رونوشت کامل Waves, Signals, and Cosmic Aromas: A Q&A Journey Through Space

84 00:03:11.230 --> 00:03:13.710 Jonti Horner: Crack the big whips and all the rest of it. 85 00:03:13.710 --> 00:03:16.590 Andrew Dunkley: But yeah, yeah, no, it's fascinating 86 00:03:16.590 --> 00:03:18.469 history. Wouldn't you love a time machine 87 00:03:18.469 --> 00:03:20.190 just to go back and go, ah, uh, look. 88 00:03:20.190 --> 00:03:20.590 Andrew Dunkley: Yeah, 89 00:03:22.910 --> 00:03:25.230 Andrew Dunkley: now that we're seeing it, it looks easy. 90 00:03:25.840 --> 00:03:27.830 Jonti Horner: Uh, absolutely. I mean, I probably end up 91 00:03:27.830 --> 00:03:29.590 being really kind of busman's holiday though, 92 00:03:29.590 --> 00:03:31.350 with the time machine and going back to 93 00:03:31.350 --> 00:03:33.990 different astronomical events and think like, 94 00:03:33.990 --> 00:03:35.810 trying figure out if Caesar's Comet was 95 00:03:35.810 --> 00:03:38.090 actually real, you know, and, you know, 96 00:03:38.090 --> 00:03:40.810 trying to see if there were multiple sun 97 00:03:40.810 --> 00:03:42.850 grazing comets visible with the naked eye in 98 00:03:42.850 --> 00:03:45.850 daylight in I think it was 363 A.D. so 99 00:03:45.850 --> 00:03:47.410 I'd probably end up picking myself an 100 00:03:47.410 --> 00:03:50.270 astronomical holiday tour, um, 101 00:03:51.210 --> 00:03:52.930 not getting distracted by all the kind of 102 00:03:52.930 --> 00:03:54.170 human history stuff. 103 00:03:54.410 --> 00:03:56.730 Andrew Dunkley: Yeah, fair enough. I mean, you go nuts 104 00:03:56.810 --> 00:03:58.730 thinking about things to go back and see. 105 00:03:58.970 --> 00:03:59.610 Absolutely. 106 00:03:59.610 --> 00:04:01.850 Jonti Horner: Or going forward. I've said a few times that 107 00:04:01.930 --> 00:04:03.770 given the predictions we talked about last 108 00:04:03.770 --> 00:04:06.160 year, that Comet Duchesso, Comic 109 00:04:06.230 --> 00:04:08.950 Linkenberg, will return in the year 2097. 110 00:04:09.430 --> 00:04:11.350 That could well be the best comet of this 111 00:04:11.350 --> 00:04:13.910 century. I'd quite like to see it, but 112 00:04:14.390 --> 00:04:17.350 unless I am fortunate enough to reach 119 113 00:04:17.350 --> 00:04:20.150 years old, I think it unlikely. So, 114 00:04:20.230 --> 00:04:21.910 you know, time machine would be welcome. 115 00:04:22.310 --> 00:04:25.190 Andrew Dunkley: Yeah, it would. I'm working on it. 116 00:04:26.790 --> 00:04:28.830 Uh, so let's go to the first part of the 117 00:04:28.830 --> 00:04:31.110 question. Uh, how is a photographic image 118 00:04:31.110 --> 00:04:33.750 produced from a radio telescope when 119 00:04:33.830 --> 00:04:35.990 all they receive is radio waves and not an 120 00:04:35.990 --> 00:04:38.810 optical image through a telescope lens? Yeah, 121 00:04:38.810 --> 00:04:41.330 I've got to admit, this one confuses me a 122 00:04:41.330 --> 00:04:41.570 bit. 123 00:04:42.690 --> 00:04:44.810 Jonti Horner: We could say the same for infrared. We could 124 00:04:44.810 --> 00:04:47.530 say the same for gamma rays or X rays or for 125 00:04:47.530 --> 00:04:49.930 optical photographs. Right. So all of those 126 00:04:49.930 --> 00:04:51.890 different forms of radiation I just mentioned 127 00:04:51.890 --> 00:04:53.450 are different, uh, parts of the 128 00:04:53.450 --> 00:04:54.970 electromagnetic spectrum. So they're 129 00:04:54.970 --> 00:04:56.410 fundamentally the same thing but with 130 00:04:56.410 --> 00:04:58.650 different wavelengths in just the same way 131 00:04:58.650 --> 00:05:00.210 that red light and blue light are 132 00:05:00.210 --> 00:05:02.930 electromagnetic waves, but blue has a shorter 133 00:05:02.930 --> 00:05:04.850 wavelength and red has a longer wavelength. 134 00:05:05.330 --> 00:05:07.650 And um, I've got an astro photo behind me of 135 00:05:07.650 --> 00:05:10.530 the Helix Nebula. If I had a camera that was 136 00:05:10.530 --> 00:05:12.090 more sensitive to infrared, I would have 137 00:05:12.090 --> 00:05:13.770 picked out some slightly different features 138 00:05:13.770 --> 00:05:16.450 there because there is radiation coming in of 139 00:05:16.450 --> 00:05:19.450 different wavelengths. The way it 140 00:05:19.450 --> 00:05:21.970 works with a radio telescope or the way that 141 00:05:21.970 --> 00:05:24.010 it works with an M infrared detector or 142 00:05:24.010 --> 00:05:26.490 whatever is, you've got a detector 143 00:05:26.890 --> 00:05:29.770 that can detect radiation of that 144 00:05:29.770 --> 00:05:32.650 wavelength. Um, with an optical photo, 145 00:05:33.050 --> 00:05:35.770 you have a DSLR camera or a CCD camera that 146 00:05:35.770 --> 00:05:38.170 is sensitive to optical light and 147 00:05:38.710 --> 00:05:41.230 you get photons hitting the detector and 148 00:05:41.230 --> 00:05:43.670 creating electrons that are countered in the 149 00:05:43.670 --> 00:05:45.470 same way. For a radio telescope, you have a 150 00:05:45.470 --> 00:05:47.990 detector that is sensitive to radio waves 151 00:05:48.230 --> 00:05:50.550 and when photons of the right energy hit the 152 00:05:50.550 --> 00:05:52.790 detector, they create electrons and they get 153 00:05:52.790 --> 00:05:55.510 countered. So what happens is you've got your 154 00:05:55.510 --> 00:05:58.350 radio telescope that can look at a patch of 155 00:05:58.350 --> 00:06:01.150 sky with some level of 156 00:06:01.150 --> 00:06:03.750 resolution and some telescopes have 157 00:06:04.640 --> 00:06:06.320 better resolution and some have blurrier 158 00:06:06.320 --> 00:06:08.720 vision linked to the size of the telescope. 159 00:06:08.880 --> 00:06:10.840 Typically, the bigger a telescope is, the 160 00:06:10.840 --> 00:06:13.760 better its resolution will be. For optical 161 00:06:13.760 --> 00:06:15.640 telescopes, the atmosphere puts a cap on 162 00:06:15.640 --> 00:06:17.200 that. Uh, unless you can do things to filter 163 00:06:17.200 --> 00:06:20.079 it out at about 1 arc second, very 164

00:06:20.079 --> 00:06:23.040 roughly, the turbulence of the 165 00:06:23.040 --> 00:06:25.680 atmosphere is a bit of a pain. But in theory, 166 00:06:25.680 --> 00:06:27.320 if you could take the atmosphere away, you 167 00:06:27.320 --> 00:06:30.120 would be able to see smaller things on the 168 00:06:30.120 --> 00:06:32.480 sky with a 10 metre diameter telescope than a 169 00:06:32.480 --> 00:06:35.130 1 metre telescope in the optical. And there's 170 00:06:35.130 --> 00:06:36.730 a mathematical relation for this that we 171 00:06:36.730 --> 00:06:39.530 teach our students at undergrad level. The 172 00:06:39.530 --> 00:06:41.690 resolution of the telescope, so what the 173 00:06:41.690 --> 00:06:43.810 smallest thing it can see is, if you ignore 174 00:06:43.810 --> 00:06:45.330 the atmosphere, if you look purely on the 175 00:06:45.330 --> 00:06:48.290 physics of it, is related to 176 00:06:48.290 --> 00:06:49.810 the diameter of the telescope. A bigger 177 00:06:49.810 --> 00:06:52.210 telescope will see a smaller resolution, but 178 00:06:52.210 --> 00:06:55.010 it's also related to the wavelength. So if 179 00:06:55.010 --> 00:06:57.690 you've got two telescopes of identical size 180 00:06:57.690 --> 00:06:59.730 and one's looking at optical and one's 181 00:06:59.730 --> 00:07:02.210 looking at radio waves, the radio waves are 182 00:07:02.210 --> 00:07:04.250 much longer wavelength, so the resolution of 183 00:07:04.250 --> 00:07:06.000 that telescope will be much lower. 