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 --> 00:00:25.000 slumber under the night sky. 7 00:00:26.920 --> 00:00:29.839 If you close your eyes and try to picture the 8 00:00:29.960 --> 00:00:33.520 ultimate space getaway, you might imagine staring out the reinforced 9 00:00:33.560 --> 00:00:37.759 window of a spacecraft just watching this beautiful, pristine world 10 00:00:38.079 --> 00:00:39.119 slowly drifting past. 11 00:00:39.159 --> 00:00:41.679 Now, absolutely that classic sci fi view. 12 00:00:41.759 --> 00:00:43.960 Right, And I really want to paint that picture for 13 00:00:44.000 --> 00:00:47.320 you today, because back in February of nineteen seventy four, 14 00:00:47.960 --> 00:00:50.479 humanity actually got a view of something that looked exactly 15 00:00:50.560 --> 00:00:50.799 like that. 16 00:00:51.000 --> 00:00:52.719 Yeah, the Mariner ten flyby. 17 00:00:52.640 --> 00:00:55.960 Exactly NASA's Mariner ten spacecraft. Yeah, it's hurtling through the 18 00:00:55.960 --> 00:00:58.280 inner Solar System. And as it performed this fly by, 19 00:00:58.320 --> 00:01:02.280 a venus the camera snap this incredibly striking series of photographs. 20 00:01:02.359 --> 00:01:04.439 They're iconic images, really they are. 21 00:01:04.599 --> 00:01:07.280 And when you look at those archival images, the planet 22 00:01:07.359 --> 00:01:11.599 just looks entirely peaceful. I mean It's this perfectly smooth, featureless, 23 00:01:11.920 --> 00:01:15.239 pearly white orb just hanging there in the pitch blackness 24 00:01:15.239 --> 00:01:15.719 of space. 25 00:01:15.879 --> 00:01:17.599 It looks completely harmless, right. 26 00:01:17.680 --> 00:01:21.879 There are no jagged crater's visible, no raging storms tearing 27 00:01:21.879 --> 00:01:24.640 across the surface, no harsh colors. It just looks like 28 00:01:24.680 --> 00:01:30.159 a giant, pristine marble, serene quiet. I'm completely underscurbed. 29 00:01:30.439 --> 00:01:34.280 It really is a stunning piece of cosmic imagery. But 30 00:01:35.200 --> 00:01:37.719 it is also one of the greatest deceptions in our 31 00:01:37.879 --> 00:01:38.760 entire solar system. 32 00:01:38.879 --> 00:01:40.000 The ultimate catfish. 33 00:01:40.120 --> 00:01:43.439 Yeah, exactly. We are so conditioned as humans to look 34 00:01:43.480 --> 00:01:47.719 at a smooth, white, cloudy surface and associate it with calm, 35 00:01:47.920 --> 00:01:50.439 you know, maybe a soft winter day or a gentle fog. 36 00:01:50.760 --> 00:01:52.799 Right, it looks like a cloud you could just bounce on. 37 00:01:53.280 --> 00:01:56.480 But what Mariner ten actually captured was, well, it's essentially 38 00:01:56.560 --> 00:02:01.040 planetary scale camouflage, because right beneath those trenk pearly white 39 00:02:01.079 --> 00:02:06.480 clouds is an environment so hostiles, so thoroughly apocalyptic that 40 00:02:06.560 --> 00:02:09.319 it is quite literally the closest thing to Hell we 41 00:02:09.400 --> 00:02:11.479 have ever discovered in our cosmic neighborhood. 42 00:02:11.599 --> 00:02:14.199 Wow, and I think we need to completely shatter that 43 00:02:14.280 --> 00:02:17.360 peaceful illusion right out of the gate because the reality 44 00:02:17.400 --> 00:02:20.599 of what is happening under that pristine veil is almost 45 00:02:21.319 --> 00:02:22.240 it's hard to comprehend. 46 00:02:22.280 --> 00:02:24.960 It defies everyday logic, honestly, it really does. 47 00:02:25.159 --> 00:02:27.319 Like if you were to somehow drop down beneath that 48 00:02:27.400 --> 00:02:29.879 pearly white exterior in a protective suit and try to 49 00:02:29.919 --> 00:02:32.319 just stand on the surface, you wouldn't be standing at all. 50 00:02:32.319 --> 00:02:33.919 You'd be instantaneously crushed. 51 00:02:33.919 --> 00:02:34.879 Oh, completely flattened. 52 00:02:35.080 --> 00:02:37.759 Yeah, because the atmosphere of pressure down there is ninety 53 00:02:37.759 --> 00:02:40.560 two times greater than what we experience standing at sea 54 00:02:40.639 --> 00:02:42.680 level here on Earth. Ninety two times. 