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This episode originally aired in 2024.
Cosmic Q&A: Gravity, Energy, and Hidden Galaxies
In this thought-provoking holiday repeat episode of Space Nuts, hosts Andrew Dunkley and Professor Fred Watson dive into listener questions that explore the intricate relationships between gravity, energy, and the cosmos. With inquiries from Steve, Gus, and Nick, the discussion spans the nature of gravity, the implications of energy on gravitational fields, and the mysteries of galaxy movements.
Episode Highlights:
- Gravity Without Mass: Steve from New Zealand poses a fascinating question about the possibility of gravity existing without mass. Andrew and Fred discuss the theoretical implications and whether energy can contribute to gravitational effects, referencing concepts like thermal energy and dark matter.
- Energy and Gravity: Gus from Jessica, Washington, raises an intriguing point about the equivalence of mass and energy and its relationship to gravity. The hosts navigate the complexities of gravitational energy and ponder whether the energy of gravitational fields could influence mass.
- Hidden Galaxies: Nick from Auckland, New Zealand, wonders if there are early galaxies moving towards us that we can't yet see. The discussion delves into the concepts of redshift and peculiar motion, clarifying how the expansion of the universe affects our observations of distant galaxies.
- Listener Engagement: The episode wraps up with Andrew and Fred encouraging listeners to keep sending in their questions, fostering a sense of community and curiosity about the universe.
For more Space Nuts, including our continuously updating newsfeed and to listen to all our episodes, visit our website. Follow us on social media at SpaceNutsPod on Facebook, X, YouTube Music Music, Tumblr, Instagram, and TikTok. We love engaging with our community, so be sure to drop us a message or comment on your favorite platform.
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Stay curious, keep looking up, and join us next time for more stellar insights and cosmic wonders. Until then, clear skies and happy stargazing.
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00:00:00 --> 00:00:02 Andrew Dunkley: Hi there, this is Space Nuts. Q and A. My
00:00:02 --> 00:00:04 name is Andrew Dunkley. Great to have your
00:00:04 --> 00:00:06 company. Coming up on this episode, we'll
00:00:06 --> 00:00:08 answer questions from Steve, Gus and Nick.
00:00:08 --> 00:00:11 Uh, Steve and Gus are sort of focused on the
00:00:11 --> 00:00:13 same thing, gravity.
00:00:13 --> 00:00:15 Steve, uh, wants to know if it can exist
00:00:15 --> 00:00:18 without mass. Uh, and Gus is talking
00:00:18 --> 00:00:21 about gravity and energy and what's the
00:00:21 --> 00:00:23 relationship. And Nick is asking about
00:00:24 --> 00:00:26 galaxy, um, movements and are any moving
00:00:26 --> 00:00:28 towards us that we can't see yet?
00:00:29 --> 00:00:31 Well, we don't know we can't see them yet.
00:00:31 --> 00:00:33 Uh, but we'll see if we can tackle all of
00:00:33 --> 00:00:35 that on this episode of space
00:00:35 --> 00:00:36 nuts.
00:00:36 --> 00:00:39 Generic: 15 seconds. Guidance is internal.
00:00:39 --> 00:00:41 10, 9. Ignition
00:00:41 --> 00:00:44 sequence start. Space nuts. 5, 4, 3,
00:00:45 --> 00:00:47 2. 1, 2, 3, 4, 5, 5, 4,
00:00:47 --> 00:00:50 3, 2, 1. Space nuts. Astronauts
00:00:50 --> 00:00:52 report it feels good.
00:00:52 --> 00:00:55 Andrew Dunkley: Here he is again, Professor Fred Watson.
00:00:55 --> 00:00:55 Hello, Fred.
00:00:56 --> 00:00:59 Professor Fred Watson: Hello Andrew. Hello. How are you doing now?
00:01:00 --> 00:01:02 Andrew Dunkley: I'm doing the same as I was before.
00:01:03 --> 00:01:04 How about you?
00:01:05 --> 00:01:07 Professor Fred Watson: Uh, well, I'm still doing the same as I was
00:01:07 --> 00:01:10 before. Yes, that's right. And I hope to be
00:01:10 --> 00:01:12 doing the same again very soon.
00:01:12 --> 00:01:15 Andrew Dunkley: Yes, indeed, yes. Uh, shall
00:01:15 --> 00:01:18 we just sort of muck in and get
00:01:18 --> 00:01:19 these questions sorted out?
00:01:21 --> 00:01:24 It was ah, like a couple of weeks ago we had
00:01:24 --> 00:01:27 um, gravity questions coming in thick and
00:01:27 --> 00:01:29 fast. Uh, no black hole questions. But today
00:01:29 --> 00:01:30 it's gravity questions.
