WEBVTT 0 00:00:00.000 --> 00:00:02.440 Andrew Dunkley: Space Nuts is taking a bit of a break at the 1 00:00:02.440 --> 00:00:05.000 moment, Fred. Uh, and I will be back, uh, in 2 00:00:05.000 --> 00:00:06.880 the not too distant future with fresh 3 00:00:06.880 --> 00:00:09.440 episodes. In the meantime, enjoy some of, uh, 4 00:00:09.440 --> 00:00:12.240 the key episodes that we have presented over 5 00:00:12.240 --> 00:00:14.680 the years. Major events in 6 00:00:14.680 --> 00:00:17.440 astronomy and space science. And 7 00:00:17.440 --> 00:00:18.640 we'll see you real soon. 8 00:00:19.200 --> 00:00:20.240 Generic: Space Nuts. 9 00:00:20.400 --> 00:00:23.040 Andrew Dunkley: Hi there. Thanks for joining us on a Q and A 10 00:00:23.040 --> 00:00:25.880 edition of Space Nuts. I'm Andrew Dunkley, 11 00:00:25.880 --> 00:00:28.480 your host. Once again. Uh, thanks for joining 12 00:00:28.480 --> 00:00:31.160 us and, um, good to have your company. On 13 00:00:31.160 --> 00:00:32.840 this edition, we're, uh, answering some 14 00:00:32.840 --> 00:00:35.640 questions about light in space. Um, this 15 00:00:35.640 --> 00:00:38.120 one comes from Lee. He's asked a very 16 00:00:38.120 --> 00:00:39.680 interesting question. I've never actually 17 00:00:39.760 --> 00:00:41.040 thought about this particular 18 00:00:42.319 --> 00:00:45.240 concept, but, uh, it's a question that I 19 00:00:45.240 --> 00:00:47.960 think is worth answering for sure. That's why 20 00:00:47.960 --> 00:00:50.000 we included it. Fenton wants to know about, 21 00:00:50.100 --> 00:00:52.880 um, shielding astronauts in the 22 00:00:52.880 --> 00:00:54.720 outer reaches of the solar system. And he's 23 00:00:54.720 --> 00:00:57.110 got an idea on how to do that. Uh, 24 00:00:57.410 --> 00:00:59.690 Robert wants to, uh, talk about things we 25 00:00:59.690 --> 00:01:01.850 learned from the moon. And what if our moon 26 00:01:01.850 --> 00:01:04.370 wasn't the same as the moon is now? 27 00:01:04.610 --> 00:01:06.810 Would our learnings be different? That's a 28 00:01:06.810 --> 00:01:09.130 really interesting question. And Duncan wants 29 00:01:09.130 --> 00:01:11.370 to talk about ice giants. And why are they 30 00:01:11.370 --> 00:01:13.130 ice giants? Why don't we call them something 31 00:01:13.130 --> 00:01:15.970 else? That's all coming up shortly on this 32 00:01:15.970 --> 00:01:17.970 edition of Space Nuts. 33 00:01:18.130 --> 00:01:20.530 Generic: 15 seconds. Guidance is internal. 34 00:01:20.930 --> 00:01:23.570 10, 9. Ignition 35 00:01:23.570 --> 00:01:24.610 sequence start. 36 00:01:24.770 --> 00:01:25.730 Professor Fred Watson: Space Nuts. 37 00:01:25.730 --> 00:01:27.061 Generic: 5, 4, 3, 2. 38 00:01:27.129 --> 00:01:27.403 Duncan: 1. 39 00:01:27.471 --> 00:01:30.134 Generic: 2, 3, 4, 5, 5, 4, 3, 2, 40 00:01:30.202 --> 00:01:30.510 1. 41 00:01:30.590 --> 00:01:33.350 Professor Fred Watson: Space Nuts astronauts report at Beales. 42 00:01:33.350 --> 00:01:33.630 Good. 43 00:01:34.430 --> 00:01:37.110 Andrew Dunkley: Once again we welcome the one and only Fred 44 00:01:37.110 --> 00:01:39.550 Watson, astronomer at large. Hello, Fred. 45 00:01:39.790 --> 00:01:41.870 Professor Fred Watson: Hello, Andrew. How have you been since we 46 00:01:41.870 --> 00:01:42.510 last spoke? 47 00:01:43.790 --> 00:01:46.230 Andrew Dunkley: I haven't moved from this seat in all that 48 00:01:46.230 --> 00:01:46.510 time. 49 00:01:47.870 --> 00:01:50.230 Professor Fred Watson: Well, it's. I know. It's, uh. I can see 50 00:01:50.230 --> 00:01:52.000 you're glued to your chair there. Um, 51 00:01:53.390 --> 00:01:55.500 very much so. Uh, yes. 52 00:01:55.660 --> 00:01:57.980 Andrew Dunkley: Uh, shall we get, um, straight into it and 53 00:01:57.980 --> 00:02:00.060 answer some questions from our audience? 54 00:02:01.120 --> 00:02:03.100 Professor Fred Watson: Uh, that's a good idea. 55 00:02:03.100 --> 00:02:05.340 Andrew Dunkley: Yeah, it is. That's what we're here for. 56 00:02:05.580 --> 00:02:07.940 This first one, Fred, comes from Lee. He 57 00:02:07.940 --> 00:02:10.200 lives in New York City. Uh, 58 00:02:10.620 --> 00:02:13.340 he's asking how much light is in space. 59 00:02:14.380 --> 00:02:17.020 He'll qualify that question. For example, if 60 00:02:17.020 --> 00:02:19.820 you were to visit Voyager 1, where Voyager 1 61 00:02:19.820 --> 00:02:22.170 is today, would you be able to see. See it? 62 00:02:22.490 --> 00:02:25.250 Would you see just a silhouette? Would you be 63 00:02:25.250 --> 00:02:28.170 able to make out, uh, details and colors, if 64 00:02:28.170 --> 00:02:31.170 there are any colors on it? Uh, what about 65 00:02:31.170 --> 00:02:34.050 if, uh, you and Voyager were midway between 66 00:02:34.050 --> 00:02:36.890 the sun and Alpha Centauri? Uh, can we 67 00:02:37.210 --> 00:02:39.970 know a reasonably accurate answer, 68 00:02:39.970 --> 00:02:42.930 or is it pure speculation? Thanks. Love the 69 00:02:42.930 --> 00:02:45.690 show. Lee, from New York. I've never 70 00:02:45.690 --> 00:02:47.170 thought about that. I mean, we take for 71 00:02:47.170 --> 00:02:49.410 granted light on Earth because we're 72 00:02:49.410 --> 00:02:51.970 illuminated by the sun. But it's a bit 73 00:02:51.970 --> 00:02:54.470 different in other parts of the solar system 74 00:02:54.470 --> 00:02:56.710 and the universe in general. So, yeah, if we 75 00:02:56.710 --> 00:02:59.230 could just go, snap, we're out there next to 76 00:02:59.230 --> 00:03:02.030 Voyager 1. Could we actually see it? Is it 77 00:03:02.030 --> 00:03:04.230 illuminated in any way? Is it being 78 00:03:04.230 --> 00:03:06.870 illuminated by something? What would it be 79 00:03:06.870 --> 