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White Dwarfs, Black Holes & Cosmic Oddities Unpacked | Q&A · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hi there. Thanks for joining us on another
0:02
episode of Space Nuts. This is a Q and A
0:04
edition. This is where we answer audience
0:07
questions. Well, we read them out or we
0:10
listen to them and we nod
0:13
and then we go home. Uh, today we're
0:15
going to be discussing white dwarf stars. An
0:18
interesting question, a double barreled
0:20
question in fact. Um, we've got
0:23
one about uh, the different size of black
0:26
holes. Gosh, a question about black holes.
0:28
How odd. Uh, the effect of being in orbit
0:32
come up and Casey wants to know about
0:34
some of the oddities that exist in the
0:37
cosmos. We'll cover all of that in this
0:40
edition of space nuts. 15
0:42
seconds. Guidance is internal. 10,
0:45
9, ignition sequence start.
0:48
Professor Fred Watson: Space nuts.
0:49
Andrew Dunkley: 5, 4, 3, 2. 1, 2, 3, 4,
0:52
5, 5, 4, 3, 2, 1. Space
0:55
nuts. Astronauts report it feels good.
0:58
And Fred Watson brought with him today his
1:01
brain the size of a planet to answer all your
1:03
questions. Professor Fred Watson, what's an
1:04
astronomer at large? Hello Fred Watson.
1:06
Professor Fred Watson: Hello Andrew. Fancy seeing you here.
1:09
Andrew Dunkley: It's unusual, isn't it, really?
1:13
We've got a fair bit to get through, so we
1:15
might just get straight into it, uh,
1:18
as they say in Britain, we'll muck in.
1:21
Professor Fred Watson: Um, I think it's, you'll find it's muckin
1:24
nookin mukin.
1:25
Andrew Dunkley: I've got to get the accent right.
1:27
Professor Fred Watson: Yes, of course.
1:29
Andrew Dunkley: All right, uh, our first question comes from
1:32
Bloomington, Indiana. Two questions, if I
1:34
may, about white dwarf stars. After a very
1:37
long period of initial cooling, white
1:40
dwarf stars undergo crystallisation before
1:42
eventually transforming into theoretical
1:45
black dwarf objects. So the
1:48
questions are, uh, what is the process of
1:50
crystallisation and how might crystallisation
1:53
slow the further cooling of a white dwarf for
1:56
such an incredibly long time? Thank you very
1:58
much for your terrific podcast, Keep Smiling
2:00
in the Land down under. That comes from Mark.
2:03
Thank you, Mark. Lovely to hear from you. We
2:06
don't talk all that often about white dwarfs,
2:08
although we have had them pop up a couple of
2:11
times lately. But um, yeah, you might want to
2:14
tackle that uh, process of crystallisation
2:16
first. What is that?
2:19
Professor Fred Watson: Uh, so, um, you need to sort of think about
2:22
what a white dwarf is before you get to the
2:24
crystallisation.
2:25
Andrew Dunkley: I suppose so, yeah, yeah. Is that what our,
2:28
uh, sun's going to turn into?
2:29
Professor Fred Watson: Yeah, yeah it is. So, uh, a couple of weeks
2:32
time, I think, uh, it was it
2:35
uh, after tomorrow, wasn't it? I can't
2:37
remember. Yeah, anyway, um, it's or the, the
2:39
Andrew Dunkley: billionth of a year after tomorrow.
2:43
Professor Fred Watson: Yes, it's about, uh, so
2:46
it will be in the region of 5 billion
2:49
years.
2:50
Andrew Dunkley: Oh, that's okay.
2:50
Professor Fred Watson: Then have to put up with that. So
2:53
uh, as well, let's take this and as an
2:56
example, so the um, the outer.
2:58
So what, what basically happens at the
3:00
moment? We've got this reaction taking place
3:02
that converts hydrogen into helium
3:06
and produces a few other things as well.
3:08
There are other reactions going on, uh, many
3:11
of which produce carbon. Uh, and so
3:14
carbon sort of builds up in the core
3:17
of the sun over
3:20
time and in particular as, as it
3:23
gets nearer the end of its life it becomes
3:25
quite carbon rich, uh, the
3:28
nuc. So um,
3:32
when it sheds its outer
3:35
atmosphere and turns into what we call a
3:38
planetary nebula. Nothing to do with planets,
3:40
it's just that the early astronomers thought
3:41
they looked like planets, but they're
3:43
actually clouds of gas. Yeah, um, William
3:45
Herschel, who called them planetary nebulae,
3:47
he called a lot of things their names that we
3:50
still use. Very eminent astronomer.
3:52
Anyway, you get a planetary nebula,
3:55
uh, but the, the core of the
3:58
star that's left
4:02
uh, behind basically
4:04
collapses under its own gravity because it
4:07
doesn't have the radiation any longer to
4:10
support a swollen star. If
4:13
I can put it that way. Radiation's gone.
