WEBVTT 0 00:00:00.000 --> 00:00:03.000 Avery: Welcome to Astronomy Daily, the podcast that 1 00:00:03.000 --> 00:00:05.840 brings the cosmos down to Earth. I'm Avery. 2 00:00:05.840 --> 00:00:08.560 Anna: And I'm Anna. It's great to be with you 3 00:00:08.880 --> 00:00:11.800 today. We've got a fantastic lineup. We're 4 00:00:11.800 --> 00:00:14.240 starting with our own sun, which just put on 5 00:00:14.240 --> 00:00:17.040 a spectacular and slightly terrifying 6 00:00:17.040 --> 00:00:19.760 show for our most powerful solar telescope. 7 00:00:19.920 --> 00:00:22.320 Avery: Then we're heading into our own atmosphere, 8 00:00:22.480 --> 00:00:25.040 to a mysterious layer we can barely reach. 9 00:00:25.200 --> 00:00:27.680 And the brilliant new technology that might 10 00:00:27.760 --> 00:00:30.520 finally unlock its secrets. After that, we'll 11 00:00:30.520 --> 00:00:33.340 dig deep into Mars to find out why its 12 00:00:33.420 --> 00:00:35.660 insides are as chunky as a cookie. 13 00:00:35.740 --> 00:00:38.660 Anna: And finally, we'll tackle the big one, time 14 00:00:38.660 --> 00:00:41.460 travel. A new study suggests it might be 15 00:00:41.460 --> 00:00:44.140 possible, but it comes with a catch that 16 00:00:44.140 --> 00:00:46.700 changes everything. So let's get started. 17 00:00:46.860 --> 00:00:49.380 Avery: Alright, Anna, let's talk about the sun. We 18 00:00:49.380 --> 00:00:51.420 know it can be violent, but this is something 19 00:00:51.420 --> 00:00:54.020 else. The NSF Inouye Solar 20 00:00:54.020 --> 00:00:56.820 telescope just got its first look at an X 21 00:00:56.820 --> 00:00:59.500 class flare. And the images are mind 22 00:00:59.500 --> 00:00:59.980 blowing. 23 00:01:00.060 --> 00:01:02.940 Anna: They really are. For our listeners, an X 24 00:01:02.940 --> 00:01:05.680 class flare is the most powerful category of 25 00:01:05.680 --> 00:01:08.240 solar flare there is. These are massive 26 00:01:08.240 --> 00:01:10.840 explosions of energy and catching one with 27 00:01:10.840 --> 00:01:13.760 this level of detail is a huge deal. The 28 00:01:13.760 --> 00:01:15.680 telescope managed to capture it at a 29 00:01:15.680 --> 00:01:18.040 resolution where the smallest details are 30 00:01:18.040 --> 00:01:19.560 just four Earths across. 31 00:01:19.960 --> 00:01:22.360 Avery: That's incredible. It's like having a super 32 00:01:22.360 --> 00:01:24.760 powered magnifying glass on, um, the most 33 00:01:24.760 --> 00:01:26.920 energetic event in our solar system. 34 00:01:27.480 --> 00:01:29.800 So what did they actually see with this new 35 00:01:29.800 --> 00:01:30.600 level of clarity? 36 00:01:30.960 --> 00:01:33.720 Anna: They saw something called coronal loops, but 37 00:01:33.720 --> 00:01:36.280 on a scale we've never seen before. These are 38 00:01:36.280 --> 00:01:38.960 thin filaments of plasma that arch over the 39 00:01:38.960 --> 00:01:41.600 sun's surface following magnetic field lines. 40 00:01:41.760 --> 00:01:43.880 We've seen bundles of them before. But 41 00:01:43.880 --> 00:01:46.640 Inoue's power allowed scientists to see 42 00:01:46.800 --> 00:01:49.720 individual loops for the first time. Some 43 00:01:49.720 --> 00:01:52.640 of these loops were as small as 21 kilometres 44 00:01:52.640 --> 00:01:55.080 wide, which is right at the telescope's 45 00:01:55.080 --> 00:01:57.720 resolution limit. It's these magnetic field 46 00:01:57.720 --> 00:02:00.480 lines twisting, snapping and reconnecting 47 00:02:00.560 --> 00:02:02.560 that powers the solar flares in the first 48 00:02:02.560 --> 00:02:02.710 place. 