00:01:30 --> 00:01:31 Professor Fred Watson: It is.
00:01:31 --> 00:01:33 Andrew Dunkley: And our first one comes from
00:01:34 --> 00:01:34 Steve.
00:01:35 --> 00:01:38 Steve: Hi guys, my name is Steve. I'm uh, from New
00:01:38 --> 00:01:41 Zealand. Um, really enjoy your show.
00:01:42 --> 00:01:45 Recently read a article
00:01:46 --> 00:01:49 implying that, uh, gravity
00:01:50 --> 00:01:51 could be possible without mass.
00:01:53 --> 00:01:56 And um, I'm wondering if that would
00:01:56 --> 00:01:58 be, uh, another alternative
00:01:58 --> 00:02:00 explanation to um,
00:02:02 --> 00:02:04 uh, dark matter and to
00:02:04 --> 00:02:05 Mond.
00:02:07 --> 00:02:09 Yeah, I don't know if that makes it very
00:02:09 --> 00:02:10 clear to you. Anyway, thanks.
00:02:11 --> 00:02:12 Andrew Dunkley: All right, uh, Steve, thanks for the
00:02:12 --> 00:02:15 question, gravity without mass.
00:02:15 --> 00:02:18 Well, I doubt that, uh, we can turn to the
00:02:18 --> 00:02:21 Catholic Church because they do have mass.
00:02:22 --> 00:02:22 Um, but,
00:02:26 --> 00:02:28 uh, terrible. Uh, it's an interesting
00:02:28 --> 00:02:29 question though.
00:02:30 --> 00:02:33 Professor Fred Watson: It is. And um, so
00:02:33 --> 00:02:35 yeah, my reading on this. Excuse me, is
00:02:36 --> 00:02:39 yes, um, that's correct.
00:02:39 --> 00:02:42 So, uh, actually there's a nice
00:02:42 --> 00:02:44 thread about this on Reddit if anybody looks
00:02:44 --> 00:02:45 at that website.
00:02:46 --> 00:02:47 Andrew Dunkley: I do.
00:02:47 --> 00:02:50 Professor Fred Watson: And um, well, I love Reddit. Yeah,
00:02:52 --> 00:02:54 really Well, I do remember my, uh, one of my
00:02:54 --> 00:02:57 sons was an absolute Reddit fiend at one
00:02:57 --> 00:02:59 time. He was very much, um,
00:03:00 --> 00:03:03 a Reddit fan. Uh, now, so
00:03:03 --> 00:03:05 that's how I was aware of it. But I haven't
00:03:05 --> 00:03:08 been a great user of Reddit. But the bottom
00:03:08 --> 00:03:11 line. Excuse me, is, um,
00:03:12 --> 00:03:15 and this is the way it's phrased in this
00:03:15 --> 00:03:18 Particular conversation. If you increase
00:03:18 --> 00:03:21 the temperature of
00:03:21 --> 00:03:24 an object and they take a planet, in this
00:03:24 --> 00:03:27 case, uh, and in fact I might just
00:03:27 --> 00:03:29 read it, uh, because this kind of is
00:03:30 --> 00:03:31 quite interesting.
00:03:31 --> 00:03:34 Um,
00:03:35 --> 00:03:37 take your Neptunian planet, something the
00:03:37 --> 00:03:40 size of Neptune, raise the temperature by 300
00:03:40 --> 00:03:43 degrees Kelvin instantly. Now, the mass
00:03:43 --> 00:03:46 of neptune is about 10 to the 26 kg.
00:03:46 --> 00:03:48 And if we roughly assume all its hydrogen,
00:03:48 --> 00:03:51 uh, corresponds uh, to about 6 times 10
00:03:51 --> 00:03:54 to the 52 particles of hydrogen. Uh,
00:03:54 --> 00:03:57 the thermal energy is roughly given by
00:03:58 --> 00:04:01 an uh, equation. There equals nkt, uh,
00:04:01 --> 00:04:04 uh, which leads to an increase in thermal
00:04:04 --> 00:04:06 energy, uh, of
00:04:07 --> 00:04:07 deh.
00:04:07 --> 00:04:07 Gus: Duh.
00:04:07 --> 00:04:10 Professor Fred Watson: Uh, and it's a large number of
00:04:10 --> 00:04:13 joules. Um, actually it's a small number
00:04:13 --> 00:04:16 of joules. It's k times 6
00:04:16 --> 00:04:18 times 10 to the minus 52 times 300
00:04:18 --> 00:04:21 Joules, which
00:04:21 --> 00:04:24 um, if you then convert that.
