WEBVTT 0 00:00:00.000 --> 00:00:02.120 Andrew Dunkley: Hi there. Thanks for joining us. This is a Q 1 00:00:02.120 --> 00:00:05.080 and A edition of Space Nuts. Not only do 2 00:00:05.080 --> 00:00:07.160 we talk astronomy and space science, we 3 00:00:07.160 --> 00:00:09.040 pretend to answer questions from our 4 00:00:09.520 --> 00:00:11.600 wonderful, uh, audience. We've got a bunch 5 00:00:11.600 --> 00:00:14.320 today. Bill, uh, is asking about small 6 00:00:14.480 --> 00:00:16.480 bodies in solar systems. 7 00:00:17.200 --> 00:00:19.080 I don't think that's got anything to do with 8 00:00:19.080 --> 00:00:21.520 weight loss, but we'll see. Uh, Peter is 9 00:00:21.520 --> 00:00:23.560 asking about, uh, leaving something behind 10 00:00:23.560 --> 00:00:25.760 that could survive the destruction of Earth. 11 00:00:26.670 --> 00:00:29.310 Wow, that's a what if question. Tiny moons 12 00:00:29.310 --> 00:00:32.270 and giant planets and issues with a 13 00:00:32.270 --> 00:00:34.820 giant space station. Those are, uh, 14 00:00:34.830 --> 00:00:36.910 questions we will endeavour to answer today 15 00:00:36.990 --> 00:00:39.150 on this edition of Space Nuts. 16 00:00:39.310 --> 00:00:41.710 Professor Fred Watson: 15 seconds. Guidance is internal. 17 00:00:42.109 --> 00:00:44.670 10, 9. Ignition 18 00:00:44.750 --> 00:00:47.481 sequence start. Space Nuts. 5, 4, 19 00:00:47.550 --> 00:00:50.224 3, 2. 1. 2, 3, 4, 5, 5, 20 00:00:50.292 --> 00:00:52.910 4, 3, 2, 1. Space Nuts 21 00:00:52.910 --> 00:00:54.750 astronauts report it feels good. 22 00:00:56.140 --> 00:00:58.020 Andrew Dunkley: And with us again is Professor Fred Watson 23 00:00:58.020 --> 00:01:00.100 Watson, um, astronomer at large. Hello, 24 00:01:00.100 --> 00:01:00.460 Fred Watson. 25 00:01:00.860 --> 00:01:03.220 Professor Fred Watson: Hello, Andrew. Uh, fancy seeing you here. 26 00:01:03.220 --> 00:01:05.180 Andrew Dunkley: Yes, unusual. Both wearing black. 27 00:01:05.500 --> 00:01:07.380 Professor Fred Watson: Is it black? Uh, 28 00:01:08.620 --> 00:01:09.500 it is, yeah. 29 00:01:11.740 --> 00:01:14.740 It's the, um, this is the, the shirt 30 00:01:14.740 --> 00:01:17.660 that if I have Jordy sitting on my lap, you, 31 00:01:17.740 --> 00:01:20.260 you can't see him at all because it's exactly 32 00:01:20.260 --> 00:01:22.220 the same colour as he is. Jet black. 33 00:01:23.190 --> 00:01:25.180 Andrew Dunkley: Uh, that'll make a good Instagram photo. 34 00:01:25.500 --> 00:01:28.480 Professor Fred Watson: Well, it might do. Just two eyes poking 35 00:01:28.480 --> 00:01:28.760 out. 36 00:01:29.800 --> 00:01:32.440 Andrew Dunkley: Now, um, we've got a lot to get through, so 37 00:01:32.440 --> 00:01:34.720 we'll start straight away with, uh, a 38 00:01:34.720 --> 00:01:36.840 question that comes from Bill 39 00:01:37.800 --> 00:01:40.240 and he asks if small bodies in the solar 40 00:01:40.240 --> 00:01:43.119 system formed by accretion of fine dust 41 00:01:43.119 --> 00:01:46.040 and gas, why are they not all 42 00:01:46.120 --> 00:01:48.800 fluffy, low gravity powder 43 00:01:48.800 --> 00:01:51.680 puffs? Um, we're 44 00:01:51.680 --> 00:01:54.640 all dense stony. Uh, or, uh, were 45 00:01:54.640 --> 00:01:56.960 all dense stony or metallic objects 46 00:01:56.960 --> 00:01:59.070 originally part of a larger body that could, 47 00:01:59.140 --> 00:02:01.860 could differentiate under, uh, decent 48 00:02:01.860 --> 00:02:04.860 gravity levels, then were smashed to small 49 00:02:04.860 --> 00:02:07.300 pieces in collisions. Uh, thanks for the 50 00:02:07.300 --> 00:02:09.380 great podcasts. Uh, that comes from Bill. 51 00:02:10.040 --> 00:02:12.180 Um, so, yeah, why isn't everything 52 00:02:12.580 --> 00:02:13.300 puffy? 53 00:02:14.380 --> 00:02:17.220 Professor Fred Watson: Um, I think it was to start with. Well, there 54 00:02:17.220 --> 00:02:18.900 you go. Yeah. So, 55 00:02:20.740 --> 00:02:22.260 um, people often say, 56 00:02:23.620 --> 00:02:26.620 people who should know better often say that 57 00:02:26.620 --> 00:02:28.620 if you want to know how planet formation 58 00:02:28.620 --> 00:02:30.660 starts, look under your bed because 59 00:02:32.400 --> 00:02:34.480 the bits of fluff that you tend to find under 60 00:02:34.480 --> 00:02:37.120 your bed are, uh, made of dust 61 00:02:37.120 --> 00:02:39.600 sticking together, uh, usually by 62 00:02:39.600 --> 00:02:42.280 electrostatic forces, which we think played a 63 00:02:42.280 --> 00:02:45.280 part in the early, uh, evolution of planets. 64 00:02:45.800 --> 00:02:48.640 Uh, these things stick together. You build 65 00:02:48.640 --> 00:02:51.540 up bigger and bigger fluff balls. Um, 66 00:02:51.920 --> 00:02:54.640 and eventually the 67 00:02:54.640 --> 00:02:57.600 fluff balls, because. Exactly, 68 00:02:57.860 --> 00:03:00.280 um, as Bill says, they do tend to collide 69 00:03:00.280 --> 00:03:02.600 with one another. We're now talking about a 70 00:03:02.600 --> 00:03:05.300 very, a very, very 71 00:03:05.300 --> 00:03:07.580 dense, dusty environment. We're talking about 72 00:03:07.580 --> 00:03:10.580 the protoplanetary disc that Surrounded the 73 00:03:10.580 --> 00:03:13.420 sun. Uh, very dusty place 74 00:03:13.580 --> 00:03:16.580 with lots of, um, basically 75 00:03:16.580 --> 00:03:19.420 lots of capacity for uh, dust 76 00:03:19.420 --> 00:03:22.340 fluff balls to build up to have bigger and 77 00:03:22.340 --> 00:03:24.540 bigger sizes. Eventually 78 00:03:25.100 --> 00:03:27.860 these various forces uh, will 79 00:03:27.860 --> 00:03:30.660 cause the dust balls to sort of 80 00:03:30.660 --> 00:03:33.260 collapse. Probably collisions will contribute 81 00:03:33.260 --> 00:03:36.200 to, um, by that I mean that they 82 00:03:36.520 --> 00:03:39.360 tend to lose their porosity. In other words, 83 00:03:39.360 --> 00:03:41.560 they become more solid. 84 00:03:41.860 --> 00:03:44.760 Um, now having said that, there are objects 85 00:03:44.760 --> 00:03:47.280 in space that we know are very 86 00:03:47.280 --> 00:03:47.880 porous. 