55 00:02:43.319 --> 00:02:46.479 To put the sheer physics of that into perspective, experiencing 56 00:02:46.599 --> 00:02:49.879 ninety two bars of atmospheric pressure is the equivalent of 57 00:02:49.919 --> 00:02:52.800 being nearly a kilometer or so about three thousand feet 58 00:02:52.879 --> 00:02:54.280 underwater in Earth's oceans. 59 00:02:54.520 --> 00:02:56.520 Wait, three thousand feet deep. 60 00:02:56.680 --> 00:02:59.680 Yeah, if you think about the kind of heavy, incredibly 61 00:02:59.680 --> 00:03:02.800 reenf force titanium submersibles we have to build just to 62 00:03:02.840 --> 00:03:06.319 survive at those depths, that is the baseline environment on 63 00:03:06.360 --> 00:03:07.439 the surface of Venus. 64 00:03:07.560 --> 00:03:10.360 That is terrifying. Just standing there as like being at 65 00:03:10.400 --> 00:03:11.960 the bottom of the ocean. 66 00:03:11.639 --> 00:03:14.439 And it gets stranger actually, because the atmosphere at the 67 00:03:14.439 --> 00:03:16.879 surface is so dense that it doesn't even behave like 68 00:03:16.919 --> 00:03:20.280 a normal gas anymore. It exists as what physicists call 69 00:03:20.360 --> 00:03:21.919 a supercritical fluid. 70 00:03:22.159 --> 00:03:25.520 Okay, wait, a supercritical fluid that sounds like something out 71 00:03:25.520 --> 00:03:28.400 of a sci fi reactor core. How does an entire 72 00:03:28.439 --> 00:03:29.919 atmosphere become supercritical? 73 00:03:29.960 --> 00:03:32.400 It's wild, right. It happens when you have carbon dioxide, 74 00:03:32.439 --> 00:03:35.599 which makes up about ninety six percent of Venus' atmosphere, 75 00:03:35.840 --> 00:03:40.560 and it gets subjected to extreme pressure and extreme heat simultaneously. 76 00:03:39.960 --> 00:03:42.240 So it's basically being squeezed and baked at the same 77 00:03:42.240 --> 00:03:43.199 time exactly. 78 00:03:43.280 --> 00:03:47.000 It passes the specific critical point where the distinct boundary 79 00:03:47.039 --> 00:03:50.400 between a liquid and a gas just entirely disappear. So 80 00:03:50.400 --> 00:03:52.240 you aren't walking through a heavy breeze. 81 00:03:51.960 --> 00:03:53.479 Down there, What are you walking through them? 82 00:03:53.639 --> 00:03:57.159 You'd be wading through this thick, soupy, viscous fluid that 83 00:03:57.360 --> 00:04:00.639 constantly surrounds and crushes everything at time. I mean, it 84 00:04:00.639 --> 00:04:03.240 flows like a gas, but it has the dissolving power 85 00:04:03.280 --> 00:04:04.879 in the density of a liquid. 86 00:04:04.639 --> 00:04:08.159 That is deeply, deeply unsettling. You're wading through a glowing, 87 00:04:08.719 --> 00:04:12.039 crushing soup and we haven't even brought up the temperature. 88 00:04:12.120 --> 00:04:14.479 Yet oh right, the heat is a whole other nightmare. 89 00:04:14.560 --> 00:04:18.399 Yeah, the surface of Venus sits at a staggering four 90 00:04:18.439 --> 00:04:22.639 hundred and sixty seven degrees celsius. That's eight hundred and 91 00:04:22.639 --> 00:04:24.519 seventy three degrees fahrenheit. 92 00:04:24.120 --> 00:04:26.279 Which is hotter than the surface of Mercury. By the way, 93 00:04:26.319 --> 00:04:28.079 even the mercury is much closer to the sun. 94 00:04:28.399 --> 00:04:30.759 Right, And just to give a practical reference for that 95 00:04:30.839 --> 00:04:32.800 kind of heat for you listening, if you took a 96 00:04:32.839 --> 00:04:36.040 solid block of lead or zinc or tin and just 97 00:04:36.040 --> 00:04:38.519 set it on the ground on Venus, it would instantly 98 00:04:38.560 --> 00:04:39.519 melt into a puddle. 99 00:04:39.600 --> 00:04:42.000 It would just liquify, just liquify. 100 00:04:42.879 --> 00:04:46.240 And to put the final terrifying touch on this whole environment, 101 00:04:46.560 --> 00:04:49.720 those serene clouds we talked about from the Mariner ten photos, 102 00:04:50.079 --> 00:04:51.959 the ones that look like a soft winter. 103 00:04:51.800 --> 00:04:53.720 Fog, Yeah, definitely not water vapor. 104 00:04:53.839 --> 00:04:56.199 No, they are made of concentrated sulfuric acid. 105 00:04:56.560 --> 00:05:00.000 And that acid cycle is particularly vicious too. It actually 106 00:05:00.199 --> 00:05:03.199 rain sulfuric acid high up in the atmosphere, but the 107 00:05:03.279 --> 00:05:08.000 surface is so unimaginably hot that the acid rain boils 108 00:05:08.000 --> 00:05:11.839 and evaporates miles before it ever even hits the ground. 