00:04:24 --> 00:04:27 So what this is saying is you warm up a
00:04:27 --> 00:04:30 planet, you get an increase, uh, in the
00:04:30 --> 00:04:33 thermal energy of that planet. You can then
00:04:33 --> 00:04:35 use E equals MC squared to convert that
00:04:35 --> 00:04:38 thermal energy into mass. And in this case it
00:04:38 --> 00:04:41 comes out to be something like 3 times 10 to
00:04:41 --> 00:04:44 the 15 kilogram is a lot,
00:04:44 --> 00:04:47 but, uh, is not
00:04:47 --> 00:04:49 very much in comparison with a planet. Uh,
00:04:50 --> 00:04:52 but that does mean that adding energy
00:04:53 --> 00:04:55 to something will increase its gravitational
00:04:55 --> 00:04:58 mass. Now, um,
00:04:59 --> 00:05:02 Steve's sort of, uh, you know,
00:05:03 --> 00:05:05 um, next step in the argument from that is
00:05:05 --> 00:05:08 whether that could be misleading us in the
00:05:08 --> 00:05:10 idea of dark matter and things of that sort
00:05:10 --> 00:05:12 of. Um. And uh,
00:05:13 --> 00:05:16 I can't really get my head around how
00:05:16 --> 00:05:18 that would work. Um, he mentioned MOND
00:05:18 --> 00:05:21 as well modified Newtonian dynamics.
00:05:21 --> 00:05:24 Um, because my understanding
00:05:24 --> 00:05:26 is that everybody who looks at these
00:05:28 --> 00:05:30 particular problems, what is dark matter?
00:05:30 --> 00:05:32 What is dark energy, they take into account
00:05:33 --> 00:05:35 everything. Uh, I've um, read some of the
00:05:35 --> 00:05:38 papers on this and so things like,
00:05:39 --> 00:05:41 um, uh,
00:05:41 --> 00:05:44 gravitational influence of
00:05:45 --> 00:05:47 pure energy. And in this case we're talking
00:05:47 --> 00:05:49 about heat energy. That
00:05:50 --> 00:05:53 uh, is likely to be something that would
00:05:53 --> 00:05:55 be already in the equations. Um, so I don't
00:05:55 --> 00:05:57 think it's the answer, but it's a really
00:05:57 --> 00:06:00 interesting suggestion and an interesting
00:06:00 --> 00:06:03 thing to think about. Uh, thank
00:06:03 --> 00:06:03 you very much, Steve.
00:06:04 --> 00:06:07 Andrew Dunkley: Yeah, indeed. Just, um, made me wonder. Are
00:06:07 --> 00:06:09 we increasing Earth's gravity because we're
00:06:09 --> 00:06:10 heating the planet up?
00:06:11 --> 00:06:13 Professor Fred Watson: Yep, that's probably right. Um,
00:06:14 --> 00:06:17 I mean the example that uh, I just read out
00:06:17 --> 00:06:18 was about
00:06:20 --> 00:06:23 300 degrees Kelvin, an instant increase, uh,
00:06:23 --> 00:06:26 in that we're talking about one or two
00:06:26 --> 00:06:29 degrees Kelvin, uh, uh,
00:06:29 --> 00:06:30 which makes a big difference to the Earth's
00:06:30 --> 00:06:32 atmosphere, but probably not that much
00:06:32 --> 00:06:34 difference to its uh, you know, gravitational
00:06:34 --> 00:06:35 potential.
00:06:36 --> 00:06:38 Andrew Dunkley: Okay, M. So the answer is yes. Gravity can
00:06:38 --> 00:06:40 exist without mass, but
00:06:41 --> 00:06:44 it's probably not a major factor. Is that
00:06:45 --> 00:06:45 fair enough?
00:06:46 --> 00:06:48 Professor Fred Watson: Uh, yes, that is right.
00:06:49 --> 00:06:51 Um, I've, uh, just been dragging through my
00:06:51 --> 00:06:54 memory, Andrew, something else that's sort
00:06:54 --> 00:06:56 of vaguely related to this.
00:06:56 --> 00:06:59 Um, which is the. Well, we haven't
00:06:59 --> 00:07:01 used this name, but we did talk about it a
00:07:01 --> 00:07:03 while ago. Kugelblitz.
00:07:04 --> 00:07:06 Do you know what a Kugelblitz is?
00:07:06 --> 00:07:08 Andrew Dunkley: Uh, look, I've heard this before.
00:07:09 --> 00:07:11 Uh, no, remind me.
