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

An episode of [Space Nuts: Astronomy Insights & Cosmic Discoveries](https://invisiblenetwork.ai/podcast/1080090608), 31 Aug 2026, 38 min.

Audio: https://dts.podtrac.com/redirect.mp3/pscrb.fm/rss/p/op3.dev/e/api.spreaker.com/download/episode/74761230/waves_signals_and_cosmic_aromas_a_q_a_journey_through_space.mp3

In this intriguing Q&A episode of Space Nuts, hosts Andrew Dunkley and Professor Jonti Horner tackle a variety of cosmic queries from listeners. Join them as they explore the fascinating world of radio telescopes and how they produce images from radio waves, delve into the complexities of gravitational waves, and ponder the sounds and smells of space. 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.

## Transcript

[0:00] Andrew Dunkley: Hello again. Thanks for joining us on a Q and
[0:02] A edition of Space Nuts, where we talk
[0:05] astronomy and space science and we
[0:07] endeavour to answer, uh, questions from
[0:10] our audience. We've got a few good questions
[0:12] today, unlike all the bad ones we had
[0:15] previously. Uh, we're going to talk about
[0:17] radio telescope imagery. What does that
[0:20] mean? How does it work? I don't understand.
[0:23] And that's just me. Um, we also
[0:26] are going to be talking gravity waves. Now,
[0:28] I'm not sure if it's gravity or
[0:30] gravitational. They are different things. Uh,
[0:33] and also, uh, sounds and smells in space.
[0:36] What would they be like if you could stick
[0:39] your schnoz beyond our atmosphere? We'll talk
[0:41] about all of that on this edition of space
[0:44] nuts.
[0:44] Generic: 15 seconds. Guidance is internal.
[0:47] 10, 9. Uh, ignition
[0:50] sequence start.
[0:51] Jonti Horner: Space nuts.
[0:52] Generic: 5, 4, 3, 2, 1. 2, 3,
[0:54] 4, 5, 4, 3, 2', 1.
[0:57] Jonti Horner: Space nuts.
[0:58] Generic: Astronauts report it feels good.
[1:01] Andrew Dunkley: He's back again. He is Professor Jonty
[1:03] Horner, professor of Astrophysics at the
[1:05] University of Southern Queensland. Hi, Jonty.
[1:07] Jonti Horner: Good afternoon. How are you going? I am well.
[1:09] Andrew Dunkley: Good to see you again.
[1:11] Jonti Horner: It's good to be back. I think I'm going to be
[1:12] doing a lot of. I'm not sure, but today I
[1:15] think we've got questions that are a little
[1:16] out of my area of expertise. Um, I'd always
[1:20] like to flag up at the start when things are
[1:22] less my field because we don't all know
[1:25] everything. And it's good to, rather than
[1:27] pretend, good to be open about what I do and
[1:30] don't know.
[1:31] Andrew Dunkley: Fair enough.
[1:32] Andrew Dunkley: But, uh, we'll do our very best. I
[1:35] got the easy part. I just get to ask the
[1:36] questions.
[1:37] Let's, uh, get straight to our first one.
[1:40] And this one, uh, asks how is
[1:43] a photographic image produced from a radio
[1:45] telescope when all they are receiving is
[1:48] radio waves and not an optical image through
[1:51] a telescope lens? Uh, that's, uh,
[1:54] from Thomas in Canberra. He's thrown in a
[1:56] supplementary Monty Python, Monty Python
[1:59] style question. Were the pyramids built
[2:02] by aliens? Does that sound
[2:05] fair enough?
[2:06] Andrew Dunkley: Uh,
[2:09] Andrew Dunkley: horrible, dad joke.
[2:11] Andrew Dunkley: Horrible.
[2:13] Jonti Horner: But if you want to keep your
[2:14] Andrew Dunkley: razor sharp, I did see an article only
[2:17] a few days ago about, uh, a new theory into
[2:20] the building of the pyramids. But we went to
[2:22] Egypt a few years ago and they are, uh, quite
[2:25] adamant that, um, not only were they built
[2:28] by humans, they were built by
[2:31] what you would call contractors. They were
[2:33] not slaves. The people that built the
[2:35] pyramids, according to the locals, were
[2:38] actually employed.
[2:40] Jonti Horner: Yeah, lots of discussion of that. My partner
[2:43] Ness, is an avid history buff and
[2:46] also Likes to watch a bit of TV when she's
[2:48] trying to relax, to go to sleep. So I'm m
[2:50] constantly seeing archaeological
[2:52] documentaries and things like that. And she
[2:53] loves the Egyptians. So I've seen lots and
[2:56] lots of documentaries talking about this. And
[2:58] it turns out, if what I've seen in these
[3:00] shows can be believed, that it was actually
[3:02] fairly prestigious and fairly good working
[3:04] conditions to be one of the contractors
[3:07] working on the pyramids kind of building
[3:08] that. So.
[3:09] Andrew Dunkley: Yeah, I heard that too. Yes, exactly.
[3:11] Jonti Horner: Crack the big whips and all the rest of it.
[3:13] Andrew Dunkley: But yeah, yeah, no, it's fascinating
[3:16] history. Wouldn't you love a time machine
[3:18] just to go back and go, ah, uh, look.
[3:20] Andrew Dunkley: Yeah,
[3:22] Andrew Dunkley: now that we're seeing it, it looks easy.
[3:25] Jonti Horner: Uh, absolutely. I mean, I probably end up
[3:27] being really kind of busman's holiday though,
[3:29] with the time machine and going back to
[3:31] different astronomical events and think like,
[3:33] trying figure out if Caesar's Comet was
[3:35] actually real, you know, and, you know,
[3:38] trying to see if there were multiple sun
[3:40] grazing comets visible with the naked eye in
[3:42] daylight in I think it was 363 A.D. so
[3:45] I'd probably end up picking myself an
[3:47] astronomical holiday tour, um,
[3:51] not getting distracted by all the kind of
[3:52] human history stuff.
