Speaker 1: Hi, there, Andrew Duncley again with another episode of Space Nuts,
Speaker 1: and it's good to have your company. This is a
Speaker 1: Q and A edition. This is where we answer your
Speaker 1: questions if we can. If we can't, we just pretend to.
Speaker 1: We've got questions about light and redshift. Today we're also
Speaker 1: going to talk gas giants, expansion of the galaxy versus
Speaker 1: or expansion of the universe versus galaxy collisions, and a
Speaker 1: future of navigation reference points. How are we going to
Speaker 1: do that? When we start going further and further out,
Speaker 1: those questions will be answered or they'll be faked. We're
Speaker 1: not sure yet. Deep fake radio coming up soon on
Speaker 1: this edition of Space Nuts fifteen seconds. Guidance is in
Speaker 1: channel ten nine ignition sequence Space Nuts or three two.
Speaker 2: One Space Nuts.
Speaker 1: As can I report it?
Speaker 2: Neils good and.
Speaker 1: He's here again, like a fly on a piece of meat.
Speaker 1: Hello Fred, Thanks so do Thanks professor Fred. What's an
Speaker 1: astronomer at large? Nice to see you.
Speaker 2: Yeah, that's right, it's nice to see you too. I
Speaker 2: think I.
Speaker 1: Have enough digs at Hugh. I thought maybe I.
Speaker 2: Should just should That's fine.
Speaker 1: Land a left hook for a change. It always comes
Speaker 1: back and hits me. Though eventually, so, yeah, I can't
Speaker 1: take it.
Speaker 3: I'm tough.
Speaker 1: Let's let's go straight to our questions. Our first question today,
Speaker 1: Fred comes from Mario in Melbourne. He likes to go
Speaker 1: go karting. Hi, Fred and Andrew, hoping you can help
Speaker 1: explain why if light itself doesn't experience time, how can
Speaker 1: it redshift? Doesn't red shifting imply it changes somehow, which
Speaker 1: implies it must have been subject to time. Or is
Speaker 1: this some sort of relativity witchcraft where we as observers
Speaker 1: experience time and the red shift, but the photon itself
Speaker 1: somehow in all states it can be simultaneously or something
Speaker 1: like that. Yeah, simultaneously or something like that. Appreciate you
Speaker 1: unscrambling my brain on this one. Still listening from the
Speaker 1: far start keep up the great show, Mario from Melbourne.
Speaker 1: I think we've kind of had variations of this question
Speaker 1: come up in the past. People sort of have trouble
Speaker 1: differentiating between light and time and what's going on out there.
Speaker 1: Can you shed some light on this one for it?
Speaker 2: I'm sorry, I'm completely in the dark about this one.
Speaker 2: It's a good point though, and so it's made me.
Speaker 2: You know, it's got the old cogs working to try
Speaker 2: and work out what's happening. Because that's right. Because light
Speaker 2: travels at the speed of light to the fastest speed
Speaker 2: anything could travel through the universe, it does not experience time.
Speaker 2: A photon of light does not experience time, and yet
Speaker 2: they change. And you're right, Mario is correct that we
Speaker 2: do see photons changing because the photons that we are
Speaker 2: now receiving from distant galaxy, for example, are highly red shifted.
Speaker 2: They've become ready photons. Now, what that corresponds to is
Speaker 2: a loss of energy, which results from the expansion of
Speaker 2: the universe. And so I think I'm right in saying
Speaker 2: that the photon doesn't notice that. It doesn't know that
Speaker 2: it's lost energy because it doesn't experience time. So I
Speaker 2: think you know, in a sense the loss of energy,
Speaker 2: which by the way, just filters out into the universe.
Speaker 2: Apparently normally that's where it goes. It's I think that
Speaker 2: is a property of the observer, the fact that we're
Speaker 2: observing this thing. The photon, the best of my understanding,
Speaker 2: doesn't care it arrives at the same time as it
Speaker 2: left because it doesn't experience time. But it might be
Speaker 2: surprised that where the place where it arrived at is
Speaker 2: very different from the place where it left out in
Speaker 2: terms of the energy balance and what's happening there. I'm
Speaker 2: not sure whether I'm making much sense here, Mario, but
Speaker 2: that's my understanding of the situation.
