Hello, thanks for joining us. This is Space Nuts. I'm Andrew Dunkle,
your host, and it's so good to have your company once again.
And coming up on this episode, it is all questions because it's episode three
hundred and fifty, and that's when we dedicate our show to the audience to
nail down such questions as those of stellar mass, black holes, our place
in the universe, and where that place might be in the future because it's
moving. Is there a size limit to rocky planets. We're going to look
at expansion limits, expansion effects, asteroids, space time, and photons.
All questions coming from our vast audience of nine here on Space Nuts. Hope
you can hang around a while. Dan Sack and Rad in Ternel ten nine
Magnian sequenced Space Nuts three two two one Space Nuts and actually report a bill
good and joining me to discuss all of that and much much more is Professor
Fred Watson, a storm Er at Large. Hello Fred, Hello Andrew,
very good to be at large again. If I haven't caught you yet,
not at all. We've got a smashing program. It's there's so much to
talk about today, so I think we'll just hose straight in and get stuck
into it. And our very first question comes from none other than Hallo Space
Nuts, Margin Burman Gorvyn here, writer extraordinaire in many genres, and today
we're crossing my strength in science fiction with horror as we ask how close could
a spacecraft with human beings aboard realistically get to a stour mass black hole before
all the inside our fried and or linguinified, which I think sounds better than
spaghettified, don't You can't wait to hear the answer? Margin Burming Gorvine in
Potomac, Maryland here over and act linguinified. Yeah, yeah, with that
or with that? Yeah that's not bad? Um? Yeah, how close
is too close? So I suppose the answer is it depends? Uh,
it does, doesn't it? Yeah? I am um so somewhere and here
we go. This is the the usual um tribute to one of my books,
but I can't remember which one, which Chat's five episodes? Sorry,
I'm not naming any at least I don't think I'm going to um. I
did write about the event. Horizon divers are a stellamass black hole, and
I can't remember what it is, but it's it's relatively compact, measured in
kilometers if I remember rightly, But the event horizons not really what would sort
you out in you know, in the answer to Martin's question, because yes,
you'd be linguinified spaghettified. You probably would even be result of fired as
well, because you might end up in bids when you got within a much
closer distance. Um, So here is a something I'm pulling out of my
memory from only about four weeks ago. There is a there's a gas cloud
which is currently orbiting the it's not orbiting, it's passing by the supermassive black
hole in the center of our galaxy. Now that's not a tellomass black hole,
which is what Martin's asking about. This is a three point six million
stellar mass black hole. This, this gas cloud is passing within a few
trillion kilometers if I remember rightly, of the black hole, and it is
being spaghettified. It's been watched, it's been observed to do that over quite
a long period. Notwithstanding that a few more million trillion kilometers there are stars
happily in orbit around the supermassive black hole. So I don't haven't done the
calculation, Martin. It's probably conjecture as to you know what, at what
level do the tidal forces separating your head and your feet start to become significant
enough that they overcome the the you know, the stomic forces which are holding
your atomies together. And that's a calculation that I haven't done. But it's
even for a stellar mass black hole, it's probably not very far away.
I think the title forces that you would experience would would really start to make
things uncomfortable, Okay, And which one is the stella mass black hole?
Again, in terms of the size of black holes, it's the massive one
star. Stella mass is one star, right, Okay, gotcha, hen's
the name. Yes, sorry, sorry, I'm I'm being lived there,
But that's right. It's an object of the order of the massive one star,
which sometimes includes things up to twenty or thirty times the mass of the
song. But it's still not a super massive black hole. And it's not
the other thing that we've talked about from Touch to Town. The intermediate mass
black calls things of order a thousand times the mass of the song, which
which quite rare, we believe, and very much unlike the ultra massive black
hole that we talked about four weeks ago, that's bigger than big. Just
wait for the hypermassive black hole. That's the next one to come up.
Well, it could happen, couldn't it? And did it? Could?
You just never know these things, these like we when we started the podcast
and write through several episodes or several years of episodes, we could only confirm
there were two yes, moall and large. Now we've got yeah, yeah,
loads different, including that ultra massive black hole that we talked about.