109 00:05:12.000 --> 00:05:16.279 So it's just this permanent hovering acid mist exactly. 110 00:05:16.399 --> 00:05:19.560 It forms a permanent corrosive haze. It is a world 111 00:05:19.600 --> 00:05:22.360 that seems actively designed to destroy anything that comes near it, 112 00:05:22.759 --> 00:05:26.959 which makes the underlying reality of Venus so bewildering for 113 00:05:27.079 --> 00:05:28.959 planetary scientists. 114 00:05:28.560 --> 00:05:30.959 Because it shouldn't be like this, right, No, not at all. 115 00:05:31.160 --> 00:05:34.160 By almost every metric we have. Venus shouldn't be a hellscape. 116 00:05:34.160 --> 00:05:35.240 It should be Earth's twin. 117 00:05:35.480 --> 00:05:37.439 That's the part that really boggles the mind. If you 118 00:05:37.480 --> 00:05:40.600 look at the rostats, Earth and Venus are practically identical, 119 00:05:40.639 --> 00:05:42.680 I mean, yeah, roughly the same size, they have almost 120 00:05:42.680 --> 00:05:44.920 the same mass, they have similar gravity. 121 00:05:44.519 --> 00:05:46.240 They're virtually the same age too. 122 00:05:46.680 --> 00:05:49.319 Right, They're located in the same general neighborhood of the 123 00:05:49.360 --> 00:05:51.879 inner Solar System, and they formed at the exact same 124 00:05:51.920 --> 00:05:54.560 time out of the exact same primordial dust and gas. 125 00:05:54.759 --> 00:05:57.480 If you are an alien astronomer looking at our Solar 126 00:05:57.480 --> 00:06:00.680 System from say a thousand light years away, you would 127 00:06:00.680 --> 00:06:04.879 see two blue, green, habitable looking planets right next to 128 00:06:04.920 --> 00:06:07.720 each other. You would assume they evolved identically. 129 00:06:08.160 --> 00:06:10.959 So how do you start with two identical twins made 130 00:06:11.000 --> 00:06:13.199 of the same stuff at the same time and end 131 00:06:13.279 --> 00:06:17.480 up with one being this vibrant blue marble teeming with 132 00:06:17.560 --> 00:06:22.120 oceans and forests, and the other being a toxic, crushing, 133 00:06:22.399 --> 00:06:25.079 eight hundred and seventy three degree supercritical inferno. 134 00:06:25.279 --> 00:06:28.720 That divergence is basically the holy grail of planetary science. 135 00:06:28.759 --> 00:06:30.839 I bet it's the ultimate what went wrong. 136 00:06:30.800 --> 00:06:34.360 Scenario exactly, And the general consensus is that you won't 137 00:06:34.360 --> 00:06:37.480 find the answer by looking at anything happening on Venus today. 138 00:06:37.800 --> 00:06:40.720 The surface has been completely scrubbed. To figure out what 139 00:06:40.839 --> 00:06:44.319 went so disastrously wrong, we have to look incredibly far 140 00:06:44.360 --> 00:06:45.279 back in time. 141 00:06:45.160 --> 00:06:46.839 Like to the very beginning of the Solar system. 142 00:06:47.120 --> 00:06:50.160 Yeah, we have to rewind the clock roughly four point 143 00:06:50.240 --> 00:06:55.560 five billion years to the very chaotic, incredibly violent first 144 00:06:55.600 --> 00:06:57.959 fifty million years of our Solar System's existence. 145 00:06:58.120 --> 00:07:02.079 Because the evidence points to a cataclysmic event, doesn't. 146 00:07:01.759 --> 00:07:03.680 It It does. It points to something massive. 147 00:07:03.839 --> 00:07:06.839 We're talking about a massive moon sized object acting as 148 00:07:06.879 --> 00:07:11.079 a cosmic wrecking ball, an event so violently profound that 149 00:07:11.160 --> 00:07:13.800 it permanently altered the planet's fundamental mechanics. 150 00:07:13.879 --> 00:07:15.480 Yeah, it fundamentally broke the planet. 151 00:07:15.600 --> 00:07:18.079 But to even begin to understand how we know this 152 00:07:18.160 --> 00:07:21.600 ancient catastrophe happened. We have to look at the strange, 153 00:07:21.680 --> 00:07:23.720 perplexing way Venus moves through. 