The Cosmic Q&A: Redshift, Dark Matter & the Shape of the Universe | Space Nuts: Astronomy...

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Language: en

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Hello again. Thanks for joining us on


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Space Nuts. This is a Q&A edition. My


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name is Andrew Dunley. What's a Q&A


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edition? It's an edition where we get


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Q's and give you A's because you're so


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clever. Uh, something like that. Anyway,


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we're going to answer audience


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questions. That's what I'm getting at.


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We've got questions about Red Shift. We


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got questions about dark photons. What?


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Uh, we've got questions about deep space


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astronomy. And another one about the


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expansion of the universe. So, I think


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we talked about that last episode.


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Anyway, uh we'll see if we can solve all


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of that on this episode of Space Nuts.


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>> 15 seconds. Guidance is internal. 10 9


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Ignition sequence start.


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>> Space Nuts.


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>> 5 4 3 2 1 2 3 4 5 5 4 3 2 1


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>> Space Nuts.


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>> Astronauts report. It feels good.


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And with us again to kind of try to


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maybe answer some of that is Professor


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Fred Watson, astronomer at large. Hello,


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Fred.


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>> Hello, Andrew. Um, kind of is probably


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the best description really, isn't it?


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[laughter]


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>> Possibly. So, possibly so. Um, but you


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know, it's good to get questions. We've


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got a whole new batch. So, um, let's get


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stuck straight into it. Our first


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question comes from, um, uh, I I love


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the way he always ends his questions.


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I'm not going to reveal anything, but um


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let's hear from Roger.


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>> Hey there, space nuts. This is Roger the


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truck driver. Tonight I'm in uh Rutland,


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Vermont.


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Got a question about the red shift of


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galaxies.


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Um if the light that we're seeing from a


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far off galaxy is shifted to the red and


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it started out at a higher frequency,


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doesn't that mean energy's lost


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somewhere between here and there? And is


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that energy just transferred into space?


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And if it is, does that contribute to


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the expansion of space? And I'm not


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saying it's dark energy, but it is does


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it contribute to it or does that energy


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get dissipated in another way? All


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right. Always digging the show. You guys


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keep on trucking.


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[laughter] I love that. I love that. Uh


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we got train drivers that do that.


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Unfortunately, they do it at 3:00 in the


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morning. [gasps]


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Although today he did it at 10 to 7, I


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was pretty annoyed. Pretty annoyed.


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>> This is uh the one going past your


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place.


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>> Yeah, behind our place there's a rail


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line. It doesn't get used a heck of a


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lot, but when it does, um yes, the the


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glasses rattle. Uh the ones on my face,


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I mean. Uh thanks, Roger. Great


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question. Uh so um yeah the change in


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frequency with the um energy loss um


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where does the energy go and does it


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contribute to the expansion of the


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universe and could it possibly be maybe


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maybe not dark matter or dark energy


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>> or something.


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>> Yeah.


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>> Yeah. Um there's a lot he packed a lot


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into that question.


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>> He did and it's a great question too. Uh


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and you know I mean it's a um project is


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absolutely right the conservation of


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energy uh energy can't be created or


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destroyed. That's the the fundamental


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rule. Uh it's energy is always conserved


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[snorts] but


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uh the universe doesn't play by the


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ordinary rules.


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Uh and um it it's a it's an interesting


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answer here. Um and and I have to say


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it's changed my view of what this you


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know what the answer to this problem


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was.


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>> Okay.


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>> Uh because um when we've been asked this


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before been asked it for a long time I


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just assumed that the energy uh


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basically was absorbed by the universe


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by spacetime


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uh and maybe contributed to the


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expansion. Although there's it's a it's


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a you can't have it both ways because


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it's the expansion that's causing the


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the photon's energy to be to be lost. Uh


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and and just stepping back exactly as


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Roger said, uh you've got light going


00:04:13.680 --> 00:04:17.189
through the universe. It's uh the its


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wavelength is being stretched by the


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expansion of the universe. Therefore,


00:04:21.359 --> 00:04:24.150
the light is losing energy because the


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energy of a beam of light is all about


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the frequency of the light. In other


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words, or the wavelength, putting it


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another way.


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>> So, if you increase the wavelength, you


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lose energy and that's that's um a given


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already. Uh so, what I used to say was


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yes, it kind of goes into the universe,


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but um I've done a bit more reading on


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this and I was wrong. Oh.


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[sighs and gasps]


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Um because


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when you apply general relativity to the


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universe as a whole and that's the as


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we've talked about and we talked about


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it at length in the last episode it's uh


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the the kind of fundamental rule that


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governs everything that we understand in


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the universe. Um when you apply general


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relativity


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uh that conservation of energy that we


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expect to happen in the everyday world


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uh it doesn't hold good. So uh energy is


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not conserved in an expanding universe.


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>> Oh


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>> uh and so basically the energy simply


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disappears.


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It's just not there anymore because of


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the expansion of the universe. It's not


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causing the expansion of the universe.


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It's not create contributing to dark


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energy or dark matter, the energy loss.


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It just vanishes.


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>> Wow.


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>> So, work that one out.


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>> I can't. [snorts]


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>> No, I can't either. [laughter]


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>> Uh it's um it's I I kind of really need


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to look at the equations on this.


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>> Um you don't show them to me. I mean,


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I'm yeah I'm not that keen on looking at


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them myself either got too much else to


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do but uh but um uh but that's yes that


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is the thinking on this uh and I think


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the conservation rule does not work uh


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when it comes to


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um when it comes to consu to to to the


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universe on a whole.


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>> Yeah. Wow. Gee, that's um that's quite a


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revelation. And who who figured that


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out?


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>> Uh [sighs]


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uh it's on a number of uh different


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physics uh related.


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>> There's there there's the reason no one


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knows about it cuz it's physics and


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[laughter]


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who reads that stuff?


