SN350: Questions Time

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Hello, thanks for joining us.
This is Space Nuts. I'm Andrew Dunkle,

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your host, and it's so good
to have your company once again.

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And coming up on this episode,
it is all questions because it's episode three

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hundred and fifty, and that's when
we dedicate our show to the audience to

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nail down such questions as those of
stellar mass, black holes, our place

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in the universe, and where that
place might be in the future because it's

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moving. Is there a size limit
to rocky planets. We're going to look

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at expansion limits, expansion effects,
asteroids, space time, and photons.

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All questions coming from our vast audience
of nine here on Space Nuts. Hope

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you can hang around a while.
Dan Sack and Rad in Ternel ten nine

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Magnian sequenced Space Nuts three two two
one Space Nuts and actually report a bill

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good and joining me to discuss all
of that and much much more is Professor

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Fred Watson, a storm Er at
Large. Hello Fred, Hello Andrew,

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very good to be at large again. If I haven't caught you yet,

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not at all. We've got a
smashing program. It's there's so much to

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talk about today, so I think
we'll just hose straight in and get stuck

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into it. And our very first
question comes from none other than Hallo Space

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Nuts, Margin Burman Gorvyn here,
writer extraordinaire in many genres, and today

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we're crossing my strength in science fiction
with horror as we ask how close could

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a spacecraft with human beings aboard realistically
get to a stour mass black hole before

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all the inside our fried and or
linguinified, which I think sounds better than

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spaghettified, don't You can't wait to
hear the answer? Margin Burming Gorvine in

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Potomac, Maryland here over and act
linguinified. Yeah, yeah, with that

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or with that? Yeah that's not
bad? Um? Yeah, how close

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is too close? So I suppose
the answer is it depends? Uh,

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it does, doesn't it? Yeah? I am um so somewhere and here

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we go. This is the the
usual um tribute to one of my books,

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but I can't remember which one,
which Chat's five episodes? Sorry,

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I'm not naming any at least I
don't think I'm going to um. I

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did write about the event. Horizon
divers are a stellamass black hole, and

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I can't remember what it is,
but it's it's relatively compact, measured in

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kilometers if I remember rightly, But
the event horizons not really what would sort

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you out in you know, in
the answer to Martin's question, because yes,

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you'd be linguinified spaghettified. You probably
would even be result of fired as

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well, because you might end up
in bids when you got within a much

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closer distance. Um, So here
is a something I'm pulling out of my

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memory from only about four weeks ago. There is a there's a gas cloud

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which is currently orbiting the it's not
orbiting, it's passing by the supermassive black

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hole in the center of our galaxy. Now that's not a tellomass black hole,

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which is what Martin's asking about.
This is a three point six million

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stellar mass black hole. This,
this gas cloud is passing within a few

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trillion kilometers if I remember rightly,
of the black hole, and it is

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being spaghettified. It's been watched,
it's been observed to do that over quite

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a long period. Notwithstanding that a
few more million trillion kilometers there are stars

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happily in orbit around the supermassive black
hole. So I don't haven't done the

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calculation, Martin. It's probably conjecture
as to you know what, at what

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level do the tidal forces separating your
head and your feet start to become significant

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enough that they overcome the the you
know, the stomic forces which are holding

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your atomies together. And that's a
calculation that I haven't done. But it's

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even for a stellar mass black hole, it's probably not very far away.

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I think the title forces that you
would experience would would really start to make

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things uncomfortable, Okay, And which
one is the stella mass black hole?

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Again, in terms of the size
of black holes, it's the massive one

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star. Stella mass is one star, right, Okay, gotcha, hen's

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the name. Yes, sorry,
sorry, I'm I'm being lived there,

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But that's right. It's an object
of the order of the massive one star,

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which sometimes includes things up to twenty
or thirty times the mass of the

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song. But it's still not a
super massive black hole. And it's not

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the other thing that we've talked about
from Touch to Town. The intermediate mass

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black calls things of order a thousand
times the mass of the song, which

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which quite rare, we believe,
and very much unlike the ultra massive black

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hole that we talked about four weeks
ago, that's bigger than big. Just

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wait for the hypermassive black hole.
That's the next one to come up.

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Well, it could happen, couldn't
it? And did it? Could?

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You just never know these things,
these like we when we started the podcast

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and write through several episodes or several
years of episodes, we could only confirm

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there were two yes, moall and
large. Now we've got yeah, yeah,

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loads different, including that ultra massive
black hole that we talked about.

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That's sort of pushing the limits of
which we thought black holes could exist.

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We thought that couldn't exist. I
can't remember what it was. Was it

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thirty billion or thereabout? It was
some astronomical numbs a huge number. Yeah,

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yeah, yeah, it was amazing. Um. So the answer to

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Martin's question is, in real terms, you could get reasonably close, but

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not but not that close. Sorry
Martin, we haven't given you another for

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at all. We've just talked about. But reasonably close is what I think.

