Gravitational Waves, Cosmic What-Ifs & Dark Energy Dilemmas | Space Nuts: Astronomy Insights &...

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Language: en

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While the world takes a little bit of a


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rest over the Christmas New Year period,


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we thought we would, too. But we're not


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going to leave you hanging. We've dug


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into the archives and found a few of the


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biggest episodes of recent times. So,


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sit back and enjoy those. And we'll be


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back with new episodes of Space Nuts


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probably in the middle of January. See


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you then. Space Nuts. Hi there. Thanks


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for joining us. This is Space Nuts Q&A.


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My name is Andrew Dunley, your host. And


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coming up on this episode, we got a


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question about gravitational waves and


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the big bang. We're also going to uh


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look at a what if question. Love the


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what if questions. Uh which is asking


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about the life of Earth. Not life on


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Earth, the life of Earth if the sun


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never died. Interesting uh angle. And


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we're also going to look at uh time and


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dark energy. That's all coming up on the


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Q&A edition 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


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>> 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 joining me once again is Professor


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Fred Watson, astronomer at large. Hello


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Fred.


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>> Hi Andrew. How are you doing?


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>> I'm doing as much as I can.


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>> Good. Good. Good, good to be Q&A with


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you.


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>> Yes, you too. Um, shall we get stuck


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straight in?


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>> Why not? Yes, why not?


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>> All right. Uh, our first question comes


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I'm not sure if it's Bo or Boa. I'll


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have to listen more carefully. Here we


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go.


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>> Hello, Fred and Andrew. Is Bo here from


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Melbourne? I hope you're well. I have a


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question for you, and it is not about


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dark energy, nor it is about dark


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matter, but it is about gravitational


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waves. It's a straightforward question.


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Did the big bang produce gravitational


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waves? As we understand it,


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gravitational waves are generated when


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two massive bodies such as neutron stars


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and black holes collided each other and


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cause that ripple in the fabric of


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spacetime.


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But when the universe as just began uh


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in infinite density and so forth when it


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came into existence via the big bang did


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it produce gravitational waves or echoes


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and can we detect those echoes in space


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and time very much like the cosmic


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microwave background radiation that we


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see today. Anyway, I hope that makes


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sense. I'd love to hear your answer.


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Thank you very much.


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>> Thank you Boa. Um that's a good


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question. I you know we talk about the


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big bang a lot. We get a lot of


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questions about it. Uh and I mean it was


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a a massive event. We don't know why. We


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don't know a lot but uh we know we can


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see that it happened through the cosmic


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microwave background radiation that's


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still evident today. But gravitational


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waves would I mean if the universe


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didn't exist at the moment of the big


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bang and was being created as a


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consequence of that


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I'm not sure gravitational waves could


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have happened the way we understand them


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with other events in our universe. So um


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yeah I'm not sure about this one. So um


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the the thing is Andrew um the yes the


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universe was created in that instant uh


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of the big bang um and so you're right


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um you know in the conventional theory


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standard Einsteinian physics we we


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imagine that time and space didn't exist


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before the big bang so uh you've got to


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create some space for your gravitational


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waves to go through uh which is kind of


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thinking yeah and so um And so yes,


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there was the instant of the big bang


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that created this singularity in time


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and space followed by this period was it


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10us 33 of a second something like that


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in duration uh which we call the period


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of inflation when the when the expansion


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really took hold uh and it you know the


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universe went from the size of a


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football to the size of a galaxy in


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something like 10 theus 33 a second and


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uh the thinking is and I'm actually


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dragging this up from reading a few


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years ago but but that yes that per that


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inflationary period as we call it would


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have created gravitational waves.


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>> Uhhuh. Uh or maybe a gravitational wave


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but


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>> I was about to say


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>> maybe just one big one


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>> that's right


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>> at that point. But the the issue is um


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that uh it is a gravitational wave of


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very very very low frequency.