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>> Yeah. I think I think the relativistic


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bit of it


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>> uh comes from the fact that the energy


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of a particle which is what we're


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talking about it's an observer dependent


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quantity and so that's why relativity


00:07:07.680 --> 00:07:09.589
plays a part in this because you're the


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observer and and you're talking about


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something that's relative to another


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observer i.e. the photon.


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>> Yeah. Uh, and that's why you've got, you


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know, a relivist a relativistic uh,


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access to it.


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>> Wow. Okay. Um, great question, Roger.


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I'm not sure you were expecting that


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answer, but uh, there it is. Uh, the


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energy just


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gone,


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goes, vanishes, ceases to exist. It's a


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dead poly.


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So


00:07:43.599 --> 00:07:47.350
anyway, um, no one got that joke. I was,


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um, I was doing a Montipython skit for


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some reason.


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>> Yeah. Yeah, you were. That's right. I'm


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I'm Look, I'm pursuing this in a little


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bit more detail and, uh, and just trying


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to, you know, see whether we've got


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alternative alternative views of this.


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>> Generally speaking, you do get


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alternative views when it comes to this


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kind.


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>> That's right.


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>> Um, yes. So, so the the that's right. Uh


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I think I think the the standard


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explanation today is that energy is not


00:08:20.080 --> 00:08:23.589
is not conserved. Okay, we'll leave it


00:08:23.599 --> 00:08:25.189
at that until somebody throws another


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spanner into the


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>> Yeah, we might be giving a different


00:08:27.680 --> 00:08:28.710
answer next week.


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>> It could be. [laughter] Thanks, Roger.


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Great to hear from you. Toot toot. Uh


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we'll catch you next time. Our next


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question comes from Peter. He's from San


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Diego, California. While listening to


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another astrophysics podcast, I heard


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the term dark photon for the first time.


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Apparently, this is a particle


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astrophysicists are seeking in order to


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explain dark matter and/or dark energy.


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Could you please elaborate on what a


00:08:54.399 --> 00:08:58.550
dark photon could be? Um, dad joke for


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Andrew. A photon travels at the speed of


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light. Does that mean a dark photon


00:09:03.519 --> 00:09:06.266
travels at the speed of dark?


00:09:06.276 --> 00:09:06.870
>> [laughter]


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>> I like that. That's good.


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>> That's really good. Keep up the great


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work, he says. Uh, thank you, Peter.


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Hope all is well in San Diego,


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California.


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>> Uh, have you ever heard of a dark


00:09:17.920 --> 00:09:20.710
photon, Fred? Um, yes. I've probably got


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a few in this box here. [laughter]


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Um, your the speed of dark just just


00:09:25.760 --> 00:09:29.430
going back to that that quip. Uh there


00:09:29.440 --> 00:09:33.430
was a story I read uh probably a


00:09:33.440 --> 00:09:37.829
fortnight ago uh about exactly this in


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that darkness


00:09:40.720 --> 00:09:43.350
can move faster than the speed of light.


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>> No, [clears throat]


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it it's but it's a an illusory darkness.


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is when you've got um light beams


00:09:52.640 --> 00:09:55.430
interfering with one another so that


00:09:55.440 --> 00:09:58.550
you've that and interference


00:09:58.560 --> 00:10:00.630
light beams can cancel out. So if you've


00:10:00.640 --> 00:10:02.710
got two light waves and you add them up


00:10:02.720 --> 00:10:04.470
out of phase, they can cancel out and


00:10:04.480 --> 00:10:06.550
you get darkness.


00:10:06.560 --> 00:10:07.829
>> That's well-known principle of


00:10:07.839 --> 00:10:09.750
intererometry. I used to play with that


00:10:09.760 --> 00:10:13.190
when I was a student a lot. Uh but there


00:10:13.200 --> 00:10:14.870
are certain circumstances that those


00:10:14.880 --> 00:10:18.630
patterns of darkness can actually exceed


00:10:18.640 --> 00:10:21.190
the speed of light because they're not


00:10:21.200 --> 00:10:22.949
actually real. They're not real


00:10:22.959 --> 00:10:24.790
entities. They're not a thing that's


00:10:24.800 --> 00:10:26.470
carrying any sort of information or


00:10:26.480 --> 00:10:29.452
energy. They're just patterns in a in an


00:10:29.462 --> 00:10:30.470
[clears throat] interference pattern.


00:10:30.480 --> 00:10:32.230
They're just dark patches in it. And I


00:10:32.240 --> 00:10:33.990
think under certain circumstances, they


00:10:34.000 --> 00:10:36.949
could go faster than the speed of light.


00:10:36.959 --> 00:10:40.069
So, darkness might be not quite as uh


00:10:40.079 --> 00:10:43.190
you know as twe as you thought it was,


00:10:43.200 --> 00:10:43.829
>> I guess.


00:10:43.839 --> 00:10:47.590
>> Anyway, anyway, uh that's not the the


00:10:47.600 --> 00:10:50.069
question. Uh because dark photons are


00:10:50.079 --> 00:10:51.990
definitely something different and


00:10:52.000 --> 00:10:54.230
they're basically


00:10:54.240 --> 00:10:56.949
uh hypothetical. They've been


00:10:56.959 --> 00:10:59.269
hypothesized by physicists and


00:10:59.279 --> 00:11:00.790
cosmologists


00:11:00.800 --> 00:11:05.590
as being a force carrier similar to the


00:11:05.600 --> 00:11:09.750
ordinary photon but related to


00:11:09.760 --> 00:11:12.389
dark matter.


00:11:12.399 --> 00:11:15.430
In in other words, you might have Sorry,


00:11:15.440 --> 00:11:17.110
somebody's trying to phone me. I'm just


00:11:17.120 --> 00:11:18.790
going to kill that call.