00:03:07.190 like? 80 00:03:08.460 --> 00:03:11.190 Professor Fred Watson: Uh, the answer is yes, you'd see it. Um, and 81 00:03:12.070 --> 00:03:14.270 so we're talking really now about the 82 00:03:14.270 --> 00:03:17.030 sensitivity of the human eye. Um, because, 83 00:03:17.340 --> 00:03:20.070 uh, with a camera, uh, you know, 84 00:03:20.950 --> 00:03:23.270 with long exposure settings and things you'd 85 00:03:23.270 --> 00:03:25.390 be able to see in great detail 86 00:03:25.950 --> 00:03:28.750 but thinking about the human eye. So, 87 00:03:29.380 --> 00:03:32.150 um, I used 88 00:03:32.150 --> 00:03:34.030 to work, as you know, at Siding Spring 89 00:03:34.030 --> 00:03:36.990 Observatory. Uh, I spent 90 00:03:36.990 --> 00:03:39.870 many hours, uh, outside at 91 00:03:39.870 --> 00:03:41.870 night. There it is a place that is truly 92 00:03:41.870 --> 00:03:44.830 dark. There's no interference from street 93 00:03:44.830 --> 00:03:47.790 lights. Uh, there are a few blobs of 94 00:03:47.790 --> 00:03:49.510 light on the horizon, but nothing that 95 00:03:49.510 --> 00:03:51.790 affects the pristine darkness of the night 96 00:03:51.790 --> 00:03:54.780 sky. And on a starry night 97 00:03:54.860 --> 00:03:57.340 with the sun not in the sky, you can see 98 00:03:57.340 --> 00:03:59.980 quite clearly. Um, there's enough 99 00:03:59.980 --> 00:04:02.860 light from the stars themselves to let 100 00:04:02.860 --> 00:04:05.740 you see where you're going. Uh, let 101 00:04:05.740 --> 00:04:08.740 you, you know, walk around and be 102 00:04:08.740 --> 00:04:10.620 quite confident that you're not going to fall 103 00:04:10.620 --> 00:04:12.580 off the mountain, as I nearly did one night 104 00:04:12.580 --> 00:04:15.300 when it was, uh, cloudy. I went out without 105 00:04:15.300 --> 00:04:16.900 my torch. I thought, oh, yeah, I'll see by 106 00:04:16.900 --> 00:04:18.860 the stars. But fortunately, unfortunately, 107 00:04:18.860 --> 00:04:20.340 the cloud had come in, I couldn't see 108 00:04:20.340 --> 00:04:22.620 anything and I nearly fell off the mountain. 109 00:04:23.370 --> 00:04:25.670 Uh, I didn't in the end. But, um. 110 00:04:25.850 --> 00:04:27.130 Andrew Dunkley: It's a long drop free. 111 00:04:27.530 --> 00:04:29.370 Professor Fred Watson: Yes, it is. Yes. It's quite a long drop 112 00:04:29.370 --> 00:04:31.930 anyway, uh, if you, uh, you know, 113 00:04:32.010 --> 00:04:34.730 normally on a starry night, you will see, 114 00:04:35.430 --> 00:04:38.330 um, by the light of the stars. Now, 115 00:04:38.330 --> 00:04:41.210 where voyager is Voyager 1, I 116 00:04:41.210 --> 00:04:44.110 just looked it up. Uh, it is, uh, 117 00:04:44.110 --> 00:04:46.650 at a distance from the sun 118 00:04:47.050 --> 00:04:49.730 in astronomical units, which is 119 00:04:49.730 --> 00:04:52.610 163 astronomical units. That's 120 00:04:52.610 --> 00:04:55.570 163 times the number 121 00:04:55.730 --> 00:04:58.570 of times the distance between the Earth and 122 00:04:58.570 --> 00:05:01.130 the sun. So that's 150 million 123 00:05:01.130 --> 00:05:04.130 kilometers. Multiply that by 163 124 00:05:04.370 --> 00:05:06.210 and you will get, 125 00:05:07.490 --> 00:05:10.450 uh. What do you get? I was looking for it in 126 00:05:10.450 --> 00:05:12.610 kilometers, but it's not there. I'll have to 127 00:05:12.610 --> 00:05:14.290 do the numbers anyway. It doesn't matter. The 128 00:05:14.290 --> 00:05:16.860 bad thing is, um, Its distance is 129 00:05:16.860 --> 00:05:19.140 22.55 light hours away. 130 00:05:19.700 --> 00:05:22.380 That's how long it takes, uh, the signal to 131 00:05:22.380 --> 00:05:25.100 get from Voyager to Earth. It's almost a day. 132 00:05:25.100 --> 00:05:28.020 It's almost a light day away. Um, 133 00:05:28.900 --> 00:05:31.219 so at that distance from the Sun, 134 00:05:31.219 --> 00:05:33.700 160 odd astronomical units, 135 00:05:34.180 --> 00:05:36.460 there's still significant light coming from 136 00:05:36.460 --> 00:05:38.660 the sun, not to mention Venus, 137 00:05:39.650 --> 00:05:42.580 uh, and um, you know, Jupiter and 138 00:05:42.870 --> 00:05:45.380 uh, the other planets. Mostly the sun though, 139 00:05:45.380 --> 00:05:47.900 you'd, you're being illuminated by the sun, 140 00:05:47.900 --> 00:05:50.580 so that's certainly opposite, uh, as 141 00:05:50.580 --> 00:05:53.220 compared with just being illuminated by the 142 00:05:53.220 --> 00:05:55.100 starry sky, which is what I was just talking 143 00:05:55.100 --> 00:05:57.170 about. So you'd see it really clearly. You 144 00:05:57.170 --> 00:05:59.060 uh, wouldn't have any problem making it out, 145 00:05:59.060 --> 00:06:01.300 assuming your eye was dark adapted. 146 00:06:03.380 --> 00:06:06.140 Andrew Dunkley: So, um, it's fairly bright out 147 00:06:06.140 --> 00:06:06.420 there. 148 00:06:06.740 --> 00:06:08.940 We talked about the sensitivity of the human 149 00:06:08.940 --> 00:06:11.380 eye as uh, you referred to 150 00:06:12.180 --> 00:06:14.660 how sort of small amount of light can we see 151 00:06:14.660 --> 00:06:15.700 as human beings? 152 00:06:16.770 --> 00:06:19.380 Professor Fred Watson: Um, I think there were some 153 00:06:19.540 --> 00:06:22.460 experiments. Let me think, was 154 00:06:22.460 --> 00:06:23.540 it one photon. 