49 00:02:03.340 --> 00:02:05.780 Avery: So saying the fundamental building blocks of 50 00:02:05.780 --> 00:02:08.700 these events is a game changer. I know these 51 00:02:08.700 --> 00:02:10.980 flares can be dangerous, knocking out radio 52 00:02:10.980 --> 00:02:13.020 communications and power grids here on Earth. 53 00:02:13.420 --> 00:02:15.100 Does this help us prepare for that? 54 00:02:15.500 --> 00:02:17.220 Anna: That's the goal. According to the 55 00:02:17.220 --> 00:02:19.540 researchers, peering into these smaller 56 00:02:19.540 --> 00:02:21.780 scales where the magnetic reconnection 57 00:02:21.780 --> 00:02:24.140 actually happens, opens the door to 58 00:02:24.140 --> 00:02:26.540 understanding the engine behind the flares. 59 00:02:26.780 --> 00:02:28.740 Better understanding leads to better 60 00:02:28.740 --> 00:02:31.140 prediction models, which gives us a better 61 00:02:31.140 --> 00:02:33.300 chance to protect our technology. When the 62 00:02:33.300 --> 00:02:36.120 sun decides to act, it's a huge step 63 00:02:36.120 --> 00:02:38.200 forward in forecasting space weather. 64 00:02:38.520 --> 00:02:41.000 Avery: From the very big to the very, 65 00:02:41.160 --> 00:02:41.960 very small. 66 00:02:42.600 --> 00:02:44.840 Our next Story is about exploring a part of 67 00:02:44.840 --> 00:02:47.440 our own atmosphere that's been stubbornly out 68 00:02:47.440 --> 00:02:50.280 of reach. The mesosphere. It's too high for 69 00:02:50.280 --> 00:02:52.680 balloons, but too low for satellites. 70 00:02:52.840 --> 00:02:55.640 Anna: Exactly. It's a huge blind spot for 71 00:02:55.640 --> 00:02:58.120 climate and weather data. But researchers at 72 00:02:58.120 --> 00:03:00.760 Harvard and the University of Chicago may 73 00:03:00.760 --> 00:03:02.890 have found a way to reach it. And it sounds 74 00:03:02.890 --> 00:03:04.330 like something out of science fiction. 75 00:03:04.570 --> 00:03:07.370 They've designed ultralight flying structures 76 00:03:07.370 --> 00:03:09.770 that float by harnessing sunlight itself. 77 00:03:10.170 --> 00:03:12.530 No engines, no fuel, powered by 78 00:03:12.530 --> 00:03:13.210 sunlight. 79 00:03:13.290 --> 00:03:14.250 Avery: How does that work? 80 00:03:14.410 --> 00:03:17.290 Anna: It uses a phenomenon called photoforces. 81 00:03:17.690 --> 00:03:20.650 It's a gentle force that pushes on an object 82 00:03:20.650 --> 00:03:22.610 when light heats one side more than the 83 00:03:22.610 --> 00:03:25.130 other. Down here on the ground, the force is 84 00:03:25.130 --> 00:03:27.610 so weak, we never notice it. But in the 85 00:03:27.610 --> 00:03:30.410 extremely thin air of the mesosphere, that 86 00:03:30.410 --> 00:03:32.650 tiny push is enough to overcome the weight of 87 00:03:32.650 --> 00:03:33.530 these new structures. 88 00:03:33.690 --> 00:03:36.030 Avery: So, so what are these things made of? They 89 00:03:36.030 --> 00:03:37.830 must be unbelievably light. 