184 00:07:07.190 --> 00:07:09.390 So radio telescopes of the same size as an 185 00:07:09.390 --> 00:07:11.430 optical telescope will get a blurrier image, 186 00:07:11.990 --> 00:07:14.230 but we can build radio telescopes much 187 00:07:14.230 --> 00:07:16.670 bigger. So there's swings and 188 00:07:16.670 --> 00:07:19.630 roundabouts there. But effectively what 189 00:07:19.630 --> 00:07:22.070 happens is you've got your image 190 00:07:22.470 --> 00:07:24.310 of the sky, the telescope looking at a patch 191 00:07:24.310 --> 00:07:27.190 of sky, and you've got a detector that 192 00:07:27.270 --> 00:07:30.070 counts the amount of radio waves 193 00:07:30.150 --> 00:07:31.950 impacting upon it in the form of photons 194 00:07:31.950 --> 00:07:33.910 impacting upon it. And that gives you a 195 00:07:33.910 --> 00:07:35.830 measure of how bright that bit of sky is. 196 00:07:36.550 --> 00:07:39.490 Now, if you've got multiple pixels, you can 197 00:07:39.490 --> 00:07:42.130 see different bits of that, uh, image 198 00:07:42.210 --> 00:07:45.090 in the same way as with a normal camera. One 199 00:07:45.090 --> 00:07:47.250 way. I think that this used to be done back 200 00:07:47.250 --> 00:07:49.970 in the very early days of radio or Ah, with 201 00:07:49.970 --> 00:07:51.930 very simple radio telescopes was all you're 202 00:07:51.930 --> 00:07:54.490 doing is you're counting the amount of radio 203 00:07:54.490 --> 00:07:56.530 waves hitting your detector. So you've got 204 00:07:56.530 --> 00:07:58.570 one pixel for your entire field of view and 205 00:07:58.570 --> 00:08:00.890 then you move your field around to make an 206 00:08:00.890 --> 00:08:02.930 image. So this part of the sky is this 207 00:08:02.930 --> 00:08:04.730 bright, the one next to it is this bright and 208 00:08:04.730 --> 00:08:06.650 so on, and you raster around to build up an 209 00:08:06.650 --> 00:08:09.410 image, you move around. Nowadays I 210 00:08:09.410 --> 00:08:12.210 think that you can get multiple pixels per 211 00:08:12.210 --> 00:08:14.370 field of view. In fact, you can get many. 212 00:08:14.370 --> 00:08:16.050 That's why we can get these beautiful high 213 00:08:16.050 --> 00:08:18.730 resolution images. And, uh, it's effectively 214 00:08:18.730 --> 00:08:21.290 working, albeit at different wavelengths, in 215 00:08:21.290 --> 00:08:24.090 the same kind of general science way as an 216 00:08:24.090 --> 00:08:26.250 optical detector. In that you've got a grid 217 00:08:26.250 --> 00:08:29.090 of pixels. Each pixel is sensitive 218 00:08:29.090 --> 00:08:31.770 to light falling upon that pixel and that 219 00:08:31.770 --> 00:08:34.690 pixel is seeing a certain bit of the sky. So 220 00:08:34.690 --> 00:08:36.610 you get a measure of how bright one bit of 221 00:08:36.610 --> 00:08:38.250 the sky is, how bright the next one is, how 222 00:08:38.250 --> 00:08:40.870 bright the next one is. That then gives you 223 00:08:40.870 --> 00:08:43.430 bright and faint. So you can then make a 224 00:08:43.430 --> 00:08:46.350 monochrome image where you plot 225 00:08:46.430 --> 00:08:48.790 those brightnesses as colours, from black 226 00:08:48.790 --> 00:08:51.470 being no light to white being some light and, 227 00:08:51.470 --> 00:08:53.990 um, really bright white being the 228 00:08:53.990 --> 00:08:55.830 brightest. Right. So you can build up an 229 00:08:55.830 --> 00:08:58.830 image where each pixel is a different 230 00:08:58.830 --> 00:09:01.150 brightness. Suddenly you've got a picture. 231 00:09:01.470 --> 00:09:02.030 Andrew Dunkley: Yeah. 232 00:09:02.110 --> 00:09:03.990 Jonti Horner: What you can do then is if you're sensitive 233 00:09:03.990 --> 00:09:06.630 to different wavelengths, you can 234 00:09:06.630 --> 00:09:08.870 combine those monochromatic images to make a 235 00:09:08.870 --> 00:09:11.390 colour image just the same way as I did with 236 00:09:11.390 --> 00:09:13.750 the one behind me. So the picture I've got on 237 00:09:13.750 --> 00:09:15.390 my screen, and this is useless to those of 238 00:09:15.390 --> 00:09:17.270 you listening, but anybody live in the 239 00:09:17.270 --> 00:09:18.950 studio, I've got a picture behind me of the 240 00:09:18.950 --> 00:09:21.790 Helix Nebula, which I took with my telescope 241 00:09:21.790 --> 00:09:24.190 here. And it's a beautiful kind of true 242 00:09:24.190 --> 00:09:25.909 colour image with a little bit of hydrogen 243 00:09:25.909 --> 00:09:28.430 alpha

added for those listening in. But what 244 00:09:28.430 --> 00:09:30.310 I've done here is taken images that were 245 00:09:30.310 --> 00:09:32.230 black and white, that were taken through 246 00:09:32.230 --> 00:09:35.190 filters of blue, green and 247 00:09:35.190 --> 00:09:37.810 red and combine them to make a colour image. 248 00:09:37.970 --> 00:09:39.690 So you can do that to make false colour 249 00:09:39.690 --> 00:09:42.440 images in infrared or radio, uh, 250 00:09:42.450 --> 00:09:45.330 or whatever. Sometimes what you're seeing 251 00:09:45.330 --> 00:09:47.370 is effectively a monochromatic image, but 252 00:09:47.370 --> 00:09:48.690 instead of black and white, they've used 253 00:09:48.690 --> 00:09:50.330 black and yellow to make it look nice and 254 00:09:50.330 --> 00:09:52.810 colourful. But that's effectively what's 255 00:09:52.810 --> 00:09:54.650 going on. Now, I'm not a radio astronomer. 256 00:09:54.650 --> 00:09:57.210 There's subtleties and differences in the 257 00:09:57.210 --> 00:09:58.880 technology you need to observe at, ah, 258 00:09:58.970 --> 00:10:01.810 different wavelengths compared to optical. 259 00:10:01.810 --> 00:10:03.450 And I know that's equally true of the very 260 00:10:03.450 --> 00:10:05.490 high energy stuff like gamma rays and X rays 261 00:10:05.490 --> 00:10:07.560 that need clever little Bits of technology. 262 00:10:07.710 --> 00:10:09.910 Technology to be done. But fundamentally what 263 00:10:09.910 --> 00:10:11.950 you're doing to get an image is you're 264 00:10:11.950 --> 00:10:13.790 measuring the brightness of the sky in a 265 00:10:13.790 --> 00:10:16.230 given position at the wavelength you're 266 00:10:16.230 --> 00:10:18.910 interested in and ascribing that a colour. 267 00:10:18.990 --> 00:10:21.510 And then you're building a grid of those to 268 00:10:21.510 --> 00:10:23.190 make a picture which shows you the brighter 269 00:10:23.190 --> 00:10:25.630 areas and the fainter areas. And that's 270 00:10:25.710 --> 00:10:27.670 pretty much the same no matter what you're 271 00:10:27.670 --> 00:10:30.670 looking at. It's the same technique. It's 272 00:10:30.670 --> 00:10:32.230 just using different technology because 273 00:10:32.230 --> 00:10:34.300 you're looking at different energy levels, 274 00:10:34.300 --> 00:10:35.300 different wavelengths, 275 00:10:35.860 --> 00:10:38.640 Andrew Dunkley: which is how they got the, uh, 276 00:10:38.740 --> 00:10:41.460 image of Sagittarius A and 277 00:10:41.700 --> 00:10:43.620 m. Was it M37? 278 00:10:44.820 --> 00:10:46.540 Jonti Horner: Was it the one at the middle of M81? 279 00:10:46.540 --> 00:10:48.100 Andrew Dunkley: I think M81, yeah. 280 00:10:48.260 --> 00:10:50.740 Jonti Horner: So that's the, um, big global Black hole 281 00:10:50.740 --> 00:10:52.500 telescope. I can't remember the exact name of 282 00:10:52.500 --> 00:10:55.420 it, that took advantage of the 283 00:10:55.420 --> 00:10:58.180 long wavelength because you can

do very 284 00:10:58.180 --> 00:11:01.020 clever things if you can work out 285 00:11:01.020 --> 00:11:03.700 where in a particular way of your 286 00:11:03.700 --> 00:11:06.540 detectors picking things up. So you can have 287 00:11:06.540 --> 00:11:09.420 distributed detectors that are part of the 288 00:11:09.420 --> 00:11:12.420 same telescope. Now, it's really hard to 289 00:11:12.420 --> 00:11:14.340 do this with optical. So, uh, people are 290 00:11:14.340 --> 00:11:15.980 playing with interferometry and things like 291 00:11:15.980 --> 00:11:18.540 that, uh, optical wavelengths. But for 292 00:11:18.860 --> 00:11:21.860 radio waves, it's possible for you to use 293 00:11:21.860 --> 00:11:24.700 detectors scattered all around the world to 294 00:11:24.700 --> 00:11:26.980 mimic having a detector that is a radio 295 00:11:26.980 --> 00:11:28.780 telescope that is the size of the Earth. 