1 00:00:00,000 --> 00:00:01,880 Welcome back to Cosmos in a Pod. 2 00:00:01,880 --> 00:00:03,200 Yes, welcome back. 3 00:00:03,200 --> 00:00:06,080 For another deep dives into space and astronomy. 4 00:00:06,080 --> 00:00:08,240 This time, we're going all the way back. 5 00:00:08,240 --> 00:00:09,080 All the way. 6 00:00:09,080 --> 00:00:10,400 To the beginning of the universe. 7 00:00:10,400 --> 00:00:13,120 We're talking about the Cosmic Microwave Background. 8 00:00:13,120 --> 00:00:13,960 The CMB. 9 00:00:13,960 --> 00:00:15,520 Yeah, the CMB for short. 10 00:00:15,520 --> 00:00:18,280 The term's called the afterglow of the Big Bang. 11 00:00:18,280 --> 00:00:20,720 And yeah, I mean, that's kind of a cool way 12 00:00:20,720 --> 00:00:21,560 to think about it. 13 00:00:21,560 --> 00:00:22,380 Right. 14 00:00:22,380 --> 00:00:24,660 But it's so much more than just leftover light. 15 00:00:24,660 --> 00:00:25,500 Absolutely. 16 00:00:25,500 --> 00:00:26,880 It holds so many secrets. 17 00:00:26,880 --> 00:00:27,800 It really does. 18 00:00:27,800 --> 00:00:29,840 About how everything that we see came to be. 19 00:00:29,840 --> 00:00:30,880 Yeah. 20 00:00:30,880 --> 00:00:32,960 Galaxies, planets. 21 00:00:32,960 --> 00:00:33,480 Us. 22 00:00:33,480 --> 00:00:34,400 Yeah, even us. 23 00:00:34,400 --> 00:00:36,160 So to kick things off, can you just explain 24 00:00:36,160 --> 00:00:38,120 what exactly the CMB is? 25 00:00:38,120 --> 00:00:42,120 Yeah, so it really is more than just a faint glow. 26 00:00:42,120 --> 00:00:45,480 It's almost like a baby picture of the universe. 27 00:00:45,480 --> 00:00:46,000 Wow. 28 00:00:46,000 --> 00:00:48,440 You know, a snapshot from when the universe was just 29 00:00:48,440 --> 00:00:50,120 a tiny fraction of its current age. 30 00:00:50,120 --> 00:00:53,680 Like, imagine the universe as a newborn. 31 00:00:53,680 --> 00:00:57,900 A baby universe, just 380,000 years old. 32 00:00:57,900 --> 00:01:01,080 And back then, it was incredibly hot and dense, 33 00:01:01,080 --> 00:01:04,520 like a swirling soup of particles and energy. 34 00:01:04,520 --> 00:01:06,880 And actually, light couldn't even travel freely. 35 00:01:06,880 --> 00:01:07,380 Yeah. 36 00:01:07,380 --> 00:01:09,040 It kept bumping into all that stuff. 37 00:01:09,040 --> 00:01:12,760 But as the universe expanded and cooled down, 38 00:01:12,760 --> 00:01:16,000 things settled down enough for light to break free. 39 00:01:16,000 --> 00:01:16,500 Oh, wow. 40 00:01:16,500 --> 00:01:18,800 To travel across the cosmos. 41 00:01:18,800 --> 00:01:22,920 And that first burst of light is what we detect today 42 00:01:22,920 --> 00:01:24,240 as the CMB. 43 00:01:24,240 --> 00:01:25,760 So we're seeing light. 44 00:01:25,760 --> 00:01:28,640 It's been traveling for billions of years. 45 00:01:28,640 --> 00:01:29,600 We are. 46 00:01:29,600 --> 00:01:30,680 That's crazy. 47 00:01:30,680 --> 00:01:31,240 It is. 48 00:01:31,240 --> 00:01:33,480 But how did we even find this baby picture? 49 00:01:33,480 --> 00:01:34,320 Well, you're right. 50 00:01:34,320 --> 00:01:37,520 It's not like we can just point a telescope anywhere and see it. 51 00:01:37,520 --> 00:01:39,840 It took kind of a cosmic accident, you know. 52 00:01:39,840 --> 00:01:40,360 Oh, really? 