Cosmic Queries: Weighty Matters, Stellar Ages & Moonless Earth Scenarios | Space Nuts: Astronomy...

[00:00:00] Hello again and thank you for joining us. This is a Q&A edition of Space Nuts. This is where we stand in a queue and go, ah, yeah, or not. No, it's where we answer audience questions. We've got questions today about weight variations on Earth depending on where you are. I know we've been down that road before, but we're going to do it again.

[00:00:22] The age of the solar system has been brought up again. Visiting another star, would we be able to do that anytime soon? And Earth minus the Moon, a what-if question that we have done a trillion times, but why not? Let's reroute to that little what-if scenario. That's all coming up on this edition of Space Nuts.

[00:00:45] 15 seconds. Guidance is internal. 10, 9, ignition sequence start. Space Nuts. 5, 4, 3, 2. 1, 2, 3, 4, 5, 5, 4, 3, 2, 1. Space Nuts. Astronauts report it feels good. And he's back again to solve all your riddles. It's Professor Fred Watson, astronomer at large. Hello, Fred. Hello, Andrew. I'd love to be a riddle solver.

[00:01:11] Yes, it's a good thing to do. Even when you can't. You can just pretend. That's what we do all the time. I like the Q&A edition. It gives us a chance to hear other voices from around the world who listen to us. And sometimes we learn more about them than we expect to. Like Andy the train driver in Sydney. And we've had a few over the years. Rusty from Donnybrook, one of our regular sender-innerers.

[00:01:37] And Sandy in Melbourne. And oh, gosh. And plenty of others. Plenty of others. And if I didn't name you and I should have, I apologize. Martin. We should not mention Martin. We've got pilots as well. We have. We have. Hannah. That's right. I haven't heard from her in ages, but I hope she's well. Now, let's maybe get to our first question. Fred, this comes from DJ.

[00:02:05] Hi, guys. DJ from Indianapolis, Indiana, USA. You, in a recent podcast, talked about how if a person weighed 100 kilograms on the North Pole, that they would weigh 99 at the equator. My question would be, if you were to take a submarine up to the North Pole,

[00:02:29] you pop up through the ice, you hop out with your bathroom scale, stand on the ice, and it says you weigh 100 kilograms. You take that same scale, drive the sub down to, say, Ecuador, get out on the beach, put your bathroom scale down,

[00:02:48] and now would it then say you weighed 99? Or are bathroom scales calibrated for Earth's gravity at, say, the equator, and it would say you weighed 99 at the North Pole too? Would you need scientific instruments to tell the difference?

[00:03:11] Or could a normal person with a normal scale tell that they weighed a kilogram less at the pole than they do at the equator? Thanks, guys. All right. The first flaw in his question is putting the scales on sand would probably completely mess him up. But look, we know we get the gist. Yeah, 100 kilograms on the North Pole, same set of scales at the equator or Ecuador,

[00:03:38] 99 kilos. Does that sound about right? It is. It's perfectly right. Yeah. Yeah. And it would show up on the scale. I mean, bathroom scales are notoriously inaccurate. They are. They're not accurate to 1%. But if you did have a really accurate scale and you can get them, then it would show the difference. It would be 100 kilograms on the pole, 99 at the equator.

[00:04:10] And that's because what you're measuring your weight against is something that doesn't change with gravity. And that's the spring. You know, you're standing on something that's spring loaded and the spring behaves the same, no matter what gravitational field you're in, it still exerts the same force. And so it will feel

[00:04:29] less weight from you at the equator than it does at the poles. Now, I think that's fairly common knowledge that happens, that you weigh less. Probably most people don't realize that it is actually 1%. It's almost exactly 1%, which is a bit of a coincidence. But it has four sources, not just one. So the weight

[00:04:57] that you feel are determined by, first of all, the Earth's gravity, which is a property of the planet. But then you've got the Moon's, the Sun's gravity as well, pulling on you and the Moon's gravity too. And then the thing that I think most people think about is the centrifugal force, the fact that the Earth is rotating. And that gives you a centrifugal force that tends to lift you a little bit.

