#434: Gravity, Energy, and Hidden Galaxies: Listener Queries Unpacked

Hi there, This is Space Nuts Q and A. My name is Andrew Dunkley. Great to have your company coming up. On this episode, we'll answer questions from Steve, Gus and Nick. Steve and gusso are sort of focused on the same thing gravity. Steve wants to know if it can exist without mass, and Gus is talking about gravity and energy and what's the relationship. And Nick is asking about galaxy movements and are any moving towards us that we can't see yet? Well, we don't know, we can't see them yet, but we'll see if we can tackle all of that on this episode of Space Nuts. Fifteen seconds guidance in Channel ten nine ignition sequence Space Nuts or three two one Space Nuts can I reported Neil Good. Here he is again, Professor Fred. What's a hello? Fred? Hello? Hello? How are you doing now? I'm doing the same as it was before. How about you? Well, I'm still doing the same as it was before. Yes, that's right. I hope to be doing the same again very soon. Yes, indeed, yes, Shall we just sort of muck in and get these questions sorted out? It was like a couple of weeks ago we had gravity questions coming in thick and fast, no black hole questions, but today it's gravity questions. And first our first one comes from Steve. I go to the Steve on promm. We'll enjoy your show. Recently, you've read an article implying that gravity could be possible without mess, and I'm wondering if that would be alternative explanation two two dark matter and to wand you have enough makes it very clearly anyway, all right, Steve, thanks for the question gravity without mass. Well, I doubt that we can turn to the Catholic Church because they do have mass, but terrible. It's an interesting question, though, it is. And so yeah, my reading on this, excuse me, is yes, that's correct. So actually there's a nice thread about this on Reddit if anybody looks at that website. And well I love Reddit, yeah really, well I do remember my one of my sons was an absolute Reddit fiend at one time. He was very much a Reddit fan. Now, so that's how I was aware of it, but I hadn't been a great user of Reddit. But the bottom line, excuse me, is, and this is the way is phrased in this particular conversation. If you increase the temperature of an object, and they take a planet in this case, and in fact, I might just read it because this kind of is quite interesting. Take your Neptune. You'd take your neptunean planet something the size of Neptune, raise the temperature by three hundred degrees calving instantly. Now, the massive neptune is about tenth to twenty six kilograms, and if we roughly assume all its hydrogen, it corresponds to about six times tenth to fifty two particles of hydrogen. It's the thermal energy is roughly given by an equation they're equal, which leads to an increase in thermal energy of deaded and it's a large number of duels. Actually it's a small number of duels. It's ok times six times tenth of minus fifty two times three hundred duels, which if you then convert that So what this is saying is you warm up a planet, you get an increase in the thermal energy of that planet. You can then use equals mc square to convert that thermal energy into mass, and in this case it comes out to be something like three times ten to fifteen kilograms, which is a lot, but is not very much in comparison. With a planet, but that does mean that adding energy to something will increase its gravitational mass. Now, the Steve's sort of, you know, next step in the argument from that is whether that could be misleading us in the idea of dark matter and things of that sort. And I can't really get my head around how that would work. He mentioned moms as well modified Newtonian dynamics, because my understanding is that everybody who looks at these particular problems, what is dark matter, what is dark energy? They take into account everything I've read some of the papers on this and so things like you know, gravitational gravitational influence of pure energy, and in this case we're talking about heat energy that is likely to be something that would be already in the equations. So I don't think it's the answer, but it's a really interesting suggestion and interesting thing to think about. So so thank you very much, Steve. Yeah, indeed just made me wonder are we increasing Earth gravity because we're heeding the planet up? Yep, that's probably right that I mean, the example that I just read out was about three hundred three hundred degrees calvin an instant increase in that we're talking about one or two degrees kelvin, but which makes a big difference to this atmosphere, but probably not that much difference to its gravitational potential. Okay, so the answer is yes, gravity can exist without mass, but it's probably not a major factor. Is that fair enough? Yes? That is right. I have just been dragging through my memory andrew something else that's sort of vaguely related to this, which is the We haven't this name, but we did talk about it a while ago, google blitz. Do you know what a google blitz is? Look, I've heard this before, No, remind me? Yeah? So's it? Basically is a black hole made of light and Wikipedia says it's a concentration of heat, light, or radiation so intense that its energy forms an event horizon and becomes self trapped. In other words, if enough radiation is aimed into a region of space, the concentration of energy can warp space time so much that it creates a black hole. It's a black hole as a black hole whose original mass energy was in the form of radiant energy rather than matter. Now, there is a