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Yeah, I don't think you'd want
to get you know, if it

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was at the center of the solar
system. I don't think you want to

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get much nearer than such an r
neptune. Sorry, your readers, so

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well, no one wants to get
hear that now. Okay, so Martin,

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that's a very loose answer to your
question, but it's a good question

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because you know, one day we
might be able to get out there and

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get close to one of these things, and you just really, you really

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didn't need to do your mathematics before
you lined yourself up. Bring it.

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Who came out of your space warp
ups? I mentioned the name and got

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too close. Yeah, all right, thanks Martin. Great to hear from

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you. Let's go to a text
question. This actually came in via email

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from Andrew. He says, I
love the show. I have a science

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question. Does our Sun move its
position as the planet's orbit? If so,

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by how much? Thanks? Andrew? Hit reply to respond. Now

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we'll just talk about that. Yeah, it's a great question, and the

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answer is yes, it does.
And so basically the bottom line here is

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that the Sun in a sense,
is not the center of the Solar system.

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The point at the center of the
Solar system is something called the Barry

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center, which is the sort of
it's like the center of gravity of the

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Solar System. So it includes not
just the Sun but also the planets,

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of which really only one counts in
this argument, and that's the planet Jupiter,

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which is, you know, the
most massive of the Solar System's planets.

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So, but the Barry center,
that's to say, this center of

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gravity does actually move around with respect
to the Sun, or should I say

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the Sun moves around with respect to
the Barrier center. And it's that process

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that actually allows us to detect the
planets of other stars. Because if you've

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got if you've got a object in
deep space, a star, you know,

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one hundred light years away, all
you can observe is its light and

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its spectrum. But what you can
see is it's velocity changing slightly as the

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planets pullets, you know, slightly
one way or the other. And you

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can actually disentangle how many planets there
are around at the star without being able

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to see any of them, just
by knowing how the star moves with respect

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to the barri center. It's that
movement that you can see reflected in the

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star's velocity. And in fact,
we can now detect motions of stars with

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an accuracy measured believe it or not, in centimeters per second. Rather than

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well the work I did, you
were doing well if you got down to

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a kilometer per second accuracy, but
meter per second accuracy has been attainable for

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a long time, but now people
are talking about sentimeter per second accuracy in

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the speed of a star that you
can detect if I remember rightly, the

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planet Jupiter changes the Sun's velocity by
around eleven meters per seconds, right to

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detect. Yeah, if to detect
a Jupiter sized planet in the same orbit

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as Jupiteres, but around another star
rather than the Sun, you would see

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motions of that star of eleven meters
per second as it moves with respect to

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the Barrit Center. Now, Andrew's
other part of his question was how much

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does it move? How much does
the Sun move with respect to the center

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of gravity of the Solar system,
And it's basically not much, but that

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Barry center does actually from time to
time it is outside the Sun rather than

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being within it. So you're talking
about the Sun moving by, you know,

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some fraction of its diameter. It
might be quite a large fraction.

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It's not millions of kilometers. It's
well, actually the Sun is one point

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formula kilometers in diameter, so it
might be millions of kilometers, but but

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you know, more likely to be
tens of hundreds of thousands. That's which

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means that the Barris center is for
the most part inside the Sun, but

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it does occasionally go outside when you
reckon. When you include the effect of

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all the planets that include Saturn as
well, it's one of the Jupiter.

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I suppose the other way to describe
the movement would be that that wobble we

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talk about when they're trying to detect
planets around other stars, that that's one

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of the mythos, isn't it.
Yeah, exactly what that wobble is the

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eleven kilometers per second in the place
of Jupiter el the song Dopler wobbles technique.

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It's called yeah, yeah, very
good. Thanks Andrew, hope you're

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doing well. Let's go on to
our next question. This comes from Tom

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in Ireland. He said, Hi, my brain hurts, please help.

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Paracetamol or iberprofen is very good.
For that time, thirteen point eight billion

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years ago, the universe began and
has been expanding ever since. How is

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it that we can see objects up
to twelve billion light years away in one

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direction and also in the opposite direction. If we are seeing these objects where

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they were twelve billion years ago,
which means they were twenty four billion years

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apart. How could they have originated
at the same point thirteen point eight billion

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years ago? Please help love the
show Tom in Ireland. I think he's

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getting his light years and his universal
age years mixed up. Possibly, No,

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it's it is. It's a confusing
thing because yeah, and your age

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years is a good point, because
we talk in terms of lookback times.

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That's the kind of usual phrase,
and so it's misleading to say Gallex is

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twelve billion light years away and unless
you qualify it by adding in the in

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the co moving coordinate system, and
not many people do, I know,

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I don't know. There you go, So the bottom it's better to talk

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in terms of look back times,
because that's the sort of fundamental thing.

