WEBVTT 0 00:00:00.400 --> 00:00:02.160 Andrew Dunkley: Hello again and thank you for joining us on 1 00:00:02.160 --> 00:00:04.120 another episode of Space Nuts. This is a Q 2 00:00:04.120 --> 00:00:06.160 and A edition where we take audience 3 00:00:06.240 --> 00:00:09.000 questions. We put them on paper and then we 4 00:00:09.000 --> 00:00:11.680 put them on a roll that goes on a little 5 00:00:11.680 --> 00:00:14.520 thing in a bathroom. Or we could 6 00:00:14.520 --> 00:00:16.880 answer them. We can do that. Uh, coming up 7 00:00:16.880 --> 00:00:19.760 today we have questions, uh, uh, 8 00:00:19.760 --> 00:00:22.760 from John about Martian days. The length 9 00:00:22.760 --> 00:00:25.600 of a Martian day. It's close, but is it 10 00:00:25.600 --> 00:00:28.480 close enough to Earth standard? We'll discuss 11 00:00:28.480 --> 00:00:31.400 that. Uh, the growth of a black 12 00:00:31.400 --> 00:00:33.740 hole has been, uh, brought up again. 13 00:00:34.120 --> 00:00:36.660 Uh, we've got a, um, a question, uh, 14 00:00:36.900 --> 00:00:39.180 from an 11 year old named Thomas. Hi, Thomas. 15 00:00:39.420 --> 00:00:41.900 He wants to talk about the galactic centre. 16 00:00:42.060 --> 00:00:44.900 And Paul is asking our, uh, about 17 00:00:44.900 --> 00:00:47.899 our galactic location. So we'll deal with 18 00:00:47.899 --> 00:00:50.780 all of that today on this episode of Space 19 00:00:50.780 --> 00:00:51.340 Nuts. 20 00:00:51.500 --> 00:00:53.980 Professor Fred Watson: 15 seconds. Guidance is internal. 21 00:00:54.220 --> 00:00:56.940 10, 9. Ignition 22 00:00:56.940 --> 00:00:57.900 sequence start. 23 00:00:58.140 --> 00:00:59.100 Professor Fred Watson: Space Nuts. 24 00:00:59.100 --> 00:01:01.944 Professor Fred Watson: 5, 4, 3. 2. 1. 2, 3, 4, 25 00:01:02.016 --> 00:01:04.360 5, 5, 4, 3. Space 26 00:01:04.440 --> 00:01:07.000 Nuts astronauts report it feels good. 27 00:01:08.200 --> 00:01:11.160 Andrew Dunkley: Joining us again to sort all that out is 28 00:01:11.160 --> 00:01:13.120 Professor Fred Watson Watson, astronomer at 29 00:01:13.120 --> 00:01:14.120 large. Hello, Fred Watson. 30 00:01:14.200 --> 00:01:16.040 Professor Fred Watson: Hello, Andrew. Good to see you again. 31 00:01:16.540 --> 00:01:17.720 Andrew Dunkley: Uh, good to see you too. 32 00:01:18.200 --> 00:01:20.280 Professor Fred Watson: Yes. Despite the hole in my head. 33 00:01:20.520 --> 00:01:23.400 Andrew Dunkley: Yeah, yeah. It doesn't look any better than 34 00:01:23.400 --> 00:01:23.960 last time. 35 00:01:24.840 --> 00:01:25.960 Professor Fred Watson: It doesn't, does it? 36 00:01:26.040 --> 00:01:28.840 Andrew Dunkley: No, I mean, you know, it's only been 37 00:01:28.840 --> 00:01:30.640 minutes. You'd think it would have improved 38 00:01:30.640 --> 00:01:31.080 by now. 39 00:01:32.360 --> 00:01:34.280 Professor Fred Watson: That's what happens when you walk into a, 40 00:01:34.440 --> 00:01:36.820 when you walk into a closed screen door. 41 00:01:36.820 --> 00:01:37.380 Andrew Dunkley: Yeah. 42 00:01:37.620 --> 00:01:39.380 Professor Fred Watson: In the dark it hurts. 43 00:01:40.660 --> 00:01:43.420 Andrew Dunkley: Now that's why they have stuff, um, on, 44 00:01:43.420 --> 00:01:46.210 on glass sliding doors, you know, 45 00:01:46.210 --> 00:01:48.740 uh, that, that's a standard safety standard 46 00:01:48.740 --> 00:01:50.860 required these days so that, you know, the 47 00:01:50.860 --> 00:01:51.620 door is there. 48 00:01:51.700 --> 00:01:52.180 Professor Fred Watson: Yeah. 49 00:01:52.740 --> 00:01:54.780 Andrew Dunkley: But when it's nighttime and it's a screen 50 00:01:54.780 --> 00:01:56.900 door. Not, not many excuses left there, 51 00:01:56.900 --> 00:01:57.260 Fred Watson. 52 00:01:57.260 --> 00:02:00.060 Professor Fred Watson: Really only stupidity, I think is the, 53 00:02:00.060 --> 00:02:02.940 is the last one. But that's, that's 54 00:02:02.940 --> 00:02:04.580 my excuse many, many times. 55 00:02:05.620 --> 00:02:08.560 Andrew Dunkley: Yeah, well, we've all done it. 56 00:02:09.760 --> 00:02:11.600 Shall we try and answer these questions? 57 00:02:11.600 --> 00:02:12.160 Professor Fred Watson: We should. 58 00:02:12.320 --> 00:02:14.560 Andrew Dunkley: Okay, let's go to question one. This one 59 00:02:14.560 --> 00:02:16.000 comes from John. 60 00:02:16.830 --> 00:02:19.520 Uh, we know that the Martian Day is 39 61 00:02:19.520 --> 00:02:22.240 minutes longer than an Earth Day. That's 62 00:02:22.240 --> 00:02:25.200 about four and a half hours a week. Uh, when 63 00:02:25.280 --> 00:02:27.920 and if Mars is populated with humans, 64 00:02:28.320 --> 00:02:31.040 how would we work with the longer 65 00:02:31.040 --> 00:02:33.400 day, week? Would human 66 00:02:33.400 --> 00:02:36.160 biology tend to keep to the 24 hour 67 00:02:36.160 --> 00:02:38.960 day or would we adapt to a longer day, 68 00:02:38.960 --> 00:02:41.180 Night. Cycle. Cycle. Thanks. Love the show 69 00:02:41.180 --> 00:02:43.420 and have been a listener since you started. 70 00:02:43.740 --> 00:02:46.300 Wow, you've got a lot of spare time, John. 71 00:02:47.020 --> 00:02:49.580 Thank you so much, uh, for sending your 72 00:02:49.580 --> 00:02:52.240 question in and hope all is well. Uh, 73 00:02:52.380 --> 00:02:54.220 I love this question because 74 00:02:55.660 --> 00:02:58.340 you've got a planet that is close enough for 75 00:02:58.340 --> 00:03:00.380 us to get to in the not too distant future. 76 00:03:00.700 --> 00:03:03.180 Probably not a 77 00:03:03.180 --> 00:03:04.940 permanent settlement, but a rotating 78 00:03:04.940 --> 00:03:07.580 settlement of some kind will be the initial 79 00:03:07.580 --> 00:03:10.300 stages of humans being on Mars. 80 00:03:11.540 --> 00:03:14.500 And yet you've got an extra 39 81 00:03:14.500 --> 00:03:17.220 minutes a day to deal with what 82 00:03:17.700 --> 00:03:19.060 is going to be the impact. 83 00:03:20.690 --> 00:03:22.820 Professor Fred Watson: Um, I think we've already, we have 84 00:03:23.590 --> 00:03:25.980 um, a lot of data on this 85 00:03:25.980 --> 00:03:28.340 Andrew Dunkley: because the, we've already talked about this 86 00:03:28.340 --> 00:03:30.380 once before in the deep dark past. Quite a 87 00:03:30.380 --> 00:03:31.340 lot came up again. 88 00:03:31.340 --> 00:03:33.830 Professor Fred Watson: Yeah, yeah, because of the, the um, 89 00:03:34.260 --> 00:03:36.740 rover, um, drivers, they, 90 00:03:38.730 --> 00:03:41.610 the people who are uh, in command of, 91 00:03:41.610 --> 00:03:42.970 if I can put it that way, because they don't 92 00:03:42.970 --> 00:03:45.170 actually drive them directly but in command 93 00:03:45.170 --> 00:03:48.130 of the rovers on Mars and the two active 94 00:03:48.130 --> 00:03:50.150 NASA ones at the moment are Curiosity. Uh, 95 00:03:50.770 --> 00:03:53.529 and perseverance. Uh, they 96 00:03:53.930 --> 00:03:54.850 Adapt to uh, 97 00:03:56.890 --> 00:03:58.810 24 hours, 39 minutes day, 98 00:03:59.770 --> 00:04:02.610 and do it quite successfully 99 00:04:02.610 --> 00:04:05.530 as far as I've been able to work out. 100 00:04:06.890 --> 00:04:09.330 Andrew Dunkley: Well I hope so, yeah. 101 00:04:09.330 --> 00:04:11.450 Professor Fred Watson: Otherwise there might be a pile up on Mars. 102 00:04:11.750 --> 00:04:14.050 Um, and in fact the reason why I said they 103 00:04:14.050 --> 00:04:16.450 don't actually drive them is because the 104 00:04:16.450 --> 00:04:19.410 rovers themselves have got to be to some 105 00:04:19.410 --> 00:04:22.250 extent autonomous because of the delay 106 00:04:22.890 --> 00:04:25.850 in signal time to get between Mars and 107 00:04:26.090 --> 00:04:28.650 the Earth. You can't have video coming back 108 00:04:28.650 --> 00:04:30.690 from your rover and a steering wheel so that 109 00:04:30.690 --> 00:04:32.730 you respond to that because you'd have a sort 110 00:04:32.730 --> 00:04:35.050 of 20 or 30 minute delay probably before 111 00:04:36.030 --> 00:04:38.950 uh, before um, you turn, before 112 00:04:38.950 --> 00:04:41.430 the wheels turned on the rover. 