00:11:18.800 --> 00:11:19.350
>> Yeah.


00:11:19.360 --> 00:11:21.190
>> Uh um


00:11:21.200 --> 00:11:24.472
>> that was me. That was me. No, it wasn't.


00:11:24.482 --> 00:11:25.782
[laughter]


00:11:25.792 --> 00:11:26.310
>> [sighs and gasps]


00:11:26.320 --> 00:11:27.990
>> They're they're you know they're part of


00:11:28.000 --> 00:11:30.949
the there may be when we discover


00:11:30.959 --> 00:11:34.150
finally what dark matter is there may be


00:11:34.160 --> 00:11:38.389
a suite of dark particles


00:11:38.399 --> 00:11:40.470
which could include dark photons. That's


00:11:40.480 --> 00:11:41.990
the line


00:11:42.000 --> 00:11:43.110
>> right?


00:11:43.120 --> 00:11:45.269
>> And and so you know we mentioned last


00:11:45.279 --> 00:11:48.310
week the or the last episode the uh the


00:11:48.320 --> 00:11:50.630
large hydrron collider being upgraded to


00:11:50.640 --> 00:11:52.470
be the high luminosity large hydrron


00:11:52.480 --> 00:11:55.670
collider. Um, that's one of the things


00:11:55.680 --> 00:11:57.110
they'd be looking for will be dark


00:11:57.120 --> 00:11:58.870
photons.


00:11:58.880 --> 00:12:04.230
Okay. Uh, yeah, I tried to do a um an AI


00:12:04.240 --> 00:12:07.509
search for an explanation on it and um


00:12:07.519 --> 00:12:09.670
it it it sort of gave me all this gobbly


00:12:09.680 --> 00:12:13.030
but um you know what would a dark


00:12:13.040 --> 00:12:16.150
proton photon do? It says it would carry


00:12:16.160 --> 00:12:19.269
a force within the dark sector.


00:12:19.279 --> 00:12:21.430
We call that the government. uh it might


00:12:21.440 --> 00:12:23.430
allow dark matter particles to interact


00:12:23.440 --> 00:12:25.430
with each other and it could very weakly


00:12:25.440 --> 00:12:27.910
mix with normal photons giving us a way


00:12:27.920 --> 00:12:30.710
to detect it. And the reason they reckon


00:12:30.720 --> 00:12:33.110
that scientists care about this is as


00:12:33.120 --> 00:12:35.350
you said could explain what dark matter


00:12:35.360 --> 00:12:38.230
is made of. So therefore solving some of


00:12:38.240 --> 00:12:40.310
those gaps in our current physics


00:12:40.320 --> 00:12:42.389
theories.


00:12:42.399 --> 00:12:44.550
So that's that's that's why people are


00:12:44.560 --> 00:12:45.750
interested in this and that's why


00:12:45.760 --> 00:12:47.350
they're upgrading the Large Hadron


00:12:47.360 --> 00:12:49.110
Collider and


00:12:49.120 --> 00:12:52.470
>> hopefully we will learn more in years to


00:12:52.480 --> 00:12:55.829
come. That's that's the that's the hope.


00:12:55.839 --> 00:12:57.590
That's the hope. Yeah. So we might you


00:12:57.600 --> 00:12:59.269
know we might be talking one day about


00:12:59.279 --> 00:13:01.829
dark photons um having been detected


00:13:01.839 --> 00:13:03.430
which would be


00:13:03.440 --> 00:13:05.910
>> a coup for space nukes.


00:13:05.920 --> 00:13:08.389
>> Yes, it will. Uh but at this stage uh


00:13:08.399 --> 00:13:10.949
they are not proven. It's just a theory.


00:13:10.959 --> 00:13:13.030
So that's That's about as much as we


00:13:13.040 --> 00:13:15.030
know at this point in time.


00:13:15.040 --> 00:13:17.750
>> But uh very good question uh and thank


00:13:17.760 --> 00:13:19.990
you Peter for sending it in. This is


00:13:20.000 --> 00:13:22.069
Space Nuts with Andrew Dunley and


00:13:22.079 --> 00:13:25.590
Professor Fred Watson.


00:13:25.600 --> 00:13:27.350
Let's take a short break from the show


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>> And I feel


00:15:15.279 --> 00:15:17.430
>> Space Nuts. Okay, Fred, we'll move


00:15:17.440 --> 00:15:19.430
straight on to our next question, which


00:15:19.440 --> 00:15:23.430
is uh another audio question from Eli.


00:15:23.440 --> 00:15:27.829
Hello, this is Eli from sunny Coachella


00:15:27.839 --> 00:15:30.870
Valley in California.


00:15:30.880 --> 00:15:33.430
I'm embarrassed to admit it, but I still


00:15:33.440 --> 00:15:35.189
can't get my head around deep space


00:15:35.199 --> 00:15:38.230
astronomy. I get that the light from say


00:15:38.240 --> 00:15:41.910
a distant galaxy is a billion years old.


00:15:41.920 --> 00:15:44.550
But why that particular point in its


00:15:44.560 --> 00:15:47.189
time? Is it just a matter of whatever


00:15:47.199 --> 00:15:49.749
light is hitting us is the time we get


00:15:49.759 --> 00:15:51.749
to see?


00:15:51.759 --> 00:15:55.910
But for really early light, the JWST


00:15:55.920 --> 00:15:57.910
early universe stuff that's been


00:15:57.920 --> 00:16:01.269
traveling for 13 billion years and just


00:16:01.279 --> 00:16:04.310
hitting us now. Are we looking for the


00:16:04.320 --> 00:16:07.509
light that hasn't passed us by or hasn't


00:16:07.519 --> 00:16:10.710
made it here yet, but is from that one


00:16:10.720 --> 00:16:14.150
precise location long ago?