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When you see an object in very
the very distant universe, it's seeing it

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as it was, maybe when the
universe was one point eight billion years old.

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If it's if it's got a twelve
billion year lookback time, but it's

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actual distance is much more than twelve
billion light years, because the universe has

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expanded by a huge amount since their
light left that object. So the the

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what you might call in fact,
it's got a name, it's called the

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proper distance would be something like thirty
maybe thirty five billion light years away because

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of the expansion of the universe.
But that's something that you can't actually measure

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in any way, that distance,
because all we see is the light that's

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reached us after it's twelve billion year
journey. And so it's more accurate to

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talk about look back time of four
billion years than to say a distance of

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a look back time of twelve billion
years, rather than a distance of twelve

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billion light years, unless you say
it's a co moving distance, which is

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the distance which doesn't account for the
expansion of the universe. Good grief kind

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of equates to the question we often
get about where is the center of the

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universe and where we are? Where
are we in it? Well, we

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are in it, that's rightly speaking. Yeah, so sorry, and Tom,

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I didn't really answer probably the address
your question about things being separated by

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twenty eight and sorry, twenty four
billion light years. And that's all that

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is saying, Yes, we see
things receding from us in different directions.

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And the Hubble law seems to work
everywhere whatever direction you're looking, and the

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Hubble law is the one that relates. It's this velocity of the velocity away

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from us of an object to its
distance. It's how we know that redshift

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equals distance in the you know,
standard cosmological model of the universe. So

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what what that is telling you is
that the universe, first of all,

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is extremely big. And we think
that when it kicked off within the first

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gazillions to the second, in fact, about tenth of minus thirty three of

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us and if I remember the number
rightly, it expanded very violently in this

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period we call the Age of inflation, which only lasted a few quintillions of

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a second, but blew up the
universe from the size of a p to

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the size of a galaxy. And
then the expansion sort of settled down.

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But that's how we think. That's
why we think the universe looks the same

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in all directions, even though it's
very very large and the distances separating objects

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is very very extreme. We think
at one time everything was very close together,

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and then it wasn't. And that's
why we she what was she today?

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Okay, Tom's headache is throbbing now, Yes, probably, Yeah.

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I go for asprints, actually you
know you do? Yeah, yeah,

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I just go around trying to find
willow trees and lick the bark. Okay,

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all right, I wondered what you
were doing. That's that's a natural

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pankiller. I didn't know that.
Hell, that's that's I think that's how

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aspurin was invented. Not sure something
like that. Yeah, willow is a

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natural has a natural painkilling property in
it. It does. Thank you,

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Tom. Great to hear from you. This is space Nuts with Andrew Duntley

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and Professor Fred. What's a space
nuts? Now? Fred to a regular

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contributor to our question answer session,
and it's Duncan from Weymouth. I think

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I'm pretty sure he'll tell me that's
where he's from. Hello, Duncan.

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Hear from Weymouth in the UK.
Another quick question. I know that Andrew

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likes hypothetical one, so here's one
that's been bugging me for a while.

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If you could get a huge mass
of rock together, say, well,

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I don't know, a hundred times
Jupiter's mass of solid rock in one place

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and put it in either they wore
a bit around a star. Would it

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form a really massive rocky planet?
Or is there an upper limits to how

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big or how massive a rocky planet
can be? Just interested to know and

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if it couldn't form a massive,
massive rocky planet, what would actually happen

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to that rock to prevent it becoming
a rocky planet. Would it somehow not

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be able to be bound together,
or would it melt or boil and form

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a gas or what would prevent that? Okay, keep up the good work

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and thanks for your efforts. Bye
bye, thank you. Duncan m I

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kind of become a type of belt
or an asteroid belt or something like that

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if it couldn't form a planet would
have to sort of break up like that?

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But how big is the limit?
That's they So, yeah, it's

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a really interesting question. And I
think the limit is imposed is imposed not

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by the physics of how big something
can be. It's more about how things

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evolve when planetary systems are formed.
So we think that rocky planets do evolved

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by the sort of silicon material in
the original dust and gas cloud that formed

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the Solar System. We think that
stuff all stuck together became solidified turned into

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rock. These bits are rock bashed
into one another, some stuck together,

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some didn't. But in the end
you got planets building into a sort of

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rocks building into planetismals and then to
protoplanets and eventually two planets. But this

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is all taking place within an environment
that is very very gasy. And if

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you form rocky cause that start getting
very big, you will also a mass

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gas you want just you don't want
just to create rock, you'll acret gas

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as well. And that's why we
think the gas giants are gas giants,

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because they grew big enough that they
not only collected more bits of rock,

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they actually collected very significant envelopes of
gas around them. And it sort of

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helped as well by them what we
call the frost line or the ice line

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in the Solar system, that region
which is between the orbits of Miles and

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Jupiter, where where ice actually forms
because the temperatures low enough. Yeah,

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and so that the you know,
the limits are more about the way you

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form planets rather than what could exist. Um, whether a hundred jupiter mass

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I mean a hundred jupiter mass solid, a hundred jupiter mass object is is

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actually a star because I think the
the mass linits for brown dwarfs, is

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is it thirteen jupiter mass is up
to about eighty I think in something in

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that range will produce deuterium burning and
become what's called a brown dwarf star.

