Cosmic Questions, Gravitational Waves & the Mysteries of Space-Time

You are listening to another wonderful episode of Space Nuts and I am your host for today, Heidi Compo. Well, our beloved Andrew Dunkley is out on holiday. Don't worry, he will be back soon. But the brains and brawn of the show, you're beloved, Fred Watson, is here with us today. Fred. Hello, Hello, you ready? Hid you ready to answer some questions on our Q and A episode today? Yeah? Look, Q and A is the real meat of Space Nuts because we love people telling us what they want to hear about. It's far better than me spouting on things that they don't want to hear about. So yeah, sound ready to go? All right, and we get just such a wonderful, diverse range of questions from our listeners. Starting you know today we have Thomas dear Professor Fred Watson. My name is Thomas Wood. I mean, you're eleven student doing my research project on the question. And the question that I have is what is the chance of a habitable planet being found? Here's the key word within our lifetime? So what do you think, Fred, within our lifetime? Yeah? I think? I mean we're talking here about planets of other stars, exoplanets, It doesn't really matter whether they're habitable or not. Because they're so far away, we're never going to manage to get to them within what you might call a human timescale. But there are certainly candidates already for habitable planets among the five or six thousand exoplanets that we know of today, and there are more being discovered all the time. There are planets that sit within the habitable zone of their parents' star and may have atmospheres that could sustain life. Those have not yet been confirmed, they've not been definitively confirmed, but I do think they will be within our life time, and probably Thomas, as Year eleven students, your lifetime is rather longer than mine is, but that's all right. I can deal with that. I think we'll find them within my lifetime. There you go. That's putting the that's putting the odds on it. Well, Fred, I think you have certainly done a lot with your lifetime so far, and you have really broken broken the ground for so many more to follow. Our next question is an audio question. This is Adriana from Florence, Italy. Hi, Federalreo. This is Adriano from Florence in Italy. I was listening to a conversation about LIGO so the LASI interferometer, where they explained that by measuring the gravitational waves from too colliding the Coursa, for example, they can also estimate the master of the two objects. Can you please explain how they can do that? And they also mentioned that with a much or czable instrumental we should be able to measure the gravitational waves from the big banger. Is this is a correct and if so, will we be able to estimate the master of the entire universe and therefore to confirm more than I the particis around the dark energy and dark matter. Thank you guys for your inspiring podcast Whitby. These are fantastic questions from Adriana really, you know, on the edge of our knowledge really, and it's a good question. How so Ligo, as you said, the Laser into from Gravitational Wave Observatory is one of several gravitational wave observatories. Now, LIGO was the first to actually detect gravitational waves back in twenty fifteen, and what we saw was so gravitational waves are formed by vibrations in space and waves move through space, which you know, they're basically propagated by the vibrations. The waves are propagated by the vibrations of space because space is flexible. It's one hundred billion billion times more rigid than steel, but it's still flexible. So what we have is this phenomenon where we can actually measure those vibrations directly. And it turns out that ligo is sensitive to gravitational waves with the same sort of frequency as the audio waves that we hear through our ears. So audio waves are frequencies of a few hundred killer hers, and the gravitational waves that ligo is sensitive to are the same. And when you look at the traces of these waves, you can see them in great detail and measure the way they change as two black holes or neutron stars combined together. Because there's a characteristic signal, it's called the chirp. I'll do one for you, Heidi, because I haven't chirped to you before. If you listen to the audio, it sounds like and the chirp at the end is when the gravitational waves, sorry, the black holes, actually emerge. They come together, and it's the way that signal changes over those few tens of seconds at the end of their lives that let you model exactly what it is that is coming together. You can model the objects that are colliding by analyzing that waveform in detail. So that's how it's done. You don't look as though you believe me. I just think Adriana's question was a little bit over my IQ or at least my knowledge. But this sounds very fantastic, and I'm very excited for all the people who understood explanation. Let's go to just finish off his other question though, because that's really interesting. He says, with a bigger interferometer, could you detect the Big Bang? And