Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Nuclear Power in Space, SETI from the Moon & the Hubble Tension Unravelled

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Nuclear Power in Space, SETI from the Moon & the Hubble Tension Unravelled · Space Nuts: Astronomy Insights & Cosmic Discoveries

• 0:00
  Andrew Dunkley: Hello again. Thank you for joining us. This
• 0:02
  is Space Nuts. My name is Andrew
• 0:05
  Dunkley. If you've never heard of Space Nuts,
• 0:07
  where have you been for the last 10 years?
• 0:09
  Good, uh, to have you along if you're a first
• 0:11
  timer. And everybody else who's been with us
• 0:13
  for aeons. Uh, today
• 0:16
  on the show we will be talking about,
• 0:18
  uh, a. Ah, really interesting and some
• 0:21
  might think scary development, nuclear
• 0:24
  space policies. I don't think they're talking
• 0:27
  about, you know, weapons of mass destruction,
• 0:30
  but they are talking about power supply
• 0:32
  systems. We're, uh, also going to look at
• 0:34
  SETI from the far side of the moon because,
• 0:37
  uh, that's the best place to listen for alien
• 0:40
  civilizations because, well, Earth is very
• 0:43
  noisy. But the far side of the moon,
• 0:46
  you can't hear a thing. Except the aliens,
• 0:49
  apparently. And. Oh, uh, no. The
• 0:52
  Hubble tension debate is simmering
• 0:54
  again. We'll get into all of that on, on
• 0:56
  this, uh, this episode of space
• 0:59
  nuts.
• 1:00
  Generic: 15 seconds. Guidance is internal.
• 1:03
  10, 9. Ignition
• 1:06
  sequence start.
• 1:07
  Professor Fred Watson: Space nuts.
• 1:08
  Generic: 5, 4, 3, 2. 1. 2, 3, 4,
• 1:10
  5, 5, 4, 3, 2, 1.
• 1:13
  Andrew Dunkley: Space nuts.
• 1:14
  Generic: Astronauts report it feels good.
• 1:17
  Andrew Dunkley: And joining us to nuke a few storeys is
• 1:19
  Professor Fred Watson Watson, uh, astronomer
• 1:21
  at large. Hello, Fred Watson.
• 1:23
  Professor Fred Watson: Hello, Andrew. Lovely to hear, uh, your
• 1:26
  voice and see your face.
• 1:28
  Andrew Dunkley: Yes, my voice is still a little bit down
• 1:31
  like that. Could do an Elvis song as a
• 1:33
  backing.
• 1:34
  Professor Fred Watson: Oh, you could, yeah, yeah, Way on, just down.
• 1:37
  Well, we. So at the end of the show, you
• 1:39
  definitely need to say thank you very much.
• 1:42
  Andrew Dunkley: Thank you very much. Uh, yes,
• 1:44
  that's what happens when I get a cold. My
• 1:46
  voice just goes down deep. When I first
• 1:49
  started in radio, I did midnight to dawns. In
• 1:51
  the days where they didn't automate it,
• 1:53
  everything, everything was live.
• 1:56
  And around four in the morning when I used to
• 1:58
  get really, really tired, my voice would just
• 2:01
  naturally go down there and.
• 2:05
  And it was really weird because, um,
• 2:07
  it wasn't my natural voice. But,
• 2:10
  um, at the moment it's. It's enjoying that
• 2:12
  part of the spectrum.
• 2:14
  Professor Fred Watson: So, m. Yes.
• 2:16
  Andrew Dunkley: Hopefully it'll get better soon. I don't like
• 2:18
  the feeling, I must say.
• 2:19
  Professor Fred Watson: No, you wouldn't.
• 2:20
  Andrew Dunkley: Anyway, we battle on, don't we?
• 2:22
  Professor Fred Watson: No point getting all that's. You know,
• 2:25
  we do in Space Nuts. We come rain or shine
• 2:28
  or absence or whatever, we keep going. We do.
• 2:31
  Andrew Dunkley: Speaking of battling on nuclear energy,
• 2:36
  uh, this. This is a policy that's just been
• 2:39
  announced by the Pentagon and the Department
• 2:42
  of Energy and they've kind of dragged NASA
• 2:44
  into it. They said, hey, NASA,
• 2:47
  we want you to build us a couple of power
• 2:49
  stations and they've got to be nuclear and
• 2:50
  they've got to be ready by 2028. How about
• 2:53
  it?
• 2:54
  Professor Fred Watson: Yeah, that's more or less it.
• 2:57
  It's a six page policy document.
• 3:00
  Uh, its title is NSTM
• 3:03
  M3. Uh, which is
• 3:06
  to direct a parallel and mutually
• 3:09
  reinforcing design, uh, set of design
• 3:11
  competitions by NASA and the Defence
• 3:14
  Department to enable, and I'm quoting here,
• 3:16
  to enable near term demonstration and use of
• 3:19
  mid power space reactors in orbit and on the
• 3:22
  lunar surface and prepare to deploy
• 3:25
  high power reactors in the 2000 and 30s.
• 3:28
  Uh, I'm quoting here from uh,
• 3:31
  people who are closely involved with this.
• 3:33
  For this to work it has to be a collaboration
• 3:36
  between multiple government agencies. Well
• 3:39
  that's a novel idea, isn't it? Yeah,
• 3:41
  um, that's the way that work.
