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<v Speaker 1>Hi, there, Andrew Duncley again with another episode of Space Nuts,

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<v Speaker 1>and it's good to have your company. This is a

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<v Speaker 1>Q and A edition. This is where we answer your

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<v Speaker 1>questions if we can. If we can't, we just pretend to.

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<v Speaker 1>We've got questions about light and redshift. Today we're also

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<v Speaker 1>going to talk gas giants, expansion of the galaxy versus

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<v Speaker 1>or expansion of the universe versus galaxy collisions, and a

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<v Speaker 1>future of navigation reference points. How are we going to

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<v Speaker 1>do that? When we start going further and further out,

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<v Speaker 1>those questions will be answered or they'll be faked. We're

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<v Speaker 1>not sure yet. Deep fake radio coming up soon on

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<v Speaker 1>this edition of Space Nuts fifteen seconds. Guidance is in

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<v Speaker 1>channel ten nine ignition sequence Space Nuts or three two.

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<v Speaker 2>One Space Nuts.

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<v Speaker 1>As can I report it?

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<v Speaker 2>Neils good and.

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<v Speaker 1>He's here again, like a fly on a piece of meat.

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<v Speaker 1>Hello Fred, Thanks so do Thanks professor Fred. What's an

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<v Speaker 1>astronomer at large? Nice to see you.

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<v Speaker 2>Yeah, that's right, it's nice to see you too. I

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<v Speaker 2>think I.

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<v Speaker 1>Have enough digs at Hugh. I thought maybe I.

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<v Speaker 2>Should just should That's fine.

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<v Speaker 1>Land a left hook for a change. It always comes

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<v Speaker 1>back and hits me. Though eventually, so, yeah, I can't

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<v Speaker 1>take it.

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<v Speaker 3>I'm tough.

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<v Speaker 1>Let's let's go straight to our questions. Our first question today,

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<v Speaker 1>Fred comes from Mario in Melbourne. He likes to go

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<v Speaker 1>go karting. Hi, Fred and Andrew, hoping you can help

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<v Speaker 1>explain why if light itself doesn't experience time, how can

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<v Speaker 1>it redshift? Doesn't red shifting imply it changes somehow, which

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<v Speaker 1>implies it must have been subject to time. Or is

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<v Speaker 1>this some sort of relativity witchcraft where we as observers

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<v Speaker 1>experience time and the red shift, but the photon itself

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<v Speaker 1>somehow in all states it can be simultaneously or something

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<v Speaker 1>like that. Yeah, simultaneously or something like that. Appreciate you

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<v Speaker 1>unscrambling my brain on this one. Still listening from the

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<v Speaker 1>far start keep up the great show, Mario from Melbourne.

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<v Speaker 1>I think we've kind of had variations of this question

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<v Speaker 1>come up in the past. People sort of have trouble

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<v Speaker 1>differentiating between light and time and what's going on out there.

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<v Speaker 1>Can you shed some light on this one for it?

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<v Speaker 2>I'm sorry, I'm completely in the dark about this one.

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<v Speaker 2>It's a good point though, and so it's made me.

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<v Speaker 2>You know, it's got the old cogs working to try

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<v Speaker 2>and work out what's happening. Because that's right. Because light

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<v Speaker 2>travels at the speed of light to the fastest speed

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<v Speaker 2>anything could travel through the universe, it does not experience time.

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<v Speaker 2>A photon of light does not experience time, and yet

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<v Speaker 2>they change. And you're right, Mario is correct that we

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<v Speaker 2>do see photons changing because the photons that we are

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<v Speaker 2>now receiving from distant galaxy, for example, are highly red shifted.

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<v Speaker 2>They've become ready photons. Now, what that corresponds to is

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<v Speaker 2>a loss of energy, which results from the expansion of

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<v Speaker 2>the universe. And so I think I'm right in saying

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<v Speaker 2>that the photon doesn't notice that. It doesn't know that

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<v Speaker 2>it's lost energy because it doesn't experience time. So I

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<v Speaker 2>think you know, in a sense the loss of energy,

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<v Speaker 2>which by the way, just filters out into the universe.

