WEBVTT 1 00:00:03.439 --> 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 --> 00:00:26.719 slumber under the night sky. 7 00:00:27.000 --> 00:00:29.120 Every single star you see when you look up at 8 00:00:29.120 --> 00:00:32.000 the night sky is well, it's essentially a survivor. 9 00:00:32.119 --> 00:00:34.280 Oh absolutely, that is a great way to put. 10 00:00:34.159 --> 00:00:37.560 It right, because it is the glowing, burning byproduct of 11 00:00:37.600 --> 00:00:43.399 this completely violent, chaotic and just incredibly destructive factory that 12 00:00:43.960 --> 00:00:46.359 likely blew itself to pieces millions of years ago. 13 00:00:46.520 --> 00:00:48.320 Yeah, I think people really lose sight of that. 14 00:00:48.759 --> 00:00:51.399 I want you to just imagine stepping outside your house tonight, 15 00:00:51.520 --> 00:00:55.399 or you know, just standing outside on a perfectly clear, crisp, 16 00:00:55.759 --> 00:00:56.640 moonless night. 17 00:00:56.799 --> 00:00:59.280 Away from all the city lights, hopefully exactly. 18 00:00:59.640 --> 00:01:02.200 You look up and the canopy is just scattered with 19 00:01:02.240 --> 00:01:05.319 these brilliant points of light, and it feels quiet. 20 00:01:05.439 --> 00:01:06.560 It feels very stable. 21 00:01:06.680 --> 00:01:10.439 Yeah right, it feels serene. But that stability is a 22 00:01:10.480 --> 00:01:12.079 profound optical illusion. 23 00:01:12.200 --> 00:01:14.959 It really is the visible universe is effectively just the 24 00:01:15.000 --> 00:01:16.159 exhaust of the system. 25 00:01:16.400 --> 00:01:17.640 The exhaust. I love that. 26 00:01:17.879 --> 00:01:20.319 I mean, it's true. The glowing stars the things that 27 00:01:20.359 --> 00:01:24.920 have captivated human attention for millennia. They represent the absolute 28 00:01:24.959 --> 00:01:29.760 final stage of a vastly longer, darker, and infinitely more 29 00:01:29.799 --> 00:01:30.840 turbulent process. 30 00:01:30.920 --> 00:01:32.840 So if you only look at the stars. 31 00:01:32.719 --> 00:01:35.640 You're entirely missing the actual story of how the universe 32 00:01:35.640 --> 00:01:36.920 builds itself, which. 33 00:01:36.760 --> 00:01:40.159 Is exactly why we are completely shifting our perspective today. 34 00:01:40.159 --> 00:01:43.599 We are going to plunge into the absolute coldest, darkest, 35 00:01:43.680 --> 00:01:48.079 and literally the most massive structures that exist in the cosmos. 36 00:01:47.959 --> 00:01:50.840 The giant molecular clouds or GMCs. 37 00:01:50.959 --> 00:01:53.840 GMCs. Yeah, our goal here is to figure out the 38 00:01:53.879 --> 00:01:57.560 actual mechanics, how does the universe take a vast region 39 00:01:57.959 --> 00:02:03.159 of cold, dead, seemingly empty gas and somehow crush it 40 00:02:03.239 --> 00:02:06.200 down until it ignites into a burning fusion engine. 41 00:02:06.439 --> 00:02:09.000 And to really understand that we can't just poke around 42 00:02:09.000 --> 00:02:10.240 our own local neighborhood. 43 00:02:10.360 --> 00:02:12.520 Right, We're going big. We're going to look fifty to 44 00:02:12.560 --> 00:02:15.560 sixty million light years away at an entire galaxy is 45 00:02:15.599 --> 00:02:18.719 worth of these factories, just to see the actual blueprints of. 46 00:02:18.719 --> 00:02:21.280 Creation, because it is the only way to really understand 47 00:02:21.280 --> 00:02:23.759 the fundamental life cycle of a galaxy. I mean, a 48 00:02:23.800 --> 00:02:27.039 giant molecular cloud isn't just the birthplace of a single. 49 00:02:26.719 --> 00:02:29.400 Star or even a single cluster of stars, right exactly. 50 00:02:29.520 --> 00:02:33.120 The sheer, scale, the mass, the mechanics of these structures. 51 00:02:33.479 --> 00:02:36.280 They dictate everything about a galaxy. They determine how it 52 00:02:36.360 --> 00:02:39.759 changes shape over billions of years, how it breathe, and. 53 00:02:39.800 --> 00:02:43.000 Ultimately what kinds of chemical elements are even available to 54 00:02:43.080 --> 00:02:43.840 forge planets. 55 00:02:43.919 --> 00:02:46.039 Yes, and by extension biology itself. 