Nuclear Power in Space, SETI from the Moon & the Hubble Tension Unravelled

WEBVTT

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Andrew Dunkley: Hello again. Thank you for joining us. This

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is Space Nuts. My name is Andrew

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Dunkley. If you've never heard of Space Nuts,

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where have you been for the last 10 years?

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Good, uh, to have you along if you're a first

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timer. And everybody else who's been with us

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for aeons. Uh, today

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on the show we will be talking about,

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uh, a. Ah, really interesting and some

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might think scary development, nuclear

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space policies. I don't think they're talking

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about, you know, weapons of mass destruction,

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but they are talking about power supply

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systems. We're, uh, also going to look at

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SETI from the far side of the moon because,

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uh, that's the best place to listen for alien

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civilizations because, well, Earth is very

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noisy. But the far side of the moon,

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you can't hear a thing. Except the aliens,

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apparently. And. Oh, uh, no. The

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Hubble tension debate is simmering

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again. We'll get into all of that on, on

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this, uh, this episode of space

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nuts.

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Generic: 15 seconds. Guidance is internal.

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10, 9. Ignition

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sequence start.

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Professor Fred Watson: Space nuts.

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Generic: 5, 4, 3, 2. 1. 2, 3, 4,

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5, 5, 4, 3, 2, 1.

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Andrew Dunkley: Space nuts.

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Generic: Astronauts report it feels good.

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Andrew Dunkley: And joining us to nuke a few storeys is

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Professor Fred Watson Watson, uh, astronomer

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at large. Hello, Fred Watson.

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Professor Fred Watson: Hello, Andrew. Lovely to hear, uh, your

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voice and see your face.

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Andrew Dunkley: Yes, my voice is still a little bit down

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like that. Could do an Elvis song as a

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backing.

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Professor Fred Watson: Oh, you could, yeah, yeah, Way on, just down.

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Well, we. So at the end of the show, you

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definitely need to say thank you very much.

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Andrew Dunkley: Thank you very much. Uh, yes,

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that's what happens when I get a cold. My

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voice just goes down deep. When I first

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started in radio, I did midnight to dawns. In

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the days where they didn't automate it,

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everything, everything was live.

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And around four in the morning when I used to

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get really, really tired, my voice would just

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naturally go down there and.

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And it was really weird because, um,

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it wasn't my natural voice. But,

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um, at the moment it's. It's enjoying that

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part of the spectrum.

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Professor Fred Watson: So, m. Yes.

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Andrew Dunkley: Hopefully it'll get better soon. I don't like

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the feeling, I must say.

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Professor Fred Watson: No, you wouldn't.

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Andrew Dunkley: Anyway, we battle on, don't we?

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Professor Fred Watson: No point getting all that's. You know,

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we do in Space Nuts. We come rain or shine

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or absence or whatever, we keep going. We do.

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Andrew Dunkley: Speaking of battling on nuclear energy,

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uh, this. This is a policy that's just been

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announced by the Pentagon and the Department

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of Energy and they've kind of dragged NASA

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into it. They said, hey, NASA,

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we want you to build us a couple of power

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stations and they've got to be nuclear and

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they've got to be ready by 2028. How about

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it?

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Professor Fred Watson: Yeah, that's more or less it.

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It's a six page policy document.

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Uh, its title is NSTM

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M3. Uh, which is

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to direct a parallel and mutually

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reinforcing design, uh, set of design

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competitions by NASA and the Defence

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Department to enable, and I'm quoting here,

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to enable near term demonstration and use of

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mid power space reactors in orbit and on the

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lunar surface and prepare to deploy

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high power reactors in the 2000 and 30s.

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Uh, I'm quoting here from uh,

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people who are closely involved with this.

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For this to work it has to be a collaboration

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between multiple government agencies. Well

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that's a novel idea, isn't it? Yeah,

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um, that's the way that work.

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Yeah, that's the way that we do the right R

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D and get the right tools in place for these

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events to unfold over the next few years.

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Yeah. Yes. So um, that's right. So the

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bottom line is NASA is

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directed to start work within

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30 days on a mid power space

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reactor generating at least 20 kilowatts of

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power with a variant that can operate on the

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lunar surface. He calls for the

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agency to work with multiple companies on

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reactor designs including for a low power

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system that produces as little as 1 kilowatt

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if doing so offers lower cost and schedule

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risk. And this is um, it's a White House

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release, uh, that I'm quot from here. So

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it's, it's definitely the official thing.

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Yeah. Wow.

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Andrew Dunkley: Should we be surprised by this though?

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Professor Fred Watson: Uh no, no we shouldn't. I mean actually

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we did get um. Was it Jared Isaacman, the

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uh, the new, relatively new head of

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NASA, who I think we covered this uh,

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quite a few months ago, talked about the idea

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of uh, using a uh, 100 kilowatt

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nuclear reactor on the lunar surface. Because

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that raises a few eyebrows. Uh, but it looks

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as though this is the first step in, in

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expediting that uh, to start small,

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maybe even the smallest 1kW it'll run an

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electric fire and uh,

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keep um, going upwards. Uh, there's an

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interesting uh, disparity in

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the sort of urgency of this though because

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um, the next paragraph of the White House

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release says the policy calls on the Defence

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Department to provide a briefing to the

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White House in 90 days on um, potential

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uses and payloads for space nuclear systems

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of varying power levels. The Pentagon will in

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the first year of the policy use its space

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nuclear funding to support NASA's efforts,

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then conduct its own competition for space

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nuclear power systems. I get the feeling here

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that there's going to be too many fingers in

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the pie and too many people deciding which

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companies are going to get the, you know,

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going to get the contracts to do this.

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Andrew Dunkley: The options for nuclear power these days

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are so much more,

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uh, available and simple. Like

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you can make very small nuclear power

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stations now. You can, you can build one

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that's, that's small enough just to service a

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town these days. You don't need these big

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complex setups anymore.

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So it probably is the logical way to go.

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Even though when you say the word nuclear,

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everybody sort of runs for the hills. Not

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that that would save them, but um,

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it's not, ah, as big and scary as people

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envisage. But um, it's, it's got bad

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press for a long, long time. So whenever you

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talk about nuclear power station or look what

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happened in Australia, um, we're so

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scared of it. We've never done it.

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Professor Fred Watson: And people think of Three Mile, Three Mile

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island in Chernobyl.

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Uh, and uh, yes. And the bottom line

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is that if things go wrong, you have a very

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big environmental problem. And uh, that would

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be the case.