00:07:11 --> 00:07:14 Professor Fred Watson: Yeah. So it basically is,
00:07:14 --> 00:07:17 uh, a black hole made of light. Uh,
00:07:18 --> 00:07:20 and Wikipedia says it's a concentration of
00:07:20 --> 00:07:22 heat, light, or radiation so intense that its
00:07:22 --> 00:07:24 energy forms an event horizon and becomes
00:07:24 --> 00:07:27 self trapped. In other words, if enough
00:07:27 --> 00:07:29 radiation is aimed into a region of space,
00:07:29 --> 00:07:32 the concentration of energy can warp space
00:07:32 --> 00:07:34 time so much that it creates a black hole.
00:07:35 --> 00:07:38 It's a black hole as a black hole whose
00:07:38 --> 00:07:40 original mass energy was in the form of
00:07:40 --> 00:07:42 radiant energy rather than matter.
00:07:43 --> 00:07:45 Uh, now, um, there is a
00:07:46 --> 00:07:48 paper that was published in
00:07:48 --> 00:07:51 2024 that concludes
00:07:52 --> 00:07:54 that a phenomenon like this cannot occur in
00:07:54 --> 00:07:57 any realistic scenario within our universe.
00:07:58 --> 00:08:00 So kugelblitzes, uh, are a theoretical
00:08:00 --> 00:08:03 entity that are not thought not
00:08:03 --> 00:08:06 to occur in nature. Uh, but it
00:08:06 --> 00:08:08 is a similar thing, isn't it? So it
00:08:08 --> 00:08:10 basically. It's a black hole made of energy.
00:08:11 --> 00:08:14 Andrew Dunkley: Yeah. Wow, that's really interesting. I'll
00:08:14 --> 00:08:16 tell you something else that does exist is a
00:08:16 --> 00:08:17 Kugel scriber. So
00:08:19 --> 00:08:20 I've got one of those.
00:08:20 --> 00:08:21 Professor Fred Watson: Have you?
00:08:22 --> 00:08:23 Andrew Dunkley: Yeah. There it is.
00:08:23 --> 00:08:24 Professor Fred Watson: Mangle.
00:08:24 --> 00:08:26 Andrew Dunkley: It's a pen. It's German looking.
00:08:26 --> 00:08:28 Professor Fred Watson: Hold it up. Ah, okay.
00:08:28 --> 00:08:29 Andrew Dunkley: Google scriber.
00:08:29 --> 00:08:31 Professor Fred Watson: Kugel scriber, yes.
00:08:32 --> 00:08:33 Andrew Dunkley: You know what German is? Uh. You know what
00:08:33 --> 00:08:34 the German is for pencil?
00:08:35 --> 00:08:37 Professor Fred Watson: Uh, I probably did once, but I don't know.
00:08:41 --> 00:08:43 All right. Uh, it's probably.
00:08:44 --> 00:08:45 I only.
00:08:45 --> 00:08:47 Andrew Dunkley: I did languages at high school, and I was
00:08:47 --> 00:08:49 very good at them. And I should have probably
00:08:49 --> 00:08:51 pursued that somewhere along the line, but
00:08:51 --> 00:08:52 German stuck with me.
00:08:52 --> 00:08:52 Professor Fred Watson: I.
00:08:53 --> 00:08:56 Andrew Dunkley: Some of the references I still remember
00:08:56 --> 00:08:57 today. Someone's going to correct me now
00:08:57 --> 00:08:59 because I probably buggered up the, uh,
00:08:59 --> 00:09:01 pronunciation anyway.
00:09:02 --> 00:09:03 Professor Fred Watson: That's all right.
00:09:03 --> 00:09:04 Andrew Dunkley: I'm just showing off now.
00:09:04 --> 00:09:07 Professor Fred Watson: No, ah, it's a side of your character that I
00:09:07 --> 00:09:08 was unaware of, Andrew. Um,
00:09:10 --> 00:09:12 curiously, I, uh,
00:09:13 --> 00:09:16 never joined Lerman at school. I
00:09:16 --> 00:09:19 never learned Sherman at school. Um,
00:09:19 --> 00:09:21 but, uh, uh, when I was 14,
00:09:22 --> 00:09:25 uh, I went on a school exchange to
00:09:25 --> 00:09:27 Germany, which was Barbara, because I wasn't
00:09:27 --> 00:09:29 studying German. But that was my first
00:09:30 --> 00:09:32 overseas visit, of course, from the United
00:09:32 --> 00:09:34 Kingdom. Um, and so I've
00:09:34 --> 00:09:37 spent the. However many years it
00:09:37 --> 00:09:40 is, 60 odd years since then
00:09:40 --> 00:09:43 trying to learn German and.