56 00:02:46.159 --> 00:02:49.199 But the scale, the scale is the part that I 57 00:02:49.199 --> 00:02:52.199 think breaks the human brain first, because we use the 58 00:02:52.199 --> 00:02:53.840 word cloud in everyday life. 59 00:02:54.039 --> 00:02:57.000 Right, you look out the window on a cloudy day, exactly. 60 00:02:56.639 --> 00:02:59.759 You see these fluffy white collections of water vapor suspended 61 00:02:59.680 --> 00:03:03.360 a few miles above your head. But when astrophysicists use 62 00:03:03.400 --> 00:03:05.800 the term giant molecular cloud. 63 00:03:06.520 --> 00:03:09.280 They are talking about something so immensely huge that our 64 00:03:09.439 --> 00:03:12.919 entire solar system wouldn't even register as a single speck 65 00:03:12.960 --> 00:03:14.199 of dust inside it. 66 00:03:14.240 --> 00:03:17.120 A speck of dust. Yeah, So before we even get 67 00:03:17.159 --> 00:03:19.719 to the specific galaxy we are mapping out, we need 68 00:03:19.759 --> 00:03:22.080 to understand the anatomy of the beast what actually is 69 00:03:22.120 --> 00:03:22.759 a GMC. 70 00:03:23.280 --> 00:03:26.000 Well, to define a giant molecular cloud, you have to 71 00:03:26.039 --> 00:03:28.840 first look at the baseline environment of space. Okay, the 72 00:03:28.879 --> 00:03:32.199 interstellar medium, right, the space between the stars is not 73 00:03:32.360 --> 00:03:35.599 an absolute perfect vacuum. It is filled with a highly 74 00:03:35.639 --> 00:03:37.719 diffuse mixture of gas and dust. 75 00:03:37.960 --> 00:03:40.520 But out in the open that gas is relatively warm. 76 00:03:40.360 --> 00:03:44.719 Right, Yeah, it's ionized by starlight and it's spread incredibly thin. 77 00:03:45.360 --> 00:03:48.879 But a giant molecular cloud forms when, through a variety 78 00:03:48.919 --> 00:03:52.400 of different galactic processes, vast amounts of that gas just 79 00:03:52.439 --> 00:03:53.439 gets swept up together. 80 00:03:53.599 --> 00:03:55.240 It starts to clup up exactly. 81 00:03:55.680 --> 00:03:59.319 Its density increases dramatically, and the sheer volume of it 82 00:03:59.520 --> 00:04:02.400 shields is the inside from the radiation of the rest 83 00:04:02.439 --> 00:04:03.520 of the galaxy. 84 00:04:03.159 --> 00:04:04.560 Like it's building its own shade. 85 00:04:04.759 --> 00:04:06.680 That's a good way to look at it. And because 86 00:04:06.719 --> 00:04:09.000 it is shielded, it can finally cool down. And when 87 00:04:09.000 --> 00:04:11.120 I say cool down, I mean it reaches temperatures just 88 00:04:11.280 --> 00:04:13.479 barely hovering above absolute zero. 89 00:04:13.599 --> 00:04:15.240 Okay, Wait, let's put a hard number on that for 90 00:04:15.280 --> 00:04:17.839 anyone listening in their car or at the gym right now. 91 00:04:18.920 --> 00:04:22.560 Because cold is relative, how cold is this. 92 00:04:22.600 --> 00:04:25.759 Environment we are talking about internal temperatures of around ten 93 00:04:25.800 --> 00:04:26.519 to twenty. 94 00:04:26.319 --> 00:04:28.560 Kelvin, which in fahrenheit is what in. 95 00:04:28.519 --> 00:04:32.519 Fahrenheit that is roughly minus four hundred and forty degrees. 96 00:04:32.120 --> 00:04:34.079 Minus four hundred and forty degrees. Wow. 97 00:04:34.240 --> 00:04:36.759 Yeah, And to give you some context for that, the 98 00:04:36.800 --> 00:04:40.560 ambient background temperature of the entire universe, the leftover heat 99 00:04:40.600 --> 00:04:43.519 from the Big Bang itself, is about two point seven kelvin. 100 00:04:43.759 --> 00:04:46.720 So these clouds are just a tiny, tiny fraction of 101 00:04:46.720 --> 00:04:49.480 a degree warmer than the fundamental floor. 102 00:04:49.199 --> 00:04:52.519 Of physics, exactly, just barely warmer than the background of 103 00:04:52.519 --> 00:04:53.079 the universe. 104 00:04:53.079 --> 00:04:55.600 At minus four hundred and forty degrees. Matter has to 105 00:04:55.600 --> 00:04:58.000 behave completely differently, right, I mean everything just stops. 