Andrew Dunkley: Hello again. Thank you for joining us on
another episode of Space Nuts. This is a Q
and A edition where we take audience
questions, we write them on a piece of paper
and then we throw it in the bin. Or we
could answer them. We'll do the latter. Uh,
we got questions about ultra hot
Jupiters. We've also got questions about,
uh, reusing spent rocket fuel. How would
you do that? That is the question. And
wow, how about this one? Uh, some conspiracy
with the Artemis 2 mission
being fake. We'll deal with all of that on
this episode of space nuts.
Generic: 15 seconds. Guidance is internal.
10, 9. Ignition
sequence start.
Jonti Horner: Uh, space nuts.
Generic: 5, 4, 3, 2, 1. 3, 4, 5,
5, 4, 3, 2', 1.
Jonti Horner: Space nuts.
Generic: Astronauts report. It feels good.
Andrew Dunkley: And joining us to try and sort all that out
is Jonty Horner, professor of Astrophysics at
the University of Southern Queensland.
Jonty, hello.
Jonti Horner: Good afternoon. How are you?
Andrew Dunkley: I'm, um, all right. Um, please forgive me if
there's some background noise. There's a
gardener working, uh, just out the front, and
he's, uh, doing a fabulous job. But he's
using that kind of equipment that you would,
um, you know, demolish a building with.
So, uh, it's, um, it's making
quite a noise. But, um, I've got my filter
turned on, so hopefully it'll just keep it
blocked out.
Jonti Horner: Oh, it's amazing just how well these things
work. I use this microphone in front of me
for my teaching. I've had a number of
occasions where the dog has decided that I'm
painting too much attention to my students
and not enough to her. And it's got quite
vocal about that lying just behind me here
next to her fire at the minute, keeping her
really happy. And they say, no, we can't hear
anything. It's amazing how well it can filter
out the background noise.
Andrew Dunkley: Yeah, the technology is amazing today. It's
like the telescope technology that exists now
where you can filter out light pollution.
I don't know how that works, but, uh, it's
quite incredible these days. Works really
well. I want to answer some questions.
Jonti Horner: Of course.
Andrew Dunkley: All right, let's start with David, who's on
the Sunshine coast in Queensland, Australia.
David: G', day, David from the sunny coast again. I,
uh, just had a question regarding the, uh,
ultra hot Jupiter article from the latest,
uh, podcast. Um,
in the conversation, Fred Watson, uh,
mentioned that, uh, the belief is
that stars and their surrounding planets all
form from the same, uh, disc of material.
Um, I just had a question regarding the
material. Um, you know, we tend to
think of stars as Helium or hydrogen or both,
um, and everything else as metals. And we
believe those metals formed within stars,
uh, due to the
fusion burning. Um, where then
does this material come from in the disc to
form a star and its planets? Is that from
material from. Do we believe it's material
from another star or, um, is there some
other process going on? Thanks very much for
the show. Awesome. See you guys.
Andrew Dunkley: See you, David. Thank you very much. Um, that
sounds like it's right up your alley.
Jonti Horner: It is. It's a good film to start off with.
Sah. Uh, you're right. The
material that forms a star and its planets
has been contributed to by many previous
stars. If you imagine after the Big Bang, the
universe was hydrogen and helium and a tiny
little bit of other stuff, but it really was
barely any, which meant that a generation of
stars formed that were pretty much just
hydrogen and helium and very little else.
Those stars in the early universe, there's
some speculation that they may have been,
including mega megastars, much
bigger than something called the Eddington
Limit, which is a maximum size a
stable star can form, um, because of how
dense the universe was at the time, how much
material there was. So speculation of stars
up to several thousand solar mass. Those
stars lived fast, died young, put
material back out into the cosmos. So they,
when they died, they locked some of the stuff
up in the remnants to the left, whether
that's a black hole, a neutron star, a white
dwarf, whatever. But the material that was
flung outwards to form planetary nebulae,
supernova remnants, disperses into the
wider galaxy. So what's happening over
the aeons of time since the Milky Way formed
is that stars are born, live and
die. And when they die, they pollute the
cosmos. Stars of different masses throughout
different things. But what that means is that
you gradually get more and more heavy
elements introduced into the galaxy.