the answer is basically no, you need something quite different. So, as I said, the ligo, and it's ilk sensitive to gravitational waves with killer hurts frequencies, so a few hundred cycles per second as we used to call it. Did I say killer hurts? Yes, I meant the wrong. Yeah, well I'm talking. Yeah, killer hurts are a bit high. It's hundreds of hurts rather than killer hurts. So you know, five hundred and six hundred hrs. Killer hurts is a thousand obviously, so just replay that bit. Anyway, The bottom line is to look for phenomena in the early universe, and it's not so much the Big Bang itself as the inflationary period that followed it, when the universe expanded by ten to the power fifty and ten to the minus thirty three of a second, which is just beggars the imagination. But to pick up phenomena like that, you need to be sensitive to gravitational waves with nanohertz frequencies. That means, how can I put it? A billionth of a billionth of a cycle per second? In other words, they make one cycle over a very long period of time years, decades, maybe even millions of years with some of them, so you never see the vibrations. You just see part of one cycle because it's so slow. The period of these vibrations is so slow, and so you need different technologies to do that, and people are working on those. And indeed we've spoken about on space Nuts in the past. People just like people just like you, I'd say, people like you and me, but probably a little bit more people like you. Let's take a short break from space Nuts to tell you about our sponsor, nord vp N. Now. I've talked about virtual private networks before and how they can protect you online, and no one does it better than Nord Now. I've been using Nord for over two years and I have no complaints. I'm also using some of their other tools, including the brilliant password manager and the one terabyte of cloud storage. And let's face it, you just can't get enough storage these days. And cloud storage is good because it's backed up. If you've got it on a drive attached to your computer, that drive will eventually die and you don't want to lose all that stuff. So yeah, cloud storage is the way to go right now. Space Nuts listeners get an exclusive deals extra for free when you sign up for a two year plan, and that's a saving of seventy four percent, plus it comes with their thirty day money back guarantee. All you have to do is head over to NordVPN slash space Nuts and click on get NordVPN. You'll see all the current deals and options, including their VPN service, malware protection, ad blocker, track a blocker, they're awesome, password manager, and even a data breach scanner. Seriously, have a look at it. NordVPN dot com slash space Nuts. Nord vpn dot com slash space Nuts. All right, let's get back to the show. Space Nuts. Our next question is actually from your side of the world, and it's from Anthony. Anthony love the show, of course. My question is, even though the Moon's orbit is tilted relative to the Earth only by or sorry, by only seven degrees, why does it appear to shift so much in the sky tonight? For example, it is really low in the north from my location in Sydney, but at other times, sometimes not too far apart, it is almost overhead. It must be simple geometry, but the differences seem far too great to be seven or fourteen degrees. It seems like much more than forty five degrees, certainly more than the first three lengths. Think. Thanks. That's from Anthony from Sydney, Australia. Yeah, it's probably not very far from where I'm sitting now, Hello Anthony. So seven to fourteen degrees away from you? Yes, so, actually it's five degrees, not seven degrees. The tilt of the Moon's orbit is five degrees. But the main point is that that five degrees is with respect to the ecliptic, which is the plane of the sorbit in space. So and in the sky, the ecliptic is the path of the Sun through the sky. So five degree tilt to the ecliptic means that effectively the moon follows the Sun's path through the sky with a bit of five degrees either side of it, so that, as Anthony says, that's not very much. But the bottom line is, of course the Sun's path through the sky is tilted at twenty three and a half degrees with respect to the equator, and that's why we see such large variations. So if you think about what the Sun does in a year, the moon does more or less the same thing in a month, because it goes around the ecliptic five degrees one side or the other of it, but more or less going around the ecliptic in one month, which is why, over very short periods of time you see the moon in very very different places in the sky. One little characteristic, and this might illuminate one of the comments that Anthony made is that when you're near the solstices, either the summer solstice, which for us in Australia is in December the sun is at its highest in the sky, or the winter solstice, which for us in Australia is June, then the moon in its path through the sky and Basically, when it's full, a full moon is exactly opposite where the sun is. So when the sun's very high in the sky, a full moon is