106 00:04:58.040 --> 00:05:01.560 The atomic behavior changes fundamentally. Yes. In the warmer and 107 00:05:01.639 --> 00:05:06.560 more diffuse interstellar medium, hydrogen exists mostly as single unbound 108 00:05:06.560 --> 00:05:08.040 atoms just bouncing. 109 00:05:07.639 --> 00:05:10.639 Around because they have too much kinetic energy to stick together, right. 110 00:05:10.480 --> 00:05:13.720 They just ricochet off each other. But inside these dark, 111 00:05:14.000 --> 00:05:18.639 incredibly cold clouds, the hydrogen atoms lose that kinetic energy. 112 00:05:18.920 --> 00:05:22.040 They slow down, they get sluggish, they get very sluggish. 113 00:05:22.160 --> 00:05:25.959 They meet and they bond together to form molecular hydrogen, 114 00:05:26.199 --> 00:05:31.000 which is H two two hydrogen atoms sharing their electrons. 115 00:05:30.639 --> 00:05:34.759 And that chemical transition is the defining characteristic of these structures. Right, 116 00:05:34.800 --> 00:05:37.120 That's why we specifically call them molecular clouds. 117 00:05:37.160 --> 00:05:39.120 Precisely, It's all about the molecules. 118 00:05:39.120 --> 00:05:41.879 Okay, so we have this freezing dark pocket of paired 119 00:05:41.959 --> 00:05:45.399 up hydrogen. But let's talk size. We throw around astronomical 120 00:05:45.480 --> 00:05:47.120 terms a lot, but I really want to ground this. 121 00:05:47.959 --> 00:05:49.959 How big is a typical GMC? 122 00:05:50.360 --> 00:05:54.680 A standard giant molecular cloud will span anywhere from tens 123 00:05:54.720 --> 00:05:58.160 to hundreds of light years across or in the units 124 00:05:58.160 --> 00:06:02.279 astronomers actually prefer to use tends to hundreds of parsecs. 125 00:06:02.560 --> 00:06:05.519 Okay, let's quickly define the parsec because it's one of 126 00:06:05.519 --> 00:06:08.279 those words that sounds like pure science fiction mostly beza 127 00:06:08.319 --> 00:06:08.759 Han solo. 128 00:06:08.839 --> 00:06:12.600 Let's be real, right, the infamous Kessel run, which as 129 00:06:12.600 --> 00:06:15.600 a quick aside, was always a unit of distance. 130 00:06:15.240 --> 00:06:18.720 Not time exactly. Take that Star Wars, But what is 131 00:06:18.839 --> 00:06:20.079 a parsk in reality? 132 00:06:20.199 --> 00:06:23.240 In reality, a parsec is simply a unit of distance 133 00:06:23.279 --> 00:06:26.319 equivalent to about three point twenty six light years or 134 00:06:26.600 --> 00:06:28.560 roughly nineteen trillion. 135 00:06:28.199 --> 00:06:31.000 Mile nineteen trillion miles for one parsek. 136 00:06:31.199 --> 00:06:34.399 Yes, it is derived from a geometric measurement called parallax. 137 00:06:34.759 --> 00:06:37.959 That's how astronomers measure the distance to relatively nearby stars 138 00:06:38.240 --> 00:06:40.560 by looking at how they shift against the background as 139 00:06:40.600 --> 00:06:41.879 the Earth orbits the Sun. 140 00:06:42.079 --> 00:06:43.879 Right like holding your thumb up and closing one eye 141 00:06:43.920 --> 00:06:44.120 then the. 142 00:06:44.160 --> 00:06:46.959 Other, exactly that principle, just on a solar system scale. 143 00:06:47.040 --> 00:06:49.879 So when an astronomer says a cloud is thirty parsecs across, 144 00:06:49.920 --> 00:06:51.720 they mean it is about one hundred light years from 145 00:06:51.800 --> 00:06:52.279 end to end. 146 00:06:52.439 --> 00:06:54.040 Okay, I want to put one hundred light years in 147 00:06:54.079 --> 00:06:58.959 perspective for the listener. The distance from our Sun to 148 00:06:59.240 --> 00:07:04.959 the absolute closest neighboring star, Proxima Centauri, is about four light. 149 00:07:04.839 --> 00:07:05.920 Years, just over four. 150 00:07:06.000 --> 00:07:09.560 Yes, and the fastest spacecraft humanity has ever built would 151 00:07:09.600 --> 00:07:12.800 still take tens of thousands of years to make that 152 00:07:12.959 --> 00:07:14.040 single four light. 