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Andrew Dunkley: It's fukush.

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Professor Fred Watson: Yeah.

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Andrew Dunkley: With the earthquake and the tide and the

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tsunami. Yeah, that's so mess.

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Professor Fred Watson: Yes. So, uh, it is scary, I

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think. Um, but, but

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well, so I grew up in a country that, uh,

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pioneered nuclear power with the US

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and there are several nuclear power stations.

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Uh, I used to live not very far from one

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actually at uh, Torness in Scotland.

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Yes, I think it's Taunus. Uh, and

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look, everybody just regarded it as

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a normal power station. It was very much a

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low key thing. Uh, and you

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see statistics like there's more

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radiation comes from the natural emissions

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from rocks in the uk. If you go down to

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Cornwall, the rocks are basically radioactive

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there.

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Andrew Dunkley: Oh wow.

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Professor Fred Watson: There's radon in the atmosphere. Um, but it's

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at a level that humans can tolerate. Humans

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have been tolerating it for hundreds of

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thousands of years. And uh, that's.

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Andrew Dunkley: Yeah, you're exposed to radiation every time

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you walk outside.

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Professor Fred Watson: Well, that's right, you are. Yes. So, um, so

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it, it's got to be treated with respect.

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Um, I, I think what freaks people out

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though as well is the idea of sticking a

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nuclear reactor on top of a rocket and then

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sending it into space. And there was an

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accident, uh, with a. So just

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stepping back, uh, NAS, their

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RTGs, radioisotope

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thermal generator, thermoelectric generators,

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I think that's what it stands for. Uh, on

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several spacecraft, including the two

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Voyagers, I think the pioneers have got it as

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well. Um, the Curiosity, um,

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and um, Perseverance.

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Both have RTG power supplies. Uh,

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so that's uh, uh,

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a well trodden path. But there was an

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accident, I think it might have been in the

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80s with a spacecraft that was launched with

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something like an RTG on board and it did,

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uh, it went wrong. I can't remember

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the details but I think it was Canada that

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took the punch. And there was a lot of

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radioactive debris that got spread over

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very, very sparsely, uh,

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populated regions. Uh,

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literal fallout. Yes, that's right. Yes,

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exactly. Flaws out the sky. If I remember

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rightly. I'm digging up things from the past

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year, but I think that's the case and that

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clearly freaks people out. If you've got a

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launch that doesn't work, uh, what's going to

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happen?

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Andrew Dunkley: I imagine so. But uh, it certainly does ramp

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up the space race between the US and China.

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And you know, China's probably going to fall

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a bit behind here because I think they were

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trying to set up a coal fired power station

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on the moon. You know, it

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um, might m, might

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slow them down a bit.

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Professor Fred Watson: Yeah, China's doing pretty well. They are

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doing sustainability. Yeah, yeah, they are.

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Ah, but yeah, they do use a lot of coal

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still.

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Andrew Dunkley: Yeah, they do, they do. So this is probably

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going to happen and what other

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option would there be? That's the thing. I

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mean some people will say no, put up solar

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energy systems, but um,

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nuclear is probably a much more

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efficient way of doing it.

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Professor Fred Watson: Yeah, well for a start, you've got the

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baseline load. You're not worried about where

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the sun is in the sky. The idea

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of being at the south pole of the moon,

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which is where the focus is in terms

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of our uh, exploration of the moon.

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Uh, it puts a different slant

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on it because it means that you are looking

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at a very low sun altitude in the

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sky. Uh, the sun's coming in nearly

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horizontally. The sunlight, now that's not

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uh, as bad a thing on the moon as it would be

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on the Earth. The Earth, as the sun gets

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lower, it's going through a thicker and

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thicker layer of atmosphere. So its uh, power

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is attenuated. On the moon that doesn't

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happen because there ain't no atmosphere. But

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it does bring challenges for your solar

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panels. You know, you've got to build arrays

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that are almost vertical and if you're

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looking for a big structure, uh, then

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uh, it becomes different slightly different

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engineering, um, issue. Plus you've got to

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take all that stuff up there as well. You

267
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know, going up to the moon with arrays of

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solar panels in the spacecraft might not

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leave room for much else. Whereas a nuclear

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reactor of the kind that people are talking

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about would be relatively compact. I m mean,

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the RTG devices are, I think

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it's, is it 13 kilogrammes of, uh,

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plutonium that they have in them.

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They're about the size of a, you know,

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a tea urn or something like that. Or a drink

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serum. Yeah, yeah.

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Andrew Dunkley: It's much simpler than it was 20, 30,

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40, 50 years ago. And of course they're

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talking not only about the moon, but people,

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uh, on Mars, uh, they'll need power as well.

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Um, I know in the movie the Martian they used

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solar panels, but that Mars is a bit further

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away, so the solar panels probably wouldn't

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be as efficient.

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Professor Fred Watson: Exactly.

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Andrew Dunkley: Nuclear, um, power makes, Makes perfect

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sense. Uh, although, you know, solar energy

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is quite, um, well used

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in space. Artemis 2 used it.

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Professor Fred Watson: Um, that's correct, yes. Uh, and

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um, you know, thinking of the different

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spacecraft, the one that's got perhaps the

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most spectacular solar panels is Lucy, uh,

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spacecraft which is on its way to the Trojan

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asteroids. Uh, and that's got

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solar panels which are huge. And that's

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because you're going out to the asteroid belt

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and beyond. Actually you go into the orbit of

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Jupiter, which is where the Trojan asteroids

301
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hang out. Uh, so you need big solar

302
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panels to collect all the energy. Yeah.

303
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Andrew Dunkley: The other problem with solar panels on Mars

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would be dust, because it's

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a pretty grubby place.

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Professor Fred Watson: Yeah, that's what, um, probably brought an

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end to. Uh, so Spirit and Opportunity both

308
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had solar panels. Uh, and there were

309
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certainly times when the amount of dust was

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stopping the power generation. And uh, that

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was cleared by, uh, Willy Willies, as they're

312
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called. Uh, the um, dust

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devils. That's right. On Mars. Yeah.

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Andrew Dunkley: Fascinating.

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All right, so the um, the directive has

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been put to NASA to start working on this,

317
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uh, and it comes from the White House. So,

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um, it's all systems go and they hope to have

319
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something operational as soon as 20,

320
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28. So they're not mucking around. In fact, I

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think NASA, after this was released, were

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given one month to it.

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Professor Fred Watson: Uh, that's, uh, exactly right. That's the 30

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days that I mentioned.

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Andrew Dunkley: No mucking around.

