Heidi Campo: Welcome back to another episode of space nuts.
Voice Over Guy: 15 seconds. Guidance is internal.
10, 9. Ignition
sequence start. Space nuts. 5, 4, 3,
2. 1, 2, 3, 4, 5, 5, 4,
3, 2, 1. Space nuts. Astronauts
report. It feels good.
Heidi Campo: I'm your host for this summer, filling in
for Andrew Dunkley. My name is Heidi Campo.
And joining us is professor Fred Watson,
astronomer at large.
Professor Fred Watson: Uh, good to be here, Heidi, as always. And
you're also our host for this winter here in Australia.
So, yeah, lovely to talk. And um, I think we've got
some pretty great questions from our, uh, listeners for this episode.
Heidi Campo: We do. We have some really fun, uh,
uh, not episodes. We have some fun questions.
Um, our first question today is
Martins from Latvia. And here
is his question.
Martins: Hello guys. It's, uh, Martins from
Latvia. Um, I've been loving your show. Been
listening since 2017. And, um,
so I have a question about dark matter.
Okay, just kidding. I have a question about speed,
uh, of light. So we have two objects.
One object is on Earth and the other one is traveling
in space at the speed of light. After some
time it comes back and the object that's on Earth is
older than the other object.
So why is that happening again? Why? They aren't
the same, uh, age. I mean. Yeah,
there's something to do probably when you're reaching speed of light that
time is slowing down or something. But why it's slowing
down? Why isn't it, uh, like. Yeah,
just curious. And uh.
Yeah, and I have, um, some
dad joke for your, uh, arsenal,
Andrew. So, uh, how do you
put a space baby to sleep? You rock it.
So anyways, guys, cheers then.
Yeah, have a good one.
Heidi Campo: Well, I think those space babies will
being well with those jokes. Thank you so much, Martinez.
That's a. That was a good one.
Professor Fred Watson: Yep. Space babies, uh, always need to be
rocked. That's right.
So, uh, now that's a great question.
Um, um, I have visited Latvia actually.
Uh, some years ago we did a tour there. I do
remember, um, you know, Heidi, because we've
talked about it before. I'm very fond of trains. We
traveled on a little railway, uh, through the snow and
through, uh. Because we always visit these places in
winter, uh, through snow and woodlands. And it
trundled along at something like
nine miles an hour. Maybe it
was a fast walking pace
because it was a very old line, but it was a lot of fun.
Anyway, enough about Latvia.
Uh, let's get to the speed of light, which is basically
what Martin's question is about.
Um, this is, it's one of the
fundamental aspects of
relativity. Uh, Einstein's two theories
of relativity. One was about motion. The other was about
gravity. It's the one about motion that covers this. That's
called the special theory of relativity. Uh, dated
1905. And it turns out
that the thinking that Einstein had had,
uh, leading up to this. Was
that we know that the speed of light
is a bizarre quantity.
Because in a vacuum it's always the same.
We know also that it's the maximum
speed that anything can attain. In fact, you can't actually achieve
the speed of light with an object. Because
you would have to put infinite energy in to get it to the speed of
light. And we don't have infin infinite energy. So light
and its other electromagnetic waves.
They are the only things that can travel at the speed of light.
But if you had something that you are accelerating.
Well, let me just go back. The speed of light is
almost like a magic number. It's not magic because it's a
very round number. It's about 300,000 kilometers per second.
Uh uh, it is, however,
the fact that it doesn't change in a vacuum. And it
doesn't matter how fast the source is moving. You'd expect
if you have a source that's moving. That sends out a
beam of light. Um, the source's speed
would add to the speed of light. And the speed of light
would increase. But it doesn't doesn't work like that.
And once you establish that, then
it turns out. And there's
some quite sort of simple ways of
seeing how this might work. Which we don't really have time
to talk about. But some of the books about special
relativity. That talk about people looking at somebody
moving on a train. Show you how the geometry
works. That, uh. Because the speed of light
is always the same. Then what it tells
you is perceptions of time and distance
must change. And so the key
thing here. And the point that, uh, Martins
is raising. Is that if you've got
an observer who is stationary.
Compared with somebody who's moving at a very high
speed. Nearly, uh, the speed of light or
yeah. It doesn't matter whether it's near the speed of light or
not. The effect works. But it's when you get
nearer the speed of light. That it becomes noticeable.