153 00:07:13.959 --> 00:07:16.240 Year trip, a staggeringly long time. 154 00:07:16.480 --> 00:07:18.360 And you were saying one of these clouds is one 155 00:07:18.399 --> 00:07:21.839 hundred light years across, I mean you could stack thousands 156 00:07:21.879 --> 00:07:24.439 of our solar systems end to end and they would 157 00:07:24.480 --> 00:07:25.279 just be swallowed up in the. 158 00:07:25.319 --> 00:07:28.360 Dark, swallowed up completely. You wouldn't even notice them. And 159 00:07:28.399 --> 00:07:32.439 with that kind of physical volume comes an almost incomprehensible 160 00:07:32.480 --> 00:07:33.360 amount of mass. 161 00:07:33.519 --> 00:07:34.720 How much mass are we talking? 162 00:07:34.839 --> 00:07:38.639 A typical giant molecular cloud contains the equivalent mass of 163 00:07:38.839 --> 00:07:41.839 hundreds of thousands, and sometimes well over a million of 164 00:07:41.920 --> 00:07:42.920 our suns. 165 00:07:42.639 --> 00:07:44.480 A million suns worth of raw material. 166 00:07:44.639 --> 00:07:48.680 Yes, a million suns. And while the vast overwhelming majority 167 00:07:48.680 --> 00:07:51.199 of that mass is the molecular hydrogen we just discussed, 168 00:07:51.560 --> 00:07:54.519 the cloud is definitely not pure. It's got some seasoning 169 00:07:54.519 --> 00:07:57.399 in it, a lot of seasoning. It is laced with 170 00:07:57.480 --> 00:08:02.319 an incredibly important mixture of other opponents. Roughly one percent 171 00:08:02.600 --> 00:08:05.600 of the cloud's mass is made up of interstellar dust. 172 00:08:05.800 --> 00:08:08.000 When you say dust, you mean like the stuff on 173 00:08:08.040 --> 00:08:08.680 my bookshelf. 174 00:08:08.920 --> 00:08:13.800 More like microscopic grains of silicates and carbonaceous material. Think 175 00:08:13.879 --> 00:08:16.399 soot and sand, but at a microscopic level. 176 00:08:16.480 --> 00:08:17.879 Okay, soot in sand, got it. 177 00:08:18.000 --> 00:08:21.519 And then there are trece amounts of other gases too, ammonia, 178 00:08:21.560 --> 00:08:26.519 carbon monoxide, and even highly complex organic molecules. They are 179 00:08:26.560 --> 00:08:28.839 really the ultimate cosmic reservoir. 180 00:08:28.959 --> 00:08:31.240 So we have a reservoir of a million suns. It's 181 00:08:31.240 --> 00:08:33.559 one hundred light years wide, it is full of the 182 00:08:33.679 --> 00:08:37.440 exact raw materials needed to build solar systems and it 183 00:08:37.480 --> 00:08:39.639 is hanging right over our heads in our own galaxy. 184 00:08:39.840 --> 00:08:41.720 Oh, absolutely all over the galaxy, and. 185 00:08:41.679 --> 00:08:44.320 In every other galaxy too. So you would think astronomers 186 00:08:44.320 --> 00:08:46.360 could just point a telescope at the sky and see 187 00:08:46.360 --> 00:08:49.080 these massive things literally everywhere. You would think so, But 188 00:08:49.120 --> 00:08:52.200 that leads to one of the most frustrating paradoxes in astrophysics. 189 00:08:52.840 --> 00:08:55.080 These behemoths are practically invisible. 190 00:08:55.480 --> 00:08:59.080 It really is the great irony of star formation. The 191 00:08:59.240 --> 00:09:03.799 raw fuel that creates the brightest, most intensely luminous objects 192 00:09:03.840 --> 00:09:09.120 in the universe is fundamentally undetectable to standard observational tools. 193 00:09:09.279 --> 00:09:11.879 It's like they're cloaked. Why is that right? Because it's 194 00:09:11.919 --> 00:09:14.320 just two of the exact same hydrogen atoms. 195 00:09:14.320 --> 00:09:16.639 So when it rotates in the freezing cold of a 196 00:09:16.720 --> 00:09:21.440 dark cloud, it doesn't emit any easily detectable radiation at all. 197 00:09:21.519 --> 00:09:23.879 It is completely silent to our instruments. 198 00:09:24.080 --> 00:09:27.240 It's totally dark. You know. To me, it's like trying 199 00:09:27.279 --> 00:09:30.240 to watch a perfectly clear, rushing river at night. 200 00:09:30.279 --> 00:09:31.519 That's a really good analogy. 201 00:09:31.759 --> 00:09:34.000 You know, the river is there, you know, it spans 202 00:09:34.000 --> 00:09:36.720 for miles and millions of gallons of water are churning 203 00:09:36.759 --> 00:09:39.799 and carrying massive amounts of force. But because the water 204 00:09:39.919 --> 00:09:43.679 is totally transparent and there's no light bouncing off of it, 205 00:09:44.039 --> 00:09:46.320 you stand on the bank and you are just totally blind. 