155 00:06:23.540 --> 00:06:25.380 Andrew Dunkley: Or one pixel like that? 156 00:06:25.380 --> 00:06:28.220 Professor Fred Watson: There was. That's right. We might have talked 157 00:06:28.220 --> 00:06:30.540 about this. There were experiments done that 158 00:06:30.540 --> 00:06:32.940 showed that the human eye is capable of 159 00:06:32.940 --> 00:06:35.940 detecting single photons. Uh, it was 160 00:06:35.940 --> 00:06:38.910 under special circumstances, but uh, 161 00:06:38.920 --> 00:06:41.870 and that is just extraordinary, um, 162 00:06:41.870 --> 00:06:44.440 when you think that the human eye can also 163 00:06:44.840 --> 00:06:47.360 cope with broad daylight. That's the 164 00:06:47.360 --> 00:06:49.920 amazing thing about the human eye. It can, 165 00:06:49.920 --> 00:06:52.600 you know, it's quite happy, uh, to see 166 00:06:53.080 --> 00:06:55.960 light, uh, one brightness and then 167 00:06:55.960 --> 00:06:58.440 a light that's only a millionth of as bright. 168 00:06:58.810 --> 00:07:01.190 Um, it's fine. You can deal with that. Ah. 169 00:07:01.190 --> 00:07:03.440 And that's a combination of what's called 170 00:07:03.440 --> 00:07:06.400 retinal bleaching and the iris of 171 00:07:06.400 --> 00:07:08.520 your eye opening and closing. It's all those 172 00:07:08.520 --> 00:07:10.470 things come together to give you this 173 00:07:11.030 --> 00:07:14.030 unbelievably versatile and sensitive 174 00:07:14.030 --> 00:07:16.910 tool with which we can look at the uh, our 175 00:07:16.910 --> 00:07:19.710 surroundings. Whether it's uh, the rock face 176 00:07:19.710 --> 00:07:21.710 I'm looking at now because that's what our 177 00:07:21.710 --> 00:07:24.670 backyard consists of, or whether it's uh, 178 00:07:24.670 --> 00:07:26.310 you know, the night sky where you're looking 179 00:07:26.310 --> 00:07:28.950 at faint objects, uh, in the sky. 180 00:07:29.030 --> 00:07:30.710 It's quite amazing. 181 00:07:31.270 --> 00:07:33.990 Andrew Dunkley: So even if you went deeper into space, way 182 00:07:33.990 --> 00:07:36.510 beyond our solar system, you, you would 183 00:07:36.510 --> 00:07:39.430 probably still see objects that you were 184 00:07:39.430 --> 00:07:39.670 near. 185 00:07:40.070 --> 00:07:41.750 Professor Fred Watson: There'd be enough light from the stars. The 186 00:07:41.750 --> 00:07:44.670 Milky Way is bright. Uh, it 187 00:07:44.670 --> 00:07:47.580 would, it would. You know, even if, as uh, 188 00:07:47.990 --> 00:07:50.950 Lee says, even if you were halfway between 189 00:07:51.190 --> 00:07:53.510 sun and Alpha Centauri, you'd still see it 190 00:07:53.510 --> 00:07:56.380 because of the ambient light, um, 191 00:07:56.380 --> 00:07:59.110 that's coming from, from the stars. Yeah. 192 00:07:59.110 --> 00:08:01.190 Andrew Dunkley: And you'd still see color because that's 193 00:08:01.190 --> 00:08:03.310 what. Well, it's dark enough, it might turn 194 00:08:03.310 --> 00:08:04.710 into the grays, which happens. 195 00:08:04.790 --> 00:08:06.510 Professor Fred Watson: That's right. Yeah. And I think that's 196 00:08:06.510 --> 00:08:08.470 likely. I think, I don't Think you would see 197 00:08:08.470 --> 00:08:11.130 color? Um, you. You would. Where it is now, 198 00:08:11.130 --> 00:08:12.650 there's enough light coming from the sun that 199 00:08:12.650 --> 00:08:15.130 you'd see color. But I think, uh, when you 200 00:08:15.130 --> 00:08:17.730 got further out, you would start to just see 201 00:08:17.730 --> 00:08:20.530 the. You know, as you said, that 202 00:08:21.410 --> 00:08:23.890 sort of pale gray appearance. Where you're 203 00:08:23.890 --> 00:08:25.890 looking at very low light. Low light levels 204 00:08:25.890 --> 00:08:27.530 indeed. Where the color cells aren't 205 00:08:27.530 --> 00:08:28.130 receptive. 206 00:08:29.090 --> 00:08:30.970 Andrew Dunkley: There you go. Lee, uh, the answer to your 207 00:08:30.970 --> 00:08:32.890 question's yes to all of the above, 208 00:08:32.890 --> 00:08:33.410 Basically. 209 00:08:33.730 --> 00:08:34.370 Duncan: Yeah. 210 00:08:34.930 --> 00:08:36.789 Andrew Dunkley: Great question. Excellent question. 211 00:08:37.589 --> 00:08:39.509 All right, let's move on. This is from 212 00:08:39.509 --> 00:08:40.069 Fenton. 213 00:08:40.789 --> 00:08:43.309 Duncan: Yeah. Hello, Fred and Andrew. This is 214 00:08:43.309 --> 00:08:46.189 Fenton contacting you from St. 215 00:08:46.189 --> 00:08:48.629 Paul, Minnesota, in the U.S. 216 00:08:49.480 --> 00:08:52.389 um, I sort of have a different type of 217 00:08:52.389 --> 00:08:54.709 astrophysical question for you. 218 00:08:55.349 --> 00:08:58.069 And this is on how to 219 00:08:58.069 --> 00:09:00.469 shield astronauts from 220 00:09:00.869 --> 00:09:03.749 radiation outside of the Van Allen Belt. 221 00:09:04.440 --> 00:09:07.390 Um, I was curious if you know of any pending 222 00:09:07.390 --> 00:09:10.310 technologies. That would allow this 223 00:09:10.790 --> 00:09:13.510 obvious choice would some people would say is 224 00:09:13.510 --> 00:09:16.030 lead. But I can think of several reasons why 225 00:09:16.030 --> 00:09:18.790 this is not a good idea. How about 226 00:09:18.950 --> 00:09:21.750 a miniature Van Allen Belt 227 00:09:21.990 --> 00:09:24.350 which could surround a 228 00:09:24.350 --> 00:09:27.270 spacecraft? How does that sound? How 229 00:09:27.270 --> 00:09:29.830 could this become, uh, reality? 