00:16:14.160 --> 00:16:16.550
This stuff is so difficult to get my


00:16:16.560 --> 00:16:19.829
head around. Love the show and hope you


00:16:19.839 --> 00:16:22.629
guys can clear this up for me.


00:16:22.639 --> 00:16:25.189
>> Uh, no we can't. We just thought we'd um


00:16:25.199 --> 00:16:27.990
put the question in there. Uh, thanks


00:16:28.000 --> 00:16:31.430
Eli. Uh it this is a deep um not only in


00:16:31.440 --> 00:16:33.509
deep space astronomy terms but it is a


00:16:33.519 --> 00:16:37.269
deep deep topic. Uh I mean when we look


00:16:37.279 --> 00:16:39.590
up into the sky at night and we see all


00:16:39.600 --> 00:16:42.389
those beautiful colored dots we are


00:16:42.399 --> 00:16:44.629
looking at history and it's variable


00:16:44.639 --> 00:16:47.829
history because some of it's 4.41 light


00:16:47.839 --> 00:16:51.269
years away and some of it's 400,000


00:16:51.279 --> 00:16:53.590
light years away. Some of it's further


00:16:53.600 --> 00:16:55.590
than that. It's um but then you've got


00:16:55.600 --> 00:16:58.069
the cosmic microwave background


00:16:58.079 --> 00:17:00.870
radiation which is kind of a leftover of


00:17:00.880 --> 00:17:03.430
of um [gasps]


00:17:03.440 --> 00:17:05.990
what happened after the big bang and


00:17:06.000 --> 00:17:08.470
that that's that's a different kettle to


00:17:08.480 --> 00:17:10.630
fish and I can understand why you got a


00:17:10.640 --> 00:17:13.591
headache Eli. Over to you Fred.


00:17:13.601 --> 00:17:14.470
[laughter]


00:17:14.480 --> 00:17:20.789
Thanks. Um so I guess you know that I I


00:17:20.799 --> 00:17:25.110
understand Eli's issue as well. um


00:17:25.120 --> 00:17:27.110
you you've got to be in the right place


00:17:27.120 --> 00:17:29.190
at the right time to see a photon from a


00:17:29.200 --> 00:17:32.789
distant galaxy. But I I guess the way to


00:17:32.799 --> 00:17:36.230
envisage this is if you think of the


00:17:36.240 --> 00:17:40.070
universe um and you've got to perhaps


00:17:40.080 --> 00:17:41.750
think of it as if you were looking at it


00:17:41.760 --> 00:17:43.590
from the outside, which we never can.


00:17:43.600 --> 00:17:46.150
But uh if you can think of it that way,


00:17:46.160 --> 00:17:48.950
then it's full of objects which are


00:17:48.960 --> 00:17:52.549
radiating light even in its infancy.


00:17:52.559 --> 00:17:54.150
when the universe was very young, the


00:17:54.160 --> 00:17:57.270
stuff in it was basically shining. Um


00:17:57.280 --> 00:17:59.350
once we got past the dark ages where no


00:17:59.360 --> 00:18:03.190
stars were shining, uh but um and those


00:18:03.200 --> 00:18:05.430
are the galaxies that we now see. So so


00:18:05.440 --> 00:18:08.310
they're constantly radiating light and


00:18:08.320 --> 00:18:10.310
that's like just like a river of light


00:18:10.320 --> 00:18:12.230
that's flowing


00:18:12.240 --> 00:18:15.350
down time, if I can put it that way. Uh


00:18:15.360 --> 00:18:19.669
and a long time in in the future, it


00:18:19.679 --> 00:18:22.630
reaches us. But it's not just, you know,


00:18:22.640 --> 00:18:25.110
an individual photon or something that's


00:18:25.120 --> 00:18:27.430
reaching us. It's this stream of stuff


00:18:27.440 --> 00:18:30.470
that is being radiated throughout the


00:18:30.480 --> 00:18:34.070
universe by these galaxies. So we um and


00:18:34.080 --> 00:18:37.270
and we we pick it up. We pick it up


00:18:37.280 --> 00:18:39.029
sometimes as exactly as you've said,


00:18:39.039 --> 00:18:40.870
well up to 10 billion years after it's


00:18:40.880 --> 00:18:43.350
been radiated. I think


00:18:43.360 --> 00:18:45.830
>> 12 billion years are the are the oldest


00:18:45.840 --> 00:18:47.830
or the earliest galaxies that we now


00:18:47.840 --> 00:18:49.510
see. We're looking back in time. 12


00:18:49.520 --> 00:18:51.750
billion years and seeing them as they


00:18:51.760 --> 00:18:54.470
were perhaps a billion and a half years


00:18:54.480 --> 00:18:57.190
after the big bang. Um, and they're they


00:18:57.200 --> 00:18:59.350
are shining. They're radiating light uh


00:18:59.360 --> 00:19:01.830
in the early universe and down the track


00:19:01.840 --> 00:19:03.830
that reaches us because that light's


00:19:03.840 --> 00:19:05.590
going in all directions. So, it wouldn't


00:19:05.600 --> 00:19:08.310
matter where in the universe we were, we


00:19:08.320 --> 00:19:10.870
would still see them. Uh, we'd just see


00:19:10.880 --> 00:19:12.549
them in a, you know, in a different


00:19:12.559 --> 00:19:14.630
position in the sky if we're a long way


00:19:14.640 --> 00:19:15.990
from where we are now.