That's sort of pushing the limits of which we thought black holes could exist.
We thought that couldn't exist. I can't remember what it was. Was it
thirty billion or thereabout? It was some astronomical numbs a huge number. Yeah,
yeah, yeah, it was amazing. Um. So the answer to
Martin's question is, in real terms, you could get reasonably close, but
not but not that close. Sorry Martin, we haven't given you another for
at all. We've just talked about. But reasonably close is what I think.
Yeah, I don't think you'd want to get you know, if it
was at the center of the solar system. I don't think you want to
get much nearer than such an r neptune. Sorry, your readers, so
well, no one wants to get hear that now. Okay, so Martin,
that's a very loose answer to your question, but it's a good question
because you know, one day we might be able to get out there and
get close to one of these things, and you just really, you really
didn't need to do your mathematics before you lined yourself up. Bring it.
Who came out of your space warp ups? I mentioned the name and got
too close. Yeah, all right, thanks Martin. Great to hear from
you. Let's go to a text question. This actually came in via email
from Andrew. He says, I love the show. I have a science
question. Does our Sun move its position as the planet's orbit? If so,
by how much? Thanks? Andrew? Hit reply to respond. Now
we'll just talk about that. Yeah, it's a great question, and the
answer is yes, it does. And so basically the bottom line here is
that the Sun in a sense, is not the center of the Solar system.
The point at the center of the Solar system is something called the Barry
center, which is the sort of it's like the center of gravity of the
Solar System. So it includes not just the Sun but also the planets,
of which really only one counts in this argument, and that's the planet Jupiter,
which is, you know, the most massive of the Solar System's planets.
So, but the Barry center, that's to say, this center of
gravity does actually move around with respect to the Sun, or should I say
the Sun moves around with respect to the Barrier center. And it's that process
that actually allows us to detect the planets of other stars. Because if you've
got if you've got a object in deep space, a star, you know,
one hundred light years away, all you can observe is its light and
its spectrum. But what you can see is it's velocity changing slightly as the
planets pullets, you know, slightly one way or the other. And you
can actually disentangle how many planets there are around at the star without being able
to see any of them, just by knowing how the star moves with respect
to the barri center. It's that movement that you can see reflected in the
star's velocity. And in fact, we can now detect motions of stars with
an accuracy measured believe it or not, in centimeters per second. Rather than
well the work I did, you were doing well if you got down to
a kilometer per second accuracy, but meter per second accuracy has been attainable for
a long time, but now people are talking about sentimeter per second accuracy in
the speed of a star that you can detect if I remember rightly, the
planet Jupiter changes the Sun's velocity by around eleven meters per seconds, right to
detect. Yeah, if to detect a Jupiter sized planet in the same orbit
as Jupiteres, but around another star rather than the Sun, you would see
motions of that star of eleven meters per second as it moves with respect to
the Barrit Center. Now, Andrew's other part of his question was how much
does it move? How much does the Sun move with respect to the center
of gravity of the Solar system, And it's basically not much, but that
Barry center does actually from time to time it is outside the Sun rather than
being within it. So you're talking about the Sun moving by, you know,
some fraction of its diameter. It might be quite a large fraction.
It's not millions of kilometers. It's well, actually the Sun is one point
formula kilometers in diameter, so it might be millions of kilometers, but but
you know, more likely to be tens of hundreds of thousands. That's which
means that the Barris center is for the most part inside the Sun, but
it does occasionally go outside when you reckon. When you include the effect of
all the planets that include Saturn as well, it's one of the Jupiter.
I suppose the other way to describe the movement would be that that wobble we
talk about when they're trying to detect planets around other stars, that that's one
of the mythos, isn't it. Yeah, exactly what that wobble is the
eleven kilometers per second in the place of Jupiter el the song Dopler wobbles technique.
It's called yeah, yeah, very good. Thanks Andrew, hope you're
doing well. Let's go on to our next question. This comes from Tom
in Ireland. He said, Hi, my brain hurts, please help.
