Latest / Space News Today / Nuclear Power in Space, SETI from the Moon & the Hubble Tension Unravelled | Space Nuts:...

Transcript

Nuclear Power in Space, SETI from the Moon & the Hubble Tension Unravelled | Space Nuts:... · Space News Today

• 0:00
  Hello again. Thank you for joining us.
• 0:02
  This is Space Nuts. My name is Andrew
• 0:05
  Dunley. If you've never heard of Space
• 0:06
  Nuts, where have you been for the last
• 0:08
  10 years? Uh good to have you along if
• 0:10
  you're a first timer and everybody else
• 0:12
  who's been with us for eons. Uh today on
• 0:16
  the show, we will be talking about uh a
• 0:19
  a really interesting and some might
• 0:22
  think scary development, nuclear space
• 0:25
  policies. I don't think they're talking
• 0:27
  about, you know, weapons of mass
• 0:29
  destruction, but they are talking about
• 0:31
  power supply systems. Uh we're also
• 0:34
  going to look at SETI from the far side
• 0:36
  of the moon because uh that's the best
• 0:38
  place to listen for alien civilizations
• 0:41
  because well, Earth is very noisy. But
• 0:44
  the far side of the moon, you can't hear
• 0:46
  a thing except the aliens apparently.
• 0:50
  And oh no, the Hubble tension debate is
• 0:53
  siming simmering again. We will get into
• 0:56
  all of that on this uh this episode of
• 0:59
  Space Nuts.
• 1:00
  >> 15 seconds. Guidance is internal. 10 9g
• 1:05
  Ignition sequence start.
• 1:07
  >> Space nuts.
• 1:08
  >> 5 4 3 2 1 2 3 4 5 5 4 3 2 1
• 1:13
  >> Space Nuts.
• 1:14
  >> Astronauts report. It feels good.
• 1:17
  >> And joining us to nuke a few stories is
• 1:19
  Professor Fred Watson, astronomer at
• 1:21
  large. Hello, Fred. Hello, Andrew.
• 1:24
  Lovely to uh hear your voice and see
• 1:27
  your face.
• 1:28
  >> It's my my voice is still a little bit
• 1:30
  down like that. I could do an Elvis song
• 1:33
  as a backing vocal.
• 1:34
  >> You could. Yeah.
• 1:35
  >> Yeah. Way on down.
• 1:37
  >> Well, we So, at the end of the show, you
• 1:39
  definitely need to say thank you very
• 1:41
  much.
• 1:42
  >> Thank you very much.
• 1:43
  >> Uh yeah, it's that's what happens when I
• 1:46
  get a cold. My voice just goes down
• 1:48
  deep. When I first started in radio, I
• 1:50
  did Midnight to Dawns in the days where
• 1:52
  they didn't automate it. Everything
• 1:54
  Everything was live
• 1:56
  >> and around 4 in the morning when I used
• 1:58
  to get really really tired, my voice
• 2:00
  would just naturally go down there and
• 2:05
  and it was really weird because um it
• 2:08
  wasn't my natural voice, but um at the
• 2:11
  moment it's it's enjoying that part of
• 2:13
  the spectrum. So
• 2:15
  >> yes, hopefully it'll get better soon. I
• 2:17
  don't like the feeling, I must say.
• 2:19
  >> No, you wouldn't.
• 2:21
  >> Anyway, we battle on, don't we? No point
• 2:23
  getting all
• 2:24
  >> that's, you know,
• 2:25
  >> we do in space nuts. We come rain or
• 2:28
  shine or absence or whatever, we keep
• 2:30
  going.
• 2:30
  >> We do. Speaking of battling on nuclear
• 2:34
  energy. Uh
• 2:36
  uh this this is a a policy that's just
• 2:39
  been announced by the Pentagon and the
• 2:41
  Department of Energy and they've kind of
• 2:43
  dragged NASA into it. They said, "Hey,
• 2:46
  NASA, we want you to build us a couple
• 2:48
  of power stations, and they've got to be
• 2:50
  nuclear, and they got to be ready by
• 2:51
  2028."
• 2:53
  How about it?
• 2:54
  >> Yeah, that's more or less it. It's a
• 2:58
  six-page policy document. Uh, its title
• 3:02
  is NSTM-3.
• 3:05
  uh which is to direct a parallel and
• 3:08
  mutually reinforcing design uh set of
• 3:11
  design competitions by NASA and the
• 3:13
  defense department to enable and I'm
• 3:15
  quoting here to enable near-term
• 3:17
  demonstration and use of low to midpower
• 3:20
  space reactors in orbit and on the lunar
• 3:22
  surface and prepare to deploy high power
• 3:25
  reactors in the 2030s. Uh I'm quoting
• 3:29
  here from uh uh from people who who are
• 3:32
  closely involved with this. For this to
• 3:34
  work, it has to be a collaboration
• 3:36
  between multiple government agencies.
• 3:38
  Well, that's that's a novel idea, isn't
• 3:40
  it?
• 3:40
  >> Yes.
