Key topics include:
- How photographic images are generated from radio telescopes, despite only receiving radio waves, and the fundamental principles behind this technology.
- A deep dive into gravitational waves, their impact on space, and how LIGO detects these minute disturbances in the fabric of spacetime.
- An imaginative discussion on what sounds might exist in space and the potential smells one could encounter beyond Earth’s atmosphere, including the curious idea of cosmic fragrances.
Join Andrew and Jonty as they demystify these concepts, providing clarity and insights into the wonders of astronomy and space science.
00:00 - Space Nuts aims to answer questions from the audience about astronomy and space science
01:37 - Were the pyramids built by aliens or were they built by humans
04:26 - How is a photographic image produced from a radio telescope and not an optical telescope
12:36 - Dean: I often hear about gravity waves and I have a hard time visualising
20:15 - Andrew Dunkley: I think ideas become easier to explain over time
22:45 - Our next question comes from David from Port Washington, New York
30:37 - Several volcanoes have blown up since we've been to them
32:08 - The metropolitan area of Auckland contains 53 volcanoes
35:02 - If you could take a big inhale, what would space smell like
36:22 - If you would like to send us some questions, please do through our website
Become a supporter of this podcast: https://www.spreaker.com/podcast/space-nuts-astronomy-insights-cosmic-discoveries--2631155/support.
00:00:00 --> 00:00:02 Andrew Dunkley: Hello again. Thanks for joining us on a Q and
00:00:02 --> 00:00:05 A edition of Space Nuts, where we talk
00:00:05 --> 00:00:07 astronomy and space science and we
00:00:07 --> 00:00:10 endeavour to answer, uh, questions from
00:00:10 --> 00:00:12 our audience. We've got a few good questions
00:00:12 --> 00:00:15 today, unlike all the bad ones we had
00:00:15 --> 00:00:17 previously. Uh, we're going to talk about
00:00:17 --> 00:00:20 radio telescope imagery. What does that
00:00:20 --> 00:00:22 mean? How does it work? I don't understand.
00:00:23 --> 00:00:26 And that's just me. Um, we also
00:00:26 --> 00:00:28 are going to be talking gravity waves. Now,
00:00:28 --> 00:00:30 I'm not sure if it's gravity or
00:00:30 --> 00:00:32 gravitational. They are different things. Uh,
00:00:33 --> 00:00:35 and also, uh, sounds and smells in space.
00:00:36 --> 00:00:39 What would they be like if you could stick
00:00:39 --> 00:00:41 your schnoz beyond our atmosphere? We'll talk
00:00:41 --> 00:00:44 about all of that on this edition of space
00:00:44 --> 00:00:44 nuts.
00:00:44 --> 00:00:47 Generic: 15 seconds. Guidance is internal.
00:00:47 --> 00:00:50 10, 9. Uh, ignition
00:00:50 --> 00:00:51 sequence start.
00:00:51 --> 00:00:52 Jonti Horner: Space nuts.
00:00:52 --> 00:00:54 Generic: 5, 4, 3, 2, 1. 2, 3,
00:00:54 --> 00:00:57 4, 5, 4, 3, 2', 1.
00:00:57 --> 00:00:58 Jonti Horner: Space nuts.
00:00:58 --> 00:01:00 Generic: Astronauts report it feels good.
00:01:01 --> 00:01:03 Andrew Dunkley: He's back again. He is Professor Jonty
00:01:03 --> 00:01:05 Horner, professor of Astrophysics at the
00:01:05 --> 00:01:07 University of Southern Queensland. Hi, Jonty.
00:01:07 --> 00:01:09 Jonti Horner: Good afternoon. How are you going? I am well.
00:01:09 --> 00:01:10 Andrew Dunkley: Good to see you again.
00:01:11 --> 00:01:12 Jonti Horner: It's good to be back. I think I'm going to be
00:01:12 --> 00:01:15 doing a lot of. I'm not sure, but today I
00:01:15 --> 00:01:16 think we've got questions that are a little
00:01:16 --> 00:01:19 out of my area of expertise. Um, I'd always
00:01:20 --> 00:01:22 like to flag up at the start when things are
00:01:22 --> 00:01:25 less my field because we don't all know
00:01:25 --> 00:01:27 everything. And it's good to, rather than
00:01:27 --> 00:01:30 pretend, good to be open about what I do and
00:01:30 --> 00:01:30 don't know.
00:01:31 --> 00:01:32 Andrew Dunkley: Fair enough.
00:01:32 --> 00:01:35 Andrew Dunkley: But, uh, we'll do our very best. I
00:01:35 --> 00:01:36 got the easy part. I just get to ask the
00:01:36 --> 00:01:37 questions.
00:01:37 --> 00:01:39 Let's, uh, get straight to our first one.
00:01:40 --> 00:01:43 And this one, uh, asks how is
00:01:43 --> 00:01:45 a photographic image produced from a radio
00:01:45 --> 00:01:48 telescope when all they are receiving is
00:01:48 --> 00:01:51 radio waves and not an optical image through
00:01:51 --> 00:01:54 a telescope lens? Uh, that's, uh,
00:01:54 --> 00:01:56 from Thomas in Canberra. He's thrown in a
00:01:56 --> 00:01:59 supplementary Monty Python, Monty Python
00:01:59 --> 00:02:02 style question. Were the pyramids built
00:02:02 --> 00:02:05 by aliens? Does that sound
00:02:05 --> 00:02:06 fair enough?
00:02:06 --> 00:02:06 Andrew Dunkley: Uh,
00:02:09 --> 00:02:11 Andrew Dunkley: horrible, dad joke.
00:02:11 --> 00:02:11 Andrew Dunkley: Horrible.
00:02:13 --> 00:02:14 Jonti Horner: But if you want to keep your
00:02:14 --> 00:02:16 Andrew Dunkley: razor sharp, I did see an article only
00:02:17 --> 00:02:20 a few days ago about, uh, a new theory into
00:02:20 --> 00:02:22 the building of the pyramids. But we went to
00:02:22 --> 00:02:25 Egypt a few years ago and they are, uh, quite
00:02:25 --> 00:02:28 adamant that, um, not only were they built
00:02:28 --> 00:02:30 by humans, they were built by
00:02:31 --> 00:02:33 what you would call contractors. They were
00:02:33 --> 00:02:35 not slaves. The people that built the
00:02:35 --> 00:02:38 pyramids, according to the locals, were
00:02:38 --> 00:02:40 actually employed.
00:02:40 --> 00:02:43 Jonti Horner: Yeah, lots of discussion of that. My partner
00:02:43 --> 00:02:46 Ness, is an avid history buff and
00:02:46 --> 00:02:48 also Likes to watch a bit of TV when she's
00:02:48 --> 00:02:50 trying to relax, to go to sleep. So I'm m
00:02:50 --> 00:02:52 constantly seeing archaeological
00:02:52 --> 00:02:53 documentaries and things like that. And she
00:02:53 --> 00:02:56 loves the Egyptians. So I've seen lots and
00:02:56 --> 00:02:58 lots of documentaries talking about this. And
00:02:58 --> 00:03:00 it turns out, if what I've seen in these
00:03:00 --> 00:03:02 shows can be believed, that it was actually
00:03:02 --> 00:03:04 fairly prestigious and fairly good working
00:03:04 --> 00:03:07 conditions to be one of the contractors
00:03:07 --> 00:03:08 working on the pyramids kind of building
00:03:08 --> 00:03:09 that. So.
00:03:09 --> 00:03:11 Andrew Dunkley: Yeah, I heard that too. Yes, exactly.
00:03:11 --> 00:03:13 Jonti Horner: Crack the big whips and all the rest of it.
00:03:13 --> 00:03:16 Andrew Dunkley: But yeah, yeah, no, it's fascinating
00:03:16 --> 00:03:18 history. Wouldn't you love a time machine
00:03:18 --> 00:03:20 just to go back and go, ah, uh, look.
00:03:20 --> 00:03:20 Andrew Dunkley: Yeah,
00:03:22 --> 00:03:25 Andrew Dunkley: now that we're seeing it, it looks easy.
00:03:25 --> 00:03:27 Jonti Horner: Uh, absolutely. I mean, I probably end up
00:03:27 --> 00:03:29 being really kind of busman's holiday though,
00:03:29 --> 00:03:31 with the time machine and going back to
00:03:31 --> 00:03:33 different astronomical events and think like,
00:03:33 --> 00:03:35 trying figure out if Caesar's Comet was
00:03:35 --> 00:03:38 actually real, you know, and, you know,
00:03:38 --> 00:03:40 trying to see if there were multiple sun
00:03:40 --> 00:03:42 grazing comets visible with the naked eye in
00:03:42 --> 00:03:45 daylight in I think it was 363 A.D. so
00:03:45 --> 00:03:47 I'd probably end up picking myself an
00:03:47 --> 00:03:50 astronomical holiday tour, um,
00:03:51 --> 00:03:52 not getting distracted by all the kind of
00:03:52 --> 00:03:54 human history stuff.