Paracetamol or iberprofen is very good. For that time, thirteen point eight billion
years ago, the universe began and has been expanding ever since. How is
it that we can see objects up to twelve billion light years away in one
direction and also in the opposite direction. If we are seeing these objects where
they were twelve billion years ago, which means they were twenty four billion years
apart. How could they have originated at the same point thirteen point eight billion
years ago? Please help love the show Tom in Ireland. I think he's
getting his light years and his universal age years mixed up. Possibly, No,
it's it is. It's a confusing thing because yeah, and your age
years is a good point, because we talk in terms of lookback times.
That's the kind of usual phrase, and so it's misleading to say Gallex is
twelve billion light years away and unless you qualify it by adding in the in
the co moving coordinate system, and not many people do, I know,
I don't know. There you go, So the bottom it's better to talk
in terms of look back times, because that's the sort of fundamental thing.
When you see an object in very the very distant universe, it's seeing it
as it was, maybe when the universe was one point eight billion years old.
If it's if it's got a twelve billion year lookback time, but it's
actual distance is much more than twelve billion light years, because the universe has
expanded by a huge amount since their light left that object. So the the
what you might call in fact, it's got a name, it's called the
proper distance would be something like thirty maybe thirty five billion light years away because
of the expansion of the universe. But that's something that you can't actually measure
in any way, that distance, because all we see is the light that's
reached us after it's twelve billion year journey. And so it's more accurate to
talk about look back time of four billion years than to say a distance of
a look back time of twelve billion years, rather than a distance of twelve
billion light years, unless you say it's a co moving distance, which is
the distance which doesn't account for the expansion of the universe. Good grief kind
of equates to the question we often get about where is the center of the
universe and where we are? Where are we in it? Well, we
are in it, that's rightly speaking. Yeah, so sorry, and Tom,
I didn't really answer probably the address your question about things being separated by
twenty eight and sorry, twenty four billion light years. And that's all that
is saying, Yes, we see things receding from us in different directions.
And the Hubble law seems to work everywhere whatever direction you're looking, and the
Hubble law is the one that relates. It's this velocity of the velocity away
from us of an object to its distance. It's how we know that redshift
equals distance in the you know, standard cosmological model of the universe. So
what what that is telling you is that the universe, first of all,
is extremely big. And we think that when it kicked off within the first
gazillions to the second, in fact, about tenth of minus thirty three of
us and if I remember the number rightly, it expanded very violently in this
period we call the Age of inflation, which only lasted a few quintillions of
a second, but blew up the universe from the size of a p to
the size of a galaxy. And then the expansion sort of settled down.
But that's how we think. That's why we think the universe looks the same
in all directions, even though it's very very large and the distances separating objects
is very very extreme. We think at one time everything was very close together,
and then it wasn't. And that's why we she what was she today?
Okay, Tom's headache is throbbing now, Yes, probably, Yeah.
I go for asprints, actually you know you do? Yeah, yeah,
I just go around trying to find willow trees and lick the bark. Okay,
all right, I wondered what you were doing. That's that's a natural
pankiller. I didn't know that. Hell, that's that's I think that's how
aspurin was invented. Not sure something like that. Yeah, willow is a
natural has a natural painkilling property in it. It does. Thank you,
Tom. Great to hear from you. This is space Nuts with Andrew Duntley
and Professor Fred. What's a space nuts? Now? Fred to a regular
contributor to our question answer session, and it's Duncan from Weymouth. I think
I'm pretty sure he'll tell me that's where he's from. Hello, Duncan.
Hear from Weymouth in the UK. Another quick question. I know that Andrew
likes hypothetical one, so here's one that's been bugging me for a while.
If you could get a huge mass of rock together, say, well,
I don't know, a hundred times Jupiter's mass of solid rock in one place
and put it in either they wore a bit around a star. Would it
form a really massive rocky planet? Or is there an upper limits to how
big or how massive a rocky planet can be? Just interested to know and
if it couldn't form a massive, massive rocky planet, what would actually happen
to that rock to prevent it becoming a rocky planet. Would it somehow not
be able to be bound together, or would it melt or boil and form
a gas or what would prevent that? Okay, keep up the good work
and thanks for your efforts. Bye bye, thank you. Duncan m I
kind of become a type of belt or an asteroid belt or something like that
if it couldn't form a planet would have to sort of break up like that?