113 00:04:41.910 --> 00:04:44.710 Andrew Dunkley: I would imagine that the manual 114 00:04:44.870 --> 00:04:47.350 driving of a rover from Earth 115 00:04:47.670 --> 00:04:50.630 on Mars would be damn near impossible because 116 00:04:51.030 --> 00:04:53.430 even your images would be out of sync with. 117 00:04:53.430 --> 00:04:54.670 Professor Fred Watson: Everything's out of sync. That's right. 118 00:04:54.670 --> 00:04:56.390 Andrew Dunkley: So you say, oh, there's a rock coming up. 119 00:04:56.630 --> 00:04:59.470 That was 40 minutes ago, I'll turn 120 00:04:59.470 --> 00:05:00.470 left now. 121 00:05:01.590 --> 00:05:02.150 Martin Berman Gorvine: Oops. 122 00:05:03.350 --> 00:05:03.470 Andrew Dunkley: Yeah. 123 00:05:03.470 --> 00:05:05.560 Professor Fred Watson: Ah, um, 124 00:05:06.400 --> 00:05:09.120 so the rovers drive themselves basically, 125 00:05:09.560 --> 00:05:12.300 uh, with a lot of assistance, um, 126 00:05:12.840 --> 00:05:15.760 and monitoring from Earth, uh, in order 127 00:05:15.840 --> 00:05:18.560 to see what's coming up and see what 128 00:05:19.040 --> 00:05:21.880 the onboard computers are doing in terms of 129 00:05:21.880 --> 00:05:23.840 what route they're taking through the rocks 130 00:05:23.840 --> 00:05:26.360 and debris on Mars. Ah, uh, 131 00:05:27.080 --> 00:05:29.920 um, but those people, as I understand 132 00:05:29.920 --> 00:05:32.800 it, do go on to uh, this 24 133 00:05:32.800 --> 00:05:35.440 hours and 39 minutes day length. 134 00:05:35.880 --> 00:05:37.980 Uh, I think it's nearing enough to our 24 135 00:05:37.980 --> 00:05:39.900 hours that I think they adapt quite quickly. 136 00:05:39.900 --> 00:05:41.860 From my recollection of our previous 137 00:05:41.860 --> 00:05:43.340 conversation about this Andrew. 138 00:05:44.380 --> 00:05:47.260 Andrew Dunkley: Yeah, if I remember rightly, we were talking 139 00:05:47.260 --> 00:05:49.180 about the fact that if you're going to stay 140 00:05:49.180 --> 00:05:51.860 on Mars long term you would 141 00:05:51.860 --> 00:05:53.980 have to adapt. 142 00:05:54.830 --> 00:05:57.340 Um, you wouldn't adapt naturally 143 00:05:58.940 --> 00:06:01.820 at all you'd have to take catnaps 144 00:06:01.820 --> 00:06:04.810 or something like that to catch up. Um, 145 00:06:05.100 --> 00:06:07.340 or something to that effect. 146 00:06:08.220 --> 00:06:11.040 Professor Fred Watson: Well, yes. So your circadian rhythms 147 00:06:11.040 --> 00:06:13.560 would, they'd be under stress, they'd change 148 00:06:15.880 --> 00:06:18.160 and I suppose you'd have a permanent feeling 149 00:06:18.160 --> 00:06:20.880 of jet lag. Probably what it feels like. 150 00:06:20.880 --> 00:06:23.510 Andrew Dunkley: It would be tough. I read an article, uh, 151 00:06:23.800 --> 00:06:26.440 last weekend which I found fascinating 152 00:06:26.440 --> 00:06:29.320 and it was, um, detailing how 153 00:06:29.320 --> 00:06:32.120 the eight hour night cycle 154 00:06:32.200 --> 00:06:34.600 that humans have, like going to bed for eight 155 00:06:34.600 --> 00:06:36.120 hours, is a myth. 156 00:06:36.880 --> 00:06:37.200 Professor Fred Watson: Yes. 157 00:06:37.520 --> 00:06:40.320 Andrew Dunkley: And that, um, it was actually 158 00:06:40.320 --> 00:06:42.800 something invented by a mattress company back 159 00:06:42.800 --> 00:06:45.280 in 1938. Have you heard this? 160 00:06:45.520 --> 00:06:48.080 Professor Fred Watson: No. Yes, I do know that 161 00:06:48.320 --> 00:06:50.080 we used to sleep twice in the night. 162 00:06:50.400 --> 00:06:53.240 Andrew Dunkley: That's right. So you go to bed at like 9 o' 163 00:06:53.240 --> 00:06:55.600 clock and you'd sleep for four hours 164 00:06:56.000 --> 00:06:58.200 and then you'd get up for two hours and you'd 165 00:06:58.200 --> 00:07:00.760 do stuff like, stuff we can't talk about on 166 00:07:00.760 --> 00:07:03.270 this podcast, but other stuff like, 167 00:07:03.270 --> 00:07:05.520 um, they cited a couple of, 168 00:07:07.150 --> 00:07:10.080 um, famous people, um, whose names have 169 00:07:10.080 --> 00:07:12.300 dropped straight out of my head. Um, 170 00:07:13.000 --> 00:07:15.960 William Shakespeare apparently wrote 171 00:07:16.040 --> 00:07:18.520 a lot of his famous works between 172 00:07:18.920 --> 00:07:21.640 1 and 3 in the morning when he got up and 173 00:07:21.640 --> 00:07:24.200 then he'd go back to bed for four hours. And, 174 00:07:24.380 --> 00:07:26.760 uh, Beethoven did the same thing with some of 175 00:07:26.760 --> 00:07:28.840 his symphonies. He wrote some of the 176 00:07:29.640 --> 00:07:31.880 best works that he ever created 177 00:07:32.280 --> 00:07:35.110 at 3 o' clock in the morning, um, 178 00:07:35.110 --> 00:07:37.730 during his wake time between his two sleeps. 179 00:07:38.290 --> 00:07:40.690 So the eight hour sleep 180 00:07:41.730 --> 00:07:44.330 that we have at night was an invention 181 00:07:44.330 --> 00:07:47.210 apparently, to sell mattresses. That's 182 00:07:47.210 --> 00:07:49.570 what I'm told. Look, I haven't confirmed or 183 00:07:49.570 --> 00:07:52.530 denied that, but it seems 184 00:07:52.530 --> 00:07:53.570 possible, I suppose. 185 00:07:54.210 --> 00:07:56.770 Professor Fred Watson: Well, yes, I think we have, 186 00:07:58.080 --> 00:08:00.970 uh, I think, um, there's been evidence 187 00:08:00.970 --> 00:08:02.970 from the earliest times, 188 00:08:04.070 --> 00:08:06.570 uh, the times when people truly were ancient 189 00:08:06.570 --> 00:08:08.970 peoples back thousands of years ago, 190 00:08:09.530 --> 00:08:10.930 uh, that that's how they lived their lives. 191 00:08:10.930 --> 00:08:13.170 Exactly as you've said. And maybe the last 192 00:08:13.170 --> 00:08:16.010 vestiges of that were keeping 193 00:08:16.010 --> 00:08:17.650 going in Shakespeare's time and then in 194 00:08:17.650 --> 00:08:20.570 Beethoven's time. Um, there 195 00:08:20.570 --> 00:08:22.530 weren't that many clocks around then. There 196 00:08:22.530 --> 00:08:24.810 were some, but not that many. It wasn't like 197 00:08:24.810 --> 00:08:27.650 you had a smart watch by your bedside or 198 00:08:27.650 --> 00:08:30.450 anything like that. So, uh, it would be a 199 00:08:30.450 --> 00:08:33.060 natural rhythm that they would use, uh, 200 00:08:34.710 --> 00:08:35.990 to sleep and wake up. 201 00:08:36.150 --> 00:08:38.990 Andrew Dunkley: Yes. Modernization certainly 202 00:08:38.990 --> 00:08:40.030 messed us up, hasn't it? 203 00:08:40.030 --> 00:08:41.590 Professor Fred Watson: Yeah, yeah, that's right. I think in that 204 00:08:41.590 --> 00:08:42.230 case it has. 205 00:08:42.550 --> 00:08:44.970 Andrew Dunkley: And I think, uh, on Mars, um, 206 00:08:45.430 --> 00:08:47.190 it will be a pretty difficult thing, 207 00:08:47.750 --> 00:08:49.590 Professor Fred Watson: I imagine it may be. 208 00:08:50.230 --> 00:08:53.190 So maybe I can just sidestep here slightly, 209 00:08:53.190 --> 00:08:56.190 Andrew, um, because I would very much like to 210 00:08:56.190 --> 00:08:58.750 know uh, what 211 00:08:58.750 --> 00:09:01.030 answer one of our listeners would give to 212 00:09:01.030 --> 00:09:03.950 that, and that's Dr. Heidi DeBlock who's 213 00:09:03.950 --> 00:09:06.110 I think based in Houston, if I remember 214 00:09:06.350 --> 00:09:09.070 rightly, who is basically a space medic. 215 00:09:09.610 --> 00:09:12.350 Uh, and um, uh, it will be very interesting 216 00:09:12.350 --> 00:09:15.350 to hear her take on how humans will adapt 217 00:09:15.350 --> 00:09:18.270 to that. And if I may, she was in touch with 218 00:09:18.270 --> 00:09:20.790 us recently to comment on one of our earlier 219 00:09:20.790 --> 00:09:23.070 questions. Would it be all right if I. Yeah. 220 00:09:23.470 --> 00:09:26.030 Andrew Dunkley: And that was when we were talking about how 221 00:09:26.030 --> 00:09:28.880 people deal with um, gravity when they 222 00:09:28.880 --> 00:09:30.720 get back on Earth after being out in space 223 00:09:30.720 --> 00:09:32.080 for a while, correct? 