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So um the gravitational waves that we


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get from colliding neutron stars for


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example uh they produce waves which are


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basically have a frequency which is in


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the audio range which is why we can you


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know turn those uh gravitational wave


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signals into an audio signal very easily


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after you've amplified it up a bit and


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after LIGO has done its magic on it and


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that's where we get this chirp signal as


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as two neutron stars or whatever merge


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together uh and and eventually that


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because they're spinning ever ever ever


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more rapidly uh and so the frequency


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goes up of the waves that are being


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emitted and and then stop uh at a high


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point because that's where they've co


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coalesed into a single object. Um now


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you can think of those


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uh audio frequencies. Uh you know we


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might talk about something like 500 htz


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as an audio frequency or you could take


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440 htz as u the frequency of of um the


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standard a note in the in the musical


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spectrum. Um so if let's stick with 500


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because that's an easy one. Uh so the


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the the period of time between one peak


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of the of the wave and the next uh is


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1/500th of a second. And so if you think


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that's the inter interval of time of a


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characteristic gravitational wave from


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uh two colliding objects. Now the issue


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as I understand it is that the interval


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between peaks in a gravitational wave uh


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produced by inflation


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is about the same as the age of the


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universe now. It's not uh 1/500th of a


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second. It's you know several several


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billion years u perhaps even tens of


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billions of years. It's quite a while


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since I read up on this. So, so normal


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gravitational wave technology is simply


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not equipped to detect these low


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frequency


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ultra ultra low frequency gravitational


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waves, but there might be other ways of


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seeing them. Uh, and one of the things


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people have looked for, uh, and I'm not


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really very well up on this, but there


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is a potential


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signal in the cosmic microwave


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background radiation that the flash of


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the Big Bang that we see that that gives


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us what the universe looked like 380,000


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years after the Big Bang. That's that's


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what we're seeing there. that um that


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radiation uh contains information not


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just on its brightness but also on its


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polarization


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uh you know that radiation is polarized


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a bit like light can be polarized and


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I'm not really drawing the drawing the


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links very strongly here but I


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understand that there are links between


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very low frequency gravitational waves


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and that polarization signal so it's one


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of the things that people are looking


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for to try and detect this this


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polarization uh within the cosmic


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microwave background radiation. So it's


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not at all a dough question uh but it's


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quite a complex answer.


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>> Yeah. Yeah. But the the big bang itself


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could have initially been one you know


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created one gravitational wave.


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>> Yes. That's right. Yeah. That's more or


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less it.


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>> Yeah.


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>> There you go. Um you're right on the


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money. It's just a matter of finding a


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way of seeing them. Would they Is it


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possible these gravitational waves still


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bouncing around like the cosmic


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microwave background radiation?


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>> Well, yes. Yes. But um at such a low


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frequency that you don't actually know


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it's there. You've got to find other


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you've got to find other ways of


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detecting it because there's got not


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going to be any change in the


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gravitational wave signal over, you


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know, a human experimental lifetime. If


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you've got a frequency whose time


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interval is measured in billions of


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years, forget it.


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>> Yeah, that's a tough one.


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>> Forget it.


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>> Thanks, Boa. That's a great question and


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thanks for sending it in. Uh, we've got


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a question from one of our regulars,


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Renie, uh, who is from sunny West Hills,


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California. Uh, this is a what if


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question. And theoretically, if the sun


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were never to die, let's assume it's


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just never going to die, would the Earth


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eventually erode, decay,


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and die on its own?


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>> Um, yeah. Um, it's


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>> Well, my answer is no, because we'll


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destroy it first. It it could be very


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different. I mean what so if what Ren is


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saying is that yes the sun we know it's


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going to evolve over the next few


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billion years uh and it will change and


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that will eventually result in the earth


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being swamped by the outer atmosphere of


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the sun which might not be very nice for


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anybody left on earth. Uh but uh if that


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didn't happen, if the sun just um you


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know went on its merry way being a


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normal star,


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the there will be a few things that will


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happen over that time scale which


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wouldn't which wouldn't which we know


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won't happen because the sun's going the


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sun turning into a red giant's going to


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overtake it. One of them is uh the um


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tidal breaking of the earth's rotation


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so that it always uh faces the moon. So


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the earth's day will change from uh 24


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hours to something like if I remember


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rightly it's 42 days that it's it's


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about that length of time.


