Cosmic Conundrums: Time Dilation, Dark Matter & the Quest for Faster-Than-Light Travel

Um, our first question today is Martins from Latvia. And here is his question.

in space at the speed of light. After some time it comes back and the object that's on Earth is older than the other object. So why is that happening again? Why? They aren't the same, uh, age. I mean. Yeah, there's something to do probably when you're reaching speed of light that time is slowing down or something. But why it's slowing down? Why isn't it, uh, like. Yeah, just curious. And uh. Yeah, and I have, um, some dad joke for your, uh, arsenal, Andrew. So, uh, how do you

put a space baby to sleep? You rock it. So anyways, guys, cheers then. Yeah, have a good one.

through, uh. Because we always visit these places in winter, uh, through snow and woodlands. And it trundled along at something like nine miles an hour. Maybe it was a fast walking pace because it was a very old line, but it was a lot of fun. Anyway, enough about Latvia. Uh, let's get to the speed of light, which is basically what Martin's question is about. Um, this is, it's one of the fundamental aspects of relativity. Uh, Einstein's two theories

of relativity. One was about motion. The other was about gravity. It's the one about motion that covers this. That's called the special theory of relativity. Uh, dated 1905. And it turns out that the thinking that Einstein had had, uh, leading up to this. Was that we know that the speed of light is a bizarre quantity. Because in a vacuum it's always the same. We know also that it's the maximum speed that anything can attain. In fact, you can't actually achieve

the speed of light with an object. Because you would have to put infinite energy in to get it to the speed of light. And we don't have infin infinite energy. So light and its other electromagnetic waves. They are the only things that can travel at the speed of light. But if you had something that you are accelerating. Well, let me just go back. The speed of light is almost like a magic number. It's not magic because it's a very round number. It's about 300,000 kilometers per second.

Uh uh, it is, however, the fact that it doesn't change in a vacuum. And it doesn't matter how fast the source is moving. You'd expect if you have a source that's moving. That sends out a beam of light. Um, the source's speed would add to the speed of light. And the speed of light would increase. But it doesn't doesn't work like that. And once you establish that, then it turns out. And there's some quite sort of simple ways of seeing how this might work. Which we don't really have time

to talk about. But some of the books about special relativity. That talk about people looking at somebody moving on a train. Show you how the geometry works. That, uh. Because the speed of light is always the same. Then what it tells you is perceptions of time and distance must change. And so the key thing here. And the point that, uh, Martins is raising. Is that if you've got an observer who is stationary. Compared with somebody who's moving at a very high

speed. Nearly, uh, the speed of light or yeah. It doesn't matter whether it's near the speed of light or not. The effect works. But it's when you get nearer the speed of light. That it becomes noticeable. Um, the time that you observe. Um, that moving person, uh, experiencing is slower. So your time's ticking away as normal. And the person who's moving past you. Their time is ticking away as normal. But when the stationary person if you could see the clock

on the moving vehicle or whatever it is. Train Going at nearly the speed of light. Just to mix a few metaphors there, um, what you would see is their clocks would seem to be going much more slowly than yours is. And that's the time dilation effect. And yes, it means that, um, if you can then bring these two back together, the moving person has experienced less time relative to you than you have. And that's the. It's sometimes called the twins paradox.

Because if you take two twins, one goes off at the speed of light, comes back again, or nearly the speed of light, comes back again there they have aged much less than the twin who stayed put. So that's the bottom line. And it's such a counterintuitive concept that it is really hard to get your head around. But we know it works. Uh, in fact, um, the demonstration, um, the practical demonstration of this phenomenon happening in reality, uh, I think it was just

before the Second World War. Might have been round about the same time. But there are things called cosmic rays which are bombarding the Earth all the time. These are subatomic particles that come from space. Um, and they are predominantly a species of subatomic particle called a muon. So these muons were observed coming down through space at, uh, nearly the speed of light. And we know how long they take to

decay in the laboratory. But their decay time was much longer when they were observed coming in at the speed of light, nearly the speed of light, the time had dilated. So the decays were much longer than what we observe in the laboratory when they're not stationary, but they're going much more slowly. So it is a proven fact this works. Uh, if we could build a spacecraft that would get us to. I can't remember what it is. I think it's 99.99998% of the speed of light. Head off for 500