90 00:03:37.990 --> 00:03:40.630 Anna: They are. They're built from ultra thin 91 00:03:40.630 --> 00:03:43.270 ceramic alumina with a special coating on the 92 00:03:43.270 --> 00:03:45.710 bottom to absorb sunlight. The researchers 93 00:03:45.710 --> 00:03:47.870 actually tested them in a lab in a low 94 00:03:47.870 --> 00:03:50.309 pressure chamber that mimics the mesosphere. 95 00:03:50.310 --> 00:03:52.950 And they levitated perfectly with just a bit 96 00:03:52.950 --> 00:03:53.350 of light. 97 00:03:53.430 --> 00:03:55.190 Avery: That's amazing. The applications seem 98 00:03:55.190 --> 00:03:57.670 endless. You could attach sensors for climate 99 00:03:57.670 --> 00:04:00.350 data or create floating communication arrays 100 00:04:00.350 --> 00:04:03.010 like a, uh, low orbit starlink. One of the 101 00:04:03.010 --> 00:04:04.730 researchers even said they could eventually 102 00:04:04.730 --> 00:04:05.770 fly on Mars. 103 00:04:06.010 --> 00:04:08.970 Anna: That's the long term vision. Mars has a thin 104 00:04:08.970 --> 00:04:11.370 atmosphere that's very similar to our 105 00:04:11.370 --> 00:04:14.090 mesosphere, making it a perfect target. 106 00:04:14.570 --> 00:04:17.170 One of the lead authors called it the Wild 107 00:04:17.170 --> 00:04:19.770 west in terms of applied physics, because 108 00:04:19.770 --> 00:04:22.450 nothing has ever been able to fly sustainably 109 00:04:22.450 --> 00:04:25.210 up there before. This opens up an 110 00:04:25.210 --> 00:04:28.010 entirely new way to explore our upper 111 00:04:28.010 --> 00:04:30.530 atmosphere and potentially other 112 00:04:30.530 --> 00:04:31.370 worlds too. 113 00:04:32.200 --> 00:04:35.040 Speaking of Mars, our next story takes 114 00:04:35.040 --> 00:04:37.920 us deep inside the red planet. A 115 00:04:37.920 --> 00:04:40.400 new analysis has revealed that the 116 00:04:40.400 --> 00:04:43.360 interior of Mars is, and this is 117 00:04:43.360 --> 00:04:46.000 a direct quote, as chunky as a 118 00:04:46.000 --> 00:04:48.200 delicious macadamia cookie. 119 00:04:48.680 --> 00:04:50.720 Avery: I love it when scientists get creative with 120 00:04:50.720 --> 00:04:52.720 their analogies. So what does that mean 121 00:04:52.720 --> 00:04:55.440 exactly? It's not actually made of cookies, I 122 00:04:55.440 --> 00:04:55.960 assume. 123 00:04:56.600 --> 00:04:59.160 Anna: No. Unfortunately, what they found 124 00:04:59.320 --> 00:05:02.200 using data from the Insight lander is 125 00:05:02.200 --> 00:05:04.500 that huge chunks of Mars 126 00:05:04.580 --> 00:05:07.460 ancient early crust are preserved 127 00:05:07.540 --> 00:05:10.060 deep within its mantle. These are 128 00:05:10.060 --> 00:05:13.020 geological fossils from when the planet was 129 00:05:13.020 --> 00:05:15.940 first forming four and a half billion years 130 00:05:15.940 --> 00:05:16.260 ago. 131 00:05:16.820 --> 00:05:18.780 Avery: Insight was the mission that listened for 132 00:05:18.780 --> 00:05:21.740 Marsquakes. Right. So they used seismic waves 133 00:05:21.740 --> 00:05:23.780 to map the interior. Like an ultrasound. 