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>> Uh and that's it turning once and the


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moon will go around the sky around the


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earth in the same time. So the earth and


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the moon will constantly face one


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another with a a month and a day which


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are both equivalent to I think it's


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about 42 43 days something like that. Uh


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so that's that's going to change things


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quite a bit. Um so that would you know


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certainly alter the the um atmospheric


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dynamics of the earth if one side's


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getting warmed up for 40 of 20 days


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rather than just one day uh of day and


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night. So a lot of things change um and


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yeah the constant bombardment by the


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magnetic particles from the sun uh I


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don't know to what extent the earth's


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magnetic field might erode but there


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will certainly be be changes may even be


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>> what about go ahead go on sorry


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>> no I was just going to say if humans


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were still around in that period uh


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would we well okay no let me rephrase


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would we adapt as these things changed


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and reached that point, would we be able


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to adapt as a species and other life on


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Earth adapt to live in that kind of


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environment?


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>> Well, it certainly is these changes are


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ones that take place very slowly indeed.


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Uh and and over kind of longer periods


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than the characteristic evolution time


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to get from, you know, one mutation to


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another, whatever that might be for


00:11:57.519 --> 00:12:01.350
humans. Um, so yeah, they're they're


00:12:01.360 --> 00:12:04.310
slow and uh I'm sure humans could adapt


00:12:04.320 --> 00:12:06.790
to them. Uh, we're a pretty adaptive


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species. We might also by then be


00:12:08.560 --> 00:12:10.949
capable of building the mega structures


00:12:10.959 --> 00:12:12.710
that might protect us from some of the


00:12:12.720 --> 00:12:16.310
sun's funny things going on. Uh, it's


00:12:16.320 --> 00:12:18.550
hard to know really, isn't it? But but I


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I think generally speaking, I mean,


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Reny's question is a good one. Um, what


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happens if uh if nothing happens to the


00:12:24.240 --> 00:12:26.629
sun? Uh, does the earth just sort of


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survive? It probably survives. It will


00:12:29.519 --> 00:12:31.750
be changed. We might find we're all


00:12:31.760 --> 00:12:33.590
living in plastic domes or something by


00:12:33.600 --> 00:12:36.389
then rather than, you know, because the


00:12:36.399 --> 00:12:38.389
atmosphere has been so messed about


00:12:38.399 --> 00:12:41.190
with. But yes. Yes. I think I think I


00:12:41.200 --> 00:12:43.350
I'm I'm an optimist that humankind would


00:12:43.360 --> 00:12:44.790
survive.


00:12:44.800 --> 00:12:48.550
>> Yeah. Um now it's interesting because um


00:12:48.560 --> 00:12:50.069
I mean we we know what's going to


00:12:50.079 --> 00:12:51.430
happen. We kind of know when it's going


00:12:51.440 --> 00:12:54.150
to happen, but I if it didn't, it would


00:12:54.160 --> 00:12:56.710
create a whole array of new challenges


00:12:56.720 --> 00:12:59.269
for humanity because we would have to


00:12:59.279 --> 00:13:03.269
learn to live in a very


00:13:03.279 --> 00:13:05.110
somewhat hostile environment, I imagine,


00:13:05.120 --> 00:13:07.509
because um the the planet would not be


00:13:07.519 --> 00:13:09.829
the same. And I can't imagine what it


00:13:09.839 --> 00:13:12.470
would be like to have a 42 long


00:13:12.480 --> 00:13:14.949
>> 42 day long day.


00:13:14.959 --> 00:13:15.670
>> Um


00:13:15.680 --> 00:13:17.350
>> well, you know, birthdays would be few


00:13:17.360 --> 00:13:19.030
and far between, wouldn't they? uh they


00:13:19.040 --> 00:13:20.629
would, but you you know we're gonna


00:13:20.639 --> 00:13:22.069
we're going to know what that's like


00:13:22.079 --> 00:13:24.230
very soon because the the day on the


00:13:24.240 --> 00:13:27.750
moon is 20, you know, uh 29 days


00:13:27.760 --> 00:13:29.190
effectively from one


00:13:29.200 --> 00:13:31.670
>> full moon to another. So yeah, so we've


00:13:31.680 --> 00:13:33.910
we've we've already got something like


00:13:33.920 --> 00:13:36.150
that uh in store for people to


00:13:36.160 --> 00:13:37.829
experience. It'll be very interesting to


00:13:37.839 --> 00:13:40.629
see what even the Arteimus astronauts on


00:13:40.639 --> 00:13:43.430
the moon make of all that.