230 00:09:30.380 --> 00:09:32.340 Thank you very much. I hope you like the 231 00:09:32.340 --> 00:09:34.060 question. Bye now. 232 00:09:34.700 --> 00:09:36.620 Andrew Dunkley: Thanks, Fenton. Fenton always has these 233 00:09:36.620 --> 00:09:39.140 intriguing thoughts. I've noticed in the 234 00:09:39.140 --> 00:09:41.540 Times that we've heard from him. Um, maybe we 235 00:09:41.540 --> 00:09:43.740 should start by explaining what the Van Allen 236 00:09:43.740 --> 00:09:45.540 Belt is. For those of us who just can't 237 00:09:45.540 --> 00:09:46.459 remember, like me. 238 00:09:48.710 --> 00:09:50.750 Professor Fred Watson: Um, it's, uh. 239 00:09:51.580 --> 00:09:53.820 So the Van Allen belts are the. Basically 240 00:09:53.820 --> 00:09:56.220 the. You know, the magnetic shielding 241 00:09:56.710 --> 00:09:59.030 around the Earth, uh, which is, 242 00:09:59.790 --> 00:10:02.230 uh. Caused by 243 00:10:02.710 --> 00:10:04.870 the magnetism of the Earth. It's caused by, 244 00:10:05.430 --> 00:10:08.390 uh, the fact that we've got an iron core. And 245 00:10:09.990 --> 00:10:11.870 basically, uh, it's in two parts. It's solid 246 00:10:11.870 --> 00:10:14.030 and liquid. So it acts like a dynamo. It's 247 00:10:14.030 --> 00:10:16.650 rotating. And that gives us this, uh. 248 00:10:16.650 --> 00:10:18.650 Exactly the protection that, um. 249 00:10:19.170 --> 00:10:21.430 Um. Um. Fenton is talking about. 250 00:10:22.230 --> 00:10:22.400 Andrew Dunkley: Um. 251 00:10:22.640 --> 00:10:25.200 Professor Fred Watson: Yeah, I was gonna refer. 252 00:10:25.840 --> 00:10:27.600 I'm a bit annoyed actually, because I've lost 253 00:10:27.600 --> 00:10:30.200 it. Uh, there is a very 254 00:10:30.200 --> 00:10:32.350 nice article on, um. 255 00:10:33.530 --> 00:10:35.230 Uh, it's actually on the, um. 256 00:10:35.600 --> 00:10:38.430 BBC's website. Uh, 257 00:10:38.640 --> 00:10:41.520 their sky at Night website. There's a lovely 258 00:10:41.520 --> 00:10:44.240 article on exactly this. Here it is. I found 259 00:10:44.240 --> 00:10:47.040 it. I hadn't lost it. How astronauts can hide 260 00:10:47.040 --> 00:10:49.940 from radiation on Mars. And it goes into, 261 00:10:50.690 --> 00:10:53.540 uh. Exactly the problem that, 262 00:10:53.550 --> 00:10:55.500 uh, Fenton's talking about. How do you 263 00:10:55.500 --> 00:10:58.500 present. How do you prevent, um, astronauts 264 00:10:59.220 --> 00:11:01.620 basically becoming irradiated. 265 00:11:02.050 --> 00:11:04.939 Uh, and over time it's 266 00:11:04.939 --> 00:11:07.460 basically lethal. Uh, because 267 00:11:07.940 --> 00:11:10.820 of the cosmic radiation that's coming down 268 00:11:10.900 --> 00:11:12.980 through space. Uh, and 269 00:11:14.180 --> 00:11:16.940 the cell damage, uh, in your 270 00:11:16.940 --> 00:11:19.890 body. Uh, and it can actually trigger cancer. 271 00:11:20.370 --> 00:11:23.250 So, um, the whole study of 272 00:11:23.490 --> 00:11:26.290 this is. Sorry, 273 00:11:26.450 --> 00:11:29.290 the thrust of this article, BBC sky at 274 00:11:29.290 --> 00:11:31.650 Night magazine, uh, is to 275 00:11:32.210 --> 00:11:34.690 discuss how you might protect astronauts, 276 00:11:35.130 --> 00:11:37.730 uh, from the radiation. Uh, and that's not 277 00:11:37.730 --> 00:11:40.190 just on Mars, but on route. Uh, 278 00:11:40.190 --> 00:11:42.850 okay, uh, the 279 00:11:43.860 --> 00:11:46.660 solution that Fenton has suggested 280 00:11:46.900 --> 00:11:48.860 is covered in a paragraph. I'm going to read 281 00:11:48.860 --> 00:11:51.590 it because we quoted where the source is. Uh, 282 00:11:51.590 --> 00:11:54.420 for example. All right, 283 00:11:54.820 --> 00:11:57.180 let me go back a paragraph. One method of 284 00:11:57.180 --> 00:11:59.459 helping astronauts to avoid the radiation on 285 00:11:59.459 --> 00:12:02.380 Mars is active shielding. For 286 00:12:02.380 --> 00:12:05.340 example, superconducting electromagnets could 287 00:12:05.340 --> 00:12:07.860 be used to create a powerful magnetic field 288 00:12:08.100 --> 00:12:10.300 to deflect the incoming charged radiation 289 00:12:10.300 --> 00:12:12.420 particles away, just as the Earth's field 290 00:12:12.420 --> 00:12:15.380 does. That's the Van Allen Belt. The problem 291 00:12:15.380 --> 00:12:17.820 is that such solutions can demand a lot of 292 00:12:17.820 --> 00:12:20.700 power to run, and the technology is a long 293 00:12:20.700 --> 00:12:23.540 way from being fully developed. An easier 294 00:12:23.540 --> 00:12:25.940 alternative is passive shielding. Simply 295 00:12:25.940 --> 00:12:28.380 placing a thick bulk of shielding material 296 00:12:28.620 --> 00:12:30.780 between the crew habitat and the sky. 297 00:12:31.540 --> 00:12:34.060 Uh, and then they go on to consider different 298 00:12:34.540 --> 00:12:37.510 materials. Aluminium, AKA 299 00:12:37.510 --> 00:12:40.350 aluminum, the metal that spacecraft are 300 00:12:40.350 --> 00:12:42.310 constructed from is actually a pretty bad 301 00:12:42.310 --> 00:12:45.110 radiation shield. Um, and 302 00:12:45.190 --> 00:12:47.950 they say when hit by an energetic cosmic 303 00:12:47.950 --> 00:12:50.430 ray, its atoms can shatter and fly onwards to 304 00:12:50.430 --> 00:12:52.470 create even more radiation particles. 305 00:12:53.190 --> 00:12:55.950 And Martian soil, the regolith, uh, which if 306 00:12:55.950 --> 00:12:58.070 you're on Mars, you might think about digging 307 00:12:58.070 --> 00:13:00.710 a hole there. Uh, it's got the same problem, 308 00:13:00.790 --> 00:13:03.390 but it's actually, uh, you know, 309 00:13:03.390 --> 00:13:06.130 abundant. Um, and so you 310 00:13:06.130 --> 00:13:09.090 could use that to dig a pole. If you 311 00:13:09.090 --> 00:13:12.090 put a 2 to 3 meter layer on top of 312 00:13:12.090 --> 00:13:14.770 your habitat, uh, then you'll, 313 00:13:14.770 --> 00:13:17.570 you'll get some protection. But, uh, the 314 00:13:17.570 --> 00:13:20.530 thing that surprised me, Andrew, uh, is once 315 00:13:20.530 --> 00:13:23.160 again, it comes from this same article. Uh, 316 00:13:23.370 --> 00:13:25.850 hydrogen is the best shielding material 317 00:13:26.170 --> 00:13:28.890 as it's light atoms. Yeah, it's light 318 00:13:28.890 --> 00:13:31.820 atoms. Uh, and by light I mean 319 00:13:31.820 --> 00:13:34.300 not heavy. Its light atoms don't create as 320 00:13:34.300 --> 00:13:37.180 much secondary radiation. And so tanks of 321 00:13:37.180 --> 00:13:39.860 rocket fuel or water, which is 322 00:13:39.940 --> 00:13:42.620 rich in hydrogen, placed over crew quarters 323 00:13:42.620 --> 00:13:44.420 could double up as effective radiation 324 00:13:44.420 --> 00:13:47.130 shields. I've heard that before that, um, 325 00:13:47.540 --> 00:13:49.900 one way of protecting your spacecraft as it 326 00:13:49.900 --> 00:13:52.340 flies to Mars is put it in a tank of water. 