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<v Speaker 2>Apparently normally that's where it goes. It's I think that

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<v Speaker 2>is a property of the observer, the fact that we're

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<v Speaker 2>observing this thing. The photon, the best of my understanding,

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<v Speaker 2>doesn't care it arrives at the same time as it

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<v Speaker 2>left because it doesn't experience time. But it might be

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<v Speaker 2>surprised that where the place where it arrived at is

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<v Speaker 2>very different from the place where it left out in

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<v Speaker 2>terms of the energy balance and what's happening there. I'm

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<v Speaker 2>not sure whether I'm making much sense here, Mario, but

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<v Speaker 2>that's my understanding of the situation.

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<v Speaker 1>Okay, it is a bit complicated. It'd be nice to

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<v Speaker 1>be a photon if you're doing a long haul flight,

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<v Speaker 1>because if you didn't experienced time, you wouldn't have to

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<v Speaker 1>worry about it twenty hour flight to Turkey, for example,

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<v Speaker 1>or anything like that. Yes, this is weak, yeah all over. Yeah,

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<v Speaker 1>we hope we unscrambled your brain, Mario, because it is

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<v Speaker 1>a bit of a scrambling issue. But photons don't experience time,

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<v Speaker 1>and they don't know that they're losing energy. It's sort

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<v Speaker 1>of like old people.

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<v Speaker 2>Yep, yep, go to health. I probably you should say that,

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<v Speaker 2>though you know. Now look I can vouch for that.

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<v Speaker 3>I'm starting to.

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<v Speaker 1>Experience that myself. Yes, thanks, Mario. Let's move on to

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<v Speaker 1>our next one. This comes from Nugel.

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<v Speaker 4>Oh friend Andrew, this is Nigel from Brisbane, Australia. I

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<v Speaker 4>have two questions about our gas giants, Jupiter and Satin.

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<v Speaker 4>I want to know beneath all that gas. Is there

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<v Speaker 4>a rocky planet and if so, how big are they

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<v Speaker 4>in relation to the Earth? Okay, thank you, love the show.

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<v Speaker 3>Keep up the good work, thanks Nigel.

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<v Speaker 1>Yeah, look, its.

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<v Speaker 3>Theory, isn't it.

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<v Speaker 1>Fred. We don't know for sure what's down deep in

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<v Speaker 1>those gas giants, but there might be something.

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<v Speaker 2>Well, you've absolutely answered the question, Andrew.

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<v Speaker 1>Okay, we'll move on to the next one from Raoul.

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<v Speaker 2>Nigel's question is you know it's one that many astronomers

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<v Speaker 2>and plunge your scientists ask because we don't know, we

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<v Speaker 2>don't know the answer. The modeling suggests that, because of

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<v Speaker 2>the way we believe planets are formed, that there should

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<v Speaker 2>be a rocky core underneath all that gas, that it

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<v Speaker 2>should be quite massive, maybe with a fair degree of

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<v Speaker 2>a water ice involved with it as well. Although some

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<v Speaker 2>of the papers that I've read suggest that there might

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<v Speaker 2>be something called metallic hydrogen at the center of these

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<v Speaker 2>gas giants. I'm not sure what that means. Probably mean

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<v Speaker 2>hydrogen in a state where it can conduct electricity. So yeah,

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<v Speaker 2>so that's it's a question that's really at the forefront

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<v Speaker 2>of knowledge. So you and me both, Nigel, I wonder

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<v Speaker 2>what's at the center of these gas giants and how

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<v Speaker 2>big the central core might be if there is one,

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<v Speaker 2>which we assume there is.

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<v Speaker 1>Yeah, I mean guess giants to a certain degree. What

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<v Speaker 1>could have been stars had their formation happened in a bigger,

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<v Speaker 1>better way. At what point do they reach in size

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<v Speaker 1>or structure where they wouldn't have a solid core? Like

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<v Speaker 1>would a brown dwarf? How does have a solid core?