[00:05:27] So, and that's the case. When you look at the Sun's gravity and the Moon's gravity, they're basically, they're very, very small and they tend to cancel out anyway. The centrifugal force comes about because on the equator you're travelling at 1600 kilometres an hour eastwards,

[00:05:49] and that motion, because it's on a curve, has an acceleration represented, which cancels out a little bit of the gravity. But the other one is the Earth's gravity itself is different. Even if the Earth was not rotating, there would still be a difference at the equator from the pole. And that's because the Earth is not a perfect sphere. It's what we call an oblate spheroid. It's slightly flattened. So you're,

[00:06:17] I can't remember how far it is, you're 30 kilometres away or something like that, further away at the equator from the centre of the Earth than you are from the pole. Let me just, I can do this in my head. It's actually 20, 21 kilometres is the difference. You're 21 kilometres further from the centre of the Earth when you're on the equator than you are at the pole. And that

[00:06:45] means you're higher up, and so you feel slightly less gravity. And when you add that to the gravity change you get because of the Earth's rotation, it comes to basically 1%. So really, yeah, quite a nice calculation. And also quite a nice question from Vijay because, or DJ, I didn't quite catch which. But good to hear from you in Indiana.

[00:07:10] And it's a well-directed question. But the answer is yes, you'd see on your bathroom scale if it was accurate enough. Yes. I took, we took some bathroom scales on a cruise ship once and yeah, don't use them at sea. I weighed everything from 60 to 190 kilos in a matter of seconds. It does remind me though of when I was a kid. My dad was a pharmacist for almost his entire career.

[00:07:38] And back then when you didn't have scales at home or very few people did, you'd go down to the chemist. And you'd put in, in Australia, you'd put 20 cents in the slot and stand on the scales and it would give you an accurate weight. Last time I used one of those, I was 11 stone. Yes. Things are moved.

[00:08:01] Remember, 11 stone. Now, 11 stone doesn't mean much anymore. But I'll work it out. Equals kilos. And the answer is 69.85 kilos. Well, I weigh a little bit more than that now. Probably not that much more. Probably about 15 kilos more. Oh, yeah. Right. Okay.

[00:08:26] Yeah. 11 stone back in the day. Yes. I was quite proud of that. But you don't see them anymore, do you? Those scales out in front of the pharmacies. Well, no you don't. There used to be, you found them on railway stations as well in Britain. I don't know why. Yeah. Well, they used to have them at railway stations for weighing packages and things like that. Yeah. And post offices and things. Yeah. Yeah. All right, DJ, thanks for the question. But yeah,

[00:08:53] it's true. If you were to take a submarine, pop up at the North Pole, put your scales down and weigh 100, then go to Ecuador and do the same thing, you'd weigh 99. Now, our next question, Fred, it comes from Nick, who is in Cambridge in the UK. He said Cambridge, the UK one, just so we didn't get confused with Cambridge in the United States, I assume. There'd probably be

[00:09:17] more than two. Now, he says, as you answered my previous question so eloquently, I came back for a second helping. We must have been rude. Wouldn't have been you, Fred. The solar system is 4.6-ish billion years old, but it formed from material that is older. Are there any estimates for how much older

[00:09:39] this material is and can this help us date any supernovae that may have generated it? Or was the solar system formation process so energetic that it reset isotope ratios everywhere within the sun's sphere of influence, much like heating rocks above their Curie point resets isotropic ratios? Thank for the enlightening, enlighten me twice a week. It keeps me relatively sane, if you can believe it,

[00:10:08] Nick from Cambridge, the UK one. I like it. It's a good question. A couple of questions in there. So, yeah, I like where he's going with this. And it's one, I think it's fair to say that this is a question still on the front line of research. Because when you look through the, you know, the astronomical