• 3:41
  >> Um, that's the way
• 3:43
  >> that'll work.
• 3:44
  >> Yeah.
• 3:45
  >> That's the way that we do the right R&D
• 3:47
  and get the right tools in place for
• 3:49
  these events to unfold over the next few
• 3:51
  years.
• 3:51
  >> Yeah.
• 3:52
  >> Yes. So, um, that's right. So the bottom
• 3:54
  line is NASA
• 3:56
  is directed to start work within 30 days
• 4:01
  on a midpower space reactor generating
• 4:03
  at least 20 kW of power with a variant
• 4:06
  that can operate on the lunar surface.
• 4:08
  He calls for the agency to work with
• 4:10
  multiple companies on reactor designs,
• 4:12
  including for a low power system that
• 4:14
  produces as little as 1 kilowatt if
• 4:16
  doing so offers lower cost and schedule
• 4:19
  risk. This is um it's a White House uh
• 4:22
  release that I'm quoting from here. So,
• 4:24
  it's uh it's definitely the official
• 4:26
  thing.
• 4:26
  >> Yeah. Wow. Should we be surprised by
• 4:29
  this though?
• 4:30
  >> 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 NASA,
• 4:39
  who I think we covered this uh quite a
• 4:42
  few months ago, talked about the idea of
• 4:45
  uh using a 100 kow nuclear reactor on
• 4:47
  the lunar surface. that raises a few
• 4:50
  eyebrows. But it looks as though this is
• 4:52
  the first step in in um in expediting
• 4:56
  that to start small, maybe even the
• 4:59
  smallest 1 kilowatt. It'll run an
• 5:01
  electric fire uh and uh and um keep
• 5:04
  going upwards. Uh there's a interesting
• 5:08
  uh disparity in the sort of urgency of
• 5:11
  this though because um the next
• 5:14
  paragraph of the White House release
• 5:15
  says the policy calls on the defense
• 5:17
  department to provide a briefing to the
• 5:20
  White House in 90 days on potential uses
• 5:23
  and payloads for space nuclear systems
• 5:26
  of varying power levels. The Pentagon
• 5:28
  will in the first year of the policy use
• 5:30
  its space nuclear funding to support
• 5:32
  NASA's efforts, then conduct its own
• 5:34
  competition for space nuclear power
• 5:36
  systems. I get the feeling here that
• 5:38
  there's going to be too many fingers in
• 5:40
  the pie and too many people deciding
• 5:43
  which companies are going to get the,
• 5:44
  you know, going to get the contracts to
• 5:46
  do this.
• 5:48
  the the options for nuclear power these
• 5:51
  days are so much more
• 5:54
  uh available and and simple like you can
• 5:58
  make very small nuclear power stations
• 6:00
  now you you can you can build one that's
• 6:03
  that's small enough just to service a
• 6:06
  town these days you don't need these big
• 6:08
  complex
• 6:10
  >> setups anymore so it it probably is the
• 6:13
  logical way to go even though when you
• 6:15
  say the word nuclear everybody sort runs
• 6:17
  for the hills. Not that that would save
• 6:19
  them, but um it's not as big and scary
• 6:23
  as people
• 6:25
  envvisage, but um it it's it's got bad
• 6:28
  press for a long long time. So whenever
• 6:30
  you talk about nuclear power station or
• 6:32
  look what happened in Australia um we're
• 6:35
  so scared of it, we've never done it.
• 6:38
  And people think of three mile three
• 6:40
  mile island and churn bill
• 6:43
  >> uh and uh yes and the bottom line is
• 6:46
  that if things go wrong you have a very
• 6:48
  big environmental problem uh and that
• 6:51
  would look at Fukushima yeah with the um
• 6:54
  earthquake and the t and the and the
• 6:56
  tsunami. Yeah,
• 6:58
  >> that's a mess.
• 7:00
  >> Yes. So uh it is scary I think. Um
• 7:05
  but but well so I grew up in a country
• 7:07
  that uh pioneered nuclear power with the
• 7:10
  US and there are several nuclear power
• 7:13
  stations. Uh I used to live not very far
• 7:15
  from one actually at Torres in Scotland.
• 7:19
  >> Is it is that right? Yes. I think it's
• 7:21
  Torres. Uh and um look it everybody just
• 7:25
  regarded it as a normal power station.
• 7:27
  It was very much a low-key thing. Uh and
• 7:30
  and you you see statistics like there's
• 7:34
  more radiation comes from the natural
• 7:37
  emissions from rocks in the UK. If you
• 7:40
  go down to Cornwall, the rocks are
• 7:41
  basically radioactive there.
• 7:43
  >> Oh wow.
• 7:44
  >> There's radon in the atmosphere. Um but
• 7:46
  it's at a level that humans can
• 7:48
  tolerate. Humans have been tolerating it
• 7:51
  for hundreds of thousands of years. And
• 7:53
  uh that's Yeah. You're exposed to
• 7:56
  radiation every time you walk outside.