154 00:07:23.600 --> 00:07:27.600 Space today, right, because planetary movement is essentially a massive 155 00:07:27.720 --> 00:07:31.600 historical record, the mechanics of how a planet spins, its tilt, 156 00:07:31.680 --> 00:07:34.720 its orbital speed. These aren't just random numbers that it 157 00:07:34.800 --> 00:07:35.399 was born with. 158 00:07:35.480 --> 00:07:37.279 They're like scars exactly. 159 00:07:37.519 --> 00:07:40.399 They are the cumulative physical result of everything that has 160 00:07:40.439 --> 00:07:42.879 ever happened to that body. And Venus moves in a 161 00:07:42.920 --> 00:07:46.040 way that defies almost everything we expect from a rocky planet. 162 00:07:46.240 --> 00:07:48.439 Let's get into the kinematics, you know, the study of 163 00:07:48.480 --> 00:07:52.600 its motion, because the numbers for Venus are just absurd. 164 00:07:52.720 --> 00:07:55.360 I mean, on Earth, we are entirely used to our 165 00:07:55.879 --> 00:07:57.759 rapid counterclockwise rotation. 166 00:07:57.879 --> 00:07:59.759 Sure our standard twenty four hour day. 167 00:08:00.199 --> 00:08:02.319 We spin on our axis once every twenty four hours. 168 00:08:02.399 --> 00:08:05.199 It's a brisk pace. It keeps the weather systems churning. 169 00:08:05.399 --> 00:08:08.600 It gives us our standard day and night cycle. But Venus, 170 00:08:08.680 --> 00:08:11.079 on the other hand, is moving at a pace so 171 00:08:11.160 --> 00:08:12.879 sluggish it almost seems broken. 172 00:08:13.120 --> 00:08:16.879 It's barely moving at all rotationally speaking, and its sluggishness 173 00:08:16.920 --> 00:08:20.040 is really only half the anomaly. The truly baffling part 174 00:08:20.079 --> 00:08:22.040 is that it is spinning in the wrong direction. 175 00:08:21.920 --> 00:08:26.240 Entirely the retrograde spin. Yes, so Earth, Mars, Jupiter, almost 176 00:08:26.279 --> 00:08:30.759 everything in our solar system spins counterclockwise, but Venus spins clockwise. 177 00:08:30.800 --> 00:08:32.960 It's the odd one out, and it does it so 178 00:08:33.200 --> 00:08:37.279 agonizingly slowly that a single rotation on its axis. So 179 00:08:37.559 --> 00:08:40.600 one single Venusian day takes two hundred and forty eight 180 00:08:40.600 --> 00:08:41.559 Earth days to complete. 181 00:08:41.720 --> 00:08:43.559 Just let that number sink in for a second. Two 182 00:08:43.679 --> 00:08:46.200 hundred and forty eight earth days is wild In the 183 00:08:46.240 --> 00:08:49.000 time it takes Venus to spin around just one single time, 184 00:08:49.240 --> 00:08:52.320 Earth has gone through winter, spring, summer, and fall. In fact, 185 00:08:52.399 --> 00:08:54.639 Venus's day is actually longer than it's year. 186 00:08:54.919 --> 00:08:56.919 Wait, its day is longer than it's year. 187 00:08:57.120 --> 00:08:59.759 Yeah, it orbits the Sun in two hundred and twenty 188 00:08:59.759 --> 00:09:02.480 five earth days, but it takes two hundred and forty 189 00:09:02.519 --> 00:09:04.399 eight days to spend on its axis once. 190 00:09:04.639 --> 00:09:08.519 That is just it breaks my brain a little bit 191 00:09:08.519 --> 00:09:10.840 if I'm trying to visualize what that practically means for 192 00:09:10.879 --> 00:09:13.679 the surface. Assuming you could survive the pressure in the heat, 193 00:09:13.840 --> 00:09:17.000 and you could somehow see through the thick sulfuric acid clouds, 194 00:09:17.440 --> 00:09:18.639 what would a day even look like? 195 00:09:18.919 --> 00:09:21.440 Well, the Sun would slowly rise in the west because 196 00:09:21.440 --> 00:09:23.840 of the backward spin right the west, and it would 197 00:09:23.840 --> 00:09:26.120 take more than one hundred earth days just to cross 198 00:09:26.120 --> 00:09:29.000 the sky before finally setting in the east. The sheer 199 00:09:29.200 --> 00:09:31.399 length of the days and nights is terrifying. 200 00:09:31.480 --> 00:09:34.399 So you're just sitting under the blazing sun for over 201 00:09:34.440 --> 00:09:35.240 three months straight. 