[3:54] Andrew Dunkley: Yeah, fair enough. I mean, you go nuts
[3:56] thinking about things to go back and see.
[3:58] Absolutely.
[3:59] Jonti Horner: Or going forward. I've said a few times that
[4:01] given the predictions we talked about last
[4:03] year, that Comet Duchesso, Comic
[4:06] Linkenberg, will return in the year 2097.
[4:09] That could well be the best comet of this
[4:11] century. I'd quite like to see it, but
[4:14] unless I am fortunate enough to reach 119
[4:17] years old, I think it unlikely. So,
[4:20] you know, time machine would be welcome.
[4:22] Andrew Dunkley: Yeah, it would. I'm working on it.
[4:26] Uh, so let's go to the first part of the
[4:28] question. Uh, how is a photographic image
[4:31] produced from a radio telescope when
[4:33] all they receive is radio waves and not an
[4:35] optical image through a telescope lens? Yeah,
[4:38] I've got to admit, this one confuses me a
[4:41] bit.
[4:42] Jonti Horner: We could say the same for infrared. We could
[4:44] say the same for gamma rays or X rays or for
[4:47] optical photographs. Right. So all of those
[4:49] different forms of radiation I just mentioned
[4:51] are different, uh, parts of the
[4:53] electromagnetic spectrum. So they're
[4:54] fundamentally the same thing but with
[4:56] different wavelengths in just the same way
[4:58] that red light and blue light are
[5:00] electromagnetic waves, but blue has a shorter
[5:02] wavelength and red has a longer wavelength.
[5:05] And um, I've got an astro photo behind me of
[5:07] the Helix Nebula. If I had a camera that was
[5:10] more sensitive to infrared, I would have
[5:12] picked out some slightly different features
[5:13] there because there is radiation coming in of
[5:16] different wavelengths. The way it
[5:19] works with a radio telescope or the way that
[5:21] it works with an M infrared detector or
[5:24] whatever is, you've got a detector
[5:26] that can detect radiation of that
[5:29] wavelength. Um, with an optical photo,
[5:33] you have a DSLR camera or a CCD camera that
[5:35] is sensitive to optical light and
[5:38] you get photons hitting the detector and
[5:41] creating electrons that are countered in the
[5:43] same way. For a radio telescope, you have a
[5:45] detector that is sensitive to radio waves
[5:48] and when photons of the right energy hit the
[5:50] detector, they create electrons and they get
[5:52] countered. So what happens is you've got your
[5:55] radio telescope that can look at a patch of
[5:58] sky with some level of
[6:01] resolution and some telescopes have
[6:04] better resolution and some have blurrier
[6:06] vision linked to the size of the telescope.
[6:08] Typically, the bigger a telescope is, the
[6:10] better its resolution will be. For optical
[6:13] telescopes, the atmosphere puts a cap on
[6:15] that. Uh, unless you can do things to filter
[6:17] it out at about 1 arc second, very
[6:20] roughly, the turbulence of the
[6:23] atmosphere is a bit of a pain. But in theory,
[6:25] if you could take the atmosphere away, you
[6:27] would be able to see smaller things on the
[6:30] sky with a 10 metre diameter telescope than a
[6:32] 1 metre telescope in the optical. And there's
[6:35] a mathematical relation for this that we
[6:36] teach our students at undergrad level. The
[6:39] resolution of the telescope, so what the
[6:41] smallest thing it can see is, if you ignore
[6:43] the atmosphere, if you look purely on the
[6:45] physics of it, is related to
[6:48] the diameter of the telescope. A bigger
[6:49] telescope will see a smaller resolution, but
[6:52] it's also related to the wavelength. So if
[6:55] you've got two telescopes of identical size
[6:57] and one's looking at optical and one's
[6:59] looking at radio waves, the radio waves are
[7:02] much longer wavelength, so the resolution of
[7:04] that telescope will be much lower.
[7:07] So radio telescopes of the same size as an
[7:09] optical telescope will get a blurrier image,
[7:11] but we can build radio telescopes much
[7:14] bigger. So there's swings and
[7:16] roundabouts there. But effectively what
[7:19] happens is you've got your image
[7:22] of the sky, the telescope looking at a patch
[7:24] of sky, and you've got a detector that
[7:27] counts the amount of radio waves
[7:30] impacting upon it in the form of photons
[7:31] impacting upon it. And that gives you a
[7:33] measure of how bright that bit of sky is.
[7:36] Now, if you've got multiple pixels, you can
[7:39] see different bits of that, uh, image
[7:42] in the same way as with a normal camera. One
[7:45] way. I think that this used to be done back
[7:47] in the very early days of radio or Ah, with
[7:49] very simple radio telescopes was all you're
[7:51] doing is you're counting the amount of radio
[7:54] waves hitting your detector. So you've got
[7:56] one pixel for your entire field of view and
[7:58] then you move your field around to make an
[8:00] image. So this part of the sky is this
[8:02] bright, the one next to it is this bright and
[8:04] so on, and you raster around to build up an
[8:06] image, you move around. Nowadays I
[8:09] think that you can get multiple pixels per
[8:12] field of view. In fact, you can get many.
[8:14] That's why we can get these beautiful high
[8:16] resolution images. And, uh, it's effectively
[8:18] working, albeit at different wavelengths, in
[8:21] the same kind of general science way as an
[8:24] optical detector. In that you've got a grid
[8:26] of pixels. Each pixel is sensitive
[8:29] to light falling upon that pixel and that
[8:31] pixel is seeing a certain bit of the sky. So
[8:34] you get a measure of how bright one bit of
[8:36] the sky is, how bright the next one is, how
[8:38] bright the next one is. That then gives you
[8:40] bright and faint. So you can then make a
[8:43] monochrome image where you plot
[8:46] those brightnesses as colours, from black
[8:48] being no light to white being some light and,
[8:51] um, really bright white being the
[8:53] brightest. Right. So you can build up an
[8:55] image where each pixel is a different
[8:58] brightness. Suddenly you've got a picture.