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Professor Fred Watson: Get going.

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Andrew Dunkley: Yep. Uh, you can read all about

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it@spacenews.com.

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this is Space Nuts with Andrew Dunkley and

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Professor Fred Watson Watson.

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Space Nuts.

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Well, we mentioned the moon. We'll stick with

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the moon. This storey though has nothing to

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do with people on the moon. It's got uh,

335
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everything to do with people that are not on

336
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Earth or the Moon or, or Mars for that

337
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matter. Uh, they're out there somewhere.

338
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We're looking for them. We're talking about

339
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the search for extraterrestrial intelligence

340
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and the dark side of the moon. The far side

341
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of the moon is um, the best place

342
00:14:10.910 --> 00:14:11.750
to start looking.

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Professor Fred Watson: Uh, that's right. So we've been looking for

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this for 60 years

345
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and using ground, uh, based

346
00:14:21.110 --> 00:14:24.060
antennas here on planet Earth, uh,

347
00:14:24.310 --> 00:14:26.870
which are very, uh, very capable.

348
00:14:28.100 --> 00:14:30.080
Um, once the Square Kilometre Array

349
00:14:30.080 --> 00:14:32.440
Observatory comes on stream towards the end

350
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of the decade, uh, we'll have the

351
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finest, most capable radio

352
00:14:37.560 --> 00:14:40.480
telescope in the world, uh, which will not

353
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directly engage with SETI programmes, but

354
00:14:43.960 --> 00:14:46.680
it will uh, have the

355
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sensitivity to detect. Well the thing that

356
00:14:49.640 --> 00:14:51.480
my colleagues tell me is it'll detect an

357
00:14:51.480 --> 00:14:53.360
airport radar at 50 light years.

358
00:14:54.400 --> 00:14:56.800
So that's the kind of sensitivity

359
00:14:57.300 --> 00:14:59.820
uh, that you're talking about. Um, but

360
00:15:00.060 --> 00:15:02.180
the main problem with ground based, with

361
00:15:02.180 --> 00:15:05.020
Earth based uh, radio telescopes

362
00:15:05.100 --> 00:15:07.340
is that they're compromised by all the

363
00:15:07.660 --> 00:15:10.460
cacophony of radio signals that

364
00:15:10.460 --> 00:15:12.660
surrounds us. From your mobile phones, from

365
00:15:12.660 --> 00:15:15.460
broadcasts from people like you and

366
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me doing this, going out into the ether,

367
00:15:18.220 --> 00:15:21.020
WI fi routers, WI fi, uh, the whole thing,

368
00:15:21.020 --> 00:15:23.420
microwave ovens, it all provides this

369
00:15:23.900 --> 00:15:26.700
noisy radio background and that's not getting

370
00:15:26.700 --> 00:15:29.660
any better with the um, satellite mega

371
00:15:29.660 --> 00:15:32.640
constellations. Uh, I was in uh, a meeting

372
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yesterday. It's

373
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a meeting of the um, International

374
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Astronomical Union Centre, uh, for the

375
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protection of the dark and quiet sky from

376
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satellite interference. Uh, and it

377
00:15:45.880 --> 00:15:48.120
was um, you know one of the things that's

378
00:15:48.120 --> 00:15:51.040
raising anxiety is the idea of uh, Elon

379
00:15:51.040 --> 00:15:52.840
Musk's million satellites for

380
00:15:55.100 --> 00:15:57.880
um, orbital data centres and

381
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this mirror in the sky idea, sunlight on

382
00:16:00.320 --> 00:16:02.980
demand, that also has a million satel mirrors

383
00:16:02.980 --> 00:16:05.140
on it. So that's more for the optical

384
00:16:05.140 --> 00:16:07.220
astronomers. But it's all a concern,

385
00:16:07.920 --> 00:16:10.780
uh, and it basically is eroding our

386
00:16:10.780 --> 00:16:13.340
capability slowly but surely to

387
00:16:13.340 --> 00:16:16.020
detect uh, faint extraterrestrial

388
00:16:16.020 --> 00:16:18.980
signals. Uh, so that

389
00:16:18.980 --> 00:16:21.860
brings us to currently possibly

390
00:16:21.860 --> 00:16:24.820
the best place to do this sort of thing from

391
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which is the far side of the moon.

392
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Uh, and um, uh,

393
00:16:31.130 --> 00:16:34.010
we have one uh, spacecraft.

394
00:16:34.010 --> 00:16:36.530
By we, I mean humankind have one

395
00:16:36.530 --> 00:16:39.180
spacecraft on the far side of the moon. Uh,

396
00:16:39.180 --> 00:16:41.210
it is China's Chang' e 4,

397
00:16:41.880 --> 00:16:44.530
uh, which soft landed on the far side of the

398
00:16:44.530 --> 00:16:47.530
moon back in 2019. Can you believe it?

399
00:16:47.530 --> 00:16:50.370
It's been there uh, seven

400
00:16:50.370 --> 00:16:53.340
years. It's quite Extraordinary. Um,

401
00:16:53.340 --> 00:16:55.700
but uh, now that, that

402
00:16:56.220 --> 00:16:58.260
um. Spacecraft was not set up

403
00:16:58.840 --> 00:17:01.480
uh specifically for uh,

404
00:17:01.860 --> 00:17:04.620
looking for um, SETI search for

405
00:17:04.620 --> 00:17:07.140
extraterrestrial intelligence but

406
00:17:07.460 --> 00:17:09.860
it's got a low frequency radio

407
00:17:09.860 --> 00:17:12.500
spectrometer on board um that

408
00:17:12.740 --> 00:17:15.660
actually has been used to conduct the first

409
00:17:15.660 --> 00:17:18.620
ever SETI search from the lunar far

410
00:17:18.620 --> 00:17:21.060
side. Um and so the

411
00:17:21.300 --> 00:17:23.789
goal, uh, the idea

412
00:17:24.109 --> 00:17:26.749
is to use that equipment which is

413
00:17:26.749 --> 00:17:29.549
designed to do natural sciences

414
00:17:29.869 --> 00:17:32.349
but to look for those

415
00:17:32.760 --> 00:17:35.360
ah, technosignatures, uh

416
00:17:35.360 --> 00:17:38.020
technomarkers they're sometimes called, uh,

417
00:17:38.020 --> 00:17:40.549
which might suggest that you're getting a

418
00:17:40.549 --> 00:17:43.309
signal from an artificially generated

419
00:17:43.309 --> 00:17:45.469
source. And what you're really looking for

420
00:17:46.109 --> 00:17:48.680
are ah, periodic

421
00:17:49.340 --> 00:17:52.200
um, bursts of radiation with perhaps

422
00:17:52.200 --> 00:17:53.480
regular intervals

423
00:17:54.180 --> 00:17:57.080
um, that are not easily explained

424
00:17:57.640 --> 00:18:00.520
by natural processes. And you've got to

425
00:18:00.520 --> 00:18:03.480
think back to Jocelyn Bell Burnell and her

426
00:18:04.040 --> 00:18:06.200
discovery uh, of the first pulsar because

427
00:18:06.200 --> 00:18:08.840
that's what she saw. Narrow um, band.

