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.
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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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Episode link: https://play.headliner.app/episode/30952966?utm_source=youtube
00:00:00 --> 00:00:02 Hi there. This is Space Nuts Q&A. My
00:00:02 --> 00:00:04 name is Andrew Dunley. Great to have
00:00:04 --> 00:00:05 your company. Coming up on this episode,
00:00:05 --> 00:00:08 we'll answer questions from Steve, Gus,
00:00:08 --> 00:00:10 and Nick. Uh Steve and Gus are sort of
00:00:10 --> 00:00:13 focused on the same thing, gravity.
00:00:13 --> 00:00:15 Steve wants to know if it can exist
00:00:16 --> 00:00:18 without mass. Uh and and Gus is talking
00:00:18 --> 00:00:21 about gravity and energy, and what's the
00:00:21 --> 00:00:24 relationship? And Nick is asking about
00:00:24 --> 00:00:26 galaxy movements, and are any moving
00:00:26 --> 00:00:29 towards us that we can't see yet?
00:00:29 --> 00:00:31 Well, we don't know. We can't see them
00:00:31 --> 00:00:33 yet. Uh, but we'll see if we can tackle
00:00:33 --> 00:00:36 all of that on this episode of Space
00:00:36 --> 00:00:36 Nuts.
00:00:36 --> 00:00:41 >> 15 seconds. Guidance is internal. 10 9
00:00:41 --> 00:00:43 Ignition sequence start.
00:00:43 --> 00:00:44 >> Space nuts.
00:00:44 --> 00:00:46 >> 5 4 3 2
00:00:46 --> 00:00:49 >> 1 2 3 4 5 5 4 3 2 1
00:00:49 --> 00:00:50 >> Space Nuts.
00:00:50 --> 00:00:52 >> Astronauts report. It feels good.
00:00:52 --> 00:00:55 >> Here he is again. Professor Fred Watson.
00:00:55 --> 00:00:58 Hello, Fred. Hello, Andrew. Hello. How
00:00:58 --> 00:01:00 are you doing now?
00:01:00 --> 00:01:04 >> I'm doing the same as I was before.
00:01:04 --> 00:01:05 >> How about you?
00:01:05 --> 00:01:07 >> Uh, well, I'm I'm still doing the same
00:01:07 --> 00:01:10 as I was before. Yes, that's right. And
00:01:10 --> 00:01:11 I hope to be doing the same again very
00:01:11 --> 00:01:12 soon.
00:01:12 --> 00:01:17 >> Yes, indeed. Yes. Shall we just sort of
00:01:17 --> 00:01:19 muck in and get these questions sorted
00:01:19 --> 00:01:23 out? I I it was a like a couple of weeks
00:01:23 --> 00:01:26 ago we we had um gravity questions
00:01:26 --> 00:01:28 coming in thick and fast. Uh no black
00:01:28 --> 00:01:30 hole questions but today it's gravity
00:01:30 --> 00:01:31 questions this
00:01:31 --> 00:01:34 >> and our first our first one comes from
00:01:34 --> 00:01:35 Steve.
00:01:35 --> 00:01:38 >> Hi guys, my name is Steve. I'm uh from
00:01:38 --> 00:01:43 New Zealand. Um really enjoy your show.
00:01:43 --> 00:01:46 recently read a article
00:01:46 --> 00:01:50 implying that uh gravity could be
00:01:50 --> 00:01:53 possible without mass
00:01:53 --> 00:01:57 and um I'm wondering if that would be uh
00:01:57 --> 00:02:02 another alternative explanation uh to um
00:02:02 --> 00:02:07 uh to dark matter and to uh Mond.
00:02:07 --> 00:02:09 Yeah, I don't know if that makes it very
00:02:09 --> 00:02:11 clear to you. Anyway, thanks. All right.
00:02:11 --> 00:02:13 Uh Steve, thanks for the question.