very low in the sky, it's right opposite it, within five degrees either side. So I always think of that when I look at a full moon, I imagine it's where the sun will be in six months time, at the different time of year, which is kind of quite cute, really in a peculiar sort of way. So yes, it's a good observation. But the reason for it is, as you said, it's geometry. I never thought that that's a quite a cool little tinbit. I'm just I'm thinking back. This is a little bit of a side story. But I got married. I insisted. I told my husband I wanted to do an astronomy kind of themed wedding, and so we got married under We chose the October full moon, the Hunter's moon, and we got married, and then we immediately the next day we were driving across the country because I was from Utah. He was in Florida at the time, so we started our road trip to Florida the day after we got married. And I just remember, because we did our full moon wedding, and I got married right at the time that the moon was supposed to be at his fullest. I'm a little bit of a weirdo. But then the next day the moon was so low in the sky and bright red. I just remember it was the most brilliant looking thing I've ever seen, and so just really kind of thinking about Anthony's question with you know, when we got married, it was up in the sky, and then the very next day it's right down low on the horizon like a movie. It was like like like almost like a Lawrence of Arabia type kind of look. Was very cool. HARDI I'm going to pick up on that today because I can't resist this. Marny and I too had an astronomical wedding. We got married, and this is why I'm picking up on this six years ago today. It's actually today is our anniversary. Oh, happy anniversary, Thank. You very much. Yeah, we've been together for nearly twenty years, but it took us quite a while to get married. Six years ago today. We got married on the summit of Haliakala on Maui, which has a number of large significant telescopes on it, including pan stars to the asteroid Guardian Telescope and the Daniel K. Nui Solar Telescope is the biggest solar telescope in the world. They were right behind us when we got married at ten thousand feet on the summit of and I got wonderfully sunburned on the top. Of Oh, that's such a beautiful story. Well, congrats to you, and congrats to congrats to you yours and that's a that's such a beautiful story. I guess we're dedicating this episode to our our significant others and the. On the moon. That's right. Yeah, sorry, sorry to hijack that comes. Oh no, that was a. That was well, that was fun. You know, maybe maybe people are curious about your you know, your personal personal experiences with space because I think, you know, sometimes it's nice to add and infuse a little bit of the personal love for space too. Okay, t. Space nuts. Our next question is an audio question, and this is Mikey from Illinoi's USA. Hey friend Andrew, this is Mikey once again from Illinois and the US of A. I'm just wondering if you guys have any room in your house for me and my family. I'm just kidding, let's just serious. I'm just joking, unless you want me to. I'm just kidding. Keep it in mind. So I know that space can bend, space can warp, space can ripple space, can it supposedly tear? I was curious as to what it means for space to actually tear, like have we seen examples in real life of space tearing and what would that look like? Or is it just we know it can but we haven't seen it. Yeah, I was just hoping you guys could explain that a little bit more. I appreciate you guys love the show. What an interesting question, and it is hypothetical, the idea of space tearing, because we've never ever seen anything symptomatic of tearing space, either here on our planet or in the wider universe, and it would have to be under very very extreme circumstances that it would happen. So by extreme, I mean space being stretched beyond its limits. And the reason why this is a popular notion is because of the discovery back in back in nineteen ninety eight that space is accelerating in its expansion. We've known since nineteen twenty nine that the universe is expanding that's taking space with it. But since nineteen ninety eight, we've known that that expansion has been ever faster, ever more rapid. It's accelerating, and so that's given rise to the idea of if this goes on into the far distant future, are we going to get to a situation where space is so stretched that it falls apart? And that gives rise to the notion of the big Rip. And actually, the best place I can direct mikey to on the web, because it's explained very I won't say concisely, it's exploring great detail, but it's easy to read is the Big Rip entry on Wikipedia. I'm a big fan of Wikipedia, and the Big Rip entry is really quite extraordinary because it talks about the hypothesis that space could tear. It talks a little bit about the work that's been done on this, the research that has been carried out in a serious, you know, academic manner as to what might constitute space being ripped apart, and you can sort of define that in terms of the various fundamental