00:03:54 --> 00:03:56 Andrew Dunkley: Yeah, fair enough. I mean, you go nuts
00:03:56 --> 00:03:58 thinking about things to go back and see.
00:03:58 --> 00:03:59 Absolutely.
00:03:59 --> 00:04:01 Jonti Horner: Or going forward. I've said a few times that
00:04:01 --> 00:04:03 given the predictions we talked about last
00:04:03 --> 00:04:06 year, that Comet Duchesso, Comic
00:04:06 --> 00:04:08 Linkenberg, will return in the year 2097.
00:04:09 --> 00:04:11 That could well be the best comet of this
00:04:11 --> 00:04:13 century. I'd quite like to see it, but
00:04:14 --> 00:04:17 unless I am fortunate enough to reach 119
00:04:17 --> 00:04:20 years old, I think it unlikely. So,
00:04:20 --> 00:04:21 you know, time machine would be welcome.
00:04:22 --> 00:04:25 Andrew Dunkley: Yeah, it would. I'm working on it.
00:04:26 --> 00:04:28 Uh, so let's go to the first part of the
00:04:28 --> 00:04:31 question. Uh, how is a photographic image
00:04:31 --> 00:04:33 produced from a radio telescope when
00:04:33 --> 00:04:35 all they receive is radio waves and not an
00:04:35 --> 00:04:38 optical image through a telescope lens? Yeah,
00:04:38 --> 00:04:41 I've got to admit, this one confuses me a
00:04:41 --> 00:04:41 bit.
00:04:42 --> 00:04:44 Jonti Horner: We could say the same for infrared. We could
00:04:44 --> 00:04:47 say the same for gamma rays or X rays or for
00:04:47 --> 00:04:49 optical photographs. Right. So all of those
00:04:49 --> 00:04:51 different forms of radiation I just mentioned
00:04:51 --> 00:04:53 are different, uh, parts of the
00:04:53 --> 00:04:54 electromagnetic spectrum. So they're
00:04:54 --> 00:04:56 fundamentally the same thing but with
00:04:56 --> 00:04:58 different wavelengths in just the same way
00:04:58 --> 00:05:00 that red light and blue light are
00:05:00 --> 00:05:02 electromagnetic waves, but blue has a shorter
00:05:02 --> 00:05:04 wavelength and red has a longer wavelength.
00:05:05 --> 00:05:07 And um, I've got an astro photo behind me of
00:05:07 --> 00:05:10 the Helix Nebula. If I had a camera that was
00:05:10 --> 00:05:12 more sensitive to infrared, I would have
00:05:12 --> 00:05:13 picked out some slightly different features
00:05:13 --> 00:05:16 there because there is radiation coming in of
00:05:16 --> 00:05:19 different wavelengths. The way it
00:05:19 --> 00:05:21 works with a radio telescope or the way that
00:05:21 --> 00:05:24 it works with an M infrared detector or
00:05:24 --> 00:05:26 whatever is, you've got a detector
00:05:26 --> 00:05:29 that can detect radiation of that
00:05:29 --> 00:05:32 wavelength. Um, with an optical photo,
00:05:33 --> 00:05:35 you have a DSLR camera or a CCD camera that
00:05:35 --> 00:05:38 is sensitive to optical light and
00:05:38 --> 00:05:41 you get photons hitting the detector and
00:05:41 --> 00:05:43 creating electrons that are countered in the
00:05:43 --> 00:05:45 same way. For a radio telescope, you have a
00:05:45 --> 00:05:47 detector that is sensitive to radio waves
00:05:48 --> 00:05:50 and when photons of the right energy hit the
00:05:50 --> 00:05:52 detector, they create electrons and they get
00:05:52 --> 00:05:55 countered. So what happens is you've got your
00:05:55 --> 00:05:58 radio telescope that can look at a patch of
00:05:58 --> 00:06:01 sky with some level of
00:06:01 --> 00:06:03 resolution and some telescopes have
00:06:04 --> 00:06:06 better resolution and some have blurrier
00:06:06 --> 00:06:08 vision linked to the size of the telescope.
00:06:08 --> 00:06:10 Typically, the bigger a telescope is, the
00:06:10 --> 00:06:13 better its resolution will be. For optical
00:06:13 --> 00:06:15 telescopes, the atmosphere puts a cap on
00:06:15 --> 00:06:17 that. Uh, unless you can do things to filter
00:06:17 --> 00:06:20 it out at about 1 arc second, very
00:06:20 --> 00:06:23 roughly, the turbulence of the
00:06:23 --> 00:06:25 atmosphere is a bit of a pain. But in theory,
00:06:25 --> 00:06:27 if you could take the atmosphere away, you
00:06:27 --> 00:06:30 would be able to see smaller things on the
00:06:30 --> 00:06:32 sky with a 10 metre diameter telescope than a
00:06:32 --> 00:06:35 1 metre telescope in the optical. And there's
00:06:35 --> 00:06:36 a mathematical relation for this that we
00:06:36 --> 00:06:39 teach our students at undergrad level. The
00:06:39 --> 00:06:41 resolution of the telescope, so what the
00:06:41 --> 00:06:43 smallest thing it can see is, if you ignore
00:06:43 --> 00:06:45 the atmosphere, if you look purely on the
00:06:45 --> 00:06:48 physics of it, is related to
00:06:48 --> 00:06:49 the diameter of the telescope. A bigger
00:06:49 --> 00:06:52 telescope will see a smaller resolution, but
00:06:52 --> 00:06:55 it's also related to the wavelength. So if
00:06:55 --> 00:06:57 you've got two telescopes of identical size
00:06:57 --> 00:06:59 and one's looking at optical and one's
00:06:59 --> 00:07:02 looking at radio waves, the radio waves are
00:07:02 --> 00:07:04 much longer wavelength, so the resolution of
00:07:04 --> 00:07:06 that telescope will be much lower.
00:07:07 --> 00:07:09 So radio telescopes of the same size as an
00:07:09 --> 00:07:11 optical telescope will get a blurrier image,
00:07:11 --> 00:07:14 but we can build radio telescopes much
00:07:14 --> 00:07:16 bigger. So there's swings and
00:07:16 --> 00:07:19 roundabouts there. But effectively what
00:07:19 --> 00:07:22 happens is you've got your image
00:07:22 --> 00:07:24 of the sky, the telescope looking at a patch
00:07:24 --> 00:07:27 of sky, and you've got a detector that
00:07:27 --> 00:07:30 counts the amount of radio waves
00:07:30 --> 00:07:31 impacting upon it in the form of photons
00:07:31 --> 00:07:33 impacting upon it. And that gives you a
00:07:33 --> 00:07:35 measure of how bright that bit of sky is.
00:07:36 --> 00:07:39 Now, if you've got multiple pixels, you can
00:07:39 --> 00:07:42 see different bits of that, uh, image
00:07:42 --> 00:07:45 in the same way as with a normal camera. One
00:07:45 --> 00:07:47 way. I think that this used to be done back
00:07:47 --> 00:07:49 in the very early days of radio or Ah, with
00:07:49 --> 00:07:51 very simple radio telescopes was all you're
00:07:51 --> 00:07:54 doing is you're counting the amount of radio
00:07:54 --> 00:07:56 waves hitting your detector. So you've got
00:07:56 --> 00:07:58 one pixel for your entire field of view and
00:07:58 --> 00:08:00 then you move your field around to make an
00:08:00 --> 00:08:02 image. So this part of the sky is this
00:08:02 --> 00:08:04 bright, the one next to it is this bright and
00:08:04 --> 00:08:06 so on, and you raster around to build up an
00:08:06 --> 00:08:09 image, you move around. Nowadays I
00:08:09 --> 00:08:12 think that you can get multiple pixels per
00:08:12 --> 00:08:14 field of view. In fact, you can get many.
00:08:14 --> 00:08:16 That's why we can get these beautiful high
00:08:16 --> 00:08:18 resolution images. And, uh, it's effectively
00:08:18 --> 00:08:21 working, albeit at different wavelengths, in
00:08:21 --> 00:08:24 the same kind of general science way as an
00:08:24 --> 00:08:26 optical detector. In that you've got a grid
00:08:26 --> 00:08:29 of pixels. Each pixel is sensitive
00:08:29 --> 00:08:31 to light falling upon that pixel and that
00:08:31 --> 00:08:34 pixel is seeing a certain bit of the sky. So
00:08:34 --> 00:08:36 you get a measure of how bright one bit of
00:08:36 --> 00:08:38 the sky is, how bright the next one is, how
00:08:38 --> 00:08:40 bright the next one is. That then gives you
00:08:40 --> 00:08:43 bright and faint. So you can then make a
00:08:43 --> 00:08:46 monochrome image where you plot
00:08:46 --> 00:08:48 those brightnesses as colours, from black
00:08:48 --> 00:08:51 being no light to white being some light and,
00:08:51 --> 00:08:53 um, really bright white being the
00:08:53 --> 00:08:55 brightest. Right. So you can build up an
00:08:55 --> 00:08:58 image where each pixel is a different
00:08:58 --> 00:09:01 brightness. Suddenly you've got a picture.