light years, come back again. Uh, you will be 10 years older, whereas everybody else on Earth will be a thousand years older. So it's that sort of thing. Your time has slowed down relative to what they've experienced. I had a weird nightmare about that the other night. Professor Fred Watson: Oh, did you? It was the strangest thing. I had a nightma. Um, somebody put me in, like, some kind of a cryo sleep. And I woke up and so

much time had passed that everyone I knew had died. And so I had them put me back in cryo sleep for thousands of more years until we discovered the technology to travel back in time so I could go back in time and link back up with everyone I loved. Professor Fred Watson: That's A pretty good one is that. I have a very active dreamscape. Uh, at night I wake up exhausted. Professor Fred Watson: Okay. All right. Well, our next, uh, question has a little bit of philosophy in it.

Um, this, this question is coming from Art from Rochester, New York. And it's, ah, it's quite a long question. So let's, uh, grab a cup of tea here. Art says, I was listening to the June 13 program concerning the flying banana, which prompted me to submit my first question to Space Nuts. It is a question I had been pondering for some time. You will be glad to hear it is not a black hole question, but

rather a what if question. The great American philosopher Julius Henry Marx once postulated, time flies like an arrow, fruit flies like a banana. Based on empirical evidence, I can confirm that fruit flies like a banana. My question revolves around time flying like an arrow. To the best of my understanding, when we shoot off rockets to the moon or Pluto, in order to get there accurately, the rocket scientists use an

amphimerus. M. You'll have to correct me on the pronunciations of that or possible amphimerds as a sort of a map. If faster than light space travel were possible, how could one navigate from point A to point B? Is it possible to develop an ephemeris for faster than light travel? Thank you, Art from Rochester, New York. Professor Fred Watson: A great question, Art. And, uh, yeah, your pronunciation is correct. Ephemeris is what these things are, and ephemerides is what a

lot of them, ah, are. So what's an ephemeris? Well, uh, the original meaning, um, and I guess this really is still the meaning of the word is, uh, to predict where, uh, planets are going to be, uh, in the future, where celestial objects are going to be. So, um, going back to my master's degree, uh, back, you know, 150 years ago, my work was on, um, the orbits of asteroids. And so there were two problems. First problem was how

do you take observations of an asteroid? And remember, all we had in those days was the direction that you could see measured with a telescope. How do you turn that into knowledge of the orbit of the asteroid, uh, in three dimensions? And you can do it. You need at least three observations to do that, but you can do it. You can mathematically deduce the orbit

from just three directions in space. But then once you've got the orbit, what you want to know is where it's going to be in the future, what's its direction in space going to be? And that is what an ephemeris is. It's how the position of an object changes, uh, in the sky, uh, over time. Um, so it comes from the word ephemeral, meaning stuff that's temporary. Uh, so an ephemeris, uh, is the, basically it's a table of where an object

will be over a given amount of time. And of course it's critically important these days because we now know that, which we didn't know when I did my master's degree. We now know that the Earth's locality is pretty heavily populated with asteroids. And there's, you know, we might want to know where they are

just in case one's uh, heading our way. So um, I, you know, I think the question, Art's uh, question is uh, a good one in the sense that, okay, he's saying, yes, we, we use ephemera, um, ephemerities to, to basically navigate to objects. Um, it's actually a little bit more than that because we, we use effectively a three dimensional map of where these, these planets are, uh, in order to dictate where they're going to be when

your rocket arrives there. And that's critically important of course, because you want the rocket to get to the orbit of for example Pluto, as Art mentions, uh, when Pluto is going to be where, whereabouts the rocket is. You don't want to reach the orbit of Pluto and find Pluto somewhere else. That's why you need uh, an ephemeris. But uh, if you could travel faster than the speed of light, and we've already shown that that's impossible, uh, in this episode because you need infinite energy to do

that, uh, to reach the speed of light. But if you could, um, the ephemeris would still work. Um, you would need to put in a negative number for the. I think the speed of light actually goes into ephemeris calculations. I remember it well. But I think you uh, put in a factor. It wouldn't be a negative number. It would be a factor that would allow for the fact that you were traveling at faster than the speed of light. So you could do it. It's not an impossible mathematical problem.