00:09:44 --> 00:09:47 Andrew Dunkley: Yeah, yeah, look, I'm so
00:09:47 --> 00:09:49 jealous of students in countries like the
00:09:49 --> 00:09:52 United States and the UK and Europe because
00:09:52 --> 00:09:54 they get to do excursions to other countries.
00:09:55 --> 00:09:57 In Australia, we got to do excursions to
00:09:57 --> 00:10:00 Sydney and Canberra. I mean, come on.
00:10:02 --> 00:10:05 That was it. Yeah, that was as good as it
00:10:05 --> 00:10:07 got for us. Yeah, I mean, these days they get
00:10:07 --> 00:10:10 to go to New Zealand once in a while. Um,
00:10:10 --> 00:10:13 but yeah, we're so far from everywhere. It's
00:10:13 --> 00:10:15 just not easy. Although my son did go to get
00:10:15 --> 00:10:18 to do a couple of weeks in Japan through high
00:10:18 --> 00:10:18 school.
00:10:18 --> 00:10:19 Professor Fred Watson: So there you go.
00:10:19 --> 00:10:22 Andrew Dunkley: There are a few options these days. This is
00:10:22 --> 00:10:24 Space Nuts. Andrew Dunkley here with
00:10:24 --> 00:10:25 Professor Fred Watson.
00:10:28 --> 00:10:30 Generic: Three, two, one.
00:10:31 --> 00:10:34 Andrew Dunkley: Space Nuts. Uh, we better keep moving. Uh,
00:10:34 --> 00:10:35 thank you, Steve.
00:10:35 --> 00:10:37 Let's get a question from Gus.
00:10:38 --> 00:10:41 Gus: Hello, Professor Fred and uh, Andrew.
00:10:41 --> 00:10:44 Uh, this is Gus Iverson from Issaquah,
00:10:44 --> 00:10:46 Washington. I sent in a question for you guys
00:10:46 --> 00:10:49 previously and you thought I was in Western
00:10:49 --> 00:10:51 Australia. Yes, I, I've been thinking about,
00:10:52 --> 00:10:53 um, gravity, uh,
00:10:55 --> 00:10:58 today. And it, it came to my mind that
00:10:58 --> 00:11:00 if, uh, energy and mass
00:11:00 --> 00:11:03 are equivalent, then essentially,
00:11:04 --> 00:11:07 uh, shouldn't energy also create
00:11:07 --> 00:11:10 gravity at some level?
00:11:11 --> 00:11:13 Um, I'm not sure if this is a related
00:11:13 --> 00:11:16 question or an extension or
00:11:16 --> 00:11:19 a separate question though. Um, uh,
00:11:19 --> 00:11:22 additionally, um, if a
00:11:22 --> 00:11:25 body of any size is
00:11:25 --> 00:11:27 generating or has mass
00:11:28 --> 00:11:30 and it is generating a
00:11:30 --> 00:11:33 gravitational field, does
00:11:33 --> 00:11:35 not that field itself
00:11:37 --> 00:11:39 have energy and mass?
00:11:40 --> 00:11:42 And would that field not
00:11:42 --> 00:11:45 create additional gravity
00:11:46 --> 00:11:47 by its simple existence?
00:11:48 --> 00:11:51 So if that's the case,
00:11:51 --> 00:11:54 or even kind of the case, my question is,
00:11:55 --> 00:11:57 where does the energy and mass go? If,
00:11:58 --> 00:12:00 um, or, um.
00:12:02 --> 00:12:04 I have no idea where to go with this.
00:12:04 --> 00:12:05 Professor Fred Watson: Thank you.
00:12:05 --> 00:12:07 Gus: Uh, I love the show and, uh, appreciate being
00:12:07 --> 00:12:08 able to ask questions.
00:12:09 --> 00:12:11 Andrew Dunkley: Thank you, Gus. Uh, that sounded very much
00:12:11 --> 00:12:13 like something from catch 22.
00:12:14 --> 00:12:16 Was it apples or tomatoes? They were trying
00:12:16 --> 00:12:19 to. I don't know. Um,
00:12:19 --> 00:12:21 but, uh, yeah, it sounded a bit like that.
00:12:21 --> 00:12:24 Um, gravity plus energy, body plus
00:12:24 --> 00:12:27 mass plus gravity equals energy. But
00:12:27 --> 00:12:30 then does that add mass which adds to
00:12:30 --> 00:12:32 gravity? I think that's what he was trying
00:12:32 --> 00:12:32 to.