And, um, that goes to basically contributing
to the composition of the gas and dust that
floats around in our galaxy. If you go out,
particularly this time of year in the
Southern Hemisphere. But if you go out on any
night of the year where you can see the Milky
Way, you'll see that in the band of the Milky
Way, there are dark patches as well as
glowing bits. The dark patches are not
places where there is a lack of stars, but
rather they're places where you've got huge
clouds of gas and dust that are opaque, that
are blocking the light from stars that are
more distant from reaching us. So they look
dark in the same way that a cloud blocking
the sun will look dark in the daytime. It's
blocking light from beyond. These clouds
can be vast and they're made of gas and dust
and ice, mainly hydrogen and
helium, but lots of other stuff. And that
other stuff will vary from one cloud to the
next to some degree, based on what it has
been polluted with. You'll have to some
degree a stirring, a pollution of the galaxy
that gives you a background increase in the
amount of metals. But you'll also get local
variation. We see all of this
incidentally in the Earth and the solar
system. There are suggestions that the solar
system, when it was young, when it was
forming, was polluted by a nearby supernova
that injected a lot of very short lived
radioactive aluminium isotopes that
accelerated the degree of melting you got in
the rocky objects. There's a signature there
of a radioisotope that is so short
lived, there shouldn't really have been any
of it around, unless a supernova exploded
nearby to pollute our disc, giving us a
slightly unusual composition. There is also
an argument that the Earth is richer
in gold than it should be, because
sometime between 10 and 100 million years
before the formation of the Earth, 10,000
light years from where we formed, two neutron
stars collided, polluting the universe with
gold. And some of that gold made its way into
the disc that formed the solar system, got
incorporated into the Earth. And that's why
we are a particularly good place for
Goldfinger to, uh, have his little layer.
We've got more gold than normal.
Andrew Dunkley: Yeah.
Jonti Horner: What this all means is that those giant
clouds of gas and dust in space can be truly
vast. When they get nudged and start to
collapse, they'll fragment in their interiors
to form a cluster of stars, a number of
stars, which form from the little denser
bits. It's like driving through a fog bank.
Fog banks are never one uniform density.
There's denser patches and less dense
patches. A denser patch in one of these
clouds will collapse under its own gravity.
And so you'll get lots of stars forming. As
that material collapses in, it collapses down
to form a disc around that young protostar
that's forming. And the star and the
disc are made of the same material. They're
forming from the same material. All that
material that was in the cloud from which
they're formed, which has been polluted over
many generations of stars, cooking the
books to give the composition that is uniform
across that star system. What happens then is
that the star forms from everything, so it
ends up very rich in hydrogen and helium.
Because even after all that pollution and all
that evolution, hydrogen and helium still
make up something like between 98 and 99% of
all atoms in the universe. So the star is
going to be primarily hydrogen and helium
with a thin veneer of everything else. In
other words, the abundance of material in the
star is going to be very nearly
identical to the disc. Star will end
up being very, very, very slightly enriched
in the heavier elements, because from
the disc, particularly when the disc is
cleared, there will be some infall of rocky
and icy objects like the Kreutz sun, grazing
comets, we see that fall into the star and
pollute it further. But that' very, very
small effect compared to the overall mass of
the star. The planets form in the
disc in the main
form through a process we call core
accretion. There are some suggestions that
some of the most massive stars can form
through a process of instability. And those
planets and binary stars would form with a
more stellar composition, I.e. lots of
hydrogen, helium. But most planets
will form by initially growing a core of
solid material, because when you have a low,
uh, mass, you can't capture gas,
and so therefore your composition will be
dominated by the solid material, not the
gases. So that's why the Earth doesn't have
free hydrogen and helium. We simply don't
have enough mass to capture those gases and
hold onto them. So even though 99% of all
atoms in the protoplanetary disc were
hydrogen and helium, we didn't get any of
them, other than the old tiny little atom
that was captured in a cage of other
compounds called clathrate,
that was captured in a mineral effectively.
So we barely got any of those materials
because we couldn't hold onto them. We formed
out of the solid stuff. The further you are
from the star, the colder it is, so the more
different things can be solid rather than
gas, which is where we get the idea of the
ice line. If you're far enough from the star,
water can be solid, can be ice, and then
suddenly you've got a lot more solid material
because water's about the most common
compound there is, almost it's the most
common atom, hydrogen, and the third most
common atom, oxygen. And you put them
together and you've got water. So beyond the
ice line, you've got a lot more solid, and
you can form planets much quicker, which is
why we think Jupiter and Saturn got so big so
quickly. They had a lot to feed on. And
eventually they got massive enough that their
gravity was strong enough to hold onto the
hydrogen and helium around them and devour
it. So they are
in composition much more similar to the sun
than the, uh, Earth. Is because they have all
that hydrogen and helium, but they are still
richer in solid material than the sun
because at their core, there was all the
solid material needed to build up before they
could gather the hydrogen and helium. So they
started with more solids. Effectively.
The Earth doesn't really have the hydrogen
and helium. So all of the objects in our
solar system will have the same composition
as the sun in terms of the balance between
carbon and nitrogen and iron and all these
elements, except for where they weren't able
to capture those elements because they
weren't massive enough. So the Earth doesn't
have the same composition as the sun in terms
of hydrogen and helium, but it does in terms
of iron, nickel, all those things,
the balance between iron and nickel and
carbon and all the rest of it are all in the
same ratios as the sun, um, to an
incredibly high precision. And that's because
we all formed from the same material that
quite rightly was mentioned in the question
was delivered by past generation of stars
that had lived and died. And that's where the
whole concept that we are stardust comes
from. It's the idea that all the atoms that
we need to make us, us, other than the
hydrogen atoms, were cooked in the furnaces
of stars long de. All the carbon, the
nitrogen, the oxygen, the phosphorus, all
those wonderful things, calcium, that
contributes to our bones are all stardust
from stars that died long before the solar
system formed.