But how big is the limit? That's they So, yeah, it's
a really interesting question. And I think the limit is imposed is imposed not
by the physics of how big something can be. It's more about how things
evolve when planetary systems are formed. So we think that rocky planets do evolved
by the sort of silicon material in the original dust and gas cloud that formed
the Solar System. We think that stuff all stuck together became solidified turned into
rock. These bits are rock bashed into one another, some stuck together,
some didn't. But in the end you got planets building into a sort of
rocks building into planetismals and then to protoplanets and eventually two planets. But this
is all taking place within an environment that is very very gasy. And if
you form rocky cause that start getting very big, you will also a mass
gas you want just you don't want just to create rock, you'll acret gas
as well. And that's why we think the gas giants are gas giants,
because they grew big enough that they not only collected more bits of rock,
they actually collected very significant envelopes of gas around them. And it sort of
helped as well by them what we call the frost line or the ice line
in the Solar system, that region which is between the orbits of Miles and
Jupiter, where where ice actually forms because the temperatures low enough. Yeah,
and so that the you know, the limits are more about the way you
form planets rather than what could exist. Um, whether a hundred jupiter mass
I mean a hundred jupiter mass solid, a hundred jupiter mass object is is
actually a star because I think the the mass linits for brown dwarfs, is
is it thirteen jupiter mass is up to about eighty I think in something in
that range will produce deuterium burning and become what's called a brown dwarf star.
But if you get above that, then you've got a dwarf star. Um
So, but that's assuming it is made of gas. I think that the
physics present prevent you from forming a rocky planet with anything like that kind of
mass, because it would have created gas rather than create just more rock.
Okay, that's that's pretty good though. I think we are discovering rocky planets
that are much much bigger than Earth. Yeah, that's sort of up to
neptune mass. But they're called super earths, so that yes, So what
that's saying is that we we perhaps haven't achieved that limit within the Solar System.
Yeah. Well, in the scheme of things, our rocky little world
is actually one of the smaller ones, isn't it in real terms? Yeah,
although it's hard to you know, the bottom line is that we're not
really yet able to detect all the smaller planets that around stars because it's harder
to detect them. You can do and there are programs that that you do
that. Gravitational lensings. Want transit method lets you do it as well.
But the and perhaps you know, the Kepler and tests spacecraft have both contributed
many objects which are small compared with you know what we used to be finding,
which were always the Jupiter of us. Things are bigger, so we
are finding rocky planets. But there's still I think, gaps in our knowledge
because when I've got the technology yet to define the smallest ones, so when
we get that perfected, we might find a whole bunch thinks that a smaller
than the Earth as well. Yeah, okay, thanks Duncan. Always good
to hear from you. Jim is next. He's from something I can't pronounce,
New Orleans. Yeah, New Orleans, it's Jim dear, Professor Watson,
and mister Dunkley. I've been traveling by car a lot in the past
year and was able to catch up on all your podcasts thus far, Blimy,
I truly enjoy the show and look forward to the next episode. Onto
my question. Because the bodies in the universe are accelerating at an ever increasing
rate, eventually there will come a time when space time will become impracticable or
space travel will become impracticable, if not impossible. What I mean is that,
eventually, as a result of increasing excel leration, the velocity at which
galaxies and their component parts move through the universe will attain a substantial percentage of
the speed of light. If we cannot build spacecraft that attain speeds greater than
that substantial percentage of the speed of light, then it seems that when a
spaceship leaves the Earth's gravity, well, the Earth will become unreachable by the
spaceship because the spaceship cannot catch up. Can this be right? There must
be something that I'm missing. Thanks for your thoughts. Have a great day,
Jim. Yeah, that's I can see where he's coming from. It
is a quandary, And yes, we have talked about the fact that as
things expand, we're eventually just going to be totally isolated in the universe.