00:09:01 --> 00:09:02 Andrew Dunkley: Yeah.
00:09:02 --> 00:09:03 Jonti Horner: What you can do then is if you're sensitive
00:09:03 --> 00:09:06 to different wavelengths, you can
00:09:06 --> 00:09:08 combine those monochromatic images to make a
00:09:08 --> 00:09:11 colour image just the same way as I did with
00:09:11 --> 00:09:13 the one behind me. So the picture I've got on
00:09:13 --> 00:09:15 my screen, and this is useless to those of
00:09:15 --> 00:09:17 you listening, but anybody live in the
00:09:17 --> 00:09:18 studio, I've got a picture behind me of the
00:09:18 --> 00:09:21 Helix Nebula, which I took with my telescope
00:09:21 --> 00:09:24 here. And it's a beautiful kind of true
00:09:24 --> 00:09:25 colour image with a little bit of hydrogen
00:09:25 --> 00:09:28 alpha added for those listening in. But what
00:09:28 --> 00:09:30 I've done here is taken images that were
00:09:30 --> 00:09:32 black and white, that were taken through
00:09:32 --> 00:09:35 filters of blue, green and
00:09:35 --> 00:09:37 red and combine them to make a colour image.
00:09:37 --> 00:09:39 So you can do that to make false colour
00:09:39 --> 00:09:42 images in infrared or radio, uh,
00:09:42 --> 00:09:45 or whatever. Sometimes what you're seeing
00:09:45 --> 00:09:47 is effectively a monochromatic image, but
00:09:47 --> 00:09:48 instead of black and white, they've used
00:09:48 --> 00:09:50 black and yellow to make it look nice and
00:09:50 --> 00:09:52 colourful. But that's effectively what's
00:09:52 --> 00:09:54 going on. Now, I'm not a radio astronomer.
00:09:54 --> 00:09:57 There's subtleties and differences in the
00:09:57 --> 00:09:58 technology you need to observe at, ah,
00:09:58 --> 00:10:01 different wavelengths compared to optical.
00:10:01 --> 00:10:03 And I know that's equally true of the very
00:10:03 --> 00:10:05 high energy stuff like gamma rays and X rays
00:10:05 --> 00:10:07 that need clever little Bits of technology.
00:10:07 --> 00:10:09 Technology to be done. But fundamentally what
00:10:09 --> 00:10:11 you're doing to get an image is you're
00:10:11 --> 00:10:13 measuring the brightness of the sky in a
00:10:13 --> 00:10:16 given position at the wavelength you're
00:10:16 --> 00:10:18 interested in and ascribing that a colour.
00:10:18 --> 00:10:21 And then you're building a grid of those to
00:10:21 --> 00:10:23 make a picture which shows you the brighter
00:10:23 --> 00:10:25 areas and the fainter areas. And that's
00:10:25 --> 00:10:27 pretty much the same no matter what you're
00:10:27 --> 00:10:30 looking at. It's the same technique. It's
00:10:30 --> 00:10:32 just using different technology because
00:10:32 --> 00:10:34 you're looking at different energy levels,
00:10:34 --> 00:10:35 different wavelengths,
00:10:35 --> 00:10:38 Andrew Dunkley: which is how they got the, uh,
00:10:38 --> 00:10:41 image of Sagittarius A and
00:10:41 --> 00:10:43 m. Was it M37?
00:10:44 --> 00:10:46 Jonti Horner: Was it the one at the middle of M81?
00:10:46 --> 00:10:48 Andrew Dunkley: I think M81, yeah.
00:10:48 --> 00:10:50 Jonti Horner: So that's the, um, big global Black hole
00:10:50 --> 00:10:52 telescope. I can't remember the exact name of
00:10:52 --> 00:10:55 it, that took advantage of the
00:10:55 --> 00:10:58 long wavelength because you can do very
00:10:58 --> 00:11:01 clever things if you can work out
00:11:01 --> 00:11:03 where in a particular way of your
00:11:03 --> 00:11:06 detectors picking things up. So you can have
00:11:06 --> 00:11:09 distributed detectors that are part of the
00:11:09 --> 00:11:12 same telescope. Now, it's really hard to
00:11:12 --> 00:11:14 do this with optical. So, uh, people are
00:11:14 --> 00:11:15 playing with interferometry and things like
00:11:15 --> 00:11:18 that, uh, optical wavelengths. But for
00:11:18 --> 00:11:21 radio waves, it's possible for you to use
00:11:21 --> 00:11:24 detectors scattered all around the world to
00:11:24 --> 00:11:26 mimic having a detector that is a radio
00:11:26 --> 00:11:28 telescope that is the size of the Earth.
00:11:28 --> 00:11:29 Andrew Dunkley: Yeah.
00:11:29 --> 00:11:32 Jonti Horner: Um, and that then overcomes the problem that
00:11:32 --> 00:11:34 the wavelengths are longer by having a
00:11:34 --> 00:11:36 detector that is much, much bigger to get the
00:11:36 --> 00:11:38 kind of resolution that you get with an
00:11:38 --> 00:11:41 optical telescope or even better. And it's
00:11:41 --> 00:11:42 using that that they were able to get these
00:11:42 --> 00:11:45 beautiful resolved radio images of these
00:11:45 --> 00:11:48 black holes. They overcame the tyranny of
00:11:48 --> 00:11:50 resolution being, you know,
00:11:50 --> 00:11:53 limited by wavelength by making a really,
00:11:53 --> 00:11:55 really, really big telescope, effectively.
00:11:55 --> 00:11:58 Andrew Dunkley: M. Yeah, it worked really well. And so those
00:11:58 --> 00:12:00 images are a fair representation of what
00:12:01 --> 00:12:03 with the naked eye, from a distance.
00:12:03 --> 00:12:05 Jonti Horner: I suppose if you could see radio waves.
00:12:05 --> 00:12:07 Andrew Dunkley: Yeah, if you could, yes.
00:12:07 --> 00:12:08 Jonti Horner: Things will look different at, ah, different
00:12:08 --> 00:12:11 wavelengths. And you see that if you do play
00:12:11 --> 00:12:13 with astrophotography and you look through
00:12:13 --> 00:12:15 different filters, it is quite striking how
00:12:15 --> 00:12:17 different the same object will look in
00:12:17 --> 00:12:18 different colours when you're just looking in
00:12:18 --> 00:12:20 monochrome. And that's fundamentally how we
00:12:20 --> 00:12:22 do a lot of the science, how we work out what
00:12:22 --> 00:12:23 things are made of.
00:12:23 --> 00:12:26 Andrew Dunkley: Yeah, thank you, Thomas, Great question.
00:12:26 --> 00:12:28 Lovely to hear from you. Um, notwithstanding
00:12:28 --> 00:12:30 the Monty Python joke,
00:12:32 --> 00:12:33 Generic: Roger
00:12:33 --> 00:12:35 Jonti Horner: in your lives right here. Also space nuts.
00:12:36 --> 00:12:38 Andrew Dunkley: Our, uh, next question comes from
00:12:38 --> 00:12:41 Dean. Uh, he's not far from
00:12:41 --> 00:12:42 you Hi
00:12:42 --> 00:12:44 Andrew Dunkley: Fred Watson and Andrew, this is Dean in
00:12:44 --> 00:12:47 Redcliffe in Queensland. I often hear about
00:12:47 --> 00:12:49 gravity waves and I get a mental picture of a
00:12:49 --> 00:12:52 compression wave with dispersed particles in
00:12:52 --> 00:12:54 space getting closer together, then further
00:12:54 --> 00:12:57 apart as the wave passes. But I have a
00:12:57 --> 00:12:59 harder time visualising what happens as the
00:12:59 --> 00:13:01 wave passes through a solid body such as the
00:13:01 --> 00:13:04 Earth, where it can be detected by the LIGO
00:13:04 --> 00:13:07 interferometer. I think
00:13:07 --> 00:13:09 that it is space that is expanding and
00:13:09 --> 00:13:11 contracting rather than matter. But I'm not
00:13:11 --> 00:13:14 sure LIGO detects the
00:13:14 --> 00:13:16 gravity wave because the length of the four
00:13:16 --> 00:13:18 kilometre tunnel changes slightly.