• 3:44
  Yeah, that's the way that we do the right R
• 3:47
  D and get the right tools in place for these
• 3:49
  events to unfold over the next few years.
• 3:51
  Yeah. Yes. So um, that's right. So the
• 3:54
  bottom line is NASA is
• 3:57
  directed to start work within
• 3:59
  30 days on a mid power space
• 4:02
  reactor generating at least 20 kilowatts of
• 4:05
  power with a variant that can operate on the
• 4:07
  lunar surface. He calls for the
• 4:09
  agency to work with multiple companies on
• 4:11
  reactor designs including for a low power
• 4:13
  system that produces as little as 1 kilowatt
• 4:16
  if doing so offers lower cost and schedule
• 4:19
  risk. And this is um, it's a White House
• 4:22
  release, uh, that I'm quot from here. So
• 4:24
  it's, it's definitely the official thing.
• 4:26
  Yeah. Wow.
• 4:27
  Andrew Dunkley: Should we be surprised by this though?
• 4:29
  Professor Fred Watson: Uh no, no we shouldn't. I mean actually
• 4:32
  we did get um. Was it Jared Isaacman, the
• 4:35
  uh, the new, relatively new head of
• 4:38
  NASA, who I think we covered this uh,
• 4:41
  quite a few months ago, talked about the idea
• 4:44
  of uh, using a uh, 100 kilowatt
• 4:47
  nuclear reactor on the lunar surface. Because
• 4:49
  that raises a few eyebrows. Uh, but it looks
• 4:51
  as though this is the first step in, in
• 4:55
  expediting that uh, to start small,
• 4:58
  maybe even the smallest 1kW it'll run an
• 5:01
  electric fire and uh,
• 5:04
  keep um, going upwards. Uh, there's an
• 5:07
  interesting uh, disparity in
• 5:10
  the sort of urgency of this though because
• 5:12
  um, the next paragraph of the White House
• 5:15
  release says the policy calls on the Defence
• 5:17
  Department to provide a briefing to the
• 5:20
  White House in 90 days on um, potential
• 5:23
  uses and payloads for space nuclear systems
• 5:26
  of varying power levels. The Pentagon will in
• 5:28
  the first year of the policy use its space
• 5:30
  nuclear funding to support NASA's efforts,
• 5:33
  then conduct its own competition for space
• 5:35
  nuclear power systems. I get the feeling here
• 5:38
  that there's going to be too many fingers in
• 5:40
  the pie and too many people deciding which
• 5:43
  companies are going to get the, you know,
• 5:45
  going to get the contracts to do this.
• 5:48
  Andrew Dunkley: The options for nuclear power these days
• 5:51
  are so much more,
• 5:54
  uh, available and simple. Like
• 5:56
  you can make very small nuclear power
• 5:59
  stations now. You can, you can build one
• 6:03
  that's, that's small enough just to service a
• 6:05
  town these days. You don't need these big
• 6:08
  complex setups anymore.
• 6:11
  So it probably is the logical way to go.
• 6:14
  Even though when you say the word nuclear,
• 6:16
  everybody sort of runs for the hills. Not
• 6:18
  that that would save them, but um,
• 6:21
  it's not, ah, as big and scary as people
• 6:25
  envisage. But um, it's, it's got bad
• 6:28
  press for a long, long time. So whenever you
• 6:30
  talk about nuclear power station or look what
• 6:32
  happened in Australia, um, we're so
• 6:35
  scared of it. We've never done it.
• 6:38
  Professor Fred Watson: And people think of Three Mile, Three Mile
• 6:40
  island in Chernobyl.
• 6:43
  Uh, and uh, yes. And the bottom line
• 6:46
  is that if things go wrong, you have a very
• 6:48
  big environmental problem. And uh, that would
• 6:51
  be the case.
• 6:52
  Andrew Dunkley: It's fukush.
• 6:53
  Professor Fred Watson: Yeah.
• 6:53
  Andrew Dunkley: With the earthquake and the tide and the
• 6:56
  tsunami. Yeah, that's so mess.
• 6:59
  Professor Fred Watson: Yes. So, uh, it is scary, I
• 7:02
  think. Um, but, but
• 7:05
  well, so I grew up in a country that, uh,
• 7:08
  pioneered nuclear power with the US
• 7:11
  and there are several nuclear power stations.
• 7:14
  Uh, I used to live not very far from one
• 7:15
  actually at uh, Torness in Scotland.
• 7:20
  Yes, I think it's Taunus. Uh, and
• 7:23
  look, everybody just regarded it as
• 7:26
  a normal power station. It was very much a
• 7:29
  low key thing. Uh, and you
• 7:32
  see statistics like there's more
• 7:35
  radiation comes from the natural emissions
• 7:38
  from rocks in the uk. If you go down to
• 7:40
  Cornwall, the rocks are basically radioactive
• 7:43
  there.
• 7:43
  Andrew Dunkley: Oh wow.
• 7:44
  Professor Fred Watson: There's radon in the atmosphere. Um, but it's
• 7:47
  at a level that humans can tolerate. Humans
• 7:49
  have been tolerating it for hundreds of
• 7:52
  thousands of years. And uh, that's.
• 7:54
  Andrew Dunkley: Yeah, you're exposed to radiation every time
• 7:57
  you walk outside.