224 00:09:32.080 --> 00:09:35.040 Professor Fred Watson: Yes, that's right. Uh, she 225 00:09:35.040 --> 00:09:38.040 says, um, I just finished the July 226 00:09:38.040 --> 00:09:40.520 5th space nuts and wanted to help answer the 227 00:09:40.520 --> 00:09:42.240 question about how the astronauts feel when 228 00:09:42.240 --> 00:09:44.520 they land back on Earth. Of course I haven't 229 00:09:44.520 --> 00:09:47.080 experienced it in person, but have worked 230 00:09:47.080 --> 00:09:49.280 with plenty of astronauts at landing. In 231 00:09:49.280 --> 00:09:51.840 particular, all of our, uh, physiology 232 00:09:51.840 --> 00:09:54.280 changes in space as we are designed for 233 00:09:54.280 --> 00:09:57.160 1G. Some astronauts are pretty good when 234 00:09:57.160 --> 00:09:58.720 they land, especially those who are on the 235 00:09:58.720 --> 00:10:00.740 shuttle and in space. For short time. 236 00:10:01.860 --> 00:10:04.820 Sorry, for a short time. Some had significant 237 00:10:04.980 --> 00:10:07.860 problems. They stemmed from the orthostatic 238 00:10:07.940 --> 00:10:10.380 hypotension as a result from the 239 00:10:10.380 --> 00:10:13.260 cardiovascular changes, some of the changes 240 00:10:13.260 --> 00:10:15.420 in the inner ear with balance and knowing 241 00:10:15.420 --> 00:10:17.460 where you physically are, some mild 242 00:10:17.460 --> 00:10:20.340 weaknesses, et cetera. These changes are more 243 00:10:20.340 --> 00:10:23.020 exaggerated with long duration flight in the 244 00:10:23.020 --> 00:10:25.500 International Space Station. The vision 245 00:10:25.500 --> 00:10:28.260 problems are called SANS S A N S 246 00:10:28.500 --> 00:10:30.740 which is an acronym for Spaceflight 247 00:10:30.740 --> 00:10:32.960 Associated Neuro Ocular 248 00:10:33.040 --> 00:10:36.000 Syndrome. Our lab is studying that 249 00:10:36.000 --> 00:10:38.480 as well. That's a whole other fascinating 250 00:10:38.480 --> 00:10:41.480 issue. I could tell you some 251 00:10:41.480 --> 00:10:43.760 fun storeys about astronauts and how weird 252 00:10:43.760 --> 00:10:46.360 some of them feel when they get back. Maybe 253 00:10:46.360 --> 00:10:48.280 we need to get Heidi on the show. Maybe we 254 00:10:48.280 --> 00:10:50.710 do. Yeah, no, that's um, 255 00:10:51.530 --> 00:10:53.920 uh, she has another interesting comment 256 00:10:53.920 --> 00:10:56.520 actually about the, about the uh, 257 00:10:56.520 --> 00:10:58.680 Voyager Golden Record. But we might talk 258 00:10:58.680 --> 00:11:00.650 about that another time. Fair enough. 259 00:11:00.650 --> 00:11:02.330 Andrew Dunkley: Yeah. All right. Thank you, Heidi. That was 260 00:11:02.330 --> 00:11:02.970 fascinating. 261 00:11:02.970 --> 00:11:03.450 Professor Fred Watson: Yeah. 262 00:11:03.500 --> 00:11:06.130 Andrew Dunkley: Um, what an amazing job working with all 263 00:11:06.130 --> 00:11:09.090 those incredible people trying to 264 00:11:09.090 --> 00:11:11.130 figure out how to deal with the zero G 265 00:11:11.290 --> 00:11:13.810 problem. But uh, on Mars the gravity will 266 00:11:13.810 --> 00:11:16.770 also be an issue. So, um, there's 267 00:11:16.770 --> 00:11:19.330 a heck of a lot that needs to be sorted out 268 00:11:19.330 --> 00:11:22.330 before we um, put people down 269 00:11:22.330 --> 00:11:25.290 there. Because it's such a long trip to 270 00:11:25.290 --> 00:11:26.690 get there. It's not like you can go, uh, ah, 271 00:11:26.690 --> 00:11:28.330 no, this is no good and come straight back. 272 00:11:28.330 --> 00:11:30.610 Professor Fred Watson: It's not going to be that simple. That's 273 00:11:30.610 --> 00:11:32.230 right. Once you're on your way. On your way. 274 00:11:32.230 --> 00:11:34.550 And the only way back is to keep going. 275 00:11:34.950 --> 00:11:37.670 Andrew Dunkley: Yeah, exactly. Thanks for the question, John. 276 00:11:37.880 --> 00:11:40.750 Uh, well asked. And yeah, it's not 277 00:11:40.750 --> 00:11:43.610 going to be a snack, that's for sure. Let's, 278 00:11:43.610 --> 00:11:45.670 uh, move on to our, uh, next question from 279 00:11:45.750 --> 00:11:46.310 Dan. 280 00:11:47.030 --> 00:11:49.270 Martin Berman Gorvine: Hello gentlemen. Dan from the Gold coast 281 00:11:49.270 --> 00:11:51.510 here. Uh, now I know you've been 282 00:11:52.710 --> 00:11:55.190 asked a million questions about black holes, 283 00:11:55.690 --> 00:11:57.990 uh, but I do have a quick two parter and I'm 284 00:11:57.990 --> 00:11:59.310 hoping that's something you've never had to 285 00:11:59.310 --> 00:12:02.270 answer before. Really quickly, from the 286 00:12:02.270 --> 00:12:05.030 point when a black hole is born, 287 00:12:05.030 --> 00:12:07.030 birth, created, whatever you want to call it, 288 00:12:07.410 --> 00:12:10.150 uh, how quickly is that growing to become a, 289 00:12:10.390 --> 00:12:12.190 let's say, supermassive black hole or just 290 00:12:12.190 --> 00:12:13.760 something a lot bigger? Um, 291 00:12:14.950 --> 00:12:17.830 or is that not how black holes work and I'm 292 00:12:17.830 --> 00:12:19.670 not understanding it properly? Two, 293 00:12:21.190 --> 00:12:23.430 Hypothetically, uh, if there's no matter or 294 00:12:23.430 --> 00:12:25.510 energy or anything surrounding 295 00:12:26.370 --> 00:12:29.090 the black hole to take in and let's say 296 00:12:29.090 --> 00:12:32.010 eat, uh, is the black hole still going to 297 00:12:32.010 --> 00:12:34.850 grow? Is there more to the black hole growing 298 00:12:34.850 --> 00:12:36.690 than I understand? 299 00:12:37.640 --> 00:12:39.770 Um, yeah. Hopefully that made sense and 300 00:12:39.770 --> 00:12:41.809 hopefully it's worth answering. Love the 301 00:12:41.809 --> 00:12:44.570 show. Love you guys. Work. Cheers, 302 00:12:44.570 --> 00:12:45.010 bye. 303 00:12:45.330 --> 00:12:47.810 Andrew Dunkley: Thank you, Dan. Uh, nice to hear from you. 304 00:12:48.060 --> 00:12:50.930 Uh, yeah, a couple of questions in that one. 305 00:12:51.000 --> 00:12:53.290 Um, we never talk about black holes, but we 306 00:12:53.290 --> 00:12:56.050 will today. Ah, speed of growth. 307 00:12:56.320 --> 00:12:58.730 Um, that's an interesting one. Um, 308 00:12:59.480 --> 00:13:02.160 given that we're starting to think that there 309 00:13:02.160 --> 00:13:04.600 were some absolutely 310 00:13:04.600 --> 00:13:07.440 enormous, um, black holes in the 311 00:13:07.440 --> 00:13:09.360 early universe. Um, 312 00:13:10.120 --> 00:13:13.000 and, and they're looking 313 00:13:13.000 --> 00:13:14.640 for more and more evidence to see what was 314 00:13:14.640 --> 00:13:17.160 going on early on. Um, but we've got some 315 00:13:17.400 --> 00:13:19.740 gargantuan ones still around. Uh, 316 00:13:20.040 --> 00:13:22.880 so how fast did they get that big? And 317 00:13:22.880 --> 00:13:25.750 I, um, I'm starting to think, Fred Watson, 318 00:13:25.750 --> 00:13:27.590 it wouldn't be a stock standard approach. 