Andrew Dunkley: There you are, David. Um, a very
good, uh, answer. That pretty m. Well, nails
it. I like the bit about there being more
gold on Earth than there probably would be in
other places.
So that's. That was a lucky break for us.
Jonti Horner: Absolutely. So useful for a
lot of the technology we use. Not just for
those who are sparkly, bangly things, but,
you know, there's a lot of those rarer type
things that are so vital to our technological
growth that are all linked to our ancient
heritage.
Andrew Dunkley: Yeah, yeah. Um, well,
there's gold, there's lithium.
There's just so many of them. But we've got a
lithium mine just down the road from us,
actually.
Jonti Horner: And that lithium, probably all primordial,
the lithium in the universe, is almost
certainly, almost all leftovers from the Big
Bang.
Andrew Dunkley: Wow, that's interesting. There you go,
David, thanks for the question. Lovely to
hear from you. Hope all is well on the
Sunshine Coast. This is Space Nuts with
Andrew Dunkley and Jonty Horner, A
Q and A Edition.
Generic: Roger, your lab is right here.
David: Also Space Nuts.
Andrew Dunkley: And we're with Professor Jonty Horner today
with Fred Watson away. Uh, let's Go to our,
uh, next question. Jonty, this one comes from
Mark.
Mark: Hi, it's Mark from Sunny Siddlesham in the
uk. I've eventually plugged up the courage to
send in an audio question, so here goes. You
quite often mention water ice and the
possibility of turning this into rocket fuel.
So my what do you think? Sort of question is,
when you use hydrogen and oxygen as a rocket
fuel, it must turn back into water ice in
space. So do you think it would be possible
to collect it and reuse it through the rocket
engine, again massively reducing the amount
of fuel you would need to carry for an
extended journey, say, to Mars? I've sort of
drawn up an idea, but what do you think? Once
again, keep up the great work, Mark from the
uk.
Andrew Dunkley: Thank you, Mark. It's an interesting idea.
My, uh, first thought when I
first heard the question was, um,
how would you collect it? That
might be the first challenge.
Jonti Horner: That would be a bit of a challenge. I mean,
the thing is, your exhaust is being pushed
out of the bucket, the rocket, at very high
speed in a very dispersed form. Now the
rocket's going forward because you're
throwing the things out the back. You've got
the momentum, um, being transferred and it's
equivalent, I guess, to you. The way I'd
visualise this is imagining, again, sitting
on an ice rink on a wheelie chair. So you've
got no friction whatsoever, really slippy and
you're holding, Normally, I'd just say one
medicine ball, but instead imagine that
you're holding a big bag of short puts. You
throw a short put away from you and you'll
recall in the other direction. You throw
another short put and you'll speed up and
you'll move in the opposite direction to the
direction your short puts are going. So
that's how you'll work. And that's
essentially what you're doing with the
rocket. You're pushing material out of the
back and you're moving the opposite way,
because overall, the momentum is conserved
between the stuff going one way and you going
the other. The problem with the
rocket itself capturing its own exhaust,
pumping it back in and reusing it, is
then you're taking that momentum and bringing
it back to you, which means you're getting
pulled back towards it and you'll end up
having gone nowhere to some degree.
So imagine now that situation with the short
puts on the I shrink, but
instead you've got a really efficient bungee
cord, so that when you throw them away, they
bounce back and you catch them again. What'll
Happen is as they're moving away from you,
you'll wheel away from them. And then as they
get pulled back towards you, you get pulled
back towards them and you end up where you
started from. Here will know a little bit of
change due to friction and loss of energy and
stuff like that. So the problem I'd have
with this suggestion is not actually the idea
of capturing and reusing the fuel.
Um, I think that will be hard because the
fuel will get so dispersed, so water will be
scattered out there. It's just easier to go
get a big lump of ice from somewhere than try
and pick up individual water molecules or
small grains of ice disperse over a large
area. But the idea of being able to capture
it from the same rocket and reuse it would
get you into this problem of having to pull
back material that you've pushed away, which
means you'd be pulling yourself back to where
you started from. So you can't get away, I
think, from that momentum issue there.
So I think it's two different things. I think
if you had the ability to, instead of using
hydrogen and oxygen as a fuel and burning
them to be water, you can instead have a
rocket fired powered by firing
pellets of water out of the back. You could
fire them at a target that captures them, um,
collect them and reuse those pellets for
something else. But that target will get
pushed around by the arriving water pellets.