Um, the time that you observe.
Um, that moving person,
uh, experiencing is slower. So your
time's ticking away as normal. And
the person who's moving past you. Their time
is ticking away as normal. But when the
stationary person if you could see the clock
on the moving vehicle or whatever it is. Train Going
at nearly the speed of light. Just to mix a few metaphors there,
um, what you would see is their clocks would seem to be going
much more slowly than yours is. And
that's the time dilation effect. And
yes, it means that, um, if you can
then bring these two back together, the moving
person has experienced less time
relative to you than you have. And
that's the. It's sometimes called the twins paradox.
Because if you take two twins, one goes off at the
speed of light, comes back again, or nearly the speed of light,
comes back again there they have aged much less
than the twin who stayed put.
So that's the bottom line. And
it's such a counterintuitive concept that it
is really hard to get your head around. But we know it works.
Uh, in fact, um, the demonstration,
um, the practical demonstration of this phenomenon
happening in reality, uh, I think it was just
before the Second World War. Might have been round about the
same time. But there are things called cosmic rays which are
bombarding the Earth all the time. These are subatomic particles that
come from space. Um, and they are
predominantly a species of
subatomic particle called a muon. So these
muons were observed coming down
through space at, uh, nearly the speed of light.
And we know how long they take to
decay in the laboratory. But
their decay time was much longer when
they were observed coming in at the speed of light, nearly the
speed of light, the time had dilated. So the decays
were much longer than what we observe in the laboratory when
they're not stationary, but they're going
much more slowly. So it is a proven fact
this works. Uh, if we could
build a spacecraft that would get us to. I can't remember
what it is. I think it's
99.99998% of the speed
of light. Head off for 500
light years, come back again. Uh, you will be 10
years older, whereas everybody else on Earth
will be a thousand years older. So it's that
sort of thing. Your time has slowed down relative to what
they've experienced.
Heidi Campo: I had a weird nightmare about that the other night.
Professor Fred Watson: Oh, did you?
Heidi Campo: It was the strangest thing. I had a nightma. Um,
somebody put me in, like, some kind of a cryo sleep. And I woke up and so
much time had passed that everyone I knew had died. And so I
had them put me back in cryo sleep for
thousands of more years until we discovered the technology to travel
back in time so I could go back in time and link
back up with everyone I loved.
Professor Fred Watson: That's A pretty good one is that.
Heidi Campo: I have a very active dreamscape. Uh,
at night I wake up exhausted.
Professor Fred Watson: Okay.
Heidi Campo: All right.
Well, our next, uh, question has a little bit of philosophy in it.
Um, this, this question is coming from Art
from Rochester, New York. And it's, ah, it's quite a
long question. So let's, uh, grab a cup of
tea here. Art
says, I was listening to the June 13 program
concerning the flying banana, which prompted me to
submit my first question to Space Nuts.
It is a question I had been pondering for some time. You
will be glad to hear it is not a black hole question, but
rather a what if question. The great
American philosopher Julius Henry Marx once
postulated, time flies like an arrow, fruit
flies like a banana. Based
on empirical evidence, I can confirm that fruit
flies like a banana. My question
revolves around time flying like an arrow.
To the best of my understanding, when we shoot off
rockets to the moon or Pluto, in order to get
there accurately, the rocket scientists use an
amphimerus. M. You'll have to correct me on the
pronunciations of that or possible
amphimerds as a sort of a map.
If faster than light space travel were
possible, how could one navigate from point A to
point B? Is it possible to develop an
ephemeris for faster than light
travel? Thank you, Art from Rochester, New
York.
Professor Fred Watson: A great question, Art. And, uh, yeah,
your pronunciation is correct. Ephemeris is what
these things are, and ephemerides is what a
lot of them, ah, are. So what's an ephemeris? Well,
uh, the original
meaning, um, and I guess this really is still
the meaning of the word is, uh, to
predict where, uh, planets
are going to be, uh, in the future,
where celestial objects are going to be.