296 00:11:28.940 --> 00:11:29.370 Andrew Dunkley: Yeah. 297 00:11:29.610 --> 00:11:32.440 Jonti Horner: Um, and that then overcomes the problem that 298 00:11:32.440 --> 00:11:34.520 the wavelengths are longer by having a 299 00:11:34.520 --> 00:11:36.920 detector that is much, much bigger to get the 300 00:11:36.920 --> 00:11:38.600 kind of resolution that you get with an 301 00:11:38.600 --> 00:11:41.360 optical telescope or even better. And it's 302 00:11:41.360 --> 00:11:42.960 using that that they were able to get these 303 00:11:42.960 --> 00:11:45.439 beautiful resolved radio images of these 304 00:11:45.439 --> 00:11:48.320 black holes. They overcame the tyranny of 305 00:11:48.320 --> 00:11:50.640 resolution being, you know, 306 00:11:50.880 --> 00:11:53.360 limited by wavelength by making a really, 307 00:11:53.360 --> 00:11:55.360 really, really big telescope, effectively. 308 00:11:55.750 --> 00:11:58.400 Andrew Dunkley: M. Yeah, it worked really well. And so those 309 00:11:58.480 --> 00:12:00.880 images are a fair representation of what 310 00:12:01.580 --> 00:12:03.100 with the naked eye, from a distance. 311 00:12:03.100 --> 00:12:05.660 Jonti Horner: I suppose if you could see radio waves. 312 00:12:05.740 --> 00:12:07.260 Andrew Dunkley: Yeah, if you could, yes. 313 00:12:07.420 --> 00:12:08.820 Jonti Horner: Things will look different at, ah, different 314 00:12:08.820 --> 00:12:11.060 wavelengths. And you see that if you do play 315 00:12:11.060 --> 00:12:13.100 with astrophotography and you look through 316 00:12:13.100 --> 00:12:15.500 different filters, it is quite striking how 317 00:12:15.500 --> 00:12:17.020 different the same object will look in 318 00:12:17.020 --> 00:12:18.500 different colours when you're just looking in 319 00:12:18.500 --> 00:12:20.820 monochrome. And that's fundamentally how we 320 00:12:20.820 --> 00:12:22.540 do a lot of the science, how we work out what 321 00:12:22.540 --> 00:12:23.420 things are made of. 322 00:12:23.660 --> 00:12:26.060 Andrew Dunkley: Yeah, thank you, Thomas, Great question. 323 00:12:26.060 --> 00:12:28.900 Lovely to hear from you. Um, notwithstanding 324 00:12:28.900 --> 00:12:30.220 the Monty Python joke, 325 00:12:32.880 --> 00:12:33.120 Generic: Roger 326 00:12:33.120 --> 00:12:35.600 Jonti Horner: in your lives right here. Also space nuts. 327 00:12:36.000 --> 00:12:38.400 Andrew Dunkley: Our, uh, next question comes from 328 00:12:38.800 --> 00:12:41.720 Dean. Uh, he's not far from 329 00:12:41.720 --> 00:12:42.840 you Hi 330 00:12:42.840 --> 00:12:44.440 Andrew Dunkley: Fred Watson and Andrew, this is Dean in 331 00:12:44.440 --> 00:12:47.240 Redcliffe in Queensland. I often hear about 332 00:12:47.240 --> 00:12:49.640 gravity waves and I get a mental picture of a 333 00:12:49.640 --> 00:12:52.080 compression wave with dispersed particles in 334 00:12:52.080 --> 00:12:54.440 space getting closer together, then further 335 00:12:54.440 --> 00:12:57.160 apart as the wave passes. But I have a 336 00:12:57.160 --> 00:12:59.320 harder time visualising what happens as the 337 00:12:59.320 --> 00:13:01.950 wave passes through a solid body such as the 338 00:13:01.950 --> 00:13:04.270 Earth, where it can be detected by the LIGO 339 00:13:04.270 --> 00:13:07.030 interferometer. I think 340 00:13:07.030 --> 00:13:09.430 that it is space that is expanding and 341 00:13:09.430 --> 00:13:11.670 contracting rather than matter. But I'm not 342 00:13:11.670 --> 00:13:14.270 sure LIGO detects the 343 00:13:14.270 --> 00:13:16.310 gravity wave because the length of the four 344 00:13:16.310 --> 00:13:18.550 kilometre tunnel changes slightly. 345 00:13:19.110 --> 00:13:21.030 What's happening at a quantum scale 346 00:13:21.990 --> 00:13:24.510 as there is space within an atom, does the 347 00:13:24.510 --> 00:13:27.350 size of the atoms change or is it just the 348 00:13:27.350 --> 00:13:30.240 space between the atoms? I know 349 00:13:30.240 --> 00:13:32.520 that the effect at quantum scale would be 350 00:13:32.520 --> 00:13:34.880 minute. It's interesting to think about where 351 00:13:34.880 --> 00:13:37.880 the limit of space stretching might be. I 352 00:13:37.880 --> 00:13:39.600 suspect that I'm missing something with my 353 00:13:39.600 --> 00:13:41.960 understanding of this. I hope you can make 354 00:13:41.960 --> 00:13:44.440 some sense of it. Thanks for the podcast. 355 00:13:45.560 --> 00:13:47.960 Andrew Dunkley: Thank you, Dean. And uh, yeah, 356 00:13:48.440 --> 00:13:50.160 I think he's actually referring to 357 00:13:50.160 --> 00:13:52.720 gravitational waves because that's what LIGO 358 00:13:52.720 --> 00:13:55.400 searches for. But um, yeah, I've made that 359 00:13:55.400 --> 00:13:57.520 same mistake in the past where I call them 360 00:13:57.520 --> 00:14:00.280 gravity waves. Um, but 361 00:14:00.280 --> 00:14:01.820 gravity waves, wave is a different thing. 362 00:14:01.820 --> 00:14:03.940 They exist too, I think. 363 00:14:04.250 --> 00:14:07.100 Jonti Horner: Um, yes and no. So what's strange here is

364 00:14:07.100 --> 00:14:09.340 that I think you hear different terminology 365 00:14:09.340 --> 00:14:11.980 in different disciplines. So I think a lot of 366 00:14:11.980 --> 00:14:14.100 astronomers I've heard use the term gravity 367 00:14:14.100 --> 00:14:15.700 waves and gravitational waves almost 368 00:14:15.700 --> 00:14:17.900 interchangeably because that's what they're 369 00:14:17.900 --> 00:14:19.700 thinking about. But it's a really good 370 00:14:19.700 --> 00:14:22.340 example of how language is contextual 371 00:14:23.060 --> 00:14:25.660 in that the words you use, you use meaning 372 00:14:25.660 --> 00:14:27.340 one thing but another person may hear them 373 00:14:27.340 --> 00:14:29.140 and hear something entirely different because 374 00:14:29.140 --> 00:14:30.940 that same word can mean a different thing to 375 00:14:30.940 --> 00:14:33.480 someone else. So one other place I've heard 376 00:14:33.480 --> 00:14:36.240 the term gravity wave is actually in 377 00:14:36.640 --> 00:14:39.360 atmospheres and um, to do with fluid 378 00:14:39.360 --> 00:14:41.760 movement. And so you see 379 00:14:42.400 --> 00:14:45.280 things like um, I think lens clouds, delta 380 00:14:45.280 --> 00:14:48.040 cumulus lenticularis and um, wave 381 00:14:48.040 --> 00:14:50.640 clouds are associated with something that 382 00:14:50.640 --> 00:14:52.880 atmospheric scientists describe as gravity 383 00:14:52.880 --> 00:14:55.000 waves, which are things that happen when 384 00:14:55.000 --> 00:14:57.520 you've got the interface between two fluids 385 00:14:58.240 --> 00:15:00.800 and you've got steady airflow over things. 386 00:15:00.800 --> 00:15:03.040 And if you actually do a quick Google, I just 387 00:15:03.120 --> 00:15:05.100 fired this up and found the Wikipedia page 388 00:15:05.100 --> 00:15:08.020 for gravity wave. There are some absolutely 389 00:15:08.020 --> 00:15:10.220 beautiful images of 390 00:15:11.180 --> 00:15:13.820 wind driven gravity waves in the Timor Sea. 391 00:15:13.820 --> 00:15:15.780 You've got some beautiful wave clouds over 392 00:15:15.780 --> 00:15:18.660 the us, Little bits of maths. But this ties 393 00:15:18.660 --> 00:15:21.660 into, I think, something I used to see when I 394 00:15:21.660 --> 00:15:23.700 was doing weather recordings as a teenager in 395 00:15:23.700 --> 00:15:26.140 Yorkshire at school, because of the shape of 396 00:15:26.140 --> 00:15:27.740 the Pennines and the kind of airflow we got, 397 00:15:27.740 --> 00:15:30.500 we got lens clouds relatively frequently. And 398 00:15:30.500 --> 00:15:32.540 I think they are linked to the phenomenon 399 00:15:32.540 --> 00:15:33.980 that atmospheric scientists would often 400 00:15:33.980 --> 00:15:36.980 describe as gravity waves. For clarity, 401 00:15:36.980 --> 00:15:39.420 then, I think we should call what we're 402 00:15:39.420 --> 00:15:42.420 talking about here gravitational waves. And 403 00:15:42.420 --> 00:15:45.260 I think that's probably more accurate. 404 00:15:45.260 --> 00:15:48.100 And I think possibly astronomers slipping 405 00:15:48.100 --> 00:15:50.300 into calling gravitational waves gravity 406 00:15:50.300 --> 00:15:52.900 waves could be the cause of confusion to 407 00:15:52.900 --> 00:15:54.140 people who are thinking about weather. 