So you'd want to be clever with that and
you'd need to continually change its orbit
and stuff. So in theory, potentially, you
could gather the fuel for use on another
rocket without it being the rocket you're
flying that gathers that fuel. But in
reality, you're dispersing over such a large
area that unfortunately, it wouldn't be that
practical anyway. Especially when we've got
just huge lumps of ice floating around
anyway. I mean, you and I have both been
photographing a beautiful lump of ice flying
through the solar system. There we go in the
background. That's enough fuel for
missions forevermore. If we were to go and
mine there, and that's a lot more efficient
to mine one big comet or
asteroid for water ice or mine the moon for
water ice, then try and catch it when it's
dispersed, I think. So it's a really good
idea. It's really good thinking. But it's
something that wouldn't work. I think that's
the way I'd view it.
Andrew Dunkley: It'd be very complicated. And as you said,
um, trying to capture it in the ship, you're
actually propelling would be
counterproductive. Using another
spaceship to capture the ice after it's been
expelled, uh, would be difficult because it
would spread out too far. But then you're
using the same technology
to chase the ice that's been spent already
and spending more to get the ice back. So it,
yeah, It's a catch 22. It's just going to
keep going around and around. So um,
it makes it a little bit difficult. Uh, Mark,
but, uh, thanks for your question, that
was a fun one actually. But, uh, yeah,
um, yeah, I like the way people
think. But I, uh, suppose just to expand on
it a bit, um, there's going to come a
time where using those kinds of fuels
probably won't be necessary. They're
developing all sorts of different kinds of
engine technology, uh, everything
from solar sails to scramjets, and
they don't use that kind of fuel.
Jonti Horner: There's all sorts of things you could do. I
mean again, going back to the Bobiverse,
which I mentioned before, the Van Neumann
probes going through, they used kind of um,
ram scoots essentially initially in the book
set. They then move on to other kind of
speculative sci fi things. But initially the
idea of having a fusion drive where you scoop
up hydrogen atoms and turn them into helium
and push them out the back where in front of
you you deploy a big thing that gathers the
hydrogen you're moving through. This is also
what they did in Tau Zero by Poole Anderson
is you know, you're moving really quickly,
you gather hydrogen from in front of you and
compress it like a ramjet effectively.
There's all these kind of things, but they
will all, unless we get to truly sci fi
type things like warp driver albatier drives
or whatever, which require physics to be
somewhat different than how we can only
understand it. You still have
either a source of propellant which you
then get rid of out the back one way or the
other, or with solar sails you're using
the stellar wind and that pushes you away.
Um, people who are sailors can probably tell
you a lot more about the complexity of how
you can tack into the wind and move across
the wind. But the wind, the solar wind is
incredibly tenuous compared to the wind in
the Earth's atmosphere. So you need a very,
very big sail. And I think that will be
somewhat limiting. If you were wanting to do,
I guess, Star wars style dogfight manoeuvres,
you wouldn't do that with a solar sail. So
people will pick the right technology for the
kind of mission that they want. And that was
where the dawn mission which went to Ceres
and um, Juno in the asteroid belt was really
interesting because it used an ion drive
where it was using I think ionised xenon. And
um, that kind of drive achieves a much,
much lower thrust but can operate for much
much longer time. So it's very energy
efficient um, but it wouldn't be any good for
getting off the surface of the Earth. But
it's very, very good for cruising around the
solar system when you're not in a rush. And
so what will happen is I think different
people will have different types of drives
for different types of scenario
and choose the one that works best.
Andrew Dunkley: Yeah but to get off the planet at the moment
you need rockets. There's no real
other technology that will get you out there.
I know they've been trying um, sort
of catapult technology uh, which
um, could deploy satellites in the
future. I um, think
you'd need to be in the right place on the
planet to take advantage of the um, rotation
of the Earth so that you don't have to like
you couldn't do it too far away from the
equator, that kind of thing. But um,
at the moment uh, yeah the um, standard
old rocket engine is uh, the best option at
the moment.
Jonti Horner: Um, part of where the refuelling station idea
around uh, the moon comes from which is if
you have to take your fuel with you, you're
carrying a lot of extra weight so you've got
to burn extra fuel to carry that fuel which
means you're carrying extra weight so you've
got to take even more fuel to burn um, to
carry the weight of the fuel you're carrying
to carry the extra fuel. And so uh, it
becomes very inefficient very quickly. So if
instead you can small launches from Earth and
then refuel once you're beyond the Earth,
that's a lot more effective. And the other
thing that people have suggested long term
um, as a solution to get things off the Earth
more cheaply are things like space elevators
which are ah, probably still far science
fiction. I don't, don't think we have the
material science to do that nor the political
will. I mean putting that in perspective,
just saw the announcement this week that the
vast inland rail project that was happening
in Australia is no longer happening because
it got too expensive and it's taken too long.
And if we can't build a railway between
Melbourne and Brisbane, it's going to be
really hard to build an elevator between low
Earth orbit, well between the Earth's surface
geostationary orbit and the same distance
beyond for the counterweight. Yeah,
So I don't see it happening anytime soon.
Andrew Dunkley: We can't even get a tunnel under the Blue
Mountains between the west and Sydney.
Uh, and that's despite the fact
that that road is currently closed due to
a structural failure in Victoria Pass.