327 00:13:53.040 --> 00:13:55.060 Uh, it's the last thing you'd expect to do, 328 00:13:55.060 --> 00:13:57.880 but water is a good shielding material. 329 00:13:58.200 --> 00:14:01.000 And they also, uh, point out the 330 00:14:01.080 --> 00:14:03.600 alternative of hydrogen rich plastics like 331 00:14:03.600 --> 00:14:05.720 polyethylene could be used to cement 332 00:14:06.120 --> 00:14:08.320 regolith grains together. This is on Mars. 333 00:14:08.320 --> 00:14:11.060 And improve their shielding effect. Um, 334 00:14:11.800 --> 00:14:13.840 so, uh, if you want to read more about this, 335 00:14:13.840 --> 00:14:16.280 it's an article that originally appeared in 336 00:14:16.280 --> 00:14:19.080 the August 2022 issue of BBC 337 00:14:19.080 --> 00:14:21.530 sky at Night magazine. And it covers pretty 338 00:14:21.530 --> 00:14:23.810 well most of the ideas, uh, that have been, 339 00:14:23.810 --> 00:14:26.370 that have been suggested for this radiation 340 00:14:26.370 --> 00:14:28.650 issue. It's one that's got to, you know, it's 341 00:14:28.650 --> 00:14:31.490 got to find an answer soon because, uh, 342 00:14:31.650 --> 00:14:34.440 good old Elon and his starship, uh, 343 00:14:34.440 --> 00:14:36.410 is getting nearer to thinking about going to 344 00:14:36.410 --> 00:14:37.650 Mars. I don't think it's ever going to 345 00:14:37.650 --> 00:14:40.650 happen, but, uh, that's something he'll 346 00:14:40.650 --> 00:14:41.730 definitely be thinking about. 347 00:14:42.610 --> 00:14:45.090 Andrew Dunkley: Yes, indeed. He's too busy dealing with the 348 00:14:45.090 --> 00:14:46.450 Australian government at the moment. 349 00:14:47.570 --> 00:14:48.210 Professor Fred Watson: That's right. 350 00:14:48.690 --> 00:14:50.370 Andrew Dunkley: Some of the content on Twitter that the 351 00:14:50.370 --> 00:14:53.210 government wants to get rid of simply because 352 00:14:53.210 --> 00:14:55.530 of its, um, volatility. But anyway, that's a 353 00:14:55.530 --> 00:14:57.530 different story. Um, but there's plenty of 354 00:14:57.530 --> 00:15:00.410 water on Mars, so maybe, maybe creating those 355 00:15:00.410 --> 00:15:03.290 water barriers is probably the simplest thing 356 00:15:03.290 --> 00:15:05.050 to do. You've already got the material there. 357 00:15:05.770 --> 00:15:07.490 Professor Fred Watson: If you've landed in the right spot where 358 00:15:07.490 --> 00:15:09.370 you've got permafrost or whatever. 359 00:15:09.370 --> 00:15:11.730 Andrew Dunkley: That's the question. Yes, indeed. Uh, well 360 00:15:11.730 --> 00:15:14.050 done, Fenton. You actually happened across 361 00:15:14.050 --> 00:15:16.810 some of, uh, the answers too in, uh, asking 362 00:15:16.810 --> 00:15:19.410 your question. Uh, this is Space 363 00:15:19.410 --> 00:15:21.930 Nuts Andrew Dunkley here with Professor Fred 364 00:15:21.930 --> 00:15:22.570 Watson. 365 00:15:25.590 --> 00:15:27.670 Generic: Three, two, one. 366 00:15:28.310 --> 00:15:29.510 Andrew Dunkley: Space Nuts. 367 00:15:29.830 --> 00:15:32.390 Now, Fred, uh, our next question comes from 368 00:15:32.470 --> 00:15:34.790 Robert. Hi guys. Love your show. Sorry for 369 00:15:34.790 --> 00:15:36.590 the long question, but feel free to 370 00:15:36.590 --> 00:15:39.230 paraphrase, uh, or shorten it. Our 371 00:15:39.230 --> 00:15:42.150 moon is heavily crated and has given 372 00:15:42.150 --> 00:15:44.110 us a lot of insight into the history of the 373 00:15:44.110 --> 00:15:46.190 solar system and perhaps how the planets 374 00:15:46.190 --> 00:15:48.710 formed. But what if we had a moon 375 00:15:49.030 --> 00:15:51.430 like the icy moon Europa or the 376 00:15:51.430 --> 00:15:54.430 shrouded in, uh, haze Titan, both of 377 00:15:54.430 --> 00:15:56.730 which don't show immediate evidence of 378 00:15:56.730 --> 00:15:59.730 cratering? Would our theory about, uh, how 379 00:15:59.730 --> 00:16:02.090 the planets developed would, uh, be 380 00:16:02.090 --> 00:16:04.450 different? What other insights about our 381 00:16:04.450 --> 00:16:07.410 solar system would be missing or would 382 00:16:07.410 --> 00:16:10.010 we be missing? And lastly, uh, would we have 383 00:16:10.010 --> 00:16:12.610 spent, uh, or would we have sent people to 384 00:16:12.610 --> 00:16:14.960 land on such moons, that is, uh, 385 00:16:15.570 --> 00:16:18.410 would they be more dangerous for 386 00:16:18.410 --> 00:16:19.930 astronauts? Cheers. 387 00:16:19.930 --> 00:16:22.530 Robert in Vienna, Austria. Wow. I don't think 388 00:16:22.530 --> 00:16:24.250 we've had a question from Vienna before, have 389 00:16:24.250 --> 00:16:26.720 we? Lovely to hear from you, Robert. 390 00:16:27.120 --> 00:16:28.840 Professor Fred Watson: I think, I think Robert might have been in 391 00:16:28.840 --> 00:16:29.600 touch once before. 392 00:16:29.920 --> 00:16:32.600 Andrew Dunkley: Oh, I might have been too. It's very rare to 393 00:16:32.600 --> 00:16:33.600 hear from Vienna. 