87 00:03:48.220 --> 00:03:51.160 Andrew Dunkley: Um, well we've found powder puff planets, 88 00:03:51.160 --> 00:03:51.720 haven't we? 89 00:03:52.040 --> 00:03:54.680 Professor Fred Watson: Yes, that's right. Uh, yes, almost exactly 90 00:03:55.320 --> 00:03:57.600 a good description of them. I'm just thinking 91 00:03:57.600 --> 00:04:00.250 more nearer to home though. Um, uh, 92 00:04:00.620 --> 00:04:03.570 uh, Phobos, the larger moon of Mars, 93 00:04:03.810 --> 00:04:06.690 is thought to have a composition a bit like 94 00:04:07.060 --> 00:04:09.250 um. God, the word's gone. 95 00:04:09.740 --> 00:04:12.130 Uh, stuff that forms when 96 00:04:12.130 --> 00:04:14.530 eruptions, um, take place 97 00:04:14.530 --> 00:04:15.170 underwater. 98 00:04:15.170 --> 00:04:15.970 Andrew Dunkley: Like a honeycomb. 99 00:04:16.450 --> 00:04:19.450 Professor Fred Watson: Yes, um, but it's got a word. Oh, that's 100 00:04:19.450 --> 00:04:21.130 ridiculous. When you get to a certain age, 101 00:04:21.130 --> 00:04:24.090 words just disappear. It'll come to me 102 00:04:24.090 --> 00:04:27.090 in a minute. I know. Uh, but yeah, 103 00:04:27.090 --> 00:04:29.170 the stuff that floats on the water 104 00:04:29.890 --> 00:04:32.200 underground eruption. Pumice. The very word. 105 00:04:32.430 --> 00:04:33.950 That's what I was looking for. Thank you. 106 00:04:34.110 --> 00:04:36.710 Thank you, Andrew. So pumice is, you know, 107 00:04:36.710 --> 00:04:39.390 it's porous, it's a stony 108 00:04:39.390 --> 00:04:42.110 structure, uh, that's got a lot of gaps in it 109 00:04:42.110 --> 00:04:44.390 and I guess that might well be an 110 00:04:44.390 --> 00:04:46.550 intermediate structure of many of these 111 00:04:46.550 --> 00:04:49.550 objects. Ah, as I said, Phobos is like 112 00:04:49.550 --> 00:04:52.470 that, um, one of Saturn's moons and I 113 00:04:52.470 --> 00:04:54.590 can't remember which one it is, it's the one 114 00:04:54.590 --> 00:04:56.470 shaped like a potato. That'll probably come 115 00:04:56.470 --> 00:04:59.070 to me in a minute as well. Uh, it's also 116 00:04:59.230 --> 00:05:01.910 got that sort of structure. Um, so 117 00:05:01.910 --> 00:05:03.510 maybe, you know, when you get things like 118 00:05:03.510 --> 00:05:05.930 that colour colliding, uh, then 119 00:05:06.890 --> 00:05:09.410 and building up in size, then you're 120 00:05:09.410 --> 00:05:11.450 eventually going to get to this situation 121 00:05:12.090 --> 00:05:14.970 where gravity takes over, uh, and it 122 00:05:14.970 --> 00:05:17.690 pulls um, these low 123 00:05:18.090 --> 00:05:20.730 density materials into something 124 00:05:20.810 --> 00:05:21.690 more solid. 125 00:05:22.240 --> 00:05:24.890 Andrew Dunkley: Um, is it a malthea, A mouth? 126 00:05:25.930 --> 00:05:28.090 Professor Fred Watson: No, uh, it's one with a better known name. 127 00:05:28.700 --> 00:05:31.050 Ah. It's very highly cratered and 128 00:05:31.770 --> 00:05:32.970 potato shaped. 129 00:05:33.160 --> 00:05:33.620 Andrew Dunkley: Ah, okay. 130 00:05:34.180 --> 00:05:36.660 Professor Fred Watson: It's uh, yeah, it's one of the most cratered 131 00:05:36.660 --> 00:05:38.900 objects in the, in the solar system. I'm 132 00:05:38.900 --> 00:05:40.180 annoyed. I can't remember it. It's 133 00:05:40.180 --> 00:05:43.100 ridiculous. I was getting too 134 00:05:43.100 --> 00:05:44.100 old for this, Andrew. 135 00:05:44.100 --> 00:05:45.060 Andrew Dunkley: Oh no you're not. 136 00:05:45.140 --> 00:05:46.220 Professor Fred Watson: No, no, maybe I'm not. 137 00:05:46.220 --> 00:05:47.940 Andrew Dunkley: No, it keeps your brain active. 138 00:05:48.260 --> 00:05:51.220 Professor Fred Watson: Well, except it's demonstrating quite 139 00:05:51.220 --> 00:05:53.740 clearly, uh, that the memory banks are 140 00:05:53.740 --> 00:05:56.220 disappearing. Anyway, um, it'll come to me, 141 00:05:56.220 --> 00:05:58.380 as I said, in a minute. It's not Enceladus, 142 00:05:58.380 --> 00:06:01.150 but it's something like that. Uh, so, uh, 143 00:06:01.860 --> 00:06:04.060 if you've got, you know, gravity taking over, 144 00:06:04.060 --> 00:06:06.920 then you' to get basically solid rock 145 00:06:06.920 --> 00:06:09.790 emerging from that. Uh, uh, 146 00:06:10.160 --> 00:06:12.880 as Bill says, dense, stony or metallic 147 00:06:12.880 --> 00:06:14.560 objects, that's basically what they turn 148 00:06:14.560 --> 00:06:17.250 into. And then they collide. Uh, 149 00:06:18.200 --> 00:06:20.520 um, the larger objects are differentiated. 150 00:06:20.520 --> 00:06:22.120 That means the heavy stuff sinks to the 151 00:06:22.120 --> 00:06:24.680 middle. Uh, exactly as Bill says, but they 152 00:06:24.680 --> 00:06:26.960 collide. And that's how you can get stony 153 00:06:26.960 --> 00:06:29.720 meteorites or metallic 154 00:06:29.720 --> 00:06:31.880 meteorites because the metal tends to sink 155 00:06:31.880 --> 00:06:34.690 mostly, uh, to the middle. So I 156 00:06:34.690 --> 00:06:37.410 think, um, it is a natural process, but it's 157 00:06:37.410 --> 00:06:40.290 one in a way it's counterintuitive to us. You 158 00:06:40.290 --> 00:06:42.850 know, how do you get from a dust, a fluff 159 00:06:42.850 --> 00:06:45.050 ball under your bed. How do you get from that 160 00:06:45.050 --> 00:06:46.810 to a stone to a rock? 161 00:06:47.210 --> 00:06:47.850 Andrew Dunkley: Gravity. 162 00:06:48.650 --> 00:06:50.530 Professor Fred Watson: Yes, that's right, gravity. But over a long 163 00:06:50.530 --> 00:06:53.130 period of time. Uh, and probably heat as 164 00:06:53.130 --> 00:06:55.170 well. You know, you've got heat processes 165 00:06:55.170 --> 00:06:57.340 coming into this too. So, um, 166 00:06:57.930 --> 00:07:00.570 uh, I, uh, 167 00:07:00.570 --> 00:07:03.360 think uh, what um, 168 00:07:03.450 --> 00:07:06.270 Bill's saying is right. If the small bodies 169 00:07:06.270 --> 00:07:08.670 in the solar system formed by accretion of 170 00:07:08.670 --> 00:07:10.550 fine dust and gas, why are they not all 171 00:07:10.870 --> 00:07:13.070 fluffy, low gravity powder puffs? Well, some 172 00:07:13.070 --> 00:07:15.550 of them are and that's. Perhaps you could 173 00:07:15.550 --> 00:07:18.230 describe them like um, 174 00:07:18.230 --> 00:07:21.150 Phobos. Uh, perhaps he could describe them as 175 00:07:21.150 --> 00:07:23.990 unevolved. They haven't evolved much. 176 00:07:23.990 --> 00:07:26.470 I think it might be Hyperion, the one I'm 177 00:07:26.470 --> 00:07:26.910 thinking of. 178 00:07:26.910 --> 00:07:27.430 Andrew Dunkley: Okay. 179 00:07:28.070 --> 00:07:29.990 Professor Fred Watson: I think it might be Hyperion. I'll have a 180 00:07:29.990 --> 00:07:32.980 look, Have a look, See if it's um, shaped 181 00:07:32.980 --> 00:07:35.340 like a potato and got lots of graters on it. 182 00:07:35.340 --> 00:07:36.820 Andrew Dunkley: Yeah. Well, there's got to be a photo of it 183 00:07:36.820 --> 00:07:37.820 somewhere. Yes, it is. 184 00:07:38.220 --> 00:07:38.660 Professor Fred Watson: Yeah. 185 00:07:38.660 --> 00:07:38.860 Andrew Dunkley: Yeah. 186 00:07:38.860 --> 00:07:39.340 Professor Fred Watson: Okay, good. 187 00:07:39.340 --> 00:07:41.520 Andrew Dunkley: It's got, it's got that big, um. 188 00:07:42.220 --> 00:07:43.940 It's got a massive crater in it actually. 