319 00:13:28.790 --> 00:13:31.430 Professor Fred Watson: Maybe not, maybe not. Uh, but I mean, 320 00:13:31.430 --> 00:13:33.830 Dan's asking, uh, one of the 321 00:13:33.990 --> 00:13:35.990 fundamental questions of astrophysics at the 322 00:13:35.990 --> 00:13:38.510 moment. This is a very hot topic. Uh, and 323 00:13:38.510 --> 00:13:40.510 what set the cat among the pigeons and made 324 00:13:40.510 --> 00:13:42.350 it a hot topic is the James Webb Space 325 00:13:42.350 --> 00:13:45.110 Telescope. Because, um, until 326 00:13:45.270 --> 00:13:48.150 that came along, the idea was 327 00:13:48.150 --> 00:13:51.080 that as basically as Daniel suggests, 328 00:13:51.080 --> 00:13:54.080 black holes were formed in 329 00:13:54.080 --> 00:13:56.760 the early universe by exploding stars that, 330 00:13:56.990 --> 00:13:59.320 um, collapsed at the end of their lives 331 00:13:59.800 --> 00:14:02.200 to form a black hole. The core would collapse 332 00:14:02.200 --> 00:14:04.440 to a black hole and that then 333 00:14:05.160 --> 00:14:07.960 over billions of years that black hole would 334 00:14:07.960 --> 00:14:10.800 grow. And eventually in our own epoch 335 00:14:10.800 --> 00:14:13.800 today, 13.8 billion years after the 336 00:14:13.800 --> 00:14:16.640 Big Bang, uh, you have supermassive black 337 00:14:16.640 --> 00:14:19.480 holes at the centre of every galaxy. That 338 00:14:19.480 --> 00:14:21.710 was the old wisdom. But the James Webb 339 00:14:21.710 --> 00:14:23.430 telescope has turned that completely on its 340 00:14:23.430 --> 00:14:25.990 head because we have serious 341 00:14:25.990 --> 00:14:28.630 evidence of supermassive black holes 342 00:14:29.030 --> 00:14:31.430 within the first 500 million years 343 00:14:32.150 --> 00:14:34.950 of the universe's existence. And that's 344 00:14:34.950 --> 00:14:37.750 too quick for, or too 345 00:14:37.750 --> 00:14:40.670 short a time for this, um, you 346 00:14:40.670 --> 00:14:42.630 know, this slow accretion of 347 00:14:43.190 --> 00:14:46.130 stuff, uh, as being the, um, 348 00:14:46.950 --> 00:14:49.130 the growth mechanism for black holes. Uh, 349 00:14:49.130 --> 00:14:51.110 it's too short a time for that to be the 350 00:14:51.110 --> 00:14:53.350 case. Uh, so 351 00:14:53.670 --> 00:14:56.670 either our ideas of how fast they gobble 352 00:14:56.670 --> 00:14:59.510 up matter is wrong. And they 353 00:14:59.510 --> 00:15:01.870 gobble up matter a lot faster than we 354 00:15:01.870 --> 00:15:03.830 thought. And we actually covered a storey on 355 00:15:03.830 --> 00:15:06.150 this, I think, about four or five episodes 356 00:15:06.150 --> 00:15:08.870 ago, because there are some scientists who 357 00:15:09.430 --> 00:15:11.750 came to conclusion that one of the things 358 00:15:11.750 --> 00:15:14.590 that we thought limited how fast a 359 00:15:14.590 --> 00:15:17.140 black hole can gobble stuff up, uh, was 360 00:15:17.140 --> 00:15:19.460 actually invalid under certain circumstances. 361 00:15:20.420 --> 00:15:23.420 So that's that one avenue of 362 00:15:23.420 --> 00:15:25.580 research that's come from the James Webb 363 00:15:25.580 --> 00:15:27.340 Telescope showing us that, ah, we've got 364 00:15:27.340 --> 00:15:29.340 these supermassive black holes in the early 365 00:15:29.340 --> 00:15:31.980 universe. But the other one is the idea of 366 00:15:31.980 --> 00:15:34.660 the little pink dots or the little red dots 367 00:15:34.660 --> 00:15:37.020 as they're called. And these are thought to 368 00:15:37.020 --> 00:15:39.700 be, uh, basically just 369 00:15:39.700 --> 00:15:42.260 clouds of gas, hydrogen gas, 370 00:15:42.420 --> 00:15:45.220 which are directly feeding a black hole 371 00:15:45.540 --> 00:15:48.320 that may have been formed in the Big Bang. In 372 00:15:48.320 --> 00:15:50.160 other words, you didn't have to have star 373 00:15:50.160 --> 00:15:53.080 formation and then stars blowing up to 374 00:15:53.080 --> 00:15:55.440 create black holes in order to kick this 375 00:15:55.440 --> 00:15:58.200 process off. The Big Bang itself might have 376 00:15:58.200 --> 00:15:59.800 kicked off the process of black hole 377 00:15:59.800 --> 00:16:02.280 formation by producing these things that we 378 00:16:02.280 --> 00:16:05.280 call primordial black holes. Um, and 379 00:16:05.440 --> 00:16:08.360 they may have turned out to be able 380 00:16:08.360 --> 00:16:10.880 to grow very quickly, um, by 381 00:16:10.960 --> 00:16:13.720 immersing themselves simply in big 382 00:16:13.720 --> 00:16:16.210 clouds of hydrogen and gobbling it all up. 383 00:16:16.370 --> 00:16:19.180 Andrew Dunkley: Yeah, of course, um, 384 00:16:19.330 --> 00:16:22.130 when they run out of stuff, they can't grow. 385 00:16:22.130 --> 00:16:22.770 Is that right? 386 00:16:23.170 --> 00:16:25.240 Professor Fred Watson: That's right. So that's part two of, uh, 387 00:16:25.240 --> 00:16:28.050 Dan's question. Uh, what happens when 388 00:16:28.050 --> 00:16:29.690 there's nothing there for them to eat and 389 00:16:29.690 --> 00:16:31.650 they become what we call quiescent black 390 00:16:31.650 --> 00:16:34.410 holes? They don't do anything. They're 391 00:16:34.410 --> 00:16:36.360 there, uh, and they're still, uh, 392 00:16:37.250 --> 00:16:39.930 things that, um, if a cloud of hydrogen 393 00:16:39.930 --> 00:16:42.910 strayed by, they might seize it 394 00:16:42.910 --> 00:16:45.350 by their own gravity and pull it in. But, 395 00:16:45.520 --> 00:16:47.430 um, they're not going to go out, 396 00:16:49.160 --> 00:16:51.110 um, roaming through the universe looking for 397 00:16:51.430 --> 00:16:53.390 stuff to accrete. In other words, looking for 398 00:16:53.390 --> 00:16:53.910 a snack. 399 00:16:54.150 --> 00:16:54.300 Professor Fred Watson: Yeah. 400 00:16:54.300 --> 00:16:57.150 Andrew Dunkley: Ah, I used to work with a guy whose nickname 401 00:16:57.150 --> 00:16:58.990 was quiescent black hole. He was there, but 402 00:16:58.990 --> 00:16:59.910 he didn't do anything. 403 00:17:03.030 --> 00:17:04.630 Professor Fred Watson: Yes, I think I know who you mean. 404 00:17:08.370 --> 00:17:10.760 Yeah. Anyway, quiescent black holes, uh, are, 405 00:17:10.760 --> 00:17:13.370 uh, basically what, uh, Dan has 406 00:17:13.370 --> 00:17:14.930 described. But the first part of his question 407 00:17:14.930 --> 00:17:17.850 is absolutely asking the same questions 408 00:17:17.850 --> 00:17:20.010 that today's astrophysicists are. Uh, it's 409 00:17:20.010 --> 00:17:22.450 one whose answer we don't know. But the 410 00:17:22.450 --> 00:17:24.890 consensus will emerge over the next. Probably 411 00:17:24.890 --> 00:17:26.890 not very long because we're getting so much 412 00:17:26.890 --> 00:17:29.890 data from the James Webb telescope that I 413 00:17:29.890 --> 00:17:31.530 think it'll be quite soon before this whole 414 00:17:31.530 --> 00:17:34.380 issue is resolved, I would think. Sorry, 415 00:17:34.460 --> 00:17:36.620 I was just going to say when, when there is 416 00:17:36.620 --> 00:17:38.900 hard evidence of a primordial black hole 417 00:17:38.900 --> 00:17:41.100 being discovered, one that was created in the 418 00:17:41.100 --> 00:17:43.900 Big Bang, then that'll be Nobel 419 00:17:43.900 --> 00:17:45.980 Prize winning science when we get to that 420 00:17:45.980 --> 00:17:48.140 stage. But it won't be us. 421 00:17:48.140 --> 00:17:50.670 Andrew Dunkley: Indeed, I was going to suggest that black um, 422 00:17:50.860 --> 00:17:53.540 holes are probably like humans. Consumption 423 00:17:53.540 --> 00:17:54.860 will decide how big they get. 424 00:17:55.980 --> 00:17:58.900 Professor Fred Watson: Maybe that's right, yeah, yeah, we'll have 425 00:17:58.900 --> 00:18:01.750 Andrew Dunkley: to wait and see. All right Dan. Hopefully uh, 426 00:18:02.160 --> 00:18:04.600 we covered that for you adequately. Thanks 427 00:18:04.600 --> 00:18:06.960 for sending in the question. This is Space 428 00:18:06.960 --> 00:18:08.880 Nuts with Andrew Dunkley and Professor 429 00:18:08.880 --> 00:18:09.720 Fred Watson Watson. 