00:13:19 --> 00:13:21 What's happening at a quantum scale
00:13:21 --> 00:13:24 as there is space within an atom, does the
00:13:24 --> 00:13:27 size of the atoms change or is it just the
00:13:27 --> 00:13:30 space between the atoms? I know
00:13:30 --> 00:13:32 that the effect at quantum scale would be
00:13:32 --> 00:13:34 minute. It's interesting to think about where
00:13:34 --> 00:13:37 the limit of space stretching might be. I
00:13:37 --> 00:13:39 suspect that I'm missing something with my
00:13:39 --> 00:13:41 understanding of this. I hope you can make
00:13:41 --> 00:13:44 some sense of it. Thanks for the podcast.
00:13:45 --> 00:13:47 Andrew Dunkley: Thank you, Dean. And uh, yeah,
00:13:48 --> 00:13:50 I think he's actually referring to
00:13:50 --> 00:13:52 gravitational waves because that's what LIGO
00:13:52 --> 00:13:55 searches for. But um, yeah, I've made that
00:13:55 --> 00:13:57 same mistake in the past where I call them
00:13:57 --> 00:14:00 gravity waves. Um, but
00:14:00 --> 00:14:01 gravity waves, wave is a different thing.
00:14:01 --> 00:14:03 They exist too, I think.
00:14:04 --> 00:14:07 Jonti Horner: Um, yes and no. So what's strange here is
00:14:07 --> 00:14:09 that I think you hear different terminology
00:14:09 --> 00:14:11 in different disciplines. So I think a lot of
00:14:11 --> 00:14:14 astronomers I've heard use the term gravity
00:14:14 --> 00:14:15 waves and gravitational waves almost
00:14:15 --> 00:14:17 interchangeably because that's what they're
00:14:17 --> 00:14:19 thinking about. But it's a really good
00:14:19 --> 00:14:22 example of how language is contextual
00:14:23 --> 00:14:25 in that the words you use, you use meaning
00:14:25 --> 00:14:27 one thing but another person may hear them
00:14:27 --> 00:14:29 and hear something entirely different because
00:14:29 --> 00:14:30 that same word can mean a different thing to
00:14:30 --> 00:14:33 someone else. So one other place I've heard
00:14:33 --> 00:14:36 the term gravity wave is actually in
00:14:36 --> 00:14:39 atmospheres and um, to do with fluid
00:14:39 --> 00:14:41 movement. And so you see
00:14:42 --> 00:14:45 things like um, I think lens clouds, delta
00:14:45 --> 00:14:48 cumulus lenticularis and um, wave
00:14:48 --> 00:14:50 clouds are associated with something that
00:14:50 --> 00:14:52 atmospheric scientists describe as gravity
00:14:52 --> 00:14:55 waves, which are things that happen when
00:14:55 --> 00:14:57 you've got the interface between two fluids
00:14:58 --> 00:15:00 and you've got steady airflow over things.
00:15:00 --> 00:15:03 And if you actually do a quick Google, I just
00:15:03 --> 00:15:05 fired this up and found the Wikipedia page
00:15:05 --> 00:15:08 for gravity wave. There are some absolutely
00:15:08 --> 00:15:10 beautiful images of
00:15:11 --> 00:15:13 wind driven gravity waves in the Timor Sea.
00:15:13 --> 00:15:15 You've got some beautiful wave clouds over
00:15:15 --> 00:15:18 the us, Little bits of maths. But this ties
00:15:18 --> 00:15:21 into, I think, something I used to see when I
00:15:21 --> 00:15:23 was doing weather recordings as a teenager in
00:15:23 --> 00:15:26 Yorkshire at school, because of the shape of
00:15:26 --> 00:15:27 the Pennines and the kind of airflow we got,
00:15:27 --> 00:15:30 we got lens clouds relatively frequently. And
00:15:30 --> 00:15:32 I think they are linked to the phenomenon
00:15:32 --> 00:15:33 that atmospheric scientists would often
00:15:33 --> 00:15:36 describe as gravity waves. For clarity,
00:15:36 --> 00:15:39 then, I think we should call what we're
00:15:39 --> 00:15:42 talking about here gravitational waves. And
00:15:42 --> 00:15:45 I think that's probably more accurate.
00:15:45 --> 00:15:48 And I think possibly astronomers slipping
00:15:48 --> 00:15:50 into calling gravitational waves gravity
00:15:50 --> 00:15:52 waves could be the cause of confusion to
00:15:52 --> 00:15:54 people who are thinking about weather.
00:15:54 --> 00:15:57 Gravitational waves, Dean was
00:15:57 --> 00:16:00 right. Are, uh, perturbations in the
00:16:00 --> 00:16:02 structure of space rather than
00:16:03 --> 00:16:06 matter itself shifting. This
00:16:06 --> 00:16:08 makes my head hurt. I should stress that I'm
00:16:08 --> 00:16:11 very much not an expert here and I know I say
00:16:11 --> 00:16:13 that very, very often, but I'm. You know,
00:16:13 --> 00:16:16 it's important to note that I'm not speaking
00:16:16 --> 00:16:18 from a position of great authority here,
00:16:19 --> 00:16:22 but what you're getting are, uh, a
00:16:22 --> 00:16:24 phenomenon that was first predicted in the
00:16:24 --> 00:16:26 late 1800s and early 1900s. Apparently the
00:16:26 --> 00:16:29 predictions predated Einstein, but he kind of
00:16:29 --> 00:16:31 formalised it through general relativity
00:16:32 --> 00:16:35 in the form of extreme, extreme
00:16:35 --> 00:16:38 events causing perturbations to space time
00:16:38 --> 00:16:40 that ripple outwards at the speed of light,
00:16:40 --> 00:16:43 causing, effectively, waves in
00:16:43 --> 00:16:46 the spacetime continuum, effectively
00:16:46 --> 00:16:49 in space itself, in the same thing that is
00:16:49 --> 00:16:50 stretching with the expansion of the
00:16:50 --> 00:16:53 universe. Those waves,
00:16:53 --> 00:16:55 as they pass through, are almost
00:16:55 --> 00:16:57 imperceptible. They don't really interact
00:16:57 --> 00:16:59 much with anything. But because
00:17:00 --> 00:17:02 they perturb, um, space, they can have a
00:17:02 --> 00:17:04 measurable effect in that they can change the
00:17:04 --> 00:17:07 distance between two points as the wave
00:17:07 --> 00:17:09 passes through. Now, there's some little
00:17:09 --> 00:17:11 animations trying to illustrate how waves
00:17:11 --> 00:17:14 would look, um, on the Wikipedia
00:17:14 --> 00:17:16 article about gravitational waves that are
00:17:16 --> 00:17:18 not really helping me because they're looking
00:17:18 --> 00:17:20 at what would happen if you had a circle of
00:17:20 --> 00:17:21 points and a wave pass through. And there's
00:17:21 --> 00:17:24 two ways it can wibble and it can go like a
00:17:24 --> 00:17:27 cross, or it can go like a square, like a
00:17:27 --> 00:17:29 plus sign. Sorry, that doesn't particularly
00:17:29 --> 00:17:31 help me visualise it. But what's happening,
00:17:32 --> 00:17:34 to the best of my understanding, is that
00:17:35 --> 00:17:37 you have this tiny little
00:17:37 --> 00:17:40 shift in space as the wave passes through,
00:17:41 --> 00:17:44 which means that ligo, which has
00:17:44 --> 00:17:46 these two arms at right angle to each other
00:17:46 --> 00:17:49 that are like four kilometres long, has light
00:17:49 --> 00:17:52 bouncing along these two arms. And when
00:17:52 --> 00:17:54 the length of one of those arms, um, shifts
00:17:54 --> 00:17:57 very slightly, the light will change from
00:17:57 --> 00:17:59 being constructively to destructively
00:17:59 --> 00:18:01 interfering with each other. So a very small,
00:18:02 --> 00:18:04 very, very small shift in distance
00:18:05 --> 00:18:07 means that the light, when it goes along and
00:18:07 --> 00:18:09 bounces back, will have travelled a slightly
00:18:09 --> 00:18:11 different distance and Then when you
00:18:11 --> 00:18:13 recombine it with the light that goes down
00:18:13 --> 00:18:14 the other arm, there'll be a little bit more
00:18:14 --> 00:18:16 in phase, out of phase. So you'll see the
00:18:16 --> 00:18:18 intensity of the result changing.
00:18:19 --> 00:18:20 Andrew Dunkley: Gotcha.
00:18:20 --> 00:18:22 Jonti Horner: What's astonishing about this is the
00:18:22 --> 00:18:25 figure that um, one of these gravitational
00:18:25 --> 00:18:27 waves that they detect is changing the
00:18:27 --> 00:18:30 length of one of those four kilometre arms
00:18:31 --> 00:18:33 by a thousandth of the width of a proton
00:18:33 --> 00:18:35 of a subatomic particle.