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But if you get above that,
then you've got a dwarf star. Um

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So, but that's assuming it is
made of gas. I think that the

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physics present prevent you from forming a
rocky planet with anything like that kind of

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mass, because it would have created
gas rather than create just more rock.

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Okay, that's that's pretty good though. I think we are discovering rocky planets

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that are much much bigger than Earth. Yeah, that's sort of up to

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neptune mass. But they're called super
earths, so that yes, So what

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that's saying is that we we perhaps
haven't achieved that limit within the Solar System.

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Yeah. Well, in the scheme
of things, our rocky little world

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is actually one of the smaller ones, isn't it in real terms? Yeah,

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although it's hard to you know,
the bottom line is that we're not

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really yet able to detect all the
smaller planets that around stars because it's harder

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to detect them. You can do
and there are programs that that you do

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that. Gravitational lensings. Want transit
method lets you do it as well.

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But the and perhaps you know,
the Kepler and tests spacecraft have both contributed

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many objects which are small compared with
you know what we used to be finding,

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which were always the Jupiter of us. Things are bigger, so we

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are finding rocky planets. But there's
still I think, gaps in our knowledge

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because when I've got the technology yet
to define the smallest ones, so when

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we get that perfected, we might
find a whole bunch thinks that a smaller

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than the Earth as well. Yeah, okay, thanks Duncan. Always good

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to hear from you. Jim is
next. He's from something I can't pronounce,

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New Orleans. Yeah, New Orleans, it's Jim dear, Professor Watson,

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and mister Dunkley. I've been traveling
by car a lot in the past

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year and was able to catch up
on all your podcasts thus far, Blimy,

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I truly enjoy the show and look
forward to the next episode. Onto

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my question. Because the bodies in
the universe are accelerating at an ever increasing

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rate, eventually there will come a
time when space time will become impracticable or

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space travel will become impracticable, if
not impossible. What I mean is that,

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eventually, as a result of increasing
excel leration, the velocity at which

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galaxies and their component parts move through
the universe will attain a substantial percentage of

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the speed of light. If we
cannot build spacecraft that attain speeds greater than

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that substantial percentage of the speed of
light, then it seems that when a

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spaceship leaves the Earth's gravity, well, the Earth will become unreachable by the

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spaceship because the spaceship cannot catch up. Can this be right? There must

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be something that I'm missing. Thanks
for your thoughts. Have a great day,

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Jim. Yeah, that's I can
see where he's coming from. It

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is a quandary, And yes,
we have talked about the fact that as

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things expand, we're eventually just going
to be totally isolated in the universe.

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We won't be able to see anything
else, which is due to happen in

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a couple of days. But what
yeah, yeah, indeed, what's the

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what's the answer to Jim's quandity?
I think on the body actually, because

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yes, if we look into the
distant future, when the expansion has accelerated

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so that you know, you're talking
about a hugely greater expansion of space time

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than we have at the moment,
things will disappear beyond the horizon because the

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light that's leaving them now will never
catch up with the expansion of the universe,

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so we won't see them. And
that's the point that you were just

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making, Andrew, that we will
have a very lonely existence when you look

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a few trillion years perhaps down the
track, because there won't be anything other

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than the local group of galaxies visible. Maybe the local group will disappear as

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well. And I suppose what Jim's
question about the spacecraft really means is that

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if the spacecraft could get far enough
from the Earth so that it was being

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carried away from the Earth due to
the expansion of the universe by a velocity

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higher than the velocity of the spaceship
could have achieved, then yes, you're

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right, you will abs get back. You'd never never make it back.

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So yeah, it's an interesting conjecture, and the universe very different from the

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one we live in today than It's
a horrifying thought, though, isn't it.