206 00:09:46.399 --> 00:09:48.759 You can't see the currents, you can't map the flow. 207 00:09:49.080 --> 00:09:51.399 Right, So if you are a scientist trying to map 208 00:09:51.480 --> 00:09:54.519 that river, you have to get creative. You essentially have 209 00:09:54.559 --> 00:09:58.919 to drop a non toxic fluorescent dye into the water upstream. Exactly, 210 00:09:59.000 --> 00:10:00.960 you can't see the water it's but you can track 211 00:10:01.000 --> 00:10:04.159 the glowing dye, and by mapping the dye, you map 212 00:10:04.200 --> 00:10:04.559 the river. 213 00:10:04.759 --> 00:10:10.080 That river analogy captures the exact methodology of molecular astrophysics perfectly. 214 00:10:10.440 --> 00:10:13.759 We literally cannot see the molecular hydrogen water. We are 215 00:10:13.799 --> 00:10:15.360 totally blind to the H two. 216 00:10:15.480 --> 00:10:16.720 So we need a cosmic dye. 217 00:10:16.840 --> 00:10:17.080 Yes. 218 00:10:17.600 --> 00:10:21.440 We must rely on a tracer, and the most ubiquitous, 219 00:10:21.559 --> 00:10:25.960 reliable dye available in these giant molecular clouds is carbon 220 00:10:26.000 --> 00:10:27.360 monoxide COO. 221 00:10:27.639 --> 00:10:29.919 Wait, like the exact same carbon monoxide that comes out 222 00:10:29.960 --> 00:10:33.000 of a car exhaust or a faulty furnace. 223 00:10:32.799 --> 00:10:36.240 The very same molecule yes. Now, compared to the vast 224 00:10:36.360 --> 00:10:39.720 ocean of hydrogen, carbon monoxide is barely a drop in 225 00:10:39.759 --> 00:10:42.480 the bucket. For every single molecule of COEO, there are 226 00:10:42.559 --> 00:10:44.840 roughly ten thousand molecules of. 227 00:10:44.840 --> 00:10:47.240 Hydrogen, so it's a very very faint, dye. 228 00:10:47.120 --> 00:10:50.799 Very trace. But carbon monoxide has the one crucial feature 229 00:10:50.879 --> 00:10:53.480 that hydrogen lacks. It is asymmetric. 230 00:10:53.679 --> 00:10:56.399 Ah, It's made of one carbon in one oxygen exactly. 231 00:10:56.559 --> 00:11:00.159 Oxygen is more electronegative than carbon, which means it pull 232 00:11:00.240 --> 00:11:02.120 the shared electrons slightly toward itself. 233 00:11:02.159 --> 00:11:03.960 It has the imbalance. It has the antenna. 234 00:11:03.720 --> 00:11:07.320 Precisely because it has that slight electrical imbalance the dipole moment. 235 00:11:07.360 --> 00:11:09.960 When a carbon monoxide molecule gets bumped by a neighboring 236 00:11:10.039 --> 00:11:11.279 hydrogen molecule. 237 00:11:10.919 --> 00:11:12.320 It starts to spin and it hums. 238 00:11:12.559 --> 00:11:15.000 Yes, as it spins, it emits a very specific, very 239 00:11:15.039 --> 00:11:20.399 distinct radiofrequency. Specifically, it emits at millimeter and submillimeter wavelengths. 240 00:11:19.960 --> 00:11:22.120 Even at minus four hundred and forty degrees. 241 00:11:22.080 --> 00:11:25.600 Even at ten kelvin in the absolute freezing depths of 242 00:11:25.639 --> 00:11:29.360 the cloud, there is just enough ambient thermal energy from 243 00:11:29.399 --> 00:11:33.080 those collisions to keep the carbon monoxide rotating and humming. 244 00:11:33.320 --> 00:11:37.279 So this whole vast invisible cloud of hydrogen is basically 245 00:11:37.279 --> 00:11:39.840 singing to us, but we can only hear it through 246 00:11:39.879 --> 00:11:41.879 the voice of the trace carbon monoxide. 247 00:11:41.919 --> 00:11:45.240 That's beautifully put Yes, where you find carbon monoxide emitting 248 00:11:45.240 --> 00:11:48.559 these millimeter waves, you are virtually guaranteed to be looking 249 00:11:48.639 --> 00:11:50.960 at a dense pocket of molecular hydrogen. 250 00:11:51.120 --> 00:11:54.000 By tuning our instruments to the exact frequency of that 251 00:11:54.080 --> 00:11:57.200 co hum, we can map the entire invisible river. 252 00:11:57.320 --> 00:11:59.039 But as you might guess, there is a catch. 