Gravity Questions, Cosmic Energy & Hidden Galaxies

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Andrew Dunkley: Hi there, this is Space Nuts. Q and A. My

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name is Andrew Dunkley. Great to have your

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company. Coming up on this episode, we'll

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answer questions from Steve, Gus and Nick.

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Uh, Steve and Gus are sort of focused on the

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same thing, gravity.

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Steve, uh, wants to know if it can exist

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without mass. Uh, and Gus is talking

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about gravity and energy and what's the

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relationship. And Nick is asking about

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galaxy, um, movements and are any moving

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towards us that we can't see yet?

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Well, we don't know we can't see them yet.

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Uh, but we'll see if we can tackle all of

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that on this episode of space

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nuts.

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Generic: 15 seconds. Guidance is internal.

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10, 9. Ignition

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sequence start. Space nuts. 5, 4, 3,

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2. 1, 2, 3, 4, 5, 5, 4,

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3, 2, 1. Space nuts. Astronauts

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report it feels good.

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Andrew Dunkley: Here he is again, Professor Fred Watson.

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Hello, Fred.

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Professor Fred Watson: Hello Andrew. Hello. How are you doing now?

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Andrew Dunkley: I'm doing the same as I was before.

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How about you?

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Professor Fred Watson: Uh, well, I'm still doing the same as I was

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before. Yes, that's right. And I hope to be

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doing the same again very soon.

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Andrew Dunkley: Yes, indeed, yes. Uh, shall

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we just sort of muck in and get

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these questions sorted out?

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It was ah, like a couple of weeks ago we had

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um, gravity questions coming in thick and

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fast. Uh, no black hole questions. But today

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it's gravity questions.

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Professor Fred Watson: It is.

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Andrew Dunkley: And our first one comes from

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Steve.

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Steve: Hi guys, my name is Steve. I'm uh, from New

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Zealand. Um, really enjoy your show.

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Recently read a article

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implying that, uh, gravity

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could be possible without mass.

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And um, I'm wondering if that would

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be, uh, another alternative

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explanation to um,

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uh, dark matter and to

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Mond.

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Yeah, I don't know if that makes it very

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clear to you. Anyway, thanks.

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Andrew Dunkley: All right, uh, Steve, thanks for the

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question, gravity without mass.

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Well, I doubt that, uh, we can turn to the

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Catholic Church because they do have mass.

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Um, but,

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uh, terrible. Uh, it's an interesting

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question though.

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Professor Fred Watson: It is. And um, so

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yeah, my reading on this. Excuse me, is

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yes, um, that's correct.

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So, uh, actually there's a nice

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thread about this on Reddit if anybody looks

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at that website.

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Andrew Dunkley: I do.

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Professor Fred Watson: And um, well, I love Reddit. Yeah,

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really Well, I do remember my, uh, one of my

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sons was an absolute Reddit fiend at one

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time. He was very much, um,

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a Reddit fan. Uh, now, so

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that's how I was aware of it. But I haven't

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been a great user of Reddit. But the bottom

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line. Excuse me, is, um,

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and this is the way it's phrased in this

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Particular conversation. If you increase

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the temperature of

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an object and they take a planet, in this

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case, uh, and in fact I might just

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read it, uh, because this kind of is

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quite interesting.

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Um,

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take your Neptunian planet, something the

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size of Neptune, raise the temperature by 300

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degrees Kelvin instantly. Now, the mass

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of neptune is about 10 to the 26 kg.

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And if we roughly assume all its hydrogen,

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uh, corresponds uh, to about 6 times 10

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to the 52 particles of hydrogen. Uh,

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the thermal energy is roughly given by

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an uh, equation. There equals nkt, uh,

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uh, which leads to an increase in thermal

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energy, uh, of

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deh.

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Gus: Duh.