189 00:07:43.940 --> 00:07:46.380 Professor Fred Watson: Yeah. Yes, yes. Yeah, yeah. 190 00:07:46.380 --> 00:07:47.980 So, um, so these are you got 191 00:07:47.980 --> 00:07:48.860 Andrew Dunkley: there in the end, Fred Watson. 192 00:07:48.860 --> 00:07:51.740 Professor Fred Watson: In the end? Yeah, it's. Yes. It's just the 193 00:07:51.740 --> 00:07:53.660 processing speeds down a bit. I must be 194 00:07:53.660 --> 00:07:56.300 offline or something like that. Probably need 195 00:07:56.300 --> 00:07:59.100 a reboot. God, don't say that. Might 196 00:07:59.100 --> 00:07:59.980 never come back. 197 00:08:01.100 --> 00:08:02.820 Andrew Dunkley: Well, that's happened. My car did that while 198 00:08:02.820 --> 00:08:05.780 we were away. Uh, came home 199 00:08:05.780 --> 00:08:08.100 and to, uh, to, to stop falling asleep. We 200 00:08:08.100 --> 00:08:09.820 decided we'd go and do the groceries straight 201 00:08:09.820 --> 00:08:11.260 after getting off a long haul flight. 202 00:08:11.260 --> 00:08:12.180 Professor Fred Watson: Oh, yes. Yeah. 203 00:08:12.740 --> 00:08:14.340 Andrew Dunkley: And the car wouldn't start. 204 00:08:15.620 --> 00:08:17.220 Yeah, the battery died, so. 205 00:08:17.220 --> 00:08:18.380 Professor Fred Watson: Oh, the battery died. 206 00:08:18.380 --> 00:08:21.020 Andrew Dunkley: Yeah. That's another 315 bucks. Thank you 207 00:08:21.020 --> 00:08:21.460 very much. 208 00:08:22.100 --> 00:08:22.580 Professor Fred Watson: Yes. 209 00:08:22.580 --> 00:08:25.420 Andrew Dunkley: Anyway, it happens. It was four years. It 210 00:08:25.420 --> 00:08:26.180 lasted four years. 211 00:08:26.180 --> 00:08:27.740 Professor Fred Watson: Oh, that's all right. That's about as long as 212 00:08:27.740 --> 00:08:28.700 you get from a battery. 213 00:08:28.700 --> 00:08:31.500 Andrew Dunkley: Yes, it is indeed. But thanks, Bill, for the 214 00:08:31.500 --> 00:08:33.060 question. Uh, I think you answered it 215 00:08:33.060 --> 00:08:35.840 yourself, but, um, y, uh, although 216 00:08:35.920 --> 00:08:37.920 if you're, um, someone like me, 217 00:08:38.130 --> 00:08:40.890 um, and you don't clean under the bed, uh, 218 00:08:41.840 --> 00:08:43.440 you can watch planets evolve. 219 00:08:44.720 --> 00:08:45.920 That's what's happening. 220 00:08:46.080 --> 00:08:47.040 Professor Fred Watson: Yep, you can. 221 00:08:47.600 --> 00:08:48.760 Andrew Dunkley: All right, uh, thanks, Bill. 222 00:08:48.760 --> 00:08:51.360 Our next question, uh, is 223 00:08:51.440 --> 00:08:53.200 coming from Peter. 224 00:08:53.760 --> 00:08:56.600 Speaker C: Hello, this is Peter in Lamington 225 00:08:56.600 --> 00:08:59.440 Spa. And I want to know 226 00:09:00.000 --> 00:09:02.410 what would it take for 227 00:09:02.410 --> 00:09:04.890 humans to 228 00:09:05.770 --> 00:09:08.730 make something that will survive 229 00:09:09.210 --> 00:09:11.050 the destruction of Earth 230 00:09:11.930 --> 00:09:14.650 and then potentially be incorporated 231 00:09:15.130 --> 00:09:18.010 into a new planet when all the bits of Earth 232 00:09:18.330 --> 00:09:20.770 become a different planet and sometime in the 233 00:09:20.770 --> 00:09:22.970 future, Is it possible? 234 00:09:24.730 --> 00:09:27.610 Andrew Dunkley: Have a good evening. Thank you, Peter. That's 235 00:09:27.610 --> 00:09:30.250 a what if question. Uh, yeah, I wonder. 236 00:09:30.650 --> 00:09:33.320 That's a very. It's a long haul science 237 00:09:33.320 --> 00:09:36.040 fiction situation. You build something 238 00:09:36.200 --> 00:09:38.160 that will survive the destruction of Earth 239 00:09:38.160 --> 00:09:40.760 and then somehow the planet reconstitutes 240 00:09:40.760 --> 00:09:43.520 itself and billions of years later there's an 241 00:09:43.520 --> 00:09:45.840 intelligent race living on the planet and 242 00:09:45.840 --> 00:09:47.720 they go, oh, hello. What's all this then? 243 00:09:48.840 --> 00:09:51.480 Professor Fred Watson: This is some leftover of humankind? Yeah, 244 00:09:51.720 --> 00:09:52.760 whatever they were. 245 00:09:53.000 --> 00:09:55.920 Andrew Dunkley: There was a TV series that I watched many 246 00:09:55.920 --> 00:09:58.850 years ago called Childhood's End, and 247 00:09:59.330 --> 00:10:01.410 it was about the destruction of Earth. And 248 00:10:02.130 --> 00:10:04.770 before it, before it was destroyed, 249 00:10:05.320 --> 00:10:08.130 um, the humans asked the aliens 250 00:10:08.130 --> 00:10:11.100 that rescued the children, basically, um, 251 00:10:11.570 --> 00:10:13.690 can we just leave something behind so they 252 00:10:13.690 --> 00:10:15.570 know we were here? So they left. Music. 253 00:10:17.330 --> 00:10:20.170 Professor Fred Watson: Lovely. I like that. Yes, I like that very 254 00:10:20.170 --> 00:10:20.410 much. 255 00:10:20.410 --> 00:10:22.010 Andrew Dunkley: I just spoiled the whole thing too, by the 256 00:10:22.010 --> 00:10:22.290 way. 257 00:10:22.820 --> 00:10:24.440 Professor Fred Watson: Um, I don't think you did really, uh, 258 00:10:25.890 --> 00:10:28.770 because. Yes, that's a kind of concept, isn't 259 00:10:28.770 --> 00:10:31.710 it, that you're leaving behind? Uh, and 260 00:10:32.350 --> 00:10:35.150 my mind, when I read Peter's question or 261 00:10:35.150 --> 00:10:37.630 heard Peter's question, went to 262 00:10:38.750 --> 00:10:41.590 more concrete things, not necessarily made of 263 00:10:41.590 --> 00:10:42.110 concrete. 