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<v Speaker 2>Perhaps, Yeah, that's certainly a brown dwarf would have a core,

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<v Speaker 2>and it probably wouldn't be solid either, similar to more

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<v Speaker 2>similar to what the Sun's core we think is like,

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<v Speaker 2>compared with what a planet's core is like. So brown

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<v Speaker 2>dwarf has nuclear reactions taking place, but they're low level.

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<v Speaker 2>Once they're something called deuterium burning, and that doesn't generate

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<v Speaker 2>anything like the same amount of heat as the hydrogen

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<v Speaker 2>process that is going on at the center of our sun.

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<v Speaker 2>So at the center of the Sun, you've got this

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<v Speaker 2>ball of energy, very very hot, radiating gamma ray photons

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<v Speaker 2>out which eventually find their way as a visible light

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<v Speaker 2>out to the surface. The brown dwarf, you've got low

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<v Speaker 2>level radiation which finds its way to the surface. With

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<v Speaker 2>a gas giant, though we don't know that's the thing.

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<v Speaker 2>We really don't know what the core would below.

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<v Speaker 1>That.

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<v Speaker 2>The thinking is that that they are cold enough to

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<v Speaker 2>have a solid core. You know that you're not talking

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<v Speaker 2>about a ball of energy. But we do know again

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<v Speaker 2>that there are nuclear actions taking place. For example, in

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<v Speaker 2>the core of Jupiter Jupiter radio is at one point

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<v Speaker 2>eight times more heat than it receives from the salt

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<v Speaker 2>that's coming from maybe uranium fission or something like that

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<v Speaker 2>happening down there in its interior.

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<v Speaker 1>Wow, do they have a theory if Jupiter has a core?

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<v Speaker 1>Do they have a theory on how big it is

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<v Speaker 1>compared worth?

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<v Speaker 2>Probably? But look, I'm going to take as take a

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<v Speaker 2>punt and say yes, people probably do think it is

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<v Speaker 2>about the size of Earth. I'm sure that kind of

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<v Speaker 2>suggestion before. I just remember Jupiter's about eleven times the

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<v Speaker 2>diamature of Earth.

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<v Speaker 1>Yeah. Wow, all right, jury is still out, Nigel, but

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<v Speaker 1>it maybe could be done. Oh type of scenario. Thanks

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<v Speaker 1>for the question. Sorry, nothing to do with us, nothing

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<v Speaker 1>to see here. This is space Sandred Duntley with Fred Watson,

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<v Speaker 1>Professor Astronomer at Large. Great guy, Now let's take a

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<v Speaker 1>little break from the show to tell you about our

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<v Speaker 2>Three Space Nuts.

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<v Speaker 1>Okay, our next question, Fred comes from Raoul.

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<v Speaker 3>Hi, guys, Raoul from California here and a big Chelsea fan.

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<v Speaker 3>I know you were talking about American football, but I

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<v Speaker 3>do like europeanotball. Had a question for you. If the

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<v Speaker 3>universe is ever expanding from the Big Bang, then all

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<v Speaker 3>the galaxies will be moving apart from each other. But

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<v Speaker 3>I recall seeing on a show that galaxies could one

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<v Speaker 3>day collide. Does that mean that the universe is stopping

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<v Speaker 3>its expansion or slowing its expansion, allowing the gravity of

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<v Speaker 3>galaxies to then collide. And if that is the case,

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<v Speaker 3>will the universe one day stop expanding and start to

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<v Speaker 3>contract upon whatever the hugest big black hole in the

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<v Speaker 3>middle of the universe really is. Thanks a lot, you

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<v Speaker 3>guys do great love listening to it. Beat the show.

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<v Speaker 1>I love what you did, right, Thank you, David Chelsea.

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<v Speaker 1>Oh sorry, yeah, David, next roll roll thanks for that. Yes,

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<v Speaker 1>Chelsea fan, but yeah, we'll forgive you for that. I'm

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<v Speaker 1>a Liverpool fan myself. Do you follow English Premier League?