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Let's go visit that rock. Oh
it's gone, yeah, and we

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can't get back. Not good,
thank you, Jim. On a similar

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kind of playing field, Paul in
Melbourne says there has been talked recently about

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the energy that causes the universe to
expand coming from black holes. If this

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is so, then wouldn't we see
the space time around or near a black

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hole expanding at a faster rate than
that further away from black holes, for

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example, between galaxies or that in
the spaces between the filaments of the cosmic

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web. Wouldn't the filaments of the
cosmic web be expanding faster? And it's

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pretat data. Yeah, I'm just
trying to remember what the mechanism wants that

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linked and quite get my head to
it that linked black holes with the dark

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energy, which is what, you
know, what is the thing that we

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think drives the expansion of the universe. Dark energy seems to be very much

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a property of space itself, a
uniform property that that's the same wherever you

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look. So Paul's question is is
an interesting one. So and I can't

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remember the exact link between the mechanisms
within black holes and the dark energy,

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because yes, you know, it's
an intuitive thought if if dark energy coming

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from black holes, then the region
around black holes should be expanding more than

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the region elsewhere. But we already
observe the fact that that doesn't happen.

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We do see space time distorted around
black holes. But that's due to their

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gravitational attraction. That's the standard general
relativity distortion of space time that we see,

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you know, whenever we find gravitational
lenses, for example. So,

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as I said, the point about
dark energy is, say it is a

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phenomenon that is a property of space. I would have to I'd have to

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look back at what I was reading
up on the mechanism that feeds the energy

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of black holes into the space around
them to be able to give an answer

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to pulse question. So I'm a
bit embarrassed that I can't do that.

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I mean, it was about well, it must have been at least two

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months ago when we talked about this. Yeah, I guess, so I

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don't remember the conversation. I just
yeah, I just can't recall it.

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Is it is that paper I don't
think has been refuted, the one that

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suggests that maybe black holes could provide
the origin of dark energy. And I

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wish I could there is a there's
a there's a point about it which I'm

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just not not able to recover at
the moment from the memory bikes. Yeah,

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I could have a quick look and
see if I can find the article,

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00:29:30.559 --> 00:29:34.920
but gosh, I don't know.
There's yeah, there's there's plenty of

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articles about it, So which one
do you pick? But yeah, it's

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00:29:38.039 --> 00:29:42.920
certainly got a lot of interest at
the time. Will continue. So we're

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00:29:42.920 --> 00:29:47.880
talking, we're talking mid February when
that first came. Yeah, so you

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00:29:47.960 --> 00:29:52.559
know it's fair enough that at our
age we've forgotten. I felt we remember

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00:29:52.599 --> 00:29:56.559
the was there? Yes, yes, indeed, So Paul, I might

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try and look at that again and
we might get back to if we don't

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00:30:00.519 --> 00:30:07.119
forget. Thanks entire conversation. I'll
put an asterisk next to his question.

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Follow up. All right, thank
you, Paul, Thanks for sending in

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00:30:10.880 --> 00:30:15.160
the question. This is Space Nuts
Andrew Duncley here with Professor Fred Watson.

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00:30:18.359 --> 00:30:26.559
Great Space Nuts. Okay Fred,
a few more questions before we wrap it

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00:30:26.680 --> 00:30:30.039
up. And this one comes from
Western Australia and our good friend Rusty,

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00:30:30.200 --> 00:30:34.039
actually, to be more specific,
Rusty's wife. Hello, Space Nuts.

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00:30:34.039 --> 00:30:40.039
It's Rusty and Donnybrook. My lovely
wife Ally came up with a question about

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00:30:40.920 --> 00:30:48.119
asteroids and she's seen a few movies
with asteroid fields in them and wonders if

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they're realistic, how close do they
get and how often do they collide,

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and I think I'm sure she'd love
your answer. Cheers, Thanks, Rusty,

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00:31:00.000 --> 00:31:04.960
we are Yeah, asteroids are not
an uncommon topic of questions either,

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00:31:06.759 --> 00:31:08.759
mainly the ones that are going to
hit us or near nar hit us.

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00:31:10.599 --> 00:31:14.440
But yeah, a different spin on
it, so to speaking, and a

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00:31:14.519 --> 00:31:18.759
good one too, great question,
because we you know, when you look

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00:31:18.799 --> 00:31:22.200
at depictions of the Solar System,
the main asteroid belt, which sits between

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the orbits of Males and Jupiter,
is always portrayed as being full of asteroids,

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asteroids everywhere in every direction. Whereas
the bottom line here is, you

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00:31:36.680 --> 00:31:41.400
know Douglas Adam's famous quotation, space
is big. You will believe how big

353
00:31:41.480 --> 00:31:45.200
it is. Anyway, it's big. What was it? You might think

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00:31:45.200 --> 00:31:47.519
it's a long way. You might
stret a long way down the street to

355
00:31:47.599 --> 00:31:52.680
the chemist. That's right. Anyway, there is a lot of space between

356
00:31:52.759 --> 00:31:59.799
them. So, as witnessed by
the fact that I can't remember how many

357
00:32:00.160 --> 00:32:06.759
is it must be this five.
About eight or nine spacecraft have gone through

358
00:32:06.839 --> 00:32:15.279
the asteroid belt, including Galileo Cassini, two Voyagers to two Pioneers New Horizons.

