Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / #434: Gravity, Energy, and Hidden Galaxies: Listener Queries Unpacked

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#434: Gravity, Energy, and Hidden Galaxies: Listener Queries Unpacked · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Hi there, This is Space Nuts Q and A. My name is Andrew
0:03
Dunkley. Great to have your company coming up. On this episode, we'll
0:06
answer questions from Steve, Gus and Nick. Steve and gusso are sort of
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focused on the same thing gravity. Steve wants to know if it can exist
0:15
without mass, and Gus is talking about gravity and energy and what's the relationship.
0:22
And Nick is asking about galaxy movements and are any moving towards us that
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we can't see yet? Well, we don't know, we can't see them
0:31
yet, but we'll see if we can tackle all of that on this episode
0:35
of Space Nuts. Fifteen seconds guidance in Channel ten nine ignition sequence Space Nuts
0:44
or three two one Space Nuts can I reported Neil Good. Here he is
0:53
again, Professor Fred. What's a hello? Fred? Hello? Hello?
0:58
How are you doing now? I'm doing the same as it was before.
1:03
How about you? Well, I'm still doing the same as it was before.
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Yes, that's right. I hope to be doing the same again very
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soon. Yes, indeed, yes, Shall we just sort of muck in
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and get these questions sorted out? It was like a couple of weeks ago
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we had gravity questions coming in thick and fast, no black hole questions,
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but today it's gravity questions. And first our first one comes from Steve.
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I go to the Steve on promm. We'll enjoy your show. Recently,
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you've read an article implying that gravity could be possible without mess, and I'm
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wondering if that would be alternative explanation two two dark matter and to wand you
2:07
have enough makes it very clearly anyway, all right, Steve, thanks for
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the question gravity without mass. Well, I doubt that we can turn to
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the Catholic Church because they do have mass, but terrible. It's an interesting
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question, though, it is. And so yeah, my reading on this,
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excuse me, is yes, that's correct. So actually there's a nice
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thread about this on Reddit if anybody looks at that website. And well I
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love Reddit, yeah really, well I do remember my one of my sons
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was an absolute Reddit fiend at one time. He was very much a Reddit
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fan. Now, so that's how I was aware of it, but I
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hadn't been a great user of Reddit. But the bottom line, excuse me,
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is, and this is the way is phrased in this particular conversation.
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If you increase the temperature of an object, and they take a planet in
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this case, and in fact, I might just read it because this kind
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of is quite interesting. Take your Neptune. You'd take your neptunean planet something
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the size of Neptune, raise the temperature by three hundred degrees calving instantly.
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Now, the massive neptune is about tenth to twenty six kilograms, and if
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we roughly assume all its hydrogen, it corresponds to about six times tenth to
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fifty two particles of hydrogen. It's the thermal energy is roughly given by an
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equation they're equal, which leads to an increase in thermal energy of deaded and
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it's a large number of duels. Actually it's a small number of duels.
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It's ok times six times tenth of minus fifty two times three hundred duels,
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which if you then convert that So what this is saying is you warm up
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a planet, you get an increase in the thermal energy of that planet.
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You can then use equals mc square to convert that thermal energy into mass,
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and in this case it comes out to be something like three times ten to
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fifteen kilograms, which is a lot, but is not very much in comparison.
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With a planet, but that does mean that adding energy to something will
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increase its gravitational mass. Now, the Steve's sort of, you know,
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next step in the argument from that is whether that could be misleading us in
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the idea of dark matter and things of that sort. And I can't really
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get my head around how that would work. He mentioned moms as well modified
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Newtonian dynamics, because my understanding is that everybody who looks at these particular problems,
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what is dark matter, what is dark energy? They take into account
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everything I've read some of the papers on this and so things like you know,
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gravitational gravitational influence of pure energy, and in this case we're talking about
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heat energy that is likely to be something that would be already in the equations.
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So I don't think it's the answer, but it's a really interesting suggestion
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and interesting thing to think about. So so thank you very much, Steve.
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Yeah, indeed just made me wonder are we increasing Earth gravity because we're
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heeding the planet up? Yep, that's probably right that I mean, the
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example that I just read out was about three hundred three hundred degrees calvin an
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instant increase in that we're talking about one or two degrees kelvin, but which
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makes a big difference to this atmosphere, but probably not that much difference to
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its gravitational potential. Okay, so the answer is yes, gravity can exist
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without mass, but it's probably not a major factor. Is that fair enough?