• 7:58
  Professor Fred Watson: Well, that's right, you are. Yes. So, um, so
• 8:01
  it, it's got to be treated with respect.
• 8:04
  Um, I, I think what freaks people out
• 8:07
  though as well is the idea of sticking a
• 8:10
  nuclear reactor on top of a rocket and then
• 8:13
  sending it into space. And there was an
• 8:15
  accident, uh, with a. So just
• 8:18
  stepping back, uh, NAS, their
• 8:21
  RTGs, radioisotope
• 8:24
  thermal generator, thermoelectric generators,
• 8:27
  I think that's what it stands for. Uh, on
• 8:29
  several spacecraft, including the two
• 8:31
  Voyagers, I think the pioneers have got it as
• 8:34
  well. Um, the Curiosity, um,
• 8:38
  and um, Perseverance.
• 8:40
  Both have RTG power supplies. Uh,
• 8:43
  so that's uh, uh,
• 8:46
  a well trodden path. But there was an
• 8:49
  accident, I think it might have been in the
• 8:50
  80s with a spacecraft that was launched with
• 8:53
  something like an RTG on board and it did,
• 8:56
  uh, it went wrong. I can't remember
• 8:59
  the details but I think it was Canada that
• 9:01
  took the punch. And there was a lot of
• 9:04
  radioactive debris that got spread over
• 9:07
  very, very sparsely, uh,
• 9:10
  populated regions. Uh,
• 9:12
  literal fallout. Yes, that's right. Yes,
• 9:15
  exactly. Flaws out the sky. If I remember
• 9:18
  rightly. I'm digging up things from the past
• 9:20
  year, but I think that's the case and that
• 9:22
  clearly freaks people out. If you've got a
• 9:24
  launch that doesn't work, uh, what's going to
• 9:27
  happen?
• 9:28
  Andrew Dunkley: I imagine so. But uh, it certainly does ramp
• 9:31
  up the space race between the US and China.
• 9:33
  And you know, China's probably going to fall
• 9:35
  a bit behind here because I think they were
• 9:37
  trying to set up a coal fired power station
• 9:39
  on the moon. You know, it
• 9:40
  um, might m, might
• 9:43
  slow them down a bit.
• 9:44
  Professor Fred Watson: Yeah, China's doing pretty well. They are
• 9:46
  doing sustainability. Yeah, yeah, they are.
• 9:49
  Ah, but yeah, they do use a lot of coal
• 9:51
  still.
• 9:51
  Andrew Dunkley: Yeah, they do, they do. So this is probably
• 9:54
  going to happen and what other
• 9:57
  option would there be? That's the thing. I
• 9:59
  mean some people will say no, put up solar
• 10:01
  energy systems, but um,
• 10:04
  nuclear is probably a much more
• 10:06
  efficient way of doing it.
• 10:08
  Professor Fred Watson: Yeah, well for a start, you've got the
• 10:10
  baseline load. You're not worried about where
• 10:12
  the sun is in the sky. The idea
• 10:15
  of being at the south pole of the moon,
• 10:19
  which is where the focus is in terms
• 10:21
  of our uh, exploration of the moon.
• 10:24
  Uh, it puts a different slant
• 10:27
  on it because it means that you are looking
• 10:30
  at a very low sun altitude in the
• 10:33
  sky. Uh, the sun's coming in nearly
• 10:35
  horizontally. The sunlight, now that's not
• 10:38
  uh, as bad a thing on the moon as it would be
• 10:41
  on the Earth. The Earth, as the sun gets
• 10:43
  lower, it's going through a thicker and
• 10:44
  thicker layer of atmosphere. So its uh, power
• 10:47
  is attenuated. On the moon that doesn't
• 10:50
  happen because there ain't no atmosphere. But
• 10:52
  it does bring challenges for your solar
• 10:55
  panels. You know, you've got to build arrays
• 10:56
  that are almost vertical and if you're
• 10:58
  looking for a big structure, uh, then
• 11:01
  uh, it becomes different slightly different
• 11:04
  engineering, um, issue. Plus you've got to
• 11:07
  take all that stuff up there as well. You
• 11:09
  know, going up to the moon with arrays of
• 11:12
  solar panels in the spacecraft might not
• 11:14
  leave room for much else. Whereas a nuclear
• 11:16
  reactor of the kind that people are talking
• 11:18
  about would be relatively compact. I m mean,
• 11:20
  the RTG devices are, I think
• 11:23
  it's, is it 13 kilogrammes of, uh,
• 11:26
  plutonium that they have in them.
• 11:29
  They're about the size of a, you know,
• 11:32
  a tea urn or something like that. Or a drink
• 11:35
  serum. Yeah, yeah.
• 11:37
  Andrew Dunkley: It's much simpler than it was 20, 30,
• 11:40
  40, 50 years ago. And of course they're
• 11:43
  talking not only about the moon, but people,
• 11:45
  uh, on Mars, uh, they'll need power as well.
• 11:48
  Um, I know in the movie the Martian they used
• 11:50
  solar panels, but that Mars is a bit further
• 11:52
  away, so the solar panels probably wouldn't
• 11:54
  be as efficient.
• 11:55
  Professor Fred Watson: Exactly.