So, um, going back to my
master's degree, uh, back, you know,
150 years ago, my work was on,
um, the orbits of asteroids. And
so there were two problems. First problem was how
do you take observations of an asteroid? And remember, all we had
in those days was the direction
that you could see measured with a telescope. How do you
turn that into knowledge of the orbit of
the asteroid, uh, in three dimensions? And you can
do it. You need at least three observations to do that, but you
can do it. You can mathematically deduce the orbit
from just three directions in space. But then
once you've got the orbit, what you want to know is where it's
going to be in the future, what's its direction in space
going to be? And that is what an ephemeris is.
It's how the position of an object changes,
uh, in the sky, uh, over time. Um,
so it comes from the word ephemeral, meaning
stuff that's temporary. Uh, so an
ephemeris, uh, is the,
basically it's a table of where an object
will be over a given amount of time. And of course it's
critically important these days because we now know
that, which we didn't know when I did my master's
degree. We now know that the Earth's locality
is pretty heavily populated with asteroids. And there's,
you know, we might want to know where they are
just in case one's uh, heading our way. So
um, I, you know, I think the question, Art's uh, question
is uh, a good one in the sense
that, okay, he's saying, yes, we, we
use ephemera, um, ephemerities to, to
basically navigate to
objects. Um, it's
actually a little bit more than that because we, we
use effectively a three dimensional map of where these,
these planets are, uh, in order
to dictate where they're going to be when
your rocket arrives there. And that's critically important of course,
because you want the rocket to get to the orbit
of for example Pluto, as Art mentions,
uh, when Pluto is going to be where,
whereabouts the rocket is. You don't want to reach the
orbit of Pluto and find Pluto somewhere else. That's why you
need uh, an ephemeris. But
uh, if you could travel faster than the speed of light,
and we've already shown that that's impossible,
uh, in this episode because you need infinite energy to do
that, uh, to reach the speed of light. But if you
could, um, the ephemeris would still
work. Um, you would need to put
in a negative number for the.
I think the speed of light
actually goes into ephemeris calculations. I remember it
well. But I think you uh, put in a
factor. It wouldn't be a negative number. It would be a factor that
would allow for the fact that you were traveling at faster than the
speed of light. So you could do it. It's not
an impossible mathematical problem.
For what it's worth.
Heidi Campo: Well that was fantastic. Uh, I just about understood that
too.
Professor Fred Watson: Sorry.
Heidi Campo: Uh, no, you always do such a great job of explaining these.
Um, my IQ is going up every time I'm
um, involved on these, uh, these episodes. And also
great questions. We have some of the
smartest, smartest listeners. I mean these people
are, are brilliant.
Speaker C: Space nuts.
Heidi Campo: Um, our next question is another audio
question, um, from David from Munich.
And it's a little bit of a longer question as well. So,
so we are going to go ahead and play that for you
now.
Speaker C: Hey guys, David from Unique here. Uh,
shout out to Andrew, Fred and
Jonti and I heard that you're a bit
shorter in questions so I thought that's my chance
to submit one. I'm currently
looking at the picture from um, or taken by
the James Webb Telescope. You know the first one, the first um,
deep space which was also presented by President
Biden back then. And I realized that the
galaxies do differ in
their color pretty much. So there are
more white ones, uh, orange ones and also
reddish ones. And I um, wonder
how is that, Is it due to the fact that
um. Or is this like the red shift because they're
moving away, which I kind of
doubt, but I don't know what, what is it else?
Or is there so much material of a different,
of different kind in the galaxy that appears
for us more red or more blue.
So would be nice if you could explain that.
And um, also I wonder a bit.
Let's imagine we would travel to this far
distant galaxies. Um, if we
could do it potentially
would it not be some kind of
travel through the time?
So because when we look back there, right. We see them
on their early stages. So till
it's a long time until um, until the
light reaches us. And if you would travel to that
far distant uh, galaxies you would
basically. Or what I imagine is like you would
travel through time, right. So if you did, the moment
you come closer and closer the galaxy or
maybe let's think of a single planet would then change
its appearance, right? So you would see that it's
alter, uh, it shifts maybe its base or
it merges with another galaxy. Um,
is my thinking correct, Would it like the
far. The closer you come the more it would
change its shape and it, I
don't know, colors maybe.
Um, and things you would see.
Um. Yes, thanks for taking my questions. Um,
like the shop and, and um,
till then.