53 00:01:40,360 --> 00:01:41,200 Yeah. 54 00:01:41,200 --> 00:01:47,000 Back in 1965, two physicists, Arno Penzias and Robert Wilson, 55 00:01:47,000 --> 00:01:49,880 were working with this giant radio antenna. 56 00:01:49,880 --> 00:01:53,000 And they kept picking up this annoying hum, 57 00:01:53,000 --> 00:01:53,980 this background noise. 58 00:01:53,980 --> 00:01:55,400 They just couldn't get rid of it. 59 00:01:55,400 --> 00:01:55,960 Really? 60 00:01:55,960 --> 00:01:56,840 Yeah. 61 00:01:56,840 --> 00:01:59,400 And at first, they thought it was interference. 62 00:01:59,400 --> 00:02:02,400 Maybe pigeon droppings messing with their equipment. 63 00:02:02,400 --> 00:02:03,200 Pigeon dropping? 64 00:02:03,200 --> 00:02:04,040 I know. 65 00:02:04,040 --> 00:02:04,840 That's hilarious. 66 00:02:04,840 --> 00:02:05,960 It's a funny story now. 67 00:02:05,960 --> 00:02:09,800 But back then, they were completely stumped. 68 00:02:09,800 --> 00:02:12,540 But it turns out that this noise was actually 69 00:02:12,540 --> 00:02:16,040 a signal from the universe's earliest days. 70 00:02:16,040 --> 00:02:16,680 No way. 71 00:02:16,680 --> 00:02:17,400 Yeah. 72 00:02:17,400 --> 00:02:20,960 And it just so happened that another group of scientists 73 00:02:20,960 --> 00:02:25,240 had predicted that if the Big Bang really happened, 74 00:02:25,240 --> 00:02:28,960 there should be this faint afterglow of radiation spread 75 00:02:28,960 --> 00:02:30,560 out across the universe. 76 00:02:30,560 --> 00:02:33,680 And boom, that's exactly what Penzias and Wilson 77 00:02:33,680 --> 00:02:35,120 had accidentally detected. 78 00:02:35,120 --> 00:02:39,520 So they won a Nobel Prize for basically finding pigeon. 79 00:02:39,520 --> 00:02:40,320 Basically. 80 00:02:40,320 --> 00:02:40,960 OK. 81 00:02:40,960 --> 00:02:44,360 So what can we actually learn from this ancient light? 82 00:02:44,360 --> 00:02:46,360 It tells us so much more than you might think. 83 00:02:46,360 --> 00:02:46,860 Really? 84 00:02:46,860 --> 00:02:47,440 Yeah. 85 00:02:47,440 --> 00:02:49,600 Like you know it's like a cosmic fingerprint. 86 00:02:49,600 --> 00:02:50,100 Oh, OK. 87 00:02:50,100 --> 00:02:53,680 Containing information about the universe's early ingredients, 88 00:02:53,680 --> 00:02:54,640 its shape. 89 00:02:54,640 --> 00:02:55,140 Wow. 90 00:02:55,140 --> 00:02:56,440 And even its future. 91 00:02:56,440 --> 00:02:57,480 OK. 92 00:02:57,480 --> 00:02:58,520 I'm hooked. 93 00:02:58,520 --> 00:03:00,140 You got me thinking about the universe. 94 00:03:00,140 --> 00:03:00,640 I'm glad. 95 00:03:00,640 --> 00:03:01,920 In a whole new way. 96 00:03:01,920 --> 00:03:04,920 I can't wait to hear more about what this fingerprint reveals. 97 00:03:04,920 --> 00:03:06,040 Yeah, for sure. 98 00:03:06,040 --> 00:03:08,240 Yeah, it really is like a cosmic fingerprint. 99 00:03:08,240 --> 00:03:10,000 And one of the biggest things it tells us 100 00:03:10,000 --> 00:03:12,560 is that the universe is surprisingly smooth. 101 00:03:12,560 --> 00:03:13,480 Smooth. 102 00:03:13,480 --> 00:03:16,040 But what about all the galaxies and stars and planets? 103 00:03:16,040 --> 00:03:18,000 It doesn't seem very smooth to me. 104 00:03:18,000 --> 00:03:20,680 Well, yeah, you're right on a small scale. 