Speaker 1: Okay, it is a bit complicated. It'd be nice to
Speaker 1: be a photon if you're doing a long haul flight,
Speaker 1: because if you didn't experienced time, you wouldn't have to
Speaker 1: worry about it twenty hour flight to Turkey, for example,
Speaker 1: or anything like that. Yes, this is weak, yeah all over. Yeah,
Speaker 1: we hope we unscrambled your brain, Mario, because it is
Speaker 1: a bit of a scrambling issue. But photons don't experience time,
Speaker 1: and they don't know that they're losing energy. It's sort
Speaker 1: of like old people.
Speaker 2: Yep, yep, go to health. I probably you should say that,
Speaker 2: though you know. Now look I can vouch for that.
Speaker 3: I'm starting to.
Speaker 1: Experience that myself. Yes, thanks, Mario. Let's move on to
Speaker 1: our next one. This comes from Nugel.
Speaker 4: Oh friend Andrew, this is Nigel from Brisbane, Australia. I
Speaker 4: have two questions about our gas giants, Jupiter and Satin.
Speaker 4: I want to know beneath all that gas. Is there
Speaker 4: a rocky planet and if so, how big are they
Speaker 4: in relation to the Earth? Okay, thank you, love the show.
Speaker 3: Keep up the good work, thanks Nigel.
Speaker 1: Yeah, look, its.
Speaker 3: Theory, isn't it.
Speaker 1: Fred. We don't know for sure what's down deep in
Speaker 1: those gas giants, but there might be something.
Speaker 2: Well, you've absolutely answered the question, Andrew.
Speaker 1: Okay, we'll move on to the next one from Raoul.
Speaker 2: Nigel's question is you know it's one that many astronomers
Speaker 2: and plunge your scientists ask because we don't know, we
Speaker 2: don't know the answer. The modeling suggests that, because of
Speaker 2: the way we believe planets are formed, that there should
Speaker 2: be a rocky core underneath all that gas, that it
Speaker 2: should be quite massive, maybe with a fair degree of
Speaker 2: a water ice involved with it as well. Although some
Speaker 2: of the papers that I've read suggest that there might
Speaker 2: be something called metallic hydrogen at the center of these
Speaker 2: gas giants. I'm not sure what that means. Probably mean
Speaker 2: hydrogen in a state where it can conduct electricity. So yeah,
Speaker 2: so that's it's a question that's really at the forefront
Speaker 2: of knowledge. So you and me both, Nigel, I wonder
Speaker 2: what's at the center of these gas giants and how
Speaker 2: big the central core might be if there is one,
Speaker 2: which we assume there is.
Speaker 1: Yeah, I mean guess giants to a certain degree. What
Speaker 1: could have been stars had their formation happened in a bigger,
Speaker 1: better way. At what point do they reach in size
Speaker 1: or structure where they wouldn't have a solid core? Like
Speaker 1: would a brown dwarf? How does have a solid core?
Speaker 2: Perhaps, Yeah, that's certainly a brown dwarf would have a core,
Speaker 2: and it probably wouldn't be solid either, similar to more
Speaker 2: similar to what the Sun's core we think is like,
Speaker 2: compared with what a planet's core is like. So brown
Speaker 2: dwarf has nuclear reactions taking place, but they're low level.
Speaker 2: Once they're something called deuterium burning, and that doesn't generate
Speaker 2: anything like the same amount of heat as the hydrogen
Speaker 2: process that is going on at the center of our sun.
Speaker 2: So at the center of the Sun, you've got this
Speaker 2: ball of energy, very very hot, radiating gamma ray photons
Speaker 2: out which eventually find their way as a visible light
Speaker 2: out to the surface. The brown dwarf, you've got low
Speaker 2: level radiation which finds its way to the surface. With
Speaker 2: a gas giant, though we don't know that's the thing.
Speaker 2: We really don't know what the core would below.
Speaker 1: That.