00:12:32 --> 00:12:35 Professor Fred Watson: Yeah, that's right. So, so you've got a. You
00:12:35 --> 00:12:37 know, the whole thing gets completely out of
00:12:37 --> 00:12:40 hand because everything's got gravity. Um,
00:12:40 --> 00:12:43 I think, uh, so the first part of what Gus
00:12:43 --> 00:12:45 was saying is what we've just been talking
00:12:45 --> 00:12:47 about. You know, if you have energy and
00:12:47 --> 00:12:50 mass, um, and
00:12:52 --> 00:12:55 gravitation, you probably have to
00:12:55 --> 00:12:56 be careful with the words.
00:12:58 --> 00:12:59 Gravitation is a Potential.
00:13:01 --> 00:13:04 Uh, an object in a gravitational field has
00:13:04 --> 00:13:06 potential energy, so it does have energy.
00:13:07 --> 00:13:08 Uh, but
00:13:10 --> 00:13:12 I kind of need to take this one and notice.
00:13:12 --> 00:13:14 Actually, you did give me notice, Andrew, but
00:13:14 --> 00:13:16 I didn't have time to really look further
00:13:16 --> 00:13:16 into it.
00:13:17 --> 00:13:17 Andrew Dunkley: But.
00:13:19 --> 00:13:21 Professor Fred Watson: I think there's a stumbling block somewhere
00:13:21 --> 00:13:24 in that argument, uh, which is probably that
00:13:24 --> 00:13:26 gravitational energy isn't energy. That's
00:13:26 --> 00:13:29 convertible to mass. Um, but I
00:13:29 --> 00:13:32 need to get my thoughts clearer on that,
00:13:32 --> 00:13:34 which they aren't at the moment. So, Gus,
00:13:34 --> 00:13:37 thank you for a very, uh, tricky question,
00:13:38 --> 00:13:40 uh, which, um, I might think a little bit
00:13:40 --> 00:13:42 more about. Uh, and,
00:13:43 --> 00:13:46 uh, perhaps we will revisit it in a future
00:13:46 --> 00:13:48 episode of Spacenuts. Q and A.
00:13:50 --> 00:13:53 Andrew Dunkley: Um, I put a, uh, homework marker next to it.
00:13:53 --> 00:13:55 Professor Fred Watson: That's what I. I'm just doing that. I'm doing
00:13:55 --> 00:13:58 it. You're doing it in your, uh, kugel.
00:13:59 --> 00:14:01 Andrew Dunkley: I'm using a red Kugel scriber.
00:14:01 --> 00:14:02 Professor Fred Watson: Okay.
00:14:03 --> 00:14:05 Andrew Dunkley: I don't know what the German word for red is,
00:14:05 --> 00:14:05 though.
00:14:06 --> 00:14:06 Professor Fred Watson: Oh.
00:14:06 --> 00:14:08 Andrew Dunkley: Probably do it on translator.
00:14:08 --> 00:14:08 Professor Fred Watson: Uh.
00:14:09 --> 00:14:10 Andrew Dunkley: Ah, there you are.
00:14:10 --> 00:14:12 Professor Fred Watson: Yeah, there you are.
00:14:12 --> 00:14:13 Andrew Dunkley: I don't have to look it up.
00:14:13 --> 00:14:14 Professor Fred Watson: You do.
00:14:15 --> 00:14:17 Andrew Dunkley: So, Gus, um, dunno. We don't know.
00:14:19 --> 00:14:20 Maybe. Possibly. Could be.
00:14:21 --> 00:14:24 Professor Fred Watson: Don't know. Yeah, but we'll. How's
00:14:24 --> 00:14:24 that?
00:14:25 --> 00:14:26 Andrew Dunkley: Don't yet know.
00:14:28 --> 00:14:29 I like that.
00:14:29 --> 00:14:29 Professor Fred Watson: Yeah.
00:14:29 --> 00:14:32 Andrew Dunkley: Uh, let's, um, get to the final question.
00:14:32 --> 00:14:35 We'll get back to you, Gus. At some stage in
00:14:35 --> 00:14:37 Western Australia, or it could be the United
00:14:37 --> 00:14:37 States.
00:14:37 --> 00:14:40 Uh, now we've got a question from. Oh,
00:14:41 --> 00:14:43 um, just by coincidence, from New Zealand
00:14:43 --> 00:14:46 again. Um, hi, Tim. Amazing
00:14:46 --> 00:14:48 podcast. Which one are you talking about now?
