#396: Cosmic Riddles & Martian Quakes: Unpacking the Universe's Expansion & Insight's Seismic Secrets

[00:00:00] Hello again, thanks for joining us. This is Space Nuts. Coming up, we're talking

[00:00:05] questions about the expansion of space again, the inside mission and gravitational waves.

[00:00:11] That's all coming up on this edition of Space Nuts.

[00:00:15] 15 seconds guidance is internal. 10, 9, ignition sequence start.

[00:00:21] Space Nuts.

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[00:00:27] Space nuts.

[00:00:28] As an entrepreneur, it feels good.

[00:00:31] And joining me, as always, Professor Fred,

[00:00:34] what's on astronomer at Large High Fred?

[00:00:37] Hello, Andrew.

[00:00:38] Very good to see you again.

[00:00:40] Now, Fred, it is time to talk questions and answers

[00:00:43] from our audience.

[00:00:44] We've got a few text questions to go through today and the first one comes from Nate.

[00:00:51] Now this is a question we've had probably many times but it's worth revisiting because

[00:00:57] you never know what we're going to learn as we heard early on.

[00:01:00] Things can change in the astronomical world at the flick of a switch on the James

[00:01:07] Webb Space Telescope. So Nate asked 13.8 billion years ago, something happened. We know that

[00:01:16] whether it was a big bang, the big bounce or a big Mac, we know there was an event in

[00:01:23] a seemingly centralised location. My question is, if space

[00:01:27] is expanding, what is it expanding into or on? Even the singularity, if that's even correct,

[00:01:35] should have been residing in something, right? Thanks for making my evenings great. Every podcast

[00:01:41] is listened to the moment it is dropped and I cherish each and every one. You two are fabulous

[00:01:47] and have been a part of our lives since day one. Have a great

[00:01:50] holiday. We're back. And I can't wait to hear your answer. Yeah,

[00:01:56] it's an old chestnut. This one, what are we expanding into? Or

[00:02:00] although he goes, now, what could we be expanding on? That's an

[00:02:04] interesting angle.

[00:02:07] Well yes, yes it is, it's a nice additional way of putting it. So I think the problem is

[00:02:17] that we apply our common or garden everyday logic to problems of cosmology that don't necessarily work on those

[00:02:29] logical principles like parallel lines never meeting and things like that, which is actually

[00:02:38] it is logic but it's geometrical logic of a more unusual kind. So the observation that we can make,

[00:02:47] and I guess there's two or three of them, are that refers, relate to this. We can observe that

[00:02:54] the universe is expanding because we've got this signature velocity distribution of galaxies

[00:03:01] that the further away a galaxy you see, the faster it is moving away from you. And that's exactly what you will get from

[00:03:09] space that is expanding. We also know that as far as we can see, there isn't an

[00:03:18] edge to it. We can see a horizon and that the busiest one to envisage is the cosmic microwave background

[00:03:27] radiation where you're looking so far back in time when you look out into space that

[00:03:33] you're seeing the flash of the big bang which is now stretched from light waves to radio

[00:03:39] waves microwaves by the expansion of the universe. So the likelihood is that the universe just goes

[00:03:48] on beyond that. And if we were, there's nothing to suggest that, that's not the case. If we were

[00:03:53] somewhere else in the universe and looked out from our vantage point, which is different from

[00:03:59] where we are at the moment on our galaxy, for on somebody else's galaxy somewhere else,

[00:04:06] we would see the same thing. We thing with cosmic microwave background radiation and lots of galaxies all expanding

[00:04:10] away from us. Yeah, so the question about what's it expanding into? We don't even know whether that's a meaningful question because it's actually compressing

[00:04:27] the thing into our own perception of space and time.

[00:04:34] Whereas there are possibilities, certainly in terms of the geometry of the universe,

[00:04:43] there are possibilities that might say, well, it doesn't have an edge.

[00:04:46] For example, if you, you know, it's like the idea of, in fact, this is quite good analogy, actually.

[00:04:53] If you think of a, of your, excuse me, perception of the universe, reduced to two dimensions.