00:18:36 --> 00:18:37 Andrew Dunkley: That is a quantum level.
00:18:37 --> 00:18:40 Jonti Horner: Yeah, it's utterly quantum level. It's
00:18:40 --> 00:18:42 astonishing. The analogy that's been
00:18:42 --> 00:18:44 published about that, to put it into scale,
00:18:44 --> 00:18:45 is if you think about the distance between
00:18:45 --> 00:18:48 the sun and Proxima Centauri, it's like
00:18:48 --> 00:18:50 changing that distance by the width of a
00:18:50 --> 00:18:52 human hair. It's
00:18:53 --> 00:18:55 utterly mind boggling that we can detect
00:18:55 --> 00:18:58 this. It's an astonishing achievement. Now,
00:18:58 --> 00:19:01 my understanding is limited
00:19:01 --> 00:19:03 and, you know, really want to stress that
00:19:04 --> 00:19:06 what would happen as I understand it though
00:19:06 --> 00:19:09 is that it isn't just a distance between the
00:19:09 --> 00:19:11 subatomic particles that are changing, but
00:19:11 --> 00:19:13 they themselves will change. We would change
00:19:13 --> 00:19:15 as that wave goes through us because space
00:19:16 --> 00:19:18 itself would change, would fly us, but we
00:19:18 --> 00:19:21 wouldn't notice it. You know, that kind of
00:19:21 --> 00:19:23 change is tiny compared to us. But my
00:19:23 --> 00:19:26 understanding, Dean, is very
00:19:26 --> 00:19:28 much that, uh, the particles would change and
00:19:28 --> 00:19:29 the distance between them would change and
00:19:29 --> 00:19:31 everything will be slightly compressed and
00:19:31 --> 00:19:34 slightly relaxed. But I stand to be
00:19:34 --> 00:19:35 corrected in that. Yeah,
00:19:36 --> 00:19:38 it's very difficult to visualise and
00:19:39 --> 00:19:40 challenging to understand.
00:19:40 --> 00:19:43 Andrew Dunkley: Yeah. Um, so the wave moves through space,
00:19:43 --> 00:19:46 it affects space, but the space doesn't
00:19:46 --> 00:19:48 actually move with the wave. It's just like a
00:19:48 --> 00:19:51 wave in the ocean. It doesn't like the wave.
00:19:51 --> 00:19:52 Isn't the water moving?
00:19:52 --> 00:19:55 Jonti Horner: The water still moves up and down kind of
00:19:55 --> 00:19:56 thing. I think the water actually goes in a
00:19:56 --> 00:19:58 certain way circle, doesn't it, in a wave? So
00:19:58 --> 00:20:00 its average position is the same, but it
00:20:00 --> 00:20:02 rolls back and forth and the energy is
00:20:02 --> 00:20:03 propagated through.
00:20:03 --> 00:20:05 Andrew Dunkley: Correct. That's the way I understand
00:20:06 --> 00:20:09 it seems logical that waves in space would be
00:20:09 --> 00:20:12 the same. Um, completely
00:20:12 --> 00:20:14 different setup, but same effect
00:20:15 --> 00:20:15 essentially.
00:20:15 --> 00:20:17 I imagine what I think will be
00:20:17 --> 00:20:19 Jonti Horner: interesting, and I mean this is going
00:20:19 --> 00:20:21 slightly off topic into philosophy, is
00:20:22 --> 00:20:24 uh, how these ideas will become easier to
00:20:24 --> 00:20:27 explain over time. So I think when
00:20:27 --> 00:20:30 I was at uni, people were teaching special
00:20:30 --> 00:20:32 and general relativity and quantum mechanics
00:20:32 --> 00:20:35 as m modern physics as being quite
00:20:35 --> 00:20:38 new. And the students were understanding them
00:20:38 --> 00:20:40 a bit more easily than the people who taught
00:20:40 --> 00:20:42 them understood them when they were students,
00:20:42 --> 00:20:45 because we were about 80 years
00:20:45 --> 00:20:48 on from these discoveries. So the people who
00:20:48 --> 00:20:50 were teaching us had been taught by people
00:20:50 --> 00:20:52 where these discoveries had been made during
00:20:52 --> 00:20:54 their lifetimes, potentially. Given that
00:20:54 --> 00:20:56 you're often taught by the old academics.
00:20:57 --> 00:21:00 And initially the understanding of quantum
00:21:00 --> 00:21:02 mechanics and relativity was way
00:21:02 --> 00:21:05 postdoc. And then PhD students learned it
00:21:05 --> 00:21:07 and then uni students learned it. And now I
00:21:07 --> 00:21:09 believe it's taught at high school. So as
00:21:09 --> 00:21:12 time goes on and people can
00:21:12 --> 00:21:14 explain things to the next generation, our,
00:21:14 --> 00:21:16 uh, kind of societal understanding of these
00:21:16 --> 00:21:19 concepts gets better and they get accepted.
00:21:19 --> 00:21:21 And you suddenly get to the point where
00:21:22 --> 00:21:23 primary school kids are talking about special
00:21:23 --> 00:21:25 relativity. I mean, they're probably not
00:21:25 --> 00:21:27 talking about it in the mathematical terms,
00:21:27 --> 00:21:29 but some of the concep are now really
00:21:29 --> 00:21:32 embedded in culture. And I think part of the
00:21:32 --> 00:21:35 problem I have with gravitational
00:21:35 --> 00:21:37 waves is that whilst they had been
00:21:37 --> 00:21:39 predicted in a kind of niche way so long ago,
00:21:39 --> 00:21:42 the first observations were so recent that
00:21:42 --> 00:21:44 I wasn't taught about gravitational waves at
00:21:44 --> 00:21:47 uni. They weren't part of our courses. It's
00:21:47 --> 00:21:50 still really cutting edge new concepts.
00:21:51 --> 00:21:53 And so my understanding, therefore
00:21:53 --> 00:21:56 my explanation, it's woolly because I've
00:21:56 --> 00:21:59 never had it explained by someone who has had
00:21:59 --> 00:22:01 it explained by someone who's had it
00:22:01 --> 00:22:03 explained by someone. We've not had that
00:22:03 --> 00:22:05 buildup of conceptual
00:22:05 --> 00:22:08 description, I guess, to really embed this.
00:22:08 --> 00:22:10 And I find it really hard to get my head
00:22:10 --> 00:22:13 around the first observed gravitational wave,
00:22:13 --> 00:22:15 I think was 2015. This is a
00:22:15 --> 00:22:18 decade old. So it's probably like someone
00:22:18 --> 00:22:20 calling into the podcast in 1925
00:22:20 --> 00:22:22 asking me to explain general relativity.
00:22:24 --> 00:22:27 Andrew Dunkley: Yes. Yeah, that's a good analogy. Um,
00:22:27 --> 00:22:29 Dean, thanks for the question. Hope we, we
00:22:29 --> 00:22:30 covered all those little gaps you were
00:22:30 --> 00:22:33 talking about. Boom, boom. Uh, this is Space
00:22:33 --> 00:22:35 Nuts with Andrew Dunkley and Professor Johnty
00:22:35 --> 00:22:37 Horner. A, uh, Q A edition.
00:22:39 --> 00:22:41 Generic: I think we need to do a little more all
00:22:41 --> 00:22:42 weather testing.
00:22:43 --> 00:22:45 Andrew Dunkley: Amen, Space Nuts.
00:22:45 --> 00:22:48 Our next question comes
00:22:48 --> 00:22:49 from David.
00:22:49 --> 00:22:52 Andrew Dunkley: This is David from Port Washington, New York.
00:22:53 --> 00:22:55 And I was thinking back to when I was a
00:22:55 --> 00:22:57 teenager and I heard the recording of
00:22:57 --> 00:23:00 the resonant frequency of the universe and I
00:23:00 --> 00:23:02 thought it was very cool. I'm wondering if
00:23:02 --> 00:23:05 there was some kind of medium that sound
00:23:05 --> 00:23:08 could pass through in space, like, uh,
00:23:08 --> 00:23:11 water, uh, or even air.
00:23:11 --> 00:23:14 What would I be hearing? Uh, and would it be
00:23:14 --> 00:23:17 beautiful or would it be terrifying? What are
00:23:17 --> 00:23:19 the different resonant frequencies going on
00:23:19 --> 00:23:20 and big explosions?
00:23:21 --> 00:23:21 Generic: Really?
00:23:21 --> 00:23:22 Andrew Dunkley: Um, interested to know.
00:23:23 --> 00:23:23 Generic: Bonus.
00:23:23 --> 00:23:25 Andrew Dunkley: Um, question. If I could breathe in space,
00:23:25 --> 00:23:27 what would it smell like? But I'm more
00:23:27 --> 00:23:30 interested to know about the sounds. Okay,
00:23:30 --> 00:23:30 thanks guys.