• 7:58
  >> Well, that's right. you are. Yes. So,
• 8:01
  um, so it it it's got to be treated with
• 8:04
  respect. Um, I I I think what freaks
• 8:07
  people out though as well is the idea of
• 8:09
  sticking a nuclear reactor on top of a
• 8:12
  rocket and then sending it into space.
• 8:15
  And there was an accident uh with a so
• 8:18
  just stepping back NASA has used their
• 8:21
  RTGS radioisotope thermal gener
• 8:26
  thermmoelectric generators. I think
• 8:27
  that's what it stands for. Uh on several
• 8:30
  spacecraft including the two Voyagers. I
• 8:32
  think the Pioneers have got it as well.
• 8:34
  Um the um Curiosity and
• 8:39
  um Perseverance both have RTG power
• 8:42
  supplies. Uh so so that's well you know
• 8:46
  a well trodden path but there was an
• 8:49
  accident. I think it might have been in
• 8:50
  the 80s with a spacecraft that was
• 8:52
  launched with something like an RTG on
• 8:54
  board and it did uh it went wrong. I
• 8:58
  can't remember the details, but I think
• 9:00
  it was Canada that took the the punch
• 9:02
  and there was a lot of radioactive
• 9:05
  debris that got spread over very very uh
• 9:09
  sparsely populated regions of Canada.
• 9:13
  >> Literal fallout.
• 9:14
  >> Yes, that's right. Yes, exactly. Falls
• 9:16
  out the sky. If I remember rightly, I'm
• 9:18
  I'm digging up things from the past
• 9:20
  year, but I think that's the case. And
• 9:21
  that that clearly freaks people out. If
• 9:24
  you've got a launch that doesn't work,
• 9:26
  uh what's going to happen? I imagine so.
• 9:29
  But, uh it certainly does ramp up the
• 9:31
  space race between the US and China. And
• 9:34
  you know, China's probably going to fall
• 9:35
  a bit behind here because I think they
• 9:37
  were trying to set up a coal fired power
• 9:39
  station on the moon. You know, it um
• 9:42
  >> might might slow them down a bit.
• 9:44
  >> Yeah, China's doing pretty well. They
• 9:46
  are doing
• 9:47
  >> sustainability. Yeah.
• 9:49
  >> Yeah, they are.
• 9:49
  >> But yeah, they do use a lot of coal
• 9:51
  still. Yeah,
• 9:52
  >> they do. They do. So, this is probably
• 9:54
  going to happen. And what other option
• 9:57
  would there be? That's the thing. I
• 9:59
  mean, some people will say, "No, put up
• 10:00
  solar energy systems, but um nuclear is
• 10:04
  probably a a much more efficient way of
• 10:07
  doing it."
• 10:08
  >> Yeah. Well, for a start, you've got the
• 10:10
  baseline load. You don't not worried
• 10:12
  about where the sun is in the sky.
• 10:14
  Correct. The idea of being at the south
• 10:17
  pole of the moon which is where the
• 10:20
  focus is in terms of uh our exploration
• 10:23
  of the moon uh is it it puts a different
• 10:27
  slant on it because it means that you
• 10:29
  are looking at a very low sun altitude
• 10:32
  in the sky. Uh the sun's coming in
• 10:35
  nearly horizontally the sunlight. Now
• 10:36
  that's not uh as bad a thing on the moon
• 10:40
  as it would be on the earth. The Earth,
• 10:42
  as the sun gets lower, it's going
• 10:44
  through a thicker and thicker layer of
• 10:45
  atmosphere. So, it's power is
• 10:47
  attenuated.
• 10:48
  >> On the moon, that doesn't happen because
• 10:50
  there ain't no atmosphere. But, it does
• 10:52
  bring challenges for your solar panels.
• 10:55
  You know, you've got to build arrays
• 10:56
  that are almost vertical. And if you're
• 10:59
  looking for a big structure, uh then
• 11:01
  it's uh it it becomes different slightly
• 11:04
  different engineering um issue. Plus,
• 11:07
  you've got to take all that stuff up
• 11:08
  there as well. You know, going up to the
• 11:11
  moon with arrays of solar panels in the
• 11:13
  spacecraft might not leave room for much
• 11:15
  else. Whereas a nuclear reactor of the
• 11:17
  kind that people are talking about will
• 11:18
  be relatively compact. I mean, the the
• 11:21
  RTG devices are I think it's is it 13 kg
• 11:25
  of uh of plutonium that they have in
• 11:29
  them and they're about the size of a you
• 11:32
  know a tea or something like that or
• 11:35
  >> a drinks. Yeah.
• 11:36
  >> Yeah. It it's it's much simpler than it
• 11:39
  was 20, 30, 40, 50 years ago.
• 11:42
  >> And of course, they're talking not only
• 11:43
  about the moon, but uh people on Mars,
• 11:46
  so they'll need power as well. Uh I know
• 11:48
  in the movie The Martian, they used
• 11:50
  solar panels, but Mars is bit further
• 11:52
  away, so the solar panels probably
• 11:54
  wouldn't be as efficient.