paper that was published in twenty twenty four that concludes that a phenomenon like this cannot occur in any realistic scenario within our universe. So google blitz is are a theoretical entity that are not I thought not to occur in nature. But it is a similar thing, isn't it. Basically it's a it's a black hole made of energy. Yeah, wow, that's really interesting. I'll tell you something else that does exist is a Google scriber. So I've got one of those, how have you? Yeah, there is Langen German. Hold it up, okay, google scriber, Google scriber. Yes, you know what German is. You know the German is for pencil. I probably did once, but I don't know. That's blastiff, it's probably I only I know did languages at high school, and I was very good at them, and I should have probably pursued that somewhere along the line, but German stuck with me. Some of the references I still remember today. Someone's going to correct me now because I've probably bug it up. That ye ansociation anyway, that's all right, just showing off now. No, it's a sign of your character that I was unaware of, Andrew, I am curiously. I never joined Lerman at school. I never learned German at school. But when I was fourteen, I went on the school exchange to Germany, which was barbs because I wasn't studying German. But that was my first overseas visit, of course, from the United Kingdom, and so I've spent the however many years, it is sixty odd years since then trying to learn German. And yeah, yeah, look, I'm so jealous of students in countries like the United States, in the UK, in Europe because they get to do excursions to other countries. In Australia, we got to do excursions to Sydney and Canberra. I mean, come on, that was it. Yeah, that was as good as it got for us. Yeah, I mean these days they get to go to New Zealand once in a while, but yeah, we're so far from everywhere. It's just not easy. Although my son did go to get to do a couple of weeks in Japan through high school, so there are a few options these days. This is Space Nuts Andrew Dunkley here with Professor Fred Watson. Let's take a little break from the show to tell you about our sponsor in Cogni and if you've ever had your information harvested from the World Wide Web, this is the tool for you. Of course, your information is easily available online. We're talking personal information. We're talking addresses, phone numbers, email addresses, even bank details. If your protection isn't good enough, this stuff gets harvested and it is sold by data brokers. They sell it to other people who then scam you or other people in your name, which is happening a lot. I've found my information on the dark web on several occasions in recent years and managed to clean it up. But the more I clean it up, the more I have to clean it up because it just keeps going around and around and around. Chances are you regularly get those shonky emails and texts about winning something that's a common one, or your mail being lost, the package couldn't be delivered, could be anything, could be anything. 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But peace of mind is probably something that we all need in this world of data thieves, so check it out today in cogni dot com slash space nuts. Now back to the show, three based nuts. We better keep moving, Thank you, sir. Let's get a question from Gus. Hello, Professor Fred and Andrew. This is Gus Iverson from Issaquah, Washington. I sent in a question for you guys previously, and you thought I was in Western Australia. Yes, I've been thinking about gravity today and it came to my mind that if energy and mass are equivalent, then essentially shouldn't energy also create gravity at some level? I'm not sure if this is a related question or an extension or a separate question. Though. Additionally, if a body of any size is generating or it has mass and it is generating a gravitational field, does not that field itself have energy and mass? And would that field not create additional gravity by its simple existence? So if that's the case, or even kind of the case, my question is where does the energy and mass go? If or I have no idea where to go with this? Thank you. I love the show and appreciate being able to ask questions. Thank you, Gus. That sounded very much like something from Catch twenty two apples or tomatoes, I would try to I don't know, but it sounded a bit like that gravity plus energy, body plus mass plus gravity equals energy. But then does that add mass which adds to gravity. Think that's what he was trying to Yeah, that's right. So you've got to you know, the whole thing gets completely out of hand because everything's got gravity. I think. So the first part of what Jos was saying is what we've just been talking about. You know, if you nevalance have energy and mass and gravitation, you're gonna be I probably have to be careful with the words gravitational. Gravitation is a potential an object in a gravitational field has potential energy, so it does have energy. But I kind of need to take this one and notice actually did give me notice, Andrew, but I didn't have time to really look further into it. But I think I think there's a I think there's a stumbling block somewhere in that argument, which is probably that gravitational energy is an energy that's convertible to mass. But I need to get my thoughts clear on that, which they are at the moment. So Gus, thank you for a very tricky question which I might think a little bit more about. Okay, perhaps we will revisit it in a future episode of Space not Q and A. I put a put a homework market next to it. That's what