00:23:31 --> 00:23:34 Andrew Dunkley: Thank you. David. I love this question. It's
00:23:34 --> 00:23:36 a little bit different. We haven't had uh,
00:23:36 --> 00:23:38 one like that for a while. Although I do
00:23:38 --> 00:23:41 recall we did talk about
00:23:41 --> 00:23:43 some time back about, um, I
00:23:43 --> 00:23:46 can't remember exactly what the object was,
00:23:46 --> 00:23:48 but they were talking about what it would
00:23:48 --> 00:23:50 smell like if you could smell it. And
00:23:50 --> 00:23:53 um, you know, and that was fascinating
00:23:53 --> 00:23:55 in itself. But don't ask me to remember what
00:23:55 --> 00:23:58 it was. I think it was rotten eggs.
00:23:58 --> 00:23:58 Andrew Dunkley: It is.
00:23:58 --> 00:24:00 Jonti Horner: I think that's a concept that's often used a
00:24:00 --> 00:24:01 bit like we talked about in the Last
00:24:01 --> 00:24:04 Questions episode about the raining diamonds
00:24:04 --> 00:24:06 and raining, um, precious gems,
00:24:07 --> 00:24:10 where people try to give you a
00:24:10 --> 00:24:12 hook that fits in with your day to day lived
00:24:12 --> 00:24:14 experience to help you visualise something
00:24:14 --> 00:24:16 more clearly. And the
00:24:16 --> 00:24:19 recording of the resonant frequency of the
00:24:19 --> 00:24:22 univers. It's another one of those. I think
00:24:22 --> 00:24:23 what we're talking about there is the
00:24:23 --> 00:24:25 microwave background, cosmic microwave
00:24:25 --> 00:24:28 background, which is this very low
00:24:28 --> 00:24:31 frequency now radio detection, um,
00:24:31 --> 00:24:34 equivalent to a black body at about 2.7
00:24:34 --> 00:24:37 Kelvin. That is a leftover hiss from
00:24:37 --> 00:24:40 the Big Bang, which, when Big bang happened
00:24:40 --> 00:24:43 about 300 years later, the universe went
00:24:43 --> 00:24:45 from being opaque to transparent. And all the
00:24:45 --> 00:24:47 radiation from the heat of the universe at
00:24:47 --> 00:24:49 that time went out into space. Universes
00:24:49 --> 00:24:52 got bigger, everything's got redshifted. So
00:24:52 --> 00:24:54 the peak of that spectrum now looks like a
00:24:54 --> 00:24:56 source. That was 2.7 Kelvin. And,
00:24:56 --> 00:24:59 um, that microwave
00:24:59 --> 00:25:01 background is the source of a lot of the
00:25:01 --> 00:25:03 static that you used to get if you tune your
00:25:03 --> 00:25:05 radio between stations or if you had an old
00:25:05 --> 00:25:07 TV where you had to tune in on the dial or
00:25:07 --> 00:25:09 move the antenna around and you just got the
00:25:09 --> 00:25:12 noise on the screen. A significant component
00:25:12 --> 00:25:14 of that was a macro background. And people
00:25:14 --> 00:25:17 have often tried to convert that into
00:25:17 --> 00:25:20 a sound to give people a kind of
00:25:20 --> 00:25:21 emotional connection, a way of visualising
00:25:21 --> 00:25:24 this. Um, although that's
00:25:24 --> 00:25:27 turning radio waves into a sound. Well, I
00:25:27 --> 00:25:29 guess we do that all the time with FM and AM
00:25:29 --> 00:25:31 broadcast, right?
00:25:31 --> 00:25:31 Andrew Dunkley: Yep.
00:25:31 --> 00:25:34 Jonti Horner: So, uh, it kind of makes sense to people in
00:25:34 --> 00:25:36 terms of what the universe would sound like.
00:25:36 --> 00:25:39 If there was a medium in space to transmit
00:25:39 --> 00:25:42 the sound, it would actually depend to some
00:25:42 --> 00:25:44 degree of the density of that medium as well.
00:25:44 --> 00:25:46 So the frequency that a given sound
00:25:46 --> 00:25:49 will sound like changes with
00:25:49 --> 00:25:52 atmospheric pressure. And I've seen examples
00:25:52 --> 00:25:54 of this where people have put an alarm bell,
00:25:55 --> 00:25:57 kind of alarm clock type, ringy bell noise
00:25:58 --> 00:26:01 in a big bell jar and evacuated the air
00:26:01 --> 00:26:02 from it. And as the air pressure got lower
00:26:02 --> 00:26:04 and lower, I think the pitch got higher and
00:26:04 --> 00:26:07 higher until the sound disappeared. So you've
00:26:07 --> 00:26:09 got a lot of different factors that would
00:26:09 --> 00:26:12 come into this to do with the composition
00:26:12 --> 00:26:14 of the medium, the density of the medium and
00:26:14 --> 00:26:17 stuff like that. But let's imagine just for a
00:26:17 --> 00:26:18 minute, because I think this is more of a
00:26:18 --> 00:26:21 science fiction question than a science fact
00:26:21 --> 00:26:22 one in a way. And I do love it as a question
00:26:22 --> 00:26:25 like that. If you were floating around in the
00:26:25 --> 00:26:27 solar system and you were uh, beyond the
00:26:27 --> 00:26:30 Earth's atmosphere, what would be the main
00:26:30 --> 00:26:32 source of noise that you'd experience?
00:26:33 --> 00:26:35 To me, I would actually guess the solar wind.
00:26:35 --> 00:26:37 Cause you have this flow of particles coming
00:26:37 --> 00:26:39 past you at a speed measured in hundreds of
00:26:39 --> 00:26:42 kilometres a second, 100, 200, 300 kilometres
00:26:42 --> 00:26:44 a second. So to me, I guess the main sound
00:26:44 --> 00:26:46 you would hear if you were beyond the Earth's
00:26:46 --> 00:26:49 atmosphere and there was enough medium for
00:26:49 --> 00:26:51 you to listen to, would actually be the sound
00:26:51 --> 00:26:53 of the wind blowing, but a really intense
00:26:53 --> 00:26:56 gale blowing. There have been
00:26:56 --> 00:26:59 discussions about what you'd hear on Mars.
00:26:59 --> 00:27:01 Now of course, on Mars the atmospheric
00:27:01 --> 00:27:03 pressure is much, much lower than even at the
00:27:03 --> 00:27:06 altitude of Everest. So that frequency
00:27:06 --> 00:27:08 shifting phenomenon would come in. So
00:27:08 --> 00:27:10 something that you'd hear as an ice deep bass
00:27:10 --> 00:27:12 note on Earth, I believe, would be a higher
00:27:12 --> 00:27:14 pitch on Mars quite markedly.
00:27:14 --> 00:27:15 Andrew Dunkley: Yeah.
00:27:15 --> 00:27:18 Jonti Horner: Darren Squeaky Y if you're listening
00:27:18 --> 00:27:20 to this podcast on Mars, please wear
00:27:20 --> 00:27:22 headphones. Otherwise I'll sound even more
00:27:22 --> 00:27:25 stupid than normal, I guess. Um,
00:27:25 --> 00:27:28 I would imagine that in terms
00:27:28 --> 00:27:30 of the concept of whether it would be
00:27:30 --> 00:27:33 beautiful or scary, I suspect it'd be like
00:27:33 --> 00:27:35 white noise with a lot of different
00:27:35 --> 00:27:38 components coming in. If you could visualise
00:27:38 --> 00:27:39 different astronomical phenomena
00:27:39 --> 00:27:42 contributing, a lot of them are time varying,
00:27:42 --> 00:27:45 a lot of them are bright flashes or
00:27:45 --> 00:27:47 whatever. So you'll probably have an
00:27:47 --> 00:27:49 underlying bass noise of whatever
00:27:49 --> 00:27:52 with lots of other things impinging on it.
00:27:52 --> 00:27:54 But it's really hard to say because we're
00:27:54 --> 00:27:56 trying to imagine a reality that is so, ah,
00:27:56 --> 00:27:59 different to our own. So I'm trying to find a
00:27:59 --> 00:28:01 way to contextualise that, I guess.
00:28:01 --> 00:28:04 Um, so it'd probably be a lot more like a
00:28:04 --> 00:28:07 white noise machine than something clear and
00:28:07 --> 00:28:09 beautiful. Possibly a white noise machine on
00:28:09 --> 00:28:10 a very windy day.
00:28:11 --> 00:28:13 Andrew Dunkley: Yeah. Sounds, um, in space, um,
00:28:16 --> 00:28:18 it's a difficult thing to try and get your
00:28:18 --> 00:28:21 head around because sound needs something to
00:28:21 --> 00:28:24 move through and space doesn't offer a lot of
00:28:24 --> 00:28:24 that.
