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

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Hi there, This is Space Nuts
Q and A. My name is Andrew

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Dunkley. Great to have your company
coming up. On this episode, we'll

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answer questions from Steve, Gus and
Nick. Steve and gusso are sort of

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focused on the same thing gravity.
Steve wants to know if it can exist

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without mass, and Gus is talking
about gravity and energy and what's the relationship.

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And Nick is asking about galaxy movements
and are any moving towards us that

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

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yet, but we'll see if we
can tackle all of that on this episode

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of Space Nuts. Fifteen seconds guidance
in Channel ten nine ignition sequence Space Nuts

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or three two one Space Nuts can
I reported Neil Good. Here he is

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again, Professor Fred. What's a
hello? Fred? Hello? Hello?

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How are you doing now? I'm
doing the same as it was before.

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How about you? Well, I'm
still doing the same as it was before.

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Yes, that's right. I hope
to be doing the same again very

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soon. Yes, indeed, yes, Shall we just sort of muck in

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and get these questions sorted out?
It was like a couple of weeks ago

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we had gravity questions coming in thick
and fast, no black hole questions,

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but today it's gravity questions. And
first our first one comes from Steve.

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I go to the Steve on promm. We'll enjoy your show. Recently,

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you've read an article implying that gravity
could be possible without mess, and I'm

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wondering if that would be alternative explanation
two two dark matter and to wand you

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have enough makes it very clearly anyway, all right, Steve, thanks for

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the question gravity without mass. Well, I doubt that we can turn to

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the Catholic Church because they do have
mass, but terrible. It's an interesting

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question, though, it is.
And so yeah, my reading on this,

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excuse me, is yes, that's
correct. So actually there's a nice

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thread about this on Reddit if anybody
looks at that website. And well I

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love Reddit, yeah really, well
I do remember my one of my sons

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was an absolute Reddit fiend at one
time. He was very much a Reddit

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fan. Now, so that's how
I was aware of it, but I

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hadn't been a great user of Reddit. But the bottom line, excuse me,

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is, and this is the way
is phrased in this particular conversation.

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If you increase the temperature of an
object, and they take a planet in

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this case, and in fact,
I might just read it because this kind

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of is quite interesting. Take your
Neptune. You'd take your neptunean planet something

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the size of Neptune, raise the
temperature by three hundred degrees calving instantly.

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Now, the massive neptune is about
tenth to twenty six kilograms, and if

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we roughly assume all its hydrogen,
it corresponds to about six times tenth to

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fifty two particles of hydrogen. It's
the thermal energy is roughly given by an

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equation they're equal, which leads to
an increase in thermal energy of deaded and

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it's a large number of duels.
Actually it's a small number of duels.

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It's ok times six times tenth of
minus fifty two times three hundred duels,

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which if you then convert that So
what this is saying is you warm up

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a planet, you get an increase
in the thermal energy of that planet.

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You can then use equals mc square
to convert that thermal energy into mass,

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and in this case it comes out
to be something like three times ten to

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fifteen kilograms, which is a lot, but is not very much in comparison.

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With a planet, but that does
mean that adding energy to something will

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increase its gravitational mass. Now,
the Steve's sort of, you know,

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next step in the argument from that
is whether that could be misleading us in

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the idea of dark matter and things
of that sort. And I can't really

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get my head around how that would
work. He mentioned moms as well modified

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Newtonian dynamics, because my understanding is
that everybody who looks at these particular problems,

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what is dark matter, what is
dark energy? They take into account

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everything I've read some of the papers
on this and so things like you know,

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gravitational gravitational influence of pure energy,
and in this case we're talking about

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heat energy that is likely to be
something that would be already in the equations.

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So I don't think it's the answer, but it's a really interesting suggestion

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and interesting thing to think about.
So so thank you very much, Steve.

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Yeah, indeed just made me wonder
are we increasing Earth gravity because we're

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heeding the planet up? Yep,
that's probably right that I mean, the

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example that I just read out was
about three hundred three hundred degrees calvin an

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instant increase in that we're talking about
one or two degrees kelvin, but which

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makes a big difference to this atmosphere, but probably not that much difference to

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its gravitational potential. Okay, so
the answer is yes, gravity can exist

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without mass, but it's probably not
a major factor. Is that fair enough?