For what it's worth. Well that was fantastic. Uh, I just about understood that too. Professor Fred Watson: Sorry. Uh, no, you always do such a great job of explaining these. Um, my IQ is going up every time I'm um, involved on these, uh, these episodes. And also great questions. We have some of the smartest, smartest listeners. I mean these people are, are brilliant.

reddish ones. And I um, wonder how is that, Is it due to the fact that um. Or is this like the red shift because they're moving away, which I kind of doubt, but I don't know what, what is it else?

Or is there so much material of a different, of different kind in the galaxy that appears for us more red or more blue. So would be nice if you could explain that. And um, also I wonder a bit. Let's imagine we would travel to this far distant galaxies. Um, if we could do it potentially would it not be some kind of travel through the time? So because when we look back there, right. We see them on their early stages. So till it's a long time until um, until the

light reaches us. And if you would travel to that far distant uh, galaxies you would basically. Or what I imagine is like you would travel through time, right. So if you did, the moment you come closer and closer the galaxy or maybe let's think of a single planet would then change its appearance, right? So you would see that it's alter, uh, it shifts maybe its base or it merges with another galaxy. Um, is my thinking correct, Would it like the

far. The closer you come the more it would change its shape and it, I don't know, colors maybe. Um, and things you would see. Um. Yes, thanks for taking my questions. Um, like the shop and, and um, till then.

And that's the bottom line. But there's a few caveats here. Let me just explain what I Mean, um, redshift is the phenomenon that, uh, as light travels through an expanding universe, uh, the universe is expanding, light is making its way through the universe, but as it goes, the universe is getting bigger. And so the light's wavelength is actually being stretched. Uh, and, uh, as you stretch the wavelength of light, it goes redder. It goes to

the redder end of the spectrum. And so that's what's happening. But the caveat that I mentioned is that these are actually false colors in the sense that the James Webb telescope is an infrared telescope. So it is looking at light that our eyes are not sensitive to. It's actually redder than red light that it's looking at. So what the mission scientists do is they, um, they take the shortest wavelengths that the Web can see, which are really beyond our.

They're redder than red for us, for our eyes, but they're the shortest wavelengths that the red can detect, and they make that blue in their colors. And then the longest wavelengths that the Web can detect, they make it red in their colors and that. So that mimics what we would see with our eyes, uh, with visible, you know, visible light, but it

mimics it moved into the infrared. So it does mean that as objects, uh, you know, get redder, uh, in the infrared spectrum, we see them redder, uh, in the James Webb telescope images. And that's exactly the reason the most distant objects are so highly redshifted, that you're seeing them as red objects compared with the white objects, which are the much nearer ones. So David's right on that front. His second question, uh, what would some of these galaxies

we're looking back, you know, up to. I think the record is looking back 13.52 billion years at the moment, which is 280 million years after the birth of the universe. It's a big puzzle as to how galaxies got so big and so rich, um, in that short period of time. But that's for the cosmologists, not for us. Um, they'll work it out. It'll be okay. Uh, the bottom line, though, is that if you could forget about the journey, because

we can't travel the sort of speeds that you need. But if you imagined yourself, uh, instantly transported from our, uh, vantage point here on Earth to one of These early galaxies, 13.52 billion years, billion light years away, what you would see would be a galaxy that might look a lot like ours. It has evolved because you're seeing it. I mean, you've got to imagine we're being transported instantaneously. So that what we see is what's happening now. That galaxy will have had 13.52

billion years of evolution. It'll be quite different. It might actually be quite a boring galaxy compared with the very, uh, energetic, uh, infant galaxy that we look at with the James Webb telescope. Complicated answer to a simple question, but David's right on the money. That is such an interesting way of thinking about that. I, um, I'm going to be spending, I'm going to be spending a while wrapping my head around that one.

