The Supermassive Podcast - 56: BONUS - What distorts time?

Episode Date: September 26, 2024

What happens when a black hole and gravitational wave collide? How will the moon's gravity impact tides with rising sea levels? And "the Supermassive Wise Ones" discuss Einstein vs Newton in this bonus episode.  Send your questions to [e-mail]. 

Hello and welcome to another bonus episode of the Supermassive podcast from the Royal Astronomical Society with me, science journalist Izzy Clark and astrophysicist Dr Becky Smither. This is the place where we dive into the Supermassive mailbox, which admittedly is accreting at quite a quick rate right now with all of the questions that are coming in from you all we still absolutely love your questions you ask the best questions that we we don't even think to put in the show so thank you so much for all of you that have got in touch we will cover as many as yes um and you know you can email us or you can slide into the dms on instagram we read them all so check you out talking like the kids yes that's me i'm hip and cool. So, Robert, before we get on to the questions, I think you'll be pleased with this email that we've had from Jamie Collins. And he says, hello, fellow space nerds.

Robert promoted his book on a recent podcast and he said he's not even sure if it's in print anymore. I ordered it and can confirm it is. I look forward to reading it over the next next few weeks and he sent a picture of it well jamie jamie i i'm flattered and thank you and thank you for confirming it's still available there you go to anybody who's listening you can still get a book oh in uh well it was 2019 so it's the 50th anniversary of the new landings so no it's great i mean if it's still out there then obviously i'm going to recommend it and yes, please go ahead and tell me what you think, Jamie.

Okay. What is it called, Robert? Plug it properly. I have to do that, don't I? Moon Art Science Culture by me and Alexandra Loska, who's an art historian, and she was actually the inspiration behind it and drove it forward. So credit is here, really.

Yes. And thank you, Jamie, for letting Robert know that his book is still out. My own book is out there still. Okay. Somewhere in the void. Exactly, I think so. Your book is there. Okay, so on to the questions.

Becky, Mike Potter has a question about Einstein's work. He says, Greetings to the Supermassive team. I recently finished reading Proving Einstein Right by S. James Gates Jr. and Cathy Pelletier, which details many of the adventures of the total solar eclipse hunters of the late 1800s and early 1900s. Oh, that sounds good. OK. One thing that puzzled me was a statement that the deflection of the starlight as it passed by the sun, expected using Einstein's theory, was twice that expected using only Newton.

They had the idea that light was composed of massless particles, so how would the sun change the path of starlight without the bending of space-time? I don't understand why they expected any displacement under Newton. Help me understand, supermassive wise ones. By the way, proving Einstein right

would be great to add to the book club. Yeah, consider it done. Also, I'm putting supermassive wise ones uh by the way proving Einstein right would be great to add to the book club yeah consider it done like also I'm putting supermassive wise one on my CV yeah exactly that's all we'll only refer to ourselves as from now on thank you that's from Mike in Oregon oh nice I've just been out your way of the world Mike um anyway essentially it's what you said in your email Mike they actually weren't assuming the particles of light were massless. Like Newton, for example, when he came up with his theory of gravity, definitely did not know the speed of light at that point. It was like faster than they could measure at that time. And he also didn't know like what light was and whether it was a massless particle or not. So you can still apply Newton's theory to this if you assume that light has mass,

but you also don't need to know what the mass is to do it. If you've ever sort of worked through sort of like, I guess it's like a level, you know, high school, 17, 18, sort of like physics, 17, 18 year old. And you can sort of put the equations together to work out what the acceleration due to the sun's gravity would be and cancel out the mass of the thing that's being accelerated. And so as long as you know that acceleration, you know what the angle of deflection would be. And that's what they're talking about here

when they say that there's gonna be a deflection of starlight, what angle of a deflection is there going to be, which then produces this angle of offset on the sort of curved sky that we see. And so in Einstein's theory of general relativity of gravity you can also get at that angle offset as well and so what they measured during the eclipses was this angle of offset of what the star where the stars appeared to be during the eclipse

versus six months earlier or six months later when the sun wasn't in that part of the sky and to say okay that means the light has been accelerated by this amount and therefore bent by this amount in iso theory of general relativity it's due to the curvature of space in newton's theory it's just because mass is there i can't even never really explain what gravity was right he was just like this is the equation that just describes what gravity does right and so it is really interesting to think that you can get an expectation of what it should be using Newton's theory. And again, this is just one of the things that proved Einstein right, as the book was called, along with Mercury's orbit as well.