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Yes? That is right. I
have just been dragging through my memory

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andrew something else that's sort of vaguely
related to this, which is the We

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haven't this name, but we did
talk about it a while ago, google

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blitz. Do you know what a
google blitz is? Look, I've heard

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this before, No, remind me? Yeah? So's it? Basically is

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a black hole made of light and
Wikipedia says it's a concentration of heat,

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light, or radiation so intense that
its energy forms an event horizon and becomes

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self trapped. In other words,
if enough radiation is aimed into a region

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of space, the concentration of energy
can warp space time so much that it

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creates a black hole. It's a
black hole as a black hole whose original

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mass energy was in the form of
radiant energy rather than matter. Now,

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there is a paper that was published
in twenty twenty four that concludes that a

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phenomenon like this cannot occur in any
realistic scenario within our universe. So google

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blitz is are a theoretical entity that
are not I thought not to occur in

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nature. But it is a similar
thing, isn't it. Basically it's a

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it's a black hole made of energy. Yeah, wow, that's really interesting.

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I'll tell you something else that does
exist is a Google scriber. So

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I've got one of those, how
have you? Yeah, there is Langen

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German. Hold it up, okay, google scriber, Google scriber. Yes,

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you know what German is. You
know the German is for pencil.

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I probably did once, but I
don't know. That's blastiff, it's probably

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I only I know did languages at
high school, and I was very good

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at them, and I should have
probably pursued that somewhere along the line,

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but German stuck with me. Some
of the references I still remember today.

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Someone's going to correct me now because
I've probably bug it up. That ye

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ansociation anyway, that's all right,
just showing off now. No, it's

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a sign of your character that I
was unaware of, Andrew, I am

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curiously. I never joined Lerman at
school. I never learned German at school.

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But when I was fourteen, I
went on the school exchange to Germany,

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which was barbs because I wasn't studying
German. But that was my first

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overseas visit, of course, from
the United Kingdom, and so I've spent

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the however many years, it is
sixty odd years since then trying to learn

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German. And yeah, yeah,
look, I'm so jealous of students in

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countries like the United States, in
the UK, in Europe because they get

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to do excursions to other countries.
In Australia, we got to do excursions

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to Sydney and Canberra. I mean, come on, that was it.

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Yeah, that was as good as
it got for us. Yeah, I

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mean these days they get to go
to New Zealand once in a while,

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but yeah, we're so far from
everywhere. It's just not easy. Although

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my son did go to get to
do a couple of weeks in Japan through

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high school, so there are a
few options these days. This is Space

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Nuts Andrew Dunkley here with Professor Fred
Watson. Let's take a little break from

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00:14:00.080 --> 00:14:03.000
based nuts. We better keep moving, Thank you, sir. Let's get

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a question from Gus. Hello,
Professor Fred and Andrew. This is Gus

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Iverson from Issaquah, Washington. I
sent in a question for you guys previously,

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and you thought I was in Western
Australia. Yes, I've been thinking

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about gravity today and it came to
my mind that if energy and mass are

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equivalent, then essentially shouldn't energy also
create gravity at some level? I'm not

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sure if this is a related question
or an extension or a separate question.

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Though. Additionally, if a body
of any size is generating or it has

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mass and it is generating a gravitational
field, does not that field itself have

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energy and mass? And would that
field not create additional gravity by its simple

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existence? So if that's the case, or even kind of the case,

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my question is where does the energy
and mass go? If or I have

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no idea where to go with this? Thank you. I love the show

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and appreciate being able to ask questions. Thank you, Gus. That sounded

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very much like something from Catch twenty
two apples or tomatoes, I would try

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to I don't know, but it
sounded a bit like that gravity plus energy,

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body plus mass plus gravity equals energy. But then does that add mass

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which adds to gravity. Think that's
what he was trying to Yeah, that's

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right. So you've got to you
know, the whole thing gets completely out

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of hand because everything's got gravity.
I think. So the first part of

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what Jos was saying is what we've
just been talking about. You know,

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if you nevalance have energy and mass
and gravitation, you're gonna be I probably

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have to be careful with the words
gravitational. Gravitation is a potential an object

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in a gravitational field has potential energy, so it does have energy. But

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I kind of need to take this
one and notice actually did give me notice,

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Andrew, but I didn't have time
to really look further into it.

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But I think I think there's a
I think there's a stumbling block somewhere in

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that argument, which is probably that
gravitational energy is an energy that's convertible to

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mass. But I need to get
my thoughts clear on that, which they

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are at the moment. So Gus, thank you for a very tricky question

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which I might think a little bit
more about. Okay, perhaps we will

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revisit it in a future episode of
Space not Q and A. I put

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a put a homework market next to
it. That's what I'm just doing that.

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I'm doing it. You're doing it
in your Google. I'm using a

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red Google sscriber. Okay, I
don't know what the German word for ready

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is. Probably do it translate.
That's what what you are. I don't

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have to look at her, so
Gus, don't know, We don't know.