394 00:16:34.000 --> 00:16:35.560 Professor Fred Watson: Yeah, I was in Vienna at the beginning of 395 00:16:35.560 --> 00:16:37.360 last year and I think, I think we got 396 00:16:37.360 --> 00:16:39.040 something around about the same time. And I 397 00:16:39.040 --> 00:16:41.840 was waxing lyrical about being in Vienna at 398 00:16:41.840 --> 00:16:44.160 the UN when I was at, uh, the copywritten 399 00:16:44.160 --> 00:16:46.440 meeting. Anyway, that's another, another 400 00:16:46.440 --> 00:16:49.320 issue. Uh, what if we had a. Yeah, it's a 401 00:16:49.320 --> 00:16:51.730 really interesting question. Um, 402 00:16:52.310 --> 00:16:55.190 what would we not know about 403 00:16:55.590 --> 00:16:57.750 the solar system. If our moon 404 00:16:58.230 --> 00:17:00.950 was basically one 405 00:17:01.030 --> 00:17:03.670 that had been resurfaced in recent years 406 00:17:03.990 --> 00:17:06.830 or even millennia, because that's what makes 407 00:17:06.830 --> 00:17:09.110 the surface smooth. That's how we 408 00:17:09.110 --> 00:17:11.830 recognize, um, the 409 00:17:11.910 --> 00:17:14.230 fact that the universe. Sorry, that the. 410 00:17:15.350 --> 00:17:17.990 It's how we recognize the age of a surface is 411 00:17:17.990 --> 00:17:20.510 by how many craters it's got. The older, the 412 00:17:20.510 --> 00:17:22.809 older the surface, the more craters it has. 413 00:17:23.129 --> 00:17:25.809 And so the Moon's southern region, which is 414 00:17:25.809 --> 00:17:28.670 heavily cratered, as is the backside, tell 415 00:17:28.670 --> 00:17:31.089 uh, us that, uh, early on in the solar 416 00:17:31.089 --> 00:17:33.809 system's history, it was a very, um, wild and 417 00:17:33.809 --> 00:17:36.049 woolly place with things charging about all 418 00:17:36.049 --> 00:17:38.969 over and causing these craters. Now if we 419 00:17:38.969 --> 00:17:41.130 had a moon that was like Europa, that had, 420 00:17:41.130 --> 00:17:43.230 um, you know, icy, uh, 421 00:17:43.649 --> 00:17:46.369 geysers on it that basically covered up the 422 00:17:46.369 --> 00:17:49.289 craters, would we have known about that? My 423 00:17:49.369 --> 00:17:52.369 guess is yes, we would, because we'd 424 00:17:52.369 --> 00:17:54.030 see other bodies within the solar solar 425 00:17:54.030 --> 00:17:56.790 system, uh, like, you know, other moons, 426 00:17:56.950 --> 00:17:59.190 like, um, places like, 427 00:18:00.040 --> 00:18:02.630 um, Ceres, um, the biggest of the 428 00:18:02.630 --> 00:18:04.390 asteroids, the dwarf planet that dominates 429 00:18:04.390 --> 00:18:06.950 the asteroid belt that's heavily cratered. 430 00:18:07.260 --> 00:18:09.750 Uh, parts of Pluto are heavily cratered. 431 00:18:10.000 --> 00:18:10.140 Duncan: Um. 432 00:18:11.940 --> 00:18:14.790 Professor Fred Watson: Uh, Mimas, uh, one of Saturn's 433 00:18:15.190 --> 00:18:18.190 moons is heavily cratered too. So we'd 434 00:18:18.190 --> 00:18:20.270 know about it by looking at other objects. 435 00:18:20.270 --> 00:18:23.000 Even if our own moon was smoothly, uh, 436 00:18:23.570 --> 00:18:26.210 surfaced, um, it's, it's, uh. 437 00:18:26.370 --> 00:18:29.260 But the. Robert's last point, uh, on, 438 00:18:29.260 --> 00:18:31.730 um, this would, uh. We have sent 439 00:18:31.970 --> 00:18:34.970 people to land on such a moon. I, 440 00:18:34.970 --> 00:18:37.649 uh, think, um. I don't know. That's a really 441 00:18:37.649 --> 00:18:39.770 good question. I mean, we have sent people to 442 00:18:39.770 --> 00:18:42.610 land on our moon as it stands, uh, with an 443 00:18:42.610 --> 00:18:45.250 ancient surface. In fact, where they landed 444 00:18:45.250 --> 00:18:48.050 were more recent, uh, than the heavily 445 00:18:48.050 --> 00:18:49.450 cratered surfaces because they were 446 00:18:49.450 --> 00:18:52.210 principally in the maria, the basalt plains. 447 00:18:52.770 --> 00:18:55.010 Yeah, so maybe that 448 00:18:55.570 --> 00:18:58.090 suggests that we would have landed people on 449 00:18:58.090 --> 00:19:00.690 Europa as well, uh, because I think we 450 00:19:00.690 --> 00:19:01.130 probably. 451 00:19:01.130 --> 00:19:03.930 Andrew Dunkley: Yeah, we probably would because it would have 452 00:19:03.930 --> 00:19:06.730 a solid surface. There'd be places because it 453 00:19:06.730 --> 00:19:08.569 would be so close to us, we'd be able to 454 00:19:08.569 --> 00:19:11.410 examine and find the right landing points. 455 00:19:12.130 --> 00:19:15.010 Might be a bit more difficult with a moon 456 00:19:15.010 --> 00:19:17.730 that's shrouded in land gas. 457 00:19:17.890 --> 00:19:20.590 Professor Fred Watson: Yeah, yeah, that's right. And 458 00:19:20.590 --> 00:19:22.830 especially in places, um, like Titan. 459 00:19:23.320 --> 00:19:26.110 Uh, I still think 460 00:19:26.110 --> 00:19:28.550 we'd have done it actually. I think, um, you 461 00:19:28.550 --> 00:19:31.510 know, the JFK's, uh, promise 462 00:19:31.510 --> 00:19:33.590 to put astronauts on the moon would have 463 00:19:33.590 --> 00:19:35.710 still held good even if it had been a very 464 00:19:35.710 --> 00:19:38.570 different place. If it had been like IO, uh, 465 00:19:38.590 --> 00:19:40.870 it might have been a different story where, 466 00:19:40.870 --> 00:19:42.510 you know, you've got the most volcanically 467 00:19:42.510 --> 00:19:45.150 active body in the entire solar system with 468 00:19:45.150 --> 00:19:47.270 stuff going off all over the place, I think 469 00:19:47.270 --> 00:19:48.990 we might have been a bit more reluctant to 470 00:19:49.230 --> 00:19:49.900 land on eo. 471 00:19:49.900 --> 00:19:52.550 Andrew Dunkley: Uh, yes, possibly. So, uh, 472 00:19:52.750 --> 00:19:54.390 it would be interesting to have something 473 00:19:54.390 --> 00:19:57.390 different. But then if we'd always 474 00:19:57.390 --> 00:19:59.990 had an ice moon, we probably would have 475 00:19:59.990 --> 00:20:02.590 caught a question from, uh, Robert asking, 476 00:20:02.590 --> 00:20:04.910 what if we had a rocky moon now. 477 00:20:04.910 --> 00:20:07.830 Professor Fred Watson: Would we look, would we have 478 00:20:07.830 --> 00:20:07.950 a. 479 00:20:07.950 --> 00:20:10.110 Andrew Dunkley: Different interpretation of the formations of 480 00:20:10.110 --> 00:20:11.950 the planets if there was a rocky moon next to 481 00:20:11.950 --> 00:20:14.860 us instead of an ice moon? Yes. Um, in an 482 00:20:14.860 --> 00:20:16.660 alternative universe, Robert, you would have 483 00:20:16.660 --> 00:20:18.700 flipped your question. Good to hear from you. 484 00:20:18.700 --> 00:20:21.100 Hope all is well in Austria. 