[9:01] Andrew Dunkley: Yeah.
[9:02] Jonti Horner: What you can do then is if you're sensitive
[9:03] to different wavelengths, you can
[9:06] combine those monochromatic images to make a
[9:08] colour image just the same way as I did with
[9:11] the one behind me. So the picture I've got on
[9:13] my screen, and this is useless to those of
[9:15] you listening, but anybody live in the
[9:17] studio, I've got a picture behind me of the
[9:18] Helix Nebula, which I took with my telescope
[9:21] here. And it's a beautiful kind of true
[9:24] colour image with a little bit of hydrogen
[9:25] alpha added for those listening in. But what
[9:28] I've done here is taken images that were
[9:30] black and white, that were taken through
[9:32] filters of blue, green and
[9:35] red and combine them to make a colour image.
[9:37] So you can do that to make false colour
[9:39] images in infrared or radio, uh,
[9:42] or whatever. Sometimes what you're seeing
[9:45] is effectively a monochromatic image, but
[9:47] instead of black and white, they've used
[9:48] black and yellow to make it look nice and
[9:50] colourful. But that's effectively what's
[9:52] going on. Now, I'm not a radio astronomer.
[9:54] There's subtleties and differences in the
[9:57] technology you need to observe at, ah,
[9:58] different wavelengths compared to optical.
[10:01] And I know that's equally true of the very
[10:03] high energy stuff like gamma rays and X rays
[10:05] that need clever little Bits of technology.
[10:07] Technology to be done. But fundamentally what
[10:09] you're doing to get an image is you're
[10:11] measuring the brightness of the sky in a
[10:13] given position at the wavelength you're
[10:16] interested in and ascribing that a colour.
[10:18] And then you're building a grid of those to
[10:21] make a picture which shows you the brighter
[10:23] areas and the fainter areas. And that's
[10:25] pretty much the same no matter what you're
[10:27] looking at. It's the same technique. It's
[10:30] just using different technology because
[10:32] you're looking at different energy levels,
[10:34] different wavelengths,
[10:35] Andrew Dunkley: which is how they got the, uh,
[10:38] image of Sagittarius A and
[10:41] m. Was it M37?
[10:44] Jonti Horner: Was it the one at the middle of M81?
[10:46] Andrew Dunkley: I think M81, yeah.
[10:48] Jonti Horner: So that's the, um, big global Black hole
[10:50] telescope. I can't remember the exact name of
[10:52] it, that took advantage of the
[10:55] long wavelength because you can do very
[10:58] clever things if you can work out
[11:01] where in a particular way of your
[11:03] detectors picking things up. So you can have
[11:06] distributed detectors that are part of the
[11:09] same telescope. Now, it's really hard to
[11:12] do this with optical. So, uh, people are
[11:14] playing with interferometry and things like
[11:15] that, uh, optical wavelengths. But for
[11:18] radio waves, it's possible for you to use
[11:21] detectors scattered all around the world to
[11:24] mimic having a detector that is a radio
[11:26] telescope that is the size of the Earth.
[11:28] Andrew Dunkley: Yeah.
[11:29] Jonti Horner: Um, and that then overcomes the problem that
[11:32] the wavelengths are longer by having a
[11:34] detector that is much, much bigger to get the
[11:36] kind of resolution that you get with an
[11:38] optical telescope or even better. And it's
[11:41] using that that they were able to get these
[11:42] beautiful resolved radio images of these
[11:45] black holes. They overcame the tyranny of
[11:48] resolution being, you know,
[11:50] limited by wavelength by making a really,
[11:53] really, really big telescope, effectively.
[11:55] Andrew Dunkley: M. Yeah, it worked really well. And so those
[11:58] images are a fair representation of what
[12:01] with the naked eye, from a distance.
[12:03] Jonti Horner: I suppose if you could see radio waves.
[12:05] Andrew Dunkley: Yeah, if you could, yes.
[12:07] Jonti Horner: Things will look different at, ah, different
[12:08] wavelengths. And you see that if you do play
[12:11] with astrophotography and you look through
[12:13] different filters, it is quite striking how
[12:15] different the same object will look in
[12:17] different colours when you're just looking in
[12:18] monochrome. And that's fundamentally how we
[12:20] do a lot of the science, how we work out what
[12:22] things are made of.
[12:23] Andrew Dunkley: Yeah, thank you, Thomas, Great question.
[12:26] Lovely to hear from you. Um, notwithstanding
[12:28] the Monty Python joke,
[12:32] Generic: Roger
[12:33] Jonti Horner: in your lives right here. Also space nuts.
[12:36] Andrew Dunkley: Our, uh, next question comes from
[12:38] Dean. Uh, he's not far from
[12:41] you Hi
[12:42] Andrew Dunkley: Fred Watson and Andrew, this is Dean in
[12:44] Redcliffe in Queensland. I often hear about
[12:47] gravity waves and I get a mental picture of a
[12:49] compression wave with dispersed particles in
[12:52] space getting closer together, then further
[12:54] apart as the wave passes. But I have a
[12:57] harder time visualising what happens as the
[12:59] wave passes through a solid body such as the
[13:01] Earth, where it can be detected by the LIGO
[13:04] interferometer. I think
[13:07] that it is space that is expanding and
[13:09] contracting rather than matter. But I'm not
[13:11] sure LIGO detects the
[13:14] gravity wave because the length of the four
[13:16] kilometre tunnel changes slightly.