Professor Fred Watson: Okay, we checked all four systems and seeing where to go space nets. Um, our last, our last question of the evening is from Daryl Parker of South Australia. Daryl says, G' day, space nuts. I'm not sure of the best way to ask this question, so I'll just ask it the best way I can. That's usually, that's usually the, the best way. Uh, do objects, meteors, asteroids, comets, planets, stars, solar systems and galaxies

produce heat as they move through space? Is it friction or is friction a thing in the vacuum of speed and the vacuum of space? Thank you in advance. And that's Daryl from South Australia. Professor Fred Watson: Uh, another great question. Um, so if space was a complete vacuum, and as I'll explain in a minute, it's

not quite. But if it was a perfect vacuum with nothing in there, then, uh, there would be no friction, uh, as Daryl's calling, um, would be, uh, uh, you know, there'd be nothing to, uh, to limit the speed of motion, uh, of an object moving through it. And it wouldn't get hot. There would be no friction to heat it. And I think the way Daryl's thinking here, and it's quite right

to, uh. When a spacecraft enters the Earth's atmosphere, uh, it's the friction between the spacecraft itself moving against the air molecules that causes it to be heated and gives us this heat of reentry. There are a few subtleties to that, but that's basically the way it works. So things moving through an atmosphere get hot. Um, now, uh, space beyond the Earth's, uh, atmosphere is not a vacuum.

It's very nearly a vacuum. And that's why you can put a satellite up and it'll stay up for 200 years or whatever. And it's why, you know, the Moon doesn't come crashing down to Earth. In fact, the moon's going the other way. It's moving away from the Earth very slowly, but the, um, it's nearly a vacuum, but it's not quite so. Uh, there is basically, um, a very, very slight braking effect, uh, which in the Earth's vicinity, the Earth's

atmosphere doesn't just stop, it sort of fades away. So even 10,000 kilometers away, there's still a little bit of residual atmosphere, which would have a slowing effect on a spacecraft. When you get into interplanetary space, there's a lot of dust and there's, there's also subatomic

particles there. When you get to interstellar space, the space between the stars, there is something that we call the interstellar medium, uh, which is basically the radiation and particle environment of interstellar space. There are subatomic particles all through space. Now there, it's still so much of a vacuum that there's nothing really to heat a spacecraft. So Voyager, as it ventures through interstellar space, is on the brink of interstellar space.

Now that, uh, won't get hot because of that, um, because the friction is far too small. But when you do see its effects, uh, they are on very big scales. And we do see, uh, when we look at some objects deep in space, for example in a gas cloud, uh, a nebula, where, um, maybe there are stars forming, sometimes you see objects which are moving through that gas cloud. And what you can see is a shock wave, uh, being generated.

And sometimes that causes star formation, that shockwave of the gas cloud. Um, now, yes, that's Jordy agreeing with me there. Uh, he's just come back from his walk, so he's very enthusiastic about this idea. Uh, he's probably seen a shockwave. Um, and a shockwave is what you get when something moves rapidly through the atmosphere. You know, that's what causes the sonic boom of a supersonic jet. Um, so with very big objects in gas clouds in space, then you do get that sort of

effect. The interaction between the moving object and its surroundings generates a shockwave and would generate heat as well. So under certain circumstances the answer is yes, Darrell, but probably for most things it's no. So. So, Fred, I don't know if you'd have time for a follow up question of my own. Yes, um, so I guess I never really thought of, um, the gravity atmosphere around planets having

different layers. It's like, I knew there was layers, but it's like to really think, okay, you know, it gets thinner and thinner and thinner, but there's still particles, uh, being pulled into that atmosphere. But it just, it spreads out quite a ways well beyond our atmosphere. Are there points of space, and you may have already mentioned this, but are there points of space where there's particles floating around that are not being affected by

any gravity at all? Or is every part of space affected by something's gravity? Professor Fred Watson: Um, yeah, pretty well. Um, the thing about gravity is it, it goes on for

infinity. Um, it's, ah, it's a bit like actually light is the same. Electromagnetic radiation will not stop. It just keeps going until it gets too weak to be detected. You're talking about a dribble of, you know, hardly any photons. Gravity is the same. We don't know whether gravity has a subatomic particle equivalent. We think it might have, and

we call them gravitons, but they haven't been discovered yet. But yes, uh, that's actually, you know, it's why, uh, an object like Pluto, way out there in the depths of the solar system, is still in orbit around the sun, even though it's all these, what is it, five, six billion kilometers away. Um, the gravity of the sun is still a force because gravity goes on forever.