• 11:57
  Andrew Dunkley: Nuclear, um, power makes, Makes perfect
• 11:59
  sense. Uh, although, you know, solar energy
• 12:02
  is quite, um, well used
• 12:05
  in space. Artemis 2 used it.
• 12:09
  Professor Fred Watson: Um, that's correct, yes. Uh, and
• 12:11
  um, you know, thinking of the different
• 12:13
  spacecraft, the one that's got perhaps the
• 12:15
  most spectacular solar panels is Lucy, uh,
• 12:18
  spacecraft which is on its way to the Trojan
• 12:20
  asteroids. Uh, and that's got
• 12:23
  solar panels which are huge. And that's
• 12:26
  because you're going out to the asteroid belt
• 12:28
  and beyond. Actually you go into the orbit of
• 12:30
  Jupiter, which is where the Trojan asteroids
• 12:32
  hang out. Uh, so you need big solar
• 12:35
  panels to collect all the energy. Yeah.
• 12:37
  Andrew Dunkley: The other problem with solar panels on Mars
• 12:39
  would be dust, because it's
• 12:42
  a pretty grubby place.
• 12:43
  Professor Fred Watson: Yeah, that's what, um, probably brought an
• 12:46
  end to. Uh, so Spirit and Opportunity both
• 12:49
  had solar panels. Uh, and there were
• 12:52
  certainly times when the amount of dust was
• 12:55
  stopping the power generation. And uh, that
• 12:57
  was cleared by, uh, Willy Willies, as they're
• 13:00
  called. Uh, the um, dust
• 13:03
  devils. That's right. On Mars. Yeah.
• 13:05
  Andrew Dunkley: Fascinating.
• 13:05
  All right, so the um, the directive has
• 13:08
  been put to NASA to start working on this,
• 13:11
  uh, and it comes from the White House. So,
• 13:14
  um, it's all systems go and they hope to have
• 13:16
  something operational as soon as 20,
• 13:19
  28. So they're not mucking around. In fact, I
• 13:22
  think NASA, after this was released, were
• 13:24
  given one month to it.
• 13:26
  Professor Fred Watson: Uh, that's, uh, exactly right. That's the 30
• 13:28
  days that I mentioned.
• 13:29
  Andrew Dunkley: No mucking around.
• 13:30
  Professor Fred Watson: Get going.
• 13:31
  Andrew Dunkley: Yep. Uh, you can read all about
• 13:33
  it@spacenews.com.
• 13:36
  this is Space Nuts with Andrew Dunkley and
• 13:38
  Professor Fred Watson Watson.
• 13:44
  Space Nuts.
• 13:46
  Well, we mentioned the moon. We'll stick with
• 13:48
  the moon. This storey though has nothing to
• 13:51
  do with people on the moon. It's got uh,
• 13:53
  everything to do with people that are not on
• 13:56
  Earth or the Moon or, or Mars for that
• 13:58
  matter. Uh, they're out there somewhere.
• 14:00
  We're looking for them. We're talking about
• 14:02
  the search for extraterrestrial intelligence
• 14:05
  and the dark side of the moon. The far side
• 14:07
  of the moon is um, the best place
• 14:10
  to start looking.
• 14:13
  Professor Fred Watson: Uh, that's right. So we've been looking for
• 14:15
  this for 60 years
• 14:18
  and using ground, uh, based
• 14:21
  antennas here on planet Earth, uh,
• 14:24
  which are very, uh, very capable.
• 14:28
  Um, once the Square Kilometre Array
• 14:30
  Observatory comes on stream towards the end
• 14:32
  of the decade, uh, we'll have the
• 14:34
  finest, most capable radio
• 14:37
  telescope in the world, uh, which will not
• 14:40
  directly engage with SETI programmes, but
• 14:43
  it will uh, have the
• 14:46
  sensitivity to detect. Well the thing that
• 14:49
  my colleagues tell me is it'll detect an
• 14:51
  airport radar at 50 light years.
• 14:54
  So that's the kind of sensitivity
• 14:57
  uh, that you're talking about. Um, but
• 15:00
  the main problem with ground based, with
• 15:02
  Earth based uh, radio telescopes
• 15:05
  is that they're compromised by all the
• 15:07
  cacophony of radio signals that
• 15:10
  surrounds us. From your mobile phones, from
• 15:12
  broadcasts from people like you and
• 15:15
  me doing this, going out into the ether,
• 15:18
  WI fi routers, WI fi, uh, the whole thing,
• 15:21
  microwave ovens, it all provides this
• 15:23
  noisy radio background and that's not getting
• 15:26
  any better with the um, satellite mega
• 15:29
  constellations. Uh, I was in uh, a meeting
• 15:32
  yesterday. It's
• 15:35
  a meeting of the um, International
• 15:37
  Astronomical Union Centre, uh, for the
• 15:40
  protection of the dark and quiet sky from
• 15:43
  satellite interference. Uh, and it
• 15:45
  was um, you know one of the things that's
• 15:48
  raising anxiety is the idea of uh, Elon
• 15:51
  Musk's million satellites for
• 15:55
  um, orbital data centres and
• 15:57
  this mirror in the sky idea, sunlight on
• 16:00
  demand, that also has a million satel mirrors
• 16:02
  on it. So that's more for the optical
• 16:05
  astronomers. But it's all a concern,
• 16:07
  uh, and it basically is eroding our
• 16:10
  capability slowly but surely to
• 16:13
  detect uh, faint extraterrestrial
• 16:16
  signals. Uh, so that
• 16:18
  brings us to currently possibly
• 16:21
  the best place to do this sort of thing from
• 16:25
  which is the far side of the moon.