00:13:43.440 --> 00:13:45.509
>> Yeah. Yeah. Very interesting, Renie.


00:13:45.519 --> 00:13:46.710
That's a great question. Thanks for


00:13:46.720 --> 00:13:49.750
sending it in. Much appreciated. And


00:13:49.760 --> 00:13:53.590
next up, we've uh got Daniel. Uh this is


00:13:53.600 --> 00:13:55.110
um


00:13:55.120 --> 00:13:59.269
a sort of dark energy question. Sort of.


00:13:59.279 --> 00:14:01.350
Hey guys, Daniel from Adelaide here.


00:14:01.360 --> 00:14:02.629
There seems to be more and more


00:14:02.639 --> 00:14:04.310
discoveries lately in the very early


00:14:04.320 --> 00:14:05.750
universe that shouldn't be possible


00:14:05.760 --> 00:14:07.829
because not enough time has passed like


00:14:07.839 --> 00:14:10.069
size of galaxies or black holes. I've


00:14:10.079 --> 00:14:11.829
got a far out theory I'd love to share.


00:14:11.839 --> 00:14:14.310
What if time and dark energy were


00:14:14.320 --> 00:14:16.150
actually the same thing? So we know for


00:14:16.160 --> 00:14:17.750
about the second half of the universe


00:14:17.760 --> 00:14:19.590
that dark energy has been accelerating


00:14:19.600 --> 00:14:21.829
its expansion. Could this therefore mean


00:14:21.839 --> 00:14:23.430
that there was less dark energy in the


00:14:23.440 --> 00:14:25.590
first half? And if that's the case, what


00:14:25.600 --> 00:14:27.030
if time actually went slower in the


00:14:27.040 --> 00:14:29.110
early universe? So from our perspective,


00:14:29.120 --> 00:14:31.430
what took a really short amount of time


00:14:31.440 --> 00:14:33.269
actually happened in normal time with


00:14:33.279 --> 00:14:35.269
normal being in quotes. I'd previously


00:14:35.279 --> 00:14:36.870
asked a question on the show whether


00:14:36.880 --> 00:14:39.110
dark energy is related to black holes. I


00:14:39.120 --> 00:14:40.389
think there was a paper around the time


00:14:40.399 --> 00:14:42.389
that that kind of suggested that it was


00:14:42.399 --> 00:14:44.310
and we know that black holes do distort


00:14:44.320 --> 00:14:46.710
time. So, if time is part of the fabric


00:14:46.720 --> 00:14:48.629
of space,


00:14:48.639 --> 00:14:50.870
maybe dark energy is too, but it's


00:14:50.880 --> 00:14:52.389
actually one of the same thing. I'm


00:14:52.399 --> 00:14:55.189
expecting a very quick simple no, but I


00:14:55.199 --> 00:14:57.670
wanted to ask anyway.


00:14:57.680 --> 00:15:00.550
>> All right. Thanks, Daniel. Uh, yeah. Is


00:15:00.560 --> 00:15:03.030
um time and dark energy, are they the


00:15:03.040 --> 00:15:04.629
same thing?


00:15:04.639 --> 00:15:06.470
>> You never get a quick and simple no from


00:15:06.480 --> 00:15:09.750
me, Daniel. It's always a long drawn out


00:15:09.760 --> 00:15:11.990
complex no.