We won't be able to see anything else, which is due to happen in
a couple of days. But what yeah, yeah, indeed, what's the
what's the answer to Jim's quandity? I think on the body actually, because
yes, if we look into the distant future, when the expansion has accelerated
so that you know, you're talking about a hugely greater expansion of space time
than we have at the moment, things will disappear beyond the horizon because the
light that's leaving them now will never catch up with the expansion of the universe,
so we won't see them. And that's the point that you were just
making, Andrew, that we will have a very lonely existence when you look
a few trillion years perhaps down the track, because there won't be anything other
than the local group of galaxies visible. Maybe the local group will disappear as
well. And I suppose what Jim's question about the spacecraft really means is that
if the spacecraft could get far enough from the Earth so that it was being
carried away from the Earth due to the expansion of the universe by a velocity
higher than the velocity of the spaceship could have achieved, then yes, you're
right, you will abs get back. You'd never never make it back.
So yeah, it's an interesting conjecture, and the universe very different from the
one we live in today than It's a horrifying thought, though, isn't it.
Let's go visit that rock. Oh it's gone, yeah, and we
can't get back. Not good, thank you, Jim. On a similar
kind of playing field, Paul in Melbourne says there has been talked recently about
the energy that causes the universe to expand coming from black holes. If this
is so, then wouldn't we see the space time around or near a black
hole expanding at a faster rate than that further away from black holes, for
example, between galaxies or that in the spaces between the filaments of the cosmic
web. Wouldn't the filaments of the cosmic web be expanding faster? And it's
pretat data. Yeah, I'm just trying to remember what the mechanism wants that
linked and quite get my head to it that linked black holes with the dark
energy, which is what, you know, what is the thing that we
think drives the expansion of the universe. Dark energy seems to be very much
a property of space itself, a uniform property that that's the same wherever you
look. So Paul's question is is an interesting one. So and I can't
remember the exact link between the mechanisms within black holes and the dark energy,
because yes, you know, it's an intuitive thought if if dark energy coming
from black holes, then the region around black holes should be expanding more than
the region elsewhere. But we already observe the fact that that doesn't happen.
We do see space time distorted around black holes. But that's due to their
gravitational attraction. That's the standard general relativity distortion of space time that we see,
you know, whenever we find gravitational lenses, for example. So,
as I said, the point about dark energy is, say it is a
phenomenon that is a property of space. I would have to I'd have to
look back at what I was reading up on the mechanism that feeds the energy
of black holes into the space around them to be able to give an answer
to pulse question. So I'm a bit embarrassed that I can't do that.
I mean, it was about well, it must have been at least two
months ago when we talked about this. Yeah, I guess, so I
don't remember the conversation. I just yeah, I just can't recall it.
Is it is that paper I don't think has been refuted, the one that
suggests that maybe black holes could provide the origin of dark energy. And I
wish I could there is a there's a there's a point about it which I'm
just not not able to recover at the moment from the memory bikes. Yeah,
I could have a quick look and see if I can find the article,
but gosh, I don't know. There's yeah, there's there's plenty of
articles about it, So which one do you pick? But yeah, it's
certainly got a lot of interest at the time. Will continue. So we're
talking, we're talking mid February when that first came. Yeah, so you
know it's fair enough that at our age we've forgotten. I felt we remember
the was there? Yes, yes, indeed, So Paul, I might
try and look at that again and we might get back to if we don't
forget. Thanks entire conversation. I'll put an asterisk next to his question.
Follow up. All right, thank you, Paul, Thanks for sending in
the question. This is Space Nuts Andrew Duncley here with Professor Fred Watson.
Great Space Nuts. Okay Fred, a few more questions before we wrap it
up. And this one comes from Western Australia and our good friend Rusty,
actually, to be more specific, Rusty's wife. Hello, Space Nuts.
It's Rusty and Donnybrook. My lovely wife Ally came up with a question about
asteroids and she's seen a few movies with asteroid fields in them and wonders if
they're realistic, how close do they get and how often do they collide,
and I think I'm sure she'd love your answer. Cheers, Thanks, Rusty,
we are Yeah, asteroids are not an uncommon topic of questions either,
mainly the ones that are going to hit us or near nar hit us.