00:02:13 --> 00:02:17 Gravity without mass. Well, I doubt that
00:02:17 --> 00:02:19 uh we can turn to the Catholic Church
00:02:19 --> 00:02:22 because they do they do have mass. Um
00:02:22 --> 00:02:24 but
00:02:24 --> 00:02:27 [Music]
00:02:27 --> 00:02:28 terrible. Uh it's an interesting
00:02:28 --> 00:02:33 question though. It is. And um so yeah,
00:02:33 --> 00:02:36 my reading on this, excuse me, is is
00:02:36 --> 00:02:41 yes. Um that's correct. So, uh, actually
00:02:41 --> 00:02:43 there's a nice thread about this on
00:02:43 --> 00:02:46 Reddit if anybody looks at that website.
00:02:46 --> 00:02:49 >> I do. And, uh, well, I love Reddit.
00:02:49 --> 00:02:52 >> Yeah.
00:02:52 --> 00:02:54 I'm really, well, I do remember my, uh,
00:02:54 --> 00:02:56 one of my sons was an absolute Reddit
00:02:56 --> 00:03:00 fiend at one time. He was very much um,
00:03:00 --> 00:03:04 a Reddit fan. Uh, now, so that's how I
00:03:04 --> 00:03:05 was aware of it. But um, but I haven't
00:03:06 --> 00:03:08 been a great user of Reddit. But the
00:03:08 --> 00:03:11 bottom line, excuse me, is
00:03:11 --> 00:03:15 um and and this is the way is phrased in
00:03:15 --> 00:03:18 this particular conversation. If you
00:03:18 --> 00:03:20 increase the temperature
00:03:20 --> 00:03:24 of an object and they take a planet in
00:03:24 --> 00:03:27 this case uh and in fact I might just
00:03:27 --> 00:03:30 read it uh because this kind of is quite
00:03:30 --> 00:03:32 interesting.
00:03:32 --> 00:03:34 and
00:03:34 --> 00:03:36 take your Neptune you take your
00:03:36 --> 00:03:38 Neptunian planet something the size of
00:03:38 --> 00:03:40 Neptune raise the temperature by 300°
00:03:40 --> 00:03:43 Kelvin instantly now the mass of Neptune
00:03:44 --> 00:03:47 is about 10 26 kg and if we roughly
00:03:47 --> 00:03:49 assume all its hydrogen uh uh
00:03:49 --> 00:03:53 corresponds to about 6 * 10 52 particles
00:03:53 --> 00:03:56 of hydrogen uh it's the thermal energy
00:03:56 --> 00:03:59 is roughly given by an equation there E=
00:03:59 --> 00:04:01 NT
00:04:01 --> 00:04:03 uh uh which leads to an increase in
00:04:03 --> 00:04:06 thermal energy
00:04:06 --> 00:04:10 uh of da d and it's a large number of
00:04:10 --> 00:04:13 jewels um actually it's a small number
00:04:13 --> 00:04:18 of jewels it's k * 6 * 10 - 52 * 300
00:04:18 --> 00:04:20 jewels
00:04:20 --> 00:04:24 uh which um if you then convert that so
00:04:24 --> 00:04:26 so what what this is saying is you you
00:04:26 --> 00:04:29 you warm up a planet you get an increase
00:04:29 --> 00:04:32 uh in the thermal energy of that planet.
00:04:32 --> 00:04:35 You can then use E= MC² to convert that
00:04:35 --> 00:04:38 thermal energy into mass and in this
00:04:38 --> 00:04:40 case it comes out to be something like 3
00:04:40 --> 00:04:47 * 10 15 kg which is a lot but uh is not
00:04:47 --> 00:04:49 very much in comparison with a planet.
00:04:49 --> 00:04:53 Uh but that does mean that adding energy
00:04:53 --> 00:04:55 to something will increase its
00:04:55 --> 00:05:00 gravitational mass. Now um the Steve's
00:05:00 --> 00:05:04 sort of uh you know um next step in the
00:05:04 --> 00:05:06 argument from that is whether that could
00:05:06 --> 00:05:08 be misleading us in the idea of dark
00:05:08 --> 00:05:13 matter and things of that sort. Um and
00:05:13 --> 00:05:15 uh I I can't really get my head around
00:05:15 --> 00:05:18 how that would work. Um he mentioned M
00:05:18 --> 00:05:21 as well the modified Newtonian dynamics.