253 00:11:59.080 --> 00:12:01.559 There's always a cat astrophysics. What is it? 254 00:12:01.759 --> 00:12:05.200 If the dye is glowing specifically in millimeter wavelengths, then 255 00:12:05.279 --> 00:12:08.240 pointing a regular telescope at it, like the Hubble space telescope, 256 00:12:08.240 --> 00:12:11.720 which looks primarily at visible and ultraviolet light, is completely useless. 257 00:12:11.799 --> 00:12:14.440 It's like wearing standard sunglasses to look for a specific 258 00:12:14.480 --> 00:12:17.039 infrared laser. You just have the wrong lenses. 259 00:12:17.080 --> 00:12:19.600 You have entirely the wrong lenses. If we want to 260 00:12:19.639 --> 00:12:23.399 map this massive invisible machinery, we need a machine that 261 00:12:23.519 --> 00:12:27.200 is specifically built from the ground up to see millimeter waves. 262 00:12:27.120 --> 00:12:31.960 Which brings us to the Atacoma Large Millimeter Submillimeter Array 263 00:12:32.080 --> 00:12:36.519 ALMA ALMA, which is, without hyperbole, one of the most 264 00:12:36.600 --> 00:12:41.200 phenomenal and frankly complex pieces of engineering ever constructed by 265 00:12:41.279 --> 00:12:41.879 human hands. 266 00:12:41.919 --> 00:12:44.360 It is the ultimate lens for peering into the dark. 267 00:12:44.639 --> 00:12:45.440 It's a marvel. 268 00:12:45.600 --> 00:12:48.240 Let's really dig into LMA because when you look at 269 00:12:48.240 --> 00:12:51.399 pictures of this facility, it honestly looks like a colony 270 00:12:51.440 --> 00:12:53.679 on another planet. It does not look like a traditional 271 00:12:53.720 --> 00:12:54.799 observatory at all. 272 00:12:54.919 --> 00:12:56.840 No, it doesn't, and it doesn't look like one because 273 00:12:56.840 --> 00:13:00.679 it operates on entirely different principles than a standard optical telescope. 274 00:13:01.279 --> 00:13:04.440 ALIMA is not just a single giant mirror housed inside 275 00:13:04.440 --> 00:13:05.600 a shiny silver dome. 276 00:13:05.720 --> 00:13:06.919 Right, It's a sprawling network. 277 00:13:07.000 --> 00:13:09.200 It is an array. It is a network of sixty 278 00:13:09.279 --> 00:13:13.759 six highly precess individual dish antennas. Most of them are 279 00:13:13.759 --> 00:13:17.279 twelve meters across, and they weigh over one hundred tons. 280 00:13:17.039 --> 00:13:18.919 Each one hundred tons each. Wow. 281 00:13:18.960 --> 00:13:21.320 But the most critical aspect of LMA isn't just the 282 00:13:21.360 --> 00:13:24.600 dishes themselves. It is where those dishes are physically located, right. 283 00:13:24.519 --> 00:13:27.000 The Attacama Desert in northern Chile. Yeah, but it's not 284 00:13:27.080 --> 00:13:29.440 just the desert. They built this thing at an altitude 285 00:13:29.480 --> 00:13:33.200 of five thousand meters, which is over sixteen four hundred 286 00:13:33.240 --> 00:13:36.080 feet above sea level. I mean, it is so high 287 00:13:36.159 --> 00:13:38.720 up that the engineers and the astronomers who maintain it 288 00:13:39.159 --> 00:13:43.559 literally have to carry supplemental oxygen tanks just to avoid hypoxia. 289 00:13:43.879 --> 00:13:47.039 It is a brutally hostile environment for human beings. 290 00:13:47.279 --> 00:13:50.240 So why on Earth do you take a multi billion 291 00:13:50.320 --> 00:13:54.879 dollar ultrasensitive international science project and stick it on top 292 00:13:54.919 --> 00:13:59.279 of a freezing oxygen deprived mountain. The logistics alone must be. 293 00:13:59.279 --> 00:14:01.879 A nightmare are but you do it to escape the 294 00:14:01.919 --> 00:14:05.679 Earth's atmosphere. Specifically, you are trying to escape the water vapor, 295 00:14:05.840 --> 00:14:10.120 ah the humidity exactly. Remember that the carbon monoxide die 296 00:14:10.200 --> 00:14:12.759 we are looking for emits radiation in the millimeter and 297 00:14:12.799 --> 00:14:16.519 submillimeter range. It turns out that atmospheric water vapor, the 298 00:14:16.639 --> 00:14:19.000 literal humidity in the air that we breathe down here 299 00:14:19.039 --> 00:14:22.840 on Earth, is incredibly efficient at absorbing those exact wavelengths, 300 00:14:22.879 --> 00:14:25.720 so it blocks the signal completely. If you build Alima 301 00:14:25.720 --> 00:14:28.519 in Florida, or even on a standard mountain in California, 302 00:14:28.919 --> 00:14:31.679 the moisture in the air would act like an opaque, dense, 303 00:14:31.759 --> 00:14:32.799 impenetrable wall. 304 00:14:33.120 --> 00:14:35.240 That's incredibly frustrating to think about. 