00:14:48 --> 00:14:51 Uh, I have been listening since your early
00:14:51 --> 00:14:53 days and have always, uh, looked forward to
00:14:53 --> 00:14:55 new, uh, uploads. My question is around the
00:14:55 --> 00:14:58 discovery of early galaxies from the James
00:14:58 --> 00:15:00 Webb Space Telescope. Is it possible for
00:15:00 --> 00:15:03 earlier galaxies to be traveling towards us
00:15:03 --> 00:15:06 that are currently out of reach? Uh, filling
00:15:06 --> 00:15:09 with potentially, uh, nothing. Uh,
00:15:10 --> 00:15:12 filling where potentially nothing was in view
00:15:12 --> 00:15:15 before. Uh, if possible, would the light be
00:15:15 --> 00:15:18 compressed? How would the instruments deal
00:15:18 --> 00:15:20 with that? Hope that makes sense. Cheers.
00:15:20 --> 00:15:22 Nick from Auckland, New Zealand.
00:15:25 --> 00:15:27 My brain just went, well, I suppose it's
00:15:27 --> 00:15:29 possible, but how do we prove it until it
00:15:29 --> 00:15:29 happens?
00:15:30 --> 00:15:32 Professor Fred Watson: Yes. So, a. Ah, couple of things in here. Um,
00:15:33 --> 00:15:36 thanks, Nick. Great question. The last bit
00:15:36 --> 00:15:38 about light being compressed, um,
00:15:39 --> 00:15:42 and in a way, that's, um, quite
00:15:42 --> 00:15:44 a nice way of putting it. So anything that
00:15:44 --> 00:15:46 comes towards you that's emitting light,
00:15:46 --> 00:15:48 its light will be blue shifted. In other
00:15:48 --> 00:15:51 words, its wavelength will get
00:15:51 --> 00:15:54 shorter. And that's saying
00:15:54 --> 00:15:56 it's compressed is pretty well you know,
00:15:56 --> 00:15:58 that's pretty well what happens. It's like,
00:15:58 --> 00:16:00 uh, um, you know, the good old
00:16:01 --> 00:16:04 ambulance, uh, siren or fire engine siren or
00:16:04 --> 00:16:06 whatever it is coming towards you, uh, which
00:16:06 --> 00:16:09 compresses the sound waves. And the
00:16:09 --> 00:16:11 result is an increase in pitch. Which
00:16:11 --> 00:16:13 corresponds to a shortening of wavelength. So
00:16:13 --> 00:16:16 that's standard physics. We can detect,
00:16:16 --> 00:16:19 uh, by the Doppler shift, anything coming
00:16:19 --> 00:16:22 towards us. Uh, by the fact that its light is
00:16:22 --> 00:16:24 shifted towards the blue end of the spectrum.
00:16:25 --> 00:16:28 Um, but, um, the
00:16:28 --> 00:16:31 first bit of the question about galaxies,
00:16:32 --> 00:16:34 earlier galaxies traveling towards us.
00:16:34 --> 00:16:35 Andrew Dunkley: Um.
00:16:39 --> 00:16:41 Professor Fred Watson: When we think about galaxies, we have
00:16:42 --> 00:16:45 two different velocities involved. One
00:16:45 --> 00:16:48 is the velocity of a galaxy as it's
00:16:48 --> 00:16:50 carried along by the expansion of the
00:16:50 --> 00:16:53 universe. Uh, and that is
00:16:53 --> 00:16:55 what we measure as a redshift. Uh,
00:16:56 --> 00:16:58 the expansion of the universe is carrying
00:16:58 --> 00:17:00 galaxies away from us. And so their light is
00:17:00 --> 00:17:03 being redshifted. Uh, and by the
00:17:03 --> 00:17:06 time you get to these really early galaxies
00:17:06 --> 00:17:08 where you're looking back, uh, almost the
00:17:08 --> 00:17:11 whole edge of the universe, the redshift is
00:17:11 --> 00:17:14 very considerable. It's a factor of 13 or 14,
00:17:14 --> 00:17:16 something like that. We're giving the name Z.
00:17:16 --> 00:17:19 Uh, the redshift is about 14. So,
00:17:19 --> 00:17:21 um. I beg your pardon. No, that's not true.
00:17:21 --> 00:17:24 Uh, that's me confusing the age
00:17:24 --> 00:17:27 with the redshift. Forget that bit. But
00:17:27 --> 00:17:29 the number's quite high. The redshifts are
00:17:29 --> 00:17:31 probably five or six or something like that.
00:17:31 --> 00:17:34 But, uh, it's still a high level of
00:17:35 --> 00:17:36 the light being stretched out by the
00:17:36 --> 00:17:39 expansion of the universe. So that's one
00:17:39 --> 00:17:41 velocity. But galaxies can have
00:17:42 --> 00:17:45 superimposed on that a velocity which we call
00:17:45 --> 00:17:48 a peculiar motion. Its own velocity, uh,
00:17:48 --> 00:17:51 caused by local eddies in
00:17:51 --> 00:17:54 space or whatever. Uh, that. That might,
00:17:54 --> 00:17:56 um, move a galaxy towards us. It's the
00:17:56 --> 00:17:59 gravitational field that it's exposed
00:17:59 --> 00:18:02 to. Very much like the
00:18:02 --> 00:18:04 analog is always a river carrying you along.