264 00:10:43.150 --> 00:10:44.430 Andrew Dunkley: I was about to say that. 265 00:10:46.110 --> 00:10:48.950 Professor Fred Watson: But in a sense we've already done it, Andrew, 266 00:10:48.950 --> 00:10:50.990 because there are five 267 00:10:52.670 --> 00:10:55.330 little spacecraft which are, 268 00:10:55.330 --> 00:10:58.070 ah, absolute, um, 269 00:10:59.090 --> 00:11:01.750 uh, monuments to humanity leaving the 270 00:11:01.750 --> 00:11:04.710 solar system, um, way, way beyond 271 00:11:04.710 --> 00:11:07.430 the orbit of Earth. Voyager 1 is 272 00:11:07.430 --> 00:11:10.230 probably beyond. Actually, 273 00:11:10.230 --> 00:11:13.230 that's not quite true. I, uh, was going to 274 00:11:13.230 --> 00:11:15.310 say beyond the limits of the sun. When it 275 00:11:15.310 --> 00:11:17.670 turns into a red giant star, um, 276 00:11:19.390 --> 00:11:21.950 Voyager 1 will probably survive, 277 00:11:22.620 --> 00:11:25.270 um, the red giant phase of 278 00:11:25.270 --> 00:11:28.070 our sun, uh, which will take place in 279 00:11:28.070 --> 00:11:30.920 a few billion years, three or four 280 00:11:30.920 --> 00:11:33.760 billion years. Um, it'll survive that, 281 00:11:33.760 --> 00:11:36.720 but might not survive the formation of 282 00:11:36.720 --> 00:11:39.720 a planetary nebula when you've got hot gas 283 00:11:39.720 --> 00:11:42.640 coming off the, uh, being puffed off the 284 00:11:42.640 --> 00:11:44.679 surface of the red Giant. It might actually 285 00:11:44.760 --> 00:11:47.120 melt in that because it's because planetary 286 00:11:47.120 --> 00:11:49.240 nebulae get to be light years in diameter. 287 00:11:49.640 --> 00:11:52.200 Uh, our Voyager, uh, is only, well, it's 288 00:11:52.200 --> 00:11:54.800 nearly a light day away. Um, on the other 289 00:11:54.800 --> 00:11:57.320 hand, we've got 3 or 4 billion years to play 290 00:11:57.320 --> 00:11:59.040 with because the sun's not going to do 291 00:11:59.040 --> 00:12:01.850 anything really nasty, um, within that 292 00:12:01.850 --> 00:12:04.050 time. So yes, Voyager 1 will be well out of 293 00:12:04.050 --> 00:12:06.890 the way, probably will survive the 294 00:12:06.890 --> 00:12:09.610 eventual evolution, um, and 295 00:12:11.350 --> 00:12:13.850 uh, final evolutionary stages of the sun when 296 00:12:13.850 --> 00:12:16.730 it actually turns into a white dwarf star. So 297 00:12:16.730 --> 00:12:19.690 yes, uh, those spacecraft, Voyager 298 00:12:19.690 --> 00:12:22.490 1, Voyager 2, Pioneer 10, Pioneer 11, 299 00:12:22.490 --> 00:12:25.170 is that right? And New Horizons, 300 00:12:25.170 --> 00:12:27.330 they're the five that are leaving the solar 301 00:12:27.330 --> 00:12:30.010 system which will probably outlive humanity. 302 00:12:30.330 --> 00:12:32.470 Andrew Dunkley: They probably won't. They probably won't be 303 00:12:32.470 --> 00:12:32.950 the last. 304 00:12:33.670 --> 00:12:35.310 Professor Fred Watson: They won't be the last. No, I think that's 305 00:12:35.310 --> 00:12:36.790 right. Uh, but, 306 00:12:37.010 --> 00:12:39.990 um, I mean 307 00:12:40.070 --> 00:12:43.060 the idea of, um, the Earth, uh, 308 00:12:43.390 --> 00:12:46.310 being destroyed, the 309 00:12:46.310 --> 00:12:48.270 kinds of things that might destroy the Earth, 310 00:12:48.270 --> 00:12:50.870 ah, are first of all, that eventual 311 00:12:50.870 --> 00:12:53.310 evolution of the sun to a red giant star that 312 00:12:53.310 --> 00:12:55.990 will almost certainly melt the Earth because 313 00:12:57.110 --> 00:13:00.110 the Sun's, um, surface, put 314 00:13:00.110 --> 00:13:03.070 it that way, will be, um, a quarter of a 315 00:13:03.070 --> 00:13:04.870 mile from the Earth. And we might be on the 316 00:13:04.870 --> 00:13:07.390 inside of, uh, could even, 317 00:13:07.450 --> 00:13:09.770 uh, overtake the planet Mars. Uh, 318 00:13:10.270 --> 00:13:12.910 so it's hard to imagine how you'd rebuild 319 00:13:13.230 --> 00:13:15.870 the Earth, uh, from the debris that is really 320 00:13:15.870 --> 00:13:17.910 just molecules, uh, because it'll have been 321 00:13:17.910 --> 00:13:20.720 vaporised. Um, so I think, uh, 322 00:13:21.470 --> 00:13:23.150 in addressing this question, you've really 323 00:13:23.150 --> 00:13:26.030 got to think about things that uh, have 324 00:13:26.030 --> 00:13:28.830 left the Earth. And that really basically 325 00:13:28.830 --> 00:13:31.670 pushes your mind to spacecraft. There are 326 00:13:31.670 --> 00:13:34.110 some spacecraft which are, uh, in orbit 327 00:13:34.110 --> 00:13:36.390 around the sun, uh, which 328 00:13:36.870 --> 00:13:39.430 are spacecraft that have been sent 329 00:13:39.750 --> 00:13:42.430 exploring the inner solar system. Mostly 330 00:13:42.430 --> 00:13:44.550 these days we try and get rid of them. We 331 00:13:44.550 --> 00:13:47.390 plunge them, uh, into either, uh, Jupiter or 332 00:13:47.390 --> 00:13:49.190 Saturn. Jupiter in the case of Galileo, 333 00:13:49.190 --> 00:13:51.830 Saturn in the case of Cassini. Uh, those 334 00:13:52.550 --> 00:13:55.390 spacecraft were destroyed purposely so that 335 00:13:55.390 --> 00:13:58.030 they didn't accidentally land on one of the 336 00:13:58.030 --> 00:14:00.650 moons of Jupiter or Saturn and leave microbes 337 00:14:00.650 --> 00:14:03.530 behind. Um, so you're really talking about 338 00:14:03.530 --> 00:14:05.170 something that's left the solar system. And 339 00:14:05.170 --> 00:14:07.970 that leaves those five spacecraft 340 00:14:07.970 --> 00:14:09.970 I've mentioned. And they definitely will 341 00:14:09.970 --> 00:14:11.250 outlast humankind. 342 00:14:11.890 --> 00:14:14.690 Andrew Dunkley: Okay, there you have it, Peter. Um, so we've 343 00:14:14.690 --> 00:14:17.090 already done it kind of, uh, I don't think 344 00:14:17.090 --> 00:14:19.810 you could probably build some kind 345 00:14:19.810 --> 00:14:22.210 of monolith or something that would survive 346 00:14:22.210 --> 00:14:24.930 the red giant phase of 347 00:14:25.170 --> 00:14:28.120 the sun and, and overwhelm Earth. That would 348 00:14:28.120 --> 00:14:31.000 all get destroyed, um, unless you did 349 00:14:31.000 --> 00:14:33.640 it deep down inside. But I don't even Know, 350 00:14:33.640 --> 00:14:36.520 if you could do that, I think a 351 00:14:36.520 --> 00:14:38.760 red giant phase would be pretty cataclysmic, 352 00:14:38.760 --> 00:14:39.200 wouldn't it? 353 00:14:39.760 --> 00:14:42.440 Professor Fred Watson: Yeah. Uh, yes. If your planet's being 354 00:14:42.440 --> 00:14:44.720 vaporised. Your planet's being vaporised. It 355 00:14:44.720 --> 00:14:46.320 is, yeah. 356 00:14:47.120 --> 00:14:49.800 Andrew Dunkley: Indeed. Thank you, Peter. Great to hear from 357 00:14:49.800 --> 00:14:52.760 you. I love what if questions. So, um, thanks 358 00:14:52.760 --> 00:14:55.000 for serving it up. This is Space Nuts with 359 00:14:55.000 --> 00:14:57.200 Andrew Dunkley and Professor Fred Watson 360 00:14:57.200 --> 00:14:57.840 Watson. 