105 00:03:20,680 --> 00:03:21,180 OK. 106 00:03:21,180 --> 00:03:23,360 But when we look at the CMB, we're 107 00:03:23,360 --> 00:03:25,720 seeing the universe on a much grander scale. 108 00:03:25,720 --> 00:03:26,320 Oh, right. 109 00:03:26,320 --> 00:03:29,420 And the temperature of the CMB is almost exactly the same 110 00:03:29,420 --> 00:03:30,640 in every direction. 111 00:03:30,640 --> 00:03:31,140 Wow. 112 00:03:31,140 --> 00:03:33,560 It only varies by tiny fractions of a degree. 113 00:03:33,560 --> 00:03:34,040 OK. 114 00:03:34,040 --> 00:03:35,760 And this tells us that the early universe 115 00:03:35,760 --> 00:03:37,720 was incredibly uniform. 116 00:03:37,720 --> 00:03:40,240 So it was like if you took a giant cosmic blender 117 00:03:40,240 --> 00:03:41,840 and mixed everything up perfectly. 118 00:03:41,840 --> 00:03:42,600 Exactly. 119 00:03:42,600 --> 00:03:43,920 OK, that makes sense. 120 00:03:43,920 --> 00:03:47,240 But if everything was so evenly spread out in the beginning, 121 00:03:47,240 --> 00:03:49,880 how did we get all the clumps and clusters we see today? 122 00:03:49,880 --> 00:03:53,180 How did stars and galaxies even form 123 00:03:53,180 --> 00:03:54,440 if everything was so smooth? 124 00:03:54,440 --> 00:03:56,440 Well, that's where things get really interesting. 125 00:03:56,440 --> 00:03:56,940 OK. 126 00:03:56,940 --> 00:04:00,400 Because even though the CMB is remarkably uniform, 127 00:04:00,400 --> 00:04:04,560 it does have these tiny, tiny variations in temperature. 128 00:04:04,560 --> 00:04:07,440 We're talking about differences of just a few millionths 129 00:04:07,440 --> 00:04:08,280 of a degree. 130 00:04:08,280 --> 00:04:09,080 Wow. 131 00:04:09,080 --> 00:04:11,720 But believe it or not, those tiny variations 132 00:04:11,720 --> 00:04:13,460 are incredibly important. 133 00:04:13,460 --> 00:04:17,920 So these almost undetectable temperature differences, 134 00:04:17,920 --> 00:04:20,200 they're the key to the universe's structure. 135 00:04:20,200 --> 00:04:20,760 They are. 136 00:04:20,760 --> 00:04:21,760 How does that even work? 137 00:04:21,760 --> 00:04:22,920 Well, think of it like this. 138 00:04:22,920 --> 00:04:23,420 OK. 139 00:04:23,420 --> 00:04:26,120 Imagine a perfectly still pond. 140 00:04:26,120 --> 00:04:26,600 OK. 141 00:04:26,600 --> 00:04:28,600 Now drop a tiny pebble into it. 142 00:04:28,600 --> 00:04:30,340 All right, so you get ripples spreading out 143 00:04:30,340 --> 00:04:31,520 from where the pebble landed. 144 00:04:31,520 --> 00:04:32,120 Exactly. 145 00:04:32,120 --> 00:04:32,620 OK. 146 00:04:32,620 --> 00:04:34,920 And those tiny temperature variations in the CMB 147 00:04:34,920 --> 00:04:37,720 are like those pebbles in the pond. 148 00:04:37,720 --> 00:04:41,280 They represent slightly denser regions in the early universe. 149 00:04:41,280 --> 00:04:44,520 And over billions of years, gravity did its thing. 150 00:04:44,520 --> 00:04:48,160 It pulled more and more matter towards those denser areas 151 00:04:48,160 --> 00:04:50,540 and eventually forming the stars, galaxies, 152 00:04:50,540 --> 00:04:52,520 and clusters of galaxies that we see today. 