00:19:16.000 --> 00:19:19.990
>> Yeah. Um but yeah so I I guess it's you


00:19:20.000 --> 00:19:22.549
know in a way one way of thinking about


00:19:22.559 --> 00:19:25.430
this is if you imagine us on planet


00:19:25.440 --> 00:19:28.390
earth here and imagine us being


00:19:28.400 --> 00:19:32.630
surrounded by a whole series of shells


00:19:32.640 --> 00:19:34.630
uh which we're at the center of and this


00:19:34.640 --> 00:19:36.310
is a bit like the crystalline spheres


00:19:36.320 --> 00:19:38.470
that people used to think uh the


00:19:38.480 --> 00:19:41.590
universe was made of. Uh but these these


00:19:41.600 --> 00:19:44.549
shells uh spherical shells all centered


00:19:44.559 --> 00:19:47.590
on the earth but each one clicks over to


00:19:47.600 --> 00:19:51.669
a to a a time further in the past. Uh


00:19:51.679 --> 00:19:53.510
because the lights coming to us from the


00:19:53.520 --> 00:19:55.990
whole the whole cosmos which is full of


00:19:56.000 --> 00:19:58.390
stuff. Uh and that's why we can see


00:19:58.400 --> 00:20:00.230
these these shells sort of being


00:20:00.240 --> 00:20:02.710
illuminated in a way by the objects that


00:20:02.720 --> 00:20:05.830
uh that radiated them at that time. uh


00:20:05.840 --> 00:20:09.270
that has um that we see them because of


00:20:09.280 --> 00:20:11.590
the the distance that they are away from


00:20:11.600 --> 00:20:13.909
us means that they've the light has


00:20:13.919 --> 00:20:15.990
taken that long to get to us. Whether


00:20:16.000 --> 00:20:17.990
that helps or not in fact I think I've


00:20:18.000 --> 00:20:20.924
just confused it completely but


00:20:20.934 --> 00:20:21.830
[snorts]


00:20:21.840 --> 00:20:25.029
um I


00:20:25.039 --> 00:20:27.750
just doing a little experimental search


00:20:27.760 --> 00:20:30.789
here for a sec.


00:20:30.799 --> 00:20:34.390
What what I I I agree with in terms of


00:20:34.400 --> 00:20:36.630
Eli's question and and getting your head


00:20:36.640 --> 00:20:40.230
around it is um if Beetlejuice or


00:20:40.240 --> 00:20:42.149
however you want to pronounce it went


00:20:42.159 --> 00:20:47.029
supernova right now as we were speaking


00:20:47.039 --> 00:20:50.230
>> we wouldn't see it for


00:20:50.240 --> 00:20:52.470
640 years.


00:20:52.480 --> 00:20:53.669
>> Yeah.


00:20:53.679 --> 00:20:57.350
So for it to have gone supernova in the


00:20:57.360 --> 00:21:00.230
past and us to witness it, it has to


00:21:00.240 --> 00:21:02.470
have happened


00:21:02.480 --> 00:21:06.230
pretty close to 640 years ago. Does that


00:21:06.240 --> 00:21:07.110
make sense?


00:21:07.120 --> 00:21:09.830
>> Yes. Um so you could think of that in


00:21:09.840 --> 00:21:13.909
another way. Um you know um anywhere


00:21:13.919 --> 00:21:16.630
between us and 640 light years away


00:21:16.640 --> 00:21:18.710
there could be this pulse of light


00:21:18.720 --> 00:21:20.789
that's on its way to us


00:21:20.799 --> 00:21:23.909
>> from Beetlejuice. uh it would spread out


00:21:23.919 --> 00:21:26.470
in a sphere uh and as that sphere


00:21:26.480 --> 00:21:28.549
expanded eventually it would wash over


00:21:28.559 --> 00:21:31.590
the earth and we'd see it um and perhaps


00:21:31.600 --> 00:21:33.350
see it during the day as well because it


00:21:33.360 --> 00:21:35.270
might get bright enough to do that.


00:21:35.280 --> 00:21:37.350
>> Uh and and I think that's a really good


00:21:37.360 --> 00:21:39.669
way of putting it, Andrew, because um


00:21:39.679 --> 00:21:41.029
thinking about the galaxies, they're


00:21:41.039 --> 00:21:43.029
just streaming light out all the time.


00:21:43.039 --> 00:21:45.750
But something like uh a supernova


00:21:45.760 --> 00:21:47.909
explosion which gives a big pulse of


00:21:47.919 --> 00:21:50.710
light um that's perhaps easier to get


00:21:50.720 --> 00:21:52.549
your head around because that's that's


00:21:52.559 --> 00:21:57.029
just got a um it'll take whatever


00:21:57.039 --> 00:21:59.029
whatever time is represented by the


00:21:59.039 --> 00:22:02.310
distance away. So 640 light years away.


00:22:02.320 --> 00:22:04.549
It'll take 640 years to get here for


00:22:04.559 --> 00:22:06.470
that pulse to get here. But then it will


00:22:06.480 --> 00:22:09.190
sweep over us uh and we'll see the light


00:22:09.200 --> 00:22:11.110
the the light fading away.


00:22:11.120 --> 00:22:15.190
>> Yeah. And um the reason I chose that


00:22:15.200 --> 00:22:18.149
target is because there's a lot of


00:22:18.159 --> 00:22:20.710
conjecture about its future and the


00:22:20.720 --> 00:22:22.390
possibility that it's reaching that


00:22:22.400 --> 00:22:23.909
critical mass point.


00:22:23.919 --> 00:22:24.710
>> Yes.


00:22:24.720 --> 00:22:26.390
>> Um but it could have already happened.


00:22:26.400 --> 00:22:28.789
That's the other thing. [laughter]


00:22:28.799 --> 00:22:30.870
>> But we that's that's something we can


00:22:30.880 --> 00:22:33.029
have no knowledge of. That's the the key


00:22:33.039 --> 00:22:35.669
thing because um we are limited by the


00:22:35.679 --> 00:22:37.669
speed of light. That's the thing that


00:22:37.679 --> 00:22:39.350
always limits our view of the universe.