134 00:05:24.100 --> 00:05:26.820 Anna: That's right. By studying how the waves from 135 00:05:26.820 --> 00:05:29.220 these quakes travelled and bounced, they 136 00:05:29.220 --> 00:05:31.510 couldn't map out the Composition. And they 137 00:05:31.510 --> 00:05:34.350 found these massive fragments, some up 138 00:05:34.350 --> 00:05:37.310 to four kilometres across, just drifting in 139 00:05:37.310 --> 00:05:39.870 the mantle. The theory is that during the 140 00:05:39.870 --> 00:05:41.990 chaotic early days of the solar system, 141 00:05:42.390 --> 00:05:45.310 giant impacts shattered the young planet's 142 00:05:45.310 --> 00:05:48.110 crust and those pieces sank into the 143 00:05:48.110 --> 00:05:51.030 molten mantle before a new crust formed. 144 00:05:51.430 --> 00:05:52.990 Avery: And they've just been sitting there ever 145 00:05:52.990 --> 00:05:53.350 since? 146 00:05:53.830 --> 00:05:56.750 Anna: Pretty much. Unlike Earth, Mars doesn't 147 00:05:56.750 --> 00:05:59.620 have active plate tectonics. Our crust and 148 00:05:59.620 --> 00:06:02.380 mantle are constantly churning and recycling 149 00:06:02.380 --> 00:06:04.940 each other. Mars has a single 150 00:06:05.020 --> 00:06:07.660 solid crust, a stagnant lid. 151 00:06:07.980 --> 00:06:10.860 So its interior evolution is much slower. 152 00:06:11.180 --> 00:06:13.260 It's acted like a, uh, time capsule, 153 00:06:13.340 --> 00:06:15.780 preserving this evidence of its violent 154 00:06:15.780 --> 00:06:18.380 birth. This gives us an incredible 155 00:06:18.380 --> 00:06:21.180 window into what rocky planets look like 156 00:06:21.180 --> 00:06:22.860 before tectonics get started. 157 00:06:23.500 --> 00:06:25.820 Avery: Okay, for our final story, we're going from 158 00:06:25.820 --> 00:06:28.560 planetary history to rewriting it. Or 159 00:06:29.040 --> 00:06:29.680 maybe not. 160 00:06:30.000 --> 00:06:31.520 Anna, uh, let's talk time travel. 161 00:06:32.000 --> 00:06:35.000 Anna: This is a really fascinating one. A new 162 00:06:35.000 --> 00:06:37.880 study looked at what would happen inside a 163 00:06:37.880 --> 00:06:40.600 spaceship travelling on a closed time 164 00:06:40.600 --> 00:06:43.600 like curve, which is basically a loop through 165 00:06:43.600 --> 00:06:46.400 space time that brings you back to the exact 166 00:06:46.400 --> 00:06:47.200 moment you left. 167 00:06:47.840 --> 00:06:50.680 Avery: The classic sci fi setup. So do we get to go 168 00:06:50.680 --> 00:06:53.360 back and fix our mistakes or accidentally 169 00:06:53.360 --> 00:06:55.320 erase ourselves from existence by bumping 170 00:06:55.320 --> 00:06:56.240 into our grandfather? 171 00:06:56.930 --> 00:06:59.170 Anna: Well, according to this research, neither. 172 00:06:59.570 --> 00:07:02.370 The study uses standard quantum mechanics 173 00:07:02.450 --> 00:07:05.370 and thermodynamics, not some exotic new 174 00:07:05.370 --> 00:07:07.410 theory. And the conclusion is 175 00:07:08.290 --> 00:07:10.850 the laws of physics themselves demand 176 00:07:11.410 --> 00:07:14.050 self consistency. After one full 177 00:07:14.050 --> 00:07:16.970 loop, everything inside the ship clocks 178 00:07:16.970 --> 00:07:19.770 computers, and even you must return 179 00:07:19.770 --> 00:07:21.090 to its original state. 180 00:07:21.650 --> 00:07:23.910 Avery: So time travel would be like pressing a 181 00:07:23.910 --> 00:07:25.190 cosmic reset button. 182 00:07:25.510 --> 00:07:27.830 Anna: Precisely. And it gets weirder. 