202 00:09:35.440 --> 00:09:39.639 Yes, it creates a thermal dynamic that is profoundly alien 203 00:09:40.080 --> 00:09:43.559 because when a planet spins that slowly, the side facing 204 00:09:43.600 --> 00:09:46.799 the Sun is subjected to a relentless, unending bombardment of 205 00:09:46.799 --> 00:09:48.559 solar radiation for months on end. 206 00:09:48.639 --> 00:09:50.759 So all that heat just bakes into the atmosphere in 207 00:09:50.799 --> 00:09:51.960 one spot. 208 00:09:51.759 --> 00:09:55.759 Exactly Meanwhile, the dark side is plunged into an equally 209 00:09:55.799 --> 00:10:00.000 long stagnant night. You completely lose all the rapid atmosphere 210 00:10:00.279 --> 00:10:03.720 mixing and the daily thermal relief that a fast spinning 211 00:10:03.759 --> 00:10:05.480 planet like Earth enjoys. 212 00:10:05.600 --> 00:10:08.399 Man, if you're trying to picture how anomalous this backward 213 00:10:08.440 --> 00:10:12.240 spin really is, think of Earth like a beautifully balanced 214 00:10:12.279 --> 00:10:12.960 spinning top. 215 00:10:13.159 --> 00:10:14.320 I like that analogy. 216 00:10:14.480 --> 00:10:16.320 Yeah, So you pull the string and it hits the table, 217 00:10:16.679 --> 00:10:19.480 and it's just humming along, spinning rapidly and smoothly in 218 00:10:19.519 --> 00:10:23.919 a nice counterclockwise direction. It has all this wonderful, stable momentum. 219 00:10:24.120 --> 00:10:27.080 It's happy, right, it's happy. But Venus looks like a 220 00:10:27.120 --> 00:10:30.519 spinning top that was violently kicked, like something hit it 221 00:10:30.559 --> 00:10:34.399 with such immense force that it completely killed its natural 222 00:10:34.480 --> 00:10:38.840 forward momentum, stopped it dead, and left it slowly, drunkenly 223 00:10:38.879 --> 00:10:40.279 spinning in the opposite direction. 224 00:10:40.679 --> 00:10:44.039 That visual is remarkably accurate to the physics involved. Actually, 225 00:10:44.080 --> 00:10:46.440 and the reason planetary scientists have been so obsessed with 226 00:10:46.440 --> 00:10:49.600 this retrograde anomaly for decades is that planets do not 227 00:10:49.679 --> 00:10:52.519 just spontaneously decide to hit the brakes and reverse. 228 00:10:52.200 --> 00:10:53.960 Course because of the laws of physics, right. 229 00:10:53.919 --> 00:10:56.120 Right, The laws of physics strictly forbid it. 230 00:10:56.519 --> 00:11:01.000 Why is that exactly what dictates the defeat vault spin 231 00:11:01.080 --> 00:11:03.399 of a planet in the first place. Why counterclockwise? 232 00:11:03.639 --> 00:11:05.960 It all comes back to how a solar system forms. 233 00:11:06.200 --> 00:11:09.879 If you picture a giant, formless cloud of cold gas 234 00:11:09.879 --> 00:11:14.639 and dust floating in space. Eventually gravity causes this cloud 235 00:11:14.639 --> 00:11:16.039 to collapse in on itself. 236 00:11:16.080 --> 00:11:17.960 Okay, so it starts squishing together. 237 00:11:17.759 --> 00:11:21.120 Right, and as it collapses, it starts to spin, And 238 00:11:21.399 --> 00:11:23.519 just like an ice skater pulling their arms in during 239 00:11:23.559 --> 00:11:26.519 a spin, the more it collapses the faster it spins, 240 00:11:26.879 --> 00:11:31.279 eventually flattening out into a massive swirling disk. We call 241 00:11:31.279 --> 00:11:32.919 it the protoplanetary disk, like. 242 00:11:32.879 --> 00:11:34.120 A giant cosmic pizza. 243 00:11:34.159 --> 00:11:37.399 Do yes, exactly. The star forms in the center and 244 00:11:37.440 --> 00:11:40.759 the planets form from the leftover dust swirling around it 245 00:11:40.799 --> 00:11:41.360 in the disk. 246 00:11:41.559 --> 00:11:44.399 So, because the entire massive dust cloud was already spinning 247 00:11:44.399 --> 00:11:48.639 in one direction, let's say counterclockwise, everything that forms out 248 00:11:48.639 --> 00:11:51.240 of that dust should also be spinning counterclockwise. 249 00:11:51.320 --> 00:11:54.960 Precisely. It is called the conservation of angular momentum. The 250 00:11:55.039 --> 00:11:58.320 planets are basically inheriting the spin of the original dust cloud. 251 00:11:58.399 --> 00:12:00.200 They don't have a choice, no choice at all. 252 00:12:00.240 --> 00:12:03.200 So for a planet the size and mass of Venus 253 00:12:03.240 --> 00:12:07.000 to completely violate that inherited momentum to just stop and 254 00:12:07.039 --> 00:12:11.879 spin backward, an external force of unimaginable power must have intervened. 