forces of nature. And there is a hypothesis that then suggests that what might be the trigger for a big rip in terms of, you know, the tension that is involved, and that One of the authors of that hypothesis is Robert Caldwell of Dartmouth College, who presents us with a formula which defines when the big rip will take. It's quite a neat formula. It includes things like the Hubble constant and the baryonic mass content of the universe. It's all there on the page. And I think the bottom line is is it twenty billion years if something like that? Oh no, wait a minute, The earliest is one hundred and fifty two billion years time. That's when space. Yeah, one hundred and fifty two billion years. Put it in your diary, miikey, because that's when you will find the first example of space being with. Oh my, well, our very last question is from my side of the world again. So we got Greg from Minnesota. So he says, hello from Minnesota, USA. I'm Greg, and I have a question about the cosmic jerk. And no, I don't mean Fred, oh Fred. And his question is the change of position over time is velocity, and the change of velocity over time is acceleration. But we don't need to stop there. The change of acceleration over time is called jerk. We know the universe is accelerating, but have we been able to measure whether or not it's accelerating at a constant rate? Love the podcast, Keep up the good work if you're curious. The next derivatives after jerk are snap, crackle. And pop. Yeah. So, I'll refrain from using the term jerk since it's been applied to me and to give it its proper name, which is the rate of change of acceleration. So acceleration is the rate of change of velocity. Velocity is the rate of change of position. As exactly as Greg says, I was. Thinking this question was going to be for me for a second. I was like, wait a second, that's what I do my research in. Yes, so yeah, so so. But Greg's question is is very very topical at the moment, because yes, we've known that the universe is accelerating, as I said a few minutes ago, since nineteen ninety eight discovery made by an Australian and a US scientist in working independently. That discovery immediately led to the question is the acceleration changing? In other words, is there a rate of change of acceleration? And that's a very hard observation to make. You need to look at the universe over the widest possible range of look back times. So you want to look back eleven billion years if you can, you know, sort of seven eighths of the age of the universe. And so what's happened recently is something called DESI, which is the Dark Energy Survey Instrument, and dark energy is, by the way, the mechanism which we think is causing the universe to expand, that space has an energy of its own. Until now, we've believed that was a constant, that their acceleration of the universe was a constant. But DESI, the Dark Energy Survey Instrument on a telescope in Arizona, based on the Male telescope before me to the telescope at kick Peak, that seems to be indicating and it's still not speculative. It's still one of these results that's still got a question mark over it, but it seems to indicate that the acceleration is slowing down, and slowing down the acceleration is a good thing because it might put off the big rip beyond one hundred and fifty two billion years, might push it back into the more distant horizon. So we will It remains to be seen, but I think the odds are that over the next few years will find compelling evidence that the acceleration of the universe's expansion is slowing down. And that's a mystery because that needs a mechanism, and it probably suggests there are new physics that we do not understand that have yet to be determined, and it opens up all kinds of areas of research, which seems like a really good way to wrap up this Q and a session of space nuts. Absolutely, and I'll tie that in with love, another one of life's greatest mysteries. Since we're talking about our loved ones. If there is somebody that you love and you would love to share this podcast with, we would be just tickled if you could tell everybody that you love, and maybe some people that you don't even really care for but you sit next to them at the office. Tell your friends, tell your family, tell the people you don't like, tell your dog, tell your cat about space nuts. We are here for you. We've got our question and answer episodes and our more I guess what do we call this more narrative story style episodes every week and so, Fred, do you have anything else you want to add before we sign off. For the day. I think we've covered some much of the big mysteries today that we should just go away with our heads spinning and try and think of some more questions for next time. Excellent. Well, hey Fred, thank you so much. This has been another episode of Space Nuts. Space Nuts. You'll be listening to the Space Nuts podcast. Available at Apple Podcasts, Spotify, iHeartRadio, or your favorite podcast player. You can also stream on demand at bytes dot com. This has been another quality podcast production from nights dot com.