361 00:15:00.880 --> 00:15:03.680 Professor Fred Watson: Swiften Tranquilly Base here. 362 00:15:03.760 --> 00:15:06.160 The eagle has landed. Space Nuts. 363 00:15:06.880 --> 00:15:08.559 Andrew Dunkley: Our next question, Fred Watson, comes from 364 00:15:08.559 --> 00:15:11.520 Martin in Heswall. Heswall, is that right? 365 00:15:11.840 --> 00:15:13.200 Professor Fred Watson: Yes, Heswall. Yeah. 366 00:15:13.200 --> 00:15:15.160 Andrew Dunkley: Where's that? I'm going to guess it's the UK 367 00:15:15.160 --> 00:15:15.680 somewhere. 368 00:15:16.160 --> 00:15:19.120 Professor Fred Watson: It is indeed. It's, um, uh, on the Wirral 369 00:15:19.120 --> 00:15:21.600 Peninsula. So if you think of Liverpool, 370 00:15:21.600 --> 00:15:23.950 you've been to Liverpool? I have. And done 371 00:15:23.950 --> 00:15:24.870 the Beatles experience. 372 00:15:24.950 --> 00:15:25.350 Andrew Dunkley: Yes. 373 00:15:25.350 --> 00:15:27.470 Professor Fred Watson: Is that right? Yes. Yeah. Well, across the 374 00:15:27.470 --> 00:15:29.830 River Mersey from Liverpool is the Wirral 375 00:15:29.830 --> 00:15:32.310 Peninsula and Heswall is 376 00:15:33.430 --> 00:15:35.750 one of the towns on that, um, I've said 377 00:15:35.750 --> 00:15:38.070 before, and in fact we've had listener 378 00:15:38.070 --> 00:15:40.630 comments about this, I had a girlfriend once 379 00:15:40.630 --> 00:15:43.190 who lived on the Wirral Peninsula and so I 380 00:15:43.190 --> 00:15:45.190 used to be a very regular visitor there to a 381 00:15:45.190 --> 00:15:46.950 village called Barnston, which was not that 382 00:15:46.950 --> 00:15:49.190 far from Heswall. There you are. All right. 383 00:15:49.510 --> 00:15:51.500 It's very pretty too. It's a pretty village. 384 00:15:51.810 --> 00:15:52.210 Hmm. 385 00:15:52.290 --> 00:15:55.210 Andrew Dunkley: Okay. Just wanted to know where you 386 00:15:55.210 --> 00:15:57.210 were, Martin. So thank you for that. Uh, I 387 00:15:57.210 --> 00:15:58.970 hope, uh, you'll answer this question. 388 00:15:58.970 --> 00:16:01.890 According to Wikipedia, there are, uh, now 389 00:16:02.130 --> 00:16:04.930 known to be 292 satellites, 390 00:16:05.500 --> 00:16:07.970 uh, with confirmed orbits around Saturn. 391 00:16:07.970 --> 00:16:10.370 Presumably, many of these moons are very 392 00:16:10.370 --> 00:16:13.370 small. So is there a minimum size for 393 00:16:13.370 --> 00:16:16.250 an object to be called a moon? And is 394 00:16:16.250 --> 00:16:18.210 there a minimum size for an object to 395 00:16:18.210 --> 00:16:20.850 maintain a stable orbit around a planet? 396 00:16:21.630 --> 00:16:24.550 Uh, as all the giant plan have ring 397 00:16:24.550 --> 00:16:27.550 systems, would the smaller particles just 398 00:16:27.550 --> 00:16:30.390 be absorbed into the rings? Conversely, I 399 00:16:30.390 --> 00:16:32.950 suppose that many objects could be knocked 400 00:16:32.950 --> 00:16:34.670 out of the rings to form independent 401 00:16:34.670 --> 00:16:36.430 satellites that may become permanently 402 00:16:36.430 --> 00:16:39.070 separated from the rings. Will Saturn get, 403 00:16:39.770 --> 00:16:42.190 uh, to 1,000 moons or more? 404 00:16:42.590 --> 00:16:44.990 Also, uh, can you recommend a website 405 00:16:45.310 --> 00:16:47.830 which has the latest data about, uh, the 406 00:16:47.830 --> 00:16:50.790 solar system, as the numbers vary from one 407 00:16:50.790 --> 00:16:53.630 site to the next, no doubt due to how recent 408 00:16:53.630 --> 00:16:56.450 the information is. Keep up the work. Thanks, 409 00:16:56.450 --> 00:16:58.890 Martin. Um, that's a good question because, 410 00:16:58.970 --> 00:17:01.930 yeah, we know that the ring systems, 411 00:17:02.530 --> 00:17:04.770 um, are full of dust and ice, but they've 412 00:17:04.770 --> 00:17:07.210 also got larger objects that are referred to 413 00:17:07.290 --> 00:17:08.970 regularly as moons. 414 00:17:10.470 --> 00:17:12.170 Professor Fred Watson: Um, it's interesting, this was one of the 415 00:17:12.170 --> 00:17:14.890 exact questions that came up in the Q and 416 00:17:14.890 --> 00:17:17.490 A night, the science in the pub night that we 417 00:17:17.490 --> 00:17:20.450 had on Lord Howe island at the Dark Sky 418 00:17:20.450 --> 00:17:20.890 Festival. 419 00:17:21.290 --> 00:17:23.210 Andrew Dunkley: That was Martin. He was, he was there. 420 00:17:24.610 --> 00:17:25.570 No he probably wasn't. 421 00:17:26.050 --> 00:17:28.970 Professor Fred Watson: Carry on. There was a Martin 422 00:17:28.970 --> 00:17:29.250 there. 423 00:17:30.370 --> 00:17:31.810 Andrew Dunkley: Did he have a British accent? 424 00:17:32.570 --> 00:17:35.330 Professor Fred Watson: Uh no, he's quite Australian but 425 00:17:35.330 --> 00:17:38.330 he's not from Haswell. But yeah, uh, 426 00:17:38.610 --> 00:17:41.330 but interesting coincidence to get the two 427 00:17:41.410 --> 00:17:44.290 and I don't think at the moment there is 428 00:17:45.410 --> 00:17:47.810 a uh limiting size 429 00:17:48.530 --> 00:17:51.170 to differentiate between a ring particle 430 00:17:52.380 --> 00:17:54.390 and a moon. Um 431 00:17:55.340 --> 00:17:58.260 so uh, it 432 00:17:58.260 --> 00:18:01.260 is a great question um how 433 00:18:01.260 --> 00:18:03.820 do you define a moon around a planet which is 434 00:18:03.900 --> 00:18:06.380 festooned with objects orbiting around it 435 00:18:07.259 --> 00:18:09.620 in the form of rings. So we think the rings 436 00:18:09.620 --> 00:18:12.460 of Saturn are uh the debris 437 00:18:12.540 --> 00:18:14.940 of uh probably a satellite 438 00:18:15.500 --> 00:18:18.220 that came within the Roche limit 439 00:18:18.540 --> 00:18:21.350 of the the planet. The Roche limit 440 00:18:21.350 --> 00:18:24.230 being the point at which uh a solid 441 00:18:24.230 --> 00:18:27.150 object can't actually survive within 442 00:18:27.230 --> 00:18:30.030 that distance. In other words that close to 443 00:18:30.030 --> 00:18:32.910 the planet. Um and so 444 00:18:32.910 --> 00:18:35.550 it broke up into lots of small particles. 