359
00:32:15.200 --> 00:32:20.799
They've all gone through the asteroid belt
and of course been completely unscathed.

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On having said that, the second
part of rust wife's question, I'm sorry

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I didn't catch your name, But
the second part is do they collide?

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And the answer is yes. From
time to time they do, which we

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see usually as a plume of material
coming from an asteroid that's being accidentally observed,

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00:32:45.920 --> 00:32:50.680
usually because since part of the field
of view of something else, so

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some nondescript asteroid will suddenly start looking
like a comet. It will get a

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00:32:53.640 --> 00:33:00.480
tale of material, a bit like
Demorphus did after it was clouted by the

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Dart spacecraft. So you get this
usually reasonably straight lined cloud of material which

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is interpreted as having been a collision
between two asteroids. We think we've even

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observed one in the planetary system of
another star. The star is Famulo.

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It's a bright star in our southern
skies, and over a number of years

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that's been observed to have an object
going around it. We covered this,

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00:33:30.039 --> 00:33:34.480
I think a year or so ago
Andrew, which was thought to be a

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planet. They gradually got fainter and
eventually disappeared, And the thinking is that

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what we actually were looking at was
the debris cloud from two large asteroids that

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00:33:45.799 --> 00:33:51.880
it collided. That collided because that
thing's vanished altogether now as the debris cloud

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00:33:52.079 --> 00:33:59.440
disperses, so they do collide relatively
rarely because the space between them is so

377
00:33:59.720 --> 00:34:02.119
it's big. Yeah, I mean, going back a few billion years,

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00:34:02.160 --> 00:34:06.240
it was probably a lot more collisions. There's a lot more stuff out there

379
00:34:06.319 --> 00:34:08.599
to hit each other in close proximity. In fact, that we give that

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00:34:08.760 --> 00:34:13.840
period a name, it's called the
Late Heavy bombardment about three point eight billion

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00:34:13.920 --> 00:34:16.800
years ago, when the place was
full of debris charging around and bashing into

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00:34:17.280 --> 00:34:22.679
other things, including Earth. Yeah, including Earth. That's right. Indeed,

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00:34:23.719 --> 00:34:30.320
Thanks Rusty and spouse. Let's get
let's go onto annex. Question from

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00:34:30.840 --> 00:34:37.719
Renny all right, this is ready
from West Hills, California, with another

385
00:34:37.880 --> 00:34:44.239
question. I'm trying to understand what
space time is made out and why it

386
00:34:44.440 --> 00:34:50.440
bends when it interacts with matter.
I envisioned space climb as an invisible energy

387
00:34:50.599 --> 00:34:54.800
force pushing against some object of matter, which is another form of energy,

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where they to find a balance,
which is gravity. Am I correct?

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Yes? And the answer to your
question is it's made up of space end

390
00:35:07.000 --> 00:35:10.519
time. Yeah, that's the trouble. Nobody really knows what space time is,

391
00:35:14.719 --> 00:35:20.039
but I can qualify that a little
bit further because whatever it is,

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00:35:20.239 --> 00:35:24.079
yeah, you know, we glibly
talk about the fabric of spacetime bending under

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00:35:24.400 --> 00:35:29.639
the action of mass. Renny is
quite right. It's really hard to get

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your head around that because back in
the eighteen eighties we got rid of the

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idea that there was an ether something
that actually permeated space and allowed light to

396
00:35:40.360 --> 00:35:45.159
pass through a medium that would transmit
light that got thrown out, and the

397
00:35:45.320 --> 00:35:51.639
consequence of that was actually the special
theory of relativity, which says that you

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00:35:51.719 --> 00:35:54.840
know you're in the speed of light
is the same everywhere because the experiments,

399
00:35:54.960 --> 00:36:00.280
the Mikolson Morley experiment as it was
called, to measure the ether relied on

400
00:36:00.400 --> 00:36:05.360
the fact that you should see the
speed of light changing depending on what direction

401
00:36:05.400 --> 00:36:08.320
you're moving through the ether. And
we're not moving through the ether, so

402
00:36:08.400 --> 00:36:13.760
the speed of light doesn't change.
And that then brings up special theory of

403
00:36:13.840 --> 00:36:22.920
relativity. So we really don't know
what it is. But I think you

404
00:36:22.079 --> 00:36:27.599
have to look at the big picture
here, because the big picture says,

405
00:36:27.760 --> 00:36:35.480
well, there are two sort of
pivotal theories on which we base our view

406
00:36:35.519 --> 00:36:42.719
of reality. General relativity, which
works incredibly well for things on a large

407
00:36:42.760 --> 00:36:47.039
scale and quantum mechanics, which works
incredibly well for things on a small scale.