430 00:18:12.520 --> 00:18:14.760 Professor Fred Watson: Three, two, one. 431 00:18:15.400 --> 00:18:16.600 Andrew Dunkley: Space Nuts. 432 00:18:17.160 --> 00:18:19.520 Our next question, Fred Watson, comes from 433 00:18:19.520 --> 00:18:22.360 Thomas Reid. Thomas is 11 years old. 434 00:18:22.520 --> 00:18:24.560 He says something has been troubling me. In 435 00:18:24.560 --> 00:18:27.360 books I've read they say that the centres of 436 00:18:27.360 --> 00:18:30.320 galaxies are very big black holes and I 437 00:18:30.320 --> 00:18:32.460 have a few questions about them but uh, I'm 438 00:18:32.460 --> 00:18:34.820 only an 11 year old kid so the questions 439 00:18:34.820 --> 00:18:36.620 might sound silly but here they are. Now 440 00:18:36.620 --> 00:18:38.220 we've got five questions Fred Watson, so we 441 00:18:38.220 --> 00:18:41.220 can be brief on on them. Unless you wanted to 442 00:18:41.220 --> 00:18:43.940 sit here for another couple of hours. Um, if 443 00:18:43.940 --> 00:18:45.780 Jonty was here we would be a couple of hours. 444 00:18:46.700 --> 00:18:49.660 Um, can the galactic centre swallow all the 445 00:18:49.660 --> 00:18:52.380 stars and planets in the galaxy? How big are 446 00:18:52.380 --> 00:18:54.740 the galactic centres or do we not know, 447 00:18:55.260 --> 00:18:57.300 uh, if they can swallow up all the stars and 448 00:18:57.300 --> 00:19:00.020 planets. Is there a limit? If there is a 449 00:19:00.020 --> 00:19:02.620 limit, what is it? And if there is a 450 00:19:02.620 --> 00:19:05.440 limit happens when the limit is reached. 451 00:19:05.440 --> 00:19:07.440 Thank you for taking the time to read this 452 00:19:07.440 --> 00:19:09.560 and I would love it if you could reply. Well 453 00:19:09.560 --> 00:19:12.450 we are going to reply right now Thomas. Um, 454 00:19:13.680 --> 00:19:16.560 yeah, it's great that somebody, uh, so 455 00:19:16.560 --> 00:19:19.120 young is taking a keen interest in something 456 00:19:19.279 --> 00:19:22.180 so mysterious as a black hole. Uh, 457 00:19:22.240 --> 00:19:24.360 we want to start at the top. Can the galactic 458 00:19:24.360 --> 00:19:26.080 centre swallow all the stars and planets in 459 00:19:26.080 --> 00:19:26.720 the galaxy? 460 00:19:27.360 --> 00:19:30.240 Professor Fred Watson: Well so the answer is no. Um, so the 461 00:19:30.240 --> 00:19:33.040 galaxies are very big. Ours is about 100,000 462 00:19:33.040 --> 00:19:35.900 light years across. Uh, black holes 463 00:19:35.980 --> 00:19:38.500 have ah, a kind of sphere of 464 00:19:38.500 --> 00:19:41.380 influence um, which gravitationally 465 00:19:41.380 --> 00:19:43.620 stretches to the edge of the galaxy. But by 466 00:19:43.620 --> 00:19:45.740 the time you get there the gravity of the 467 00:19:45.740 --> 00:19:48.700 black hole is very, very weak indeed. And 468 00:19:48.700 --> 00:19:51.660 so it's only in the central region of a 469 00:19:51.660 --> 00:19:54.420 galaxy where you could get material 470 00:19:54.420 --> 00:19:57.100 being swallowed up uh, to create this 471 00:19:57.260 --> 00:19:58.980 activity that we talk about when we Talk 472 00:19:58.980 --> 00:20:01.500 about active black holes, uh, where 473 00:20:01.500 --> 00:20:03.780 there's, uh, an accretion disc, a disc of 474 00:20:03.780 --> 00:20:06.700 material swirling around it. And these jets, 475 00:20:07.240 --> 00:20:09.040 uh, point basically at right angles to the 476 00:20:09.040 --> 00:20:10.960 accretion disc, jets of material travelling 477 00:20:10.960 --> 00:20:12.520 at nearly the speed of light. Quite 478 00:20:12.520 --> 00:20:15.240 extraordinary. So, um, that's all 479 00:20:15.240 --> 00:20:17.760 great and black holes, like a factory or a 480 00:20:17.760 --> 00:20:20.520 furnace doing that, but its stretch is not 481 00:20:20.520 --> 00:20:23.439 very far. Uh, it's measured 482 00:20:23.439 --> 00:20:25.040 in light years, but not in hundreds of 483 00:20:25.040 --> 00:20:27.320 thousands of light years, which would have to 484 00:20:27.320 --> 00:20:29.640 be to grab everything in the galaxy. So the 485 00:20:29.640 --> 00:20:32.310 answer is no. The, uh, galactic centre, uh, 486 00:20:32.310 --> 00:20:34.800 black hole cannot swallow all the stars and 487 00:20:34.800 --> 00:20:35.960 planets in the galaxy. 488 00:20:36.630 --> 00:20:39.420 Andrew Dunkley: Uh, so Thomas can sleep well tonight. Um, how 489 00:20:39.420 --> 00:20:42.420 big are the galactic centres? Do we know how 490 00:20:42.420 --> 00:20:42.730 big? 491 00:20:42.730 --> 00:20:45.460 Professor Fred Watson: M. We do. Yes, we do, because 492 00:20:47.220 --> 00:20:50.180 we can measure the speed 493 00:20:50.180 --> 00:20:52.900 of rotation of stuff 494 00:20:52.900 --> 00:20:55.339 swirling around a black hole, if it's an 495 00:20:55.339 --> 00:20:58.220 active one. And that directly tells you 496 00:20:58.220 --> 00:21:01.140 the mass of the black hole. Um, because 497 00:21:01.140 --> 00:21:03.420 the bigger the black hole, the faster the 498 00:21:03.420 --> 00:21:06.420 stuff is going. And so, um, in terms 499 00:21:06.420 --> 00:21:09.360 of if, the if by 500 00:21:09.360 --> 00:21:12.040 big, Thomas means what's their mass? 501 00:21:12.590 --> 00:21:15.000 Uh, we can measure them quite accurately 502 00:21:15.240 --> 00:21:18.240 now because we can measure their mass. We can 503 00:21:18.240 --> 00:21:20.680 also work out their event horizon 504 00:21:20.760 --> 00:21:23.560 diameter or radius. The event horizon 505 00:21:23.880 --> 00:21:26.880 is that sort of imaginary sphere around a 506 00:21:26.880 --> 00:21:29.480 black hole beyond which light cannot 507 00:21:29.480 --> 00:21:32.160 escape. And so it would appear as a dark 508 00:21:32.160 --> 00:21:34.680 sphere. So the event horizon is the 509 00:21:34.920 --> 00:21:37.460 point of no return for anything going into a 510 00:21:37.460 --> 00:21:40.180 black hole. And it's also the point of no 511 00:21:40.180 --> 00:21:42.990 escape for light waves. Uh, 512 00:21:42.990 --> 00:21:45.540 so we can, knowing the mass of a black hole, 513 00:21:45.540 --> 00:21:48.180 we can calculate how big that event 514 00:21:48.180 --> 00:21:50.100 horizon would be. And some of the 515 00:21:50.100 --> 00:21:52.900 supermassive ones, ah, are really very big. 516 00:21:52.900 --> 00:21:55.020 They're measured in light years, tens of 517 00:21:55.020 --> 00:21:56.620 light years, perhaps for the supermassive 518 00:21:56.620 --> 00:21:57.220 black holes. 519 00:21:57.380 --> 00:22:00.180 Andrew Dunkley: Yeah. It's a level of enormity 520 00:22:00.180 --> 00:22:01.900 that you just struggle to get your head 521 00:22:01.900 --> 00:22:02.180 around. 522 00:22:02.180 --> 00:22:03.300 Professor Fred Watson: Yeah, yeah, I suppose. 523 00:22:03.300 --> 00:22:05.540 Andrew Dunkley: In terms of the rest of Thomas's questions, 524 00:22:05.620 --> 00:22:07.900 you've basically answered it with the answer 525 00:22:07.900 --> 00:22:10.040 to first question, because he's asking if 526 00:22:10.040 --> 00:22:11.680 they can swallow up all the stars and 527 00:22:11.680 --> 00:22:13.920 planets. Is there a limit? If there is a 528 00:22:13.920 --> 00:22:16.560 limit, what is it? Uh, and if there is a 529 00:22:16.560 --> 00:22:18.200 limit, what happens when the limit is 530 00:22:18.200 --> 00:22:20.960 reached? Well, the limit is probably 531 00:22:21.920 --> 00:22:24.719 the local area of the centre of the galaxy 532 00:22:24.800 --> 00:22:26.640 and what's available to eat. 533 00:22:26.880 --> 00:22:29.680 Professor Fred Watson: Yes, that's right. So the limiting factor, 534 00:22:29.680 --> 00:22:31.590 uh, is, um, 535 00:22:32.320 --> 00:22:34.920 basically what you might call the grasp of 536 00:22:34.920 --> 00:22:37.800 the black hole, how far it can reach to 537 00:22:37.800 --> 00:22:40.160 pull something in. And that is 538 00:22:40.380 --> 00:22:43.340 dependent on how fast the objects are moving. 