428
00:18:09.120 --> 00:18:12.000
Um. Sorry, narrow uh, band

429
00:18:12.000 --> 00:18:14.890
in time signatures, uh, or

430
00:18:14.890 --> 00:18:17.450
bursts of radiation which we now know is the

431
00:18:17.450 --> 00:18:19.450
pulsar, the kind of light ass beam of

432
00:18:19.450 --> 00:18:22.170
radiation from the pulsar sweeping around and

433
00:18:22.170 --> 00:18:25.130
passing the earth. Um, she didn't know that

434
00:18:25.130 --> 00:18:27.490
then. So she wrote little green men in her

435
00:18:27.560 --> 00:18:30.450
uh. On her chart record of very,

436
00:18:30.450 --> 00:18:33.380
very famous words. Um,

437
00:18:33.490 --> 00:18:36.400
so that's what basically uh, the uh,

438
00:18:36.400 --> 00:18:39.210
Chang', E, um Low Frequency Radio

439
00:18:39.210 --> 00:18:41.850
Spectrometer has been looking for. Uh, and

440
00:18:41.850 --> 00:18:44.770
it's things that um, you know, that speak

441
00:18:44.770 --> 00:18:47.470
of an artificial generated source.

442
00:18:47.550 --> 00:18:50.470
And so um, what they've

443
00:18:50.470 --> 00:18:52.670
done, uh the scientists working on this,

444
00:18:52.880 --> 00:18:55.550
uh basically they built an algorithm

445
00:18:56.700 --> 00:18:58.990
uh that ah, uh trawled through the data

446
00:18:59.550 --> 00:19:02.270
looking for anything that might

447
00:19:02.670 --> 00:19:05.310
be artificial. With no

448
00:19:05.950 --> 00:19:08.350
credible candidates revealed,

449
00:19:08.800 --> 00:19:11.630
uh, nothing that couldn't be explained either

450
00:19:11.630 --> 00:19:14.420
by you know, natural phenomena or by

451
00:19:14.500 --> 00:19:16.100
instrument, uh, issues.

452
00:19:17.140 --> 00:19:20.100
Um, there's a nice comment though

453
00:19:20.100 --> 00:19:22.940
from uh, phys.org who is carrying this

454
00:19:22.940 --> 00:19:25.540
storey. Uh, this is,

455
00:19:25.780 --> 00:19:28.379
I'll quote this. This is not a failure, it is

456
00:19:28.379 --> 00:19:30.580
a beginning. As Carl Sagan once put it,

457
00:19:30.820 --> 00:19:33.740
absence of evidence is not evidence of

458
00:19:33.740 --> 00:19:35.940
absence. Brilliant. Really good point.

459
00:19:36.820 --> 00:19:39.620
Andrew Dunkley: I had a lot of time for Carl Sagan, uh, very

460
00:19:39.620 --> 00:19:42.330
wise man and um. Yeah, he uh, he did a lot

461
00:19:42.330 --> 00:19:45.020
for astronomy during his time. But um,

462
00:19:45.490 --> 00:19:48.410
that's a valid point and, and I suppose you

463
00:19:48.410 --> 00:19:50.410
and I have spoken about it in the past. The

464
00:19:50.410 --> 00:19:52.850
big problem is distance. There might,

465
00:19:53.330 --> 00:19:55.450
there might be civilizations out there that

466
00:19:55.450 --> 00:19:58.090
are advanced and capable of communication but

467
00:19:58.090 --> 00:20:00.170
they're so far away we will never hear from

468
00:20:00.170 --> 00:20:01.970
them. Maybe that.

469
00:20:02.050 --> 00:20:04.600
Professor Fred Watson: Yeah, um, that's right. Uh,

470
00:20:04.690 --> 00:20:07.410
and you know, and time is the other issue.

471
00:20:07.410 --> 00:20:09.690
It's a needle in A haystack both in distance

472
00:20:09.690 --> 00:20:11.930
and in time because you've got to hit your

473
00:20:11.930 --> 00:20:14.910
civil station just at the right time. Yes.

474
00:20:15.020 --> 00:20:17.950
Uh, when uh, they are uh, technologically

475
00:20:17.950 --> 00:20:19.590
enough to have airport radar, uh, for

476
00:20:19.590 --> 00:20:22.270
example, but haven't wiped themselves out

477
00:20:22.430 --> 00:20:23.830
because of the loonies that they've

478
00:20:23.830 --> 00:20:24.350
generated.

479
00:20:24.350 --> 00:20:26.270
Andrew Dunkley: Yeah, you're more, you're more likely to get

480
00:20:26.270 --> 00:20:29.110
a um, a tick tock of some

481
00:20:29.110 --> 00:20:31.590
kid doing a stupid raps hole. That's

482
00:20:31.590 --> 00:20:34.190
probably, that's what you'll get from,

483
00:20:35.150 --> 00:20:38.100
from an extraterrestrial intelligence, um.

484
00:20:38.100 --> 00:20:40.540
What, what, what I wonder

485
00:20:40.860 --> 00:20:43.100
is with the far side of the moon? Yes, it's

486
00:20:43.100 --> 00:20:45.860
radio silent, but does it cover enough

487
00:20:45.860 --> 00:20:48.060
of the spectrum of the universe to

488
00:20:48.860 --> 00:20:51.740
pick up something or is it fairly

489
00:20:51.740 --> 00:20:53.340
narrow in its scope?

490
00:20:53.900 --> 00:20:56.300
Professor Fred Watson: Do you mean in terms of direction or.

491
00:20:56.300 --> 00:20:58.060
Andrew Dunkley: Yeah, being able to pick something up.