[00:10:32] literature, you find a lot of stuff about the solar nebula. The solar nebula is a cloud of gas and dust, which the, basically the solar system was born in by this process of gravitational collapse. It collapses under its own mass. And start spinning and the spinning produces a disk. So you've got a

[00:10:55] hot ball of gas in the middle, which becomes the sun. And this disk of rocky material and gaseous material as well, swirling around it, which is the protoplanetary disk. When you look at papers, they're nearly always in the middle of the solar nebula. And I think it's a lot of the things that are going to be in the middle of the solar nebula, just in terms of the mix of gases. It's mostly hydrogen and helium

[00:11:22] with a few pollutants, which are what eventually made the rocky planets and the likes of us. But there's not that much work done on exactly the question that Nick is asking. You know, can you identify what supernovae were the remnants of the supernovae explosions, which include heavy elements as well

[00:11:51] as the hydrogen and helium? Can you identify the dates of those supernovae? Now I have a recollection of seeing some papers that refer to evidence in meteoritic rock, I think, that suggests that some of the material of the solar system dates from about eight billion years ago, remembering that the age of the solar system is more or less 4.6 billion years, exactly as Nick says. And we know it

[00:12:20] actually a bit more accurately than that, but that's the easy number to remember, 4.6, 4.7 billion years. So yes, we do know it formed from material that's older, but I think it's turning out to be quite difficult science to actually detect that. And that may be because of the second part of his question,

[00:12:42] although I suspect that the isotope ratios were probably preserved rather than destroyed as per the Curie point. I'm sorry this sounds like a waffly answer, but I haven't really been able to pin down much research on this. There was a spacecraft that was launched back in, I think about 2001,

[00:13:07] that it was called Genesis. And it was a NASA experiment. And the idea was to catch particles of the solar wind and bring them back to Earth. And the solar wind is basically nuclei of gas, they're mostly hydrogen, but you can also detect any sort of pollutants. And in a way,

[00:13:28] what you're trying to do there is analyse remnants of the cloud of gas and dust that form the solar system. You're trying to analyse traces of that gas and dust. And it's similar to what we do with comets. We try and analyse comets to death because we know they're pristine objects. They've never been

[00:13:49] hot. They're just samples of the solar nebula frozen onto dust crystals. But Genesis, unfortunately, had a problem. The capsule that was sending back this material, actually one of the parachutes didn't open and so it crashed at, I think it was 200 kilometres an hour, it hit the Earth and broke.

[00:14:14] Luke. So there was some contamination, but I think there was some research done on it. But I don't think they got to the real nub of the matter. You know, what's the solar nebula made of? I'll keep looking at this because it is a really interesting one. And if we come across any more definitive papers, we might be able to give Nick a shout out later on.

[00:14:37] Luke. So he's dug up a mystery, basically. He's come up with something we can't quite grapple with. Luke. That's right. Although I think, as I said, you know, and unfortunately I haven't been able to find the papers that I've read where it does suggest that we've got evidence for supernovae in the past, which are maybe 8 billion years ago. So nearly twice the age of the solar system. But supernovae in the environment that we

[00:15:02] are now in, which would have contributed to the makeup of the solar system. Good question. Luke. It is fascinating. Thank you, Nick. We'll get back to you shortly. This is Space Nuts with Andrew Dunkley and Professor Fred Watson.

[00:15:28] Luke. Yes. And you're listening to a Q&A edition. And our next question comes from Keith. Hey guys, this is Keith in Vancouver, Washington, USA. And I'm just curious about interstellar space travel. How long do you think it's going to take for a human to be able to reach another star?