I'm just doing that. I'm doing it. You're doing it in your Google. I'm using a red Google sscriber. Okay, I don't know what the German word for ready is. Probably do it translate. That's what what you are. I don't have to look at her, so Gus, don't know, We don't know. Maybe possibly could be don't yeh, but don't don't yet know. I like that. Let's to the final question. We'll get back to you Gus at some stage in Western Australia or it could be the United States. But now we've got a question from oh just by coincidence from New Zealand again high team, Amazing podcast. Which one are you talking about now? I have been listening since your early days and have always looked forward to new uploads. My question is around the discovery of early galaxies from the James web Space Telescope. Is it possible for earlier galaxies to be traveling towards us that are currently out of reach, filling with potentially nothing, filling where potentially nothing was in view before. If possible, would the light be compressed? How would the instruments deal with that? Hope that makes sense? Cheers Nick from Auckland, New Zealand. I My brain just went, well, I suppose it's possible, but how do we prove it until it happens? Yes, so couple of things in here, Thanks Nick, A great question. The last bit about light being compressed, so and in a way that's you know, that's quite a nice way of putting it. So anything that comes towards you that's emitting light, it's like, will be blue shifting. In other words, its wavelength will get shorter, and that's saying it's compressed is pretty well, you know, that's pretty well what happens. It's like, you know, the the good old ambulance siren or fire engine siren or whatever it is coming towards you, which compresses the sound waves and the result is an increase in pitch, which corresponds to a shortening of wavelength. So that's standard physics. We can detect by the Doppler shift anything coming towards us, by the fact that its light is shifted towards the blue end of the spectrum. But the first bit of the question about galaxies earlier galaxies traveling towards us. When we think about galaxies, we have two different velocities involved. One is the velocity of a galaxy as it's carried along by the expansion of the universe, and that is what we measure as a red shift. The expansion of the universe is carrying galaxies away from us, and so their light is being red shifted. And by the time you get to these really early galaxies where you're looking back almost the whole age of the universe, the red shift is very considerable. It's a fact of thirteen or fourteen something like that. We give in the name Z. The red shift is about fourteen, so a big part. No, that's not true. That's me confusing the age with the red shift. Forget that bit. But the numbers quite high. The red shifts are probably five or six or something like that. But it's still a high level of the light being stretched out by the expansion of the universe. So that's one velocity. But galaxies can have a superimposed on that, a velocity which we call a peculiar motion, its own velocity caused by local you know, local eddies in space or whatever that might move a galaxy towards us. It's the gravitational field that it's exposed to. Very much like the analog is always a river carrying you along, and if you're in a rowboat, you can move relative to the river, but the river's always carrying you along. That's exactly what's happening with the Hubble flow, the expansion of the universe, and these peculiar motions are super imposed on that, but they're much much less than the motion those distances or moot back times. It's much much less than the expansion flow of the universe. So no, there won't be anything hidden from us that's coming towards us. Think it's an interesting suggestion, but everything's moving away from us at this very high velocity at those distances. Of course, Nick, if you want to check with us in a million years or so, we might have an alternative answer. Well, that's true, put that in your diary of well, I'll mark it with a US risk, knowing that it's hard work for a million years time. Yes, it's good. I'm really disappointed that the people who make diaries haven't gone ahead that far yetbsolutely. Thanks Nick, Probably not, I think is the answer. Thanks for the question. Thanks to everyone who's sending questions. Keep them coming. You can do that via our website spacenotspodcast dot com, space nuts dot io, which has two options, the AMA tab at the top where you can send us text and audio, or the send us your questions button on the right hand side of our home screens. Don't forget to tell us who you are and where you're from, and you can probably upload your audio questions on any device as long as you've got a microphone, and mobile phones are perfect for this, but a lot of people have home computers with Mike's built in et cetera, et cetera, et cetera. Always happy to hear from you, Fred, Thanks so much. We've done with another episode. We're wrecking them up, were racking them up. Good to talk to you, Andrew, and we'll speak again too, Indeed we will. Professor Fred Watson, Astronomer at Large. And thanks to Hue in the studio for collating. Not much, but we thank him anyway. And from me Andrew Dunkley, thanks for your company. See you on the very next episode of Space Nuts. Bie spaces. You'll be listening to the Space Nuts podcast available at Apple Podcasts, Spotify, iHeart Radio, or your favorite podcast player. You can also stream on demand at bides dot com. This has been another quality podcast production from nights dot com.