492
00:20:58.060 --> 00:21:00.620
Professor Fred Watson: Has it got like a wide array? Yeah, I mean

493
00:21:00.620 --> 00:21:03.540
the far side of the moon, um, you know,

494
00:21:03.540 --> 00:21:06.020
if you plunk something on the equator of the

495
00:21:06.020 --> 00:21:08.840
moon on the far side over a month

496
00:21:08.840 --> 00:21:11.840
you cover the entire sky. If you're,

497
00:21:11.840 --> 00:21:14.440
yeah, if you're um, if your

498
00:21:14.860 --> 00:21:17.480
uh, equipment is broadband enough

499
00:21:17.560 --> 00:21:20.360
and all the SETI stuff is, it's got a very

500
00:21:20.360 --> 00:21:22.760
wide range of spectral, of uh, frequencies

501
00:21:22.760 --> 00:21:25.640
although they do tend to concentrate on

502
00:21:26.920 --> 00:21:29.440
what uh, we call the 21 centimetre line. This

503
00:21:29.440 --> 00:21:32.040
is the frequency, the specific frequency

504
00:21:32.040 --> 00:21:34.380
that's radiated by called hydrogen.

505
00:21:34.860 --> 00:21:37.300
Uh and they do tend to concentrate on that

506
00:21:37.300 --> 00:21:39.460
because everybody in the universe will be

507
00:21:39.460 --> 00:21:41.740
aware of that 21 centimetre

508
00:21:42.300 --> 00:21:44.860
uh, wavelength because

509
00:21:44.860 --> 00:21:47.580
that's called hydrogen. Which is the same

510
00:21:47.580 --> 00:21:48.140
everywhere.

511
00:21:48.300 --> 00:21:51.180
Andrew Dunkley: Yeah, makes sense. All right,

512
00:21:51.580 --> 00:21:54.220
fascinating. Um, storey, um, nothing yet.

513
00:21:54.380 --> 00:21:56.500
But that doesn't mean, that doesn't mean

514
00:21:56.500 --> 00:21:57.660
it'll always be nothing.

515
00:21:57.740 --> 00:22:00.420
Professor Fred Watson: So it's not evidence of

516
00:22:00.420 --> 00:22:01.420
absence. That's right.

517
00:22:01.520 --> 00:22:04.030
Andrew Dunkley: M exactly. You can read all about it as

518
00:22:04.030 --> 00:22:05.830
Fred Watson said at the phys

519
00:22:06.070 --> 00:22:08.550
phys.org website,

520
00:22:08.950 --> 00:22:11.270
this is Space Nuts Andrew Dunkley here with

521
00:22:11.350 --> 00:22:12.710
Professor Fred Watson Watson.

522
00:22:15.110 --> 00:22:17.190
Professor Fred Watson: Okay, we checked all four systems and

523
00:22:17.190 --> 00:22:19.920
Andrew Dunkley: being with a go, Space Nuts, our uh,

524
00:22:19.950 --> 00:22:22.950
final storey. Fred Watson brings uh, us back

525
00:22:22.950 --> 00:22:25.670
to that old debate about the Hubble

526
00:22:25.670 --> 00:22:28.630
tension. Now the Hubble tension is measured

527
00:22:28.630 --> 00:22:30.870
in two different ways and they come up with

528
00:22:30.870 --> 00:22:33.470
two different answers. And that's troubled

529
00:22:33.470 --> 00:22:36.030
people for a while. Although we did a storey

530
00:22:36.030 --> 00:22:38.070
not so long ago that suggested. Hang on a

531
00:22:38.070 --> 00:22:40.630
minute, the differences aren't uh, that

532
00:22:40.870 --> 00:22:43.350
significant. So they're probably both right

533
00:22:43.590 --> 00:22:46.270
if you allow for the um, you know, the, the

534
00:22:46.270 --> 00:22:49.070
variables. But this storey is saying.

535
00:22:49.070 --> 00:22:51.870
Hang on a minute, we, we think there's a

536
00:22:51.870 --> 00:22:52.390
better way.

537
00:22:53.750 --> 00:22:56.150
Professor Fred Watson: Yes, that's right. Uh, in

538
00:22:56.150 --> 00:22:58.950
Exactly. That it's all about. So

539
00:22:59.510 --> 00:23:02.460
let's just, uh, backtrack. What is the Hubble

540
00:23:02.460 --> 00:23:05.100
tension? Uh, so the

541
00:23:05.180 --> 00:23:07.840
expansion rate of the universe, uh,

542
00:23:07.840 --> 00:23:10.700
basically is a number that we was

543
00:23:10.700 --> 00:23:13.340
first measured by Edwin hubble back in 1929.

544
00:23:13.860 --> 00:23:15.900
Um, he got the wrong answer because he was

545
00:23:15.900 --> 00:23:17.860
only looking at a very small number of

546
00:23:17.860 --> 00:23:20.700
galaxies. But it comes about because, as

547
00:23:20.700 --> 00:23:23.700
you look at galaxies, ah, in the

548
00:23:23.700 --> 00:23:26.540
wider universe, uh, they get,

549
00:23:26.920 --> 00:23:29.350
um. Their velocity away from us

550
00:23:29.830 --> 00:23:31.990
is bigger the further away they are.

551
00:23:32.710 --> 00:23:34.510
And that comes about when you've got a

552
00:23:34.510 --> 00:23:36.830
universe that's expanding. That's the natural

553
00:23:36.830 --> 00:23:39.030
assumption and we've believed that ever

554
00:23:39.030 --> 00:23:41.590
since. Yeah. Excuse me. So.

555
00:23:42.550 --> 00:23:44.590
So, um, I've got a bit of Hubble tension in

556
00:23:44.590 --> 00:23:47.350
my chest there. Um, so that's how

557
00:23:47.430 --> 00:23:50.310
it's normally measured, measured the Hubble

558
00:23:50.310 --> 00:23:52.710
constant, this number,

559
00:23:53.110 --> 00:23:56.030
which is in slightly bizarre units, it's

560
00:23:56.030 --> 00:23:58.390
in megapas, uh, kilometres per second per

561
00:23:58.390 --> 00:24:01.090
megaparsec. Kilometres per second is

562
00:24:01.090 --> 00:24:04.050
the recession speed of a galaxy.

563
00:24:04.450 --> 00:24:06.210
A megaparsec is,

564
00:24:07.000 --> 00:24:09.890
uh, it 3.26. I can never remember the

565
00:24:09.890 --> 00:24:11.410
name. Million light years.