00:18:05 --> 00:18:06 Uh, and if you're in a rowboat, you can move
00:18:06 --> 00:18:08 relative to the river. But the river's always
00:18:08 --> 00:18:10 carrying you along. That's exactly what's
00:18:10 --> 00:18:13 happening with the Hubble flow, the expansion
00:18:13 --> 00:18:15 of the universe. And these peculiar motions
00:18:15 --> 00:18:17 are superimposed on that. But they're much,
00:18:17 --> 00:18:19 much less than the motion,
00:18:20 --> 00:18:22 uh, those distances, uh, or look
00:18:22 --> 00:18:25 back times. It's much, much less than the
00:18:26 --> 00:18:28 expansion flow of the universe. So no, there
00:18:28 --> 00:18:30 won't be anything hidden from us that's
00:18:30 --> 00:18:32 coming towards us. I don't think it's an
00:18:32 --> 00:18:34 interesting suggestion. But, uh, uh,
00:18:34 --> 00:18:36 everything's moving away from us at this very
00:18:36 --> 00:18:39 high velocity. At those distances, M
00:18:39 --> 00:18:40 of Course.
00:18:40 --> 00:18:42 Andrew Dunkley: Um, Nick, if you want to check with us, uh,
00:18:42 --> 00:18:44 in a million years or so, we might have an
00:18:44 --> 00:18:45 alternative answer.
00:18:45 --> 00:18:47 Professor Fred Watson: Well, that's true. Uh, put that in your diary
00:18:47 --> 00:18:50 and, uh, I'll mark it with an
00:18:50 --> 00:18:52 asterisk, knowing that it's work for a
00:18:52 --> 00:18:54 million years time. Yes,
00:18:55 --> 00:18:56 it's good.
00:18:56 --> 00:18:59 Andrew Dunkley: Um, I'm really disappointed that the people
00:18:59 --> 00:19:01 who make diaries haven't gone ahead that far
00:19:01 --> 00:19:01 yet.
00:19:06 --> 00:19:08 Thanks, Nick. Um, probably not, I think, is
00:19:08 --> 00:19:11 the answer. Um, but thanks for the
00:19:11 --> 00:19:13 question. Thanks to everyone who sent in
00:19:13 --> 00:19:14 questions. Keep them coming. You can do that
00:19:14 --> 00:19:17 via our, ah, website spacenutspodcast.com
00:19:17 --> 00:19:20 spacenuts IO which, uh, has two
00:19:20 --> 00:19:23 options. The AMA tab at the top where you can
00:19:23 --> 00:19:25 send us text audio or the send us your
00:19:25 --> 00:19:28 questions, um, button on the right hand side
00:19:28 --> 00:19:30 of our home screen. Don't forget to tell us
00:19:30 --> 00:19:32 who you are and where you're from. And you
00:19:32 --> 00:19:35 can probably upload your audio questions on
00:19:35 --> 00:19:36 any device as long as you've got a
00:19:36 --> 00:19:39 microphone. Mobile phones are perfect for
00:19:39 --> 00:19:42 this. Um, but, um, a lot of people have home
00:19:42 --> 00:19:44 computers with mics built in, et cetera, et
00:19:44 --> 00:19:46 cetera, et cetera. Always happy to hear from
00:19:46 --> 00:19:49 you. Um, Fred, thanks so much. We're done
00:19:49 --> 00:19:51 with another episode. Geez. We're wrapping
00:19:51 --> 00:19:51 them up.
00:19:52 --> 00:19:53 Professor Fred Watson: We are racking him up. Good to talk to you,
00:19:53 --> 00:19:55 Andrew. And we'll speak again soon.
00:19:56 --> 00:19:58 Andrew Dunkley: Indeed we will. Professor Fred Watson,
00:19:58 --> 00:20:00 astronomer at large. And thanks to Huw in the
00:20:00 --> 00:20:02 studio for collating.
00:20:04 --> 00:20:06 Not much, but, uh, we thank him anyway. And
00:20:06 --> 00:20:07 from me, Andrew Dunkley, thanks for your
00:20:07 --> 00:20:10 company. See you on the very next episode of
00:20:10 --> 00:20:11 Space Nuts. Bye bye.
00:20:12 --> 00:20:15 Generic: You've been listening to the Space Nuts
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