00:22:39.360 --> 00:22:41.830
And just to confuse Eli a little bit


00:22:41.840 --> 00:22:45.590
more, there are probably things in the


00:22:45.600 --> 00:22:47.430
universe we will never witness because


00:22:47.440 --> 00:22:49.590
the light is just too far away to reach


00:22:49.600 --> 00:22:51.909
us in any reasonable amount of time.


00:22:51.919 --> 00:22:53.350
Even even


00:22:53.360 --> 00:22:56.149
>> beyond the life of the earth itself or


00:22:56.159 --> 00:22:57.430
or our sun,


00:22:57.440 --> 00:23:01.110
>> we we we there are things we will never


00:23:01.120 --> 00:23:03.350
ever know about.


00:23:03.360 --> 00:23:04.390
>> Correct.


00:23:04.400 --> 00:23:06.870
>> It's um and that's where it just gives


00:23:06.880 --> 00:23:08.605
you um


00:23:08.615 --> 00:23:09.110
>> [snorts and laughter]


00:23:09.120 --> 00:23:11.110
>> one of those headaches that uh requires


00:23:11.120 --> 00:23:13.909
you to take paracetamol and ibuprofen at


00:23:13.919 --> 00:23:17.776
the same time. So,


00:23:17.786 --> 00:23:18.870
[laughter]


00:23:18.880 --> 00:23:21.350
>> um deep deep headaches. But Eli, great


00:23:21.360 --> 00:23:23.110
question. I'm not sure we solved your


00:23:23.120 --> 00:23:27.830
problem, but um anyway, uh it it I I try


00:23:27.840 --> 00:23:29.190
to explain this sort of stuff to my


00:23:29.200 --> 00:23:33.510
grandson uh and my granddaughters and


00:23:33.520 --> 00:23:36.230
you know, how do you explain time and


00:23:36.240 --> 00:23:40.549
distance to a to a a young child and um


00:23:40.559 --> 00:23:41.430
when you're trying to get through


00:23:41.440 --> 00:23:43.750
traffic, it's [laughter]


00:23:43.760 --> 00:23:45.190
>> that might not be the best time to do


00:23:45.200 --> 00:23:45.510
it.


00:23:45.520 --> 00:23:46.789
>> Probably not, but they're very


00:23:46.799 --> 00:23:47.990
interested.


00:23:48.000 --> 00:23:50.149
>> Very interested. Thanks, Eli. Great


00:23:50.159 --> 00:23:53.029
question.


00:23:53.039 --> 00:23:55.430
The crew of Artemis 2 now bound for the


00:23:55.440 --> 00:23:57.909
moon. Humanity's next great voyage


00:23:57.919 --> 00:23:59.270
begins.


00:23:59.280 --> 00:24:03.270
>> Space nuts. Our final question uh comes


00:24:03.280 --> 00:24:07.029
from Nova Scotia. It's from Ken. Uh


00:24:07.039 --> 00:24:08.470
look, this is an old chestnut. We've


00:24:08.480 --> 00:24:10.950
we've probably spoken about this many


00:24:10.960 --> 00:24:13.510
times, but it's always good to um to to


00:24:13.520 --> 00:24:15.990
revisit. If the universe is expanding,


00:24:16.000 --> 00:24:20.070
what is it expanding into? And also is


00:24:20.080 --> 00:24:23.269
the universe spherical?


00:24:23.279 --> 00:24:25.669
So um yes, what's it expanding into?


00:24:25.679 --> 00:24:29.350
Well, we don't know. And yes,


00:24:29.360 --> 00:24:32.230
>> that's yes. Uh it's actually we don't


00:24:32.240 --> 00:24:33.110
know and maybe


00:24:33.120 --> 00:24:35.110
>> and maybe maybe.


00:24:35.120 --> 00:24:39.669
>> So um the the universe is everything


00:24:39.679 --> 00:24:41.909
that we can detect. That's the


00:24:41.919 --> 00:24:43.269
definition of the universe. Everything


00:24:43.279 --> 00:24:46.870
we can measure or detect. And that means


00:24:46.880 --> 00:24:49.909
and we observe the expansion


00:24:49.919 --> 00:24:52.470
but we don't know whether there's an


00:24:52.480 --> 00:24:54.070
edge to the universe. We don't know


00:24:54.080 --> 00:24:55.990
whether it's infinite. We don't know


00:24:56.000 --> 00:24:58.390
anything beyond the horizons that we


00:24:58.400 --> 00:25:00.549
see. And the most obvious one is the


00:25:00.559 --> 00:25:03.350
cosmic microwave background radiation


00:25:03.360 --> 00:25:05.669
um which beyond which we can't see. But


00:25:05.679 --> 00:25:07.430
the universe almost certainly goes on be


00:25:07.440 --> 00:25:09.909
beyond that probably for a very long


00:25:09.919 --> 00:25:12.230
way. It may be very big. But we've got


00:25:12.240 --> 00:25:14.950
no knowledge of a boundary or or any


00:25:14.960 --> 00:25:17.029
other medium that it might be expanding


00:25:17.039 --> 00:25:18.310
into.


00:25:18.320 --> 00:25:22.470
>> So um one possibility is the idea of


00:25:22.480 --> 00:25:27.029
multiple universes and they might exist


00:25:27.039 --> 00:25:30.789
maybe in a higher dimensional


00:25:30.799 --> 00:25:34.630
uh arena if I can put it that way. you


00:25:34.640 --> 00:25:37.990
know, if you've if if you can um find


00:25:38.000 --> 00:25:40.789
that there are extra dimensions, we we


00:25:40.799 --> 00:25:42.789
know the three dimensions of space and


00:25:42.799 --> 00:25:45.830
one of time, that's what we've got now.