153 00:04:52,520 --> 00:04:55,800 Wow, so those tiny, almost imperceptible variations 154 00:04:55,800 --> 00:04:58,480 were like the seeds of the entire cosmic web. 155 00:04:58,480 --> 00:04:59,480 That's mind boggling. 156 00:04:59,480 --> 00:05:00,480 It is. 157 00:05:00,480 --> 00:05:02,040 But how do we know all of this is true? 158 00:05:02,040 --> 00:05:03,880 I mean, how do we know the CMB is really 159 00:05:03,880 --> 00:05:06,440 telling us about the Big Bang in the early universe? 160 00:05:06,440 --> 00:05:07,680 Well, that's a great question. 161 00:05:07,680 --> 00:05:09,520 And the answer lies in the details 162 00:05:09,520 --> 00:05:11,080 of the CMB's properties. 163 00:05:11,080 --> 00:05:11,580 OK. 164 00:05:11,580 --> 00:05:14,280 The specific pattern of temperature fluctuations, 165 00:05:14,280 --> 00:05:16,960 the fact that the CMB has a black body spectrum, 166 00:05:16,960 --> 00:05:18,880 the way it's polarized. 167 00:05:18,880 --> 00:05:20,640 All of these things match up perfectly 168 00:05:20,640 --> 00:05:23,840 with what we'd expect to see if the Big Bang theory is correct. 169 00:05:23,840 --> 00:05:25,640 So like a giant cosmic puzzle. 170 00:05:25,640 --> 00:05:28,680 And the CMB is helping us put all the pieces together. 171 00:05:28,680 --> 00:05:29,840 Precisely. 172 00:05:29,840 --> 00:05:32,960 And the more we study the CMB, the more evidence 173 00:05:32,960 --> 00:05:35,040 we find to support this picture. 174 00:05:35,040 --> 00:05:37,600 So it's like we're constantly finding new clues. 175 00:05:37,600 --> 00:05:38,520 We are. 176 00:05:38,520 --> 00:05:39,880 Ooh, like what? 177 00:05:39,880 --> 00:05:41,600 Give me some of the big cosmic mysteries. 178 00:05:41,600 --> 00:05:43,360 Well, for one, there's dark matter. 179 00:05:43,360 --> 00:05:43,960 Dark matter. 180 00:05:43,960 --> 00:05:44,880 Yeah, I've heard of that. 181 00:05:44,880 --> 00:05:46,640 We know from the CMB that it makes up 182 00:05:46,640 --> 00:05:48,240 a huge chunk of the universe. 183 00:05:48,240 --> 00:05:48,740 OK. 184 00:05:48,740 --> 00:05:50,920 We still have no idea what it actually is. 185 00:05:50,920 --> 00:05:51,400 Right. 186 00:05:51,400 --> 00:05:53,040 We can't see it directly, but we know 187 00:05:53,040 --> 00:05:55,560 it's there because of its gravitational effects 188 00:05:55,560 --> 00:05:57,760 on galaxies and the CMB itself. 189 00:05:57,760 --> 00:05:59,800 So dark matter, it's like the universe 190 00:05:59,800 --> 00:06:02,080 is in double scaffolding, right? 191 00:06:02,080 --> 00:06:03,320 Holding everything together. 192 00:06:03,320 --> 00:06:04,200 Precisely. 193 00:06:04,200 --> 00:06:07,120 And then there's dark energy, which is even more mysterious. 194 00:06:07,120 --> 00:06:08,880 Oh, dark energy. 195 00:06:08,880 --> 00:06:12,160 It seems to be accelerating the expansion of the universe, 196 00:06:12,160 --> 00:06:15,320 but we're completely in the dark, no pun intended, 197 00:06:15,320 --> 00:06:16,720 about its nature. 198 00:06:16,720 --> 00:06:17,600 OK. 199 00:06:17,600 --> 00:06:19,280 Dark energy sounds like we're missing 200 00:06:19,280 --> 00:06:21,560 some pretty big pieces of the cosmic puzzle. 201 00:06:21,560 --> 00:06:25,080 We are, and that's why studying the CMB is so crucial. 