Speaker 2: The thinking is that that they are cold enough to
Speaker 2: have a solid core. You know that you're not talking
Speaker 2: about a ball of energy. But we do know again
Speaker 2: that there are nuclear actions taking place. For example, in
Speaker 2: the core of Jupiter Jupiter radio is at one point
Speaker 2: eight times more heat than it receives from the salt
Speaker 2: that's coming from maybe uranium fission or something like that
Speaker 2: happening down there in its interior.
Speaker 1: Wow, do they have a theory if Jupiter has a core?
Speaker 1: Do they have a theory on how big it is
Speaker 1: compared worth?
Speaker 2: Probably? But look, I'm going to take as take a
Speaker 2: punt and say yes, people probably do think it is
Speaker 2: about the size of Earth. I'm sure that kind of
Speaker 2: suggestion before. I just remember Jupiter's about eleven times the
Speaker 2: diamature of Earth.
Speaker 1: Yeah. Wow, all right, jury is still out, Nigel, but
Speaker 1: it maybe could be done. Oh type of scenario. Thanks
Speaker 1: for the question. Sorry, nothing to do with us, nothing
Speaker 1: to see here. This is space Sandred Duntley with Fred Watson,
Speaker 1: Professor Astronomer at Large. Great guy, Now let's take a
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Speaker 2: Three Space Nuts.
Speaker 1: Okay, our next question, Fred comes from Raoul.
Speaker 3: Hi, guys, Raoul from California here and a big Chelsea fan.
Speaker 3: I know you were talking about American football, but I
Speaker 3: do like europeanotball. Had a question for you. If the
Speaker 3: universe is ever expanding from the Big Bang, then all
Speaker 3: the galaxies will be moving apart from each other. But
Speaker 3: I recall seeing on a show that galaxies could one
Speaker 3: day collide. Does that mean that the universe is stopping
Speaker 3: its expansion or slowing its expansion, allowing the gravity of
Speaker 3: galaxies to then collide. And if that is the case,
Speaker 3: will the universe one day stop expanding and start to
Speaker 3: contract upon whatever the hugest big black hole in the
Speaker 3: middle of the universe really is. Thanks a lot, you
Speaker 3: guys do great love listening to it. Beat the show.
Speaker 1: I love what you did, right, Thank you, David Chelsea.
Speaker 1: Oh sorry, yeah, David, next roll roll thanks for that. Yes,
Speaker 1: Chelsea fan, but yeah, we'll forgive you for that. I'm
Speaker 1: a Liverpool fan myself. Do you follow English Premier League?
Speaker 2: Most League slightly? Yeah? Only you know some of the
Speaker 2: bigger teams. I've was interested in what they're doing. I've
Speaker 2: got a son in law and a grand couple of
Speaker 2: grandsons who are absolutely mad Manchester United freaks, and you know,
Speaker 2: various various other football teams. I never really got heavily
Speaker 2: into football. I can never remember which I was supposed
Speaker 2: to be kicking the balls and it wasn't nice team really,
Speaker 2: But yeah, that takes an interest.
Speaker 1: Yeah, I played soccer for ten years, never won a thing.
Speaker 1: I didn't even win the Raffle anyway. Raoul's asking about
Speaker 1: the universe and his expansion versus galaxy collisions basically, and
Speaker 1: is the expansion slowing or stopping? And is that why
Speaker 1: galaxies are going to crash into each other? Is it
Speaker 1: all going to sort of fall back into a giant
Speaker 1: black hole in the middle. We've had variations of questions
Speaker 1: like this over the years. It's one that always spawns
Speaker 1: a lot of interest.
Speaker 2: It does, doesn't it. And there are actually two things
Speaker 2: going on here. I think in rolls question because it's
Speaker 2: quite right that some galaxies do collide with each other,
Speaker 2: but in fact we are in poor position for a
Speaker 2: collision with Andromeda that might already be happening.
Speaker 1: In fact, yeah, in fact, yeah, we talked about it
Speaker 1: the other day. They're actually sort of you know, tickling
Speaker 1: their fingertips at the moment because of their giant gas balls.
Speaker 1: That's been revealed.