408
00:36:47.519 --> 00:36:52.119
But the two are incompatible. They
don't sort of sit together, and

409
00:36:52.360 --> 00:36:59.119
that sparks back in Einstein's day.
Actually the quest for a theory of quantum

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00:36:59.199 --> 00:37:04.079
gravity that would allow us to unite
these two theories, which we're still looking

411
00:37:04.199 --> 00:37:12.880
for. But one of the themes
that I think is addressed by quantum gravitists,

412
00:37:12.920 --> 00:37:16.000
if I can put them that way, people theoretical physicists who work on

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00:37:16.119 --> 00:37:21.760
this. One of the themes is
that we're missing something, and what we're

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00:37:21.800 --> 00:37:29.119
missing is a more fundamental theory of
space and time that underpins what we see

415
00:37:29.400 --> 00:37:32.199
as space and time. In other
words, there might be something else that

416
00:37:32.960 --> 00:37:38.880
from which space and time emerge and
hence space time. Many quantum theorists in

417
00:37:38.960 --> 00:37:43.760
the last twenty years have proposed that, and most of the theories I mean

418
00:37:43.840 --> 00:37:47.159
string theories one of those. It's
that sort of idea that there's something there

419
00:37:49.199 --> 00:37:53.800
that underpins what we observe in relativity
and in quantum mechanics, and a kind

420
00:37:53.840 --> 00:38:01.440
of deeper version of reality which may
include additional dimensions. There is some recent

421
00:38:01.519 --> 00:38:05.840
work that's being done on this,
which we might talk about in coming weeks.

422
00:38:05.880 --> 00:38:13.719
Andrew, that once again highlights that
there might be this hidden reality beneath

423
00:38:13.800 --> 00:38:19.440
space and time, which how do
we probe it? That's the problem and

424
00:38:19.760 --> 00:38:22.639
the suggestions that are being put forward
by how we might deal with that in

425
00:38:22.760 --> 00:38:30.400
a real situation, how we might
actually try and peer underneath the gossom avail.

426
00:38:30.159 --> 00:38:36.360
It's not gossom avail, it's a
curse relativity. And on the other

427
00:38:36.440 --> 00:38:40.239
side, quantum mechanics, also known
as the banking industry. The banking industry

428
00:38:40.239 --> 00:38:44.880
has got that as well as different
realities. In fact, yes, I

429
00:38:44.960 --> 00:38:49.039
think there are many places in the
world where you can put to different realities.

430
00:38:50.199 --> 00:38:53.440
Yeah, indeed, thank you,
Renny, and hope that helped somewhat

431
00:38:53.920 --> 00:39:00.760
now adequately. Now, finally we'll
go to David, who is from Huntsville,

432
00:39:00.800 --> 00:39:04.480
Alabama. First of all, I'm
a huge fan of the show and

433
00:39:04.519 --> 00:39:08.079
appreciate what you guys do to put
new wrinkles in my brain. I look

434
00:39:08.119 --> 00:39:13.320
forward to each Thursday for my space
nuts fixed. My question is if a

435
00:39:13.480 --> 00:39:19.960
photon does not experience time after it's
been emitted, and the universe is expanding

436
00:39:20.039 --> 00:39:23.960
greater than the speed of light,
assuming the photon has an unimpeded line straight

437
00:39:24.039 --> 00:39:29.119
towards the edge of the universe.
Is the photon essentially trapped in time at

438
00:39:29.239 --> 00:39:32.519
that point? Thanks keep up the
great work kind of relates to a question

439
00:39:32.599 --> 00:39:37.519
we had earlier. It does yet, and it presupposes the universe as an

440
00:39:37.639 --> 00:39:45.840
edge, which we don't think it
has. We don't know what it's got

441
00:39:45.880 --> 00:39:51.079
will beget us an edge. It's
got a banking industry surrounding it, a

442
00:39:51.239 --> 00:39:59.039
pique veil. So if but if
the photon, you know, to the

443
00:39:59.119 --> 00:40:02.480
photons always traveling through the universe at
the speed of light. Now, the

444
00:40:02.639 --> 00:40:12.400
fact that it's the source of the
photon and its destination are separating, are

445
00:40:12.480 --> 00:40:15.920
being separated by the expansion of the
universe greater than the speed of light,

446
00:40:16.719 --> 00:40:21.840
doesn't matter to the photon. It
just keeps ongoing. The fact that its

447
00:40:21.920 --> 00:40:25.320
target is moving away from it faster
than it's ever going to get there is

448
00:40:25.360 --> 00:40:30.480
not a concern to the photon.
It will still not experience the passage of

449
00:40:30.559 --> 00:40:35.159
time, which is exactly what David
said. That's what we think is the

450
00:40:35.280 --> 00:40:42.199
case. We'll just keep going forever. I suppose, in a sense it's

451
00:40:42.480 --> 00:40:47.000
the scenario that he he mentioned that
it will just keep on passing through space