445 00:18:36.670 --> 00:18:39.630 Probably the biggest ring sized 446 00:18:40.190 --> 00:18:42.830 sorry the biggest ring particles 447 00:18:43.690 --> 00:18:46.590 uh, uh in the region of 10 metres 448 00:18:47.830 --> 00:18:49.590 because the rings themselves are only about 449 00:18:49.590 --> 00:18:52.190 100 metres thick. Yeah it's quite 450 00:18:52.190 --> 00:18:52.950 staggering. 451 00:18:54.390 --> 00:18:57.350 Um and 250,000 kilometres 452 00:18:57.350 --> 00:19:00.230 in diameter. So yes it's quite a contrast. 453 00:19:00.830 --> 00:19:03.470 Um a sort of blade of material in space is 454 00:19:03.470 --> 00:19:05.530 the way I've always described it. Uh 455 00:19:07.190 --> 00:19:09.950 but some of the smaller satellites of 456 00:19:09.950 --> 00:19:12.910 Saturn and some of them are actually embedded 457 00:19:12.910 --> 00:19:15.710 in the ring system. Uh some of them 458 00:19:15.710 --> 00:19:17.670 are measured in 459 00:19:18.470 --> 00:19:20.790 single digit kilometres so they're not that 460 00:19:21.190 --> 00:19:23.590 much more than 461 00:19:24.310 --> 00:19:27.310 the biggest ring particles and I'm not sure 462 00:19:27.310 --> 00:19:30.150 that there is a definition between the two. 463 00:19:30.750 --> 00:19:33.030 Uh and in a sense you could say that every 464 00:19:33.590 --> 00:19:36.070 solid object within Saturn's rings is a 465 00:19:36.070 --> 00:19:38.750 satellite and so you're then talking about 466 00:19:38.750 --> 00:19:41.110 millions or maybe even billions of 467 00:19:41.510 --> 00:19:44.430 moons of Saturn. Uh it's a great 468 00:19:44.430 --> 00:19:46.510 question and one that I don't have an answer 469 00:19:46.510 --> 00:19:49.210 for and I perhaps ough who have checked it 470 00:19:49.210 --> 00:19:51.890 out in the wake of the question that came uh 471 00:19:52.290 --> 00:19:55.090 at the science in the pub science in the bolo 472 00:19:55.330 --> 00:19:58.090 on Lord Howe island the week before last when 473 00:19:58.090 --> 00:19:59.730 we did the Dark Sky Festival there. 474 00:19:59.890 --> 00:20:02.770 Andrew Dunkley: Yeah, yeah he also 475 00:20:02.770 --> 00:20:05.750 asked about uh website. Yeah ah 476 00:20:05.850 --> 00:20:08.770 well I just did a quick cheque and top uh of 477 00:20:08.770 --> 00:20:11.770 the tree is NASA for up 478 00:20:11.770 --> 00:20:14.050 to date solar system information. 479 00:20:15.250 --> 00:20:17.610 Uh yeah, uh but the other ones that you could 480 00:20:17.610 --> 00:20:19.800 try uh the sky 481 00:20:19.950 --> 00:20:22.670 mylive.com apparently is 482 00:20:22.670 --> 00:20:25.630 very highly rated um says 483 00:20:25.630 --> 00:20:27.750 it offers comprehensive information about the 484 00:20:27.750 --> 00:20:29.870 most interesting celestial objects and sets 485 00:20:29.870 --> 00:20:32.270 tools designed to support the exploration et 486 00:20:32.270 --> 00:20:34.590 cetera. Uh the planets today 487 00:20:35.790 --> 00:20:38.630 uh is also there and there's a specific uh 488 00:20:38.910 --> 00:20:41.590 NASA page that you can look up 489 00:20:41.590 --> 00:20:44.490 called Eyes on the Solar System. Um, 490 00:20:44.670 --> 00:20:47.670 and it provides a 3D solar 491 00:20:47.670 --> 00:20:50.590 scape if you like. So there's a few 492 00:20:50.590 --> 00:20:53.290 ideas if you uh, want to um, chase them 493 00:20:53.290 --> 00:20:56.010 up, Martin. But um, there'd be plenty more 494 00:20:56.010 --> 00:20:58.490 out there. There's um, just to name a few 495 00:20:58.490 --> 00:21:00.090 more, Global Solar Atlas, 496 00:21:00.790 --> 00:21:03.690 um, the NOAA homepage, 497 00:21:03.850 --> 00:21:06.330 the Space Weather Prediction homepage, um, 498 00:21:06.730 --> 00:21:09.450 and Planet Labs just to name a few. So 499 00:21:10.030 --> 00:21:13.010 um, and they're constantly being updated as 500 00:21:13.010 --> 00:21:15.930 far as I'm aware, as things change or as 501 00:21:15.930 --> 00:21:18.210 new things come to light. So might be worth 502 00:21:18.210 --> 00:21:21.000 chasing all of those up because they do seem 503 00:21:21.000 --> 00:21:23.400 to be, um, highly credentialed. Fred Watson? 504 00:21:24.280 --> 00:21:27.200 Professor Fred Watson: Yeah, I was going to say I usually go 505 00:21:27.200 --> 00:21:29.720 to NASA when I want the latest figures on 506 00:21:30.120 --> 00:21:33.000 this sort of thing. M. So, 507 00:21:33.190 --> 00:21:35.640 uh, you've confirmed that and also given a 508 00:21:35.640 --> 00:21:37.160 few other options as well, which is good. 509 00:21:37.160 --> 00:21:38.960 Andrew Dunkley: Yep, plenty to look at. There's lots of great 510 00:21:38.960 --> 00:21:41.360 sites out there. Just don't go to the ones 511 00:21:41.360 --> 00:21:43.960 that start with um, words 512 00:21:43.960 --> 00:21:45.460 starting with F and e. 513 00:21:51.370 --> 00:21:53.050 Professor Fred Watson: I was thought you were going to say don't go 514 00:21:53.050 --> 00:21:55.450 to ones that start with space and have knots 515 00:21:55.450 --> 00:21:55.930 in the. 516 00:21:57.610 --> 00:21:59.210 Andrew Dunkley: That's, that's good advice too. 517 00:21:59.210 --> 00:21:59.690 Professor Fred Watson: Yeah. 518 00:22:00.730 --> 00:22:02.210 Andrew Dunkley: Okay, thank you, Martin. 