Heidi Campo: Well, thank you so much. Um,
that was David from Munich. Thank you. That was a
well thought out question. Fred, I'm so curious.
Professor Fred Watson: They were great questions Heidi from
David and in fact the answer to both his
questions is yes. Um,
so David's asking whether
the color changes that we see in the
images, uh, of these deep fields as we
call them, uh, looking way back in
time, uh, whether those different colors of
galaxies is caused by
the different redshifts of these galaxies.
And that's the bottom line. But there's a few
caveats here. Let me just explain what I Mean, um,
redshift is the phenomenon that,
uh, as light travels through an expanding universe,
uh, the universe is expanding, light is making its
way through the universe, but as it goes, the universe is getting
bigger. And so the light's wavelength is
actually being stretched. Uh, and,
uh, as you stretch the wavelength of light, it goes redder. It goes to
the redder end of the spectrum. And so that's what's happening.
But the caveat that I mentioned is that these
are actually false colors in the sense that
the James Webb telescope is an infrared telescope.
So it is looking at light that our eyes are not
sensitive to. It's actually redder than red light that it's
looking at. So what the mission
scientists do is they,
um, they take the shortest
wavelengths that the Web can see,
which are really beyond our.
They're redder than red for us, for our eyes,
but they're the shortest wavelengths that the red can detect, and
they make that blue in their colors. And then the
longest wavelengths that the Web can detect, they make it
red in their colors and that. So that mimics
what we would see with our eyes,
uh, with visible, you know, visible light, but it
mimics it moved into the infrared. So it does mean
that as objects, uh, you
know, get redder, uh, in the infrared spectrum,
we see them redder, uh, in the James Webb telescope images.
And that's exactly the reason the most
distant objects are so highly redshifted,
that you're seeing them as red objects compared with
the white objects, which are the much nearer ones.
So David's right on that front. His second
question, uh, what would some of these galaxies
we're looking back, you know, up to. I think the record is
looking back 13.52 billion years at the moment,
which is 280 million years after the birth
of the universe. It's a big puzzle as to how
galaxies got so
big and so rich, um, in that short period
of time. But that's for the
cosmologists, not for us. Um, they'll work it
out. It'll be okay. Uh, the bottom line, though, is
that if you could forget about the journey, because
we can't travel the sort of speeds that you need. But
if you imagined yourself, uh,
instantly transported from
our, uh, vantage point here on Earth to
one of These early galaxies, 13.52
billion years, billion light years away, what you
would see would be a galaxy that might look a lot like
ours. It has evolved because
you're seeing it. I mean, you've got to imagine
we're being transported
instantaneously. So that what we see is what's happening
now. That galaxy will have had 13.52
billion years of evolution. It'll be quite different. It might
actually be quite a boring galaxy compared with the
very, uh, energetic, uh, infant galaxy that
we look at with the James Webb telescope. Complicated
answer to a simple question, but David's
right on the money.
Heidi Campo: That is such an interesting way of thinking about that. I, um,
I'm going to be spending, I'm going to be spending a while
wrapping my head around that one.
Professor Fred Watson: Okay, we checked all four systems and seeing where to go
space nets.
Heidi Campo: Um, our last, our last question of the evening is from
Daryl Parker of South Australia.
Daryl says, G' day, space nuts. I'm
not sure of the best way to ask this question, so
I'll just ask it the best way I can. That's
usually, that's usually the, the best way.
Uh, do objects, meteors, asteroids,
comets, planets, stars,
solar systems and galaxies
produce heat as they move through space? Is
it friction or is friction a thing
in the vacuum of speed and the vacuum of space?
Thank you in advance. And that's Daryl from South
Australia.
Professor Fred Watson: Uh, another great question. Um,
so if space was a complete
vacuum, and as I'll explain in a minute, it's
not quite. But if it was a perfect vacuum
with nothing in there, then, uh,
there would be no friction,
uh, as Daryl's calling, um,
would be, uh, uh, you know,
there'd be nothing to, uh, to limit the
speed of motion, uh, of an object moving through it.
And it wouldn't get hot. There would be no friction to heat it.