305 00:14:35.519 --> 00:14:39.080 Right, The faint hum of the carbon monoxide traveling from 306 00:14:39.159 --> 00:14:42.960 fifty million light years away, would survive its entire cosmic 307 00:14:43.039 --> 00:14:46.639 journey across the universe, only to be entirely soaked up 308 00:14:46.679 --> 00:14:49.879 by a random marine cloud two miles above the telescope. 309 00:14:49.919 --> 00:14:51.679 It would just hit a brick wall at the very 310 00:14:51.759 --> 00:14:52.840 last possible. 311 00:14:52.480 --> 00:14:54.679 Second, exactly, So you have to get above the water. 312 00:14:55.039 --> 00:14:57.919 The Chajnantur Plateau in the a Kama Desert is one 313 00:14:57.960 --> 00:15:00.440 of the absolute driest places on the st surface of 314 00:15:00.440 --> 00:15:01.200 the planet, and. 315 00:15:01.159 --> 00:15:04.320 It's sixteen four hundred feet you're above most of the 316 00:15:04.360 --> 00:15:05.240 atmosphere anyway. 317 00:15:05.360 --> 00:15:08.000 Yes, you are sitting above the vast majority of the 318 00:15:08.039 --> 00:15:12.240 Earth's atmospheric blanket. The sky up there is exceptionally transparent 319 00:15:12.360 --> 00:15:15.279 to millimeter waves. It is truly as close to being 320 00:15:15.320 --> 00:15:18.159 an outer space as you can possibly get while still 321 00:15:18.200 --> 00:15:19.960 keeping your equipment anchored to the ground. 322 00:15:20.159 --> 00:15:23.600 Okay, so you have sixty six massive, one hundred ton 323 00:15:23.720 --> 00:15:27.480 dishes sitting high up in a dry barren desert. But 324 00:15:27.679 --> 00:15:30.120 you mentioned they form an array, so they don't just 325 00:15:30.159 --> 00:15:32.759 act like sixty six separate people looking through sixty six 326 00:15:32.759 --> 00:15:35.879 separate pairs of binoculars. Right, They work as a collective. 327 00:15:35.559 --> 00:15:37.679 They do, and the technique they used to do this 328 00:15:37.720 --> 00:15:41.440 is called interferometry. This is where the physics of waves 329 00:15:41.440 --> 00:15:44.960 becomes incredibly, incredibly useful. Okay, how so, Well, if you 330 00:15:45.000 --> 00:15:48.399 want to see highly detailed, sharp structures from millions of 331 00:15:48.480 --> 00:15:52.720 light years away, you fundamentally need a massive telescope. The 332 00:15:52.799 --> 00:15:55.600 larger the diameter of the dish, the sharper your resolution 333 00:15:55.720 --> 00:15:56.200 is going to be. 334 00:15:56.399 --> 00:15:58.519 That makes sense, bigger lens, better picture. 335 00:15:58.639 --> 00:16:01.519 But physically building a single telescope dish that is saved 336 00:16:01.799 --> 00:16:06.080 miles across is structurally impossible. It would simply collapse under 337 00:16:06.120 --> 00:16:06.639 its own weight. 338 00:16:06.759 --> 00:16:08.480 Gravity gets in the way exactly. 339 00:16:08.559 --> 00:16:11.440 Interferometry is basically the cheat code that gets around this 340 00:16:11.480 --> 00:16:12.679 physical limitation, a. 341 00:16:12.759 --> 00:16:16.039 Cheat code for building a bigger lens. I like that, 342 00:16:16.519 --> 00:16:18.000 How does the cheat code work? 343 00:16:18.360 --> 00:16:22.320 By linking multiple smaller dishes together, you can synthesize the 344 00:16:22.320 --> 00:16:24.720 aperture of a much larger virtual telescope. 345 00:16:24.840 --> 00:16:25.120 Okay. 346 00:16:25.879 --> 00:16:28.320 When the faint radiowave from the carbon monoxide in a 347 00:16:28.360 --> 00:16:32.039 distant galaxy arrives at Earth, it hits one antenna in 348 00:16:32.080 --> 00:16:36.240 the array a tiny microscopic fraction of a picosecond before 349 00:16:36.279 --> 00:16:37.200 it hits the next one. 350 00:16:37.240 --> 00:16:38.759 Because they're physically spread. 