566
00:24:12.850 --> 00:24:14.810
It's the units that astronomers use for

567
00:24:14.810 --> 00:24:17.410
measuring distance parsecs. And it's a

568
00:24:17.410 --> 00:24:20.370
million parsecs. So, um, kilometres

569
00:24:20.370 --> 00:24:23.250
per second per megaparsec tells you how

570
00:24:23.250 --> 00:24:25.770
the velocity of a galaxy

571
00:24:25.770 --> 00:24:28.570
increases with distance and that's the

572
00:24:28.570 --> 00:24:30.290
result of the expansion of the universe. So

573
00:24:30.290 --> 00:24:33.270
the Hubble constant tells you how fast the

574
00:24:33.270 --> 00:24:35.070
universe is expanding. Now,

575
00:24:35.950 --> 00:24:38.870
now you can. The normal way of

576
00:24:38.870 --> 00:24:41.750
doing this is, uh. And it's actually why the

577
00:24:41.750 --> 00:24:44.470
Hubble telescope was created and why it got

578
00:24:44.470 --> 00:24:47.349
its name. Uh, we. Excuse me, we

579
00:24:47.349 --> 00:24:50.310
measure the brightness. Sorry, I've

580
00:24:50.310 --> 00:24:52.110
got my. Got my tension back there.

581
00:24:53.630 --> 00:24:55.630
If you want to cut this bit out, Huw, you're

582
00:24:55.630 --> 00:24:56.670
more than welcome to,

583
00:24:58.720 --> 00:25:01.070
um. It's fine now, uh,

584
00:25:02.080 --> 00:25:05.010
uh, the tension comes about. So, no, let me

585
00:25:05.010 --> 00:25:07.890
step back again. The measure, uh, where

586
00:25:07.890 --> 00:25:10.770
it's measured is you build up a sort of

587
00:25:10.770 --> 00:25:12.610
distance scale ladder. So the direct

588
00:25:12.610 --> 00:25:15.610
measurement of star distances in outer

589
00:25:15.610 --> 00:25:18.250
space comes about by the parallax

590
00:25:18.250 --> 00:25:21.090
method. As the Earth goes around the sun, we

591
00:25:21.090 --> 00:25:24.090
see stars, uh, apparently changing their

592
00:25:24.090 --> 00:25:26.970
position relative to very distant

593
00:25:26.970 --> 00:25:29.390
background stars. And that changing position

594
00:25:29.390 --> 00:25:31.910
you can measure. Uh, and in fact

595
00:25:31.990 --> 00:25:34.270
it's that. That gives the parsec its name.