And I think the way Daryl's thinking here, and it's quite right
to, uh. When a spacecraft enters the Earth's atmosphere,
uh, it's the friction between the spacecraft itself
moving against the air molecules that causes it to be heated and
gives us this heat of reentry. There are a few subtleties to
that, but that's basically the way it works. So things moving
through an atmosphere get hot. Um,
now, uh, space
beyond the Earth's, uh,
atmosphere is not a vacuum.
It's very nearly a vacuum. And that's why you can put a
satellite up and it'll stay up for 200 years or
whatever. And it's why, you know, the Moon doesn't come
crashing down to Earth. In fact, the moon's going the other way. It's moving away
from the Earth very slowly, but
the, um, it's nearly
a vacuum, but it's not quite so.
Uh, there is basically, um,
a very, very slight braking effect,
uh, which in the Earth's vicinity, the Earth's
atmosphere doesn't just stop, it sort of fades away. So
even 10,000 kilometers away,
there's still a little bit of residual atmosphere, which would have a
slowing effect on a spacecraft. When you get into
interplanetary space, there's a lot
of dust and there's, there's also subatomic
particles there. When you get to interstellar space, the space
between the stars, there is something that we call the
interstellar medium, uh, which is
basically the radiation and
particle environment of interstellar space.
There are subatomic particles all through space.
Now there, it's still so much of a vacuum
that there's nothing really to heat a spacecraft.
So Voyager, as it ventures through
interstellar space, is on the brink of interstellar space.
Now that, uh, won't get hot because of that,
um, because the friction is far too small.
But when you do see its effects, uh,
they are on very big scales. And we do
see, uh, when we look at
some objects deep in space, for example in a gas cloud,
uh, a nebula, where, um,
maybe there are stars forming, sometimes you see objects which
are moving through that gas cloud. And what you can see
is a shock wave, uh, being generated.
And sometimes that causes star formation,
that shockwave of the gas cloud.
Um, now, yes, that's Jordy agreeing with me there.
Uh, he's just come back from his walk, so
he's very enthusiastic about this idea. Uh,
he's probably seen a shockwave. Um,
and a shockwave is what you get when something moves rapidly through the
atmosphere. You know, that's what causes the sonic boom of a
supersonic jet. Um, so
with very big objects in gas
clouds in space, then you do get that sort of
effect. The interaction between the moving object and
its surroundings generates a shockwave and would generate
heat as well. So under certain circumstances the answer is
yes, Darrell, but probably for most things it's
no.
Heidi Campo: So.
So, Fred, I don't know if you'd have time for a follow up question
of my own. Yes, um, so
I guess I never really thought of, um, the
gravity atmosphere around planets having
different layers. It's like, I knew there was layers, but it's like to really
think, okay, you know, it gets thinner and thinner and thinner, but
there's still particles, uh, being pulled into that atmosphere. But it
just, it spreads out quite a ways well
beyond our atmosphere. Are there points of space,
and you may have already mentioned this, but are there points of space where there's
particles floating around that are not being affected by
any gravity at all? Or is every
part of space affected by something's
gravity?
Professor Fred Watson: Um, yeah, pretty well. Um, the thing about
gravity is it, it goes on for
infinity. Um, it's, ah, it's a
bit like actually light is the same. Electromagnetic
radiation will not stop. It just keeps going until
it gets too weak to be detected. You're talking
about a dribble of, you know, hardly any photons.
Gravity is the same. We don't know whether gravity
has a subatomic particle equivalent. We think it might have, and
we call them gravitons, but they haven't been discovered yet. But
yes, uh, that's actually, you know, it's
why, uh, an object like
Pluto, way out there in the depths of the solar system,
is still in orbit around the sun, even though
it's all these, what is it, five, six billion
kilometers away. Um, the gravity of
the sun is still a force
because gravity goes on forever.
Uh, but of course, when you get way
out into interstellar space, then you might feel
the sun's gravity, but you'd also feel the gravity of other
stars. Uh, and so I think you're
right that there is always going to be a sort of gravity
background, uh, because of the
objects which are in the universe. Maybe
it's pretty near zero in the space between
galaxies, uh, which is pretty empty, although there are
subatomic particles there too. Uh, but,
uh, yeah, but no, it's a. It's a very, um,
A very compelling force is gravity, which is just as
well because otherwise we wouldn't exist.
Heidi Campo: There's always something pulling. It's just going to
be stronger or weaker. No matter if it's.