But yeah, a different spin on it, so to speaking, and a
good one too, great question, because we you know, when you look
at depictions of the Solar System, the main asteroid belt, which sits between
the orbits of Males and Jupiter, is always portrayed as being full of asteroids,
asteroids everywhere in every direction. Whereas the bottom line here is, you
know Douglas Adam's famous quotation, space is big. You will believe how big
it is. Anyway, it's big. What was it? You might think
it's a long way. You might stret a long way down the street to
the chemist. That's right. Anyway, there is a lot of space between
them. So, as witnessed by the fact that I can't remember how many
is it must be this five. About eight or nine spacecraft have gone through
the asteroid belt, including Galileo Cassini, two Voyagers to two Pioneers New Horizons.
They've all gone through the asteroid belt and of course been completely unscathed.
On having said that, the second part of rust wife's question, I'm sorry
I didn't catch your name, But the second part is do they collide?
And the answer is yes. From time to time they do, which we
see usually as a plume of material coming from an asteroid that's being accidentally observed,
usually because since part of the field of view of something else, so
some nondescript asteroid will suddenly start looking like a comet. It will get a
tale of material, a bit like Demorphus did after it was clouted by the
Dart spacecraft. So you get this usually reasonably straight lined cloud of material which
is interpreted as having been a collision between two asteroids. We think we've even
observed one in the planetary system of another star. The star is Famulo.
It's a bright star in our southern skies, and over a number of years
that's been observed to have an object going around it. We covered this,
I think a year or so ago Andrew, which was thought to be a
planet. They gradually got fainter and eventually disappeared, And the thinking is that
what we actually were looking at was the debris cloud from two large asteroids that
it collided. That collided because that thing's vanished altogether now as the debris cloud
disperses, so they do collide relatively rarely because the space between them is so
it's big. Yeah, I mean, going back a few billion years,
it was probably a lot more collisions. There's a lot more stuff out there
to hit each other in close proximity. In fact, that we give that
period a name, it's called the Late Heavy bombardment about three point eight billion
years ago, when the place was full of debris charging around and bashing into
other things, including Earth. Yeah, including Earth. That's right. Indeed,
Thanks Rusty and spouse. Let's get let's go onto annex. Question from
Renny all right, this is ready from West Hills, California, with another
question. I'm trying to understand what space time is made out and why it
bends when it interacts with matter. I envisioned space climb as an invisible energy
force pushing against some object of matter, which is another form of energy,
where they to find a balance, which is gravity. Am I correct?
Yes? And the answer to your question is it's made up of space end
time. Yeah, that's the trouble. Nobody really knows what space time is,
but I can qualify that a little bit further because whatever it is,
yeah, you know, we glibly talk about the fabric of spacetime bending under
the action of mass. Renny is quite right. It's really hard to get
your head around that because back in the eighteen eighties we got rid of the
idea that there was an ether something that actually permeated space and allowed light to
pass through a medium that would transmit light that got thrown out, and the
consequence of that was actually the special theory of relativity, which says that you
know you're in the speed of light is the same everywhere because the experiments,
the Mikolson Morley experiment as it was called, to measure the ether relied on
the fact that you should see the speed of light changing depending on what direction
you're moving through the ether. And we're not moving through the ether, so
the speed of light doesn't change. And that then brings up special theory of
relativity. So we really don't know what it is. But I think you
have to look at the big picture here, because the big picture says,
well, there are two sort of pivotal theories on which we base our view
of reality. General relativity, which works incredibly well for things on a large
scale and quantum mechanics, which works incredibly well for things on a small scale.
But the two are incompatible. They don't sort of sit together, and
that sparks back in Einstein's day. Actually the quest for a theory of quantum
gravity that would allow us to unite these two theories, which we're still looking
for. But one of the themes that I think is addressed by quantum gravitists,
if I can put them that way, people theoretical physicists who work on
this. One of the themes is that we're missing something, and what we're
missing is a more fundamental theory of space and time that underpins what we see
as space and time. In other words, there might be something else that
from which space and time emerge and hence space time. Many quantum theorists in
the last twenty years have proposed that, and most of the theories I mean
string theories one of those. It's that sort of idea that there's something there
that underpins what we observe in relativity and in quantum mechanics, and a kind
of deeper version of reality which may include additional dimensions. There is some recent
work that's being done on this, which we might talk about in coming weeks.