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Yes? That is right. I have just been dragging through my memory
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andrew something else that's sort of vaguely related to this, which is the We
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haven't this name, but we did talk about it a while ago, google
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blitz. Do you know what a google blitz is? Look, I've heard
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this before, No, remind me? Yeah? So's it? Basically is
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a black hole made of light and Wikipedia says it's a concentration of heat,
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light, or radiation so intense that its energy forms an event horizon and becomes
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self trapped. In other words, if enough radiation is aimed into a region
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of space, the concentration of energy can warp space time so much that it
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creates a black hole. It's a black hole as a black hole whose original
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mass energy was in the form of radiant energy rather than matter. Now,
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there is a paper that was published in twenty twenty four that concludes that a
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phenomenon like this cannot occur in any realistic scenario within our universe. So google
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blitz is are a theoretical entity that are not I thought not to occur in
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nature. But it is a similar thing, isn't it. Basically it's a
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it's a black hole made of energy. Yeah, wow, that's really interesting.
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I'll tell you something else that does exist is a Google scriber. So
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I've got one of those, how have you? Yeah, there is Langen
8:26
German. Hold it up, okay, google scriber, Google scriber. Yes,
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you know what German is. You know the German is for pencil.
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I probably did once, but I don't know. That's blastiff, it's probably
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I only I know did languages at high school, and I was very good
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at them, and I should have probably pursued that somewhere along the line,
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but German stuck with me. Some of the references I still remember today.
8:56
Someone's going to correct me now because I've probably bug it up. That ye
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ansociation anyway, that's all right, just showing off now. No, it's
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a sign of your character that I was unaware of, Andrew, I am
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curiously. I never joined Lerman at school. I never learned German at school.
9:18
But when I was fourteen, I went on the school exchange to Germany,
9:26
which was barbs because I wasn't studying German. But that was my first
9:30
overseas visit, of course, from the United Kingdom, and so I've spent
9:35
the however many years, it is sixty odd years since then trying to learn
9:41
German. And yeah, yeah, look, I'm so jealous of students in
9:48
countries like the United States, in the UK, in Europe because they get
9:52
to do excursions to other countries. In Australia, we got to do excursions
9:58
to Sydney and Canberra. I mean, come on, that was it.
10:03
Yeah, that was as good as it got for us. Yeah, I
10:07
mean these days they get to go to New Zealand once in a while,
10:11
but yeah, we're so far from everywhere. It's just not easy. Although
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my son did go to get to do a couple of weeks in Japan through
10:18
high school, so there are a few options these days. This is Space
10:22
Nuts Andrew Dunkley here with Professor Fred Watson. Let's take a little break from
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in cogni dot com slash space nuts. Now back to the show, three
14:00
based nuts. We better keep moving, Thank you, sir. Let's get
14:03
a question from Gus. Hello, Professor Fred and Andrew. This is Gus
14:11
Iverson from Issaquah, Washington. I sent in a question for you guys previously,
14:15
and you thought I was in Western Australia. Yes, I've been thinking
14:20
about gravity today and it came to my mind that if energy and mass are
14:28
equivalent, then essentially shouldn't energy also create gravity at some level? I'm not
14:39
sure if this is a related question or an extension or a separate question.
14:46
Though. Additionally, if a body of any size is generating or it has
14:54
mass and it is generating a gravitational field, does not that field itself have
15:05
energy and mass? And would that field not create additional gravity by its simple
15:15
existence? So if that's the case, or even kind of the case,
15:22
my question is where does the energy and mass go? If or I have
15:31
no idea where to go with this? Thank you. I love the show
15:35
and appreciate being able to ask questions. Thank you, Gus. That sounded
15:39
very much like something from Catch twenty two apples or tomatoes, I would try
15:45
to I don't know, but it sounded a bit like that gravity plus energy,
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body plus mass plus gravity equals energy. But then does that add mass
15:58
which adds to gravity. Think that's what he was trying to Yeah, that's
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right. So you've got to you know, the whole thing gets completely out
16:06
of hand because everything's got gravity. I think. So the first part of
16:11
what Jos was saying is what we've just been talking about. You know,
16:12
if you nevalance have energy and mass and gravitation, you're gonna be I probably
16:22
have to be careful with the words gravitational. Gravitation is a potential an object
16:30
in a gravitational field has potential energy, so it does have energy. But
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I kind of need to take this one and notice actually did give me notice,
16:41
Andrew, but I didn't have time to really look further into it.
16:45
But I think I think there's a I think there's a stumbling block somewhere in
16:49
that argument, which is probably that gravitational energy is an energy that's convertible to
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mass. But I need to get my thoughts clear on that, which they
17:00
are at the moment. So Gus, thank you for a very tricky question
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which I might think a little bit more about. Okay, perhaps we will
17:12
revisit it in a future episode of Space not Q and A. I put
17:18
a put a homework market next to it. That's what I'm just doing that.
17:22
I'm doing it. You're doing it in your Google. I'm using a
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red Google sscriber. Okay, I don't know what the German word for ready
17:33
is. Probably do it translate. That's what what you are. I don't
17:41
have to look at her, so Gus, don't know, We don't know.