00:25:45.840 --> 00:25:49.750
Um but uh if there are hidden extra


00:25:49.760 --> 00:25:53.029
dimensions, maybe they provide a venue


00:25:53.039 --> 00:25:56.870
for the universe to expand into. Uh and


00:25:56.880 --> 00:25:59.350
there are various theories that accept


00:25:59.360 --> 00:26:02.630
that. um M theory is one of them where M


00:26:02.640 --> 00:26:04.470
is probably an abbreviation for


00:26:04.480 --> 00:26:06.310
membrane. The idea is that the universe


00:26:06.320 --> 00:26:08.390
is can be collapsed onto a


00:26:08.400 --> 00:26:10.470
two-dimensional membrane and there are


00:26:10.480 --> 00:26:12.870
lots of these membranes in the univer in


00:26:12.880 --> 00:26:15.110
the in the kind of higher dimensional


00:26:15.120 --> 00:26:17.190
universe but that's just conjecture and


00:26:17.200 --> 00:26:20.230
we've got no mechanism for proving that


00:26:20.240 --> 00:26:22.149
at the moment the only thing we know


00:26:22.159 --> 00:26:24.230
with certainty with absolute certainty


00:26:24.240 --> 00:26:26.230
is that the universe is expanding.


00:26:26.240 --> 00:26:28.230
>> Yes. uh at an accelerating rate,


00:26:28.240 --> 00:26:29.990
although the accelerating rate's not as


00:26:30.000 --> 00:26:32.390
accelerating as it once was. Possibly.


00:26:32.400 --> 00:26:33.110
>> Possibly.


00:26:33.120 --> 00:26:35.350
>> Um yeah, there there's there's three


00:26:35.360 --> 00:26:38.710
possible shapes of the universe. He asks


00:26:38.720 --> 00:26:41.909
it's if it's a a sphere. Um there's uh


00:26:41.919 --> 00:26:43.909
the flat universe theory. Oh, do we have


00:26:43.919 --> 00:26:46.310
to go there? Uh there's the closed


00:26:46.320 --> 00:26:49.190
universe theory, which is the positive


00:26:49.200 --> 00:26:52.390
curvature, so a sphere. or the open


00:26:52.400 --> 00:26:54.390
universe theory which is negative


00:26:54.400 --> 00:26:56.390
curvature. So it's more like the shape


00:26:56.400 --> 00:26:57.909
of a saddle.


00:26:57.919 --> 00:27:01.909
>> From what I'm reading, the most popular


00:27:01.919 --> 00:27:04.710
>> likelihood is the flat universe theory,


00:27:04.720 --> 00:27:07.350
>> but it but it's only flat in a ukidian


00:27:07.360 --> 00:27:10.230
sense. It doesn't mean it's shaped like


00:27:10.240 --> 00:27:11.830
a tabletop.


00:27:11.840 --> 00:27:14.149
>> Uh it means that parallel lines never


00:27:14.159 --> 00:27:16.549
meet. Basically, that's what we mean by


00:27:16.559 --> 00:27:17.909
flat. It's the the shape of the


00:27:17.919 --> 00:27:20.870
geometry. And the other thing that they


00:27:20.880 --> 00:27:23.750
suggest is that um you know it can be


00:27:23.760 --> 00:27:25.750
flat and still expanding as you said uh


00:27:25.760 --> 00:27:28.390
it might be infinite. We've we've talked


00:27:28.400 --> 00:27:30.630
about that before and there is likely no


00:27:30.640 --> 00:27:32.870
center and no edge.


00:27:32.880 --> 00:27:35.190
>> Correct. That's what we believe.


00:27:35.200 --> 00:27:40.310
>> Yeah. Now um to its shape so


00:27:40.320 --> 00:27:42.789
uh so


00:27:42.799 --> 00:27:45.029
basically I think Ken's question is is


00:27:45.039 --> 00:27:47.110
it spherical


00:27:47.120 --> 00:27:49.990
>> and we don't know the answer to that. We


00:27:50.000 --> 00:27:52.950
we know that the volume within which we


00:27:52.960 --> 00:27:56.950
can detect is spherical because the the


00:27:56.960 --> 00:27:59.350
cosmic microwave background radiation


00:27:59.360 --> 00:28:02.789
forms a an imaginary shell all around


00:28:02.799 --> 00:28:05.990
all around our galaxy. And it's the same


00:28:06.000 --> 00:28:08.149
distance in every direction. So in that


00:28:08.159 --> 00:28:10.549
regard, it's what we call isotropic, the


00:28:10.559 --> 00:28:12.710
same in all directions.


00:28:12.720 --> 00:28:15.110
Uh and that's really the only thing we


00:28:15.120 --> 00:28:18.149
can lay it down to. But there are ideas


00:28:18.159 --> 00:28:20.310
that if you looked at the universe on a


00:28:20.320 --> 00:28:21.990
bigger scale than we could see, it


00:28:22.000 --> 00:28:24.149
wouldn't be that it might be different


00:28:24.159 --> 00:28:26.389
in different directions.


00:28:26.399 --> 00:28:29.029
Um, and that in fact has been


00:28:29.039 --> 00:28:31.190
hypothesized as one of the sources of


00:28:31.200 --> 00:28:33.269
dark energy that we're just seeing a


00:28:33.279 --> 00:28:34.630
local bit of the universe that's


00:28:34.640 --> 00:28:37.590
expanding whose expansion is increasing


00:28:37.600 --> 00:28:40.630
whereas somewhere else it might be


00:28:40.640 --> 00:28:42.310
slowing down the expansion of the


00:28:42.320 --> 00:28:45.669
universe. Um,


00:28:45.679 --> 00:28:45.990
>> yeah,


00:28:46.000 --> 00:28:46.950
>> sorry. Go on.