[13:19] What's happening at a quantum scale
[13:21] as there is space within an atom, does the
[13:24] size of the atoms change or is it just the
[13:27] space between the atoms? I know
[13:30] that the effect at quantum scale would be
[13:32] minute. It's interesting to think about where
[13:34] the limit of space stretching might be. I
[13:37] suspect that I'm missing something with my
[13:39] understanding of this. I hope you can make
[13:41] some sense of it. Thanks for the podcast.
[13:45] Andrew Dunkley: Thank you, Dean. And uh, yeah,
[13:48] I think he's actually referring to
[13:50] gravitational waves because that's what LIGO
[13:52] searches for. But um, yeah, I've made that
[13:55] same mistake in the past where I call them
[13:57] gravity waves. Um, but
[14:00] gravity waves, wave is a different thing.
[14:01] They exist too, I think.
[14:04] Jonti Horner: Um, yes and no. So what's strange here is
[14:07] that I think you hear different terminology
[14:09] in different disciplines. So I think a lot of
[14:11] astronomers I've heard use the term gravity
[14:14] waves and gravitational waves almost
[14:15] interchangeably because that's what they're
[14:17] thinking about. But it's a really good
[14:19] example of how language is contextual
[14:23] in that the words you use, you use meaning
[14:25] one thing but another person may hear them
[14:27] and hear something entirely different because
[14:29] that same word can mean a different thing to
[14:30] someone else. So one other place I've heard
[14:33] the term gravity wave is actually in
[14:36] atmospheres and um, to do with fluid
[14:39] movement. And so you see
[14:42] things like um, I think lens clouds, delta
[14:45] cumulus lenticularis and um, wave
[14:48] clouds are associated with something that
[14:50] atmospheric scientists describe as gravity
[14:52] waves, which are things that happen when
[14:55] you've got the interface between two fluids
[14:58] and you've got steady airflow over things.
[15:00] And if you actually do a quick Google, I just
[15:03] fired this up and found the Wikipedia page
[15:05] for gravity wave. There are some absolutely
[15:08] beautiful images of
[15:11] wind driven gravity waves in the Timor Sea.
[15:13] You've got some beautiful wave clouds over
[15:15] the us, Little bits of maths. But this ties
[15:18] into, I think, something I used to see when I
[15:21] was doing weather recordings as a teenager in
[15:23] Yorkshire at school, because of the shape of
[15:26] the Pennines and the kind of airflow we got,
[15:27] we got lens clouds relatively frequently. And
[15:30] I think they are linked to the phenomenon
[15:32] that atmospheric scientists would often
[15:33] describe as gravity waves. For clarity,
[15:36] then, I think we should call what we're
[15:39] talking about here gravitational waves. And
[15:42] I think that's probably more accurate.
[15:45] And I think possibly astronomers slipping
[15:48] into calling gravitational waves gravity
[15:50] waves could be the cause of confusion to
[15:52] people who are thinking about weather.
[15:54] Gravitational waves, Dean was
[15:57] right. Are, uh, perturbations in the
[16:00] structure of space rather than
[16:03] matter itself shifting. This
[16:06] makes my head hurt. I should stress that I'm
[16:08] very much not an expert here and I know I say
[16:11] that very, very often, but I'm. You know,
[16:13] it's important to note that I'm not speaking
[16:16] from a position of great authority here,
[16:19] but what you're getting are, uh, a
[16:22] phenomenon that was first predicted in the
[16:24] late 1800s and early 1900s. Apparently the
[16:26] predictions predated Einstein, but he kind of
[16:29] formalised it through general relativity
[16:32] in the form of extreme, extreme
[16:35] events causing perturbations to space time
[16:38] that ripple outwards at the speed of light,
[16:40] causing, effectively, waves in
[16:43] the spacetime continuum, effectively
[16:46] in space itself, in the same thing that is
[16:49] stretching with the expansion of the
[16:50] universe. Those waves,
[16:53] as they pass through, are almost
[16:55] imperceptible. They don't really interact
[16:57] much with anything. But because
[17:00] they perturb, um, space, they can have a
[17:02] measurable effect in that they can change the
[17:04] distance between two points as the wave
[17:07] passes through. Now, there's some little
[17:09] animations trying to illustrate how waves
[17:11] would look, um, on the Wikipedia
[17:14] article about gravitational waves that are
[17:16] not really helping me because they're looking
[17:18] at what would happen if you had a circle of
[17:20] points and a wave pass through. And there's
[17:21] two ways it can wibble and it can go like a
[17:24] cross, or it can go like a square, like a
[17:27] plus sign. Sorry, that doesn't particularly
[17:29] help me visualise it. But what's happening,
[17:32] to the best of my understanding, is that
[17:35] you have this tiny little
[17:37] shift in space as the wave passes through,
[17:41] which means that ligo, which has
[17:44] these two arms at right angle to each other
[17:46] that are like four kilometres long, has light
[17:49] bouncing along these two arms. And when
[17:52] the length of one of those arms, um, shifts
[17:54] very slightly, the light will change from
[17:57] being constructively to destructively
[17:59] interfering with each other. So a very small,
[18:02] very, very small shift in distance
[18:05] means that the light, when it goes along and
[18:07] bounces back, will have travelled a slightly
[18:09] different distance and Then when you
[18:11] recombine it with the light that goes down
[18:13] the other arm, there'll be a little bit more
[18:14] in phase, out of phase. So you'll see the
[18:16] intensity of the result changing.
[18:19] Andrew Dunkley: Gotcha.
[18:20] Jonti Horner: What's astonishing about this is the
[18:22] figure that um, one of these gravitational
[18:25] waves that they detect is changing the
[18:27] length of one of those four kilometre arms
[18:31] by a thousandth of the width of a proton
[18:33] of a subatomic particle.
[18:36] Andrew Dunkley: That is a quantum level.