519 00:22:02.210 --> 00:22:05.210 Our final question today comes from 520 00:22:05.370 --> 00:22:06.010 Finn. 521 00:22:06.410 --> 00:22:08.770 Speaker C: Hello, Andrew and Fred Watson. It's Finn from 522 00:22:08.770 --> 00:22:11.570 NAN in the Adelaide Hills in South 523 00:22:11.570 --> 00:22:14.010 Australia. And a happy May 4th to you as 524 00:22:14.010 --> 00:22:16.540 well. I was watching a 40 year old 525 00:22:16.540 --> 00:22:18.500 documentary the other day about a space 526 00:22:18.500 --> 00:22:21.220 station orbiting a planet. And this 527 00:22:21.220 --> 00:22:24.220 space station, um, if it was to orbit 528 00:22:24.220 --> 00:22:26.180 the Earth, I would like to know how that 529 00:22:26.180 --> 00:22:28.620 would affect the orbit of our 530 00:22:28.700 --> 00:22:31.540 moon and maybe the orbit of the Earth 531 00:22:31.540 --> 00:22:34.460 around the sun. This space station being 150 532 00:22:34.460 --> 00:22:36.980 kilometres diameter with a mass of about 10 533 00:22:36.980 --> 00:22:39.980 to the 15 tonne. Um, I'd 534 00:22:39.980 --> 00:22:42.860 like to know, and if for whatever reason this 535 00:22:42.860 --> 00:22:45.500 space station happened to destroy our planet, 536 00:22:46.100 --> 00:22:48.140 how would the rest of the planets in the 537 00:22:48.140 --> 00:22:50.500 solar system be affected by that 538 00:22:50.500 --> 00:22:53.220 destruction? One last question, 539 00:22:53.640 --> 00:22:56.500 um, to you both is, um, what was the first 540 00:22:56.580 --> 00:22:57.700 animal in space? 541 00:22:58.260 --> 00:22:59.220 Andrew Dunkley: It was a dog. 542 00:22:59.540 --> 00:23:02.380 Speaker C: Ah, ah, don't think it was that. It was 543 00:23:02.380 --> 00:23:04.700 actually the cow because it jumped over the 544 00:23:04.700 --> 00:23:06.180 moon. Thank you. 545 00:23:06.980 --> 00:23:07.780 Professor Fred Watson: Dear, oh dear. 546 00:23:07.780 --> 00:23:09.900 Andrew Dunkley: Finn. That was probably one of the worst dad 547 00:23:09.900 --> 00:23:12.820 jokes I've ever heard. So, 548 00:23:13.220 --> 00:23:15.740 but you know, most welcome on this show. 549 00:23:19.340 --> 00:23:20.940 Professor Fred Watson: Yeah, it was good. It wasn't, wasn't even 550 00:23:20.940 --> 00:23:21.940 adequate that one, was it? 551 00:23:21.940 --> 00:23:22.500 Andrew Dunkley: No, it wasn't. 552 00:23:22.500 --> 00:23:23.260 Professor Fred Watson: No, no. 553 00:23:23.340 --> 00:23:26.060 Andrew Dunkley: We strive for adequacy and we didn't even 554 00:23:26.060 --> 00:23:28.860 achieve that. Thank you, Finn. 555 00:23:28.880 --> 00:23:31.500 Uh, so the substance of his question was, 556 00:23:31.760 --> 00:23:34.580 uh, you got a space Station orbiting Earth 557 00:23:34.580 --> 00:23:36.860 at 150 kilometres in 558 00:23:37.260 --> 00:23:40.260 diameter or whatever. Uh what kind 559 00:23:40.260 --> 00:23:42.900 of effect could that have on the orbit of the 560 00:23:42.900 --> 00:23:45.740 Moon? And ye 561 00:23:46.040 --> 00:23:47.520 get to the next part of the question after 562 00:23:47.520 --> 00:23:49.400 that. Could it have, would that have any. 563 00:23:49.560 --> 00:23:50.520 That's pretty big. 564 00:23:52.040 --> 00:23:54.560 Professor Fred Watson: It's well the critical thing was the mass 565 00:23:54.560 --> 00:23:57.080 which um Fin actually 566 00:23:57.640 --> 00:24:00.560 mentioned as being 10 to 567 00:24:00.560 --> 00:24:03.240 the 15 tonnes I think is what he said 568 00:24:04.330 --> 00:24:07.000 uh which is 10 to the 18 569 00:24:07.000 --> 00:24:09.480 kilogrammes. Um and 570 00:24:10.840 --> 00:24:12.920 so the bottom line is that's not enough 571 00:24:14.410 --> 00:24:17.240 uh the Earth just. Yeah, nah, ah forget it. 572 00:24:17.400 --> 00:24:20.280 So the earth's uh six times 10 to the 573 00:24:20.280 --> 00:24:22.920 24 kilogrammes. So it's 574 00:24:23.270 --> 00:24:25.960 um, what is it? It's 575 00:24:26.680 --> 00:24:29.640 six uh orders of magnitude bigger in 576 00:24:29.640 --> 00:24:32.600 mass than uh this space station 577 00:24:33.240 --> 00:24:35.320 and so the other. So 578 00:24:37.240 --> 00:24:39.600 it's certainly not going to affect the orbit 579 00:24:39.600 --> 00:24:42.530 of the ah Earth. It might perturb 580 00:24:42.530 --> 00:24:44.450 the orbit of the Moon a bit. 581 00:24:45.100 --> 00:24:47.770 Uh one of the considerations will be how far 582 00:24:47.770 --> 00:24:50.490 away is it from the 583 00:24:50.490 --> 00:24:53.410 Earth? And uh, our last question 584 00:24:53.730 --> 00:24:56.130 actually pointed to an answer to that 585 00:24:56.609 --> 00:24:59.370 and that is that if it's 150 586 00:24:59.370 --> 00:25:02.290 kilometres in diameter it has to be a long 587 00:25:02.290 --> 00:25:04.850 way away or else it's within the Roche limit 588 00:25:06.050 --> 00:25:08.050 of the Earth uh and it would just break up 589 00:25:08.130 --> 00:25:10.650 straight away. So I'm not going to guess how 590 00:25:10.650 --> 00:25:12.530 far away it has to be but it'll be a long way 591 00:25:12.830 --> 00:25:15.230 the earth if it's 150 kilometres in diameter. 592 00:25:16.020 --> 00:25:18.870 Um so that again um, basically 593 00:25:18.870 --> 00:25:21.750 mitigates any effects it might have 594 00:25:21.750 --> 00:25:23.750 on the orbital dynamics of the Earth. It 595 00:25:23.750 --> 00:25:25.230 certainly wouldn't affect the Earth's orbit 596 00:25:25.230 --> 00:25:28.150 around the Sun. Might just tweak the 597 00:25:28.150 --> 00:25:30.110 Moon's orbit around the Earth a bit. 598 00:25:30.820 --> 00:25:33.670 Uh wouldn't cause the demolition of the 599 00:25:33.670 --> 00:25:36.510 Earth. The orbits of the other planets 600 00:25:36.990 --> 00:25:39.940 wouldn't even bother to, to take any 601 00:25:39.940 --> 00:25:42.860 notice of it. Uh they are too 602 00:25:42.860 --> 00:25:45.740 stable compared with uh, a 603 00:25:45.740 --> 00:25:48.140 thing of that mass and that far away from the 604 00:25:48.140 --> 00:25:50.900 Earth. So ah it's an interesting 605 00:25:50.900 --> 00:25:53.660 thought uh and one that I 606 00:25:53.660 --> 00:25:56.380 think um we can say yes you could have a 607 00:25:56.380 --> 00:25:58.980 space station 150 kilometres in diameter 608 00:25:58.980 --> 00:26:01.900 weighing 10 to the 15 tonnes uh and it 609 00:26:01.900 --> 00:26:04.740 probably would not affect the status quo 610 00:26:04.740 --> 00:26:05.490 terribly badly. 