Uh, but of course, when you get way out into interstellar space, then you might feel the sun's gravity, but you'd also feel the gravity of other stars. Uh, and so I think you're right that there is always going to be a sort of gravity background, uh, because of the objects which are in the universe. Maybe it's pretty near zero in the space between galaxies, uh, which is pretty empty, although there are

subatomic particles there too. Uh, but, uh, yeah, but no, it's a. It's a very, um, A very compelling force is gravity, which is just as well because otherwise we wouldn't exist. There's always something pulling. It's just going to be stronger or weaker. No matter if it's. No matter if it's the biggest gap in the known cosmos, there's still a little thread pulling us together. Oh, that's so beautiful. That's kind of cool. We're all connected somehow.

Professor Fred Watson: That's a connection. That's right. Yeah. Um, Fred. Well, this has been a very enlightening Q and A episode of Space Nuts. Thank you so much for sharing your wealth of knowledge with us. Um, while your rooster. I'm sorry, your dog. Sings his song in the background. Professor Fred Watson: That's what he sounds like. I know. Um, his voice hasn't broken yet. It's kind of cute. It's endearing. Um, thank you so much. Professor Fred Watson: This has been, been.

This has been fantastic. And, um, we will, we will, I guess, catch you guys next time. Please keep sending in your amazing questions. And, um, real quick, before we go, we are going to play a, uh, another, um, another update for you. So this is your little Treat for listening to the whole thing. We've got an update from Andrew, your beloved regular host. I know you guys probably miss him because your questions are still addressed to him, but, um, he's on his trip

around the world. Going to let that, um, play back now.

much worse. We were having lunch in one of the restaurants at the back of the ship and we got hit by a weather front. It felt like we'd been rammed and the. The ship tilted over 7 degrees and it stayed there for the rest of the day. It just hit us out of nowhere. The captain had to do some heavy maneuvering to get us, uh, into. Into a, you know, better position. And they had to move, um, the ballast to, uh, keep the ship, uh, balanced and upright as much

as they could. Uh, yeah, it was pretty harrowing. And the weather never got better, uh, until we got into Adelaide and were in protected waters. But, um, the Adelaide was fantastic. Went to, uh, Handorf, as I mentioned, that little German village where the German people. People came in all those years ago. They were, um, they were basically escaping, uh, Prussian oppression when they came out here in the 1800s. And, um, yeah, made it, made a German town, which is fantastic. Had, uh, a good look

around Adelaide, although the weather was terrible. We went to Mount Lofty, which is one of the best views in Australia. And all we saw was cloud and very strong winds. It was, uh, it was quite nasty. Got back on board, uh, we had to stay the night in Adelaide because of the conditions, hoping they'd settle down. And we did have some good sailing until we got to the West Australian border and then another weather front hit us and it got rough again

and. Yeah, gosh. And just to top it all off, we had a galley fire in the middle of the night at one point, which they dealt with very, very quickly. So it's been a bit of a dog's, uh, breakfast of a cruise in some respects, but we're still having a fantastic time. We stopped at Fremantle again, um, because of the weather. We were very late and so we stayed the night. We have friends in Fremantle so We spent the evening with them. It was fantastic. And we set sail again yesterday, headed west.

We leave Australia now, headed for Mauritius. That'll be a seven day crossing of the Indian Ocean. So that's where things are at with our uh, current tour. Um, we're really enjoying ourselves. I must confess. The crew here is fantastic. And uh, you know, with over 2,000 Aussies on board, we outnumber everybody about 10 to 1. Which is, which is good. But so many nationalities. Hope all is well back home and in Houston of course. Heidi, look forward to talking to you next time. Uh, no, Aurora.