17:47
Maybe possibly could be don't yeh, but don't don't yet know. I
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like that. Let's to the final question. We'll get back to you Gus
18:02
at some stage in Western Australia or it could be the United States. But
18:06
now we've got a question from oh just by coincidence from New Zealand again high
18:14
team, Amazing podcast. Which one are you talking about now? I have
18:17
been listening since your early days and have always looked forward to new uploads.
18:22
My question is around the discovery of early galaxies from the James web Space Telescope.
18:26
Is it possible for earlier galaxies to be traveling towards us that are currently
18:32
out of reach, filling with potentially nothing, filling where potentially nothing was in
18:41
view before. If possible, would the light be compressed? How would the
18:45
instruments deal with that? Hope that makes sense? Cheers Nick from Auckland,
18:49
New Zealand. I My brain just went, well, I suppose it's possible,
18:56
but how do we prove it until it happens? Yes, so couple
19:00
of things in here, Thanks Nick, A great question. The last bit
19:03
about light being compressed, so and in a way that's you know, that's
19:10
quite a nice way of putting it. So anything that comes towards you that's
19:12
emitting light, it's like, will be blue shifting. In other words,
19:18
its wavelength will get shorter, and that's saying it's compressed is pretty well,
19:23
you know, that's pretty well what happens. It's like, you know,
19:27
the the good old ambulance siren or fire engine siren or whatever it is coming
19:33
towards you, which compresses the sound waves and the result is an increase in
19:37
pitch, which corresponds to a shortening of wavelength. So that's standard physics.
19:42
We can detect by the Doppler shift anything coming towards us, by the fact
19:48
that its light is shifted towards the blue end of the spectrum. But the
19:56
first bit of the question about galaxies earlier galaxies traveling towards us. When we
20:07
think about galaxies, we have two different velocities involved. One is the velocity
20:15
of a galaxy as it's carried along by the expansion of the universe, and
20:21
that is what we measure as a red shift. The expansion of the universe
20:25
is carrying galaxies away from us, and so their light is being red shifted.
20:30
And by the time you get to these really early galaxies where you're looking
20:34
back almost the whole age of the universe, the red shift is very considerable.
20:40
It's a fact of thirteen or fourteen something like that. We give in
20:42
the name Z. The red shift is about fourteen, so a big part.
20:48
No, that's not true. That's me confusing the age with the red
20:52
shift. Forget that bit. But the numbers quite high. The red shifts
20:56
are probably five or six or something like that. But it's still a high
21:02
level of the light being stretched out by the expansion of the universe. So
21:06
that's one velocity. But galaxies can have a superimposed on that, a velocity
21:12
which we call a peculiar motion, its own velocity caused by local you know,
21:18
local eddies in space or whatever that might move a galaxy towards us.
21:23
It's the gravitational field that it's exposed to. Very much like the analog is
21:30
always a river carrying you along, and if you're in a rowboat, you
21:33
can move relative to the river, but the river's always carrying you along.
21:37
That's exactly what's happening with the Hubble flow, the expansion of the universe,
21:41
and these peculiar motions are super imposed on that, but they're much much less
21:45
than the motion those distances or moot back times. It's much much less than
21:52
the expansion flow of the universe. So no, there won't be anything hidden
21:57
from us that's coming towards us. Think it's an interesting suggestion, but everything's
22:03
moving away from us at this very high velocity at those distances. Of course,
22:08
Nick, if you want to check with us in a million years or
22:11
so, we might have an alternative answer. Well, that's true, put
22:15
that in your diary of well, I'll mark it with a US risk,
22:18
knowing that it's hard work for a million years time. Yes, it's good.
22:26
I'm really disappointed that the people who make diaries haven't gone ahead that far
22:29
yetbsolutely. Thanks Nick, Probably not, I think is the answer. Thanks
22:38
for the question. Thanks to everyone who's sending questions. Keep them coming.
22:41
You can do that via our website spacenotspodcast dot com, space nuts dot io,
22:47
which has two options, the AMA tab at the top where you can
22:51
send us text and audio, or the send us your questions button on the
22:56
right hand side of our home screens. Don't forget to tell us who you
22:59
are and where you're from, and you can probably upload your audio questions on
23:03
any device as long as you've got a microphone, and mobile phones are perfect
23:07
for this, but a lot of people have home computers with Mike's built in
23:11
et cetera, et cetera, et cetera. Always happy to hear from you,
23:15
Fred, Thanks so much. We've done with another episode. We're wrecking
23:18
them up, were racking them up. Good to talk to you, Andrew,
23:22
and we'll speak again too, Indeed we will. Professor Fred Watson,
23:26
Astronomer at Large. And thanks to Hue in the studio for collating. Not
23:32
much, but we thank him anyway. And from me Andrew Dunkley, thanks
23:34
for your company. See you on the very next episode of Space Nuts.
23:38
Bie spaces. You'll be listening to the Space Nuts podcast available at Apple Podcasts,
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