• 11:55
  >> Exactly.
• 11:56
  >> Uh nuclear power makes makes perfect
• 11:59
  sense. Although you know solar solar
• 12:02
  energy is quite um well used in space
• 12:07
  too used it.
• 12:09
  >> Um that's correct. Yes. Uh and um you
• 12:12
  know thinking of the different
• 12:14
  spacecraft the one that's got perhaps
• 12:15
  the most spectacular solar panels is the
• 12:17
  Lucy spacecraft which is on its way to
• 12:20
  the Trojan 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
• 12:28
  belt and beyond. actually going to the
• 12:30
  orbit of Jupiter which is where the
• 12:31
  Trojan asteroids hang out. Uh so you
• 12:34
  need big solar panels to collect all the
• 12:36
  energy.
• 12:37
  >> Yeah. The other problem with solar
• 12:38
  panels on Mars would be dust because
• 12:41
  >> it's it's a pretty grubby place.
• 12:44
  >> Yeah. That's what um probably brought an
• 12:46
  end to so Spirit and Opportunity both
• 12:49
  had solar panels. Uh and they there were
• 12:52
  certainly times when the amount of dust
• 12:54
  was stopping the power generation and
• 12:57
  that was cleared by uh willy-willies as
• 13:00
  they're called
• 13:02
  the
• 13:03
  >> dust devils that's right on Mars. Yeah.
• 13:05
  >> Fascinating. All right. So the um the
• 13:08
  directive has been put to NASA to start
• 13:10
  working on this.
• 13:12
  >> Uh and it comes from the White House. So
• 13:14
  um it's all systems go and they hope to
• 13:16
  have something operational as soon as
• 13:19
  2028. So they're not mucking around. In
• 13:22
  fact, I think NASA after this was
• 13:23
  released were given one month to get
• 13:25
  started.
• 13:26
  >> So,
• 13:26
  >> uh, that's exactly right. That's the 30
• 13:28
  days that I mentioned earlier.
• 13:29
  >> No mucking around.
• 13:30
  >> Get going.
• 13:31
  >> Yep. Uh, you can read all about it at
• 13:33
  spacnews.com.
• 13:36
  This is Space Nuts with Andrew Dunley
• 13:38
  and Professor Fred Watson.
• 13:43
  >> G. And I feel
• 13:45
  >> space nuts.
• 13:46
  >> Well, we mentioned the moon. We'll stick
• 13:48
  with the moon. This story though has
• 13:50
  nothing to do with people on the moon.
• 13:52
  It's got uh everything to do with people
• 13:54
  that are not on Earth or the moon or
• 13:57
  Mars for that matter. They uh they're
• 13:59
  out there somewhere. We're looking for
• 14:01
  them. We're talking about the search for
• 14:03
  extraterrestrial intelligence and the
• 14:06
  dark side of the moon, the far side of
• 14:08
  the moon is uh the best place to start
• 14:11
  looking.
• 14:13
  >> Uh that's right. So, we've been looking
• 14:14
  for this for 60 years. um and
• 14:18
  >> and using uh groundbased antennas here
• 14:22
  on planet earth uh which are very very
• 14:26
  capable um when once the square
• 14:29
  kilometer array observatory comes on
• 14:31
  stream towards the end of the decade uh
• 14:34
  we'll have the finest most capable radio
• 14:37
  telescope in the world uh which will not
• 14:41
  directly engage with SETI programs but
• 14:44
  it will
• 14:45
  uh have the sensitivity to detect well
• 14:48
  the thing that my colleagues tell me is
• 14:50
  it'll detect an airport radar at 50
• 14:52
  light years.
• 14:53
  >> Yeah.
• 14:54
  >> Uh so that's the kind of sensitivity uh
• 14:57
  that you're talking about. Um, but the
• 15:00
  main problem with groundbased with
• 15:02
  earthbased uh radio telescopes is that
• 15:05
  they're compromised by all the the
• 15:07
  cacophony of radio signals that
• 15:10
  surrounds us from your mobile phones,
• 15:12
  from broadcasts, from people like you
• 15:15
  and me doing this, going out into the
• 15:17
  ether,
• 15:18
  >> Wi-Fi routers,
• 15:19
  >> Wi-Fi, the whole thing, microwave ovens,
• 15:22
  it all provides this noisy radio
• 15:24
  background. And that's not getting any
• 15:27
  better with the um satellite mega
• 15:29
  constellations.
• 15:31
  I was in a meeting yesterday where which
• 15:35
  for it's a meeting of the um
• 15:37
  international astronomical union center
• 15:39
  for the protection of the dark and quiet
• 15:42
  sky from satellite interference. Uh and
• 15:45
  it was um you know one of the things
• 15:47
  that's raising anxiety is the idea of uh
• 15:50
  Elon Musk's million satellites for for
• 15:53
  um orbital data u orbital data centers
• 15:57
  and this mirror in the sky idea sunlight
• 16:00
  on demand that also has a million
• 16:01
  satellites with mirrors on it. That's
• 16:04
  that's more for the optical astronomers
• 16:05
  but it's all a concern. uh and it's it
• 16:09
  it basically is eroding our capability
• 16:11
  slowly but surely to detect uh faint
• 16:14
  extraterrestrial signals.