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Professor Fred Watson: Uh, and it's a large number of

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joules. Um, actually it's a small number

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of joules. It's k times 6

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times 10 to the minus 52 times 300

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Joules, which

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um, if you then convert that.

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So what this is saying is you warm up a

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planet, you get an increase, uh, in the

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thermal energy of that planet. You can then

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use E equals MC squared to convert that

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thermal energy into mass. And in this case it

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comes out to be something like 3 times 10 to

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the 15 kilogram is a lot,

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but, uh, is not

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very much in comparison with a planet. Uh,

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but that does mean that adding energy

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to something will increase its gravitational

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mass. Now, um,

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Steve's sort of, uh, you know,

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um, next step in the argument from that is

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whether that could be misleading us in the

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idea of dark matter and things of that sort

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of. Um. And uh,

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I can't really get my head around how

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that would work. Um, he mentioned MOND

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as well modified Newtonian dynamics.

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Um, because my understanding

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is that everybody who looks at these

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particular problems, what is dark matter?

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What is dark energy, they take into account

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everything. Uh, I've um, read some of the

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papers on this and so things like,

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um, uh,

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gravitational influence of

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pure energy. And in this case we're talking

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about heat energy. That

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uh, is likely to be something that would

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be already in the equations. Um, so I don't

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think it's the answer, but it's a really

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interesting suggestion and an interesting

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thing to think about. Uh, thank

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you very much, Steve.

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Andrew Dunkley: Yeah, indeed. Just, um, made me wonder. Are

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we increasing Earth's gravity because we're

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heating the planet up?

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Professor Fred Watson: Yep, that's probably right. Um,

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I mean the example that uh, I just read out

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was about

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300 degrees Kelvin, an instant increase, uh,

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in that we're talking about one or two

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degrees Kelvin, uh, uh,

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which makes a big difference to the Earth's

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atmosphere, but probably not that much

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difference to its uh, you know, gravitational

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potential.

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Andrew Dunkley: Okay, M. So the answer is yes. Gravity can

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exist without mass, but

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it's probably not a major factor. Is that

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fair enough?

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Professor Fred Watson: Uh, yes, that is right.

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Um, I've, uh, just been dragging through my

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memory, Andrew, something else that's sort

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of vaguely related to this.

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Um, which is the. Well, we haven't

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used this name, but we did talk about it a

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while ago. Kugelblitz.

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Do you know what a Kugelblitz is?

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Andrew Dunkley: Uh, look, I've heard this before.

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Uh, no, remind me.

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Professor Fred Watson: Yeah. So it basically is,

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uh, a black hole made of light. Uh,

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and Wikipedia says it's a concentration of

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heat, light, or radiation so intense that its

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energy forms an event horizon and becomes

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self trapped. In other words, if enough

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radiation is aimed into a region of space,

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the concentration of energy can warp space

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time so much that it creates a black hole.

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It's a black hole as a black hole whose

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original mass energy was in the form of

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radiant energy rather than matter.

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Uh, now, um, there is a

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paper that was published in

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2024 that concludes

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that a phenomenon like this cannot occur in

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any realistic scenario within our universe.

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So kugelblitzes, uh, are a theoretical

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entity that are not thought not

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to occur in nature. Uh, but it

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is a similar thing, isn't it? So it

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basically. It's a black hole made of energy.

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Andrew Dunkley: Yeah. Wow, that's really interesting. I'll

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tell you something else that does exist is a

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Kugel scriber. So

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I've got one of those.

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Professor Fred Watson: Have you?

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Andrew Dunkley: Yeah. There it is.

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Professor Fred Watson: Mangle.

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Andrew Dunkley: It's a pen. It's German looking.

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Professor Fred Watson: Hold it up. Ah, okay.

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Andrew Dunkley: Google scriber.

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Professor Fred Watson: Kugel scriber, yes.

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Andrew Dunkley: You know what German is? Uh. You know what

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the German is for pencil?

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Professor Fred Watson: Uh, I probably did once, but I don't know.