539 00:22:43.340 --> 00:22:45.220 So you can have some stars and there are 540 00:22:45.220 --> 00:22:47.700 some. We've observed them, uh, with infrared 541 00:22:47.700 --> 00:22:50.540 radiation that are comfortably in 542 00:22:50.540 --> 00:22:52.300 orbit, uh, around 543 00:22:53.580 --> 00:22:55.580 the black hole at the centre of our own 544 00:22:55.580 --> 00:22:57.660 galaxy, which are not being pulled in, 545 00:22:57.660 --> 00:22:59.660 they're orbiting. And that's because their 546 00:22:59.660 --> 00:23:02.500 speed is enough to keep them out of the grasp 547 00:23:02.500 --> 00:23:05.460 of the black hole. Um, their distances from 548 00:23:05.460 --> 00:23:08.430 the black hole are measured in not two 549 00:23:08.430 --> 00:23:11.230 dissimilar units from the solar system. Sort 550 00:23:11.230 --> 00:23:13.390 of half a light day or something like that, 551 00:23:13.870 --> 00:23:16.870 you know, light day, that's 552 00:23:16.870 --> 00:23:18.710 the sort of measures that we're talking 553 00:23:18.710 --> 00:23:21.390 about. Um, which probably 554 00:23:21.710 --> 00:23:23.749 denies what I just said a few minutes ago 555 00:23:23.749 --> 00:23:26.590 about, um, some black hole event horizons 556 00:23:26.590 --> 00:23:28.790 being tens of light years. I don't think they 557 00:23:28.790 --> 00:23:30.110 are. I think they're smaller than that. 558 00:23:30.190 --> 00:23:30.750 Joe: Okay. 559 00:23:30.910 --> 00:23:33.110 Andrew Dunkley: I thought of a way to explain it to Thomas. 560 00:23:33.110 --> 00:23:35.040 So, uh, Thomas, you've won a competition 561 00:23:35.110 --> 00:23:37.270 kitchen and you can go to 562 00:23:37.430 --> 00:23:39.910 McDonald's and eat everything you want. 563 00:23:40.470 --> 00:23:43.230 Absolutely. Just keep eating until, you know, 564 00:23:43.230 --> 00:23:46.110 the cows come home. However, you aren't 565 00:23:46.110 --> 00:23:48.390 allowed to move from wherever you're standing 566 00:23:48.390 --> 00:23:50.710 and you can only eat what's within reach. 567 00:23:52.150 --> 00:23:54.830 Once you run out of food, you stop 568 00:23:54.830 --> 00:23:57.310 growing. And you're the black hole, by the 569 00:23:57.310 --> 00:23:59.230 way. How's that for an analogy? 570 00:23:59.230 --> 00:24:01.390 Professor Fred Watson: It's a nice one. I like it. Yes. Yeah, 571 00:24:01.390 --> 00:24:03.550 because your reach is the sort of 572 00:24:03.550 --> 00:24:06.390 gravitational force that you can exert. It's 573 00:24:06.390 --> 00:24:06.940 a good way of putting it. 574 00:24:07.090 --> 00:24:07.210 Professor Fred Watson: It. 575 00:24:07.210 --> 00:24:08.050 Andrew Dunkley: Andrew, well done. 576 00:24:08.050 --> 00:24:09.210 Professor Fred Watson: You should be on the I try 577 00:24:09.210 --> 00:24:11.410 Andrew Dunkley: to think on 11 year old level, but I'm 578 00:24:11.410 --> 00:24:13.290 thinking Thomas was probably much brighter at 579 00:24:13.290 --> 00:24:15.770 11 than I was struggle 580 00:24:15.770 --> 00:24:17.250 Professor Fred Watson: to get to 11. So do I. 581 00:24:17.570 --> 00:24:20.370 Andrew Dunkley: Yes, thanks Thomas. That was really terrific. 582 00:24:20.370 --> 00:24:22.290 Thanks for sending it in and uh, keep on 583 00:24:22.290 --> 00:24:22.850 listening. 584 00:24:26.930 --> 00:24:29.810 Professor Fred Watson: Tranquilly Base here. The eagle has landed. 585 00:24:29.810 --> 00:24:30.850 Professor Fred Watson: Space nets. 586 00:24:31.330 --> 00:24:34.240 Andrew Dunkley: Final question, Fred Watson, comes from Paul. 587 00:24:35.040 --> 00:24:36.880 Joe: Hello, Space Nights. Paul here from 588 00:24:36.880 --> 00:24:38.400 Sunnybris, Vegas, where it's currently 589 00:24:38.480 --> 00:24:41.400 bucketing down in what is being described 590 00:24:41.400 --> 00:24:44.000 as a rare rain occurrence. 591 00:24:45.200 --> 00:24:47.440 Anyway, I 592 00:24:48.320 --> 00:24:51.080 am currently looking through a very old book 593 00:24:51.080 --> 00:24:54.080 of mine. Guess it's old compared to 594 00:24:54.080 --> 00:24:56.840 these students I teach. It was published back 595 00:24:56.840 --> 00:24:59.840 in 1978. I think I got it in 1980 from 596 00:25:00.450 --> 00:25:02.600 uh, an uncle of mine, Uncle Jim. Thank you 597 00:25:02.600 --> 00:25:04.560 very much. It's called Stars and Planets and 598 00:25:04.560 --> 00:25:06.380 it's probably what got me into 599 00:25:07.340 --> 00:25:10.020 the whole field of astronomy in the first 600 00:25:10.020 --> 00:25:12.940 place. At least my interest in astronomy. 601 00:25:12.940 --> 00:25:13.740 Obviously 602 00:25:15.980 --> 00:25:17.100 Andrew Dunkley: very, uh, very grateful. 603 00:25:17.500 --> 00:25:20.140 Joe: I'm on the page where it's talking about 604 00:25:20.220 --> 00:25:22.620 how the American astronomer Carlo 605 00:25:22.620 --> 00:25:25.180 Shapley used 606 00:25:25.260 --> 00:25:28.260 the 1.5 metre reflector on 607 00:25:28.260 --> 00:25:30.540 top of Matt Wilson in California 608 00:25:31.830 --> 00:25:34.470 to work out that our sun is 609 00:25:34.790 --> 00:25:36.950 not at the centre of our galaxy. As was 610 00:25:36.950 --> 00:25:39.510 previously thought, but is about two thirds 611 00:25:39.510 --> 00:25:42.430 of the way to the edge. Could you 612 00:25:42.430 --> 00:25:45.430 please give us some idea how 613 00:25:45.430 --> 00:25:47.750 he actually managed to do that? 614 00:25:48.630 --> 00:25:50.990 Was it something about the 615 00:25:50.990 --> 00:25:53.670 density of stars? I mean, how many 616 00:25:53.670 --> 00:25:55.910 stars in the field of view? 617 00:25:56.370 --> 00:25:57.470 Andrew Dunkley: Uh, when you point it one way 618 00:25:57.470 --> 00:25:59.660 Joe: compared to the other other. How did you do 619 00:25:59.660 --> 00:26:01.940 it? I'm really curious and I know I could 620 00:26:01.940 --> 00:26:04.300 Google it, but I'd rather hear it from you 621 00:26:04.300 --> 00:26:07.220 guys. So thanks in advance. Love 622 00:26:07.220 --> 00:26:10.180 the show and dare I 623 00:26:10.180 --> 00:26:12.820 say, keep up the good work. Cheers. 624 00:26:13.380 --> 00:26:13.860 Professor Fred Watson: Cheers. 625 00:26:13.860 --> 00:26:15.840 Andrew Dunkley: Paul, thanks for sending that in. Uh, 626 00:26:16.900 --> 00:26:18.980 sending the question in and uh, we don't know 627 00:26:18.980 --> 00:26:21.820 the answer, so. But 628 00:26:21.820 --> 00:26:24.600 we're going to Google it. No, um, uh, 629 00:26:24.600 --> 00:26:26.920 1978, stars and planets. Uh, 630 00:26:27.520 --> 00:26:29.760 I tried to look it up. There are umpteen 631 00:26:29.840 --> 00:26:31.680 books named Stars and Planets. 632 00:26:31.680 --> 00:26:32.160 Professor Fred Watson: Yeah. 633 00:26:32.160 --> 00:26:34.280 Andrew Dunkley: So I haven't been able to, you know, 634 00:26:34.280 --> 00:26:36.600 distinguish one from the other as yet. So, 635 00:26:36.600 --> 00:26:39.560 um. Uh, yeah, you'll have to do some 636 00:26:39.560 --> 00:26:41.720 fishing to find the book that, uh, Paul was 637 00:26:41.720 --> 00:26:42.240 talking about. 638 00:26:42.240 --> 00:26:44.960 But he wanted to know about 639 00:26:45.280 --> 00:26:47.800 the man who decided or 640 00:26:47.800 --> 00:26:50.440 discovered that the sun was not the centre of 641 00:26:50.440 --> 00:26:53.320 everything. Uh, which was a common 642 00:26:53.320 --> 00:26:54.650 belief back in the day. 643 00:26:55.840 --> 00:26:58.400 Professor Fred Watson: It was, um, it was actually 1919 when that 644 00:26:58.400 --> 00:26:59.360 discovery was made. 645 00:27:00.000 --> 00:27:00.960 Andrew Dunkley: Was it that recent? 