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Maybe possibly could be don't yeh,
but don't don't yet know. I

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like that. Let's to the final
question. We'll get back to you Gus

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at some stage in Western Australia or
it could be the United States. But

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now we've got a question from oh
just by coincidence from New Zealand again high

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team, Amazing podcast. Which one
are you talking about now? I have

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been listening since your early days and
have always looked forward to new uploads.

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My question is around the discovery of
early galaxies from the James web Space Telescope.

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Is it possible for earlier galaxies to
be traveling towards us that are currently

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out of reach, filling with potentially
nothing, filling where potentially nothing was in

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view before. If possible, would
the light be compressed? How would the

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instruments deal with that? Hope that
makes sense? Cheers Nick from Auckland,

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New Zealand. I My brain just
went, well, I suppose it's possible,

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but how do we prove it until
it happens? Yes, so couple

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of things in here, Thanks Nick, A great question. The last bit

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about light being compressed, so and
in a way that's you know, that's

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quite a nice way of putting it. So anything that comes towards you that's

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emitting light, it's like, will
be blue shifting. In other words,

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its wavelength will get shorter, and
that's saying it's compressed is pretty well,

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

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the the good old ambulance siren or
fire engine siren or whatever it is coming

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towards you, which compresses the sound
waves and the result is an increase in

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pitch, which corresponds to a shortening
of wavelength. So that's standard physics.

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We can detect by the Doppler shift
anything coming towards us, by the fact

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that its light is shifted towards the
blue end of the spectrum. But the

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first bit of the question about galaxies
earlier galaxies traveling towards us. When we

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think about galaxies, we have two
different velocities involved. One is the velocity

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of a galaxy as it's carried along
by the expansion of the universe, and

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that is what we measure as a
red shift. The expansion of the universe

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is carrying galaxies away from us,
and so their light is being red shifted.

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And by the time you get to
these really early galaxies where you're looking

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back almost the whole age of the
universe, the red shift is very considerable.

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It's a fact of thirteen or fourteen
something like that. We give in

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the name Z. The red shift
is about fourteen, so a big part.

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No, that's not true. That's
me confusing the age with the red

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shift. Forget that bit. But
the numbers quite high. The red shifts

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are probably five or six or something
like that. But it's still a high

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level of the light being stretched out
by the expansion of the universe. So

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that's one velocity. But galaxies can
have a superimposed on that, a velocity

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which we call a peculiar motion,
its own velocity caused by local you know,

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local eddies in space or whatever that
might move a galaxy towards us.

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It's the gravitational field that it's exposed
to. Very much like the analog is

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always a river carrying you along,
and if you're in a rowboat, you

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can move relative to the river,
but the river's always carrying you along.

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That's exactly what's happening with the Hubble
flow, the expansion of the universe,

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and these peculiar motions are super imposed
on that, but they're much much less

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than the motion those distances or moot
back times. It's much much less than

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the expansion flow of the universe.
So no, there won't be anything hidden

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from us that's coming towards us.
Think it's an interesting suggestion, but everything's

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moving away from us at this very
high velocity at those distances. Of course,

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Nick, if you want to check
with us in a million years or

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so, we might have an alternative
answer. Well, that's true, put

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that in your diary of well,
I'll mark it with a US risk,

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knowing that it's hard work for a
million years time. Yes, it's good.

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I'm really disappointed that the people who
make diaries haven't gone ahead that far

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yetbsolutely. Thanks Nick, Probably not, I think is the answer. Thanks

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for the question. Thanks to everyone
who's sending questions. Keep them coming.

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You can do that via our website
spacenotspodcast dot com, space nuts dot io,

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00:22:47.079 --> 00:22:51.400
which has two options, the AMA
tab at the top where you can

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00:22:51.440 --> 00:22:56.160
send us text and audio, or
the send us your questions button on the

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right hand side of our home screens. Don't forget to tell us who you

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are and where you're from, and
you can probably upload your audio questions on

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00:23:03.559 --> 00:23:07.559
any device as long as you've got
a microphone, and mobile phones are perfect

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for this, but a lot of
people have home computers with Mike's built in

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00:23:11.920 --> 00:23:15.039
et cetera, et cetera, et
cetera. Always happy to hear from you,

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Fred, Thanks so much. We've
done with another episode. We're wrecking

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them up, were racking them up. Good to talk to you, Andrew,

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and we'll speak again too, Indeed
we will. Professor Fred Watson,

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Astronomer at Large. And thanks to
Hue in the studio for collating. Not

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much, but we thank him anyway. And from me Andrew Dunkley, thanks

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for your company. See you on
the very next episode of Space Nuts.

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Bie spaces. You'll be listening to
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stream on demand at bides dot com. This has been another quality podcast production

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from nights dot com.