00:28:25 --> 00:28:28 Jonti Horner: Absolutely. And I mean to maybe give you a
00:28:28 --> 00:28:29 different illustration of that. If you think
00:28:29 --> 00:28:31 about how sounds change when you go
00:28:31 --> 00:28:33 underwater, how different the world
00:28:33 --> 00:28:35 seems if you're snorkelling or you're doing a
00:28:35 --> 00:28:36 scuba Dive.
00:28:36 --> 00:28:36 Andrew Dunkley: Yeah.
00:28:36 --> 00:28:39 Jonti Horner: How all the sounds are so different to you.
00:28:39 --> 00:28:42 Andrew Dunkley: Yeah. I'll give you an example of sound
00:28:42 --> 00:28:45 and witnessing its movement. Uh, and this is
00:28:45 --> 00:28:48 not something I'd recommend, but, uh, we were
00:28:48 --> 00:28:50 standing on the rim of a volcano some years
00:28:50 --> 00:28:53 ago, and it was active and it was going
00:28:54 --> 00:28:56 in our faces. Actually, we had to leave
00:28:56 --> 00:28:59 because it was getting in our faces. Um,
00:28:59 --> 00:29:02 but watching the process of the eruption,
00:29:02 --> 00:29:04 you see it, it before
00:29:05 --> 00:29:08 you hear it, but you feel it
00:29:09 --> 00:29:12 also before you hear it, but not until after
00:29:12 --> 00:29:12 you see it.
00:29:12 --> 00:29:13 Andrew Dunkley: Yeah.
00:29:13 --> 00:29:16 Andrew Dunkley: So, uh, you see the explosion, you feel the
00:29:16 --> 00:29:19 rumble, and then you hear it, and
00:29:19 --> 00:29:22 then the shockwave hits you. Yeah, it's
00:29:22 --> 00:29:24 a really weird combination. And look, you're
00:29:24 --> 00:29:26 talking about a matter of
00:29:27 --> 00:29:29 all of this happening over in the course of
00:29:29 --> 00:29:31 about a second or a second, a half,
00:29:32 --> 00:29:35 depending on distance. But you see it, you
00:29:35 --> 00:29:37 feel it, you hear it,
00:29:38 --> 00:29:40 you feel it in the ground, and then you feel
00:29:40 --> 00:29:40 the shockwave.
00:29:40 --> 00:29:41 Andrew Dunkley: Yeah.
00:29:41 --> 00:29:44 Jonti Horner: And I mean, that fits in with how
00:29:45 --> 00:29:47 sound travels at different speeds. So what
00:29:47 --> 00:29:49 you feel under your feet is effectively waves
00:29:49 --> 00:29:52 that you'd probably hear as sound. But going
00:29:52 --> 00:29:54 through a solid medium, they travel faster.
00:29:54 --> 00:29:55 Andrew Dunkley: Exactly.
00:29:55 --> 00:29:57 Jonti Horner: Shockwaves are quicker. And I mean, that
00:29:57 --> 00:29:59 links in part to, uh, how we know so much
00:29:59 --> 00:30:01 about the interior of the Earth. Because
00:30:01 --> 00:30:04 shock waves from earthquakes travel at
00:30:04 --> 00:30:06 different speeds through different media. And
00:30:06 --> 00:30:08 you've got T waves and S waves
00:30:08 --> 00:30:10 propagating around the Earth. Ah, some going
00:30:10 --> 00:30:11 through the Earth's, uh, interior, being
00:30:11 --> 00:30:13 picked up at seismographs around the world
00:30:14 --> 00:30:16 that very clever people can use to reverse
00:30:16 --> 00:30:18 engineer what the interior structure of the
00:30:18 --> 00:30:21 Earth's like by those differences in speed.
00:30:22 --> 00:30:25 Andrew Dunkley: Yeah, it was a strange experience.
00:30:25 --> 00:30:27 And that was the last thing I expected to
00:30:27 --> 00:30:30 witness. I was a bit more concerned about
00:30:30 --> 00:30:32 what was falling out of the sky at the time.
00:30:33 --> 00:30:35 I'll tell you, though, um, I took a great
00:30:35 --> 00:30:37 photo as we were walking off.
00:30:37 --> 00:30:39 Uh, when you're in tour groups, there's
00:30:39 --> 00:30:41 always a straggler. So we're all halfway off
00:30:41 --> 00:30:44 the mountain, but someone decided to stay
00:30:44 --> 00:30:47 behind. And that's when the biggest bang of
00:30:47 --> 00:30:50 the day happened. And it flung lava bombs up
00:30:50 --> 00:30:52 in the sky the size of soccer balls.
00:30:53 --> 00:30:55 And I had already put my camera in my
00:30:55 --> 00:30:57 pocket. I, uh, turned it off. I had enough
00:30:57 --> 00:31:00 time to pull the camera out, turn it on
00:31:01 --> 00:31:03 focus, and take a photo of this woman staring
00:31:03 --> 00:31:05 up at lava bombs coming down.
00:31:06 --> 00:31:09 It's a great photo. Um, and then it was,
00:31:09 --> 00:31:11 uh, only a few weeks after I got home that my
00:31:11 --> 00:31:14 friend, uh, sent me a video that he'd Taken
00:31:15 --> 00:31:17 of one of those, uh, little eruptions and
00:31:18 --> 00:31:20 I didn't see it, but there was a lava bomb
00:31:20 --> 00:31:23 landed 20 metres in front of me. I never even
00:31:23 --> 00:31:26 saw it. And, yeah, that kind
00:31:26 --> 00:31:27 of freaked me out after the fact.
00:31:29 --> 00:31:32 Yeah, like I said, not something I recommend,
00:31:32 --> 00:31:35 but, boy, what an adrenaline jolt.
00:31:36 --> 00:31:38 Yeah, but there's a few
00:31:38 --> 00:31:40 volcanoes we've visited over the years and,
00:31:41 --> 00:31:43 um, they've all blown up since we've been to
00:31:43 --> 00:31:45 them. So the one at Vanuatu stopped air
00:31:45 --> 00:31:48 traffic. Uh, we were at Matt Etna,
00:31:49 --> 00:31:50 uh, a couple of years ago. Well, look what
00:31:50 --> 00:31:53 it's doing at the moment. Kilauea. It's gone
00:31:53 --> 00:31:55 off, like, several times since we were there.
00:31:55 --> 00:31:58 In fact, the observation deck in the
00:31:58 --> 00:32:00 caldera, uh, where we
00:32:01 --> 00:32:03 looked at Kilauea, was
00:32:03 --> 00:32:06 obliterated about a month after we were
00:32:06 --> 00:32:06 there.
00:32:08 --> 00:32:10 Jonti Horner: So when are you taking a holiday to Naples or
00:32:10 --> 00:32:11 to Yelliston?
00:32:11 --> 00:32:14 Andrew Dunkley: Well, actually, we've been to Naples, so,
00:32:14 --> 00:32:17 um, it wasn't, um,
00:32:17 --> 00:32:19 Vesuvius, though, that went off when we were
00:32:19 --> 00:32:21 there. It was, um, Stromboli.
00:32:21 --> 00:32:23 Jonti Horner: Yeah, well, they're quite worried about Campo
00:32:23 --> 00:32:26 Fiegri, I think it's called, which is Big
00:32:26 --> 00:32:29 Field under Naples. That, yes, will
00:32:29 --> 00:32:30 be a disaster when it goes.
00:32:31 --> 00:32:33 Andrew Dunkley: Well, like, if you go out
00:32:33 --> 00:32:36 into the. Into the bay and, and
00:32:36 --> 00:32:39 do a bit of, um, skin diving down to the. To
00:32:39 --> 00:32:41 the bottom, there's all this gas coming up
00:32:41 --> 00:32:42 through the sand, like.
00:32:43 --> 00:32:45 Jonti Horner: And I keep seeing reports of the amount of
00:32:45 --> 00:32:47 swelling of the lava dome and things like
00:32:47 --> 00:32:49 this. I mean, yeah, I personally would not
00:32:49 --> 00:32:51 feel all that comfortable living in that area
00:32:51 --> 00:32:52 or even necessarily visiting,
00:32:55 --> 00:32:57 but hopefully, you know, it will not be a
00:32:57 --> 00:32:59 problem within our lifetimes and the science
00:32:59 --> 00:33:01 will continue to improve to the level that
00:33:01 --> 00:33:03 they get enough warning to get everybody out
00:33:03 --> 00:33:03 when it goes.