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All right. Uh, it's probably.

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I only.

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Andrew Dunkley: I did languages at high school, and I was

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very good at them. And I should have probably

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pursued that somewhere along the line, but

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German stuck with me.

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Professor Fred Watson: I.

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Andrew Dunkley: Some of the references I still remember

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today. Someone's going to correct me now

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because I probably buggered up the, uh,

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pronunciation anyway.

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Professor Fred Watson: That's all right.

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Andrew Dunkley: I'm just showing off now.

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Professor Fred Watson: No, ah, it's a side of your character that I

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was unaware of, Andrew. Um,

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curiously, I, uh,

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never joined Lerman at school. I

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never learned Sherman at school. Um,

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but, uh, uh, when I was 14,

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uh, I went on a school exchange to

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Germany, which was Barbara, because I wasn't

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studying German. But that was my first

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overseas visit, of course, from the United

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Kingdom. Um, and so I've

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spent the. However many years it

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is, 60 odd years since then

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trying to learn German and.

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Andrew Dunkley: Yeah, yeah, look, I'm so

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jealous of students in countries like the

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United States and the UK and Europe because

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they get to do excursions to other countries.

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In Australia, we got to do excursions to

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Sydney and Canberra. I mean, come on.

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That was it. Yeah, that was as good as it

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got for us. Yeah, I mean, these days they get

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to go to New Zealand once in a while. Um,

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but yeah, we're so far from everywhere. It's

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just not easy. Although my son did go to get

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to do a couple of weeks in Japan through high

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school.

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Professor Fred Watson: So there you go.

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Andrew Dunkley: There are a few options these days. This is

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Space Nuts. Andrew Dunkley here with

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Professor Fred Watson.

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Generic: Three, two, one.

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Andrew Dunkley: Space Nuts. Uh, we better keep moving. Uh,

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thank you, Steve.

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Let's get a question from Gus.

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Gus: Hello, Professor Fred and uh, Andrew.

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Uh, this is Gus Iverson from Issaquah,

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Washington. I sent in a question for you guys

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previously and you thought I was in Western

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Australia. Yes, I, I've been thinking about,

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um, gravity, uh,

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today. And it, it came to my mind that

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if, uh, energy and mass

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are equivalent, then essentially,

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uh, shouldn't energy also create

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gravity at some level?

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Um, I'm not sure if this is a related

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question or an extension or

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a separate question though. Um, uh,

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additionally, um, if a

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body of any size is

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generating or has mass

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and it is generating a

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gravitational field, does

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not that field itself

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have energy and mass?

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And would that field not

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create additional gravity

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by its simple existence?

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So if that's the case,

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or even kind of the case, my question is,

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where does the energy and mass go? If,

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um, or, um.

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I have no idea where to go with this.

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Professor Fred Watson: Thank you.

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Gus: Uh, I love the show and, uh, appreciate being

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able to ask questions.

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Andrew Dunkley: Thank you, Gus. Uh, that sounded very much

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like something from catch 22.

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Was it apples or tomatoes? They were trying

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to. I don't know. Um,

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but, uh, yeah, it sounded a bit like that.

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Um, gravity plus energy, body plus

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mass plus gravity equals energy. But

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then does that add mass which adds to

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gravity? I think that's what he was trying

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to.

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Professor Fred Watson: Yeah, that's right. So, so you've got a. You

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know, the whole thing gets completely out of

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hand because everything's got gravity. Um,

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I think, uh, so the first part of what Gus

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was saying is what we've just been talking

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about. You know, if you have energy and

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mass, um, and

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gravitation, you probably have to

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be careful with the words.

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Gravitation is a Potential.

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Uh, an object in a gravitational field has

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potential energy, so it does have energy.

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Uh, but

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I kind of need to take this one and notice.

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Actually, you did give me notice, Andrew, but

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I didn't have time to really look further

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into it.