• 16:28
  Uh, and um, uh,
• 16:31
  we have one uh, spacecraft.
• 16:34
  By we, I mean humankind have one
• 16:36
  spacecraft on the far side of the moon. Uh,
• 16:39
  it is China's Chang' e 4,
• 16:41
  uh, which soft landed on the far side of the
• 16:44
  moon back in 2019. Can you believe it?
• 16:47
  It's been there uh, seven
• 16:50
  years. It's quite Extraordinary. Um,
• 16:53
  but uh, now that, that
• 16:56
  um. Spacecraft was not set up
• 16:58
  uh specifically for uh,
• 17:01
  looking for um, SETI search for
• 17:04
  extraterrestrial intelligence but
• 17:07
  it's got a low frequency radio
• 17:09
  spectrometer on board um that
• 17:12
  actually has been used to conduct the first
• 17:15
  ever SETI search from the lunar far
• 17:18
  side. Um and so the
• 17:21
  goal, uh, the idea
• 17:24
  is to use that equipment which is
• 17:26
  designed to do natural sciences
• 17:29
  but to look for those
• 17:32
  ah, technosignatures, uh
• 17:35
  technomarkers they're sometimes called, uh,
• 17:38
  which might suggest that you're getting a
• 17:40
  signal from an artificially generated
• 17:43
  source. And what you're really looking for
• 17:46
  are ah, periodic
• 17:49
  um, bursts of radiation with perhaps
• 17:52
  regular intervals
• 17:54
  um, that are not easily explained
• 17:57
  by natural processes. And you've got to
• 18:00
  think back to Jocelyn Bell Burnell and her
• 18:04
  discovery uh, of the first pulsar because
• 18:06
  that's what she saw. Narrow um, band.
• 18:09
  Um. Sorry, narrow uh, band
• 18:12
  in time signatures, uh, or
• 18:14
  bursts of radiation which we now know is the
• 18:17
  pulsar, the kind of light ass beam of
• 18:19
  radiation from the pulsar sweeping around and
• 18:22
  passing the earth. Um, she didn't know that
• 18:25
  then. So she wrote little green men in her
• 18:27
  uh. On her chart record of very,
• 18:30
  very famous words. Um,
• 18:33
  so that's what basically uh, the uh,
• 18:36
  Chang', E, um Low Frequency Radio
• 18:39
  Spectrometer has been looking for. Uh, and
• 18:41
  it's things that um, you know, that speak
• 18:44
  of an artificial generated source.
• 18:47
  And so um, what they've
• 18:50
  done, uh the scientists working on this,
• 18:52
  uh basically they built an algorithm
• 18:56
  uh that ah, uh trawled through the data
• 18:59
  looking for anything that might
• 19:02
  be artificial. With no
• 19:05
  credible candidates revealed,
• 19:08
  uh, nothing that couldn't be explained either
• 19:11
  by you know, natural phenomena or by
• 19:14
  instrument, uh, issues.
• 19:17
  Um, there's a nice comment though
• 19:20
  from uh, phys.org who is carrying this
• 19:22
  storey. Uh, this is,
• 19:25
  I'll quote this. This is not a failure, it is
• 19:28
  a beginning. As Carl Sagan once put it,
• 19:30
  absence of evidence is not evidence of
• 19:33
  absence. Brilliant. Really good point.
• 19:36
  Andrew Dunkley: I had a lot of time for Carl Sagan, uh, very
• 19:39
  wise man and um. Yeah, he uh, he did a lot
• 19:42
  for astronomy during his time. But um,
• 19:45
  that's a valid point and, and I suppose you
• 19:48
  and I have spoken about it in the past. The
• 19:50
  big problem is distance. There might,
• 19:53
  there might be civilizations out there that
• 19:55
  are advanced and capable of communication but
• 19:58
  they're so far away we will never hear from
• 20:00
  them. Maybe that.
• 20:02
  Professor Fred Watson: Yeah, um, that's right. Uh,
• 20:04
  and you know, and time is the other issue.
• 20:07
  It's a needle in A haystack both in distance
• 20:09
  and in time because you've got to hit your
• 20:11
  civil station just at the right time. Yes.
• 20:15
  Uh, when uh, they are uh, technologically
• 20:17
  enough to have airport radar, uh, for
• 20:19
  example, but haven't wiped themselves out
• 20:22
  because of the loonies that they've
• 20:23
  generated.
• 20:24
  Andrew Dunkley: Yeah, you're more, you're more likely to get
• 20:26
  a um, a tick tock of some
• 20:29
  kid doing a stupid raps hole. That's
• 20:31
  probably, that's what you'll get from,
• 20:35
  from an extraterrestrial intelligence, um.
• 20:38
  What, what, what I wonder
• 20:40
  is with the far side of the moon? Yes, it's
• 20:43
  radio silent, but does it cover enough
• 20:45
  of the spectrum of the universe to
• 20:48
  pick up something or is it fairly
• 20:51
  narrow in its scope?
• 20:53
  Professor Fred Watson: Do you mean in terms of direction or.