00:28:46.960 --> 00:28:49.029
>> No, that that would be a a universe


00:28:49.039 --> 00:28:50.789
that's not isotropic. It's not the same


00:28:50.799 --> 00:28:52.630
in all directions, but we assume it's


00:28:52.640 --> 00:28:55.190
isotropic. That's all we can do in our


00:28:55.200 --> 00:28:56.870
assumptions in cosmology.


00:28:56.880 --> 00:28:59.190
>> We just can't see


00:28:59.200 --> 00:29:01.269
beyond what we can see, which sounds


00:29:01.279 --> 00:29:02.789
stupid, but that's that's the way the


00:29:02.799 --> 00:29:03.909
universe is.


00:29:03.919 --> 00:29:04.310
>> Yeah.


00:29:04.320 --> 00:29:06.630
>> Um Yeah. We've got the known universe


00:29:06.640 --> 00:29:08.389
and then the rest.


00:29:08.399 --> 00:29:09.190
>> That's right.


00:29:09.200 --> 00:29:09.909
>> Basically,


00:29:09.919 --> 00:29:11.350
>> and the rest might be a lot bigger than


00:29:11.360 --> 00:29:12.230
the known universe.


00:29:12.240 --> 00:29:14.470
>> We just Yeah. But we just don't know. Um


00:29:14.480 --> 00:29:16.389
I I [clears throat] the only thing I


00:29:16.399 --> 00:29:18.070
thought of is like you look at Earth's


00:29:18.080 --> 00:29:20.310
atmosphere and as you go out it fins and


00:29:20.320 --> 00:29:24.630
so there's no defined line between space


00:29:24.640 --> 00:29:28.310
and the earth proper. Could the universe


00:29:28.320 --> 00:29:30.870
be of the same ilk?


00:29:30.880 --> 00:29:32.950
Yes. But that would imply that the


00:29:32.960 --> 00:29:35.669
spacetime just sort of keeps keeps on


00:29:35.679 --> 00:29:37.990
going. It just might be empty.


00:29:38.000 --> 00:29:39.590
>> Uh


00:29:39.600 --> 00:29:41.029
>> yeah. Don't know.


00:29:41.039 --> 00:29:41.909
>> Don't know more.


00:29:41.919 --> 00:29:44.149
>> We don't know. We don't know.


00:29:44.159 --> 00:29:46.850
>> Why are you asking us? We don't know.


00:29:46.860 --> 00:29:49.350
[laughter]


00:29:49.360 --> 00:29:52.149
>> Oh dear. Um, thank you, Ken. Uh, very


00:29:52.159 --> 00:29:54.070
thoughtprovoking question and thanks for


00:29:54.080 --> 00:29:55.590
sending it in. If you have questions for


00:29:55.600 --> 00:29:58.310
us, please send them to us via our


00:29:58.320 --> 00:30:00.389
website, spacenutspodcast.com,


00:30:00.399 --> 00:30:01.909
spacenuts.io.


00:30:01.919 --> 00:30:03.269
There's a little button at the top


00:30:03.279 --> 00:30:06.149
called AMA, and that's what you click on


00:30:06.159 --> 00:30:08.470
to send us text and audio questions. If


00:30:08.480 --> 00:30:10.149
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00:30:10.159 --> 00:30:12.470
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00:30:12.480 --> 00:30:14.950
smart devices have that and you can send


00:30:14.960 --> 00:30:17.669
it to us in audio form. Don't forget to


00:30:17.679 --> 00:30:18.789
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00:30:18.799 --> 00:30:20.470
from or you can send us a text question.


00:30:20.480 --> 00:30:23.110
Just fill in the blanks. And while


00:30:23.120 --> 00:30:24.310
you're there, have a look around, visit


00:30:24.320 --> 00:30:26.710
the shop, get something from yourself.


00:30:26.720 --> 00:30:29.750
Um you know, whatever you like. And


00:30:29.760 --> 00:30:31.430
we're done. Fred, thank you so much.


00:30:31.440 --> 00:30:34.549
That was a tough one. [laughter]


00:30:34.559 --> 00:30:37.510
Well, we you know, uh Space Nuts always


00:30:37.520 --> 00:30:40.070
probes the limits of knowledge. We does.


00:30:40.080 --> 00:30:40.630
That's what we do.


00:30:40.640 --> 00:30:42.789
>> Unfortunately, I have such limited


00:30:42.799 --> 00:30:44.710
knowledge. I'm not very helpful, but um


00:30:44.720 --> 00:30:45.990
glad you're here.


00:30:46.000 --> 00:30:48.310
>> No, you are very helpful and um so are


00:30:48.320 --> 00:30:50.230
our listeners because they keep on


00:30:50.240 --> 00:30:51.029
probing which


00:30:51.039 --> 00:30:53.350
>> they do indeed. All right, Fred. Thanks


00:30:53.360 --> 00:30:54.549
very much. We'll catch you on the next


00:30:54.559 --> 00:30:55.350
episode.


00:30:55.360 --> 00:30:56.789
>> Sounds great. Thanks, Andrew.


00:30:56.799 --> 00:30:58.310
>> Professor Fred Watson, astronomer at


00:30:58.320 --> 00:31:00.310
large. And thanks to Hugh in the studio,


00:31:00.320 --> 00:31:01.590
who couldn't be with us today because


00:31:01.600 --> 00:31:03.510
he's been expanding at an accelerating


00:31:03.520 --> 00:31:05.510
rate, so he went to the gym. And from


00:31:05.520 --> 00:31:07.110
me, Andrew Dunley, thanks for your


00:31:07.120 --> 00:31:08.310
company. We'll see you on the next


00:31:08.320 --> 00:31:10.549
episode of Space Nuts. Bye-bye.


00:31:10.559 --> 00:31:11.510
>> Space nuts.


00:31:11.520 --> 00:31:13.669
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