00:33:04 --> 00:33:06 Andrew Dunkley: Yeah, that's the problem, isn't it? Uh, and
00:33:06 --> 00:33:09 even in, uh, New Zealand they've got, um, the
00:33:10 --> 00:33:12 dormant, uh, volcano in the
00:33:12 --> 00:33:15 harbour at Auckland. And
00:33:16 --> 00:33:18 I was talking to a journalist friend of mine
00:33:18 --> 00:33:21 who lived in New Zealand, uh, some years ago
00:33:21 --> 00:33:23 when I worked for the abc, and he was saying,
00:33:23 --> 00:33:26 look, it is a worry there too, if this thing
00:33:26 --> 00:33:28 ever wakes up. There are only two roads out
00:33:28 --> 00:33:31 of Wellington, uh, out of Auckland,
00:33:31 --> 00:33:34 and you've got a million people there or
00:33:34 --> 00:33:37 something. And how are they going to get
00:33:37 --> 00:33:37 out?
00:33:37 --> 00:33:39 Jonti Horner: It was actually fascinating. I was in New
00:33:39 --> 00:33:41 Zealand a couple of times earlier in the year
00:33:41 --> 00:33:43 and went through Auckland and spotted all
00:33:43 --> 00:33:44 these little humps and thought, that's
00:33:44 --> 00:33:46 interesting. Looked into it. I just pulled up
00:33:46 --> 00:33:49 the information here. The metropolitan area
00:33:49 --> 00:33:51 of Auckland contains 53
00:33:51 --> 00:33:54 volcanoes because it's a little volcanic
00:33:54 --> 00:33:56 field of these small little
00:33:57 --> 00:33:59 maas and tuff rings and all this stuff.
00:34:01 --> 00:34:03 Um, none of them are thought to have erupted
00:34:03 --> 00:34:05 more than once, except for one of them called
00:34:06 --> 00:34:09 Orangitoto. But it is
00:34:09 --> 00:34:10 an active volcanic area. Apparently the first
00:34:10 --> 00:34:13 vent in that area erupted 193
00:34:13 --> 00:34:15 years ago. And the most recent one was about
00:34:15 --> 00:34:16 600 years ago.
00:34:16 --> 00:34:17 Generic: Go.
00:34:17 --> 00:34:17 Andrew Dunkley: Yeah.
00:34:18 --> 00:34:19 Jonti Horner: Um, and that's from the one in the water,
00:34:20 --> 00:34:23 um, just east of the city. But,
00:34:23 --> 00:34:25 yeah, must be a fascinating place to live.
00:34:25 --> 00:34:28 But that plus the earthquakes,
00:34:29 --> 00:34:31 plus the psalms that get there. It's
00:34:31 --> 00:34:33 good to live in interesting times. But that
00:34:33 --> 00:34:35 might be a little bit too full on.
00:34:35 --> 00:34:38 Andrew Dunkley: Yeah. Well, we visited Christchurch,
00:34:38 --> 00:34:41 uh, coming up on four
00:34:41 --> 00:34:43 years ago now, and, uh, it had had that
00:34:43 --> 00:34:46 massive earthquake, that tragic earthquake.
00:34:46 --> 00:34:49 And, uh, even then you could. That
00:34:49 --> 00:34:51 they hadn't come close to rebuilding.
00:34:52 --> 00:34:55 And they even have, um, a
00:34:55 --> 00:34:57 museum, Quake City, I think it's called In
00:34:58 --> 00:35:00 Christchurch, which I highly recommend. It's
00:35:00 --> 00:35:01 fascinating. Yeah.
00:35:02 --> 00:35:04 Uh, we got off the topic, uh, did we talk
00:35:04 --> 00:35:06 about smells in space? If you could take a
00:35:06 --> 00:35:08 big inhale, what would it be like?
00:35:08 --> 00:35:09 Andrew Dunkley: I'm not sure.
00:35:09 --> 00:35:11 Jonti Horner: I mean, this is one of those things that
00:35:11 --> 00:35:14 people use to give you a handle
00:35:14 --> 00:35:17 to get on. So when we discover interesting
00:35:17 --> 00:35:19 things in the atmosphere of different places,
00:35:20 --> 00:35:23 usually, um, the things that relate to
00:35:23 --> 00:35:25 gases that we'd have on Earth are used to
00:35:25 --> 00:35:27 say, oh, this place would smell of whatever.
00:35:27 --> 00:35:29 Most common of them is hydrogen sulphide,
00:35:29 --> 00:35:32 which is your rotten egg smell, which is why
00:35:32 --> 00:35:34 people talk so much about exoplanets that
00:35:34 --> 00:35:37 smell like rotten eggs. But I think there was
00:35:37 --> 00:35:40 one recently that wasn't there. Something
00:35:40 --> 00:35:41 saying it was a giant gas cloud that would
00:35:41 --> 00:35:44 have smelled or tasted of strawberries. Big
00:35:44 --> 00:35:47 Said found a long chain hydrocarbon that was
00:35:47 --> 00:35:49 part of the test sensation. That is a nice,
00:35:49 --> 00:35:52 nice strawberry. So I think most of space
00:35:52 --> 00:35:55 would not smell particularly pleasant, but
00:35:55 --> 00:35:57 you wouldn't smell very much. But there's
00:35:57 --> 00:35:58 dust and debris around. But there's also a
00:35:58 --> 00:36:00 lot of gases that you really wouldn't want to
00:36:00 --> 00:36:02 inhale. I mean, I'm thinking of hydrogen
00:36:02 --> 00:36:05 cyanide and things like this. So, uh,
00:36:05 --> 00:36:06 inhale at your own risk.
00:36:07 --> 00:36:09 Andrew Dunkley: Well, I think you'd only inhale once in space
00:36:09 --> 00:36:10 and that'd be the end of that.
00:36:10 --> 00:36:11 Jonti Horner: Oh, absolutely, absolutely.
00:36:11 --> 00:36:13 Generic: Probably. All right.
00:36:13 --> 00:36:14 Andrew Dunkley: Uh, David, thanks for that. Great question.
00:36:14 --> 00:36:16 That was a lot of fun to discuss and brought
00:36:16 --> 00:36:18 up a lot of things in my mind about some of
00:36:18 --> 00:36:21 the experiences with sounds and smells I've
00:36:21 --> 00:36:22 had in my life.
00:36:22 --> 00:36:24 Uh, and that brings us to the end of a Q and
00:36:24 --> 00:36:26 A edition. If you would like to send us some
00:36:26 --> 00:36:28 questions, please do through our website
00:36:28 --> 00:36:31 spacenutspodcast.com spacenuts
00:36:31 --> 00:36:33 IO or do a search for SpaceNuts
00:36:33 --> 00:36:36 podcast in your favourite search engine. If
00:36:36 --> 00:36:37 you just do a search for Space Nuts, it'll
00:36:37 --> 00:36:39 take you to that horrible movie.
00:36:40 --> 00:36:42 Um, well, it's probably not that horrible,
00:36:43 --> 00:36:45 but anyway, uh, that's how you do it. Just
00:36:45 --> 00:36:47 click on the AMA tab and send us text or
00:36:47 --> 00:36:49 audio questions. And don't forget to tell us
00:36:49 --> 00:36:51 who you are and where you're from. And have a
00:36:51 --> 00:36:52 look around on our website while you're
00:36:52 --> 00:36:54 there. Jonty, thanks very much. Good to see
00:36:54 --> 00:36:55 you again.
00:36:55 --> 00:36:56 Jonti Horner: That's absolute pleasure. It's good to catch
00:36:56 --> 00:36:58 up and, you know, I'll catch you again the
00:36:58 --> 00:36:59 next time Fred Watson's on a jolt.
00:36:59 --> 00:37:01 Andrew Dunkley: Yeah, I think you'll be back after this
00:37:01 --> 00:37:03 episode, but we'll, um, we'll keep you on
00:37:03 --> 00:37:05 standby, but we'll talk again down the track.
00:37:06 --> 00:37:06 Jonti Horner: Absolutely.
00:37:06 --> 00:37:09 Andrew Dunkley: Look forward to it, Professor Jonty Horner,
00:37:09 --> 00:37:10 professor of Astrophysics at the University
00:37:10 --> 00:37:12 of Southern Queensland. And thanks to Huw in
00:37:12 --> 00:37:15 the studio, uh, who did actually turn up
00:37:15 --> 00:37:16 today, but they wouldn't let him in because
00:37:16 --> 00:37:19 he smells. And from me, Andrew Dunkley.
00:37:19 --> 00:37:20 Thanks for your company. We'll see you on the
00:37:20 --> 00:37:23 next episode of Space Nuts. Bye. Bye.
00:37:24 --> 00:37:26 You've been listening to the Space Nuts
00:37:26 --> 00:37:29 Jonti Horner: podcast, available at
00:37:29 --> 00:37:31 Apple Podcasts, Spotify,
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00:37:36 --> 00:37:37 demand@bytes.com.
00:37:38 --> 00:37:40 Andrew Dunkley: this has been another quality podcast
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