• 20:56
  Andrew Dunkley: Yeah, being able to pick something up.
• 20:58
  Professor Fred Watson: Has it got like a wide array? Yeah, I mean
• 21:00
  the far side of the moon, um, you know,
• 21:03
  if you plunk something on the equator of the
• 21:06
  moon on the far side over a month
• 21:08
  you cover the entire sky. If you're,
• 21:11
  yeah, if you're um, if your
• 21:14
  uh, equipment is broadband enough
• 21:17
  and all the SETI stuff is, it's got a very
• 21:20
  wide range of spectral, of uh, frequencies
• 21:22
  although they do tend to concentrate on
• 21:26
  what uh, we call the 21 centimetre line. This
• 21:29
  is the frequency, the specific frequency
• 21:32
  that's radiated by called hydrogen.
• 21:34
  Uh and they do tend to concentrate on that
• 21:37
  because everybody in the universe will be
• 21:39
  aware of that 21 centimetre
• 21:42
  uh, wavelength because
• 21:44
  that's called hydrogen. Which is the same
• 21:47
  everywhere.
• 21:48
  Andrew Dunkley: Yeah, makes sense. All right,
• 21:51
  fascinating. Um, storey, um, nothing yet.
• 21:54
  But that doesn't mean, that doesn't mean
• 21:56
  it'll always be nothing.
• 21:57
  Professor Fred Watson: So it's not evidence of
• 22:00
  absence. That's right.
• 22:01
  Andrew Dunkley: M exactly. You can read all about it as
• 22:04
  Fred Watson said at the phys
• 22:06
  phys.org website,
• 22:08
  this is Space Nuts Andrew Dunkley here with
• 22:11
  Professor Fred Watson Watson.
• 22:15
  Professor Fred Watson: Okay, we checked all four systems and
• 22:17
  Andrew Dunkley: being with a go, Space Nuts, our uh,
• 22:19
  final storey. Fred Watson brings uh, us back
• 22:22
  to that old debate about the Hubble
• 22:25
  tension. Now the Hubble tension is measured
• 22:28
  in two different ways and they come up with
• 22:30
  two different answers. And that's troubled
• 22:33
  people for a while. Although we did a storey
• 22:36
  not so long ago that suggested. Hang on a
• 22:38
  minute, the differences aren't uh, that
• 22:40
  significant. So they're probably both right
• 22:43
  if you allow for the um, you know, the, the
• 22:46
  variables. But this storey is saying.
• 22:49
  Hang on a minute, we, we think there's a
• 22:51
  better way.
• 22:53
  Professor Fred Watson: Yes, that's right. Uh, in
• 22:56
  Exactly. That it's all about. So
• 22:59
  let's just, uh, backtrack. What is the Hubble
• 23:02
  tension? Uh, so the
• 23:05
  expansion rate of the universe, uh,
• 23:07
  basically is a number that we was
• 23:10
  first measured by Edwin hubble back in 1929.
• 23:13
  Um, he got the wrong answer because he was
• 23:15
  only looking at a very small number of
• 23:17
  galaxies. But it comes about because, as
• 23:20
  you look at galaxies, ah, in the
• 23:23
  wider universe, uh, they get,
• 23:26
  um. Their velocity away from us
• 23:29
  is bigger the further away they are.
• 23:32
  And that comes about when you've got a
• 23:34
  universe that's expanding. That's the natural
• 23:36
  assumption and we've believed that ever
• 23:39
  since. Yeah. Excuse me. So.
• 23:42
  So, um, I've got a bit of Hubble tension in
• 23:44
  my chest there. Um, so that's how
• 23:47
  it's normally measured, measured the Hubble
• 23:50
  constant, this number,
• 23:53
  which is in slightly bizarre units, it's
• 23:56
  in megapas, uh, kilometres per second per
• 23:58
  megaparsec. Kilometres per second is
• 24:01
  the recession speed of a galaxy.
• 24:04
  A megaparsec is,
• 24:07
  uh, it 3.26. I can never remember the
• 24:09
  name. Million light years.
• 24:12
  It's the units that astronomers use for
• 24:14
  measuring distance parsecs. And it's a
• 24:17
  million parsecs. So, um, kilometres
• 24:20
  per second per megaparsec tells you how
• 24:23
  the velocity of a galaxy
• 24:25
  increases with distance and that's the
• 24:28
  result of the expansion of the universe. So
• 24:30
  the Hubble constant tells you how fast the
• 24:33
  universe is expanding. Now,
• 24:35
  now you can. The normal way of
• 24:38
  doing this is, uh. And it's actually why the
• 24:41
  Hubble telescope was created and why it got
• 24:44
  its name. Uh, we. Excuse me, we
• 24:47
  measure the brightness. Sorry, I've
• 24:50
  got my. Got my tension back there.
• 24:53
  If you want to cut this bit out, Huw, you're
• 24:55
  more than welcome to,
• 24:58
  um. It's fine now, uh,
• 25:02
  uh, the tension comes about. So, no, let me
• 25:05
  step back again. The measure, uh, where
• 25:07
  it's measured is you build up a sort of
• 25:10
  distance scale ladder. So the direct
• 25:12
  measurement of star distances in outer
• 25:15
  space comes about by the parallax
• 25:18
  method. As the Earth goes around the sun, we
• 25:21
  see stars, uh, apparently changing their
• 25:24
  position relative to very distant
• 25:26
  background stars. And that changing position
• 25:29
  you can measure. Uh, and in fact
• 25:31
  it's that. That gives the parsec its name.