00:15:12.000 --> 00:15:15.110
not always but I think in this case yeah


00:15:15.120 --> 00:15:17.110
your your thinking is interesting uh


00:15:17.120 --> 00:15:19.030
we've we've talked recently as well


00:15:19.040 --> 00:15:24.389
about the um the fact that um


00:15:24.399 --> 00:15:26.389
this new controversial theory from Joe


00:15:26.399 --> 00:15:29.750
Silk at all uh over in Baltimore


00:15:29.760 --> 00:15:31.750
suggesting that perhaps black holes


00:15:31.760 --> 00:15:33.350
super massive black holes came first


00:15:33.360 --> 00:15:35.030
they were formed in the early universe


00:15:35.040 --> 00:15:37.430
and that goes a long way to explaining


00:15:37.440 --> 00:15:39.110
uh the conundrum that you mentioned at


00:15:39.120 --> 00:15:40.550
the start of your question there that a


00:15:40.560 --> 00:15:42.790
lot seems to have happened in the first


00:15:42.800 --> 00:15:46.150
uh in the first uh few millions or


00:15:46.160 --> 00:15:48.310
hundreds of millions of years of the


00:15:48.320 --> 00:15:52.230
universe's existence. Um so we we kind


00:15:52.240 --> 00:15:55.430
of understand the grav the gravitational


00:15:55.440 --> 00:15:58.470
time dilation uh effects pretty well and


00:15:58.480 --> 00:16:01.749
they're actually quite small uh from our


00:16:01.759 --> 00:16:05.670
vantage point here 38 13.8 billion years


00:16:05.680 --> 00:16:09.350
later. Um, and we and but you're right


00:16:09.360 --> 00:16:12.790
to make the point that uh dark energy uh


00:16:12.800 --> 00:16:15.749
only seems to have appeared over the


00:16:15.759 --> 00:16:17.350
second half of the age of the universe,


00:16:17.360 --> 00:16:21.829
but that's more likely to be uh it's


00:16:21.839 --> 00:16:24.069
because it its measurable effect has


00:16:24.079 --> 00:16:26.550
only become apparent. We think that


00:16:26.560 --> 00:16:28.949
during the first half of the universe's


00:16:28.959 --> 00:16:32.949
age, um there was the galaxies within


00:16:32.959 --> 00:16:34.550
the universe were close enough to each


00:16:34.560 --> 00:16:36.710
other that gravitational attraction


00:16:36.720 --> 00:16:39.829
would have basically kept the expansion


00:16:39.839 --> 00:16:41.590
due to dark energy in check, the


00:16:41.600 --> 00:16:44.069
accelerated expansion uh due to dark


00:16:44.079 --> 00:16:47.030
energy. Uh and so it's only when you get


00:16:47.040 --> 00:16:49.430
past a kind of tipping point where


00:16:49.440 --> 00:16:52.150
suddenly the the mass of galaxies in the


00:16:52.160 --> 00:16:54.629
universe is not enough not strong enough


00:16:54.639 --> 00:16:57.350
gravitationally to break the


00:16:57.360 --> 00:16:59.509
acceleration of the expansion. By that I


00:16:59.519 --> 00:17:03.670
mean B R A K rather than B R E A K. Uh


00:17:03.680 --> 00:17:05.909
it's not enough to slow it down. And so


00:17:05.919 --> 00:17:09.110
the acceleration takes over. Uh and


00:17:09.120 --> 00:17:11.909
that's why it's a tricky thing just to


00:17:11.919 --> 00:17:14.390
try and tease out and we've talked about


00:17:14.400 --> 00:17:17.669
this recently as well whether the dark


00:17:17.679 --> 00:17:19.350
energy is a constant whether it's


00:17:19.360 --> 00:17:22.789
something that's uh a factor that hasn't


00:17:22.799 --> 00:17:25.909
changed in terms of its uh its release


00:17:25.919 --> 00:17:29.430
as space as space expands. Um it's


00:17:29.440 --> 00:17:31.669
because there is this added impact of


00:17:31.679 --> 00:17:34.390
the gravitational pull of the galaxies


00:17:34.400 --> 00:17:37.190
uh stopping us from basically seeing the


00:17:37.200 --> 00:17:39.510
effect of dark energy the accelerated


00:17:39.520 --> 00:17:41.190
expansion of the universe back in the


00:17:41.200 --> 00:17:42.950
early universe. So I think all those


00:17:42.960 --> 00:17:45.430
things are are well and truly understood


00:17:45.440 --> 00:17:48.230
and kept fairly separate by the by the


00:17:48.240 --> 00:17:49.990
scientists looking at them. And by that


00:17:50.000 --> 00:17:52.230
I mean time and and dark energy. So


00:17:52.240 --> 00:17:55.350
that's a long complicated no.