• 16:17
  Uh so that brings us to currently
• 16:21
  possibly the best place to do this sort
• 16:24
  of thing from which is the far side of
• 16:27
  the moon. Uh and um uh we have one uh
• 16:33
  spacecraft by we I mean humankind have
• 16:36
  one spacecraft on the far side of the
• 16:38
  moon. Uh it is China's Chang 4 uh which
• 16:42
  soft landed on the far side of the moon
• 16:44
  back in 2019. Can you believe it? It's
• 16:47
  been there.
• 16:49
  >> Uh this is seven years. It's quite
• 16:51
  extraordinary. Um but uh now that um
• 16:56
  spacecraft was not set up uh
• 16:59
  specifically for uh for looking for um
• 17:03
  SETI search for extraterrestrial
• 17:05
  intelligence but it's got a low
• 17:08
  frequency radio spectrometer on board uh
• 17:12
  that actually has been used to conduct
• 17:15
  the first ever SETI search from the
• 17:17
  lunar far side. Um and so the the goal
• 17:22
  uh the idea is to use that equipment
• 17:26
  which is designed to do natural sciences
• 17:29
  but to look for um those uh techno
• 17:34
  signatures uh technomarkers they're
• 17:36
  sometimes called uh which might suggest
• 17:39
  that you're getting a signal from an
• 17:41
  artificially generated source. And what
• 17:44
  you're really looking for are uh
• 17:47
  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 got
• 18:00
  to think back to Joselyn Bell and her
• 18:04
  discovery of the first pulsar because
• 18:06
  that's what she saw. um narrow band um
• 18:09
  sorry uh narrow band in time signatures
• 18:14
  uh or bursts of radiation which we now
• 18:17
  know is the pulsar the kind of
• 18:18
  lighthouse beam of radiation from the
• 18:20
  pulsar sweeping round and passing the
• 18:22
  earth. Um she didn't know that then so
• 18:25
  she wrote little green men in her uh in
• 18:28
  on her chart record of very very famous
• 18:31
  words. Um so that's what basically uh
• 18:35
  the uh Changa um low frequency radio
• 18:39
  spectrometer has been looking for. Uh
• 18:41
  and it's things that um you know that
• 18:44
  speak of an artificially generated
• 18:46
  source. And so um what's what they've
• 18:50
  done uh the scientists working on this
• 18:53
  uh basically they built an algorithm
• 18:56
  uh that uh uh troll through the data
• 18:59
  looking for anything that might be
• 19:03
  artificial with no credible candidates
• 19:07
  revealed. Uh nothing that couldn't be
• 19:10
  explained either by you know natural
• 19:13
  phenomena or by instrument uh issues. Um
• 19:18
  there's a nice comment though from
• 19:20
  fizz.org who is carrying this story. Uh
• 19:25
  this is I'll quote this. This is not a
• 19:27
  failure. It is a beginning. As Carl Sean
• 19:29
  once put it, absence of evidence is not
• 19:33
  evidence of absence. Brilliant.
• 19:35
  >> Really good point.
• 19:36
  >> I I got I had a lot of time for Carl
• 19:38
  Sean, very wise man and um yeah, he uh
• 19:41
  he did a lot for astronomy
• 19:43
  >> during his time. But um that's a valid
• 19:46
  point and and I suppose you and I have
• 19:48
  spoken about it in the past. The big
• 19:50
  problem is distance. There might there
• 19:53
  might be civilizations out there that
• 19:55
  are advanced and capable of
• 19:57
  communication, but they're so far away
• 19:59
  we will never hear from them.
• 20:01
  >> Maybe that Yeah. Um that's right. Uh and
• 20:05
  you know, and time is the other issue.
• 20:07
  It's a needle in a hay stack both in
• 20:09
  distance and in time because you've got
• 20:11
  to hit your civilization just at the
• 20:13
  right time.
• 20:14
  >> Yes.
• 20:15
  >> Uh when they are technologically enough
• 20:18
  to have airport radar, for example, uh
• 20:20
  but haven't wiped themselves out because
• 20:22
  of the loonies that they've generated.
• 20:24
  You're more you're more likely to get a
• 20:26
  um a tick tock of some kid doing a
• 20:29
  stupid rap song. That's probably that's
• 20:32
  what you'll get from from an
• 20:35
  extraterrestrial intelligence. Um what
• 20:38
  what I wonder is with the far side of
• 20:42
  the moon, yes, it's radio silent, but
• 20:44
  does it cover enough of the spectrum of
• 20:47
  the universe to to pick up something or
• 20:50
  is or is it fairly narrow in its its
• 20:52
  scope?
• 20:53
  >> Uh do you mean uh in terms of direction
• 20:55
  or
• 20:56
  >> Yeah. being able to pick something up?