408 00:15:54.860 --> 00:15:57.660 Gravitational waves, Dean was 409 00:15:57.660 --> 00:16:00.660 right. Are, uh, perturbations in the 410 00:16:00.660 --> 00:16:02.940 structure of space rather than 411 00:16:03.860 --> 00:16:06.780 matter itself shifting. This 412 00:16:06.780 --> 00:16:08.820 makes my head hurt. I should stress that I'm 413 00:16:08.820 --> 00:16:11.140 very much not an expert here and I know I say 414 00:16:11.140 --> 00:16:13.340 that very, very often, but I'm. You know, 415 00:16:13.340 --> 00:16:16.140 it's important to note that I'm not speaking 416 00:16:16.140 --> 00:16:18.260 from a position of great authority here, 417 00:16:19.060 --> 00:16:22.020 but what you're getting are, uh, a 418 00:16:22.020 --> 00:16:24.140 phenomenon that was first predicted in the 419 00:16:24.140 --> 00:16:26.620 late 1800s and early 1900s. Apparently the 420 00:16:26.620 --> 00:16:29.060 predictions predated Einstein, but he kind of 421 00:16:29.460 --> 00:16:31.860 formalised it through general relativity 422 00:16:32.500 --> 00:16:35.320 in the form of extreme, extreme 423 00:16:35.320 --> 00:16:38.080 events causing perturbations to space time 424 00:16:38.080 --> 00:16:40.000 that ripple outwards at the speed of light, 425 00:16:40.560 --> 00:16:43.400 causing, effectively, waves in 426 00:16:43.400 --> 00:16:46.400 the spacetime continuum, effectively 427 00:16:46.720 --> 00:16:49.280 in space itself, in the same thing that is 428 00:16:49.440 --> 00:16:50.800 stretching with the expansion of the 429 00:16:50.800 --> 00:16:53.280 universe. Those waves, 430 00:16:53.680 --> 00:16:55.520 as they pass through, are almost 431 00:16:55.520 --> 00:16:57.400 imperceptible. They don't really interact 432 00:16:57.400 --> 00:16:59.920 much with anything. But because 433 00:17:00.080 --> 00:17:02.520 they perturb, um, space, they can have a 434 00:17:02.520 --> 00:17:04.480 measurable effect in that they can change the 435 00:17:04.480 --> 00:17:07.390 distance between two points as the wave 436 00:17:07.390 --> 00:17:09.470 passes through. Now, there's some little 437 00:17:09.470 --> 00:17:11.750 animations trying to illustrate how waves 438 00:17:11.750 --> 00:17:14.590 would look, um, on the Wikipedia 439 00:17:14.590 --> 00:17:16.310 article about gravitational waves that are 440 00:17:16.310 --> 00:17:18.030 not really helping me because they're looking 441 00:17:18.030 --> 00:17:20.190 at what would happen if you had a circle of 442 00:17:20.190 --> 00:17:21.910 points and a wave pass through. And there's 443 00:17:21.910 --> 00:17:24.550 two ways it can wibble and it can go like a 444 00:17:24.550 --> 00:17:27.350

cross, or it can go like a square, like a 445 00:17:27.350 --> 00:17:29.630 plus sign. Sorry, that doesn't particularly 446 00:17:29.630 --> 00:17:31.700 help me visualise it. But what's happening, 447 00:17:32.490 --> 00:17:34.890 to the best of my understanding, is that 448 00:17:35.290 --> 00:17:37.130 you have this tiny little 449 00:17:37.850 --> 00:17:40.810 shift in space as the wave passes through, 450 00:17:41.450 --> 00:17:44.210 which means that ligo, which has 451 00:17:44.210 --> 00:17:46.570 these two arms at right angle to each other 452 00:17:46.570 --> 00:17:49.250 that are like four kilometres long, has light 453 00:17:49.250 --> 00:17:52.210 bouncing along these two arms. And when 454 00:17:52.210 --> 00:17:54.090 the length of one of those arms, um, shifts 455 00:17:54.090 --> 00:17:57.090 very slightly, the light will change from 456 00:17:57.090 --> 00:17:59.210 being constructively to destructively 457 00:17:59.210 --> 00:18:01.940 interfering with each other. So a very small, 458 00:18:02.260 --> 00:18:04.420 very, very small shift in distance 459 00:18:05.540 --> 00:18:07.580 means that the light, when it goes along and 460 00:18:07.580 --> 00:18:09.420 bounces back, will have travelled a slightly 461 00:18:09.420 --> 00:18:11.420 different distance and Then when you 462 00:18:11.420 --> 00:18:13.100 recombine it with the light that goes down 463 00:18:13.100 --> 00:18:14.900 the other arm, there'll be a little bit more 464 00:18:14.900 --> 00:18:16.540 in phase, out of phase. So you'll see the 465 00:18:16.540 --> 00:18:18.580 intensity of the result changing. 466 00:18:19.380 --> 00:18:20.020 Andrew Dunkley: Gotcha. 467 00:18:20.020 --> 00:18:22.740 Jonti Horner: What's astonishing about this is the 468 00:18:22.740 --> 00:18:25.060 figure that um, one of these gravitational 469 00:18:25.060 --> 00:18:27.860 waves that they detect is changing the 470 00:18:27.860 --> 00:18:30.180 length of one of those four kilometre arms 471 00:18:31.010 --> 00:18:33.810 by a thousandth of the width of a proton 472 00:18:33.890 --> 00:18:35.730 of a subatomic particle. 473 00:18:36.050 --> 00:18:37.330 Andrew Dunkley: That is a quantum level. 474 00:18:37.490 --> 00:18:40.130 Jonti Horner: Yeah, it's utterly quantum level. It's 475 00:18:40.130 --> 00:18:42.330 astonishing. The analogy that's been 476 00:18:42.330 --> 00:18:44.130 published about that, to put it into scale, 477 00:18:44.130 --> 00:18:45.690 is if you think about the distance between 478 00:18:45.690 --> 00:18:48.490 the sun and Proxima Centauri, it's like 479 00:18:48.490 --> 00:18:50.130 changing that distance by the width of a 480 00:18:50.130 --> 00:18:52.530 human hair. It's 481 00:18:53.090 --> 00:18:55.530 utterly mind boggling that we can detect 482 00:18:55.530 --> 00:18:58.130 this. It's an astonishing achievement. Now, 483 00:18:58.130 --> 00:19:01.060 my understanding is limited 484 00:19:01.460 --> 00:19:03.620 and, you know, really want to stress that 485

00:19:04.100 --> 00:19:06.660 what would happen as I understand it though 486 00:19:06.660 --> 00:19:09.540 is that it isn't just a distance between the 487 00:19:09.540 --> 00:19:11.380 subatomic particles that are changing, but 488 00:19:11.380 --> 00:19:13.140 they themselves will change. We would change 489 00:19:13.140 --> 00:19:15.940 as that wave goes through us because space 490 00:19:16.020 --> 00:19:18.940 itself would change, would fly us, but we 491 00:19:18.940 --> 00:19:21.140 wouldn't notice it. You know, that kind of 492 00:19:21.140 --> 00:19:23.460 change is tiny compared to us. But my 493 00:19:23.460 --> 00:19:26.280 understanding, Dean, is very 494 00:19:26.280 --> 00:19:28.480 much that, uh, the particles would change and 495 00:19:28.480 --> 00:19:29.960 the distance between them would change and 496 00:19:29.960 --> 00:19:31.600 everything will be slightly compressed and 497 00:19:31.600 --> 00:19:34.280 slightly relaxed. But I stand to be 498 00:19:34.280 --> 00:19:35.960 corrected in that. Yeah, 499 00:19:36.920 --> 00:19:38.920 it's very difficult to visualise and 500 00:19:39.160 --> 00:19:40.120 challenging to understand. 501 00:19:40.920 --> 00:19:43.880 Andrew Dunkley: Yeah. Um, so the wave moves through space, 502 00:19:43.960 --> 00:19:46.400 it affects space, but the space doesn't 503 00:19:46.400 --> 00:19:48.800 actually move with the wave. It's just like a 504 00:19:48.800 --> 00:19:51.200 wave in the ocean. It doesn't like the wave. 505 00:19:51.200 --> 00:19:52.520 Isn't the water moving? 506 00:19:52.600 --> 00:19:55.040 Jonti Horner: The water still moves up and down kind of 507 00:19:55.040 --> 00:19:56.920 thing. I think the water actually goes in a 508 00:19:56.920 --> 00:19:58.700 certain way circle, doesn't it, in a wave? So 509 00:19:58.700 --> 00:20:00.460 its average position is the same, but it 510 00:20:00.460 --> 00:20:02.540 rolls back and forth and the energy is 511 00:20:02.540 --> 00:20:03.540 propagated through. 512 00:20:03.860 --> 00:20:05.700 Andrew Dunkley: Correct. That's the way I understand 513 00:20:06.660 --> 00:20:09.500 it seems logical that waves in space would be 514 00:20:09.500 --> 00:20:12.500 the same. Um, completely 515 00:20:12.500 --> 00:20:14.340 different setup, but same effect 516 00:20:15.140 --> 00:20:15.820 essentially. 