So it's also worth mentioning that the RAS, one of the biggest things we did, I suspect, ever in science was to fund an expedition along with the Royal Society off to Principe, off the coast of Africa, and Sabar in Brazil to do this test in the 1919 solar eclipse. And that got loads of newspaper coverage and it made Einstein the kind of science rock star. That's what did it, you know, because his, and then there are amazing headlines about heavens all asunder and all this stuff that, you know, quite incredible. It's, yeah, the heavens askew. No one needs worry or something that's right the headline as well i think um along with your you know very rich history at the royal astronomical society you should also have a plaque that says we made einstein a science i think we will thank you

we made einstein famous yeah yeah it's pretty great okay and robert carl down has sent us an email he says hi team long time listener first time emailer i've always been interested in the mind-boggling subject of time i'm vaguely aware of certain things that can disrupt or warp time you know mass and speed but would be really interested to hear what are the causes of distortion of time and what repercussions does it have also i watched a thing just now saying that time was slower in the early universe than it is now is that true and if so how does that affect observations and calculations regarding the history of the universe i apologize for any headaches caused by these questions tar well carl that's going to get the

good and deep question description as well, I think. Personally, I find time slows down. My perception of it definitely slows down in certain settings and perhaps the headache I'll get will last longer too. But more seriously. I had a friend who did their PhD at the same time as me at college and they had a title. They were in the psychology department. It was sort of like a cross-discipline thing. And the title of the PhD was, does time really fly when you're having fun? Almost like amazing to think that you could even sort of try

and apply special relativity to that. But I mean, more seriously, this is where Einstein's theories really help us out. So special relativity describes how time slows down at speeds close to the speed of light. And that science fiction consequence, or one that's written about a lot, is the twin paradox. So if you go off and explore the universe at high speed, and then you come back to the Earth,

a few years might have passed for you, and everybody on Earth you knew is long dead. It's a classic motif of science fiction. And then general relativity includes gravity in that, as Becky was describing, and predicts how time, nearer mass slows down. And that even includes the Earth. So it means that clocks in orbit on satellites run faster than on the ground. And if we didn't take it into account, then GPS and car satnavs would not work. I think they're out by areas of hundreds of meters a day just due to that tiny, tiny difference. So if everybody ever asks you why astronomy matters, then well, your satnav wouldn't work for a start. But as for...

Have you heard the story of when they first actually tested that with, like, two planes in the opposite direction? I knew they'd done it with planes with atomic clocks. They did it with atomic clocks. Yeah, atomic clocks on, like, two just commercial planes. And they had to buy a seat for the atomic clock. Imagine if you were sitting next to that. Hello, Mr. Clock, would you like a drink? Yeah, but, you know, as for a time in the early universe running more safely, that was intriguing.

I hadn't come across that. Of course, it makes perfect sense. And it was confirmed by observing quasars. And these are very active galaxies with big black holes in the center, you know, consuming a lot of matter, devouring it. And they go, you know, they were looking at them as far back as a billion years after the Big Bang. And yes, they observed that change in the, you know, the time running more slowly. And it confirms again, that general relativity works, that that denser universe with more of an influence on gravity as a whole, was slowing down time as expected. And I think the answer to the question is the consequences. Well, it's consistent with

Einstein's theories and with our understanding of how the universe has evolved since then. So, yeah, it's great stuff. It's intriguing stuff. It may or may not cause me a headache later on. We'll find out. And I will update you on whether time slows down as a result for me personally. In line with that thesis. The other bit of the thesis.

Yeah. I remember reading that, you know, big gravitational wave background result that was last year. Was it last year? Yeah. Yeah. The one that was like, you know, big gravitational wave background result that was last year. Was it last year? Yeah. Yeah. The one that was like, you know, using like pulsar timing arrays to find like, you know, gravitational waves from what they presume are merging supermassive black holes out there

in the universe. You have to take that into account. The fact that like, you know, the early universe was running more slowly back then. Otherwise, there's so many things you have to take into account for that, like the movement of Earth and the fact that Jupiter pulls on Earth and the sun and all sorts to get the locations right but you also have to think about time too so there's many places it comes in i hope that answered your question car because i was reading it being like this what do you mean by disrupt and what do you mean by distortion of time like to me they're the same thing so i hope we i hope we answered you and

let us know if we have it and we'll come back to it. Yeah, let us know if we haven't. I could dig myself into a deeper hole if I had to answer it. Yeah. Which is always good for listeners. Well, on a similar vein, Becky, as our queen of black holes, can you help with this question from Arta, who says, Hi, I love the podcast. I hope you can answer this.