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Andrew Dunkley: But.

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Professor Fred Watson: I think there's a stumbling block somewhere

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in that argument, uh, which is probably that

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gravitational energy isn't energy. That's

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convertible to mass. Um, but I

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need to get my thoughts clearer on that,

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which they aren't at the moment. So, Gus,

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thank you for a very, uh, tricky question,

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uh, which, um, I might think a little bit

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more about. Uh, and,

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uh, perhaps we will revisit it in a future

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episode of Spacenuts. Q and A.

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Andrew Dunkley: Um, I put a, uh, homework marker next to it.

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Professor Fred Watson: That's what I. I'm just doing that. I'm doing

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it. You're doing it in your, uh, kugel.

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Andrew Dunkley: I'm using a red Kugel scriber.

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Professor Fred Watson: Okay.

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Andrew Dunkley: I don't know what the German word for red is,

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though.

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Professor Fred Watson: Oh.

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Andrew Dunkley: Probably do it on translator.

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Professor Fred Watson: Uh.

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Andrew Dunkley: Ah, there you are.

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Professor Fred Watson: Yeah, there you are.

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Andrew Dunkley: I don't have to look it up.

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Professor Fred Watson: You do.

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Andrew Dunkley: So, Gus, um, dunno. We don't know.

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Maybe. Possibly. Could be.

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Professor Fred Watson: Don't know. Yeah, but we'll. How's

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that?

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Andrew Dunkley: Don't yet know.

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I like that.

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Professor Fred Watson: Yeah.

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Andrew Dunkley: Uh, let's, um, get to the final question.

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We'll get back to you, Gus. At some stage in

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Western Australia, or it could be the United

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States.

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Uh, now we've got a question from. Oh,

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um, just by coincidence, from New Zealand

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again. Um, hi, Tim. Amazing

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podcast. Which one are you talking about now?

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Uh, I have been listening since your early

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days and have always, uh, looked forward to

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new, uh, uploads. My question is around the

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discovery of early galaxies from the James

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Webb Space Telescope. Is it possible for

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earlier galaxies to be traveling towards us

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that are currently out of reach? Uh, filling

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with potentially, uh, nothing. Uh,

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filling where potentially nothing was in view

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before. Uh, if possible, would the light be

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compressed? How would the instruments deal

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with that? Hope that makes sense. Cheers.

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Nick from Auckland, New Zealand.

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My brain just went, well, I suppose it's

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possible, but how do we prove it until it

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happens?

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Professor Fred Watson: Yes. So, a. Ah, couple of things in here. Um,

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thanks, Nick. Great question. The last bit

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about light being compressed, um,

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and in a way, that's, um, quite

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a nice way of putting it. So anything that

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comes towards you that's emitting light,

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its light will be blue shifted. In other

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words, its wavelength will get

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shorter. And that's saying

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it's compressed is pretty well you know,

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that's pretty well what happens. It's like,

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uh, um, you know, the good old

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ambulance, uh, siren or fire engine siren or

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whatever it is coming towards you, uh, which

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compresses the sound waves. And the

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result is an increase in pitch. Which

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corresponds to a shortening of wavelength. So

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that's standard physics. We can detect,

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uh, by the Doppler shift, anything coming

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towards us. Uh, by the fact that its light is

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shifted towards the blue end of the spectrum.

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Um, but, um, the

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first bit of the question about galaxies,

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earlier galaxies traveling towards us.

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Andrew Dunkley: Um.

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Professor Fred Watson: When we think about galaxies, we have

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two different velocities involved. One

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is the velocity of a galaxy as it's

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carried along by the expansion of the

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universe. Uh, and that is

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what we measure as a redshift. Uh,

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the expansion of the universe is carrying

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galaxies away from us. And so their light is

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being redshifted. Uh, and by the

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time you get to these really early galaxies

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where you're looking back, uh, almost the

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whole edge of the universe, the redshift is

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very considerable. It's a factor of 13 or 14,

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something like that. We're giving the name Z.