[00:15:56] It seems fairly restrictive with the distances involved and, you know, what kind of travel it would take, be it warp drive or laser sail. But I'm just curious what you guys think how long it's going to take for us to get there and how realistic it's actually going to be, if anything

[00:16:26] will ever come of it. Thanks guys. Love the podcast. Thank you, Keith. Great to hear from you. There's another place that's not where we would normally think it was. Vancouver. Like you automatically go, oh, that's Canada. But no, he's in the US version. Oh, yes. But Keith, that's a great question. I suspect it'll be a spaceship before it is a human

[00:16:51] being going to another star system or another star for that matter. The nearest one is what, Proxima Centauri, which is 4.41 light years away. So using conventional engines, you're looking at a trip of over 6,000 years. 60. 60,000 years. Yeah. Yeah. Right. Okay. Well, you know,

[00:17:13] don't forget to take some eggs because they don't keep that long actually, but it's a difficult one. And it sort of goes back to what we were saying in the previous episode with Elon Musk and, you know, getting, you know, shooting around all over the solar system or all over the galaxy in the future.

[00:17:38] It's not probably a high priority at this stage. And I think the day will come where we'll be able to go faster, but whether or not we can go fast enough to make a trip to Proxima Centauri, you know, reasonably quick, like at 99% relativistic speed, it would still take you

[00:18:04] about three years, I think. Well, it would, no, it must be more than that. No, well, I'm talking, it'd take, it'd take you five. I worked it out and actually, it would be, yeah. At light speed, it takes you 4.3, 4.4 years. Yes. And it, but you're right. But you've got to take into account time dilation. You do. You've got all of that thrown in as well. Yes.

[00:18:32] And it, yes, it's hard to envisage. I mentioned in our last episode, something about some work I'd seen that suggested that light sails weren't going to be the answer for this, because when you get to high enough speeds, you get this drag that actually slows you down and you've just got to put so much

[00:18:53] energy into your laser pointing at the light sails, that it really is probably not, not going to work very well. The, the, the, perhaps the nearest we've got to seriously thinking about interstellar travel has been the, what was it? Breakthrough. Starshot.

[00:19:16] Starshot. That's the one. That project, which was a feasibility study funded by a Russian billionaire, whose name was on the tip of my tongue a minute ago, but has now disappeared as names tend to do. Milner, Yuri Milner. That's his name. It is. Yeah. And they, and, um, Breakthrough Starshot was feasibility study to see whether we could within a kind of human lifetime. And I think they were thinking of 20 to 30 years,

[00:19:47] get a spacecraft to the vicinity of Proxima Centauri, the nearest star. Yeah. Now, interestingly, while you were talking, I asked ChatGPT to work it out. And for people on Earth at 99% of light speed traveling from Earth to Proxima Centauri, it would be a, um, 4.3 year journey to get there. However, when you take into account time dilation, which becomes significant,

[00:20:17] the people on board would only age seven months is what it's saying. I think they're missing something. Yeah. In that calculation. Um, it's probably not that far off. Yeah. It might not be just thinking about. So the Earth perspective is a 4.3 year journey. The on board travelers would experience seven months. It's critically dependent on how near the speed of light you get to.

[00:20:47] This is at 99%. Yes. Yeah. Uh, so yeah, yeah. It's, it's kind of roughly something like that. I'm sure. I always used to use an example of, um, going to a star a thousand light years, sorry, a star 500 light years away. So you make a thousand year journey as elapsed on Earth. And the turns out that,

[00:21:11] uh, I think it's 99.99995% of the speed of light. Yeah. Uh, which is almost the speed of light, but the people on board have only aged 10 years. So you've in 10 years, you've gone a thousand years into the future on Earth. Um, it's crazy, isn't it? It's bizarre. Yeah. But, but the physics, you, so I, uh, you know, as I said in last week's episode, I think to talk about interstellar travel,

[00:21:37] uh, certainly for humans at the moment, physics just says no way, Jose. It's not going to happen. My new book says otherwise, but we'll- Of course it does. Yeah. But that's, you're in the real world of science fiction. Yes. Exactly. Rather than the artificial world of, uh, relativity. Yeah. And just, uh, to put Keith right in the picture, um, you know, if you want to get to light speed, we're a little bit behind

[00:22:04] at the moment, uh, the Parker solar probe has, uh, currently got the, um, the space speed record of 0.064% of the speed of light. So we, we, we're nowhere near 1%. We know we're near 0.1%. Yeah. It's wasn't it, is that 190 kilometers per second? I think. It is. Yes. Yes. Give or take.