646 00:27:01.440 --> 00:27:04.440 Professor Fred Watson: Yeah. Wow. Uh, it's one of my favourite 647 00:27:04.440 --> 00:27:06.000 astronomical discoveries, which is why I 648 00:27:06.000 --> 00:27:08.080 didn't need to go to Google to look it up. 649 00:27:08.760 --> 00:27:11.440 Um, so it goes back to the time 650 00:27:11.520 --> 00:27:14.520 of William Herschel, uh, who was 651 00:27:14.520 --> 00:27:17.440 a German turned British 652 00:27:17.440 --> 00:27:20.360 astronomer, worked late in 653 00:27:20.360 --> 00:27:23.000 the 18th century and early in the 19th 654 00:27:23.000 --> 00:27:25.040 century, discovered the planet Uranus in 655 00:27:25.040 --> 00:27:27.900 1780. But what he was doing when 656 00:27:27.900 --> 00:27:30.420 he discovered Uranus was actually mapping the 657 00:27:30.420 --> 00:27:33.060 Milky Way. He was observing, um, 658 00:27:33.980 --> 00:27:36.780 the Milky Way in a very systematic way with a 659 00:27:36.780 --> 00:27:39.460 relatively small telescope. So sort of 660 00:27:39.460 --> 00:27:42.300 counting stars in the 661 00:27:42.300 --> 00:27:44.060 field of view of his telescope and then 662 00:27:44.060 --> 00:27:46.220 moving the telescope a bit further along the 663 00:27:46.220 --> 00:27:48.780 Milky Way, counting stars again, how many he 664 00:27:48.780 --> 00:27:51.420 could see in the field of view and doing that 665 00:27:51.420 --> 00:27:53.100 and doing it. He couldn't do it all the way 666 00:27:53.100 --> 00:27:54.700 around the Milky Way. Cause there's parts of 667 00:27:54.700 --> 00:27:56.460 it that he could never see because they're in 668 00:27:56.460 --> 00:27:58.840 the southern hemisphere. But he'd got round 669 00:27:58.840 --> 00:28:01.720 most of it. And what he discovered was that 670 00:28:02.520 --> 00:28:05.280 the star counts are pretty even all the way 671 00:28:05.280 --> 00:28:07.880 around. And so that led 672 00:28:08.440 --> 00:28:11.000 him to build the hypothesis that 673 00:28:11.240 --> 00:28:13.400 the stars are in a sort of flattened disc, 674 00:28:13.400 --> 00:28:16.120 which is correct. Uh, but that we're very 675 00:28:16.120 --> 00:28:18.120 near the middle, which is not correct. 676 00:28:18.760 --> 00:28:21.320 And the reason why he got that 677 00:28:21.320 --> 00:28:23.880 erroneous answer was that, uh, when you look 678 00:28:23.960 --> 00:28:26.180 through, I think it was a 7 inch telescope, 679 00:28:26.180 --> 00:28:28.940 if I remember right, a telescope of that 680 00:28:28.940 --> 00:28:31.380 size at, uh, the Milky Way, the stars that 681 00:28:31.380 --> 00:28:34.020 you see are all relatively 682 00:28:34.020 --> 00:28:36.820 nearby. They're perhaps 1000 683 00:28:36.820 --> 00:28:38.500 light years away or something like that, 684 00:28:38.500 --> 00:28:41.220 maybe a bit more, maybe a couple of thousand 685 00:28:41.220 --> 00:28:43.340 light years away in the plane of the Milky 686 00:28:43.340 --> 00:28:45.860 Way. And, uh, that's partly because the Milky 687 00:28:45.860 --> 00:28:48.540 Way is very dusty. Uh, there's a lot of dust 688 00:28:48.540 --> 00:28:50.660 everywhere. It's probably better described as 689 00:28:50.660 --> 00:28:53.140 smoke, but we call it dust in the world of 690 00:28:53.140 --> 00:28:55.940 astronomy. And so that dust limits how far 691 00:28:55.940 --> 00:28:58.480 you can see. And so when you look at the 692 00:28:58.480 --> 00:29:01.240 Milky Way, it does look generally relatively 693 00:29:01.240 --> 00:29:03.440 even. There's one bit in the constellation of 694 00:29:03.440 --> 00:29:06.000 Sagittarius where it's brighter and that's 695 00:29:06.000 --> 00:29:07.960 because you are looking towards, as we now 696 00:29:07.960 --> 00:29:10.760 know, the galactic centre. But, um, Herschel, 697 00:29:11.100 --> 00:29:13.240 um, he couldn't see that very well from the 698 00:29:13.240 --> 00:29:15.560 Northern hemisphere anyway. But he did sort 699 00:29:15.560 --> 00:29:18.440 of discount that. Uh, he said, by and large, 700 00:29:18.600 --> 00:29:21.520 it's the same count all the way around, so we 701 00:29:21.520 --> 00:29:24.440 must be in the middle, uh, roll 702 00:29:24.440 --> 00:29:27.240 on the years. And in 1919, Harlow 703 00:29:27.240 --> 00:29:29.640 Shapley, a very gifted American astronomer, 704 00:29:29.640 --> 00:29:31.520 although he did get one thing, one big thing 705 00:29:31.680 --> 00:29:34.480 wrong, uh, but what he did was 706 00:29:35.280 --> 00:29:37.160 he was interested in objects that we call 707 00:29:37.160 --> 00:29:39.639 globular clusters. And so these are, uh, in 708 00:29:39.639 --> 00:29:41.560 fact they were named by William Herschel. He 709 00:29:41.560 --> 00:29:43.640 gave them that name. Uh, clusters of stars 710 00:29:43.640 --> 00:29:46.400 that appear like a globe. Uh, and 711 00:29:47.600 --> 00:29:50.220 Harlow Shapley was, uh, 712 00:29:51.320 --> 00:29:53.560 he was interested in globular clusters. He 713 00:29:53.560 --> 00:29:56.280 noticed there were a lot of them in our, uh, 714 00:29:56.840 --> 00:29:59.840 skies. Uh, they tended 715 00:29:59.840 --> 00:30:02.320 to be different sizes. Uh, 716 00:30:02.680 --> 00:30:04.800 and he didn't know whether that was because 717 00:30:04.800 --> 00:30:06.400 they were all the same size and some were 718 00:30:06.400 --> 00:30:08.240 nearer than others or whether they were 719 00:30:08.240 --> 00:30:10.880 intrinsically different sizes. But what he 720 00:30:10.880 --> 00:30:13.320 did notice was that there's a concentration 721 00:30:13.400 --> 00:30:15.960 of them in the southern 722 00:30:15.960 --> 00:30:18.640 hemisphere sky. Uh, he was 723 00:30:18.640 --> 00:30:20.390 observing from California, so he could see, 724 00:30:20.540 --> 00:30:22.820 see a fair swath of the southern hemisphere 725 00:30:22.820 --> 00:30:25.540 sky. But he noticed that they were 726 00:30:25.540 --> 00:30:28.100 concentrated in that direction and that made 727 00:30:28.100 --> 00:30:30.940 him wonder if that 728 00:30:31.100 --> 00:30:33.180 was where the centre of the galaxy lay, 729 00:30:33.180 --> 00:30:36.130 rather than us being near the centre. Uh, 730 00:30:36.130 --> 00:30:38.980 but then his other step was that he 731 00:30:38.980 --> 00:30:41.580 recognised that within these globular 732 00:30:41.580 --> 00:30:44.540 clusters was something called, they 733 00:30:44.540 --> 00:30:47.380 called them cluster variables, stars that 734 00:30:47.380 --> 00:30:49.820 varied in a certain way with a 735 00:30:49.820 --> 00:30:52.720 periodicity of about a day. Uh, today 736 00:30:52.720 --> 00:30:55.040 we call them RR liry variables. And I 737 00:30:55.040 --> 00:30:56.760 actually started my astronomical research 738 00:30:56.840 --> 00:30:59.000 back in the 70s studying these things, 739 00:30:59.710 --> 00:31:02.360 uh, RR variables. Uh, and 740 00:31:03.720 --> 00:31:06.640 they are good because they've 741 00:31:06.640 --> 00:31:09.160 got basically a known distance. 742 00:31:09.710 --> 00:31:12.360 Uh, if you can see an RR 743 00:31:12.520 --> 00:31:15.400 variable and identify it as one, you know how 744 00:31:15.400 --> 00:31:18.360 intrinsically bright it is, uh, and then from 745 00:31:18.360 --> 00:31:20.920 that you can work out how far away it is. 746 00:31:21.240 --> 00:31:24.190 And so he found these variable stars in the 747 00:31:24.340 --> 00:31:27.180 globular clusters and recognised that he 748 00:31:27.180 --> 00:31:29.780 could draw a chart with the globular 749 00:31:29.780 --> 00:31:32.740 clusters all at their correct distance on it, 750 00:31:32.740 --> 00:31:35.340 make a kind of three dimensional map of the 751 00:31:35.340 --> 00:31:37.500 sky and sure enough, um, they 752 00:31:37.500 --> 00:31:40.220 concentrated around the galactic 753 00:31:40.220 --> 00:31:42.980 centre around a point. Uh, he actually got 754 00:31:42.980 --> 00:31:45.220 the answer wrong because his magnitude, his 755 00:31:45.220 --> 00:31:47.900 brightness that he had for the, uh, cluster 756 00:31:47.900 --> 00:31:50.860 variables was incorrect. And I can't remember 757 00:31:50.860 --> 00:31:53.530 what answer he got, but in my modern PARLANCE 758 00:31:54.090 --> 00:31:56.490 it's about 25,000 light years. 