183 00:07:28.230 --> 00:07:31.230 To maintain that consistency, the second law 184 00:07:31.230 --> 00:07:33.590 of thermodynamics, the one that says 185 00:07:33.590 --> 00:07:36.390 disorder or entropy always increases, 186 00:07:36.790 --> 00:07:39.790 has to be temporarily reversed. At a 187 00:07:39.790 --> 00:07:42.430 certain point in the loop, entropy hits a 188 00:07:42.430 --> 00:07:44.710 maximum and then it starts decreasing. 189 00:07:45.110 --> 00:07:47.990 Processes run backwards. Coffee would get 190 00:07:47.990 --> 00:07:50.540 warmer, broken eggs would reassemble. 191 00:07:50.860 --> 00:07:53.260 Avery: And what does that do to a person? What about 192 00:07:53.260 --> 00:07:53.900 our memories? 193 00:07:54.460 --> 00:07:57.420 Anna: This is the biggest catch. The formation of 194 00:07:57.420 --> 00:07:59.820 memory is a thermodynamic process, 195 00:08:00.220 --> 00:08:03.180 as entropy reverses to bring the system back 196 00:08:03.180 --> 00:08:05.900 to its starting state. Any memories you 197 00:08:05.900 --> 00:08:08.060 formed during the trip would have to be 198 00:08:08.060 --> 00:08:09.660 erased completely. 199 00:08:10.380 --> 00:08:12.540 Avery: So you could live through this incredible 200 00:08:12.540 --> 00:08:15.360 journey. But from your point of view, it 201 00:08:15.360 --> 00:08:17.000 would feel like nothing happened at all. 202 00:08:17.320 --> 00:08:19.280 You'd get in the ship, complete the loop, and 203 00:08:19.280 --> 00:08:21.920 arrive back in the same instant. With no 204 00:08:21.920 --> 00:08:22.840 memory of the trip. 205 00:08:23.160 --> 00:08:26.120 Anna: Exactly. It's the ultimate form of what 206 00:08:26.120 --> 00:08:28.920 happens in the loop stays in the loop because 207 00:08:29.000 --> 00:08:32.000 it gets completely wiped clean. So instead 208 00:08:32.000 --> 00:08:34.800 of rewriting history, you just reset 209 00:08:34.800 --> 00:08:37.760 it and forget it. A very different and 210 00:08:37.760 --> 00:08:40.440 much less adventurous picture of time travel 211 00:08:40.440 --> 00:08:41.480 than the movies suggest. 212 00:08:42.000 --> 00:08:43.680 Avery: And that's all the time we have for today, 213 00:08:43.920 --> 00:08:45.960 from the fiery heart of the sun to the 214 00:08:45.960 --> 00:08:48.680 delicate flyers in our atmosphere, the chunky 215 00:08:48.680 --> 00:08:50.800 interior of Mars, and the strange, 216 00:08:50.880 --> 00:08:53.040 forgettable physics of time travel. 217 00:08:53.600 --> 00:08:56.520 Anna: Thanks for joining us on Astronomy Daily. If 218 00:08:56.520 --> 00:08:58.320 you'd like to stay on top of the latest space 219 00:08:58.320 --> 00:09:00.840 and astronomy news, simply visit our website 220 00:09:00.840 --> 00:09:03.720 at astronomydaily IO and 221 00:09:03.720 --> 00:09:06.000 check out our constantly updating newsfeed. 222 00:09:06.400 --> 00:09:08.480 You can also find all our back episodes 223 00:09:08.480 --> 00:09:10.160 there. If you'd like to do some binge 224 00:09:10.160 --> 00:09:11.920 listening, I'm Anna. 225 00:09:12.480 --> 00:09:14.920 Avery: And I'm Avery. We'll see you next time for 226 00:09:14.920 --> 00:09:17.440 another look at our amazing universe. Until 227 00:09:17.440 --> 00:09:19.120 then, keep looking up.