[18:37] Jonti Horner: Yeah, it's utterly quantum level. It's
[18:40] astonishing. The analogy that's been
[18:42] published about that, to put it into scale,
[18:44] is if you think about the distance between
[18:45] the sun and Proxima Centauri, it's like
[18:48] changing that distance by the width of a
[18:50] human hair. It's
[18:53] utterly mind boggling that we can detect
[18:55] this. It's an astonishing achievement. Now,
[18:58] my understanding is limited
[19:01] and, you know, really want to stress that
[19:04] what would happen as I understand it though
[19:06] is that it isn't just a distance between the
[19:09] subatomic particles that are changing, but
[19:11] they themselves will change. We would change
[19:13] as that wave goes through us because space
[19:16] itself would change, would fly us, but we
[19:18] wouldn't notice it. You know, that kind of
[19:21] change is tiny compared to us. But my
[19:23] understanding, Dean, is very
[19:26] much that, uh, the particles would change and
[19:28] the distance between them would change and
[19:29] everything will be slightly compressed and
[19:31] slightly relaxed. But I stand to be
[19:34] corrected in that. Yeah,
[19:36] it's very difficult to visualise and
[19:39] challenging to understand.
[19:40] Andrew Dunkley: Yeah. Um, so the wave moves through space,
[19:43] it affects space, but the space doesn't
[19:46] actually move with the wave. It's just like a
[19:48] wave in the ocean. It doesn't like the wave.
[19:51] Isn't the water moving?
[19:52] Jonti Horner: The water still moves up and down kind of
[19:55] thing. I think the water actually goes in a
[19:56] certain way circle, doesn't it, in a wave? So
[19:58] its average position is the same, but it
[20:00] rolls back and forth and the energy is
[20:02] propagated through.
[20:03] Andrew Dunkley: Correct. That's the way I understand
[20:06] it seems logical that waves in space would be
[20:09] the same. Um, completely
[20:12] different setup, but same effect
[20:15] essentially.
[20:15] I imagine what I think will be
[20:17] Jonti Horner: interesting, and I mean this is going
[20:19] slightly off topic into philosophy, is
[20:22] uh, how these ideas will become easier to
[20:24] explain over time. So I think when
[20:27] I was at uni, people were teaching special
[20:30] and general relativity and quantum mechanics
[20:32] as m modern physics as being quite
[20:35] new. And the students were understanding them
[20:38] a bit more easily than the people who taught
[20:40] them understood them when they were students,
[20:42] because we were about 80 years
[20:45] on from these discoveries. So the people who
[20:48] were teaching us had been taught by people
[20:50] where these discoveries had been made during
[20:52] their lifetimes, potentially. Given that
[20:54] you're often taught by the old academics.
[20:57] And initially the understanding of quantum
[21:00] mechanics and relativity was way
[21:02] postdoc. And then PhD students learned it
[21:05] and then uni students learned it. And now I
[21:07] believe it's taught at high school. So as
[21:09] time goes on and people can
[21:12] explain things to the next generation, our,
[21:14] uh, kind of societal understanding of these
[21:16] concepts gets better and they get accepted.
[21:19] And you suddenly get to the point where
[21:22] primary school kids are talking about special
[21:23] relativity. I mean, they're probably not
[21:25] talking about it in the mathematical terms,
[21:27] but some of the concep are now really
[21:29] embedded in culture. And I think part of the
[21:32] problem I have with gravitational
[21:35] waves is that whilst they had been
[21:37] predicted in a kind of niche way so long ago,
[21:39] the first observations were so recent that
[21:42] I wasn't taught about gravitational waves at
[21:44] uni. They weren't part of our courses. It's
[21:47] still really cutting edge new concepts.
[21:51] And so my understanding, therefore
[21:53] my explanation, it's woolly because I've
[21:56] never had it explained by someone who has had
[21:59] it explained by someone who's had it
[22:01] explained by someone. We've not had that
[22:03] buildup of conceptual
[22:05] description, I guess, to really embed this.
[22:08] And I find it really hard to get my head
[22:10] around the first observed gravitational wave,
[22:13] I think was 2015. This is a
[22:15] decade old. So it's probably like someone
[22:18] calling into the podcast in 1925
[22:20] asking me to explain general relativity.
[22:24] Andrew Dunkley: Yes. Yeah, that's a good analogy. Um,
[22:27] Dean, thanks for the question. Hope we, we
[22:29] covered all those little gaps you were
[22:30] talking about. Boom, boom. Uh, this is Space
[22:33] Nuts with Andrew Dunkley and Professor Johnty
[22:35] Horner. A, uh, Q A edition.
[22:39] Generic: I think we need to do a little more all
[22:41] weather testing.
[22:43] Andrew Dunkley: Amen, Space Nuts.
[22:45] Our next question comes
[22:48] from David.
[22:49] Andrew Dunkley: This is David from Port Washington, New York.
[22:53] And I was thinking back to when I was a
[22:55] teenager and I heard the recording of
[22:57] the resonant frequency of the universe and I
[23:00] thought it was very cool. I'm wondering if
[23:02] there was some kind of medium that sound
[23:05] could pass through in space, like, uh,
[23:08] water, uh, or even air.
[23:11] What would I be hearing? Uh, and would it be
[23:14] beautiful or would it be terrifying? What are
[23:17] the different resonant frequencies going on
[23:19] and big explosions?
[23:21] Generic: Really?
[23:21] Andrew Dunkley: Um, interested to know.
[23:23] Generic: Bonus.
[23:23] Andrew Dunkley: Um, question. If I could breathe in space,
[23:25] what would it smell like? But I'm more
[23:27] interested to know about the sounds. Okay,
[23:30] thanks guys.