517 00:20:15.820 --> 00:20:17.620 I imagine what I think will be 518 00:20:17.620 --> 00:20:19.020 Jonti Horner: interesting, and I mean this is going 519 00:20:19.020 --> 00:20:21.140 slightly off topic into philosophy, is 520 00:20:22.250 --> 00:20:24.300 uh, how these ideas will become easier to 521 00:20:24.300 --> 00:20:27.180 explain over time. So I think when 522 00:20:27.420 --> 00:20:30.220 I was at uni, people were teaching special 523 00:20:30.220 --> 00:20:32.500 and general relativity and quantum mechanics 524 00:20:32.500 --> 00:20:35.340 as m modern physics as being quite 525 00:20:35.340 --> 00:20:38.300 new. And the students were understanding them 526 00:20:38.300 --> 00:20:40.660 a bit more easily than the people who taught 527 00:20:40.660 --> 00:20:42.060 them understood them when they were students, 528 00:20:42.780 --> 00:20:45.580 because we were about 80 years 529 00:20:45.740 --> 00:20:48.100 on from these discoveries. So the people who 530 00:20:48.100 --> 00:20:50.860 were teaching us had been taught by people 531 00:20:50.860 --> 00:20:52.780 where these discoveries had been made during 532 00:20:52.780 --> 00:20:54.820 their lifetimes, potentially. Given that 533 00:20:54.820 --> 00:20:56.700 you're often taught by the old academics. 534 00:20:57.810 --> 00:21:00.210 And initially the understanding of quantum 535 00:21:00.210 --> 00:21:02.970 mechanics and relativity was way 536 00:21:02.970 --> 00:21:05.970 postdoc. And then PhD students learned it 537 00:21:05.970 --> 00:21:07.890 and then uni students learned it. And now I 538 00:21:07.890 --> 00:21:09.970 believe it's taught at high school. So as 539 00:21:09.970 --> 00:21:12.850 time goes on and people can 540 00:21:12.850 --> 00:21:14.920 explain things to the next generation, our, 541 00:21:14.920 --> 00:21:16.970 uh, kind of societal understanding of these 542 00:21:16.970 --> 00:21:19.250 concepts gets better and they get accepted. 543 00:21:19.810 --> 00:21:21.890 And you suddenly get to the point where 544 00:21:22.210 --> 00:21:23.970 primary school kids are talking about special 545 00:21:23.970 --> 00:21:25.370 relativity. I mean, they're probably not 546 00:21:25.370 --> 00:21:27.330 talking about it in the mathematical terms, 547 00:21:27.730 --> 00:21:29.790 but some of the concep are now really 548 00:21:29.790 --> 00:21:32.110 embedded in culture. And I think part of the 549 00:21:32.110 --> 00:21:35.070 problem I have with gravitational 550 00:21:35.070 --> 00:21:37.710 waves is that whilst they had been 551 00:21:37.710 --> 00:21:39.830 predicted in a kind of niche way so long ago, 552 00:21:39.830 --> 00:21:42.750 the first observations were so recent that 553 00:21:42.750 --> 00:21:44.630 I wasn't taught about gravitational waves at 554 00:21:44.630 --> 00:21:47.350 uni. They weren't part of our courses. It's 555 00:21:47.350 --> 00:21:50.350 still really cutting edge new concepts. 556 00:21:51.150 --> 00:21:53.990 And so my understanding, therefore 557 00:21:53.990 --> 00:21:56.720 my explanation, it's woolly because I've 558 00:21:56.720 --> 00:21:59.320 never had it explained by someone who has had 559 00:21:59.320 --> 00:22:01.360 it explained by someone who's had it 560 00:22:01.360 --> 00:22:03.160 explained by someone. We've not had that 561 00:22:03.160 --> 00:22:05.600 buildup of conceptual 562 00:22:05.600 --> 00:22:08.160 description, I guess, to really embed this. 563 00:22:08.160 --> 00:22:10.000 And I find it really hard to get my head 564 00:22:10.000 --> 00:22:13.000 around the first observed gravitational wave, 565 00:22:13.000 --> 00:22:15.600 I think was 2015. This is

a 566 00:22:15.600 --> 00:22:18.160 decade old. So it's probably like someone 567 00:22:18.160 --> 00:22:20.880 calling into the podcast in 1925 568 00:22:20.880 --> 00:22:22.750 asking me to explain general relativity. 569 00:22:24.260 --> 00:22:27.030 Andrew Dunkley: Yes. Yeah, that's a good analogy. Um, 570 00:22:27.220 --> 00:22:29.500 Dean, thanks for the question. Hope we, we 571 00:22:29.500 --> 00:22:30.940 covered all those little gaps you were 572 00:22:30.940 --> 00:22:33.100 talking about. Boom, boom. Uh, this is Space 573 00:22:33.100 --> 00:22:35.980 Nuts with Andrew Dunkley and Professor Johnty 574 00:22:35.980 --> 00:22:37.700 Horner. A, uh, Q A edition. 575 00:22:39.780 --> 00:22:41.780 Generic: I think we need to do a little more all 576 00:22:41.780 --> 00:22:42.740 weather testing. 577 00:22:43.380 --> 00:22:45.140 Andrew Dunkley: Amen, Space Nuts. 578 00:22:45.460 --> 00:22:48.020 Our next question comes 579 00:22:48.260 --> 00:22:49.810 from David. 580 00:22:49.810 --> 00:22:52.690 Andrew Dunkley: This is David from Port Washington, New York. 581 00:22:53.410 --> 00:22:55.170 And I was thinking back to when I was a 582 00:22:55.170 --> 00:22:57.970 teenager and I heard the recording of 583 00:22:57.970 --> 00:23:00.770 the resonant frequency of the universe and I 584 00:23:00.770 --> 00:23:02.810 thought it was very cool. I'm wondering if 585 00:23:02.810 --> 00:23:05.810 there was some kind of medium that sound 586 00:23:05.810 --> 00:23:08.430 could pass through in space, like, uh, 587 00:23:08.690 --> 00:23:11.250 water, uh, or even air. 588 00:23:11.570 --> 00:23:14.250 What would I be hearing? Uh, and would it be 589 00:23:14.250 --> 00:23:17.240 beautiful or would it be terrifying? What are 590 00:23:17.240 --> 00:23:19.640 the different resonant frequencies going on 591 00:23:19.640 --> 00:23:20.840 and big explosions? 592 00:23:21.640 --> 00:23:21.650 Generic: Really? 593 00:23:21.650 --> 00:23:22.920 Andrew Dunkley: Um, interested to know. 594 00:23:23.480 --> 00:23:23.550 Generic: Bonus. 595 00:23:23.550 --> 00:23:25.720 Andrew Dunkley: Um, question. If I could breathe in space, 596 00:23:25.800 --> 00:23:27.760 what would it smell like? But I'm more 597 00:23:27.760 --> 00:23:30.200 interested to know about the sounds. Okay, 598 00:23:30.200 --> 00:23:30.920 thanks guys. 599 00:23:31.720 --> 00:23:34.080 Andrew Dunkley: Thank you. David. I love this question. It's 600 00:23:34.080 --> 00:23:36.110 a little bit different. We haven't had uh, 601 00:23:36.200 --> 00:23:38.280 one like that for a while. Although I do 602 00:23:38.280 --> 00:23:41.080 recall we did talk about 603 00:23:41.160 --> 00:23:43.920 some time back about, um, I 604 00:23:43.920 --> 00:23:46.560 can't remember exactly what the object was, 605 00:23:46.560 --> 00:23:48.380 but they were talking about what it would 606 00:23:48.380 --> 00:23:50.500 smell like if you could smell it. And 607 00:23:50.950 --> 00:23:53.900 um, you know, and that was

fascinating 608 00:23:53.900 --> 00:23:55.740 in itself. But don't ask me to remember what 609 00:23:55.740 --> 00:23:58.260 it was. I think it was rotten eggs. 610 00:23:58.260 --> 00:23:58.700 Andrew Dunkley: It is. 611 00:23:58.700 --> 00:24:00.660 Jonti Horner: I think that's a concept that's often used a 612 00:24:00.660 --> 00:24:01.900 bit like we talked about in the Last 613 00:24:01.900 --> 00:24:04.500 Questions episode about the raining diamonds 614 00:24:04.500 --> 00:24:06.820 and raining, um, precious gems, 615 00:24:07.620 --> 00:24:10.540 where people try to give you a 616 00:24:10.540 --> 00:24:12.460 hook that fits in with your day to day lived 617 00:24:12.460 --> 00:24:14.260 experience to help you visualise something 618 00:24:14.260 --> 00:24:16.260 more clearly. And the 619 00:24:16.900 --> 00:24:19.500 recording of the resonant frequency of the 620 00:24:19.500 --> 00:24:22.230 univers. It's another one of those. I think 621 00:24:22.230 --> 00:24:23.710 what we're talking about there is the 622 00:24:23.710 --> 00:24:25.510 microwave background, cosmic microwave 623 00:24:25.510 --> 00:24:28.430 background, which is this very low 624 00:24:28.430 --> 00:24:31.310 frequency now radio detection, um, 625 00:24:31.670 --> 00:24:34.670 equivalent to a black body at about 2.7 626 00:24:34.670 --> 00:24:37.350 Kelvin. That is a leftover hiss from 627 00:24:37.990 --> 00:24:40.790 the Big Bang, which, when Big bang happened 628 00:24:40.790 --> 00:24:43.150 about 300,000 years later, the universe went 629 00:24:43.150 --> 00:24:45.070 from being opaque to transparent. And all the 630 00:24:45.070 --> 00:24:47.150 radiation from the heat of the universe at 631 00:24:47.150 --> 00:24:49.990 