00:05:21 --> 00:05:25 Uh because my understanding is that
00:05:25 --> 00:05:28 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
00:05:32 --> 00:05:35 account everything. Uh I've read some of
00:05:35 --> 00:05:39 the papers on this. And so things like
00:05:39 --> 00:05:41 um you know gravitational
00:05:41 --> 00:05:45 uh gravitational influence of of pure
00:05:45 --> 00:05:47 energy and in this case we're talking
00:05:47 --> 00:05:52 about heat energy. Uh that uh is likely
00:05:52 --> 00:05:54 to be something that would be already in
00:05:54 --> 00:05:56 the equations. Um so I don't think it's
00:05:56 --> 00:05:58 the answer but it's a really interesting
00:05:58 --> 00:06:00 suggestion and an interesting thing to
00:06:00 --> 00:06:03 think about. Uh so thank you very much
00:06:03 --> 00:06:04 Steve.
00:06:04 --> 00:06:07 >> Yeah indeed. um just made me wonder, are
00:06:07 --> 00:06:09 we increasing Earth's gravity because
00:06:09 --> 00:06:11 we're heating the planet up?
00:06:11 --> 00:06:15 >> Yep, that's probably right. Um that I
00:06:15 --> 00:06:17 mean the the example that uh I just read
00:06:17 --> 00:06:20 out was about three t 300
00:06:20 --> 00:06:23 300° Kelvin, an instant uh increase in
00:06:24 --> 00:06:26 that. We're talking about one or two
00:06:26 --> 00:06:29 degrees Kelvin. uh but uh which makes a
00:06:29 --> 00:06:31 big difference to the earth's atmosphere
00:06:31 --> 00:06:32 but probably not that much difference to
00:06:32 --> 00:06:36 its uh you know gravitational potential.
00:06:36 --> 00:06:38 M okay. So the answer is yes. Gravity
00:06:38 --> 00:06:42 can exist without mass but it's probably
00:06:42 --> 00:06:46 not a major factor. Is that fair enough?
00:06:46 --> 00:06:50 >> Uh yes that is right. Um I just been
00:06:50 --> 00:06:52 dragging through my memory Andrew
00:06:52 --> 00:06:55 something else that's sort of vaguely
00:06:55 --> 00:06:59 related to this. Um which is the and we
00:06:59 --> 00:07:01 haven't used this name but we did talk
00:07:01 --> 00:07:04 about it a while ago the cougal blitz.
00:07:04 --> 00:07:06 And do you know what a cougall blitz is?
00:07:06 --> 00:07:10 >> Uh look, I've heard this before. Uh no,
00:07:10 --> 00:07:11 remind me.
00:07:11 --> 00:07:15 >> Yeah. So it's it basically is uh a black
00:07:15 --> 00:07:18 hole made of light. Uh it's and
00:07:18 --> 00:07:20 Wikipedia says it's a concentration of
00:07:20 --> 00:07:22 heat, light, or radiation so intense
00:07:22 --> 00:07:24 that its energy forms an event horizon
00:07:24 --> 00:07:26 and becomes selftrapped. In other words,
00:07:26 --> 00:07:28 if enough radiation is aimed into a
00:07:28 --> 00:07:31 region of space, the concentration of
00:07:31 --> 00:07:33 energy can walk spaceime so much that it
00:07:33 --> 00:07:36 creates a black hole. It's a black hole.
00:07:36 --> 00:07:39 It is a black hole whose original mass
00:07:39 --> 00:07:41 energy was in the form of radiant energy
00:07:41 --> 00:07:43 rather than matter.
00:07:43 --> 00:07:46 Uh now um there is a paper that was
00:07:46 --> 00:07:49 published in
00:07:49 --> 00:07:50
00:07:50 --> 00:07:53 that concludes that a phenomenon like
00:07:53 --> 00:07:55 this cannot occur in any realistic
00:07:55 --> 00:07:58 scenario within our universe. So cougal
00:07:58 --> 00:08:01 blitzes are a theoretical entity that
00:08:01 --> 00:08:04 are not are thought not to occur in
00:08:04 --> 00:08:07 nature. Uh but it is a similar thing
00:08:07 --> 00:08:09 isn't it? It's a it basically it's a
00:08:09 --> 00:08:11 it's a black hole made of energy.