Andrew, that once again highlights that there might be this hidden reality beneath
space and time, which how do we probe it? That's the problem and
the suggestions that are being put forward by how we might deal with that in
a real situation, how we might actually try and peer underneath the gossom avail.
It's not gossom avail, it's a curse relativity. And on the other
side, quantum mechanics, also known as the banking industry. The banking industry
has got that as well as different realities. In fact, yes, I
think there are many places in the world where you can put to different realities.
Yeah, indeed, thank you, Renny, and hope that helped somewhat
now adequately. Now, finally we'll go to David, who is from Huntsville,
Alabama. First of all, I'm a huge fan of the show and
appreciate what you guys do to put new wrinkles in my brain. I look
forward to each Thursday for my space nuts fixed. My question is if a
photon does not experience time after it's been emitted, and the universe is expanding
greater than the speed of light, assuming the photon has an unimpeded line straight
towards the edge of the universe. Is the photon essentially trapped in time at
that point? Thanks keep up the great work kind of relates to a question
we had earlier. It does yet, and it presupposes the universe as an
edge, which we don't think it has. We don't know what it's got
will beget us an edge. It's got a banking industry surrounding it, a
pique veil. So if but if the photon, you know, to the
photons always traveling through the universe at the speed of light. Now, the
fact that it's the source of the photon and its destination are separating, are
being separated by the expansion of the universe greater than the speed of light,
doesn't matter to the photon. It just keeps ongoing. The fact that its
target is moving away from it faster than it's ever going to get there is
not a concern to the photon. It will still not experience the passage of
time, which is exactly what David said. That's what we think is the
case. We'll just keep going forever. I suppose, in a sense it's
the scenario that he he mentioned that it will just keep on passing through space
and infinitem because it's destination is not good. He is always going to be
further away that it will reach until the big rip an escape, yeah maybe,
or if there's a big rip, there'll be tidal forces beyond imagination that
would probably disturb everything as it. Yes, that's the big rip. There's
got consequences that we can't really envisage it at the moment, but it's definitely
not nice and it reminds me of that famous song I'm a Photon and I'm
okay, I Glow all day and I Glow all night and I Glow all
day stealing from Monty Python. Yeah, not quite, but nearly works as
well as the original Lumberjack song. Thank you, David. It's so great
to hear from you, and thanks to everyone who's sending questions. It's nice
to fill an episode with audience questions. And we've got a whole fresh batch
like one minute before we started, so that was that was good, and
that's why some of them sort of caught us out of left field because we
did what we usually do and went in totally unprepared. Sometimes works, So
if you do have a question for us, of course, send it to
us, because that's what it's all about. We love to interact with you
and we love to hear your voices. So where you can record through our
website, space nuts podcast dot com or space nuts dot io. Click on
the AMA link and you can record a question there, or send us a
text question, or you can just hit the tab on the right hand side
at the home page send us your voice message. And as long as you've
got a smart device or a computer or something dumber than that that's got a
microphone, you can send us a question. But we're taking text and audio
questions all the time. The more the merrier. And yes, don't forget
the hypotheticals. I love those hypotheticals. Fred, we're wrapping it up for
you yet another. It's a milestone. It is actually three hundred and fifty.
Kind of let that slip through to keep it. I'll believe it.
Yeah, fifty three hundred and fifty. Oh my gosh, it seems like
only six months ago we did episode. Probably a year ago we did episode
three hundred. That's a bit, wouldn't it, Yes, that will be
I have to be near a year would yes? That's a calculation there the
words we should get a life really come to by. Maybe we should thank
you Fred as always good good to tell Andrew take care all right, We'll
catch you soon. Fred Watson, astronomer at large part of the team here
adds Space Nuts and back at Space Nuts HQ, we say thanks to Hugh
for reasons we cannot comprehend, but anyway, thank you anyway, and from
me Andrew Dunkley, thanks for joining us each and every weekend for this latest
episode. We'll catch you on the very next one on Space Nuts. Bye
bye. You'll be listening to the Space Nuts podcast, available at Apple Podcasts,
Google Podcasts, Spotify, iHeart Radio, or your favorite podcast player.
You can also stream on demand at bides dot com. This is been another
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