that time went out into space. Universes 632 00:24:49.990 --> 00:24:52.530 got bigger, everything's got redshifted. So 633 00:24:52.530 --> 00:24:54.410 the peak of that spectrum now looks like a 634 00:24:54.410 --> 00:24:56.760 source. That was 2.7 Kelvin. And, 635 00:24:56.760 --> 00:24:59.250 um, that microwave 636 00:24:59.250 --> 00:25:01.610 background is the source of a lot of the 637 00:25:01.610 --> 00:25:03.730 static that you used to get if you tune your 638 00:25:03.730 --> 00:25:05.970 radio between stations or if you had an old 639 00:25:05.970 --> 00:25:07.850 TV where you had to tune in on the dial or 640 00:25:07.850 --> 00:25:09.930 move the antenna around and you just got the 641 00:25:09.930 --> 00:25:12.090 noise on the screen. A significant component 642 00:25:12.090 --> 00:25:14.450 of that was a macro background. And people 643 00:25:14.450 --> 00:25:17.210 have often tried to convert that into 644 00:25:17.210 --> 00:25:20.010 a sound to give people a kind of 645 00:25:20.010 --> 00:25:21.970 emotional connection, a way of visualising 646 00:25:21.970 --> 00:25:24.930 this. Um, although that's 647 00:25:24.930 --> 00:25:27.690 turning radio waves into a sound. Well, I 648 00:25:27.690 --> 00:25:29.930 guess we do that all the time with FM and AM 649 00:25:29.930 --> 00:25:31.050 broadcast, right? 650 00:25:31.290 --> 00:25:31.690 Andrew Dunkley: Yep. 651 00:25:31.690 --> 00:25:34.290 Jonti Horner: So, uh, it kind of makes sense to people in 652 00:25:34.290 --> 00:25:36.890 terms of what the universe would sound like. 653 00:25:36.890 --> 00:25:39.730 If there was a medium in space to transmit 654 00:25:39.730 --> 00:25:42.130 the sound, it would actually depend to some 655 00:25:42.130 --> 00:25:44.170 degree of the density of that medium as well. 656 00:25:44.170 --> 00:25:46.730 So the frequency that a given sound 657 00:25:46.890 --> 00:25:49.660 will sound like changes with 658 00:25:49.900 --> 00:25:52.660 atmospheric pressure. And I've seen examples 659 00:25:52.660 --> 00:25:54.860 of this where people have put an alarm bell, 660 00:25:55.500 --> 00:25:57.980 kind of alarm clock type, ringy bell noise 661 00:25:58.380 --> 00:26:01.300 in a big bell jar and evacuated the air 662 00:26:01.300 --> 00:26:02.700 from it. And as the air pressure got lower 663 00:26:02.700 --> 00:26:04.260 and lower, I think the pitch got higher and 664 00:26:04.260 --> 00:26:07.180 higher until the sound disappeared. So you've 665 00:26:07.180 --> 00:26:09.340 got a lot of different factors that would 666 00:26:09.340 --> 00:26:12.300 come into this to do with the composition 667 00:26:12.300 --> 00:26:14.500 of the medium, the density of the medium and 668 00:26:14.500 --> 00:26:17.250 stuff like that. But let's imagine just for a 669 00:26:17.250 --> 00:26:18.650 minute, because I think this is more of a 670 00:26:18.650 --> 00:26:21.090 science fiction question than a science fact 671 00:26:21.090 --> 00:26:22.970 one in a way. And I do love it as a question 672 00:26:22.970 --> 00:26:25.450 like that. If you were floating around in the 673 00:26:25.450 --> 00:26:27.610 solar system and you were uh, beyond the 674 00:26:27.610 --> 00:26:30.050 Earth's atmosphere, what would be the main 675 00:26:30.130 --> 00:26:32.450 source of noise that you'd experience? 676 00:26:33.010 --> 00:26:35.010 To me, I would actually guess the solar wind. 677 00:26:35.330 --> 00:26:37.330 Cause you have this flow of particles coming 678 00:26:37.330 --> 00:26:39.490 past you at a speed measured in hundreds of 679 00:26:39.490 --> 00:26:42.010 kilometres a second, 100, 200, 300 kilometres 680 00:26:42.010 --> 00:26:44.890 a second. So to me, I guess the main sound 681 00:26:44.890 --> 00:26:46.890 you would hear if you were beyond the Earth's 682 00:26:46.890 --> 00:26:49.170 atmosphere and there was enough medium for 683 00:26:49.170 --> 00:26:51.290 you to listen to, would actually be the sound 684 00:26:51.290 --> 00:26:53.290 of the wind blowing, but a really intense 685 00:26:53.850 --> 00:26:56.810 gale blowing. There have been 686 00:26:56.810 --> 00:26:59.210 discussions about what you'd hear on Mars. 687 00:26:59.210 --> 00:27:01.370 Now of course, on Mars the atmospheric 688

00:27:01.370 --> 00:27:03.410 pressure is much, much lower than even at the 689 00:27:03.410 --> 00:27:06.330 altitude of Everest. So that frequency 690 00:27:06.330 --> 00:27:08.210 shifting phenomenon would come in. So 691 00:27:08.210 --> 00:27:10.090 something that you'd hear as an ice deep bass 692 00:27:10.090 --> 00:27:12.570 note on Earth, I believe, would be a higher 693 00:27:12.570 --> 00:27:14.730 pitch on Mars quite markedly. 694 00:27:14.970 --> 00:27:15.370 Andrew Dunkley: Yeah. 695 00:27:15.370 --> 00:27:18.350 Jonti Horner: Darren Squeaky Y if you're listening 696 00:27:18.350 --> 00:27:20.310 to this podcast on Mars, please wear 697 00:27:20.310 --> 00:27:22.390 headphones. Otherwise I'll sound even more 698 00:27:22.390 --> 00:27:25.300 stupid than normal, I guess. Um, 699 00:27:25.910 --> 00:27:28.670 I would imagine that in terms 700 00:27:28.670 --> 00:27:30.510 of the concept of whether it would be 701 00:27:30.510 --> 00:27:33.030 beautiful or scary, I suspect it'd be like 702 00:27:33.030 --> 00:27:35.190 white noise with a lot of different 703 00:27:35.350 --> 00:27:38.350 components coming in. If you could visualise 704 00:27:38.350 --> 00:27:39.830 different astronomical phenomena 705 00:27:39.830 --> 00:27:42.550 contributing, a lot of them are time varying, 706 00:27:42.550 --> 00:27:45.120 a lot of them are bright flashes or 707 00:27:45.120 --> 00:27:47.200 whatever. So you'll probably have an 708 00:27:47.200 --> 00:27:49.800 underlying bass noise of whatever 709 00:27:49.880 --> 00:27:52.320 with lots of other things impinging on it. 710 00:27:52.320 --> 00:27:54.760 But it's really hard to say because we're 711 00:27:54.760 --> 00:27:56.370 trying to imagine a reality that is so, ah, 712 00:27:56.400 --> 00:27:59.040 different to our own. So I'm trying to find a 713 00:27:59.040 --> 00:28:01.000 way to contextualise that, I guess. 714 00:28:01.630 --> 00:28:04.280 Um, so it'd probably be a lot more like a 715 00:28:04.280 --> 00:28:07.160 white noise machine than something clear and 716 00:28:07.240 --> 00:28:09.640 beautiful. Possibly a white noise machine on 717 00:28:09.640 --> 00:28:10.330 a very windy day. 718 00:28:11.200 --> 00:28:13.870 Andrew Dunkley: Yeah. Sounds, um, in space, um, 719 00:28:16.000 --> 00:28:18.840 it's a difficult thing to try and get your 720 00:28:18.840 --> 00:28:21.800 head around because sound needs something to 721 00:28:21.800 --> 00:28:24.440 move through and space doesn't offer a lot of 722 00:28:24.440 --> 00:28:24.720 that. 723 00:28:25.360 --> 00:28:28.240 Jonti Horner: Absolutely. And I mean to maybe give you a 724 00:28:28.240 --> 00:28:29.640 different illustration of that. If you think 725 00:28:29.640 --> 00:28:31.160 about how sounds change when you go 726 00:28:31.160 --> 00:28:33.840 underwater, how different the world 727 00:28:33.840 --> 00:28:35.640 seems if you're snorkelling or you're doing a 728 00:28:35.640 --> 00:28:36.220 scuba Dive. 729 00:28:36.690 --> 00:28:36.930 Andrew Dunkley: Yeah. 730 00:28:36.930 --> 00:28:39.170 Jonti Horner: How all the sounds are so different to you. 731 00:28:39.650 --> 00:28:42.410 Andrew Dunkley: Yeah. I'll give you an example of sound 732 00:28:42.410 --> 00:28:45.370 and witnessing its movement. Uh, and this is 733 00:28:45.370 --> 00:28:48.090 not something I'd recommend, but, uh, we were 734 00:28:48.090 --> 00:28:50.770 standing on the rim of a volcano some years 735 00:28:50.770 --> 00:28:53.490 ago, and it was active and it was going 736 00:28:54.450 --> 00:28:56.690 in our faces. Actually, we had to leave 737 00:28:56.690 --> 00:28:59.480 because it was getting in our faces. Um, 738 00:28:59.650 --> 00:29:02.450 but watching the process of the eruption, 739 00:29:02.450 --> 00:29:04.730 you see it, it before 740 00:29:05.690 --> 00:29:08.410 you hear it, but you feel it 741 00:29:09.610 --> 00:29:12.010 also before you hear it, but not until after 742 00:29:12.010 --> 00:29:12.650 you see it. 743 00:29:12.650 --> 00:29:13.130 Andrew Dunkley: Yeah. 744 00:29:13.770 --> 00:29:16.130 Andrew Dunkley: So, uh, you see the explosion, you feel the 745 00:29:16.130 --> 00:29:19.050 rumble, and then you hear it, and 746 00:29:19.050 --> 00:29:22.050 then the shockwave hits you. Yeah, it's 747 00:29:22.050 --> 00:29:24.410 a really weird combination. And look, you're 748 00:29:24.410 --> 00:29:26.970 talking about a matter of 749 00:29:27.530 --> 00:29:29.650 all of this happening over in the course of 750 00:29:29.650 --> 00:29:31.210 about a second or a second, a half, 751 00:29:32.570 --> 00:29:35.430 depending on distance. But you see it, you 752 00:29:35.430 --> 00:29:37.510 feel it, you hear it, 753 00:29:38.230 --> 00:29:40.070 you feel it in the ground, and then you feel 754 00:29:40.070 --> 00:29:40.790 the shockwave. 