• 20:58
  Is it got like a wide array? I mean the
• 21:00
  far side of the moon um you know if you
• 21:03
  plunk something on the equator of the
• 21:06
  moon on the far side over a month you
• 21:09
  cover the entire sky. No
• 21:11
  >> uh if your Yeah. If your um if your uh
• 21:15
  equipment is broadband enough and all
• 21:18
  the seti stuff is it's got a very wide
• 21:20
  range of spectral of frequencies.
• 21:22
  Although they do tend to to concentrate
• 21:25
  on uh what we call the 21 cm line. This
• 21:29
  is the frequency the specific frequency
• 21:32
  that's radiated by cold hydrogen.
• 21:34
  >> Uh and they do tend to concentrate on
• 21:37
  that because everybody in the universe
• 21:39
  will be aware of that 21 cm uh uh
• 21:43
  wavelength because that's called
• 21:45
  hydrogen which is the same everywhere.
• 21:48
  >> Yeah, makes sense. All right. Uh
• 21:51
  fascinating story. Um nothing yet but
• 21:54
  that doesn't mean that doesn't mean
• 21:56
  it'll always be nothing. So
• 21:58
  >> it's not um evidence of absence. That's
• 22:01
  right.
• 22:02
  >> Exactly. You can read all about it as
• 22:04
  Fred said at the fizz physf.org
• 22:08
  website. This is Space Nuts. Andrew
• 22:10
  Dunley here with Professor Fred Watson.
• 22:15
  >> Okay, we checked all four systems and
• 22:17
  with the
• 22:18
  >> Space Nuts.
• 22:19
  >> Our final story, Fred, uh brings us back
• 22:22
  to that old debate about the Hubble
• 22:25
  tension. Now, the Hubble tension is
• 22:28
  measured in two different ways, and they
• 22:30
  come up with two different answers, and
• 22:32
  that's troubled people for a while.
• 22:35
  Although, we did a story not so long ago
• 22:36
  that suggested, hang on a minute, the
• 22:39
  differences aren't that significant. So,
• 22:41
  they're probably both right if you allow
• 22:44
  for the u you know, the the variables.
• 22:47
  But this story is saying, "Hang on a
• 22:49
  minute. We we think there's a better
• 22:52
  way."
• 22:53
  >> Yes, that's right. uh in exactly that
• 22:57
  it's all about so le let's just uh
• 23:00
  backtrack what is the Hubble tension uh
• 23:04
  so the expansion rate of the universe
• 23:07
  basically is a number that we was first
• 23:10
  measured by Edwin Hubble back in 1929
• 23:14
  um he got the wrong answer because he
• 23:15
  was only looking at a very small number
• 23:17
  of galaxies but it it comes about
• 23:19
  because as you look at galaxies
• 23:23
  in the wider universe
• 23:25
  uh they get um their velocity away from
• 23:29
  us 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
• 23:36
  natural assumption and we've believed
• 23:38
  that ever since. Yeah. Excuse me. So, so
• 23:43
  um got a bit of Hubble tension in my
• 23:44
  chest there. Um so that's how it's
• 23:47
  normally measure measured the Hubble
• 23:50
  constant
• 23:52
  this number which is in slightly bizarre
• 23:55
  units. It's in mega par kilometers/s per
• 23:58
  mega par sec. Kilometers/s is the
• 24:02
  recession speed of a galaxy. A mega parc
• 24:05
  is uh is it 3.26 I can never remember
• 24:09
  the name. Million light years. Uh it's
• 24:12
  the it's the units that astronomers use
• 24:14
  for measuring distance parex and it's a
• 24:17
  million parex. So um kilometers/s per
• 24:21
  mega parc tells you how the velocity of
• 24:24
  a g galaxy increases with distance and
• 24:27
  that's the result of the expansion of
• 24:29
  the universe. So the hub constant tells
• 24:32
  you how fast the universe is expanding.
• 24:34
  Now,
• 24:35
  >> now you can you the normal way of doing
• 24:39
  this is uh and it's actually why the
• 24:41
  Hubble telescope was created and why it
• 24:44
  got its name. Uh we excuse me. We
• 24:47
  measure the brightness.
• 24:49
  Sorry, I've got my got my tension back
• 24:51
  there.
• 24:53
  If you want to cut this bit out, Hugh,
• 24:55
  you're more than welcome to.
• 24:58
  Um it's it's fine now. uh the uh the the
• 25:02
  tension comes about. So no, let me step
• 25:05
  back again. The uh measure the way it's
• 25:08
  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
• 25:20
  sun, we see stars uh apparently changing
• 25:23
  their position with relative to very
• 25:26
  distant background stars. And that
• 25:28
  change in position you can measure uh
• 25:30
  and in fact it's that that gives the
• 25:33
  parseek its name. It's a parallax of one
• 25:35
  arcsec is what it's short for. And so
• 25:38
  that's a direct geometrical way of
• 25:41
  measuring the distance to certain stars.