[23:31] Andrew Dunkley: Thank you. David. I love this question. It's
[23:34] a little bit different. We haven't had uh,
[23:36] one like that for a while. Although I do
[23:38] recall we did talk about
[23:41] some time back about, um, I
[23:43] can't remember exactly what the object was,
[23:46] but they were talking about what it would
[23:48] smell like if you could smell it. And
[23:50] um, you know, and that was fascinating
[23:53] in itself. But don't ask me to remember what
[23:55] it was. I think it was rotten eggs.
[23:58] Andrew Dunkley: It is.
[23:58] Jonti Horner: I think that's a concept that's often used a
[24:00] bit like we talked about in the Last
[24:01] Questions episode about the raining diamonds
[24:04] and raining, um, precious gems,
[24:07] where people try to give you a
[24:10] hook that fits in with your day to day lived
[24:12] experience to help you visualise something
[24:14] more clearly. And the
[24:16] recording of the resonant frequency of the
[24:19] univers. It's another one of those. I think
[24:22] what we're talking about there is the
[24:23] microwave background, cosmic microwave
[24:25] background, which is this very low
[24:28] frequency now radio detection, um,
[24:31] equivalent to a black body at about 2.7
[24:34] Kelvin. That is a leftover hiss from
[24:37] the Big Bang, which, when Big bang happened
[24:40] about 300,000 years later, the universe went
[24:43] from being opaque to transparent. And all the
[24:45] radiation from the heat of the universe at
[24:47] that time went out into space. Universes
[24:49] got bigger, everything's got redshifted. So
[24:52] the peak of that spectrum now looks like a
[24:54] source. That was 2.7 Kelvin. And,
[24:56] um, that microwave
[24:59] background is the source of a lot of the
[25:01] static that you used to get if you tune your
[25:03] radio between stations or if you had an old
[25:05] TV where you had to tune in on the dial or
[25:07] move the antenna around and you just got the
[25:09] noise on the screen. A significant component
[25:12] of that was a macro background. And people
[25:14] have often tried to convert that into
[25:17] a sound to give people a kind of
[25:20] emotional connection, a way of visualising
[25:21] this. Um, although that's
[25:24] turning radio waves into a sound. Well, I
[25:27] guess we do that all the time with FM and AM
[25:29] broadcast, right?
[25:31] Andrew Dunkley: Yep.
[25:31] Jonti Horner: So, uh, it kind of makes sense to people in
[25:34] terms of what the universe would sound like.
[25:36] If there was a medium in space to transmit
[25:39] the sound, it would actually depend to some
[25:42] degree of the density of that medium as well.
[25:44] So the frequency that a given sound
[25:46] will sound like changes with
[25:49] atmospheric pressure. And I've seen examples
[25:52] of this where people have put an alarm bell,
[25:55] kind of alarm clock type, ringy bell noise
[25:58] in a big bell jar and evacuated the air
[26:01] from it. And as the air pressure got lower
[26:02] and lower, I think the pitch got higher and
[26:04] higher until the sound disappeared. So you've
[26:07] got a lot of different factors that would
[26:09] come into this to do with the composition
[26:12] of the medium, the density of the medium and
[26:14] stuff like that. But let's imagine just for a
[26:17] minute, because I think this is more of a
[26:18] science fiction question than a science fact
[26:21] one in a way. And I do love it as a question
[26:22] like that. If you were floating around in the
[26:25] solar system and you were uh, beyond the
[26:27] Earth's atmosphere, what would be the main
[26:30] source of noise that you'd experience?
[26:33] To me, I would actually guess the solar wind.
[26:35] Cause you have this flow of particles coming
[26:37] past you at a speed measured in hundreds of
[26:39] kilometres a second, 100, 200, 300 kilometres
[26:42] a second. So to me, I guess the main sound
[26:44] you would hear if you were beyond the Earth's
[26:46] atmosphere and there was enough medium for
[26:49] you to listen to, would actually be the sound
[26:51] of the wind blowing, but a really intense
[26:53] gale blowing. There have been
[26:56] discussions about what you'd hear on Mars.
[26:59] Now of course, on Mars the atmospheric
[27:01] pressure is much, much lower than even at the
[27:03] altitude of Everest. So that frequency
[27:06] shifting phenomenon would come in. So
[27:08] something that you'd hear as an ice deep bass
[27:10] note on Earth, I believe, would be a higher
[27:12] pitch on Mars quite markedly.
[27:14] Andrew Dunkley: Yeah.
[27:15] Jonti Horner: Darren Squeaky Y if you're listening
[27:18] to this podcast on Mars, please wear
[27:20] headphones. Otherwise I'll sound even more
[27:22] stupid than normal, I guess. Um,
[27:25] I would imagine that in terms
[27:28] of the concept of whether it would be
[27:30] beautiful or scary, I suspect it'd be like
[27:33] white noise with a lot of different
[27:35] components coming in. If you could visualise
[27:38] different astronomical phenomena
[27:39] contributing, a lot of them are time varying,
[27:42] a lot of them are bright flashes or
[27:45] whatever. So you'll probably have an
[27:47] underlying bass noise of whatever
[27:49] with lots of other things impinging on it.
[27:52] But it's really hard to say because we're
[27:54] trying to imagine a reality that is so, ah,
[27:56] different to our own. So I'm trying to find a
[27:59] way to contextualise that, I guess.
[28:01] Um, so it'd probably be a lot more like a
[28:04] white noise machine than something clear and
[28:07] beautiful. Possibly a white noise machine on
[28:09] a very windy day.
[28:11] Andrew Dunkley: Yeah. Sounds, um, in space, um,
[28:16] it's a difficult thing to try and get your
[28:18] head around because sound needs something to
[28:21] move through and space doesn't offer a lot of
[28:24] that.
[28:25] Jonti Horner: Absolutely. And I mean to maybe give you a
[28:28] different illustration of that. If you think
[28:29] about how sounds change when you go
[28:31] underwater, how different the world
[28:33] seems if you're snorkelling or you're doing a
[28:35] scuba Dive.