• 25:34
  It's a parallax of 1/ arc second is what
• 25:37
  it's short for. And so that's a direct
• 25:39
  geometrical way of measuring the distance to
• 25:42
  certain stars. If you can do that to
• 25:44
  stars whose intrinsic brightness, you know,
• 25:47
  and these are typically, uh, Cepheid variable
• 25:49
  stars, then you can extend it because you
• 25:52
  know their brightness, uh, their intrinsic
• 25:54
  brightness, how much uh, light they radiate,
• 25:57
  then you can look at how faint they are
• 25:59
  further and further on. Um, and that's the,
• 26:02
  that's how we started off because Hubble
• 26:05
  measured um, um. In fact in
• 26:08
  1923 used these variable stars to
• 26:11
  measure the distance of the Andromeda, um,
• 26:12
  galaxy. Once again, he got it a bit wrong by
• 26:15
  today's standards. But that uh, was when we
• 26:17
  realised that galaxies weren't little things
• 26:19
  frutaling around in our own Milky Way. They
• 26:22
  are very distant objects. So, so that's the
• 26:25
  basic process and that has now been
• 26:28
  uh, basically elaborated by
• 26:31
  additional things which involve supernovae,
• 26:34
  the exploding stars, all sorts of other
• 26:37
  uh, cosmic phenomena. And that's the
• 26:40
  basis of what this storey is about
• 26:43
  because uh, that
• 26:46
  technology has now been
• 26:49
  absolutely refined to the nth degree,
• 26:52
  uh, by the scientists who are uh,
• 26:55
  uh, who are um, um,
• 26:57
  basically reporting this work. It's
• 27:00
  a study in astronomy and astrophysics, one of
• 27:03
  the leading journals, actually a European
• 27:05
  journal. Uh, and these scientists
• 27:08
  have spent a lot of time
• 27:11
  getting uh, the answer right from
• 27:14
  this method, what we call the distance ladder
• 27:16
  or the distance scale, by invoking
• 27:19
  objects of all kinds. And so they
• 27:22
  have produced a number for the Hubble
• 27:24
  constant which has a very, very
• 27:28
  small error. In fact they quote it as Ah,
• 27:30
  73.50
• 27:33
  kilometres per second per megaparsec
• 27:36
  plus or minus point zero, sorry,
• 27:39
  0.81 kilometres per
• 27:42
  second per megaset parsec. So they're talking
• 27:44
  about something that's either somewhere
• 27:47
  between 72.0 and 74. Sorry,
• 27:50
  72.5 and 74. 4.5
• 27:52
  thereabouts, which is a very, very
• 27:55
  tight uh, estimate of this
• 27:57
  velocity. Uh, so what's
• 28:00
  the tension about until somebody debunks
• 28:03
  them? Yeah, uh,
• 28:06
  well, it's true. Um, I do remember,
• 28:09
  um, back in the 70s, and I've told you this
• 28:11
  before, Andrew, there were two schools of
• 28:14
  thought, both offering measurements with very
• 28:17
  tight error limits, one of which said that
• 28:19
  the number was 50 and the other which said
• 28:22
  the number was 100. And lo and behold, when
• 28:25
  the Hubble telescope gave us the right
• 28:26
  answer, it was basically the average of those
• 28:28
  two around about 75. And it's now been
• 28:31
  refined.
• 28:31
  Andrew Dunkley: It's kind of what they're doing with this,
• 28:33
  isn't it?
• 28:34
  Professor Fred Watson: A little bit. Although they're really giving
• 28:37
  tight, very tight
• 28:39
  um, estimates based on everything that
• 28:42
  we can observe. Uh, whereas the previous
• 28:45
  this with the difference between 50 and 100
• 28:47
  and that was a kind of Hubble tension. We
• 28:49
  didn't call it the ah, that but that's sort
• 28:51
  of what it was. That was uh, based on
• 28:54
  uh, just individual, individual measurements
• 28:57
  from you know, their own particular school of
• 29:00
  thought. One was galaxies, one was supernovae
• 29:02
  or something. I can't remember how it worked,
• 29:04
  I can't remember the details. Probably could
• 29:06
  if I thought about it. Uh, but this brings
• 29:08
  them all together to get this super accurate
• 29:11
  so called value of 73.5.
• 29:14
  So the tension is that there is another way
• 29:18
  of determining uh, the Hubble
• 29:21
  constant and it involves uh, observing
• 29:23
  the cosmic microwave background radiation.
• 29:26
  That's the radiation that we see from the Big
• 29:28
  Bang. We're looking back 13.8 billion years
• 29:31
  to see that. What's sometimes called the
• 29:33
  afterglow of the Big Bang. It's really still
• 29:35
  the light of the Big Bang that you can see
• 29:37
  because you're looking so far back in time.
• 29:40
  And that gives us a different number. You
• 29:43
  can look at the, the, it's what's
• 29:46
  called the power spectrum. The cosmic
• 29:47
  microwave background radiation has these
• 29:49
  tiny, tiny fluctuations and by tiny
• 29:52
  I mean the amount fluctuations in
• 29:54
  temperature. You can measure the temperature
• 29:56
  of the radiation and they form in little
• 29:59
  blobs and we think that's where the galaxies
• 30:02
  came from. The cooler parts were where
• 30:04
  galaxies formed, the warmer parts were not.