Speaker 2: Indeed. So and so why are they colliding if the
Speaker 2: universe is expanding? Because both those statements are true. The
Speaker 2: universe is expanding, and the two galaxies are colliding. And
Speaker 2: that's because at the on the scale of the distance
Speaker 2: between Us and Andromeda, which is two point five million
Speaker 2: light years, the expansion of the universe is negligible more
Speaker 2: or less the universe. The universe is expanding, but over
Speaker 2: a small distance like that, what becomes the dominant force
Speaker 2: is gravity, and the gravity, the gravitational pull between the
Speaker 2: Milky Way and Andromeda, easily enough to overcome the fact
Speaker 2: that they're being pulled apart much more gently by the
Speaker 2: expansion of the universe. So, and that's we give a term.
Speaker 2: We've got a name for the individual motions of galaxies
Speaker 2: kind of superimposed on the expansion of the universe. We
Speaker 2: call it their peculiar emotions. And it's so the peculiar
Speaker 2: motion of Milky Way relative to Andromeda. Is they colliding
Speaker 2: together and they will collide, whereas the expansion of the
Speaker 2: universe is trying to pull them apart, but at a
Speaker 2: much much slower rate, if I can put it that way.
Speaker 2: It's only when you look on the big scales that
Speaker 2: you see the real effects of the expansion of the universe,
Speaker 2: things that are billions of light years away from us
Speaker 2: rather than just a couple of million, And basically Raoul's right.
Speaker 2: Until nineteen ninety eight, we used to think that eventually
Speaker 2: the gravitational pull of everything in the universe would slow
Speaker 2: down the expansion and the universe would indeed collapse on
Speaker 2: itself in what we always call Andrew.
Speaker 1: The ganeb GiB, the gonab.
Speaker 2: GiB exactly, big bang, that's right, Brian branch mates praise
Speaker 2: the gonnab GiB. We used to think often called the
Speaker 2: big crunch as well. That was the thinking. But it
Speaker 2: was when Brian Schmitz Ant his colleagues and other colleagues
Speaker 2: in the United States, when they discovered the accelerated expansion
Speaker 2: of the universe that possible the possibility of the gadab
Speaker 2: GiB was thrown out of the window. Because the universe is,
Speaker 2: as far as we know, going to expand forever and
Speaker 2: there isn't enough stuff in it for its gravitational pull
Speaker 2: to halt the expansion. And part of that is because
Speaker 2: we think that space itself has an energy we call
Speaker 2: it dark energy, and the more space you have, the
Speaker 2: more energy you've got, and that energy is trying to
Speaker 2: push things apart, to push the universe into ever ever
Speaker 2: faster expansion. So, yes, it looks as though that big
Speaker 2: crunch scenario has gone out the window. But it was
Speaker 2: very popular in the nineteen seventies and eighties.
Speaker 1: So what's the opposite to a big crunch? It's a
Speaker 1: Hagner gibnurk.
Speaker 2: Yes, that sounds right.
Speaker 1: Yeah, someone's going to ask you again because we've had
Speaker 1: the question before.
Speaker 3: But you know, if the.
Speaker 1: Universe keeps expanding and it's filling with dark energy, where
Speaker 1: where's the energy coming from? You know, wouldn't have that
Speaker 1: has that fueling itself? We don't know.
Speaker 2: We all comes out of space.
Speaker 1: Yeah, it comes from somewhere. Yeah, people say I was
Speaker 1: coming from a dark matter, but when they're not related,
Speaker 1: they're just badly named.
Speaker 2: Yes, that's correct. Maybe it's coming from outside.
Speaker 1: You know, if there's multiverses or that would be something,
Speaker 1: wouldn't it. We should just go and have a look. Simple.
Speaker 2: That's a good idea, same voyage that.
Speaker 1: Well, it's on its way. We just have to sit
Speaker 1: here and twiddle our thumbs and just wait a little while,
Speaker 1: and then we'll know if the batteries don't run out. Uh.
Speaker 1: Did we finish with Raoul? I think so yeah, Yes,
Speaker 1: all the best Raoul, and I hope Chelsea doesn't win
Speaker 1: as much as Liverpool. Let's go to our final question,
Speaker 1: and this one comes from this is David. Wow, what
Speaker 1: a coincidence. Hi love your podcast. I live in the
Speaker 1: lovely dark city of Tucson. That will be the Arizona variety.