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Uh, the redshift is about 14. So,

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um. I beg your pardon. No, that's not true.

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Uh, that's me confusing the age

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with the redshift. Forget that bit. But

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the number's quite high. The redshifts are

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probably five or six or something like that.

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But, uh, it's still a high level of

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the light being stretched out by the

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expansion of the universe. So that's one

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velocity. But galaxies can have

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superimposed on that a velocity which we call

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a peculiar motion. Its own velocity, uh,

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caused by local eddies in

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space or whatever. Uh, that. That might,

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um, move a galaxy towards us. It's the

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gravitational field that it's exposed

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to. Very much like the

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analog is always a river carrying you along.

421
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Uh, and if you're in a rowboat, you can move

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relative to the river. But the river's always

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carrying you along. That's exactly what's

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happening with the Hubble flow, the expansion

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of the universe. And these peculiar motions

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are superimposed on that. But they're much,

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much less than the motion,

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uh, those distances, uh, or look

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back times. It's much, much less than the

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expansion flow of the universe. So no, there

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won't be anything hidden from us that's

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coming towards us. I don't think it's an

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00:18:32.560 --> 00:18:34.880
interesting suggestion. But, uh, uh,

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everything's moving away from us at this very

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high velocity. At those distances, M

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of Course.

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Andrew Dunkley: Um, Nick, if you want to check with us, uh,

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in a million years or so, we might have an

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alternative answer.

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Professor Fred Watson: Well, that's true. Uh, put that in your diary

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and, uh, I'll mark it with an

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asterisk, knowing that it's work for a

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00:18:52.300 --> 00:18:54.620
million years time. Yes,

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it's good.

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Andrew Dunkley: Um, I'm really disappointed that the people

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who make diaries haven't gone ahead that far

447
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yet.

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Thanks, Nick. Um, probably not, I think, is

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the answer. Um, but thanks for the

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question. Thanks to everyone who sent in

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questions. Keep them coming. You can do that

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00:19:14.980 --> 00:19:17.180
via our, ah, website spacenutspodcast.com

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00:19:17.180 --> 00:19:20.180
spacenuts IO which, uh, has two

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00:19:20.180 --> 00:19:23.060
options. The AMA tab at the top where you can

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00:19:23.060 --> 00:19:25.960
send us text audio or the send us your

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00:19:25.960 --> 00:19:28.480
questions, um, button on the right hand side

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00:19:28.480 --> 00:19:30.960
of our home screen. Don't forget to tell us

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00:19:30.960 --> 00:19:32.880
who you are and where you're from. And you

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00:19:32.880 --> 00:19:35.240
can probably upload your audio questions on

460
00:19:35.240 --> 00:19:36.640
any device as long as you've got a

461
00:19:36.640 --> 00:19:39.360
microphone. Mobile phones are perfect for

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00:19:39.360 --> 00:19:42.120
this. Um, but, um, a lot of people have home

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computers with mics built in, et cetera, et

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00:19:44.160 --> 00:19:46.560
cetera, et cetera. Always happy to hear from

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you. Um, Fred, thanks so much. We're done

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with another episode. Geez. We're wrapping

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them up.

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Professor Fred Watson: We are racking him up. Good to talk to you,

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Andrew. And we'll speak again soon.

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Andrew Dunkley: Indeed we will. Professor Fred Watson,

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astronomer at large. And thanks to Huw in the

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studio for collating.

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Not much, but, uh, we thank him anyway. And

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00:20:06.190 --> 00:20:07.949
from me, Andrew Dunkley, thanks for your

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00:20:07.949 --> 00:20:10.150
company. See you on the very next episode of

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00:20:10.150 --> 00:20:11.710
Space Nuts. Bye bye.

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00:20:12.830 --> 00:20:15.030
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