596
00:25:34.270 --> 00:25:37.230
It's a parallax of 1/ arc second is what

597
00:25:37.230 --> 00:25:39.510
it's short for. And so that's a direct

598
00:25:39.910 --> 00:25:42.230
geometrical way of measuring the distance to

599
00:25:42.230 --> 00:25:44.989
certain stars. If you can do that to

600
00:25:44.989 --> 00:25:47.270
stars whose intrinsic brightness, you know,

601
00:25:47.590 --> 00:25:49.910
and these are typically, uh, Cepheid variable

602
00:25:49.910 --> 00:25:52.590
stars, then you can extend it because you

603
00:25:52.590 --> 00:25:54.910
know their brightness, uh, their intrinsic

604
00:25:54.910 --> 00:25:57.110
brightness, how much uh, light they radiate,

605
00:25:57.660 --> 00:25:59.580
then you can look at how faint they are

606
00:25:59.660 --> 00:26:02.220
further and further on. Um, and that's the,

607
00:26:02.220 --> 00:26:04.540
that's how we started off because Hubble

608
00:26:05.500 --> 00:26:08.500
measured um, um. In fact in

609
00:26:08.500 --> 00:26:11.180
1923 used these variable stars to

610
00:26:11.180 --> 00:26:12.500
measure the distance of the Andromeda, um,

611
00:26:12.940 --> 00:26:15.100
galaxy. Once again, he got it a bit wrong by

612
00:26:15.100 --> 00:26:17.700
today's standards. But that uh, was when we

613
00:26:17.700 --> 00:26:19.580
realised that galaxies weren't little things

614
00:26:19.580 --> 00:26:22.260
frutaling around in our own Milky Way. They

615
00:26:22.260 --> 00:26:25.030
are very distant objects. So, so that's the

616
00:26:25.030 --> 00:26:27.950
basic process and that has now been

617
00:26:28.500 --> 00:26:31.470
uh, basically elaborated by

618
00:26:31.550 --> 00:26:34.470
additional things which involve supernovae,

619
00:26:34.470 --> 00:26:37.150
the exploding stars, all sorts of other

620
00:26:37.600 --> 00:26:40.309
uh, cosmic phenomena. And that's the

621
00:26:40.309 --> 00:26:43.230
basis of what this storey is about

622
00:26:43.710 --> 00:26:46.030
because uh, that

623
00:26:46.430 --> 00:26:48.430
technology has now been

624
00:26:49.070 --> 00:26:51.630
absolutely refined to the nth degree,

625
00:26:52.180 --> 00:26:55.140
uh, by the scientists who are uh,

626
00:26:55.200 --> 00:26:57.800
uh, who are um, um,

627
00:26:57.800 --> 00:27:00.710
basically reporting this work. It's

628
00:27:00.710 --> 00:27:03.390
a study in astronomy and astrophysics, one of

629
00:27:03.390 --> 00:27:05.310
the leading journals, actually a European

630
00:27:05.310 --> 00:27:08.150
journal. Uh, and these scientists

631
00:27:08.150 --> 00:27:10.590
have spent a lot of time

632
00:27:11.310 --> 00:27:14.270
getting uh, the answer right from

633
00:27:14.270 --> 00:27:16.430
this method, what we call the distance ladder

634
00:27:16.430 --> 00:27:19.230
or the distance scale, by invoking

635
00:27:19.550 --> 00:27:22.130
objects of all kinds. And so they

636
00:27:22.370 --> 00:27:24.930
have produced a number for the Hubble

637
00:27:24.930 --> 00:27:27.650
constant which has a very, very

638
00:27:28.130 --> 00:27:30.840
small error. In fact they quote it as Ah,

639
00:27:30.890 --> 00:27:32.770
73.50

640
00:27:33.570 --> 00:27:36.210
kilometres per second per megaparsec

641
00:27:36.450 --> 00:27:39.050
plus or minus point zero, sorry,

642
00:27:39.050 --> 00:27:42.010
0.81 kilometres per

643
00:27:42.010 --> 00:27:44.650
second per megaset parsec. So they're talking

644
00:27:44.650 --> 00:27:47.210
about something that's either somewhere

645
00:27:47.210 --> 00:27:50.210
between 72.0 and 74. Sorry,

646
00:27:50.210 --> 00:27:52.510
72.5 and 74. 4.5

647
00:27:52.510 --> 00:27:55.030
thereabouts, which is a very, very

648
00:27:55.110 --> 00:27:57.990
tight uh, estimate of this

649
00:27:57.990 --> 00:28:00.990
velocity. Uh, so what's

650
00:28:00.990 --> 00:28:03.710
the tension about until somebody debunks

651
00:28:03.710 --> 00:28:06.370
them? Yeah, uh,

652
00:28:06.630 --> 00:28:09.030
well, it's true. Um, I do remember,

653
00:28:09.630 --> 00:28:11.830
um, back in the 70s, and I've told you this

654
00:28:11.830 --> 00:28:14.510
before, Andrew, there were two schools of

655
00:28:14.510 --> 00:28:17.310
thought, both offering measurements with very

656
00:28:17.310 --> 00:28:19.870
tight error limits, one of which said that

657
00:28:19.870 --> 00:28:22.100
the number was 50 and the other which said

658
00:28:22.100 --> 00:28:25.100
the number was 100. And lo and behold, when

659
00:28:25.100 --> 00:28:26.660
the Hubble telescope gave us the right

660
00:28:26.660 --> 00:28:28.700
answer, it was basically the average of those

661
00:28:28.700 --> 00:28:31.180
two around about 75. And it's now been

662
00:28:31.180 --> 00:28:31.700
refined.

663
00:28:31.780 --> 00:28:33.300
Andrew Dunkley: It's kind of what they're doing with this,

664
00:28:33.300 --> 00:28:33.860
isn't it?

665
00:28:34.580 --> 00:28:37.260
Professor Fred Watson: A little bit. Although they're really giving

666
00:28:37.260 --> 00:28:39.060
tight, very tight

667
00:28:39.510 --> 00:28:42.460
um, estimates based on everything that

668
00:28:42.460 --> 00:28:45.140
we can observe. Uh, whereas the previous

669
00:28:45.380 --> 00:28:47.780
this with the difference between 50 and 100

670
00:28:47.780 --> 00:28:49.820
and that was a kind of Hubble tension. We

671
00:28:49.820 --> 00:28:51.350
didn't call it the ah, that but that's sort

672
00:28:51.350 --> 00:28:54.070
of what it was. That was uh, based on

673
00:28:54.760 --> 00:28:57.350
uh, just individual, individual measurements

674
00:28:57.510 --> 00:29:00.350
from you know, their own particular school of

675
00:29:00.350 --> 00:29:02.830
thought. One was galaxies, one was supernovae

676
00:29:02.830 --> 00:29:04.310
or something. I can't remember how it worked,

677
00:29:04.310 --> 00:29:06.030
I can't remember the details. Probably could

678
00:29:06.030 --> 00:29:08.550
if I thought about it. Uh, but this brings

679
00:29:08.550 --> 00:29:11.350
them all together to get this super accurate

680
00:29:11.670 --> 00:29:14.310
so called value of 73.5.

681
00:29:14.790 --> 00:29:17.740
So the tension is that there is another way

682
00:29:18.220 --> 00:29:21.020
of determining uh, the Hubble

683
00:29:21.020 --> 00:29:23.900
constant and it involves uh, observing

684
00:29:23.900 --> 00:29:26.100
the cosmic microwave background radiation.

685
00:29:26.100 --> 00:29:28.620
That's the radiation that we see from the Big

686
00:29:28.620 --> 00:29:31.020
Bang. We're looking back 13.8 billion years

687
00:29:31.340 --> 00:29:33.900
to see that. What's sometimes called the

688
00:29:33.900 --> 00:29:35.900
afterglow of the Big Bang. It's really still

689
00:29:35.900 --> 00:29:37.540
the light of the Big Bang that you can see

690
00:29:37.540 --> 00:29:39.500
because you're looking so far back in time.

691
00:29:40.140 --> 00:29:43.140
And that gives us a different number. You

692
00:29:43.140 --> 00:29:46.040
can look at the, the, it's what's

693
00:29:46.040 --> 00:29:47.960
called the power spectrum. The cosmic

694
00:29:47.960 --> 00:29:49.800
microwave background radiation has these

695
00:29:49.800 --> 00:29:52.760
tiny, tiny fluctuations and by tiny

696
00:29:52.760 --> 00:29:54.960
I mean the amount fluctuations in

697
00:29:54.960 --> 00:29:56.560
temperature. You can measure the temperature

698
00:29:56.560 --> 00:29:59.560
of the radiation and they form in little

699
00:29:59.560 --> 00:30:02.480
blobs and we think that's where the galaxies

700
00:30:02.480 --> 00:30:04.320
came from. The cooler parts were where

701
00:30:04.320 --> 00:30:07.280
galaxies formed, the warmer parts were not.

702
00:30:07.700 --> 00:30:10.440
Uh, and so the microwave

703
00:30:10.440 --> 00:30:12.160
background radiation when you look at,

704
00:30:13.720 --> 00:30:16.580
looks like a wallpaper, uh, which is

705
00:30:16.580 --> 00:30:18.700
why I sometimes call it the cosmic wallpaper.

706
00:30:18.780 --> 00:30:20.620
Partly because it's behind everything else.

707
00:30:20.620 --> 00:30:22.540
Just like the wallpaper in a room is behind

708
00:30:22.540 --> 00:30:25.300
everything. But it's also got these patterns.

709
00:30:25.300 --> 00:30:27.820
So you can use those patterns to make another

710
00:30:27.900 --> 00:30:30.460
estimate of the uh, Hubble

711
00:30:30.460 --> 00:30:30.940
constant.

712
00:30:30.940 --> 00:30:33.820
And the answer that you get is 67

713
00:30:33.820 --> 00:30:36.620
kilometres per second per megaparsec, which

714
00:30:36.620 --> 00:30:39.260
is well outside the error

715
00:30:39.260 --> 00:30:41.920
band of the sort of traditional method.

