally should 375 00:19:33.160 --> 00:19:36.880 be included, but we simply can't quantify them reliably at 376 00:19:36.920 --> 00:19:42.440 the moment. They remain major unknowns. Genuine cosmic mysteries like what. Well, 377 00:19:42.480 --> 00:19:44.920 probably the biggest one is the origin of life itself 378 00:19:45.160 --> 00:19:48.640 a biogenesis. How does non living matter become living? How 379 00:19:48.680 --> 00:19:51.440 often does that happen? Even if conditions are perfect? We 380 00:19:51.480 --> 00:19:53.720 only have Earth as an example. Was it a near 381 00:19:53.759 --> 00:19:56.960 inevitable chemical process here or an incredibly lucky fluke? We 382 00:19:57.079 --> 00:19:58.759 just don't know the probability, right. 383 00:19:58.799 --> 00:20:02.039 If starting life is super rare, then even perfect planets 384 00:20:02.119 --> 00:20:03.799 might stay empty exactly. 385 00:20:04.200 --> 00:20:08.839 Then there's the origin of photosynthesis, specifically oxygen producing photosynthesis. 386 00:20:09.240 --> 00:20:12.839 It terrorformed our planet, paving the way for complex life. 387 00:20:13.240 --> 00:20:17.200 How likely is that specific biochemical pathway to evolve? Are 388 00:20:17.240 --> 00:20:20.920 there other ways complex ecosystems can be powered? Another big unknown? 389 00:20:21.119 --> 00:20:21.960 Okay, what else? 390 00:20:22.119 --> 00:20:25.839 The origin of multicellular life? Earth had only single celled 391 00:20:25.839 --> 00:20:28.519 life for what maybe three billion years? 392 00:20:28.599 --> 00:20:29.119 The leap to. 393 00:20:29.200 --> 00:20:33.440 Complex, coordinated multicellular organisms like plants and animals was a 394 00:20:33.519 --> 00:20:37.400 huge step. Maybe another major bottleneck. How often does that happen? 395 00:20:37.519 --> 00:20:40.799 Hmmm? The true life existed for ages before it got big. 396 00:20:41.000 --> 00:20:44.240 And then even if you get complex intelligent life, there's 397 00:20:44.240 --> 00:20:47.440 the frequency with which intelligence develops. Technology of the kind 398 00:20:47.480 --> 00:20:51.799 we could detect, think radio waves, large structures, atmospheric modification. 399 00:20:52.440 --> 00:20:55.359 Is that an inevitable path for intelligence or just one possibility. 400 00:20:55.680 --> 00:20:58.640 Maybe other intelligent species focus inward or develop in ways 401 00:20:58.640 --> 00:21:00.000