00:08:11 --> 00:08:14 >> Yeah. Wow, that's really interesting. I
00:08:14 --> 00:08:15 tell you something else that does exist
00:08:15 --> 00:08:19 is a Google Scriber. So, so
00:08:19 --> 00:08:22 I've got one of those. Have you?
00:08:22 --> 00:08:24 >> Yeah, there it is.
00:08:24 --> 00:08:26 >> It's a pen. It's German.
00:08:26 --> 00:08:28 >> Hold it up. Ah, okay.
00:08:28 --> 00:08:29 >> Cougle scriber.
00:08:29 --> 00:08:31 >> A cougriber.
00:08:31 --> 00:08:32 >> Yes.
00:08:32 --> 00:08:33 >> Do you know what German is? You know
00:08:33 --> 00:08:35 what the German is for pencil?
00:08:35 --> 00:08:37 >> Uh, I probably did once, but I don't
00:08:37 --> 00:08:38 now. That's
00:08:38 --> 00:08:41 >> bliff blift.
00:08:41 --> 00:08:42 >> All right.
00:08:42 --> 00:08:44 >> It's probably
00:08:44 --> 00:08:47 I only I did languages at high school
00:08:47 --> 00:08:48 and I was very good at them and I should
00:08:48 --> 00:08:50 have probably pursued that somewhere
00:08:50 --> 00:08:52 along the line, but German stuck with
00:08:52 --> 00:08:55 me. I some of the references I still
00:08:55 --> 00:08:57 remember today. Someone's going to
00:08:57 --> 00:08:58 correct me now because I'd probably
00:08:58 --> 00:09:01 bugger it up the pronunciation.
00:09:01 --> 00:09:02 >> Anyway,
00:09:02 --> 00:09:03 >> that's all right.
00:09:03 --> 00:09:04 >> I'm just showing off now. No, it's a
00:09:04 --> 00:09:07 it's a side of your character that I was
00:09:07 --> 00:09:11 unaware of. Um, Andrew, I um, curiously,
00:09:11 --> 00:09:14 I uh never joined never joined Lurman at
00:09:14 --> 00:09:17 school. I never learned German at
00:09:17 --> 00:09:22 school. Um, 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 bar because I wasn't
00:09:27 --> 00:09:29 studying German, but that that was my
00:09:29 --> 00:09:31 first overseas visit, of course, from
00:09:31 --> 00:09:34 the United Kingdom. Um, and so I've
00:09:34 --> 00:09:38 spent the the however many years it is,
00:09:38 --> 00:09:41 60 odd years since then, trying to learn
00:09:41 --> 00:09:43 German.
00:09:43 --> 00:09:45 And um, yeah.
00:09:45 --> 00:09:48 >> Yeah. Look, I'm so jealous of students
00:09:48 --> 00:09:50 in countries like the United States and
00:09:50 --> 00:09:53 the UK and Europe because they get to do
00:09:53 --> 00:09:55 excursions to other countries. In
00:09:55 --> 00:09:57 Australia, we got to do excursions to
00:09:57 --> 00:10:02 Sydney and Canra. I mean, come on.
00:10:02 --> 00:10:03 That was it.
00:10:03 --> 00:10:04 >> Yeah,
00:10:04 --> 00:10:06 >> that was as good as it got for us.
00:10:06 --> 00:10:06 >> Yeah.
00:10:06 --> 00:10:08 >> I mean, these days they get to go to New
00:10:08 --> 00:10:11 Zealand once in a while. Um, but yeah,
00:10:11 --> 00:10:13 we we're so far from everywhere, it's
00:10:13 --> 00:10:15 just not easy. Although, my son did go
00:10:15 --> 00:10:17 to go get to do a couple of weeks in
00:10:17 --> 00:10:19 Japan through high school. So,
00:10:19 --> 00:10:19 >> there you go.
00:10:19 --> 00:10:21 >> There are a few options these days.