755 00:29:40.790 --> 00:29:41.350 Andrew Dunkley: Yeah. 756 00:29:41.830 --> 00:29:44.310 Jonti Horner: And I mean, that fits in with how 757 00:29:45.110 --> 00:29:47.070 sound travels at different speeds. So what 758 00:29:47.070 --> 00:29:49.950 you feel under your feet is effectively waves 759 00:29:49.950 --> 00:29:52.910 that you'd probably hear as sound. But going 760 00:29:52.910 --> 00:29:54.630 through a solid medium, they travel faster. 761 00:29:54.870 --> 00:29:55.310 Andrew Dunkley: Exactly. 762 00:29:55.310 --> 00:29:57.110 Jonti Horner: Shockwaves are quicker. And I mean, that 763 00:29:57.190 --> 00:29:59.750 links in part to, uh, how we know so much 764 00:29:59.750 --> 00:30:01.190 about the interior of the Earth. Because 765 00:30:01.430 --> 00:30:04.110 shock waves from earthquakes travel at 766 00:30:04.110 --> 00:30:06.110 different speeds through different media. And 767 00:30:06.110 --> 00:30:08.210 you've got T waves and S waves 768 00:30:08.450 --> 00:30:10.210 propagating around the Earth. Ah, some going 769 00:30:10.210 --> 00:30:11.850 through the Earth's, uh, interior, being 770 00:30:11.850 --> 00:30:13.810 picked

up at seismographs around the world 771 00:30:14.370 --> 00:30:16.570 that very clever people can use to reverse 772 00:30:16.570 --> 00:30:18.210 engineer what the interior structure of the 773 00:30:18.210 --> 00:30:21.010 Earth's like by those differences in speed. 774 00:30:22.610 --> 00:30:25.090 Andrew Dunkley: Yeah, it was a strange experience. 775 00:30:25.250 --> 00:30:27.890 And that was the last thing I expected to 776 00:30:27.890 --> 00:30:30.530 witness. I was a bit more concerned about 777 00:30:30.610 --> 00:30:32.770 what was falling out of the sky at the time. 778 00:30:33.170 --> 00:30:35.770 I'll tell you, though, um, I took a great 779 00:30:35.770 --> 00:30:37.370 photo as we were walking off. 780 00:30:37.690 --> 00:30:39.570 Uh, when you're in tour groups, there's 781 00:30:39.570 --> 00:30:41.970 always a straggler. So we're all halfway off 782 00:30:41.970 --> 00:30:44.250 the mountain, but someone decided to stay 783 00:30:44.250 --> 00:30:47.210 behind. And that's when the biggest bang of 784 00:30:47.210 --> 00:30:50.210 the day happened. And it flung lava bombs up 785 00:30:50.210 --> 00:30:52.570 in the sky the size of soccer balls. 786 00:30:53.210 --> 00:30:55.930 And I had already put my camera in my 787 00:30:55.930 --> 00:30:57.850 pocket. I, uh, turned it off. I had enough 788 00:30:57.850 --> 00:31:00.250 time to pull the camera out, turn it on 789 00:31:01.010 --> 00:31:03.370 focus, and take a photo of this woman staring 790 00:31:03.370 --> 00:31:05.010 up at lava bombs coming down. 791 00:31:06.210 --> 00:31:09.050 It's a great photo. Um, and then it was, 792 00:31:09.050 --> 00:31:11.970 uh, only a few weeks after I got home that my 793 00:31:11.970 --> 00:31:14.610 friend, uh, sent me a video that he'd Taken 794 00:31:15.170 --> 00:31:17.650 of one of those, uh, little eruptions and 795 00:31:18.210 --> 00:31:20.610 I didn't see it, but there was a lava bomb 796 00:31:20.610 --> 00:31:23.570 landed 20 metres in front of me. I never even 797 00:31:23.570 --> 00:31:26.570 saw it. And, yeah, that kind 798 00:31:26.570 --> 00:31:27.990 of freaked me out after the fact. 799 00:31:29.580 --> 00:31:32.460 Yeah, like I said, not something I recommend, 800 00:31:32.460 --> 00:31:35.100 but, boy, what an adrenaline jolt. 801 00:31:36.060 --> 00:31:38.740 Yeah, but there's a few 802 00:31:38.740 --> 00:31:40.940 volcanoes we've visited over the years and, 803 00:31:41.240 --> 00:31:43.340 um, they've all blown up since we've been to 804 00:31:43.340 --> 00:31:45.700 them. So the one at Vanuatu stopped air 805 00:31:45.700 --> 00:31:48.700 traffic. Uh, we were at Matt Etna, 806 00:31:49.140 --> 00:31:50.980 uh, a couple of years ago. Well, look what 807 00:31:50.980 --> 00:31:53.520 it's doing at the moment. Kilauea. It's gone 808 00:31:53.670 --> 00:31:55.670 off, like, several times since we were there. 809 00:31:55.990 --> 00:31:58.190 In fact, the observation deck in the 810 00:31:58.190 --> 00:32:00.790 caldera, uh, where we 811 00:32:01.190 --> 00:32:03.590 looked at Kilauea, was 812 00:32:03.590 --> 00:32:06.430 obliterated about a month after we were 813 00:32:06.430 --> 00:32:06.710 there. 814 00:32:08.230 --> 00:32:10.510 Jonti Horner: So when are you taking a holiday to Naples or 815 00:32:10.510 --> 00:32:11.590 to Yelliston? 816 00:32:11.830 --> 00:32:14.230 Andrew Dunkley: Well, actually, we've been to Naples, so, 817 00:32:14.710 --> 00:32:17.530 um, it wasn't, um, 818 00:32:17.530 --> 00:32:19.950 Vesuvius, though, that went off when we were 819 00:32:19.950 --> 00:32:21.710 there. It was, um, Stromboli. 820 00:32:21.710 --> 00:32:23.710 Jonti Horner: Yeah, well, they're quite worried about Campo 821 00:32:23.710 --> 00:32:26.050 Fiegri, I think it's called, which is Big 822 00:32:26.210 --> 00:32:29.210 Field under Naples. That, yes, will 823 00:32:29.210 --> 00:32:30.610 be a disaster when it goes. 824 00:32:31.010 --> 00:32:33.770 Andrew Dunkley: Well, like, if you go out 825 00:32:33.770 --> 00:32:36.370 into the. Into the bay and, and 826 00:32:36.530 --> 00:32:39.370 do a bit of, um, skin diving down to the. To 827 00:32:39.370 --> 00:32:41.689 the bottom, there's all this gas coming up 828 00:32:41.689 --> 00:32:42.770 through the sand, like. 829 00:32:43.170 --> 00:32:45.730 Jonti Horner: And I keep seeing reports of the amount of 830 00:32:45.730 --> 00:32:47.290 swelling of the lava dome and things like 831 00:32:47.290 --> 00:32:49.130 this. I mean, yeah, I personally would not 832 00:32:49.130 --> 00:32:51.570 feel all that comfortable living in that area 833 00:32:51.570 --> 00:32:52.660 or even necessarily visiting, 834 00:32:55.130 --> 00:32:57.370 but hopefully, you know, it will not be a 835 00:32:57.370 --> 00:32:59.810 problem within our lifetimes and the science 836 00:32:59.810 --> 00:33:01.570 will continue to improve to the level that 837 00:33:01.570 --> 00:33:03.170 they get enough warning to get everybody out 838 00:33:03.170 --> 00:33:03.930 when it goes. 839 00:33:04.330 --> 00:33:06.650 Andrew Dunkley: Yeah, that's the problem, isn't it? Uh, and 840 00:33:06.650 --> 00:33:09.610 even in, uh, New Zealand they've got, um, the 841 00:33:10.010 --> 00:33:12.690 dormant, uh, volcano in the 842 00:33:12.690 --> 00:33:15.050 harbour at Auckland. And 843 00:33:16.170 --> 00:33:18.730 I was talking to a journalist friend of mine 844 00:33:18.810 --> 00:33:21.370 who lived in New Zealand, uh, some years ago 845 00:33:21.370 --> 00:33:23.530 when I worked for the abc, and he was saying, 846 00:33:23.850 --> 00:33:26.390 look, it is a worry there too, if this thing 847 00:33:26.390 --> 00:33:28.750 ever wakes up. There are only two roads out 848 00:33:28.750 --> 00:33:31.270 of Wellington, uh, out of Auckland, 849 00:33:31.990 --> 00:33:34.350 and you've got a million people there or 850 00:33:34.350 --> 00:33:37.150 something. And how are they going to get 851 00:33:37.150 --> 00:33:37.430 out? 852 00:33:37.430 -->