• 25:43
  If you can do that to stars whose
• 25:45
  intrinsic brightness you know and these
• 25:48
  are typically sephied variable stars
• 25:50
  then you can extend it because you know
• 25:52
  their brightness uh their intrinsic
• 25:54
  brightness how much uh light they
• 25:56
  radiate then you can look at how faint
• 25:59
  they are further and further on um and
• 26:01
  that's the that's how we started off
• 26:03
  because Hubble um measured um in fact in
• 26:08
  1923 used these variable stars to
• 26:11
  measure the distance of the Andromeda
• 26:12
  galaxy. Once again, he got it a bit
• 26:14
  wrong by today's standards, but uh that
• 26:17
  was when we realized that galaxies
• 26:18
  weren't little things frutling around in
• 26:20
  our own milky way. They are very distant
• 26:23
  objects. So that's the basic process and
• 26:26
  that has now been uh basically
• 26:29
  elaborated by additional things which
• 26:33
  involve supernovi, the exploding stars,
• 26:36
  all sorts of other uh cosmic phenomena.
• 26:39
  And that's the basis of what this story
• 26:42
  is about because
• 26:45
  uh that technology has now been
• 26:49
  absolutely refined to the nth degree uh
• 26:53
  by the scientists who are uh who are u
• 26:57
  uh basically reporting this work. Uh
• 27:00
  it's a study in astronomy and
• 27:02
  astrophysics one of the leading journals
• 27:04
  actually a European journal. uh and the
• 27:07
  these scientists have spent a lot of
• 27:10
  time getting uh the answer right from
• 27:14
  this method what we call the distance
• 27:16
  ladder or the distance scale by invoking
• 27:19
  objects of all kinds and so they have
• 27:23
  produced a number for the Hubble
• 27:24
  constant which has a very very small
• 27:28
  error in fact they quote it as 7350
• 27:33
  kilometers/s per megap par sec plus or
• 27:37
  minus.0
• 27:38
  sorry 0.81
• 27:41
  kilometers/s per mega par sec. So
• 27:44
  they're talking about something that's
• 27:46
  either somewhere between 72.0 and 74
• 27:49
  sorry 72.5 and 74.5 thereabouts which is
• 27:54
  a very very tight uh estimate of this
• 27:58
  velocity.
• 27:59
  Uh so what's the tension about
• 28:02
  >> until somebody debunks them?
• 28:05
  >> Yeah. Uh it well it's true. Um I do
• 28:08
  remember um back in the 70s and I've
• 28:11
  told you this before, Andrew, there were
• 28:13
  two schools of thought. Both offering
• 28:16
  measurements with very tight error
• 28:18
  limits. One of which said that the
• 28:20
  number was 50 and the other which said
• 28:22
  the number was 100. Yeah. And lo and
• 28:24
  behold, when we when the Hubble
• 28:25
  telescope gave us the right answer, it
• 28:27
  was basically at the average of those
• 28:28
  two around about 75. It's now been
• 28:31
  refined.
• 28:31
  >> It's kind of what they're doing with
• 28:33
  this, isn't it?
• 28:34
  >> A little bit, although they're they're
• 28:36
  really giving tight very tight um
• 28:40
  estimates based on everything that we
• 28:42
  can observe, right?
• 28:43
  >> Uh whereas the previous this with it the
• 28:46
  difference between 50 and 100 and that
• 28:48
  was a kind of hollow tension. We didn't
• 28:50
  call it that, but that's sort of what it
• 28:51
  was. that uh was based on uh just
• 28:55
  individ individual measurements from you
• 28:58
  know their own particular school of
• 29:00
  thought. One was galaxies, one was
• 29:02
  supernovi or something. I can't remember
• 29:03
  how it worked. I can't remember the
• 29:05
  details. Probably could if I thought
• 29:06
  about it. Uh but this brings them all
• 29:09
  together to get this super accurate
• 29:11
  so-called value of 73.5.
• 29:14
  So the tension is that there is another
• 29:17
  way of uh determining the Hubble
• 29:21
  constant and it involves uh observing
• 29:23
  the cosmic microwave background
• 29:25
  radiation. That's the radiation that we
• 29:27
  see from the big bang. We're looking
• 29:29
  back 13.8 billion years to see that
• 29:32
  what's sometimes called the afterglow of
• 29:34
  the Big Bang. It's really still the
• 29:36
  light of the Big Bang that you can see
• 29:37
  because you're looking so far back in
• 29:39
  time.
• 29:39
  >> Yeah.
• 29:40
  >> And that gives us a different number.
• 29:42
  You can you can look at the um it's
• 29:45
  what's called the power spectrum. The
• 29:47
  the the cosmic microwave background
• 29:48
  radiation has these tiny tiny
• 29:51
  fluctuations and by tiny I mean the
• 29:53
  amount fluctuations in temperature. You
• 29:55
  can measure the temperature of the
• 29:56
  radiation and they they form in little
• 29:59
  blobs and we think that's where the
• 30:02
  galaxies came from. The the cooler parts
• 30:03
  were where galaxies formed. The warmer
• 30:06
  parts were not. Uh, and so this the
• 30:09
  microwave background radiation when you
• 30:11
  when you look at it, it looks like it
• 30:13
  looks like a p a wallpaper pattern. Uh,
• 30:16
  which is why I sometimes call it the
• 30:17
  cosmic wallpaper. Partly because it's
• 30:19
  behind everything else just like the
• 30:21
  wallpaper in a room is behind
• 30:22
  everything.