611 00:26:06.200 --> 00:26:08.560 Andrew Dunkley: Okay, there you go. Uh and I just did a quick 612 00:26:08.560 --> 00:26:11.240 cheque but um, there's not much information 613 00:26:11.240 --> 00:26:13.520 about how fast space stations have to be away 614 00:26:13.520 --> 00:26:16.120 to avoid the Roche limit. But a solid object 615 00:26:16.920 --> 00:26:19.240 such as a Rocky body 616 00:26:20.040 --> 00:26:22.640 with 150 kilometre diameter would have to be 617 00:26:22.640 --> 00:26:25.480 at least 141,000 kilometres 618 00:26:25.480 --> 00:26:28.480 away from Earth. Um probably better off being 619 00:26:28.480 --> 00:26:30.200 over 200,000 kilometres away. 620 00:26:30.200 --> 00:26:32.480 Professor Fred Watson: Yes that's the sort of distance I had in 621 00:26:32.480 --> 00:26:35.360 mind. Something like that. Three times as 622 00:26:35.360 --> 00:26:37.760 far away as the, the geostationary 623 00:26:37.760 --> 00:26:38.400 satellites. Huh. 624 00:26:38.400 --> 00:26:39.760 Andrew Dunkley: Are. There you are now. 625 00:26:39.760 --> 00:26:42.160 He had a second question as to what would 626 00:26:42.160 --> 00:26:44.520 happen to the other planets if Earth was 627 00:26:44.520 --> 00:26:46.800 destroyed, no longer existed. I think we've 628 00:26:46.800 --> 00:26:48.480 been down this road before and I can't 629 00:26:48.480 --> 00:26:49.400 remember the answer. 630 00:26:50.040 --> 00:26:52.920 Professor Fred Watson: Yeah, so, um, the other planets 631 00:26:52.920 --> 00:26:55.680 would more or less stay in the present 632 00:26:55.680 --> 00:26:58.160 orbits. Those orbits would be 633 00:26:58.160 --> 00:27:00.920 perturbed, uh, differently from what they are 634 00:27:00.920 --> 00:27:03.600 now. So perturbations are the gravitational 635 00:27:03.600 --> 00:27:05.720 effects of other bodies in the solar system. 636 00:27:06.440 --> 00:27:09.240 Uh, when you look at the way 637 00:27:09.240 --> 00:27:11.240 things are in orbit, you start off with a two 638 00:27:11.240 --> 00:27:14.240 body problem with the sun and your object in 639 00:27:14.240 --> 00:27:16.760 orbit. But then you modify it by 640 00:27:17.400 --> 00:27:19.080 taking into account the gravitational 641 00:27:19.080 --> 00:27:20.960 attraction of other bodies and it becomes a 642 00:27:20.960 --> 00:27:22.680 three body problem and then four body problem 643 00:27:22.680 --> 00:27:25.080 and all the rest of it. Now, 644 00:27:25.480 --> 00:27:27.760 that three body problem would change if the 645 00:27:27.760 --> 00:27:30.720 Earth wasn't there. Um, or the N body 646 00:27:30.720 --> 00:27:32.720 problem, I suppose it would be a solar system 647 00:27:32.720 --> 00:27:34.980 with seven planets rather than eight. Uh, 648 00:27:35.000 --> 00:27:37.320 that would change the dynamics of the planets 649 00:27:37.320 --> 00:27:40.030 a little bit, but they would basically 650 00:27:40.030 --> 00:27:42.830 remain in their present orbits, uh, with 651 00:27:42.830 --> 00:27:45.670 just changes to the orbit rather than the 652 00:27:45.670 --> 00:27:46.630 orbits being destroyed. 653 00:27:46.630 --> 00:27:48.750 Andrew Dunkley: So, uh, in other words, if Earth disappeared, 654 00:27:48.750 --> 00:27:49.710 no great loss. 655 00:27:50.190 --> 00:27:53.150 Professor Fred Watson: No, not really. I mean, uh, you know, Douglas 656 00:27:53.150 --> 00:27:55.430 Adams had it in one. Mostly harmless. Mostly 657 00:27:55.430 --> 00:27:57.230 harmless, that's right. 658 00:27:57.230 --> 00:27:58.510 Andrew Dunkley: Thanks to the white mice. 659 00:27:59.150 --> 00:28:00.110 Professor Fred Watson: Yes, that's right. 660 00:28:01.710 --> 00:28:03.590 Andrew Dunkley: I wonder how all the other mice felt about 661 00:28:03.590 --> 00:28:06.430 that. You know, it was 662 00:28:06.430 --> 00:28:08.910 musculus. Racism. That's what it was. 663 00:28:08.990 --> 00:28:11.800 Professor Fred Watson: It is, yes. Mass racism. Exactly. So, 664 00:28:12.520 --> 00:28:14.030 yeah, thanks. 665 00:28:14.030 --> 00:28:16.200 Andrew Dunkley: Uh, Finn, great question. We always love 666 00:28:16.200 --> 00:28:18.440 these what ifs. So, um, if you'd like to keep 667 00:28:18.440 --> 00:28:20.200 sending in questions like that, or if you've 668 00:28:20.200 --> 00:28:22.800 got something deadly serious to discuss with 669 00:28:22.800 --> 00:28:25.440 us, like, uh, I don't know, exploding 670 00:28:25.440 --> 00:28:27.960 rockets and whatever else, uh, you can send 671 00:28:27.960 --> 00:28:30.600 them in to us. Uh, just go to spacenuts 672 00:28:30.680 --> 00:28:33.320 IO or spacenutspodcast.com, 673 00:28:33.400 --> 00:28:35.800 click on the Ask me anything button. 674 00:28:36.280 --> 00:28:38.840 You won't be asking me, you'll be asking him. 675 00:28:39.400 --> 00:28:41.710 But, uh, I'll read it out or you can send us 676 00:28:41.940 --> 00:28:43.220 audio question. As long as you've got a 677 00:28:43.220 --> 00:28:45.250 device with a microphone, you're all set. Uh, 678 00:28:45.250 --> 00:28:46.580 and while you're there, have a look around. 679 00:28:47.250 --> 00:28:48.820 Uh, that brings us to the end. Fred Watson, 680 00:28:48.820 --> 00:28:49.540 thank you very much. 681 00:28:50.260 --> 00:28:52.700 Professor Fred Watson: Great pleasure, Andrew. Always good to chew 682 00:28:52.700 --> 00:28:54.500 the fat. And, uh, I, uh, hope we'll do it 683 00:28:54.500 --> 00:28:54.940 again soon. 684 00:28:54.940 --> 00:28:55.460 Andrew Dunkley: We will. 685 00:28:55.540 --> 00:28:56.860 That's Professor Fred Watson Watson, 686 00:28:56.860 --> 00:28:58.700 astronomer at large, part of the team here at 687 00:28:58.700 --> 00:29:00.900 Space Nuts and thanks to Huw in the studio. 688 00:29:01.110 --> 00:29:02.620 Uh, who couldn't be with us today. He was 689 00:29:02.620 --> 00:29:04.780 seeing his dietitian after he reached 10 to 690 00:29:04.780 --> 00:29:05.780 the 15 tonnes. 691 00:29:08.190 --> 00:29:10.470 I'm surprised he survived. And from me, 692 00:29:10.470 --> 00:29:12.030 Andrew Dunkley. Thanks for your company. 693 00:29:12.110 --> 00:29:14.790 We'll be back again soon with another episode 694 00:29:14.790 --> 00:29:16.430 of Space Nuts. See you then. 695 00:29:16.430 --> 00:29:17.150 Professor Fred Watson: Bye. Bye. 696 00:29:18.350 --> 00:29:20.630 Andrew Dunkley: You've been listening to the Space Nuts 697 00:29:20.630 --> 00:29:23.590 podcast, available at 698 00:29:23.590 --> 00:29:25.550 Apple Podcasts, Spotify, 699 00:29:25.790 --> 00:29:28.470 iHeartRadio or your favourite podcast 700 00:29:28.470 --> 00:29:30.270 player. You can also stream on 701 00:29:30.270 --> 00:29:33.230 demand@bytes.com. this has been another 702 00:29:33.230 --> 00:29:35.230 quality podcast production from 703 00:29:35.230 --> 00:29:36.430 bytes.com.