716
00:30:41.990 --> 00:30:44.990
Method. And so I think

717
00:30:44.990 --> 00:30:47.830
what the direction this is going

718
00:30:47.830 --> 00:30:50.750
in is. So uh, as you and I have

719
00:30:50.750 --> 00:30:53.390
spoken about before, people have done a lot

720
00:30:53.390 --> 00:30:56.230
of work to try and look for where we've

721
00:30:56.230 --> 00:30:58.109
gone wrong here because these two numbers

722
00:30:58.109 --> 00:30:59.750
should give you the same answer. But they

723
00:30:59.750 --> 00:31:02.750
don't. But they don't. So

724
00:31:02.750 --> 00:31:04.590
now people are turning it upside down and

725
00:31:04.590 --> 00:31:06.790
saying maybe the fact that they don't give

726
00:31:06.790 --> 00:31:08.470
the same answer is telling us something

727
00:31:08.470 --> 00:31:10.330
about, about the physics of the universe that

728
00:31:10.330 --> 00:31:11.050
we don't know

729
00:31:12.810 --> 00:31:14.690
Andrew Dunkley: or we're just not accounting for everything

730
00:31:14.690 --> 00:31:16.610
we need to put into the formula.

731
00:31:16.610 --> 00:31:19.370
Professor Fred Watson: Yeah, yeah there's that too. And, but I think

732
00:31:19.370 --> 00:31:22.090
that's. So as time goes on people are ticking

733
00:31:22.090 --> 00:31:24.570
off all those things uh, simply because

734
00:31:24.730 --> 00:31:27.290
there's a lot more work being done on this

735
00:31:27.290 --> 00:31:29.930
topic. So the Hubble tension could turn out

736
00:31:29.930 --> 00:31:32.730
to be, uh, the gateway

737
00:31:32.890 --> 00:31:35.730
into new physics. That might tell us about

738
00:31:35.730 --> 00:31:38.170
dark matter and dark energy and all the other

739
00:31:38.170 --> 00:31:41.100
dark stuff that we think about. Yeah.

740
00:31:41.180 --> 00:31:44.060
So it's potentially, uh, something

741
00:31:44.060 --> 00:31:46.660
that I think, uh, scientists everywhere will

742
00:31:46.660 --> 00:31:49.400
keep an eye on. But, uh, it is really, um,

743
00:31:49.400 --> 00:31:51.620
really, uh, in many ways getting quite

744
00:31:51.620 --> 00:31:53.460
exciting that this Hubble tension is not

745
00:31:53.460 --> 00:31:55.420
going away. No, definitely not.

746
00:31:55.420 --> 00:31:57.780
Andrew Dunkley: It's come up a few times in the last 10 years

747
00:31:57.780 --> 00:31:59.940
that we've been doing this. So they keep

748
00:31:59.940 --> 00:32:01.620
looking at it and that's. And very good

749
00:32:01.620 --> 00:32:04.220
reasons to do so. Uh, for the record, a

750
00:32:04.220 --> 00:32:07.190
megaparsec is approximately 3.0 million light

751
00:32:07.190 --> 00:32:08.710
years. I think that's what you said.

752
00:32:08.870 --> 00:32:10.630
Professor Fred Watson: It is what I said. Yeah. I could never

753
00:32:10.630 --> 00:32:12.150
remember. I think it's 3.26.

754
00:32:12.150 --> 00:32:14.510
Andrew Dunkley: I thought that's what I found. Yes.

755
00:32:14.510 --> 00:32:15.990
Professor Fred Watson: Yeah. Very good.

756
00:32:16.070 --> 00:32:18.070
Andrew Dunkley: All right, uh, hopefully they've finally

757
00:32:18.070 --> 00:32:20.750
cracked the Hubble tension debate. Uh, I

758
00:32:20.750 --> 00:32:22.470
guess we'll find out if they keep coming up

759
00:32:22.470 --> 00:32:24.310
with different numbers in, in the future.

760
00:32:24.630 --> 00:32:26.100
But, uh, you can look it up@, uh,

761
00:32:26.100 --> 00:32:28.390
dailygalaxy.com or you can read the

762
00:32:28.550 --> 00:32:30.830
published paper at Astronomy and

763
00:32:30.830 --> 00:32:31.830
Astrophysics.

764
00:32:32.710 --> 00:32:34.110
Fred Watson, that brings us to the end of the

765
00:32:34.110 --> 00:32:35.350
programme. Thank you so much.

766
00:32:36.310 --> 00:32:38.750
Professor Fred Watson: A great pleasure, Andrew. Uh, we've covered

767
00:32:38.750 --> 00:32:41.510
some great topics today and, uh, it's always

768
00:32:41.510 --> 00:32:42.150
a delight.

769
00:32:42.470 --> 00:32:45.190
Andrew Dunkley: Yeah, it's very. A few different types of

770
00:32:45.270 --> 00:32:47.670
storeys this time around, which we like.

771
00:32:48.070 --> 00:32:49.590
We'll catch you on the next one, Fred Watson.

772
00:32:50.550 --> 00:32:52.310
Professor Fred Watson: I guess we will. Yes. Sounds good.

773
00:32:52.550 --> 00:32:54.350
Andrew Dunkley: Professor Fred Watson Watson, astronomer at

774
00:32:54.350 --> 00:32:56.310
large. And thanks to Huw in the studio. He

775
00:32:56.310 --> 00:32:58.710
couldn't be with us today because he caused a

776
00:32:58.710 --> 00:33:01.410
bit of, of hubby tension at home

777
00:33:03.010 --> 00:33:04.930
and he's been sent to the naughty corner.

778
00:33:05.490 --> 00:33:08.380
Don't, uh, forget to visit us online or, um,

779
00:33:08.380 --> 00:33:10.330
visit, uh, us on social media. And don't

780
00:33:10.330 --> 00:33:12.490
forget to send us your comments and questions

781
00:33:12.490 --> 00:33:13.690
via, uh, our website, space

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00:33:13.690 --> 00:33:16.010
nutspodcast.com or

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00:33:16.010 --> 00:33:19.010
spacenuts IO and, uh, leave

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reviews from your favourite podcasting

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00:33:21.050 --> 00:33:23.530
platform in the meantime, from me, Andrew

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Dunkley. Thanks for your company. We'll see

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you on the very next episode of Space Nuts.

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Professor Fred Watson: Bye. Bye.

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00:33:28.890 --> 00:33:31.090
Andrew Dunkley: You've been listening to the Space Nuts

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00:33:31.090 --> 00:33:34.050
podcast, available at

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00:33:34.050 --> 00:33:36.010
Apple Podcasts, Spotify,

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00:33:36.250 --> 00:33:38.970
iHeartRadio or your favourite podcast

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00:33:38.970 --> 00:33:40.650
player. You can also stream on

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00:33:40.650 --> 00:33:42.410
demand@bytes.com.

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Professor Fred Watson: this has been another quality podcast

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00:33:44.770 --> 00:33:46.890
production from bytes.com.