• 30:23
  >> Yeah.
• 30:23
  >> Uh, but it's also got these patterns. So
• 30:25
  you can use those patterns to make
• 30:27
  another estimate of the uh Hubble
• 30:30
  constant. And the answer that you get is
• 30:33
  67 kilometers/s per mega parse which is
• 30:37
  well outside the error band of the sort
• 30:41
  of traditional method.
• 30:43
  >> And so I think what the direction this
• 30:47
  is going in is so as you and I have
• 30:50
  spoken about before people have done a
• 30:53
  lot of work to try and look for where
• 30:56
  we've gone wrong here because these two
• 30:57
  numbers should give you the same answer
• 30:59
  but they don't. that they don't.
• 31:02
  >> And so now people are turning it upside
• 31:04
  down and saying maybe the fact that they
• 31:06
  don't give the same answer is telling us
• 31:08
  something about the physics of the
• 31:09
  universe that we don't know
• 31:12
  >> or we're just not accounting for
• 31:14
  everything we need to put into the
• 31:16
  formula.
• 31:16
  >> Yeah. Yeah. There's that too. And but I
• 31:19
  think that's so as time goes on people
• 31:21
  are ticking off all those things
• 31:23
  >> uh simply because there's a lot more
• 31:25
  work being done on this on this topic.
• 31:28
  So the Hubble tension could turn out to
• 31:30
  be uh the gateway into new physics that
• 31:34
  might tell us about dark matter and dark
• 31:37
  energy and all the other dark stuff that
• 31:39
  we we think about. Yeah. So it's it's
• 31:42
  potentially uh something that I think uh
• 31:45
  scientists everywhere will keep an eye
• 31:47
  on. Uh but it is really um really in
• 31:50
  many ways getting quite exciting that
• 31:52
  this Hubble tension is not going away.
• 31:54
  >> No, definitely not. It's come up a few
• 31:56
  times in the last 10 years that we've
• 31:58
  been doing this. So, they keep looking
• 32:00
  at it and that's and very good reasons
• 32:02
  to do so. Uh, for the record, a mega
• 32:04
  parseek is approximately 3.26 million
• 32:07
  lighty years. I think that's what you
• 32:08
  said.
• 32:09
  >> That is what I said. Yeah. I could never
• 32:10
  remember. I think it's 3.26. I told
• 32:13
  >> that's what I found. Yes.
• 32:14
  >> Yeah. Very good. All right. Uh,
• 32:16
  hopefully they've finally cracked the
• 32:18
  Hubble tension debate. Uh, I guess we'll
• 32:21
  find out if they keep coming up with
• 32:22
  different numbers in in the future, but
• 32:25
  uh, you can look it up at daily
• 32:26
  galaxy.com or you can read the published
• 32:29
  paper at astronomy and astrophysics.
• 32:32
  Fred, that brings us to the end of the
• 32:34
  program. Thank you so much.
• 32:36
  >> A great pleasure, Andrew. Uh, we've
• 32:38
  covered some great topics today and, uh,
• 32:41
  it's always a delight.
• 32:42
  >> Yeah, it's very, very, you know, a few
• 32:44
  different types of stories this time
• 32:46
  around, which we like. We'll catch you
• 32:48
  on the next one, Fred.
• 32:50
  >> Uh, I guess we will. Yes, sounds good.
• 32:52
  >> Professor Fred Watson, astronomer at
• 32:54
  large. And thanks to Hugh in the studio.
• 32:56
  He couldn't be with us today because he
• 32:58
  caused a bit of hubby tension at home
• 33:03
  and he's been sent to the naughty
• 33:04
  corner. Uh, don't forget to visit us
• 33:06
  online or um visit us on social media
• 33:09
  and don't forget to send us your
• 33:11
  comments and questions via our website,
• 33:13
  spacenutspodcast.com
• 33:15
  or spacenuts.io. io and uh leave reviews
• 33:19
  from your favorite podcasting platform
• 33:21
  in the meantime. From me, Andrew Dunley,
• 33:24
  thanks for your company. We'll see you
• 33:24
  on the very next episode of Space Nuts.
• 33:27
  Bye-bye.
• 33:28
  >> Space Nuts.
• 33:29
  >> You've been listening to the Space Nuts
• 33:31
  podcast,
• 33:33
  >> available at Apple Podcasts, Spotify,
• 33:36
  iHeart Radio, or your favorite podcast
• 33:38
  player. You can also stream on demand at
• 33:41
  byes.com. This has been another quality
• 33:44
  podcast production from sites.com.