Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Waves, Signals, and Cosmic Aromas: A Q&A Journey Through Space

Transcript

Waves, Signals, and Cosmic Aromas: A Q&A Journey Through Space · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 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.