485 00:20:21.100 --> 00:20:23.380 Our final question for this episode comes 486 00:20:23.380 --> 00:20:24.660 from Duncan. 487 00:20:25.220 --> 00:20:27.620 Duncan: Hello, Duncan here from 488 00:20:27.620 --> 00:20:29.460 Weymouth in the uk. 489 00:20:30.340 --> 00:20:32.260 Again, a quick question. 490 00:20:34.260 --> 00:20:37.100 Just looking was doing some reading and I 491 00:20:37.100 --> 00:20:39.980 noticed that Uranus and Neptune 492 00:20:39.980 --> 00:20:42.410 are often referred to as ice 493 00:20:42.410 --> 00:20:44.450 giants. Now 494 00:20:45.090 --> 00:20:47.330 given that ice is 495 00:20:48.050 --> 00:20:50.530 basically just sort of like a rock form of 496 00:20:50.690 --> 00:20:53.450 water or CO2 497 00:20:53.450 --> 00:20:56.370 or whatever else, but basically just 498 00:20:56.370 --> 00:20:59.010 a solid form of it, why are they not just 499 00:20:59.010 --> 00:21:01.730 called rock giants? Why do we 500 00:21:02.610 --> 00:21:05.610 make the definition of ice rather than just 501 00:21:05.610 --> 00:21:08.310 calling them rock? It just seems 502 00:21:08.310 --> 00:21:11.110 odd because the little planets in the 503 00:21:11.110 --> 00:21:13.790 inner solar system are referred to as rocky 504 00:21:13.790 --> 00:21:16.590 planets. So given that they're also 505 00:21:17.230 --> 00:21:19.390 apparently rocky, why are they not called 506 00:21:19.390 --> 00:21:22.110 rocky giants? Okay, 507 00:21:22.510 --> 00:21:24.270 thank you, Bye. 508 00:21:24.990 --> 00:21:27.590 Andrew Dunkley: Thanks, Duncan. Appreciate your questions as 509 00:21:27.590 --> 00:21:30.190 always. Uh, yeah, why do we call them ice 510 00:21:30.190 --> 00:21:32.350 giants? Just for the sake of the exercise? 511 00:21:32.590 --> 00:21:35.550 Because there's gas giants and ice giants. 512 00:21:36.270 --> 00:21:39.150 Professor Fred Watson: Yeah, except one is a subset of the other. 513 00:21:39.390 --> 00:21:42.150 And so all four of the outer 514 00:21:42.150 --> 00:21:44.670 planets, Jupiter, Saturn, Neptune, sorry, 515 00:21:44.670 --> 00:21:47.390 Uranus, Neptune, they're all gas giants 516 00:21:47.710 --> 00:21:50.510 because they have, uh, high mass. 517 00:21:51.180 --> 00:21:54.140 Uh, um, you know, much more, 518 00:21:54.140 --> 00:21:56.670 um, in the case of Jupiter certainly, than, 519 00:21:56.700 --> 00:21:59.000 uh, our own planet. Um, 520 00:21:59.390 --> 00:22:02.150 the. They've got their giants, they're big, 521 00:22:02.230 --> 00:22:05.030 they've got high mass, and they don't 522 00:22:05.030 --> 00:22:07.910 have a visible surface, 523 00:22:08.070 --> 00:22:10.030 which is why they call gas giants, because 524 00:22:10.030 --> 00:22:12.150 all we see is a gassy envelope. 525 00:22:12.670 --> 00:22:15.470 Um, just to go to the last of 526 00:22:15.470 --> 00:22:17.510 Duncan's questions there, we wouldn't call 527 00:22:17.910 --> 00:22:20.230 the inner planets rocky giants because 528 00:22:20.230 --> 00:22:22.030 they're not giants. They're, uh, kind of 529 00:22:22.030 --> 00:22:23.790 normal planet size. You know, if you, if you 530 00:22:23.790 --> 00:22:25.430 think of the Earth as being your standard 531 00:22:25.430 --> 00:22:27.890 planet, then, uh, Mercury, 532 00:22:28.290 --> 00:22:31.130 Venus and Mars are similar, ah, in size. 533 00:22:31.130 --> 00:22:33.730 They're, uh, all smaller. Venus is about the 534 00:22:33.730 --> 00:22:35.730 same size, but Mercury and Mars of course are 535 00:22:35.730 --> 00:22:38.570 smaller. Uh, so it's only when you 536 00:22:38.570 --> 00:22:40.970 compare with the size of Earth that you'd 537 00:22:40.970 --> 00:22:42.850 start talking about giants because they are 538 00:22:42.850 --> 00:22:45.010 much, much bigger than Earth. And so that's 539 00:22:45.010 --> 00:22:47.670 the gas giants. So why Are, uh, 540 00:22:48.290 --> 00:22:50.610 Uranus and Neptune called ice giants 541 00:22:51.170 --> 00:22:53.380 because they have 542 00:22:53.620 --> 00:22:56.580 hazes of ice in their atmosphere. 543 00:22:57.220 --> 00:23:00.220 So. And that's the trick. It's not 544 00:23:00.220 --> 00:23:02.340 a solid surface. It's not rock. 545 00:23:03.220 --> 00:23:06.060 It's a haze. It's kind of like, uh, a dust 546 00:23:06.060 --> 00:23:08.860 of ice which permeates their atmosphere. 547 00:23:08.860 --> 00:23:11.830 And it's water ice, in fact, uh, 548 00:23:11.830 --> 00:23:14.740 mostly. Uh, so that's why they 549 00:23:14.740 --> 00:23:17.420 called ice giants, because unlike Saturn and 550 00:23:17.420 --> 00:23:20.060 Jupiter, which don't have these hazes, 551 00:23:20.190 --> 00:23:20.510 uh, 552 00:23:23.020 --> 00:23:25.820 the two outer planets, Uranus and 553 00:23:25.820 --> 00:23:28.340 Neptune, do they have ice hazes in their 554 00:23:28.340 --> 00:23:29.580 atmosphere. Hence the name. 555 00:23:30.780 --> 00:23:33.180 Andrew Dunkley: Okay. Yeah. And of course, the last episode 556 00:23:33.180 --> 00:23:35.620 we learned there wasn't much water in 557 00:23:35.620 --> 00:23:36.500 Jupiter's atmosphere. 