[00:05:02] Now, we normally think of two dimensions as being on a piece of paper,

[00:05:07] a flat surface. But it could equally well be on a curved surface like a balloon. So if you have your

[00:05:16] perception of space sitting on the surface of a balloon, it expands as you blow up the balloon. And yes, in our view that we've got,

[00:05:32] it is expanding into an additional dimension, which is the third dimension of space. So

[00:05:37] maybe, maybe it will turn out that we will discover that there are hyperdimensional spaces within what we've been thinking of as

[00:05:48] the universe, but maybe the universe is just something part of something much smaller. So if you thought,

[00:05:53] sorry, I'm rambling a bit here, Andrew, but we've got a universe that's got three dimensions of space

[00:05:58] and one of time. But if it was embedded in a fifth dimensional something, in the same way that the balloon

[00:06:07] is embedded in proper space, then it may be is expanding into something else.

[00:06:14] That's a complex way of describing something quite simply, which is, we don't really know,

[00:06:20] but we think there are possibilities.

[00:06:24] There are geometrical possibilities that would allow that to happen.

[00:06:28] For the universe not to have an edge and be expanding,

[00:06:31] but to be expanding perhaps in relation to something like an additional dimension.

[00:06:38] We haven't seen any evidence of extra dimensions yet in any sense.

[00:06:42] But there are some various due to people that do believe that that may be a possibility.

[00:06:48] Yeah.

[00:06:49] And that there are multiple universes as well.

[00:06:51] Yes, of course.

[00:06:52] And what's the other one I heard that the universe is folding back on itself?

[00:06:58] That's another one I heard.

[00:07:01] But like a pile of washing.

[00:07:03] Yes.

[00:07:04] Yes, the universe is just a massive laundry.

[00:07:08] Well, these are rather dirty places, isn't it? I mean, it's just full of dust.

[00:07:15] Absolutely, dust and gas and humans. Yeah, just a message. Yeah, that's right, completeness.

[00:07:22] Yeah, that's right, completeness. All right, thank you, Nate.

[00:07:25] The answer is, yes, it's expanding.

[00:07:28] It's expanding at an accelerating rate and what it's expanding into we do not know.

[00:07:35] Lee Stevenson has sent us a question.

[00:07:37] Hi, guys.

[00:07:38] I'm an avid listener since discovering your show around six months ago.

[00:07:42] You are funny and educational at the same time. Which one of us?

[00:07:46] Okay, it's a great show. My question is, how can we learn so much about Mars interior from the

[00:07:54] inside mission? I can't figure out how we got the knowledge we have from a single point of

[00:08:00] reference down to the estimated location of meteor impacts. This has been puzzling me for quite a while.

[00:08:07] And I hope you can explain and educate me best wishes Lee and

[00:08:10] Englishman in speed in yeah.

[00:08:13] Well, it's not that big a hop from England this weekend.

[00:08:16] So stop showing off.

[00:08:21] Actually, I meant to I mean to I saw this question and meant to check it out because I've been ill for the

[00:08:28] past few days.

[00:08:29] I haven't really had time.

[00:08:30] But there is some very, very clever work that's been done by the Insight team.

[00:08:40] I think it involves, of course, like all seismology, you know, most seismology, you've

[00:08:48] got a volcano or something that erupts or there's something hits the ground and you pick up

[00:08:57] by a network of seismographs or seismometers all over the planet. This is on earth, of course. You pick up the echoes of that particular seismic event,

[00:09:10] whether it's a reflection of the core-mental boundary or whether it's a refraction past the core.

[00:09:18] These are all things that you can pick up, but it's fairly easy to understand what's going on. That you can explore the inside of the earth by having multiple sample points.

[00:09:28] By that, I mean, you know, lots of seismographs all over.

[00:09:32] Well, on Mars, you don't you don't have that.

[00:09:35] You've got one little seismic, one little

[00:09:38] lander insight, which I think I'm right.

[00:09:41] And certainly is now defunct.

[00:09:43] It's yes, the switch did often there last year.

[00:09:48] It's got one sensor.

[00:09:52] So how do you know when you are listening

[00:09:56] to the seismic signal of a meteorite hitting Mars

[00:10:02] 13,000 kilometers away or something like that?

[00:10:04] But it's a very, very good question.

[00:10:06] Now, because I'm meant to look this up,

[00:10:08] I'm not going to give a definitive answer here,

[00:10:10] but we might take that down as a bit of homework, Andrew.

[00:10:14] But I'm guessing it may be to do with the fact

[00:10:19] that seismic waves don't just come in one variety.

[00:10:22] There are...