00:10:22 --> 00:10:23 >> This is Space Nuts. Andrew Dunley here
00:10:23 --> 00:10:28 with Professor Fred Watson.
00:10:28 --> 00:10:31 >> Three, two, one.
00:10:31 --> 00:10:33 Space nuts.
00:10:33 --> 00:10:34 >> Uh, we better keep moving. Uh, thank
00:10:34 --> 00:10:37 you, Steve. Let's get a question from
00:10:37 --> 00:10:38 Gus.
00:10:38 --> 00:10:42 >> Hello, Professor Fred and, uh, Andrew.
00:10:42 --> 00:10:44 This is Gus Iverson from Isiqua,
00:10:44 --> 00:10:46 Washington. I sent in a question for you
00:10:46 --> 00:10:47 guys previously, and you thought I was
00:10:47 --> 00:10:50 in Western Western Australia.
00:10:50 --> 00:10:53 >> Yes. I I've been thinking about uh uh
00:10:53 --> 00:10:57 gravity uh today and it it came to my
00:10:57 --> 00:11:01 mind that if uh energy and mass are
00:11:01 --> 00:11:05 equivalent then essentially uh shouldn't
00:11:05 --> 00:11:09 energy also create gravity at some
00:11:09 --> 00:11:11 level.
00:11:11 --> 00:11:14 Um I'm not sure if this is a related
00:11:14 --> 00:11:17 question or or an extension or or a
00:11:17 --> 00:11:19 separate question though. Um uh
00:11:19 --> 00:11:21 additionally
00:11:21 --> 00:11:25 um if a body of of any size is
00:11:25 --> 00:11:29 generating uh or has mass and it is
00:11:29 --> 00:11:33 generating a gravitational field,
00:11:33 --> 00:11:37 does not that field itself
00:11:37 --> 00:11:41 have energy and mass? And would that
00:11:41 --> 00:11:46 field not create additional gravity by
00:11:46 --> 00:11:48 its simple existence?
00:11:48 --> 00:11:53 So, if that's the case, or even kind of
00:11:53 --> 00:11:55 the case, my question is where does the
00:11:55 --> 00:12:00 energy and mass go if if um or
00:12:00 --> 00:12:03 uh I I I have no idea where to go with
00:12:04 --> 00:12:06 this. Thank you. Uh I love love the show
00:12:06 --> 00:12:08 and appreciate being able to ask
00:12:08 --> 00:12:09 questions.
00:12:09 --> 00:12:11 >> Thank you, Gus. Uh that sounded very
00:12:11 --> 00:12:14 much like something from Catch 22. Yeah.
00:12:14 --> 00:12:16 Was it was it apples or tomatoes? They
00:12:16 --> 00:12:20 were trying to I don't know. Um but uh
00:12:20 --> 00:12:22 yeah, it sounded a bit like that. Um
00:12:22 --> 00:12:25 gravity plus energy. Body plus mass plus
00:12:25 --> 00:12:28 gravity equals energy. But then does
00:12:28 --> 00:12:31 that add mass which adds to gravity? I
00:12:31 --> 00:12:32 think that's what he was trying to
00:12:32 --> 00:12:35 >> Yeah, that's right. So So you've got to
00:12:35 --> 00:12:37 you know the whole thing gets completely
00:12:37 --> 00:12:39 out of hand cuz everything's got
00:12:39 --> 00:12:42 gravity. Um I think uh so the first part
00:12:42 --> 00:12:44 of what Gus was saying is what we've
00:12:44 --> 00:12:46 just been talking about. You know if you
00:12:46 --> 00:12:49 put it into energy and mass
00:12:49 --> 00:12:52 >> um and
00:12:52 --> 00:12:55 gravitation you got be I probably have
00:12:55 --> 00:12:57 to be careful with the words
00:12:57 --> 00:13:01 gravitational gravitation is a potential
00:13:01 --> 00:13:03 uh an object in a gravitational field
00:13:03 --> 00:13:05 has potential energy. So, it does have
00:13:05 --> 00:13:10 energy. Uh, but it I I kind of need to
00:13:10 --> 00:13:12 take this one and notice. Actually, you
00:13:12 --> 00:13:14 did give me notice, Andrew, but I didn't
00:13:14 --> 00:13:16 have time to really look further into
00:13:16 --> 00:13:19 it. But I think um I think there's a I
00:13:20 --> 00:13:21 think there's a stumbling block
00:13:21 --> 00:13:23 somewhere in that argument. Uh, which is
00:13:23 --> 00:13:25 probably that gravitational energy isn't
00:13:25 --> 00:13:29 energy that's convertible to mass. Um,
00:13:29 --> 00:13:32 but I need to get my thoughts clearer on
00:13:32 --> 00:13:34 that, which they aren't at the moment.