• 30:07
  Uh, and so the microwave
• 30:10
  background radiation when you look at,
• 30:13
  looks like a wallpaper, uh, which is
• 30:16
  why I sometimes call it the cosmic wallpaper.
• 30:18
  Partly because it's behind everything else.
• 30:20
  Just like the wallpaper in a room is behind
• 30:22
  everything. But it's also got these patterns.
• 30:25
  So you can use those patterns to make another
• 30:27
  estimate of the uh, Hubble
• 30:30
  constant.
• 30:30
  And the answer that you get is 67
• 30:33
  kilometres per second per megaparsec, which
• 30:36
  is well outside the error
• 30:39
  band of the sort of traditional method.
• 30:41
  Method. And so I think
• 30:44
  what the direction this is going
• 30:47
  in is. So uh, as you and I have
• 30:50
  spoken about before, people have done a lot
• 30:53
  of work to try and look for where we've
• 30:56
  gone wrong here because these two numbers
• 30:58
  should give you the same answer. But they
• 30:59
  don't. But they don't. So
• 31:02
  now people are turning it upside down and
• 31:04
  saying maybe the fact that they don't give
• 31:06
  the same answer is telling us something
• 31:08
  about, about the physics of the universe that
• 31:10
  we don't know
• 31:12
  Andrew Dunkley: or we're just not accounting for everything
• 31:14
  we need to put into the formula.
• 31:16
  Professor Fred Watson: Yeah, yeah there's that too. And, but I think
• 31:19
  that's. So as time goes on people are ticking
• 31:22
  off all those things uh, simply because
• 31:24
  there's a lot more work being done on this
• 31:27
  topic. So the Hubble tension could turn out
• 31:29
  to be, uh, the gateway
• 31:32
  into new physics. That might tell us about
• 31:35
  dark matter and dark energy and all the other
• 31:38
  dark stuff that we think about. Yeah.
• 31:41
  So it's potentially, uh, something
• 31:44
  that I think, uh, scientists everywhere will
• 31:46
  keep an eye on. But, uh, it is really, um,
• 31:49
  really, uh, in many ways getting quite
• 31:51
  exciting that this Hubble tension is not
• 31:53
  going away. No, definitely not.
• 31:55
  Andrew Dunkley: It's come up a few times in the last 10 years
• 31:57
  that we've been doing this. So they keep
• 31:59
  looking at it and that's. And very good
• 32:01
  reasons to do so. Uh, for the record, a
• 32:04
  megaparsec is approximately 3.0 million light
• 32:07
  years. I think that's what you said.
• 32:08
  Professor Fred Watson: It is what I said. Yeah. I could never
• 32:10
  remember. I think it's 3.26.
• 32:12
  Andrew Dunkley: I thought that's what I found. Yes.
• 32:14
  Professor Fred Watson: Yeah. Very good.
• 32:16
  Andrew Dunkley: All right, uh, hopefully they've finally
• 32:18
  cracked the Hubble tension debate. Uh, I
• 32:20
  guess we'll find out if they keep coming up
• 32:22
  with different numbers in, in the future.
• 32:24
  But, uh, you can look it up@, uh,
• 32:26
  dailygalaxy.com or you can read the
• 32:28
  published paper at Astronomy and
• 32:30
  Astrophysics.
• 32:32
  Fred Watson, that brings us to the end of the
• 32:34
  programme. Thank you so much.
• 32:36
  Professor Fred Watson: A great pleasure, Andrew. Uh, we've covered
• 32:38
  some great topics today and, uh, it's always
• 32:41
  a delight.
• 32:42
  Andrew Dunkley: Yeah, it's very. A few different types of
• 32:45
  storeys this time around, which we like.
• 32:48
  We'll catch you on the next one, Fred Watson.
• 32:50
  Professor Fred Watson: I guess we will. Yes. Sounds good.
• 32:52
  Andrew Dunkley: Professor Fred Watson Watson, astronomer at
• 32:54
  large. And thanks to Huw in the studio. He
• 32:56
  couldn't be with us today because he caused a
• 32:58
  bit of, of hubby tension at home
• 33:03
  and he's been sent to the naughty corner.
• 33:05
  Don't, uh, forget to visit us online or, um,
• 33:08
  visit, uh, us on social media. And don't
• 33:10
  forget to send us your comments and questions
• 33:12
  via, uh, our website, space
• 33:13
  nutspodcast.com or
• 33:16
  spacenuts IO and, uh, leave
• 33:19
  reviews from your favourite podcasting
• 33:21
  platform in the meantime, from me, Andrew
• 33:23
  Dunkley. Thanks for your company. We'll see
• 33:24
  you on the very next episode of Space Nuts.
• 33:27
  Professor Fred Watson: Bye. Bye.
• 33:28
  Andrew Dunkley: You've been listening to the Space Nuts
• 33:31
  podcast, available at
• 33:34
  Apple Podcasts, Spotify,
• 33:36
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• 33:38
  player. You can also stream on
• 33:40
  demand@bytes.com.
• 33:42
  Professor Fred Watson: this has been another quality podcast
• 33:44
  production from bytes.com.