[00:22:28] Um, that's as fast as we've ever been, um, as, as a, as a species. But, um, the day will come, we'll, we'll get faster. Yeah. If we could achieve 2%, that would, um, that would make traveling to the outer solar system so much quicker. Yeah, it would. Yes. It would take it, you know, we'd drop the travel time to weeks. Yeah. Yeah. It would be amazing. So, you know,

[00:22:52] we don't need the speed of light yet, but we, we do need to probably get a bit quicker. But, uh, yeah, it, it's an impossible dream at the moment. Keith, I think would be the answer to your question. But, um, we won't give up. I'm sure humanity will figure out a way to do it at some stage. Uh, but right now, if we want to go anywhere, we've probably got to build a spaceship big enough for

[00:23:17] multiple generations to live on. That will be the time they get there. They'll go, what, what, can I remember why we were coming here in the first place? Like this place is the pits. Why did we come here? Exactly. Hmm. Thank you, Keith. Great to hear from you. Now, final question comes from Mark. I love this question because of the first sentence.

[00:23:44] Mark says, am I the only person to have watched space 1999 back in the seventies? No, you're not, Mark. I was a huge fan. I loved that show. Um, it, it, uh, was on, uh, it was a British show, a British science fiction TV program that ran for two seasons, 75 to 77. Um, I watched it on, uh,

[00:24:08] uh, Australian television and, uh, it follows 311 inhabitants of moon base alpha, which is hurtling uncontrollably into space due to an explosion of nuclear waste stored on the moon's far side. And this is what's prompt Mark's question. Uh, I clearly remember a big nuclear explosion in that show. And next thing, the moon and the inhabitants of the moon, uh, of moon base alpha are sent off

[00:24:35] on their merry way into deep space, leaving the earth, uh, to wobble on its axis on the bright side. I do like to sail, so I wouldn't have to worry about tides. So, you know, that's pretty cool. Um, what are your thoughts? PS, I have cracked the screen on my phone, so this might not make much sense. Uh, keep doing what you're doing. It brings me smiles. It brings a smile to my face. That comes

[00:25:01] from Mark. Um, so yeah, all right, whatever reason, uh, but in this case, it was nuclear waste explosion that sent the moon careening off into the heavens and left earth all on its lonesome. Cause and effect. Um, what would be the effect? Uh, as well, you know, beyond the fact that the oceans would be much calmer and you could sail quite happily or would they? No, no, I didn't think so.

[00:25:29] No, I think the, you know, it's the, it's the, um, it's the, the currents in the ocean and the atmosphere itself that really dictate what's happening to the surface of the ocean. The, the tidal phenomenon is just a really low frequency effect to high tides a day. Um, and it, yes, it does mean water's moving around, but, uh, the main, the main, um,

[00:26:00] kind of source of motion in the oceans, I think are these currents that we're concerned about because the atmosphere is changing. Uh, oceans are warming up and some of these currents are forecast to possibly switch off. Like the one that's closest to my heart in, because it's where I grew up, but the, uh, the Gulf Stream Drift, which is a current that comes up from, uh, the, basically the West Indies, uh, and crosses the Atlantic and keeps Scotland warmer than it otherwise

[00:26:29] would be. Uh, it's, um, and, and of course, Western England as well and Ireland too. But it's, it's why you can find when you look down the West Coast of Britain, you can find palm trees, uh, growing in people's gardens because of that phenomenon. Of course the coconuts have floated over. David Morgan Something like that, yeah. Um, whereas, uh, without it, uh, we'd feel very much more severe winters. Oh, they would up there, because I'm now Australian, of course. Yeah. David Morgan Yeah.