00:13:34 --> 00:13:37 So Gus, thank you for a very uh tricky
00:13:37 --> 00:13:40 question uh which um I might think a
00:13:40 --> 00:13:43 little bit more about uh and
00:13:43 --> 00:13:46 >> uh perhaps we will revisit it in a
00:13:46 --> 00:13:49 future episode of Space Notes Q&A.
00:13:49 --> 00:13:52 >> I put a um I put a homework marker next
00:13:52 --> 00:13:53 to it.
00:13:53 --> 00:13:55 >> That's what I'm I'm just doing that. I'm
00:13:55 --> 00:13:57 doing it. You're doing it in your
00:13:57 --> 00:13:59 cougal.
00:13:59 --> 00:14:02 I'm using a red a red cougal scriber.
00:14:02 --> 00:14:03 Okay.
00:14:03 --> 00:14:05 I don't know what the German word for
00:14:05 --> 00:14:06 red is though.
00:14:06 --> 00:14:10 >> Oh, probably do it on translator.
00:14:10 --> 00:14:11 >> There you are.
00:14:11 --> 00:14:13 >> Yeah, there you are. I don't have to
00:14:13 --> 00:14:13 look it up.
00:14:13 --> 00:14:14 >> You don't.
00:14:14 --> 00:14:15 >> Um,
00:14:15 --> 00:14:19 >> so Gus, um, don't know. We don't know.
00:14:19 --> 00:14:22 Maybe, possibly. Could be. Don't know.
00:14:22 --> 00:14:23 >> There's the answer.
00:14:23 --> 00:14:23 >> Don't yet.
00:14:23 --> 00:14:24 >> How's that?
00:14:24 --> 00:14:28 >> Don't don't yet know.
00:14:28 --> 00:14:29 >> I like that.
00:14:29 --> 00:14:29 >> Yeah.
00:14:30 --> 00:14:32 >> 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
00:14:35 --> 00:14:37 in Western Australia or it could be the
00:14:37 --> 00:14:39 United States. Uh now we've got a
00:14:39 --> 00:14:42 question from oh um just by coincidence
00:14:42 --> 00:14:46 from New Zealand again. Um hi team
00:14:46 --> 00:14:47 amazing podcast. Which one are you
00:14:47 --> 00:14:50 talking about now? Uh I have been
00:14:50 --> 00:14:51 listening since your early days and I've
00:14:52 --> 00:14:54 always uh looked forward to new uh
00:14:54 --> 00:14:56 uploads. My question is around the
00:14:56 --> 00:14:57 discovery of early galaxies from the
00:14:57 --> 00:14:59 James Webb Space Telescope. Is it
00:14:59 --> 00:15:02 possible for earlier galaxies to be
00:15:02 --> 00:15:04 traveling towards us that are currently
00:15:04 --> 00:15:07 out of reach? Uh filling with uh
00:15:07 --> 00:15:11 potentially nothing uh uh filling where
00:15:11 --> 00:15:13 potentially nothing was in view before.
00:15:13 --> 00:15:15 Uh if possible, would the light be
00:15:16 --> 00:15:17 compressed? How would the instruments
00:15:17 --> 00:15:20 deal with that? Hope that makes sense.
00:15:20 --> 00:15:25 Cheers, Nick from Oakland, New Zealand.
00:15:25 --> 00:15:27 Now, my brain just went, well, I suppose
00:15:27 --> 00:15:29 it's possible, but how do we prove it?