202 00:06:25,080 --> 00:06:26,840 It's one of our best tools for probing 203 00:06:26,840 --> 00:06:29,040 the mysteries of dark matter, dark energy, 204 00:06:29,040 --> 00:06:30,720 and the very beginning of the universe. 205 00:06:30,720 --> 00:06:32,760 Right, I'm definitely on the edge of my seat here. 206 00:06:32,760 --> 00:06:35,360 So how do we actually study the CMB? 207 00:06:35,360 --> 00:06:37,640 I mean, it's not like we can just go out and scoop some up, 208 00:06:37,640 --> 00:06:38,200 right? 209 00:06:38,200 --> 00:06:41,200 No, but we can build incredibly sensitive instruments 210 00:06:41,200 --> 00:06:42,080 to detect it. 211 00:06:42,080 --> 00:06:42,600 OK. 212 00:06:42,600 --> 00:06:44,760 In fact, there have been several groundbreaking missions 213 00:06:44,760 --> 00:06:47,400 dedicated to studying the CMB in ever greater detail. 214 00:06:47,400 --> 00:06:48,640 So tell me about those missions. 215 00:06:48,640 --> 00:06:49,920 What have we learned from them? 216 00:06:49,920 --> 00:06:51,520 Yeah, so one of the most important 217 00:06:51,520 --> 00:06:54,200 was COBE, the Cosmic Background Explorer, 218 00:06:54,200 --> 00:06:56,520 launched back in 1989. 219 00:06:56,520 --> 00:06:59,120 It was the first mission to really map out the CMB 220 00:06:59,120 --> 00:07:02,120 in detail and confirm some of those key predictions 221 00:07:02,120 --> 00:07:03,080 about its properties. 222 00:07:03,080 --> 00:07:05,320 You know, it's a huge step forward in our understanding 223 00:07:05,320 --> 00:07:06,680 of the early universe. 224 00:07:06,680 --> 00:07:09,440 So COBE was like the pioneer, right? 225 00:07:09,440 --> 00:07:11,400 Paving the way for future missions. 226 00:07:11,400 --> 00:07:12,620 Exactly. 227 00:07:12,620 --> 00:07:16,680 And then came WMAP, the Wilkinson Microwave Anisotropy 228 00:07:16,680 --> 00:07:19,160 Probe, launched in 2001. 229 00:07:19,160 --> 00:07:23,400 And WMAP gave us an even more precise picture of the CMB, 230 00:07:23,400 --> 00:07:26,240 allowing us to measure those tiny temperature variations 231 00:07:26,240 --> 00:07:27,560 with incredible accuracy. 232 00:07:27,560 --> 00:07:29,600 It was like going from a blurry photo 233 00:07:29,600 --> 00:07:31,240 to a high-definition image. 234 00:07:31,240 --> 00:07:31,960 That's amazing. 235 00:07:31,960 --> 00:07:34,560 So we were able to see those ripples in much greater detail. 236 00:07:34,560 --> 00:07:35,320 Yes. 237 00:07:35,320 --> 00:07:37,040 And that gave us a wealth of information 238 00:07:37,040 --> 00:07:40,240 about the age, composition, and geometry of the universe. 239 00:07:40,240 --> 00:07:43,200 And then in 2009, the European Space Agency 240 00:07:43,200 --> 00:07:46,080 launched Planck, which took things to a whole new level. 241 00:07:46,080 --> 00:07:46,760 Planck, OK. 242 00:07:46,760 --> 00:07:48,520 Yeah, that name rings a bell. 243 00:07:48,520 --> 00:07:51,160 Didn't it create the most detailed map of the CMB we have? 244 00:07:51,160 --> 00:07:51,680 You got it. 245 00:07:51,680 --> 00:07:53,440 Planck's instruments were so sensitive 246 00:07:53,440 --> 00:07:55,880 that it was able to detect even fainter variations 247 00:07:55,880 --> 00:07:59,000 in the CMB, revealing even more subtle details 248 00:07:59,000 --> 00:08:00,480 about the early universe. 