How do we expect a gravitational wave to behave when meeting a black hole? Will it just sink in or swirl in like all matter, or is there a chance that it will go through it and if so could we hope to improve our technology so much so to x-ray a black hole regards arthur arthur you've hit on a really interesting point here and it's one that people have been thinking about for a long time essentially what you're asking is like do black holes like interfere with gravitational waves so if you heard of this idea of like interference of waves is you know like if you drop like two stones in a pond at once right and the ripples come out yeah and you see the ripples and they collide and you get like a double height almost and all they can cancel each other out so people were thinking about this in terms of like okay if you've got

two black holes haven't quite merged yet but they're just orbiting each other right that's a huge change in the sort of warp of space-time as they go around each other and they do send out these ripples of gravitational waves which is what we've detected we were just talking about with the pulsar timing arrays and so people were saying okay they're going to ripple out they're going to interfere with each other or are they going to interfere with each other first question and then also what happens as they go through the other black hole now the key thing here is that like the black hole is causing like a warp in space-time itself and also causing the gravitational waves and the gravitational waves and the gravity from the black hole is just according to Einstein's theory of general relativity curvature of space-time so technically what people have found from doing

simulations at least of what happens and then also testing it based on LIGO and Virgo observations which are at least getting there from some of the gravitational wave detections we've made but not quite the detail we'd want just yet to test our sort of simulations and models is that the gravitational wave just passes straight through the black hole like it just carries on it interferes like with it so it sort of like adds together in terms of the curvature right okay and it's quite weird and so we're hoping yes i'm like okay well yeah i'm just listening i'm just listening we're hoping that you heard about this new gravitational wave detector that's coming, like, next decade, that LISA, right?

It's this huge, like, triangle of lasers in space that orbits the sun, like, behind Earth. It sounds like the most ridiculous thing. Like, a triangle of lasers in space that's, like, got to cover this massive distance yeah fine cool totally of course yeah like whoever's job it is to currently write like the justifications for that for like funding must be incredible i mean talk about blue sky thinking or dark space thinking i don't know but anyway it's had the go-ahead you know from from i can't remember if it's nasa or

east alisa i think it might be both of them um and it's got the go-ahead so you know it's getting funding it's it's being developed as we speak and we're hoping with that we'll be able to have the level of detail to test the models of like how this sort of interference of the gravitational wave passing through the black hole actually happens and like arthur says like can we actually learn something about what's going on beyond the event horizon in terms of like the curvature of space and the gravity? I mean, it's very cool, isn't it? Yeah, like this hurts my head. So, yeah.

And Robert, Sara Torres has a question about the moon's gravity. How will lunar gravity affect the tide if the worst happens? How will lunar gravity affect the tide if the worst happens and due to climate change, the sea levels rise above 70 metres, say if the ice caps or glaciers completely melt? Yeah, Sarah, I looked around to look at the different scales here and about 97% of water on Earth is already in the oceans and a little bit of that in inland seas. And only about 2% is in glaciers. So even if it all melts, and that has a pretty terrible impact on very many coastal cities, you know, it's pretty disastrous if the levels are at where you don't know what you have to do in terms of, yeah, loads of areas of the earth, you know, are going to have real problems if that happens. However, it's not a huge change in the volume or the mass of water overall. You know, it's 2% compared to 97%.

So it's much, I think, like the small change in the atmosphere from increasing CO2 levels. It has a huge effect on us and the temperature of the Earth, but it's not a large change in the amount of CO2 in the atmosphere overall. You know, the air is still overwhelming in nitrogen and oxygen. So the Moon pulling on that slightly larger body of water is not massively different. And there are a few exceptions to that. And reading around, there's concerns that in, say, some Arctic settlements where they have smaller tides in winter because the sea ice locally is locked up more in the water, if that goes, then those places might have to cope with bigger tides and manage that. So I hope that answers your question. The lunar gravity will remain the same, essentially. The moon's getting very, very slowly further away

from the Earth. But, you know, on human lifetime, we don't see any significant change as a result. But there will be local effects that are problematic. And of course, you know, we don't want all the ice caps and glaciers to melt because it's really, really bad for billions of people are going to be affected badly by this you know so yeah physics aside this is something we really want to avoid totally well on that note that's it for this we'll be back in a few weeks with an episode on strange stars i feel that has to come with that music like strange stuff i know i need to insert some like weird effects and of course if you have any questions about strange stars that you've heard of in the past you can contact us it's at supermassivepod on

Instagram if you want to slide in the DMs as Sissy says or podcast I need to stop saying that don't I yeah yeah I mean I wasn't gonna do it or you can you know old-fashioned email podcast.ras.ac.uk contribute to that accretion of the supermassive mailbox, and we'll try and cover them in a future episode. But until next time, everybody, happy stargazing.