00:15:29 --> 00:15:30 until it happens.
00:15:30 --> 00:15:32 >> Yes. So, uh, couple of things in here.
00:15:32 --> 00:15:35 Um, thanks Nick. Great question. The
00:15:35 --> 00:15:38 last bit about light being compressed.
00:15:38 --> 00:15:41 So, um, and in a way that's, you know,
00:15:41 --> 00:15:43 that's, um, quite a nice way of putting
00:15:43 --> 00:15:45 it. So, anything that comes toward you
00:15:45 --> 00:15:47 that's emitting light, it's light will
00:15:47 --> 00:15:49 be blue shifted. In other words,
00:15:49 --> 00:15:52 >> it's wavelength will get shorter. And,
00:15:52 --> 00:15:55 and that's saying it's compressed is
00:15:55 --> 00:15:56 pretty well, you know, that's pretty
00:15:56 --> 00:15:59 well what happens. It's like uh um you
00:15:59 --> 00:16:02 know the the the good old uh ambulance
00:16:02 --> 00:16:04 siren or fire engine siren or whatever
00:16:04 --> 00:16:06 it is coming towards you uh which
00:16:06 --> 00:16:09 compresses the uh the sound waves and
00:16:09 --> 00:16:11 the result is an increase in pitch which
00:16:11 --> 00:16:12 corresponds to a shortening of
00:16:12 --> 00:16:15 wavelength. So that's standard physics
00:16:15 --> 00:16:18 we we can detect uh by the Doppler shift
00:16:18 --> 00:16:21 anything coming towards us uh by the
00:16:21 --> 00:16:22 fact that it light is shifted towards
00:16:22 --> 00:16:27 the blue end of the spectrum. Um but um
00:16:27 --> 00:16:30 the the first bit of the question about
00:16:30 --> 00:16:32 galaxies
00:16:32 --> 00:16:36 earlier galaxies traveling towards us um
00:16:36 --> 00:16:38 we
00:16:38 --> 00:16:41 we when we think about galaxies we have
00:16:41 --> 00:16:43 two
00:16:43 --> 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 --> 00:16:54 universe. uh and that is what we measure
00:16:54 --> 00:16:57 as a red shift. Uh the expansion of the
00:16:57 --> 00:16:59 universe is carrying galaxies away from
00:16:59 --> 00:17:01 us and so their light is being
00:17:01 --> 00:17:04 redshifted. Uh and by the time you get
00:17:04 --> 00:17:06 to these really early galaxies where
00:17:06 --> 00:17:09 you're looking back uh almost the whole
00:17:09 --> 00:17:11 edge of the universe, the red shift is
00:17:11 --> 00:17:13 very considerable. It's a factor of 13
00:17:13 --> 00:17:15 or 14 something like that. We're given
00:17:15 --> 00:17:18 the name zed. Uh the red shift is about
00:17:18 --> 00:17:21 14. So, um, a big part, no, that's not
00:17:21 --> 00:17:23 true. Uh, that's that's me confusing the
00:17:24 --> 00:17:27 age with the red shift. Forget that bit.
00:17:27 --> 00:17:29 But the the numbers quite high. The red
00:17:29 --> 00:17:30 shifts are probably five or six or
00:17:30 --> 00:17:32 something like that. Uh, but it's still
00:17:32 --> 00:17:35 it's still a a high level of the, you
00:17:35 --> 00:17:36 know, the light being stretched out by
00:17:36 --> 00:17:38 the expansion of the universe. So,
00:17:38 --> 00:17:41 that's one velocity, but galaxies can
00:17:41 --> 00:17:44 have a superimposed on that a velocity
00:17:44 --> 00:17:47 which we call a peculiar motion, its own
00:17:47 --> 00:17:50 velocity. uh caused by local, you know,
00:17:50 --> 00:17:53 local edies in space or whatever uh that
00:17:53 --> 00:17:56 that might um move a galaxy towards us.