The old convict bridge, that's, uh, 200
years old or something, or 150 years old. And
it's finally given up the ghost. And so
they've closed the road.
It's. You know, people have been screaming
for a tunnel for decades. And,
um, no politicians willing to spend the
money because there aren't enough people.
Bottom line is there aren't enough people
living west of the mountains to make it worth
your vote.
Jonti Horner: Really. What it comes down.
Andrew Dunkley: That's what it comes down to.
Jonti Horner: Reminds me of the old episode of the Simpsons
when I was a kid with the kind of argument
about books for the kids or something.
There's the two people at the front room
basically shouting, but our children, but
taxes. But our children, but taxes. And it's
this whole thing of everybody wants it, but
nobody wants to pay for it.
Andrew Dunkley: Exactly, yes. Uh, a tunnel under the Blue
Mounds would be wonderful, though. Although,
um, some. Some of the arguments against it
are, uh. Well, it'll only save you 15
minutes. I think it'd probably save you more.
Gets pretty log jammed up over that mountain.
Jonti Horner: We have those arguments about the Toowoomba
bypass, and that's been a godsend.
Andrew Dunkley: I mean, yeah, I used it last, uh, year. Yeah,
it's fantastic.
Jonti Horner: It fell apart and bits fell onto it because
they contracted fairly cheaply.
Um, but that has saved about half an hour
from my trip down to Brisbane when I go to
the airport and stuff because I don't have to
go through Toowoomba and all the freight
companies use it even though the tolls are
quite high. Because the tolls being high is a
lot better than the wear and tear on their
vehicles coming up the old road into
Toowoomba and having to stop at all the
traffic lights and stuff. So it works out
deeper for them. It's better for the
Toowoomba council because they're having to
repair less potholes and they have less
accidents. And it's one of those things where
it was a little controversial when it was
being built, but since it's there, it's been
a godsend. And I'd like to think that some of
these big infrastructure projects would be
the same. And I mean, a space elevator would
be wonderful, but, you know, gonna be hard to
persuade people to commit to building it,
even when we get the technology.
Andrew Dunkley: I think, uh, wait till there are
orbiting hotels that'll change everything.
You wait and see. Might be
waiting a while. Um, thanks, Mark. Lovely to
hear from you.
This is Space Nuts with Andrew Dunkley and
Professor Jonty Horner.
Jonti Horner: Space Nuts.
Andrew Dunkley: One more question, uh, Jonty. And this one
comes from Paul.
Joe: G', day, Fred Watson and Andrew. Paul here
from Sunnybridge, Vegas. I have
a question and a dirty secret that
I need to confess.
So I was on this Flat Earth group on
Facebook. Yes, I know, I know. Uh, anyway,
this guy provided some AI information
which was absolutely correct to
contend that there is no way that the Artemis
mission could have ever caught up to the
Earth because the Earth travels a hell of a
lot faster than that little spaceship.
I pointed out that they didn't need to
catch up to the Earth at all. They just
needed to point themselves to where it was
going to be and then splash down,
land safely, and be
applauded by everybody except for the Flat
Earthers like him, uh, who are absolutely
incensed at the moment about
how it's all fake, as per, uh, usual.
Anyway, I told him
that if he really wanted a better answer,
exact answer, he really needed to talk to an
astrophysicist. So my second question
is. Well, my first question is, was I on the
right track? And my second question is,
are there any astrophysicists or any websites
out there that can give us an animation
of the Earth going around
the sun that also has, uh, the
animated version of the Artemis going around
the moon so that we can see the whole thing
in context in terms of the solar system, or
at least our area of the solar system system.
Uh, it's not going to convince him, I'm sure,
but I think it'd be pretty cool to see
something like that. Anyway, thanks very
much, gentlemen, for the show, as always. Um,
look forward to it every week and catch you
later.
Jonti Horner: Have a good one.
Andrew Dunkley: You too, Paul. Thank you. If only we had
an astrophysicist somewhere nearby.
Jonty, any I know
was directing the question to Fred Watson,
but he asked for an
astrophysicist.
Jonti Horner: Yeah. We are legion, for we are many. There's
plenty of us around. It, uh, was always a
thing when I was at uni of what title you use
for what you're studying would depend on how
bothered you were about the conversation.
Because if, you know, if I told someone I was
studying physics, said very quickly, exit
stage left, if I told them I was doing
astronomy, they'd stay and chat. And if I
told them I was doing astrophysics, they'd
just look a little bit scared. Um, but I was
doing all three.
This is an interesting one. I mean,
people like the flat Earthers are difficult.
David: Ah.
Jonti Horner: Because there is no amount of truth, no
amount of evidence that you can put before
people who are convinced that they've been
lied to, um, other than talking to
them gently about it. And it's like
discussions of climate change I've had in the
past with people who argue climate change
isn't real. Arguing and fighting with people
over this doesn't win hearts and minds. It
just gets them more entrenched. But talking
to them about it and talking about why we
think something is the case, this is our
evidence, this is what it is. That can
be a little bit more fruitful, I guess, but
it is really challenging. I mean, especially
given that we had a beautiful eclipse of the
moon just a few months ago, where you can see
that the shadow of the Earth is round.