[28:36] Andrew Dunkley: Yeah.
[28:36] Jonti Horner: How all the sounds are so different to you.
[28:39] Andrew Dunkley: Yeah. I'll give you an example of sound
[28:42] and witnessing its movement. Uh, and this is
[28:45] not something I'd recommend, but, uh, we were
[28:48] standing on the rim of a volcano some years
[28:50] ago, and it was active and it was going
[28:54] in our faces. Actually, we had to leave
[28:56] because it was getting in our faces. Um,
[28:59] but watching the process of the eruption,
[29:02] you see it, it before
[29:05] you hear it, but you feel it
[29:09] also before you hear it, but not until after
[29:12] you see it.
[29:12] Andrew Dunkley: Yeah.
[29:13] Andrew Dunkley: So, uh, you see the explosion, you feel the
[29:16] rumble, and then you hear it, and
[29:19] then the shockwave hits you. Yeah, it's
[29:22] a really weird combination. And look, you're
[29:24] talking about a matter of
[29:27] all of this happening over in the course of
[29:29] about a second or a second, a half,
[29:32] depending on distance. But you see it, you
[29:35] feel it, you hear it,
[29:38] you feel it in the ground, and then you feel
[29:40] the shockwave.
[29:40] Andrew Dunkley: Yeah.
[29:41] Jonti Horner: And I mean, that fits in with how
[29:45] sound travels at different speeds. So what
[29:47] you feel under your feet is effectively waves
[29:49] that you'd probably hear as sound. But going
[29:52] through a solid medium, they travel faster.
[29:54] Andrew Dunkley: Exactly.
[29:55] Jonti Horner: Shockwaves are quicker. And I mean, that
[29:57] links in part to, uh, how we know so much
[29:59] about the interior of the Earth. Because
[30:01] shock waves from earthquakes travel at
[30:04] different speeds through different media. And
[30:06] you've got T waves and S waves
[30:08] propagating around the Earth. Ah, some going
[30:10] through the Earth's, uh, interior, being
[30:11] picked up at seismographs around the world
[30:14] that very clever people can use to reverse
[30:16] engineer what the interior structure of the
[30:18] Earth's like by those differences in speed.
[30:22] Andrew Dunkley: Yeah, it was a strange experience.
[30:25] And that was the last thing I expected to
[30:27] witness. I was a bit more concerned about
[30:30] what was falling out of the sky at the time.
[30:33] I'll tell you, though, um, I took a great
[30:35] photo as we were walking off.
[30:37] Uh, when you're in tour groups, there's
[30:39] always a straggler. So we're all halfway off
[30:41] the mountain, but someone decided to stay
[30:44] behind. And that's when the biggest bang of
[30:47] the day happened. And it flung lava bombs up
[30:50] in the sky the size of soccer balls.
[30:53] And I had already put my camera in my
[30:55] pocket. I, uh, turned it off. I had enough
[30:57] time to pull the camera out, turn it on
[31:01] focus, and take a photo of this woman staring
[31:03] up at lava bombs coming down.
[31:06] It's a great photo. Um, and then it was,
[31:09] uh, only a few weeks after I got home that my
[31:11] friend, uh, sent me a video that he'd Taken
[31:15] of one of those, uh, little eruptions and
[31:18] I didn't see it, but there was a lava bomb
[31:20] landed 20 metres in front of me. I never even
[31:23] saw it. And, yeah, that kind
[31:26] of freaked me out after the fact.
[31:29] Yeah, like I said, not something I recommend,
[31:32] but, boy, what an adrenaline jolt.
[31:36] Yeah, but there's a few
[31:38] volcanoes we've visited over the years and,
[31:41] um, they've all blown up since we've been to
[31:43] them. So the one at Vanuatu stopped air
[31:45] traffic. Uh, we were at Matt Etna,
[31:49] uh, a couple of years ago. Well, look what
[31:50] it's doing at the moment. Kilauea. It's gone
[31:53] off, like, several times since we were there.
[31:55] In fact, the observation deck in the
[31:58] caldera, uh, where we
[32:01] looked at Kilauea, was
[32:03] obliterated about a month after we were
[32:06] there.
[32:08] Jonti Horner: So when are you taking a holiday to Naples or
[32:10] to Yelliston?
[32:11] Andrew Dunkley: Well, actually, we've been to Naples, so,
[32:14] um, it wasn't, um,
[32:17] Vesuvius, though, that went off when we were
[32:19] there. It was, um, Stromboli.
[32:21] Jonti Horner: Yeah, well, they're quite worried about Campo
[32:23] Fiegri, I think it's called, which is Big
[32:26] Field under Naples. That, yes, will
[32:29] be a disaster when it goes.
[32:31] Andrew Dunkley: Well, like, if you go out
[32:33] into the. Into the bay and, and
[32:36] do a bit of, um, skin diving down to the. To
[32:39] the bottom, there's all this gas coming up
[32:41] through the sand, like.
[32:43] Jonti Horner: And I keep seeing reports of the amount of
[32:45] swelling of the lava dome and things like
[32:47] this. I mean, yeah, I personally would not
[32:49] feel all that comfortable living in that area
[32:51] or even necessarily visiting,
[32:55] but hopefully, you know, it will not be a
[32:57] problem within our lifetimes and the science
[32:59] will continue to improve to the level that
[33:01] they get enough warning to get everybody out
[33:03] when it goes.
[33:04] Andrew Dunkley: Yeah, that's the problem, isn't it? Uh, and
[33:06] even in, uh, New Zealand they've got, um, the
[33:10] dormant, uh, volcano in the
[33:12] harbour at Auckland. And
[33:16] I was talking to a journalist friend of mine
[33:18] who lived in New Zealand, uh, some years ago
[33:21] when I worked for the abc, and he was saying,
[33:23] look, it is a worry there too, if this thing
[33:26] ever wakes up. There are only two roads out
[33:28] of Wellington, uh, out of Auckland,
[33:31] and you've got a million people there or
[33:34] something. And how are they going to get
[33:37] out?