00:17:56 --> 00:17:58 It's the gravitational field that it's
00:17:58 --> 00:18:02 exposed to. Very much like um the the
00:18:02 --> 00:18:04 analog is always a river carrying you
00:18:04 --> 00:18:06 along. Uh and if you're in a rowbo, you
00:18:06 --> 00:18:08 can move relative to the river, but the
00:18:08 --> 00:18:09 river is always carrying you along.
00:18:09 --> 00:18:11 That's exactly what's happening with the
00:18:11 --> 00:18:13 Hubble flow, the the expansion of the
00:18:13 --> 00:18:15 universe. And these peculiar motions are
00:18:15 --> 00:18:17 superimposed on that, but they're much
00:18:17 --> 00:18:18 much less
00:18:18 --> 00:18:22 >> than the motion uh at those distances or
00:18:22 --> 00:18:24 look back times. It's much much less
00:18:24 --> 00:18:27 than the expansion flow of the universe.
00:18:28 --> 00:18:29 So no, there won't be anything hidden
00:18:30 --> 00:18:31 from us that's coming towards us. I
00:18:31 --> 00:18:33 don't think it's a interesting
00:18:33 --> 00:18:35 suggestion, but uh everything's moving
00:18:35 --> 00:18:37 away from us at this very high velocity
00:18:37 --> 00:18:39 at those distances.
00:18:39 --> 00:18:41 >> Of course. Um, Nick, if you want to
00:18:41 --> 00:18:43 check with us in a million years or so,
00:18:43 --> 00:18:45 we might have an alternative answer.
00:18:45 --> 00:18:47 >> Well, that's true. Uh, put that in your
00:18:47 --> 00:18:49 diary and we'll we'll uh I'll I'll mark
00:18:49 --> 00:18:51 it with an asterisk knowing that it's
00:18:51 --> 00:18:54 homework for a million years time.
00:18:54 --> 00:18:58 >> Yes, it's good. Um, and I'm really
00:18:58 --> 00:18:59 disappointed that the people who make
00:18:59 --> 00:19:06 diaries haven't gone ahead that far yet.
00:19:06 --> 00:19:08 >> Thanks, Nick. Um, probably not, I think,
00:19:08 --> 00:19:11 is the the answer. Um, but thanks for
00:19:11 --> 00:19:13 the question. Thanks to everyone who
00:19:13 --> 00:19:14 sent in questions. Keep them coming. You
00:19:14 --> 00:19:15 can do that via our website,
00:19:15 --> 00:19:18 spacenutspodcast.com, spacenuts.io,
00:19:18 --> 00:19:22 which has two options. The AMA tab at
00:19:22 --> 00:19:23 the top where you can send us text and
00:19:23 --> 00:19:27 audio or the send us your questions uh
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00:19:28 --> 00:19:30 home screens. Don't forget to tell us
00:19:30 --> 00:19:32 who you are and where you're from. And
00:19:32 --> 00:19:34 you can probably upload your audio
00:19:34 --> 00:19:36 questions on any device as long as
00:19:36 --> 00:19:38 you've got a microphone and mobile
00:19:38 --> 00:19:40 phones are perfect for this. Uh but a
00:19:40 --> 00:19:42 lot of people have home computers with
00:19:42 --> 00:19:45 mics built in, etc., etc., etc. Always
00:19:45 --> 00:19:48 happy to hear from you. Uh Fred, thanks
00:19:48 --> 00:19:50 so much. We're done with another
00:19:50 --> 00:19:52 episode. Jeez, we're them up.
00:19:52 --> 00:19:53 >> We are wrapping them up. Good to talk to
00:19:53 --> 00:19:56 you, Andrew. And we'll speak again soon.
00:19:56 --> 00:19:58 >> Indeed, we will. Professor Fred Watson,
00:19:58 --> 00:20:00 astronomer at large. And thanks to Hugh
00:20:00 --> 00:20:04 in the studio for collecting
00:20:04 --> 00:20:05 not much, but uh we thank him anyway.
00:20:06 --> 00:20:07 And from me, Andrew Dunley, thanks for
00:20:07 --> 00:20:09 your company. See you on the very next
00:20:09 --> 00:20:11 episode of Space Nuts. Bye-bye.
00:20:12 --> 00:20:13 >> Space Nuts.
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