452
00:40:47.880 --> 00:40:52.679
and infinitem because it's destination is not
good. He is always going to be

453
00:40:52.800 --> 00:41:00.719
further away that it will reach until
the big rip an escape, yeah maybe,

454
00:41:00.559 --> 00:41:05.559
or if there's a big rip,
there'll be tidal forces beyond imagination that

455
00:41:05.599 --> 00:41:10.119
would probably disturb everything as it.
Yes, that's the big rip. There's

456
00:41:10.159 --> 00:41:14.920
got consequences that we can't really envisage
it at the moment, but it's definitely

457
00:41:15.000 --> 00:41:20.039
not nice and it reminds me of
that famous song I'm a Photon and I'm

458
00:41:20.119 --> 00:41:22.480
okay, I Glow all day and
I Glow all night and I Glow all

459
00:41:22.559 --> 00:41:30.719
day stealing from Monty Python. Yeah, not quite, but nearly works as

460
00:41:30.760 --> 00:41:37.760
well as the original Lumberjack song.
Thank you, David. It's so great

461
00:41:37.800 --> 00:41:40.039
to hear from you, and thanks
to everyone who's sending questions. It's nice

462
00:41:40.039 --> 00:41:45.159
to fill an episode with audience questions. And we've got a whole fresh batch

463
00:41:45.280 --> 00:41:47.480
like one minute before we started,
so that was that was good, and

464
00:41:47.559 --> 00:41:52.519
that's why some of them sort of
caught us out of left field because we

465
00:41:52.679 --> 00:41:59.000
did what we usually do and went
in totally unprepared. Sometimes works, So

466
00:41:59.480 --> 00:42:00.840
if you do have a question for
us, of course, send it to

467
00:42:01.000 --> 00:42:05.119
us, because that's what it's all
about. We love to interact with you

468
00:42:05.400 --> 00:42:08.239
and we love to hear your voices. So where you can record through our

469
00:42:08.280 --> 00:42:13.159
website, space nuts podcast dot com
or space nuts dot io. Click on

470
00:42:13.239 --> 00:42:15.719
the AMA link and you can record
a question there, or send us a

471
00:42:15.760 --> 00:42:19.400
text question, or you can just
hit the tab on the right hand side

472
00:42:19.440 --> 00:42:22.519
at the home page send us your
voice message. And as long as you've

473
00:42:22.519 --> 00:42:27.239
got a smart device or a computer
or something dumber than that that's got a

474
00:42:27.320 --> 00:42:30.159
microphone, you can send us a
question. But we're taking text and audio

475
00:42:30.280 --> 00:42:35.599
questions all the time. The more
the merrier. And yes, don't forget

476
00:42:35.599 --> 00:42:38.760
the hypotheticals. I love those hypotheticals. Fred, we're wrapping it up for

477
00:42:38.880 --> 00:42:45.039
you yet another. It's a milestone. It is actually three hundred and fifty.

478
00:42:45.280 --> 00:42:47.559
Kind of let that slip through to
keep it. I'll believe it.

479
00:42:47.960 --> 00:42:52.559
Yeah, fifty three hundred and fifty. Oh my gosh, it seems like

480
00:42:52.760 --> 00:42:57.559
only six months ago we did episode. Probably a year ago we did episode

481
00:42:57.639 --> 00:43:00.920
three hundred. That's a bit,
wouldn't it, Yes, that will be

482
00:43:00.079 --> 00:43:07.920
I have to be near a year
would yes? That's a calculation there the

483
00:43:07.000 --> 00:43:15.599
words we should get a life really
come to by. Maybe we should thank

484
00:43:15.679 --> 00:43:19.800
you Fred as always good good to
tell Andrew take care all right, We'll

485
00:43:19.840 --> 00:43:22.639
catch you soon. Fred Watson,
astronomer at large part of the team here

486
00:43:22.800 --> 00:43:29.199
adds Space Nuts and back at Space
Nuts HQ, we say thanks to Hugh

487
00:43:29.440 --> 00:43:34.599
for reasons we cannot comprehend, but
anyway, thank you anyway, and from

488
00:43:34.639 --> 00:43:37.840
me Andrew Dunkley, thanks for joining
us each and every weekend for this latest

489
00:43:37.880 --> 00:43:42.760
episode. We'll catch you on the
very next one on Space Nuts. Bye

490
00:43:42.800 --> 00:43:50.519
bye. You'll be listening to the
Space Nuts podcast, available at Apple Podcasts,

491
00:43:50.760 --> 00:43:55.079
Google Podcasts, Spotify, iHeart Radio, or your favorite podcast player.

492
00:43:55.320 --> 00:44:00.519
You can also stream on demand at
bides dot com. This is been another

493
00:44:00.599 --> 00:44:02.519
quality podcast production from sites dot com.