[00:10:24] If I remember all these P waves and S waves, P

[00:10:28] waves I think are pressure waves and S waves are shear waves, which is two

[00:10:33] different ways that the medium that this is being transmitted through

[00:10:39] vibrates and it actually it's akin to a shear wave will be a bit like a light wave, which is a

[00:10:48] transverse wave. That's what we call it an electromagnetic radiation. Whereas a P wave will

[00:10:53] be like a sound wave because sound is transmitted by pressure by vibration variations in a medium.

[00:10:59] It's got to have a medium to transmit it. And I suspect that you can do things with those like the kind

[00:11:06] of things that we do with fast radio bursts in astronomy, where you know that the slower

[00:11:14] the longer wavelength signals are going to come slower than the higher, sorry, shorter

[00:11:21] wavelength signals. In other words, the higher frequency signals are going to arrive first.

[00:11:25] And that's what causes that dispersion

[00:11:28] that lets you get the distance to something

[00:11:30] without actually knowing its redshift.

[00:11:32] You get the dispersion because you know,

[00:11:34] as it transmits through what we think of as empty space,

[00:11:39] there is actually a lot of electrons being very excited.

[00:11:44] So you can pick up information by that. So I'm

[00:11:47] guessing it's something like that. But I will look that up because that's such a good question.

[00:11:51] And as I said, I saw it and I thought, yes, I must do some research into that.

[00:11:56] It's very clever science though that they can detect an impact so far away and actually isolate

[00:12:03] its location.

[00:12:05] That's right.

[00:12:06] That's the thing that actually points to the question.

[00:12:08] And Insight did go there with the intent of studying the interior of Mars.

[00:12:15] So it had equipment that was designed to pick up these kinds of activities.

[00:12:20] So that would go halfway to answering Lee's question.

[00:12:24] But we'll put it in the homework folder.

[00:12:26] And for the record, Insights Mission ended in December 2022,

[00:12:29] about 14 months ago.

[00:12:32] It was a year before.

[00:12:33] Yeah, give or take.

[00:12:34] Yeah, thanks.

[00:12:35] Thank you, Lee.

[00:12:36] And to our final question for this episode from Wayne,

[00:12:40] Greetings, gentlemen.

[00:12:41] Long time, Patreon supporter.

[00:12:43] Thank you, Wayne.

[00:12:44] We appreciate it. First time question, though, what gentlemen, long time, Patreon supporter. Thank you, Wayne. We appreciate it.

[00:12:46] First time question, though, what kind of gravitational

[00:12:48] wave, if any, is generated by a supernova?

[00:12:52] Would these be detectable by LIGO?

[00:12:54] Love all the horrible dad jokes.

[00:12:56] Keep up the great work.

[00:12:59] Glad someone likes them.

[00:13:00] That's one.

[00:13:03] I mean, we do.

[00:13:04] So they're actually hard to find some of them. Some of them are so,

[00:13:09] I mean, I've found thousands, but 99.9% of them are not air worthy.

[00:13:17] We must have a different website. I don't mean they're rude. They're just so terrible.

[00:13:27] rude. They're just so terrible. Oh, yeah. So Paul in. Yeah. So, yeah,

[00:13:34] a supernova. Does it make a gravitational wave? And I suppose the question, if I can expand it on a bit is our gravitational waves different according to what causes

[00:13:39] them? Well, the answer to that is certainly yes. And the things that we can measure with LIGO in terms of gravitational waves is the amplitude

[00:13:55] and frequency of the wave and the rate at which it decays or increases in the case of merging neutron stars, what you get is this

[00:14:09] chirp where the signal if you transfer it to audio becomes whoop because the

[00:14:17] spinning around one another and then when they actually merge the, that's the chirb, that's when it goes up like that.

[00:14:25] But I think, and once again, I'm sort of dragging out

[00:14:30] from the bottom of my memories of researching

[00:14:33] into this quite a, quite deeply a few years ago.

[00:14:37] What caused, excuse me, I'll be better

[00:14:42] when I've started the new dose of antibiotic.

[00:14:45] Yeah.

[00:14:46] Which is a great...

[00:14:47] It must really tick you off.

[00:14:50] I tell you, I've never been as ticked off as I was when I discovered what it was.

[00:14:55] Bit you.

[00:14:56] Yeah, that's right.

[00:14:57] Yeah, whatever bit me.

[00:14:59] Yeah.

[00:15:00] I'll refrain from showing you what it...

[00:15:02] Oh, yeah.