249 00:08:00,480 --> 00:08:02,060 It's incredible to think how far we've 250 00:08:02,060 --> 00:08:04,880 come since those first accidental observations back 251 00:08:04,880 --> 00:08:05,440 in the 60s. 252 00:08:05,440 --> 00:08:06,160 It really is. 253 00:08:06,160 --> 00:08:06,760 Yeah. 254 00:08:06,760 --> 00:08:09,120 A testament to human curiosity and ingenuity. 255 00:08:09,120 --> 00:08:10,360 So what's next? 256 00:08:10,360 --> 00:08:13,200 Are there any new missions planned to study the CMB? 257 00:08:13,200 --> 00:08:16,520 Oh, there are several exciting projects on the horizon. 258 00:08:16,520 --> 00:08:19,920 Scientists are working on developing even more sensitive 259 00:08:19,920 --> 00:08:21,960 instruments that could potentially 260 00:08:21,960 --> 00:08:26,160 detect the faint signature of primordial gravitational waves, 261 00:08:26,160 --> 00:08:28,440 you know, those ripples in spacetime 262 00:08:28,440 --> 00:08:31,520 from the very first moments after the Big Bang. 263 00:08:31,520 --> 00:08:32,480 Wow. 264 00:08:32,480 --> 00:08:33,520 That would be incredible. 265 00:08:33,520 --> 00:08:36,880 It would be like listening to the echo of the universe's 266 00:08:36,880 --> 00:08:37,280 birth. 267 00:08:37,280 --> 00:08:37,920 Exactly. 268 00:08:37,920 --> 00:08:40,920 And there are also proposals for new space telescopes 269 00:08:40,920 --> 00:08:43,360 that could study the polarization of the CMB 270 00:08:43,360 --> 00:08:46,720 in even greater detail, which could reveal even more 271 00:08:46,720 --> 00:08:49,840 about the nature of dark matter and dark energy. 272 00:08:49,840 --> 00:08:53,480 So the quest to understand the CMB and the secrets it holds 273 00:08:53,480 --> 00:08:54,520 is far from over. 274 00:08:54,520 --> 00:08:55,160 Definitely not. 275 00:08:55,160 --> 00:08:57,840 The CMB is like a cosmic Rosetta stone, 276 00:08:57,840 --> 00:09:00,240 providing a window into the earliest chapters 277 00:09:00,240 --> 00:09:01,360 of the universe's story. 278 00:09:01,360 --> 00:09:03,080 And the more we learn, the more we 279 00:09:03,080 --> 00:09:04,960 realize how much more there is to discover. 280 00:09:04,960 --> 00:09:07,600 Yeah, it's both humbling and inspiring at the same time. 281 00:09:07,600 --> 00:09:09,120 This has been an incredible deep dive 282 00:09:09,120 --> 00:09:11,000 into the cosmic microwave background. 283 00:09:11,000 --> 00:09:13,360 Yeah, it's been a pleasure sharing this journey with you. 284 00:09:13,360 --> 00:09:14,800 To all our listeners out there, I 285 00:09:14,800 --> 00:09:17,920 hope you found this exploration as fascinating as I have. 286 00:09:17,920 --> 00:09:21,160 If you want to learn more, we've got links to some great resources 287 00:09:21,160 --> 00:09:22,280 in our show notes. 288 00:09:22,280 --> 00:09:25,200 And of course, don't forget to subscribe to Cosmos in a Pod 289 00:09:25,200 --> 00:09:27,560 for more deep dives into the wonders of space 290 00:09:27,560 --> 00:09:28,440 and astronomy. 291 00:09:28,440 --> 00:09:31,280 You can find us on all the major podcast platforms, 292 00:09:31,280 --> 00:09:33,320 and be sure to check out our YouTube channel 293 00:09:33,320 --> 00:09:35,160 for even more cosmic content. 294 00:09:35,160 --> 00:09:39,320 Thanks for listening, and keep looking up.