759 00:31:57.770 --> 00:32:00.370 The globular clusters themselves cluster 760 00:32:00.370 --> 00:32:03.290 around a point about 25,000 light years 761 00:32:03.290 --> 00:32:05.650 away, which is deeply hidden by the dust 762 00:32:05.650 --> 00:32:08.569 clouds in Sagittarius. So he 763 00:32:08.730 --> 00:32:10.490 figured out that that's where the centre of 764 00:32:10.490 --> 00:32:12.490 the galaxy was. A brilliant piece of 765 00:32:12.490 --> 00:32:15.320 detective work. We know he was right. Uh, 766 00:32:15.450 --> 00:32:18.250 what he was wrong about was, uh, he had a big 767 00:32:18.250 --> 00:32:21.210 discussion, I think in 1923, 768 00:32:21.690 --> 00:32:24.390 just before Hubble recogn that 769 00:32:24.390 --> 00:32:27.200 galaxies were big things a long way away. Uh, 770 00:32:27.200 --> 00:32:29.790 Shapley was arguing that galaxies lie within 771 00:32:29.790 --> 00:32:32.110 our own Milky Way, that they're small objects 772 00:32:32.110 --> 00:32:34.800 in our own Milky Way. And he was, um, 773 00:32:35.350 --> 00:32:37.550 arguing. It was a public debate actually, 774 00:32:37.550 --> 00:32:39.510 between Shapley and a guy called Heber 775 00:32:39.510 --> 00:32:42.270 Curtis. Uh, Curtis had the answer right. He 776 00:32:42.270 --> 00:32:44.550 said they're big and a long way off. Uh, 777 00:32:44.630 --> 00:32:46.950 Shapley said, no, they're small and nearby. 778 00:32:47.030 --> 00:32:49.230 And it was very soon after that that Hubble 779 00:32:49.230 --> 00:32:51.060 produced that they're big and a long way. Uh, 780 00:32:51.280 --> 00:32:53.150 uh, proved that they're big and a long way 781 00:32:53.150 --> 00:32:55.510 off. So Shapley was wrong in that, but he was 782 00:32:55.510 --> 00:32:57.010 right about galactic centre. 783 00:32:57.730 --> 00:33:00.450 Andrew Dunkley: Fantastic. Gee whiz. Um, great 784 00:33:00.450 --> 00:33:03.340 question, Paul. And, um, yeah, uh, 785 00:33:03.340 --> 00:33:05.650 if people are looking for that, uh, book 786 00:33:06.050 --> 00:33:08.780 Stars and Planets, uh, it is out there. Uh, 787 00:33:08.850 --> 00:33:11.010 look, I've found a couple that were actually 788 00:33:11.010 --> 00:33:13.330 published around that time that Paul 789 00:33:13.330 --> 00:33:15.770 mentioned, but not, um, sure if they're the 790 00:33:15.770 --> 00:33:18.390 ones. I can't remember the author now, um, 791 00:33:18.390 --> 00:33:19.690 that he said, but I don't think 792 00:33:19.690 --> 00:33:21.010 Professor Fred Watson: anyway, mentioned an author. 793 00:33:21.170 --> 00:33:22.930 Andrew Dunkley: I thought he did, but, uh, he might have 794 00:33:22.930 --> 00:33:23.250 mentioned it. 795 00:33:23.480 --> 00:33:23.880 Joe: Uncle. 796 00:33:24.200 --> 00:33:25.440 Professor Fred Watson: It was his uncle he mentioned. 797 00:33:25.440 --> 00:33:25.800 Andrew Dunkley: Uncle. 798 00:33:25.880 --> 00:33:26.680 Professor Fred Watson: Uncle Jim. 799 00:33:27.080 --> 00:33:28.630 Andrew Dunkley: Right. But, um, 800 00:33:30.340 --> 00:33:32.920 um, so, yeah, thanks, Paul. Thanks for the 801 00:33:32.920 --> 00:33:35.480 question. And, um, yeah, it's a fascinating, 802 00:33:35.600 --> 00:33:38.280 um, history in astronomy as we discover these 803 00:33:38.280 --> 00:33:40.040 things. I think one of my favourite 804 00:33:40.840 --> 00:33:43.800 moments, I suppose, in astronomical history 805 00:33:43.800 --> 00:33:46.640 was when they discovered that our sun was a 806 00:33:46.640 --> 00:33:46.920 star. 807 00:33:48.360 --> 00:33:50.920 Professor Fred Watson: M. That was a long time ago. Yeah, 808 00:33:51.200 --> 00:33:51.520 yeah. 809 00:33:51.600 --> 00:33:54.160 Andrew Dunkley: But for a while there we didn't think of It. 810 00:33:54.160 --> 00:33:55.440 Professor Fred Watson: I thought it was something else. That's 811 00:33:55.440 --> 00:33:58.240 right. Something a bit special. Yeah. 812 00:33:58.580 --> 00:34:01.520 Andrew Dunkley: Um, and I saw that on a BBC documentary 813 00:34:01.520 --> 00:34:03.200 many years ago and I sat there and went, 814 00:34:04.240 --> 00:34:06.560 wow. I never thought about that because I've 815 00:34:06.560 --> 00:34:09.040 always known it to be a star, but for 816 00:34:09.360 --> 00:34:10.960 generations they didn't. 817 00:34:12.880 --> 00:34:15.320 Quite intriguing. And why would you. It 818 00:34:15.320 --> 00:34:16.480 doesn't look like a star. 819 00:34:17.440 --> 00:34:20.380 Professor Fred Watson: That's right. Uh, uh, it's 820 00:34:20.380 --> 00:34:22.179 clearly quite different from a star. Uh, 821 00:34:23.980 --> 00:34:24.580 Andrew Dunkley: incredible. 822 00:34:24.580 --> 00:34:26.380 Thanks, Paul. Thanks for sending that in. And 823 00:34:26.380 --> 00:34:29.140 if you have a question for. Thanks to all our 824 00:34:29.140 --> 00:34:31.500 sender innerers, I've always wanted to say 825 00:34:31.500 --> 00:34:33.420 that, uh, for their questions. And if you 826 00:34:33.420 --> 00:34:34.860 would like to send a question, go to our 827 00:34:34.860 --> 00:34:37.300 website, spacenutspodcast.com or 828 00:34:37.300 --> 00:34:40.220 spacenuts IO and there's a little 829 00:34:40.220 --> 00:34:43.020 AMA M tab at the top, which stands for Ask 830 00:34:43.020 --> 00:34:45.380 me anything. Not me personally, it's the 831 00:34:45.380 --> 00:34:48.349 rookie royal me. And, um, 832 00:34:48.570 --> 00:34:50.770 just put your, uh, question in there. It can 833 00:34:50.770 --> 00:34:53.090 be text or audio. Don't forget to tell us who 834 00:34:53.090 --> 00:34:54.530 you are and where you're from and have a look 835 00:34:54.530 --> 00:34:56.250 around. While you're there, don't forget to 836 00:34:56.250 --> 00:34:59.210 leave a review at your favourite podcasting 837 00:34:59.370 --> 00:35:01.130 platform. We're all done. Thanks, 838 00:35:01.130 --> 00:35:01.530 Fred Watson. 839 00:35:02.010 --> 00:35:04.930 Professor Fred Watson: A great pleasure, Andrew. Um, we, uh, 840 00:35:04.930 --> 00:35:07.530 continue to get great questions from great 841 00:35:07.530 --> 00:35:09.770 listeners and long may it continue. Thank 842 00:35:09.770 --> 00:35:09.930 you. 843 00:35:09.930 --> 00:35:12.630 Andrew Dunkley: Yes, indeed, we continue to solve and evolve. 844 00:35:13.830 --> 00:35:14.940 Um, maybe not. 845 00:35:15.260 --> 00:35:16.220 Professor Fred Watson: I'm not evolving. 846 00:35:18.220 --> 00:35:21.180 Andrew Dunkley: Once you reach a certain age, evolving 847 00:35:21.180 --> 00:35:23.500 just is not part of the programme. That's 848 00:35:23.500 --> 00:35:23.820 right. 849 00:35:23.900 --> 00:35:24.380 Professor Fred Watson: Yeah. 850 00:35:24.460 --> 00:35:26.860 Andrew Dunkley: Ask my mum on the Internet. Uh, thanks, 851 00:35:26.860 --> 00:35:27.900 Fred Watson. We'll see you soon. 852 00:35:28.300 --> 00:35:29.740 Professor Fred Watson: Sounds great. Thanks, Andrea. 853 00:35:29.740 --> 00:35:31.380 Andrew Dunkley: Professor Fred Watson Watson, astronomer at 854 00:35:31.380 --> 00:35:33.140 large. And thanks to Huw in the studio. He's 855 00:35:33.140 --> 00:35:35.940 just turned up. Um, we started 39 856 00:35:35.940 --> 00:35:38.740 minutes ago and, um, Huw set his 857 00:35:38.740 --> 00:35:41.380 clock to a Martian day, so that's why he's 858 00:35:41.380 --> 00:35:42.270 39 minutes late. 859 00:35:42.820 --> 00:35:43.380 Professor Fred Watson: Boom, boom. 860 00:35:43.460 --> 00:35:45.260 Andrew Dunkley: And from me, Andrew Dunkley, thanks for your 861 00:35:45.260 --> 00:35:47.380 company. We'll see you on the next episode of 862 00:35:47.380 --> 00:35:48.100 Space Nuts. 863 00:35:48.100 --> 00:35:48.740 Professor Fred Watson: Bye. Bye. 864 00:35:49.780 --> 00:35:52.060 Joe: You've been listening to the Space Nuts 865 00:35:52.060 --> 00:35:55.020 Andrew Dunkley: podcast, available at 866 00:35:55.020 --> 00:35:56.980 Apple Podcasts, Spotify, 867 00:35:57.140 --> 00:35:59.900 iHeartRadio or your favourite podcast 868 00:35:59.900 --> 00:36:01.620 player. You can also stream on 869 00:36:01.620 --> 00:36:04.620 demand@bytes.com. this has been another 870 00:36:04.620 --> 00:36:06.700 quality podcast production from 871 00:36:06.700 --> 00:36:07.860 bytes.com.