255 00:12:12.200 --> 00:12:14.639 It is literally the only way the math works. 256 00:12:14.759 --> 00:12:18.000 You need a massive energetic event to essentially grab the 257 00:12:18.039 --> 00:12:21.320 planet and physically force it into reverse. You do, which 258 00:12:21.320 --> 00:12:23.960 is where the work of Cedric Gilman and his team 259 00:12:24.000 --> 00:12:27.679 at ETH Zurich comes in. They are planetary scientists who 260 00:12:27.759 --> 00:12:32.159 recently presented some really groundbreaking models at the European Geoscience's 261 00:12:32.440 --> 00:12:35.679 Union General Assembly, and they basically took on the task 262 00:12:35.720 --> 00:12:38.240 of figuring out exactly what kind of force it takes 263 00:12:38.279 --> 00:12:39.120 to stop a world. 264 00:12:39.320 --> 00:12:42.440 And their approach to solving this mystery is fascinating because 265 00:12:42.519 --> 00:12:44.440 they essentially had to treat the Solar System like a 266 00:12:44.480 --> 00:12:47.000 four point five billion year old crime scene. 267 00:12:47.080 --> 00:12:49.279 Right, you can't just go dust for prints exactly. 268 00:12:49.360 --> 00:12:51.799 They couldn't just guess what happened. They had to work backward. 269 00:12:51.960 --> 00:12:56.080 They started with the slow rotating observation, so the two 270 00:12:56.159 --> 00:12:58.559 hundred and forty eight day backward crawl we see today, 271 00:12:59.200 --> 00:13:02.960 and they fed at endpoint into highly advanced computer simulations. 272 00:13:03.000 --> 00:13:04.879 So they're reverse engineering the apocalypse. 273 00:13:05.159 --> 00:13:08.600 Yeah. They use these models to test millions of permutations, 274 00:13:08.639 --> 00:13:11.120 just trying to find the exact initial conditions that could 275 00:13:11.120 --> 00:13:12.440 produce the venus we see now. 276 00:13:12.480 --> 00:13:15.519 They're essentially running the physics engine of the universe in reverse. 277 00:13:15.559 --> 00:13:20.279 They're asking what happens when you throw a ridiculously large 278 00:13:20.360 --> 00:13:22.519 rock at another ridiculously large rock. 279 00:13:22.559 --> 00:13:25.360 And not just any rock. The simulations revealed that to 280 00:13:25.679 --> 00:13:29.120 alter the momentum of a planet that massive, you need 281 00:13:29.159 --> 00:13:34.080 an impactor roughly one tenth the mass of Venus itself. 282 00:13:33.919 --> 00:13:36.639 One tenth of the entire planet's mass. To give that 283 00:13:36.720 --> 00:13:38.960 some scale for you listening, we aren't talking about a 284 00:13:38.960 --> 00:13:41.559 standard asteroid here. We aren't talking about the six mile 285 00:13:41.600 --> 00:13:43.559 wide Metia that wiped out the dinosaurs. 286 00:13:43.600 --> 00:13:45.279 No, that would barely be a scratch, right. 287 00:13:45.559 --> 00:13:47.879 An object that is one tenth the mass of Earth 288 00:13:48.120 --> 00:13:51.240 or Venus is roughly the size of our moon. You 289 00:13:51.279 --> 00:13:54.960 have a solid, rocky, fully formed planetary body thousands of 290 00:13:54.960 --> 00:13:58.080 miles across, hurtling through the dark void of the early 291 00:13:58.120 --> 00:13:58.840 Solar System. 292 00:13:58.919 --> 00:14:00.879 It is terrifying amount mass, just. 293 00:14:00.840 --> 00:14:03.639 A rogue moon on a collision course exactly. 294 00:14:04.039 --> 00:14:06.960 But the model showed that the mass alone wasn't enough 295 00:14:07.000 --> 00:14:09.799 to solve the mystery. The geometry of the collision was 296 00:14:09.919 --> 00:14:14.159 absolutely critical, because if that moon sized object had struck 297 00:14:14.279 --> 00:14:17.759 Venus dead center like a perfect bullseye, it wouldn't have 298 00:14:17.799 --> 00:14:19.159 caused the retrograde spin. 299 00:14:19.279 --> 00:14:22.120 Wait, really, why not? Wouldn't a direct hit transfer the 300 00:14:22.120 --> 00:14:23.200 most energy, Well, it. 301 00:14:23.120 --> 00:14:26.519 Transfers the most energy into the core. Yes, if you 302 00:14:26.559 --> 00:14:29.799 have a dead center impact, the kinetic energy goes straight inward, 303 00:14:29.879 --> 00:14:32.799 driving a massive