No matter if it's the biggest gap in
the known cosmos,
there's still a little thread pulling us together.
Oh, that's so beautiful. That's kind of cool. We're all connected
somehow.
Professor Fred Watson: That's a connection. That's right. Yeah.
Heidi Campo: Um, Fred. Well, this has been a
very enlightening Q and A episode
of Space Nuts. Thank you so much for
sharing your wealth of knowledge with us.
Um, while your rooster. I'm sorry, your dog.
Sings his song in the background.
Professor Fred Watson: That's what he sounds like. I know. Um, his voice
hasn't broken yet.
Heidi Campo: It's kind of cute. It's endearing. Um, thank you so
much.
Professor Fred Watson: This has been, been.
Heidi Campo: This has been fantastic. And, um, we
will, we will, I guess, catch you guys next
time. Please keep sending in your amazing
questions. And, um, real quick, before
we go, we are going to play a, uh,
another, um, another
update for you. So this is your little Treat for
listening to the whole thing. We've got an update from Andrew,
your beloved regular host. I know you
guys probably miss him because your questions are still
addressed to him, but, um, he's on his trip
around the world. Going to let that, um,
play back now.
Andrew Dunkley: Hi, Fred, hi, Heidi, and hello, Huw
in the studio.
Andrew back again, reporting from the Crown
Princess on our world tour. Uh, since I spoke to you
last, our, uh, cruise has made news all over
Australia. You might have seen some of the reports or heard some of
the news about some of the conditions we've had to
deal with. When I last spoke to you, I was explaining
how we were heading into rough weather. We got off to a pretty
rocky start. Well, it got much,
much worse. We were having lunch in
one of the restaurants at the back of the ship and
we got hit by a weather front. It felt like we'd
been rammed and the. The ship
tilted over 7 degrees and it stayed there
for the rest of the day. It just hit us out
of nowhere. The captain had to do some heavy
maneuvering to get us, uh, into. Into a, you know, better
position. And they had to move, um,
the ballast to, uh, keep the ship,
uh, balanced and upright as much
as they could. Uh, yeah, it was pretty harrowing.
And the weather never got better, uh,
until we got into Adelaide and were in protected
waters. But, um, the Adelaide was fantastic. Went
to, uh, Handorf, as I mentioned, that little German
village where the German people. People came in all those
years ago. They were, um, they were basically
escaping, uh, Prussian oppression when they came out
here in the 1800s. And, um, yeah, made it, made a German
town, which is fantastic. Had, uh, a good look
around Adelaide, although the weather was terrible. We went to Mount Lofty,
which is one of the best views in Australia. And all we saw was
cloud and very strong winds. It
was, uh, it was quite nasty. Got
back on board, uh, we had to stay the night in Adelaide because
of the conditions, hoping they'd settle down. And we did have
some good sailing until we got to the
West Australian border and then another weather front hit
us and it got rough again
and. Yeah, gosh. And just to top it all
off, we had a galley fire in the middle of the night at one
point, which they dealt with very, very quickly. So it's been
a bit of a dog's, uh, breakfast of a cruise
in some respects, but we're still having a fantastic
time. We stopped at Fremantle again,
um, because of the weather. We were very late and so we
stayed the night. We have friends in Fremantle so We spent the
evening with them. It was fantastic. And we
set sail again yesterday, headed west.
We leave Australia now, headed for Mauritius. That'll be
a seven day crossing of the Indian Ocean.
So that's where things are at with our uh, current
tour. Um, we're really enjoying
ourselves. I must confess. The crew here
is fantastic. And uh, you know, with
over 2,000 Aussies on board, we outnumber everybody
about 10 to 1. Which is, which is good.
But so many nationalities. Hope all is well back home
and in Houston of course. Heidi, look forward to talking
to you next time. Uh, no, Aurora.
Heidi Campo: Australa.
Andrew Dunkley: Australis. Missed out completely. Couldn't see that.
So um, hopefully when we get up north we'll see the other
end of the uh, country and ah, see if
there's any lights up there. North. So until next
time, Andrew Dunkley signing off.
Voice Over Guy: You've been listening to the Space Nuts. Podcast
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Heidi Campo: See you later, Fred.
Professor Fred Watson: Sounds great.