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<v Speaker 2>Most League slightly? Yeah? Only you know some of the

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<v Speaker 2>bigger teams. I've was interested in what they're doing. I've

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<v Speaker 2>got a son in law and a grand couple of

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<v Speaker 2>grandsons who are absolutely mad Manchester United freaks, and you know,

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<v Speaker 2>various various other football teams. I never really got heavily

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<v Speaker 2>into football. I can never remember which I was supposed

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<v Speaker 2>to be kicking the balls and it wasn't nice team really,

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<v Speaker 2>But yeah, that takes an interest.

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<v Speaker 1>Yeah, I played soccer for ten years, never won a thing.

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<v Speaker 1>I didn't even win the Raffle anyway. Raoul's asking about

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<v Speaker 1>the universe and his expansion versus galaxy collisions basically, and

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<v Speaker 1>is the expansion slowing or stopping? And is that why

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<v Speaker 1>galaxies are going to crash into each other? Is it

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<v Speaker 1>all going to sort of fall back into a giant

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<v Speaker 1>black hole in the middle. We've had variations of questions

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<v Speaker 1>like this over the years. It's one that always spawns

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<v Speaker 1>a lot of interest.

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<v Speaker 2>It does, doesn't it. And there are actually two things

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<v Speaker 2>going on here. I think in rolls question because it's

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<v Speaker 2>quite right that some galaxies do collide with each other,

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<v Speaker 2>but in fact we are in poor position for a

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<v Speaker 2>collision with Andromeda that might already be happening.

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<v Speaker 1>In fact, yeah, in fact, yeah, we talked about it

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<v Speaker 1>the other day. They're actually sort of you know, tickling

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<v Speaker 1>their fingertips at the moment because of their giant gas balls.

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<v Speaker 1>That's been revealed.

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<v Speaker 2>Indeed. So and so why are they colliding if the

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<v Speaker 2>universe is expanding? Because both those statements are true. The

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<v Speaker 2>universe is expanding, and the two galaxies are colliding. And

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<v Speaker 2>that's because at the on the scale of the distance

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<v Speaker 2>between Us and Andromeda, which is two point five million

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<v Speaker 2>light years, the expansion of the universe is negligible more

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<v Speaker 2>or less the universe. The universe is expanding, but over

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<v Speaker 2>a small distance like that, what becomes the dominant force

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<v Speaker 2>is gravity, and the gravity, the gravitational pull between the

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<v Speaker 2>Milky Way and Andromeda, easily enough to overcome the fact

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<v Speaker 2>that they're being pulled apart much more gently by the

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<v Speaker 2>expansion of the universe. So, and that's we give a term.

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<v Speaker 2>We've got a name for the individual motions of galaxies

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<v Speaker 2>kind of superimposed on the expansion of the universe. We

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<v Speaker 2>call it their peculiar emotions. And it's so the peculiar

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<v Speaker 2>motion of Milky Way relative to Andromeda. Is they colliding

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<v Speaker 2>together and they will collide, whereas the expansion of the

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<v Speaker 2>universe is trying to pull them apart, but at a

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<v Speaker 2>much much slower rate, if I can put it that way.

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<v Speaker 2>It's only when you look on the big scales that

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<v Speaker 2>you see the real effects of the expansion of the universe,

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<v Speaker 2>things that are billions of light years away from us

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<v Speaker 2>rather than just a couple of million, And basically Raoul's right.

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<v Speaker 2>Until nineteen ninety eight, we used to think that eventually

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<v Speaker 2>the gravitational pull of everything in the universe would slow

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<v Speaker 2>down the expansion and the universe would indeed collapse on

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<v Speaker 2>itself in what we always call Andrew.

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<v Speaker 1>The ganeb GiB, the gonab.