shockwave through the center of the planet. Okay, 304 00:14:32.919 --> 00:14:35.240 but it doesn't give you leverage. If you want to 305 00:14:35.320 --> 00:14:39.159 change how a massive sphere spins, you need torque. You 306 00:14:39.200 --> 00:14:41.639 need to hit it on the edge. So the models 307 00:14:41.679 --> 00:14:44.279 concluded that the impactor had to strike Venus at a 308 00:14:44.399 --> 00:14:47.279 very high angle. It had to be a tangential off 309 00:14:47.360 --> 00:14:48.639 center grazing blow. 310 00:14:48.799 --> 00:14:50.679 So instead of a hit on car crash, it's more 311 00:14:50.720 --> 00:14:53.080 like a side swipe, but at tens of thousands of 312 00:14:53.080 --> 00:14:53.720 miles per hour. 313 00:14:53.840 --> 00:14:57.679 Precisely, that glancing blow acts like a giant cosmic hand. 314 00:14:57.840 --> 00:15:00.320 It grabs the edge of the rapidly spinning planet and 315 00:15:00.519 --> 00:15:02.080 violently wrenches it the other way. 316 00:15:02.240 --> 00:15:06.480 Yes, the models show that this specific type of tangential 317 00:15:06.519 --> 00:15:11.159 strike could take a young, healthy, rapidly spinning Venus, slam 318 00:15:11.200 --> 00:15:15.039 the brakes on its rotation and induce a faster backward spin. 319 00:15:15.039 --> 00:15:16.799 And then over time it slowed down. 320 00:15:16.840 --> 00:15:21.039 Exactly over billions of years of gravitational friction, that initial 321 00:15:21.080 --> 00:15:24.919 backward spin slowly decayed into the sluggish two hundred and 322 00:15:24.919 --> 00:15:26.679 forty eight day crawl we see today. 323 00:15:26.759 --> 00:15:29.840 Okay, but I'm struggling with the mechanics of survivability here, 324 00:15:30.039 --> 00:15:32.879 because if an object the size of the Moon, traveling 325 00:15:32.879 --> 00:15:36.399 at thirty or forty kilometers a second, slams into a planet, 326 00:15:36.799 --> 00:15:40.200 wouldn't the planet just cease to exist? You'd think so, right, 327 00:15:40.360 --> 00:15:42.639 I mean, how does a rocky sphere take a punch 328 00:15:42.679 --> 00:15:45.279 of that magnitude and not just shatter into a billion 329 00:15:45.279 --> 00:15:47.919 pieces of gravel floating in orbit, like the Death Star 330 00:15:47.960 --> 00:15:48.840 exploding or something. 331 00:15:48.919 --> 00:15:51.919 It's a completely natural question, because our daily intuition tells 332 00:15:52.000 --> 00:15:53.919 us that a high speed collision of that size should 333 00:15:53.960 --> 00:15:57.120 be totally destructive. But this is where planetary physics really 334 00:15:57.159 --> 00:16:00.840 diverges from our everyday experience. It all comes down to 335 00:16:00.919 --> 00:16:05.440 a concept called gravitational binding energy. When a planet gets 336 00:16:05.480 --> 00:16:07.879 to be the size of Venus, its gravity is so 337 00:16:08.039 --> 00:16:11.440 intensely powerful that it holds its own mass together with 338 00:16:11.600 --> 00:16:12.919 incredible force, so. 339 00:16:12.840 --> 00:16:14.679 It's basically squeezing itself into a ball. 340 00:16:14.840 --> 00:16:19.480 Yes, To permanently shatter a planet that big, to actually 341 00:16:19.519 --> 00:16:22.200 blast its pieces so far apart that they don't just 342 00:16:22.240 --> 00:16:26.000 immediately fall back together, requires an energy threshold that is 343 00:16:26.080 --> 00:16:29.759 truly astronomical, much more than even a moon sized impactor 344 00:16:29.759 --> 00:16:30.240 can deliver. 345 00:16:30.360 --> 00:16:32.720 So even if it fractures into pieces, the gravity just 346 00:16:32.759 --> 00:16:35.480 pulls all the pieces right back into a sphere exactly. 347 00:16:35.720 --> 00:16:39.279 But furthermore, the tangential angle we talked about actually saves 348 00:16:39.279 --> 00:16:40.919 the planet from total obliteration. 349 00:16:41.200 --> 00:16:43.799 Oh, because it wasn't a dead center hit right in. 350 00:16:43.759 --> 00:16:47.039 A head on collision. All that energy plunges directly into 351 00:16:47.039 --> 00:16:49.679 the core, which can literally unbind the planet and blow 352 00:16:49.720 --> 00:16:52.919 it apart, but with a high angle, grazing blow. A 353 00:16:53.039 --> 00:16:56.519 vast amount of the impactor's kinetic energy is spent on friction, 354 00:16:56.919 --> 00:16:59.679 on shearing off the outer layers, and on altering the 355 00:16:59.679 --> 00:17:01.240 angle momentum. 