[33:37] Jonti Horner: It was actually fascinating. I was in New
[33:39] Zealand a couple of times earlier in the year
[33:41] and went through Auckland and spotted all
[33:43] these little humps and thought, that's
[33:44] interesting. Looked into it. I just pulled up
[33:46] the information here. The metropolitan area
[33:49] of Auckland contains 53
[33:51] volcanoes because it's a little volcanic
[33:54] field of these small little
[33:57] maas and tuff rings and all this stuff.
[34:01] Um, none of them are thought to have erupted
[34:03] more than once, except for one of them called
[34:06] Orangitoto. But it is
[34:09] an active volcanic area. Apparently the first
[34:10] vent in that area erupted 193,000
[34:13] years ago. And the most recent one was about
[34:15] 600 years ago.
[34:16] Generic: Go.
[34:17] Andrew Dunkley: Yeah.
[34:18] Jonti Horner: Um, and that's from the one in the water,
[34:20] um, just east of the city. But,
[34:23] yeah, must be a fascinating place to live.
[34:25] But that plus the earthquakes,
[34:29] plus the psalms that get there. It's
[34:31] good to live in interesting times. But that
[34:33] might be a little bit too full on.
[34:35] Andrew Dunkley: Yeah. Well, we visited Christchurch,
[34:38] uh, coming up on four
[34:41] years ago now, and, uh, it had had that
[34:43] massive earthquake, that tragic earthquake.
[34:46] And, uh, even then you could. That
[34:49] they hadn't come close to rebuilding.
[34:52] And they even have, um, a
[34:55] museum, Quake City, I think it's called In
[34:58] Christchurch, which I highly recommend. It's
[35:00] fascinating. Yeah.
[35:02] Uh, we got off the topic, uh, did we talk
[35:04] about smells in space? If you could take a
[35:06] big inhale, what would it be like?
[35:08] Andrew Dunkley: I'm not sure.
[35:09] Jonti Horner: I mean, this is one of those things that
[35:11] people use to give you a handle
[35:14] to get on. So when we discover interesting
[35:17] things in the atmosphere of different places,
[35:20] usually, um, the things that relate to
[35:23] gases that we'd have on Earth are used to
[35:25] say, oh, this place would smell of whatever.
[35:27] Most common of them is hydrogen sulphide,
[35:29] which is your rotten egg smell, which is why
[35:32] people talk so much about exoplanets that
[35:34] smell like rotten eggs. But I think there was
[35:37] one recently that wasn't there. Something
[35:40] saying it was a giant gas cloud that would
[35:41] have smelled or tasted of strawberries. Big
[35:44] Said found a long chain hydrocarbon that was
[35:47] part of the test sensation. That is a nice,
[35:49] nice strawberry. So I think most of space
[35:52] would not smell particularly pleasant, but
[35:55] you wouldn't smell very much. But there's
[35:57] dust and debris around. But there's also a
[35:58] lot of gases that you really wouldn't want to
[36:00] inhale. I mean, I'm thinking of hydrogen
[36:02] cyanide and things like this. So, uh,
[36:05] inhale at your own risk.
[36:07] Andrew Dunkley: Well, I think you'd only inhale once in space
[36:09] and that'd be the end of that.
[36:10] Jonti Horner: Oh, absolutely, absolutely.
[36:11] Generic: Probably. All right.
[36:13] Andrew Dunkley: Uh, David, thanks for that. Great question.
[36:14] That was a lot of fun to discuss and brought
[36:16] up a lot of things in my mind about some of
[36:18] the experiences with sounds and smells I've
[36:21] had in my life.
[36:22] Uh, and that brings us to the end of a Q and
[36:24] A edition. If you would like to send us some
[36:26] questions, please do through our website
[36:28] spacenutspodcast.com spacenuts
[36:31] IO or do a search for SpaceNuts
[36:33] podcast in your favourite search engine. If
[36:36] you just do a search for Space Nuts, it'll
[36:37] take you to that horrible movie.
[36:40] Um, well, it's probably not that horrible,
[36:43] but anyway, uh, that's how you do it. Just
[36:45] click on the AMA tab and send us text or
[36:47] audio questions. And don't forget to tell us
[36:49] who you are and where you're from. And have a
[36:51] look around on our website while you're
[36:52] there. Jonty, thanks very much. Good to see
[36:54] you again.
[36:55] Jonti Horner: That's absolute pleasure. It's good to catch
[36:56] up and, you know, I'll catch you again the
[36:58] next time Fred Watson's on a jolt.
[36:59] Andrew Dunkley: Yeah, I think you'll be back after this
[37:01] episode, but we'll, um, we'll keep you on
[37:03] standby, but we'll talk again down the track.
[37:06] Jonti Horner: Absolutely.
[37:06] Andrew Dunkley: Look forward to it, Professor Jonty Horner,
[37:09] professor of Astrophysics at the University
[37:10] of Southern Queensland. And thanks to Huw in
[37:12] the studio, uh, who did actually turn up
[37:15] today, but they wouldn't let him in because
[37:16] he smells. And from me, Andrew Dunkley.
[37:19] Thanks for your company. We'll see you on the
[37:20] next episode of Space Nuts. Bye. Bye.
[37:24] You've been listening to the Space Nuts
[37:26] Jonti Horner: podcast, available at
[37:29] Apple Podcasts, Spotify,
[37:31] iHeartRadio or your favourite podcast
[37:34] player. You can also stream on
[37:36] demand@bytes.com.
[37:38] Andrew Dunkley: this has been another quality podcast
[37:40] production from bytes.um com.

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