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<v Speaker 2>GiB exactly, big bang, that's right, Brian branch mates praise

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<v Speaker 2>the gonnab GiB. We used to think often called the

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<v Speaker 2>big crunch as well. That was the thinking. But it

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<v Speaker 2>was when Brian Schmitz Ant his colleagues and other colleagues

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<v Speaker 2>in the United States, when they discovered the accelerated expansion

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<v Speaker 2>of the universe that possible the possibility of the gadab

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<v Speaker 2>GiB was thrown out of the window. Because the universe is,

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<v Speaker 2>as far as we know, going to expand forever and

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<v Speaker 2>there isn't enough stuff in it for its gravitational pull

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<v Speaker 2>to halt the expansion. And part of that is because

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<v Speaker 2>we think that space itself has an energy we call

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<v Speaker 2>it dark energy, and the more space you have, the

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<v Speaker 2>more energy you've got, and that energy is trying to

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<v Speaker 2>push things apart, to push the universe into ever ever

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<v Speaker 2>faster expansion. So, yes, it looks as though that big

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<v Speaker 2>crunch scenario has gone out the window. But it was

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<v Speaker 2>very popular in the nineteen seventies and eighties.

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<v Speaker 1>So what's the opposite to a big crunch? It's a

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<v Speaker 1>Hagner gibnurk.

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<v Speaker 2>Yes, that sounds right.

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<v Speaker 1>Yeah, someone's going to ask you again because we've had

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<v Speaker 1>the question before.

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<v Speaker 3>But you know, if the.

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<v Speaker 1>Universe keeps expanding and it's filling with dark energy, where

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<v Speaker 1>where's the energy coming from? You know, wouldn't have that

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<v Speaker 1>has that fueling itself? We don't know.

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<v Speaker 2>We all comes out of space.

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<v Speaker 1>Yeah, it comes from somewhere. Yeah, people say I was

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<v Speaker 1>coming from a dark matter, but when they're not related,

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<v Speaker 1>they're just badly named.

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<v Speaker 2>Yes, that's correct. Maybe it's coming from outside.

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<v Speaker 1>You know, if there's multiverses or that would be something,

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<v Speaker 1>wouldn't it. We should just go and have a look. Simple.

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<v Speaker 2>That's a good idea, same voyage that.

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<v Speaker 1>Well, it's on its way. We just have to sit

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<v Speaker 1>here and twiddle our thumbs and just wait a little while,

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<v Speaker 1>and then we'll know if the batteries don't run out. Uh.

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<v Speaker 1>Did we finish with Raoul? I think so yeah, Yes,

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<v Speaker 1>all the best Raoul, and I hope Chelsea doesn't win

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<v Speaker 1>as much as Liverpool. Let's go to our final question,

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<v Speaker 1>and this one comes from this is David. Wow, what

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<v Speaker 1>a coincidence. Hi love your podcast. I live in the

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<v Speaker 1>lovely dark city of Tucson. That will be the Arizona variety.

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<v Speaker 1>I imagine my question my question. I assume astronomers use

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<v Speaker 1>the sun as a center of reference, but what about

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<v Speaker 1>the future when we want to travel somewhere else? Everything

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<v Speaker 1>is moving and it's a no body system. It's hard

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<v Speaker 1>to know exactly where anything is going to be if

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<v Speaker 1>you wait long enough, How will you tell our colony

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<v Speaker 1>on proximate sentry where to go or where to look

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<v Speaker 1>when it takes four point two years for them to

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<v Speaker 1>get the message? That's from David. I like this question.

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<v Speaker 1>It's a long term future problem when we're living in

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<v Speaker 1>other parts of the of the galaxy outside our own

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<v Speaker 1>solar system. We've we've made the giant leap and ended

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<v Speaker 1>up on one of those perfectly normal planets around the

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<v Speaker 1>Alpha Centauri system, and we want to come back. How

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<v Speaker 1>do we find how do we find our way back?

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<v Speaker 1>I mean, we can find our way there, so I

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<v Speaker 1>assume we can find our way back. M Mathematics would

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<v Speaker 1>be my answer to this one.

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<v Speaker 2>Well, it is, it's it's a it's a good question actually,

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<v Speaker 2>and it has a real significance to it because we

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<v Speaker 2>we need we already need reference points like that for

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<v Speaker 2>things like GPS, you know, satellite navigation systems, space space navigator.