Andrew Dunkley: And that's the big argument. If the Earth was
flat, the shadow at some stage would be
just a line across the Moon.
Jonti Horner: We'd see the elephants in the turtle. Um,
the other thing is, if the Earth was flat,
the cats would have pushed everything off the
edge by now. Yes, yes,
that's the other one. But, uh, in terms of
Artemis, at the end of the day,
we know it happened because we saw it. You
know, I was over in Europe at the
time, and, um, my colleagues at UNISQ were
happily sharing their own little footage of
the spacecraft that they got from our
telescopes. They have no reason to lie.
They have no vested interest in this. It's
not like they're secretly on the payroll of
NASA, ignoring the fact that if it was faked,
Russia and China will be racing to tell
everybody because that will be the best PR
victory ever. You know, I mean, it's the same
with the Moon landings in, uh, 1969.
Did anybody really, really think that the
Russians would have stayed quiet if there was
a sniff of it being faked?
Andrew Dunkley: In fact, my great grandmother
always thought the Apollo landings were
faked. Uh, she absolutely refused
to believe it. But she grew up in an era
before flight, so
I can understand why she would
think that, but she just thought it was all
just some sort of publicity stunt. But I
don't remember what they might have been
trying to get publicity for,
Jonti Horner: because they beat the Russians. I mean,
that's what it was to them. I'll beat the
Soviets as it was then, have been pulled up
on that a couple of times.
Andrew Dunkley: It was definitely a big PR, um,
Jonti Horner: exercise in that regard. Uh, a former
PhD student who worked with me, Jake Clark,
Dr. Jack Clark, now M, gave a wonderful talk
a couple of times about the
moon landings in 1969 and why they couldn't
have been faked because we couldn't afford
it. Talking about faking it with the
technology we had at the time would have
actually been more expensive than going
there. Um, which is fairly compelling
for me. I mean, there's always a joke that,
you know, yeah, the moon landings were always
going to be faked, but they hired Stanley
Kubrick to direct and he was such a
perfectionist that they demanded that they do
it on site. Um,
um, with Artemis 2, there
is abundant evidence that it really happened.
You could, with a small telescope or
binoculars, go outside and see the
spacecraft. And I mean, you can't fake that.
It's not like we're beaming thoughts into
your head. And if you think we are, you can
wear some tinfoil. That's all good.
Um, in terms of the
argument that the Earth is going too quick
for this thing to catch up, that is
in the kindest interpretation of it, that
is allowing common sense
based on your understanding of how day to day
life works, interfere with
looking at how things would move through
space. I can see why you would get to that.
If you think about a small child running
along with a model of Artemis in the hand and
a Ferrari driving down the motorway, or
insert the make of car driving down the
motorway at 100 kilometres an hour, the child
is not going to catch the thing because
they're not quick enough. And there are, uh,
limits on how fast a child can run and how
fast the car can move to do with air
resistance. It's
however, almost similar to saying, you know,
I can't throw a ball up in the air and catch
it because I'm Moving at over 1000 kilometres
an hour around the Earth. So I'm moving too
fast to catch up with that ball. Doesn't work
like that because me and the ball are both
moving at 1000 kilometres per hour. And so
it's a relative speed between us that
matters. So the Earth is going around the sun
at about 30 kilometres a second. That's
demonstrably true. Artemis moving
in orbit around the Earth is moving around
the sun at 30 kilometres a second with the
Earth. It's falling with the Earth. Uh, so
it's a relative speed that matters.
Andrew Dunkley: Yeah.
Jonti Horner: Now, if I went above the Earth, onto the
space station, but instead of orbiting the,
uh, Earth and falling with things, I was able
to use rockets to stand still. Or I had
an imaginary hovering platform of doom that
wasn't moving. I'm, um, out of the
atmosphere. If I threw a ball up in the air,
it would move away from the Earth and the
Earth's gravity would slow it down and pull
it back, and it'd fall back down to me just
the same as how it does on the ground.
Now, if I was in orbit around the Earth and
I was stood on the International Space
Station and I tossed the ball upward, it
would actually start moving on a different
orbit around the Earth. So while it would
move up, away from me and it would move down,
it'd be going around the Earth on an orbit
that takes slightly longer to go around the
Earth than I do. So it also fall behind,
behind. And that would look like wind
resistance. But it's actually just a quirk of
orbital mechanics in that I've put it onto a
different orbit, um, because we are both
falling at the time I let go of it. So if we
imagine our flat Earther jumped off a cliff,
and I'm not encouraging them to please do not
do this, but imagine one jumps off a cliff
while holding one of the shot puts from the
previous answer without it being on a bungee
cord. And they let go of the shot put, but
the shot put will fall with them at the same
speed. It won't move away from them and come
back. It will accelerate downwards in exactly
the same way that they do. And, uh, they'll
only diverge once air resistance takes
effect, depending on which of them feels more
air resistance.