Speaker 1: I imagine my question my question. I assume astronomers use
Speaker 1: the sun as a center of reference, but what about
Speaker 1: the future when we want to travel somewhere else? Everything
Speaker 1: is moving and it's a no body system. It's hard
Speaker 1: to know exactly where anything is going to be if
Speaker 1: you wait long enough, How will you tell our colony
Speaker 1: on proximate sentry where to go or where to look
Speaker 1: when it takes four point two years for them to
Speaker 1: get the message? That's from David. I like this question.
Speaker 1: It's a long term future problem when we're living in
Speaker 1: other parts of the of the galaxy outside our own
Speaker 1: solar system. We've we've made the giant leap and ended
Speaker 1: up on one of those perfectly normal planets around the
Speaker 1: Alpha Centauri system, and we want to come back. How
Speaker 1: do we find how do we find our way back?
Speaker 1: I mean, we can find our way there, so I
Speaker 1: assume we can find our way back. M Mathematics would
Speaker 1: be my answer to this one.
Speaker 2: Well, it is, it's it's a it's a good question actually,
Speaker 2: and it has a real significance to it because we
Speaker 2: we need we already need reference points like that for
Speaker 2: things like GPS, you know, satellite navigation systems, space space navigator.
Speaker 2: Even in the small distances within our solar system, you
Speaker 2: need fixed reference points. And what we use are the
Speaker 2: things on the sky that move least and that bright,
Speaker 2: and they are quasars. So quasars are very bright sources,
Speaker 2: but there are very great distances, so distant that nothing
Speaker 2: we could ever do in terms of our movement would
Speaker 2: change their positions on the sky. And so quasars have
Speaker 2: formed the fundamental reference system that's used in astronomy actually
Speaker 2: as well as for navigation. We use them to set
Speaker 2: up basically reference systems for measuring galaxy position, star positions,
Speaker 2: things of that sort. You use something that's not going
Speaker 2: to move, and the quasars don't move because they're so
Speaker 2: far away. So it's already there, David. And hopefully when
Speaker 2: you leave Tucson and head out towards Alpha Centauri, you
Speaker 2: won't need to have any worries that you'll lose your
Speaker 2: way home. You'll find your way.
Speaker 1: But yes, and don't ignore the sign that says next
Speaker 1: fuel stop two bill in kilometers. You really don't want
Speaker 1: to skip that one because it's a long way to
Speaker 1: the toilet, let's face it. Yeah, yeah, all right, I
Speaker 1: didn't realize it'd be that easy, Fay.
Speaker 3: It's good to know. Yep.
Speaker 1: We just got to we've just got to perfect the
Speaker 1: engines that enable us to travel far distance is in
Speaker 1: a bit of a hurry. That's that's probably the bigger
Speaker 1: challenge than the navigation. Thanks David. Great question, and if
Speaker 1: you have a question please send it into us fire
Speaker 1: our website space nuts dot io. You thought I was
Speaker 1: going to say space nuts podcast dot com, didn't you. Yes,
Speaker 1: well that counts to you can use both. They all
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Speaker 1: growing like a like a blob of gas in a
Speaker 1: nebula or whatever it is, and will Yeah. It's where
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Speaker 1: follow Space Nuts, talk to each other, ask each other questions,
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Speaker 1: your company today, friend, Thanks for tolerating my stupidity and
Speaker 1: answering all those questions.
Speaker 2: That's all right, I can live with Andrew, No, we'll
Speaker 2: continue to do so, keep up the good work. It's
Speaker 2: always great to talk. Thanks a lot, We'll see you soon.
Speaker 1: Professor Fred Watson, Astronomer at Large, and the Not Professor Hugh.
Speaker 1: Thank you to him for helping out Not today and
Speaker 1: we'll see you very soon. Andrew Dunkley signing off, We'll
Speaker 1: catch you on the very next episode of Space Nuts.
Speaker 1: Bye Byepacenuts. You'll be listening to the Space Nuts podcast
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