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<v Speaker 2>Even in the small distances within our solar system, you

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<v Speaker 2>need fixed reference points. And what we use are the

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<v Speaker 2>things on the sky that move least and that bright,

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<v Speaker 2>and they are quasars. So quasars are very bright sources,

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<v Speaker 2>but there are very great distances, so distant that nothing

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<v Speaker 2>we could ever do in terms of our movement would

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<v Speaker 2>change their positions on the sky. And so quasars have

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<v Speaker 2>formed the fundamental reference system that's used in astronomy actually

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<v Speaker 2>as well as for navigation. We use them to set

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<v Speaker 2>up basically reference systems for measuring galaxy position, star positions,

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<v Speaker 2>things of that sort. You use something that's not going

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<v Speaker 2>to move, and the quasars don't move because they're so

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<v Speaker 2>far away. So it's already there, David. And hopefully when

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<v Speaker 2>you leave Tucson and head out towards Alpha Centauri, you

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<v Speaker 2>won't need to have any worries that you'll lose your

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<v Speaker 2>way home. You'll find your way.

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<v Speaker 1>But yes, and don't ignore the sign that says next

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<v Speaker 1>fuel stop two bill in kilometers. You really don't want

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<v Speaker 1>to skip that one because it's a long way to

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<v Speaker 1>the toilet, let's face it. Yeah, yeah, all right, I

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<v Speaker 1>didn't realize it'd be that easy, Fay.

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<v Speaker 3>It's good to know. Yep.

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<v Speaker 1>We just got to we've just got to perfect the

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<v Speaker 1>engines that enable us to travel far distance is in

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<v Speaker 1>a bit of a hurry. That's that's probably the bigger

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<v Speaker 1>challenge than the navigation. Thanks David. Great question, and if

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<v Speaker 1>you have a question please send it into us fire

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<v Speaker 1>our website space nuts dot io. You thought I was

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<v Speaker 1>going to say space nuts podcast dot com, didn't you. Yes,

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<v Speaker 1>well that counts to you can use both. They all

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<v Speaker 1>end up in the same place, and you can send

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<v Speaker 1>us a text or audio question just by clicking on

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<v Speaker 1>the AMA tab. And if you've got a device with

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00:23:57.559 --> 00:23:59.480
<v Speaker 1>a microphone, you're all set down. Forget to tell us

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<v Speaker 1>who you are, where you're from, and don't forget to

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<v Speaker 1>leave your reviews on whatever platform you use to listen

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<v Speaker 1>to us and social media, follow us, like us, subscribe

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<v Speaker 1>wherever you are. We'd love you to make our little

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<v Speaker 1>family a little bit bigger. And don't forget about the

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<v Speaker 1>Space Nuts podcast group on Facebook. It's always growing. It's

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<v Speaker 1>growing like a like a blob of gas in a

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00:24:22.839 --> 00:24:27.880
<v Speaker 1>nebula or whatever it is, and will Yeah. It's where

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<v Speaker 1>you can sort of chat with like minded people who

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<v Speaker 1>follow Space Nuts, talk to each other, ask each other questions,

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<v Speaker 1>share your astronomical photographs and stories. It's growing at a

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<v Speaker 1>rate of knots. It is bread. And thank you for

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<v Speaker 1>your company today, friend, Thanks for tolerating my stupidity and

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<v Speaker 1>answering all those questions.

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<v Speaker 2>That's all right, I can live with Andrew, No, we'll

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<v Speaker 2>continue to do so, keep up the good work. It's

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<v Speaker 2>always great to talk. Thanks a lot, We'll see you soon.

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<v Speaker 1>Professor Fred Watson, Astronomer at Large, and the Not Professor Hugh.

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<v Speaker 1>Thank you to him for helping out Not today and

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<v Speaker 1>we'll see you very soon. Andrew Dunkley signing off, We'll

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<v Speaker 1>catch you on the very next episode of Space Nuts.

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<v Speaker 1>Bye Byepacenuts. You'll be listening to the Space Nuts podcast

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<v Speaker 1>available at Apple Podcasts, Spotify, iHeart Radio, or your favorite

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<v Speaker 1>podcast player. You can also stream on demand at bites

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00:25:30.319 --> 00:25:34.240
<v Speaker 1>dot com. This has been another quality podcast production from

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<v Speaker 1>nights dot com.