[00:15:03] Thank you.

[00:15:04] Because we are on YouTube at the moment.

[00:15:06] Don't want to get banned.

[00:15:08] No, we don't get banned for showing horrible stuff.

[00:15:11] Anyway, so just go back to it.

[00:15:13] So to generate a gravitational wave,

[00:15:15] you've got to have an accelerating mass.

[00:15:18] And that's why neutron stars in orbit around one another,

[00:15:24] do generate strong gravitational waves

[00:15:27] because you've got two objects which are spinning around each other

[00:15:31] revolving around each other.

[00:15:33] And that's basically constitutes an accelerating mass.

[00:15:39] Now, with a supernova, and in a sense,

[00:15:43] we don't know that much about these details, but supernovae,

[00:15:50] sort of generally speaking, are symmetrical. So you have an explosion, but you have stuff going

[00:16:00] out in all directions, which kind of cancels itself out. So you're not really generating a huge...

[00:16:09] It's a good idea.

[00:16:10] ...over in the background, I can hear it.

[00:16:11] Oh, no, no, there is.

[00:16:13] I'm trying to ignore him, actually, because he's...

[00:16:14] Yeah.

[00:16:15] He's just such a pain.

[00:16:18] Marnie sent me a cartoon this morning,

[00:16:22] showing a little dog dressed in armour with a sword in one

[00:16:29] and a shield in the other and he said, how small dogs think of themselves when somebody

[00:16:35] rings the doorbell. That's exactly what he's like. He's still only a puppet, he's only

[00:16:41] ten months old, so you've got to give him some understanding.

[00:16:45] Maybe one day he won't do that anymore.

[00:16:47] Anyway, he is definitely an accelerating mass

[00:16:52] when anybody comes to the door

[00:16:54] and will probably generate his own gravitational word

[00:16:57] or when they do their stuff.

[00:16:59] So, but just to carry this a little bit further,

[00:17:10] I have seen the question of whether a neutron star itself, which is often the end product of a supernova explosion, whether the neutron

[00:17:17] star that will be left behind, because it's rotating, whether that would generate a gravitational wave,

[00:17:27] but it's because it's only rotating, it's not a mass being accelerated linearly,

[00:17:34] it wouldn't, unless it has mountains on it, and you and I have spoken before about these millimeter high mountains

[00:17:41] that neutron stars might have. So if it's got a few millimeter

[00:17:47] high mountains on it, then it will generate generate a gravitational wave. But to the best of my

[00:17:54] knowledge, nothing has yet been seen by LIGO or the other detectors that actually represents that.

[00:17:59] Okay. So great question there, you know, from Wayne.

[00:18:05] You might be interested to know Fred that Wayne is actually watching us on YouTube right

[00:18:09] now and apparently our YouTube listeners and viewers are pretty excited by the fact that

[00:18:15] Wayne's question happened up, happened to be served up right now.

[00:18:19] So that doesn't happen often, but that's really good.

[00:18:22] Thanks for the question and thanks for watching Wayne.

[00:18:25] Sorry, I've got a straight answer, but I'll once again have a look at the details.

[00:18:29] It's a while since I looked at all this stuff.

[00:18:31] Very good.

[00:18:32] All right. Thank you, Wayne.

[00:18:34] And thanks for listening and good to have you a long live.

[00:18:37] And if you do have questions for us, remember you can send them through via our website,

[00:18:43] space nuts podcast.com or space nuts.io and click on the

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[00:19:05] I've got to do it again.

[00:19:06] Don't forget to press the subscribe button below.

[00:19:12] They all do it, though, they're the people on YouTube.

[00:19:15] And don't forget to hit the subscribe button below.

[00:19:17] So there we go. I've just done it.

[00:19:20] And that brings us to the end of another program.

[00:19:22] Thank you so much, Fred.

[00:19:25] Pleasure, Andrew.

[00:19:26] Good to talk again.

[00:19:27] And we'll speak again soon.

[00:19:29] We will indeed.

[00:19:30] Professor Fred Watson, astronomer at large,

[00:19:32] getting over his tick bite.

[00:19:33] And to Hugh in the studio, who just gets ticked off

[00:19:39] all the time.

[00:19:40] And from me, Andrew, don't you?

[00:19:41] Thanks so much for your company looking forward

[00:19:43] to joining you again on the next episode of Space Nuts.

[00:19:47] Bye bye.