351 00:16:38.480 --> 00:16:41.279 Out right, the antennas are all connected by miles and 352 00:16:41.360 --> 00:16:45.320 miles of fiber optic cables to a specialized supercomputer which 353 00:16:45.320 --> 00:16:46.360 is called a correlator. 354 00:16:46.559 --> 00:16:49.519 The correlator that sounds very intense. 355 00:16:50.000 --> 00:16:54.759 It is incredibly intense. It is capable of performing quadrillions 356 00:16:54.759 --> 00:16:56.159 of operations per second. 357 00:16:56.279 --> 00:16:57.360 Quadrillions. 358 00:16:57.399 --> 00:17:00.519 Wow. Its entire job is to take the signs from 359 00:17:00.600 --> 00:17:04.880 all sixty six antennas and cross multiply them, constantly matching 360 00:17:04.920 --> 00:17:08.359 up the microscopic delays in the arrival times of the radio. 361 00:17:08.039 --> 00:17:09.519 Waves, so it stitches them together. 362 00:17:09.720 --> 00:17:14.000 Yes, and by doing this insanely complex math, the array 363 00:17:14.200 --> 00:17:17.880 acts as if it were a single colossal telescope whose 364 00:17:17.920 --> 00:17:20.640 overall diameter is equal to the distance between the two 365 00:17:20.720 --> 00:17:21.960 furthest antennas in the. 366 00:17:21.920 --> 00:17:24.720 Network, and the antennas aren't bolted to the ground permanently, 367 00:17:24.759 --> 00:17:27.079 are they. No, they aren't, because I've seen footage of 368 00:17:27.200 --> 00:17:30.960 these massive, custom built tractor vehicles that literally drive up 369 00:17:31.000 --> 00:17:33.519 to one hundred ton antenna, pick the whole thing up, 370 00:17:33.759 --> 00:17:36.240 and drive it across the desert to a new concrete pad. 371 00:17:36.519 --> 00:17:40.039 Yes, those are the Alma transporters. They're named Auto and Lore. 372 00:17:40.240 --> 00:17:43.599 They allow the entire array to be constantly reconfigured. 373 00:17:43.119 --> 00:17:45.200 So you can zoom in and out exactly. 374 00:17:45.480 --> 00:17:48.480 If astronomers want a wide field zoomed out view of 375 00:17:48.519 --> 00:17:51.960 the sky, they use the transporters to cluster all the 376 00:17:52.000 --> 00:17:55.880 antennas closely together. But if they want maximum sharpness, the 377 00:17:55.960 --> 00:17:59.400 ultimate zoom, they use the transporters to physically spread the 378 00:17:59.440 --> 00:18:01.440 antenna's across the desert plateau. 379 00:18:02.000 --> 00:18:02.839 How far apart. 380 00:18:02.920 --> 00:18:06.279 They can extend the baseline up to sixteen kilometers. 381 00:18:05.680 --> 00:18:10.160 Across sixteen kilometers, So you are literally computationally building a 382 00:18:10.200 --> 00:18:13.319 telescope the size of a major city just to stare 383 00:18:13.359 --> 00:18:14.119 deep into space. 384 00:18:14.279 --> 00:18:18.039 Yes, and the result of that city sized virtual dish 385 00:18:18.200 --> 00:18:23.160 is unprecedented angular resolution. When spread out, LMA can resolve 386 00:18:23.200 --> 00:18:25.279 details down to a fraction of an arcsecond. 387 00:18:25.319 --> 00:18:27.160 Okay, let's ground that. What does a fraction of an 388 00:18:27.240 --> 00:18:28.559 arcsecond actually look like. 389 00:18:28.880 --> 00:18:32.039 Imagine standing in New York City looking through a telescope 390 00:18:32.039 --> 00:18:34.880 and being able to clearly distinguish the individual dimples on 391 00:18:34.920 --> 00:18:37.079 a golf ball, sitting on a tee in Los Angeles. 392 00:18:37.160 --> 00:18:40.039 You are kidding, No, that is the level of pinpoint 393 00:18:40.079 --> 00:18:41.279 sharpness we are talking. 394 00:18:41.079 --> 00:18:44.279 About from New York to LA. That is insane, it is. 395 00:18:44.319 --> 00:18:47.920 And we absolutely need that sharpness because to see the 396 00:18:48.119 --> 00:18:51.720 fine internal structure of a giant molecular cloud that is 397 00:18:51.759 --> 00:18:55.079 only a few dozen parsecs across and located inside a 398 00:18:55.119 --> 00:18:58.039 galaxy tens of millions of light years away, you need 399 00:18:58.079 --> 00:18:59.759 the ultimate magnifying glass. 400 00:19:00.119 --> 00:19:04.680 And crucially, because Alima is looking at radio waves, it 401 00:19:04.720 --> 00:19:07.279