Andrew Dunkley: It's the Galileo experiment, isn't it?
Jonti Horner: So if you're on the space station, you throw
a tennis ball up in the air. Ah, you're both
actually falling, but you've changed the
speed the tennis ball's falling, so it'll
move away from you and not appear to come
back because you're both still falling.
The reason all this is relevant to Artemis is
Artemis boosted off towards the Moon at, uh,
a speed that was not greater than the escape
velocity from the Earth. It was a speed that
was high enough to get to the Moon. And, uh,
the moon steered it around and flung it back
towards the Earth. But then it fell towards
the Earth under Earth's gravity, moving
with insufficient sideward speed that as
it fell towards the Earth, it would miss us.
It instead was going to hit us. And they
controlled it with rockets and stuff so that
it entered in a controlled rather than
uncontrolled fashion. What matters is
not the speed the Earth's moving around the
sun, or the speed the sun's moving around our
galaxy, or the speed that the galaxy is
moving through space. All that matters is the
difference in speed between the Earth and the
object, because they're moving together. This
thing's speed was at no time greater than the
escape velocity of the Earth, so it could
never fall away from the Earth and never come
back. It was always going to go up and then
come down again. Unless they use rockets to
boost it into an orbit around the moon to
shed some of that energy, which they didn't.
They instead slingshot it around the moon to
come back. All of that is perfectly
rational and straightforward given our
understanding of physics. But it doesn't
necessarily fit your common sense, because
you think about throwing a ball out of the
window of your car while your car's doing 100
kilometres an hour and the ball will fall
behind you and never catch you up. And so
a lot of the arguments that
flat Earth, uh, believers or other people in
that kind of situation are making good faith
are, uh, built on a faulty groundwork
where the common sense of how they understand
the world to work is not applicable to the
situation they're applying it in. Um,
and that's true of things like, you know, the
oceans are flat. If you put a spirit level on
them, they're flat. Well, it's actually that
they're curved, but they're curved at such
small level that locally they look flat.
It's a subtle difference, but it's one that's
easy to miss because it's hard to get your
head around those distances.
In terms of the animations. I just did a
quick Google search for Artemis animation of
orbit, and there's some beautiful. The first
hit is a NASA flight with an annotated and
animated path. There's a few YouTube videos,
there is a Reddit link with an interactive 3D
animation. There's a lot of
little YouTube short videos that pop up
which are not to scale, because if you make
things to scale, the sun and the Earth and
the Moon are points that are one pixel
across. And, um, the spaceship is a point
that is a pixel across as well, because
nothing can be smaller than a pixel. Um,
there is a fabulous thing, incidentally, and,
um, I'm gonna see if I can find it, see if
it's still there.
There's this great thing called if the Moon
were Only One Pixel. Um,
it is. I'm gonna see if the website still
works, because this is one of the great
things on the Internet. Here we go. I'm gonna
Drop it into the chat window. This, um,
was an effort somebody made many, many, long,
long years ago. I'll put this into the public
chat, which never gets used. There we go. To
visualise the scale of the solar system,
if you made the moon one pixel across,
so the Earth will then be two or three pixels
across, you can, when you get bored of
scrolling, you can click Play. But if you
open that up and then you scroll to the right
to explore, you move along
and then you've got the scale. One pixel is
3,500 kilometres, so the sun is a fairly big
blob. And you scroll to the right from the
sun and you've got a distance at the bottom.
Scroll to the right a long way. We've gone 10
million kilometres. This is this fabulous
visualisation to let you see how big
things are.
Andrew Dunkley: Oh, isn't that clever?
Jonti Horner: How fast light travels. You can click, um.
That's slow. It's fabulous. Now what
you can do is you can skip through.
I need to find where there was a way to skip
to the Earth. Yes, at the top. Skip to the
Earth, goes whiz, whiz, whiz, whiz, whiz.
Really quick, goes past Venus, comes to the
Earth and the Moon. If the moon is one pixel,
the earth is only two or three and you get
the scale of them 8.3 light minutes out from
the sun. And think how far you've got to
scroll to get there. Think with that moon
being a single pixel, how far it is from the
Earth. This is why none of those animations
have things to scale, because you wouldn't
see the spacecraft, you wouldn't see the
Earth and the moon, they wouldn't look
pretty. So the caution there is that, uh, the
animations that you see, even the beautiful
NASA ones that show the flight path, are,
ah, not to scale. And, um, that can be
misleading. That can also
add to some of the arguments that this is
fake, because people say, well, the Earth and
the Moon are much smaller than that and
they're much further apart. Uh, that looks
wrong. Um, so it's worth being explicit
that these are, these visualisations are, um,
definitively not to scale. Um, the one,
incidentally, that was linked on the Reddit
page looks like the dots for Earth and Moon
actually are more to scale. So I'll just drop
that one in as well. Not sure how this works,
I've not really played with it. But you can
drag the orbits around, you can move them
back and forward in time, you can see the in
and out of plane stuff and you can move the
visualisation around even with the background
stars, which is quite nice. Um, so that's
worth a play as well. And that looks a bit
more to scale. And there's lots of things you
can play with, but fundamentally we
could see it. The hardest part for me, about
the small number of people who have argued
that the Artemis mission didn't happen,
is that it's something that anybody on the
planet could see, so long as they owned a
binoculars or a telescope. You could have
pointed somewhere and you could see the
capsule moving there if you really wanted. At
any time when the moon was above the horizon,
you could track it round.