00:33:39.310 Jonti Horner: It was actually fascinating. I was in New 853 00:33:39.310 --> 00:33:41.030 Zealand a couple of times earlier in the year 854 00:33:41.190 --> 00:33:43.430 and went through Auckland and spotted all 855 00:33:43.430 --> 00:33:44.710 these little humps and thought, that's 856 00:33:44.710 --> 00:33:46.710 interesting. Looked into it. I just pulled up 857 00:33:46.710 --> 00:33:49.710 the information here. The metropolitan area 858 00:33:49.710 --> 00:33:51.960 of Auckland contains 53 859 00:33:51.960 --> 00:33:54.680 volcanoes because it's a little volcanic 860 00:33:54.680 --> 00:33:56.920 field of these small little 861 00:33:57.320 --> 00:33:59.640 maas and tuff rings and all this stuff. 862 00:34:01.160 --> 00:34:03.520 Um, none of them are thought to have erupted 863 00:34:03.520 --> 00:34:05.800 more than once, except for one of them called 864 00:34:06.040 --> 00:34:09.040 Orangitoto. But it is 865 00:34:09.040 --> 00:34:10.960 an active volcanic area. Apparently the first 866 00:34:10.960 --> 00:34:13.920 vent in that area erupted 193,000 867 00:34:13.920 --> 00:34:15.760 years ago. And the most recent one was about 868 00:34:15.760 --> 00:34:16.730 600 years ago. 869 00:34:16.879 --> 00:34:17.119 Generic: Go. 870 00:34:17.359 --> 00:34:17.839 Andrew Dunkley: Yeah. 871 00:34:18.000 --> 00:34:19.599 Jonti Horner: Um, and that's from the one in the water, 872 00:34:20.460 --> 00:34:23.399 um, just east of the city. But, 873 00:34:23.399 --> 00:34:25.439 yeah, must be a fascinating place to live. 874 00:34:25.999 --> 00:34:28.879 But that plus the earthquakes, 875 00:34:29.039 --> 00:34:31.919 plus the psalms that get there. It's 876 00:34:31.919 --> 00:34:33.959 good to live in interesting times. But that 877 00:34:33.959 --> 00:34:35.359 might be a little bit too full on. 878 00:34:35.759 --> 00:34:38.239 Andrew Dunkley: Yeah. Well, we visited Christchurch, 879 00:34:38.310 --> 00:34:41.159 uh, coming up on four 880 00:34:41.159 --> 00:34:43.959 years ago now, and, uh, it had had that 881 00:34:43.959 --> 00:34:46.230 massive earthquake, that tragic earthquake. 882 00:34:46.230 --> 00:34:49.190 And, uh, even then you could. That 883 00:34:49.190 --> 00:34:51.590 they hadn't come close to rebuilding. 884 00:34:52.230 --> 00:34:55.030 And they even have, um, a 885 00:34:55.030 --> 00:34:57.750 museum, Quake City, I think it's called In 886 00:34:58.070 --> 00:35:00.310 Christchurch, which I highly recommend. It's 887 00:35:00.470 --> 00:35:01.670 fascinating. Yeah. 888 00:35:02.270 --> 00:35:04.030 Uh, we got off the topic, uh, did we talk 889 00:35:04.030 --> 00:35:06.030 about smells in space? If you could take a 890 00:35:06.030 --> 00:35:08.950 big inhale, what would it be like? 891 00:35:08.950 --> 00:35:09.550 Andrew Dunkley: I'm not sure. 892 00:35:09.550 --> 00:35:11.350 Jonti Horner: I mean, this is one of those things that 893 00:35:11.350 --> 00:35:14.260 people use to give you a handle 894 00:35:14.420 --> 00:35:17.220 to get on. So when we discover interesting 895 00:35:17.220 --> 00:35:19.540 things in the atmosphere of different places, 896 00:35:20.820 --> 00:35:23.140 usually, um, the things that relate to 897 00:35:23.460 --> 00:35:25.500 gases that we'd have on Earth are used to 898 00:35:25.500 --> 00:35:27.300 say, oh, this place would smell of whatever. 899 00:35:27.700 --> 00:35:29.980 Most common of them is hydrogen sulphide, 900 00:35:29.980 --> 00:35:32.780 which is your rotten egg smell, which is why 901 00:35:32.780 --> 00:35:34.940 people talk so much about exoplanets that 902 00:35:34.940 --> 00:35:37.420 smell like rotten eggs. But I think there was 903 00:35:37.420 --> 00:35:40.060 one recently that wasn't there. Something 904 00:35:40.060 --> 00:35:41.660 saying it was a giant gas cloud that would 905 00:35:41.660 --> 00:35:44.310 have smelled or tasted of strawberries. Big 906 00:35:44.310 --> 00:35:47.030 Said found a long chain hydrocarbon that was 907 00:35:47.030 --> 00:35:49.750 part of the test sensation. That is a nice, 908 00:35:49.830 --> 00:35:52.510 nice strawberry. So I think most of space 909 00:35:52.510 --> 00:35:55.150 would not smell particularly pleasant, but 910 00:35:55.150 --> 00:35:57.470 you wouldn't smell very much. But there's 911 00:35:57.470 --> 00:35:58.990 dust and debris around. But there's also a 912 00:35:58.990 --> 00:36:00.910 lot of gases that you really wouldn't want to 913 00:36:00.910 --> 00:36:02.950 inhale. I mean, I'm thinking of hydrogen 914 00:36:02.950 --> 00:36:05.530 cyanide and things like this. So, uh, 915 00:36:05.550 --> 00:36:06.950 inhale at your own risk. 916 00:36:07.270 --> 00:36:09.350 Andrew Dunkley: Well, I think you'd only inhale once in space 917 00:36:09.350 --> 00:36:10.470 and that'd be the end of that. 918 00:36:10.470 --> 00:36:11.500 Jonti Horner: Oh, absolutely, absolutely. 919 00:36:11.660 --> 00:36:13.230 Generic: Probably. All right. 920 00:36:13.230 --> 00:36:14.900 Andrew Dunkley: Uh, David, thanks for that. Great question. 921 00:36:14.900 --> 00:36:16.860 That was a lot of fun to discuss and brought 922 00:36:16.860 --> 00:36:18.700 up a lot of things in my mind about some of 923 00:36:18.700 --> 00:36:21.340 the experiences with sounds and smells I've 924 00:36:21.340 --> 00:36:22.060 had in my life. 925 00:36:22.650 --> 00:36:24.820 Uh, and that brings us to the end of a Q and 926 00:36:24.820 --> 00:36:26.500 A edition. If you would like to send us some 927 00:36:26.500 --> 00:36:28.620 questions, please do through our website 928 00:36:28.620 --> 00:36:31.260 spacenutspodcast.com spacenuts 929 00:36:31.340 --> 00:36:33.740 IO or do a search for SpaceNuts 930 00:36:33.740 --> 00:36:36.220 podcast in your favourite search engine. If 931 00:36:36.220 --> 00:36:37.980 you just do a search for Space Nuts, it'll 932 00:36:37.980 --> 00:36:39.420 take you to that horrible movie. 933 00:36:40.970 --> 00:36:42.950 Um, well, it's probably not that horrible, 934 00:36:43.110 --> 00:36:45.390 but anyway, uh, that's how you do it. Just 935 00:36:45.390 --> 00:36:47.910 click on the AMA tab and send us text or 936 00:36:47.910 --> 00:36:49.630 audio questions. And don't forget to tell us 937 00:36:49.630 --> 00:36:51.350 who you are and where you're from. And have a 938 00:36:51.350 --> 00:36:52.630 look around on our website while you're 939 00:36:52.630 --> 00:36:54.750 there. Jonty, thanks very much. Good to see 940 00:36:54.750 --> 00:36:55.110 you again. 941 00:36:55.110 --> 00:36:56.590 Jonti Horner: That's absolute pleasure. It's good to catch 942 00:36:56.590 --> 00:36:58.510 up and, you know, I'll catch you again the 943 00:36:58.510 --> 00:36:59.910 next time Fred Watson's on a jolt. 944 00:36:59.910 --> 00:37:01.470 Andrew Dunkley: Yeah, I think you'll be back after this 945 00:37:01.470 --> 00:37:03.550 episode, but we'll, um, we'll keep you on 946 00:37:03.550 --> 00:37:05.990 standby, but we'll talk again down the track. 947 00:37:06.150 --> 00:37:06.710 Jonti Horner: Absolutely. 948 00:37:06.710 --> 00:37:09.350 Andrew Dunkley: Look forward to it, Professor Jonty Horner, 949 00:37:09.350 --> 00:37:10.910 professor of Astrophysics at the University 950 00:37:10.990 --> 00:37:12.910 of Southern Queensland. And thanks to Huw in 951 00:37:12.910 --> 00:37:15.070 the studio, uh, who did actually turn up 952 00:37:15.070 --> 00:37:16.590 today, but they wouldn't let him in because 953 00:37:16.590 --> 00:37:19.230 he smells. And from me, Andrew Dunkley. 954 00:37:19.230 --> 00:37:20.910 Thanks for your company. We'll see you on the 955 00:37:20.910 --> 00:37:23.150 next episode of Space Nuts. Bye. Bye. 956 00:37:24.350 --> 00:37:26.630 You've been listening to the Space Nuts 957 00:37:26.630 --> 00:37:29.590 Jonti Horner: podcast, available at 958 00:37:29.590 --> 00:37:31.630 Apple Podcasts, Spotify, 959 00:37:31.790 --> 00:37:34.480 iHeartRadio or your favourite podcast 960 00:37:34.480 --> 00:37:36.200 player. You can also stream on 961 00:37:36.200 --> 00:37:37.880 demand@bytes.com. 962 00:37:38.200 --> 00:37:40.280 Andrew Dunkley: this has been another quality podcast 963 00:37:40.280 --> 00:37:42.440 production from bytes.um com.