356 00:17:00.799 --> 00:17:03.679 So it bleeds off the energy on the surface exactly. 357 00:17:04.160 --> 00:17:08.039 The impactor itself might be completely vaporized and its material 358 00:17:08.119 --> 00:17:11.279 merged with the planet's outer crust, but the host planet's 359 00:17:11.359 --> 00:17:14.119 core remains intact. It survives structurally. 360 00:17:14.599 --> 00:17:18.000 That paints just a wild picture. The planet takes the hit, 361 00:17:18.480 --> 00:17:21.759 the moon sized rock is pulverized and absorbed into the crust, 362 00:17:22.240 --> 00:17:25.960 and Venus remains a single intact. 363 00:17:25.480 --> 00:17:27.599 Sphere, battered but intact. 364 00:17:27.839 --> 00:17:29.960 But you know, just because it stayed in one piece 365 00:17:29.960 --> 00:17:33.480 doesn't mean it walked away unharmed. Surviving the kinetic impact 366 00:17:33.559 --> 00:17:36.279 was just the beginning, because the physical consequences on the 367 00:17:36.279 --> 00:17:37.640 interior of the planet were. 368 00:17:37.559 --> 00:17:42.279 Apocalyptic, beyond apocalyptic, really, because when an object that large 369 00:17:42.319 --> 00:17:45.640 strikes a planet, the laws of thermodynamics take over immediately, 370 00:17:45.720 --> 00:17:47.759 right The energy has go somewhere exactly. You have a 371 00:17:47.799 --> 00:17:50.599 staggering amount of kinetic energy the sheer motion of a 372 00:17:50.640 --> 00:17:54.440 moon sized rock traveling at cosmic speeds. That energy cannot 373 00:17:54.440 --> 00:17:57.119 just vanish when the rock stops. It has to convert 374 00:17:57.160 --> 00:18:00.559 into another form, and in a high speed planetary collision, 375 00:18:00.880 --> 00:18:03.480 kinetic energy instantly converts into heat. 376 00:18:03.680 --> 00:18:06.039 And we are not talking about a modest heat wave here, 377 00:18:06.079 --> 00:18:08.279 not at all. We are talking about the surface of 378 00:18:08.319 --> 00:18:12.680 the planet literally melting into a global ocean of glowing rock. 379 00:18:13.359 --> 00:18:16.799 The simulations dive deep into the immediate aftermath of this collision, 380 00:18:16.960 --> 00:18:19.559 and depending on the exact speed and angle, the heat 381 00:18:19.559 --> 00:18:21.119 transformation is unimaginable. 382 00:18:21.160 --> 00:18:23.799 The models run a whole spectrum of scenarios. On the 383 00:18:23.839 --> 00:18:26.200 mild end of the collision parameters, if you can even 384 00:18:26.240 --> 00:18:29.160 call it mild, you still get a shallow melt layer 385 00:18:29.240 --> 00:18:32.200 covering the entire globe, maybe one hundred kilometers thick. 386 00:18:32.279 --> 00:18:34.119 Wait, one hundred kilometers. 387 00:18:33.640 --> 00:18:37.400 Yeah, so that is sixty two miles deep of pure, 388 00:18:38.039 --> 00:18:42.079 sloshing liquid magma coating every single inch of the planet. 389 00:18:42.200 --> 00:18:44.599 Sixty two miles deep of lava is the mild. 390 00:18:44.440 --> 00:18:48.440 Scenario, right, that's if it barely clips it. The extreme scenario, 391 00:18:48.839 --> 00:18:51.559 which the researcher's note is highly likely given the immense 392 00:18:51.680 --> 00:18:54.920 energy required to actually reverse the planet's rotation, is that 393 00:18:54.960 --> 00:18:58.720 the kinetic heat transfer melted ninety nine percent of Venus's mantle. 394 00:18:58.440 --> 00:19:01.880 Ninety nine percent, yes mantle being for context, the vast 395 00:19:02.039 --> 00:19:05.039 rocky interior of the planet that sits right between the 396 00:19:05.119 --> 00:19:07.640 dense iron core in the center and the thin outer 397 00:19:07.720 --> 00:19:10.119 crust on the surface. It is the bulk of the 398 00:19:10.160 --> 00:19:10.920 planet's volume. 399 00:19:11.000 --> 00:19:13.079 It's almost the entire planet, and. 400 00:19:12.960 --> 00:19:15.680 The model suggests that ninety nine percent of that solid 401 00:19:15.759 --> 00:19:19.839