[00:26:58] David Morgan So, uh, it, it's not going to do much to calm the ocean. Uh, it would get rid of the tides. Um, it might, as, uh, as Mark alluded to in his question, make the earth wobble on its axis a bit more, but that would be over timescales of tens of thousands of years. Uh, and we might be able to cope with that. But, um, of course we'd miss it because the moon is very romantic. Yeah. Uh, and, um, yeah. David Morgan It's a good thing to photograph some nights.

[00:27:27] David Morgan It's great. That's right. It's good to have. Yeah. David Morgan It wouldn't make life impossible for us if it vanished. David Morgan No, it wouldn't. David Morgan It would change life, definitely. But, uh, yeah, I mean, especially the accelerations that it would produce as it rocketed off into space might certainly upset things here on earth. There'd be a gravitational influence on that. It could change the length of the day. David Morgan Yeah. That's a thought.

[00:27:54] Well, um, you know, people working harder and harder, you'd probably want the day to go longer. David Morgan I don't know. I don't know what would happen. David Morgan It could be interesting though. David Morgan Well, it could, but, um, hopefully it's not going to happen. David Morgan No, it is moving away from us though, Mark. And it will, yeah, it will reach a certain distance and then that'll be it. It'll stop. It's not going to keep going away. David Morgan That's correct.

[00:28:21] David Morgan Yeah. But, um, but at the moment we're stuck with it. Um, that big gray rock that just sort of looms over us and looks pretty. David Morgan Oh, and, um, David Morgan Lights up the night. David Morgan It's great. David Morgan Yes. May soon have a colony on it. Fred's really thrilled about that. David Morgan I don't mind a permanent presence, but, um, the idea of, you know, settling on the moon is... David Morgan Ah, that's Elon's, that's Elon's goal now. David Morgan He's given up on Mars.

[00:28:49] David Morgan Well, yeah, no, he's talking about Mars as well in the, David Morgan Oh, I know. David Morgan With the latest, that's the latest. He's still got, David Morgan Yeah, but I think he's decided we'll go to the moon first and we'll see how we go there. David Morgan Yeah. David Morgan A bit worried about flushing toilets, but we'll figure that out. David Morgan Oh dear. Mark, thank you. That's a great question. Lots of fun. And yeah, Space 1999, probably one of the shows that really switched my brain on to science fiction and I haven't let go of it.

[00:29:19] David Morgan Terrific show. David Morgan That brings us to the end, but if you do have questions or comments for us, please visit our website because we'd love to hear from you. And if you've thought about sending in a question and just never got around to it, well, get around to it. SpaceNutspodcast.com, SpaceNuts.io are our URLs, because we've got a two for one package. And you can just press the AMA button at the top, which means ask me anything and send us your audio or text questions. Don't forget

[00:29:46] to tell us who you are and where you're from. We always like to know. We've got people all over the place, but more listeners in Iceland than anywhere. We're number one in Iceland. It's very exciting. But I think we're number two in Australia and number something, number nine in America or something. David Morgan Yes, number five in the UK, I noticed. David Morgan Number five in the UK. What happened to the other two people, I wonder? Anyway, Fred, we've reached the end. Thank you so much.

[00:30:16] Fred Great pleasure, Andrew. Always good fun. David Morgan And thanks to Hugh in the studio who couldn't be with us today, which is why we're number two in Australia instead of number one. He just never listens. And from me, Andrew Dunkley, thanks for your company. We'll see you on the next episode of Space Nuts. Bye-bye. Space Nuts. You'll be listening to the Space Nuts Podcast. Available at Apple Podcasts, Spotify, iHeartRadio, or your favourite podcast player. You can also stream on

[00:30:46] demand at bytes.com. This has been another quality podcast production from bytes.com.