Andrew Dunkley: And if you've got good enough gear, you can
actually look at the moon and see
the landing positions of some
of the Apollos. If you've got the gear.
Jonti Horner: If you've got the gear, I mean, that's kind
of spice athlete level. But what you can do
if you've got slightly less of the gear is
bounce laser pulses
off the retroreflectors that the astronauts
left at those sites and measure the distance
to the moon and measure its recession to an
incredible precision. And we can only do that
because people went to the moon.
Andrew Dunkley: Yeah, absolutely.
I remember the day that Neil
Armstrong stepped on the moon. I was, um,
sent home from school.
It's one of the strongest memories of my
childhood. I was seven years old and, uh,
I'll never forget it. It was, um, quite
an extraordinary thing in human history.
Inspirational.
Jonti Horner: I mean, I, I'm not old enough to have ever
seen anybody walk on the moon. I'm hoping
that'll change. But the generation of
astronomers who are 15,
20 years older than me, who were old enough
to see the moon landings and take them in,
so many people were inspired to become
scientists and engineers by that. We got a
whole generation of people across
the sciences, across the engineering subjects
that changed the world, who were all inspired
by seeing people walk on the moon.
And, um, it's kind of exciting to me, even
ignoring the signs, even ignoring the
technology, that we're going to get that
experience again in the coming years. If we
go back there, there'll be a whole new
generation who will change the world. All
inspired by those people touching down and
seeing it happen.
Andrew Dunkley: Yes, yes. I was very lucky to meet one
of them. Uh, Buzz Aldrin, um, some years ago,
came here because they built a Reutt
Flyer at a place called Narrowmine, just up
the road from here, 40 kilomet, and they took
it out for a fly and he came for the
occasion and, uh, gave A wonderful
speech and a, uh, handful of us in the media
got to interview him afterwards in a, in a
hangar at the same time as a helicopter
decided to take off.
Jonti Horner: That sounds about right.
Andrew Dunkley: He famously, you know what? You just, you
just go with it.
Jonti Horner: Oh, he very famously gave very short shrift
to people who told him that he'd not been to
the moon.
Andrew Dunkley: Oh, I know. Uh, Ah, yeah, I did
actually raise that question, but gee, it was
such an interesting answer.
Yeah, fabulous.
Um, Paul, great question, really
enjoyed that one and I,
I can understand your frustration, but, um,
maybe just avoid those Facebook pages,
um, because you can't, you just can't save
them, my friend. Uh, but good to hear from
you. Uh, if you've got questions for us,
please send them in. Uh, you can do that via
our website, space nutspodcast.com or
spacenut. You can also
visit us on social media. We've got the
official Space Nuts Facebook page and the
official. What's, uh, the
Instagram page. Uh, we've also got the
user group on Facebook, um, the
podcast group, uh, uh, which is
all. It's a lot of fun. It's where people who
listen get together, swap photos of stuff
they've taken in space and ask, uh,
questions. And, uh, it is a really good
group. So the Space Nuts podcast group on
Facebook book very much worth, uh, joining
that one as well and hope you'll join us
again real soon. And thank you to Johnny
Horner for filling in for Fred Watson for the
last month or so. It's been fantastic and
hopefully we can get that photography, uh,
special off the ground and get you back and
have a chat about astrophotography. Jonty,
that would be a real good one.
Jonti Horner: Fingers crossed. That would be awesome.
Andrew Dunkley: Yeah. All right, catch you soon. Thank you so
much.
Jonti Horner: M m. Take care. Thank you very much.
Andrew Dunkley: Professor Johnty Horner, professor of
Astrophysics at the University of Southern
Queensland, filling, uh, in for Fred Watson.
Fred Watson should be back, uh, next week
or later this week. I can't get my head
around when it'll be. It's a time slip thing.
Uh, but, uh, yeah, thanks to Jonty for
filling in and thanks to Huw in the studio,
who couldn't be with us today because he's
fake. Boom, boom. And from me, Andrew
Dunkley. Thanks for your company. We'll see
you on the next episode of Space Nuts.
Jonti Horner: Bye.
Andrew Dunkley: Bye.
Jonti Horner: You've been listening to the Space Nuts
podcast, available at
Apple Podcasts, Spotify,
iHeartRadio or your favourite podcast
player. You can also stream on
demand@bytes.um com
Andrew Dunkley: this has been another quality podcast
production from bytes.com
um.