00:17:55.360 --> 00:17:58.710
>> Yeah. Yeah. Um, okay. Daniel Winfred


00:17:58.720 --> 00:18:00.470
says, "I think these things have been


00:18:00.480 --> 00:18:02.230
long understood." That's that's his way


00:18:02.240 --> 00:18:05.909
of saying you're way off way way off the


00:18:05.919 --> 00:18:10.310
mark.


00:18:10.320 --> 00:18:12.390
>> But it's worth asking because otherwise,


00:18:12.400 --> 00:18:13.990
you know, obviously this is something


00:18:14.000 --> 00:18:15.669
people are thinking about. So, it's


00:18:15.679 --> 00:18:18.789
worth asking these um these


00:18:18.799 --> 00:18:21.750
>> different questions to um just, you


00:18:21.760 --> 00:18:24.630
know, see see if it's a possibility.


00:18:24.640 --> 00:18:26.390
>> Thanks, Daniel. Appreciate that.


00:18:26.400 --> 00:18:27.190
>> Great question.


00:18:27.200 --> 00:18:29.110
>> Uh, if you've got questions for us,


00:18:29.120 --> 00:18:30.710
please send them in because we could


00:18:30.720 --> 00:18:33.110
always use them. Uh, just, uh, go to our


00:18:33.120 --> 00:18:35.270
website, spacenutspodcast.com,


00:18:35.280 --> 00:18:36.789
spacenuts.io,


00:18:36.799 --> 00:18:38.710
and click on the various links. The AMA


00:18:38.720 --> 00:18:42.230
link will give you, uh, access to, uh,


00:18:42.240 --> 00:18:45.510
text and voice uh, audio. Or you can


00:18:45.520 --> 00:18:47.270
click on the little, it's not purple,


00:18:47.280 --> 00:18:48.630
it's green. When did they change the


00:18:48.640 --> 00:18:51.350
color of that? Uh, send us your Oh, no.


00:18:51.360 --> 00:18:52.870
It's It's purple when you hover on it.


00:18:52.880 --> 00:18:55.669
There you go. Uh send us your questions


00:18:55.679 --> 00:18:56.950
uh on the right hand side of our


00:18:56.960 --> 00:18:59.029
homepage and uh don't forget to tell us


00:18:59.039 --> 00:19:01.110
who you are and where you're from. Fred,


00:19:01.120 --> 00:19:02.789
we're done again. Thank you so much.


00:19:02.799 --> 00:19:05.029
>> Uh always a pleasure, Andrew. And I hope


00:19:05.039 --> 00:19:07.669
we'll stick it again very very soon.


00:19:07.679 --> 00:19:10.150
It's a distinct possibility. Could be


00:19:10.160 --> 00:19:13.110
with could be within 13.8 billion years


00:19:13.120 --> 00:19:14.070
in fact.


00:19:14.080 --> 00:19:16.789
>> Yes. Thanks uh Fred. See you soon. Fred


00:19:16.799 --> 00:19:19.029
Watson, astronomer at large. And uh


00:19:19.039 --> 00:19:20.710
thanks to Hugh in the studio for making


00:19:20.720 --> 00:19:22.150
our lives so much more difficult with


00:19:22.160 --> 00:19:25.270
these split episodes. But no, it's okay.


00:19:25.280 --> 00:19:27.110
Uh and from me, Andrew Dunley, thank you


00:19:27.120 --> 00:19:28.630
so much for joining us. Uh looking


00:19:28.640 --> 00:19:29.909
forward to your company on the next


00:19:29.919 --> 00:19:33.190
episode of Space Nuts. See you then.


00:19:33.200 --> 00:19:34.150
>> Space Nuts.


00:19:34.160 --> 00:19:36.310
>> You'll be listening to the Space Nuts


00:19:36.320 --> 00:19:38.549
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00:19:38.559 --> 00:19:41.510
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00:19:44.160 --> 00:19:46.549
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