558 00:23:36.500 --> 00:23:37.020 Professor Fred Watson: That's right. 559 00:23:38.620 --> 00:23:41.620 Andrew Dunkley: In the two outer gas giants. Yeah, 560 00:23:41.620 --> 00:23:43.140 it sounds like there is. Is that why they're 561 00:23:43.140 --> 00:23:43.900 a different color? 562 00:23:44.800 --> 00:23:47.790 Professor Fred Watson: Yes, yes, I think that's right. Um, 563 00:23:48.000 --> 00:23:50.490 and also their atmospheric constituents are, 564 00:23:50.490 --> 00:23:53.160 uh, different. They don't have the same belt 565 00:23:53.160 --> 00:23:56.000 structure that Saturn and Jupiter do. It may 566 00:23:56.000 --> 00:23:58.480 be that that's because any belts that exist 567 00:23:58.480 --> 00:24:00.320 are, uh, much lower in the atmosphere, and so 568 00:24:00.320 --> 00:24:03.160 you don't see them. Um, yeah, I 569 00:24:03.160 --> 00:24:06.000 mean, uh, there's a strong body of, 570 00:24:07.930 --> 00:24:10.160 uh, advocacy within the space 571 00:24:10.320 --> 00:24:12.130 fraternity to get 572 00:24:14.050 --> 00:24:16.890 more spacecraft out to Uranus and 573 00:24:16.890 --> 00:24:19.730 Neptune because they're the two planets about 574 00:24:19.730 --> 00:24:22.730 which we know least. Um, and, uh, will 575 00:24:22.730 --> 00:24:23.890 be good to know more. 576 00:24:24.610 --> 00:24:25.090 Duncan: Yeah. 577 00:24:25.890 --> 00:24:27.690 Andrew Dunkley: Well, if you sit down in snow for long 578 00:24:27.690 --> 00:24:30.130 enough, Uranus turns into a nice giant. 579 00:24:32.050 --> 00:24:33.170 I couldn't help it. 580 00:24:33.170 --> 00:24:35.010 Professor Fred Watson: Sorry. Uh, yeah, 581 00:24:36.610 --> 00:24:39.170 which is why we call it Uranus in politics. 582 00:24:39.570 --> 00:24:40.610 I know, I know. 583 00:24:41.010 --> 00:24:43.170 Andrew Dunkley: Yeah. But it's just a joke. 584 00:24:43.390 --> 00:24:43.950 Duncan: Got to tell. 585 00:24:43.950 --> 00:24:44.590 Professor Fred Watson: It's just. 586 00:24:44.670 --> 00:24:45.550 Andrew Dunkley: You have to. 587 00:24:46.510 --> 00:24:49.350 Professor Fred Watson: Yes, I. I blame Johannes Boda, who is 588 00:24:49.350 --> 00:24:52.070 the person who chose the name. He's fine in 589 00:24:52.070 --> 00:24:54.910 German. There's nothing wrong with 590 00:24:55.070 --> 00:24:57.990 German ruins. All the jokes 591 00:24:57.990 --> 00:24:58.270 there. 592 00:24:59.790 --> 00:25:01.830 Andrew Dunkley: All right, so, yes, uh, they're ice giants 593 00:25:01.830 --> 00:25:03.270 for a very good reason, Duncan. Because 594 00:25:03.270 --> 00:25:05.310 they've got ice in them in, uh, the 595 00:25:05.310 --> 00:25:07.070 atmosphere. But, uh, technically speaking, 596 00:25:07.070 --> 00:25:09.710 they are, in fact, gas giants. But, yes, 597 00:25:10.130 --> 00:25:11.890 you differentiate them because of their 598 00:25:12.210 --> 00:25:14.490 substantially different atmospheres. There 599 00:25:14.490 --> 00:25:14.930 you are. 600 00:25:15.010 --> 00:25:15.850 Professor Fred Watson: Thanks, Duncan. 601 00:25:15.850 --> 00:25:17.370 Andrew Dunkley: Great to hear from you. Great to, uh, hear 602 00:25:17.370 --> 00:25:18.970 from everybody. Thanks for sending in your 603 00:25:18.970 --> 00:25:20.570 questions. Don't forget, you can send in 604 00:25:20.570 --> 00:25:22.410 questions via our website, spacenuts 605 00:25:22.410 --> 00:25:25.410 podcast.com spacenuts IO 606 00:25:25.410 --> 00:25:26.970 and all you have to do is click on the 607 00:25:26.970 --> 00:25:29.290 various links on the right hand side, send us 608 00:25:29.290 --> 00:25:31.250 your question. That's audio questions only. 609 00:25:31.810 --> 00:25:33.850 Uh, or you can send us text and audio 610 00:25:33.850 --> 00:25:36.730 questions via the AMA M tab up the top. It's 611 00:25:36.730 --> 00:25:38.450 your choice. Don't forget to tell us who you 612 00:25:38.450 --> 00:25:39.610 are and where you're from and have a look 613 00:25:39.610 --> 00:25:42.110 around while you're on our website or join 614 00:25:42.110 --> 00:25:44.350 our media social, uh, media platforms, 615 00:25:44.350 --> 00:25:46.630 Facebook, Instagram, YouTube Music, where you 616 00:25:46.630 --> 00:25:49.430 can subscribe just by pressing the subscribe 617 00:25:49.430 --> 00:25:52.390 button below. Which, yes, it's down 618 00:25:52.390 --> 00:25:55.030 there somewhere. I don't know one of those 619 00:25:55.030 --> 00:25:57.630 places. Fred, as always, thank you so much. 620 00:25:58.270 --> 00:25:59.950 Professor Fred Watson: Pleasure, Andrew. See you soon. 621 00:26:00.270 --> 00:26:03.150 Andrew Dunkley: Okay. Fred Watson, astronomer at large. We'll 622 00:26:03.150 --> 00:26:04.950 catch him on the next episode of Space Nuts. 623 00:26:04.950 --> 00:26:07.190 We might catch Huw then as well because, um, 624 00:26:09.310 --> 00:26:11.830 not here today. Didn't even call in sick. I 625 00:26:11.830 --> 00:26:14.270 need a note. And from me, Andrew Dunkley. 626 00:26:14.270 --> 00:26:16.150 Thanks very much for your company. We'll see 627 00:26:16.150 --> 00:26:18.230 you again soon on the next episode of Space 628 00:26:18.230 --> 00:26:19.390 Nuts. Bye. Bye. 629 00:26:20.590 --> 00:26:22.790 Generic: You've been listening to the Space Nuts 630 00:26:22.790 --> 00:26:25.790 podcast, available at 631 00:26:25.790 --> 00:26:27.790 Apple Podcasts, Spotify, 632 00:26:27.950 --> 00:26:30.710 iHeartRadio or your favorite podcast 633 00:26:30.710 --> 00:26:33.070 player. You can also stream on demand at 634 00:26:33.070 --> 00:26:35.910 bitesz.com This has been another quality 635 00:26:35.910 --> 00:26:38.150 podcast production from bitesz.com