4:16
So uh, it's still. But it's incredibly hot,
4:19
which is why it's a white dwarf. It's because
4:23
the radiation pushes it into a very
4:26
extreme white part of the spectrum. A bit
4:29
like uh, a lot of the headlights on cars
4:31
these days with LED, ultra white
4:34
LEDs, it's that sort of thing. Um, but for
4:37
different processes it's very hot. That's why
4:39
it radiates the whiteness. Uh, but it
4:42
basically uh, is an object with
4:45
uh, it's in a state of what's
4:48
called electron degeneracy. And that means
4:52
that the electrons
4:55
are uh, the only thing stopping it collapsing
4:58
into something more dense
5:01
like ah, a black hole. So it's this electron
5:04
pressure that uh, sort of stops a
5:06
further collapse. Uh, and
5:09
essentially um, you've got.
5:14
Matter does very, very funny things under
5:16
those circumstances because it's under
5:19
extreme compression. Uh, and
5:22
so you've got basically
5:26
a carbon oxygen rich
5:28
carbon core which uh, in the
5:31
initial stages, uh, as Mark
5:34
says, uh, um, after a very
5:37
long period of initial cooling, that's what
5:38
he says in those initial stages, uh,
5:41
it's liquid, It's a liquid core, a liquid of
5:44
carbon and oxygen. Uh, and
5:47
it's very hard for us to imagine
5:50
that now as that cools it,
5:53
uh, it's when the crystallisation takes
5:56
place, it becomes a lattice of rather than
5:59
a slushy liquid of these Atoms,
6:02
they form a lattice structure which we call a
6:05
crystal. Uh, and
6:08
that uh. So Mark asks
6:11
what's the process of crystallisation? It's
6:13
the cooling of the, of the liquid core
6:15
further. Uh, so uh, under the extreme
6:18
pressure you get basically diamond
6:20
forming, that's what it is. Um,
6:23
and so that crystallisation, it means that
6:26
the core is diamond related.
6:29
Um so uh,
6:32
that's the sort of end product.
6:35
Um, so
6:39
then that process of
6:42
diamond formation actually releases
6:44
heat, what we call latent heat. It releases
6:47
heat and so it slows down the
6:50
star's cooling. Uh, and apparently it slows
6:53
it down by roughly a billion years.
6:57
Uh, and so the
7:00
suggestion, uh, there's a comment here that
7:02
um, I'm looking at that says Gaia data,
7:05
that's the measurement of the positions of
7:07
billions of stars and their colours.
7:11
Recent uh, Gaia data suggests this is a
7:13
common 10 million year long high density
7:16
phase. Uh, but when it,
7:20
when it, when um, when you've, when
7:23
you've basically not quite sure why, there's
7:25
a conflict of numbers there which are
7:28
struggling to understand. But if you've got
7:30
the star cooling delayed by a
7:33
billion years and then
7:36
the cooling phase keeps on going,
7:38
uh, you've got then many tens of billions of
7:41
years before it becomes a cold and dead
7:44
object, uh, which we call a black dwarf.
7:46
Uh, I don't think there are any black dwarfs
7:48
yet because the universe isn't old enough for
7:50
them to, them to be, to have been created.
7:53
Andrew Dunkley: So they're theoretical. But they um,
7:56
might suppose in terms of
7:59
theoretical, they're probable.
8:01
Professor Fred Watson: Yes, that's right. That's about right.
8:04
Andrew Dunkley: Okay.
8:05
Professor Fred Watson: The diamond stars, I mean it's a nice
8:07
concept, isn't it?
8:07
Andrew Dunkley: Yeah. Gee, it's such a. Time frames
8:10
that you just can't, yeah.
8:13
Contemplate. It just makes us seem so tiny
8:16
and small and insignificant, doesn't it?
8:19
Professor Fred Watson: Uh, yes. Although we're important to each
8:21
other.
8:22
Andrew Dunkley: Yeah, that's, that's true. Um, I, I was
8:25
just doing a bit of research while you were
8:26
talking. Apparently they think 97%
8:29
of stars in the Milky Way will become white
8:31
dwarfs.
8:32
Professor Fred Watson: Yeah, that's right. They're, they're, you
8:35
know, they're the ones that go supernova are
8:38
the rarities.
8:40
Andrew Dunkley: That's good though. I mean imagine if 97
8:42
of the stars in the Milky Way became black
8:44
holes. We'd all be in trouble.
8:46
Professor Fred Watson: Yeah.
8:48
Andrew Dunkley: Could be messy.
8:49
Professor Fred Watson: Uh, that, that's right. Yes we
8:52
would, it would be a much more
8:55
um, inhospitable universe.
8:57
Andrew Dunkley: Indeed. Thank you, Mark.
9:00
Hopefully we adequately answered Your
9:02
question.
9:02
Great to hear from you. Uh, we've got an
9:05
audio question now. This one comes from
9:06
Steve.
9:07
Speaker C: Hi guys. Love your podcast. Keeps
9:10
me uh, awake a little later every
9:13
evening listening.
9:16
Steve here from Tin Can Bay
9:18
in Queensland. Very dark sky
9:21
place actually. And my question is to
9:24
do with different sized black holes
9:27
and gravitational gradient.
9:30
Not that I know much about this. I was
9:32
wondering, um, if you fell into a
9:35
smaller black hole, believe this
9:38
specification effect where the
9:41
gravity at one end of your body to the other
9:43
would tear uh, you apart, that if you
9:46
free fell into a
9:49
super large black hole,
9:52
wouldn't the gravitational gradient be
9:56
more even out across the plane and
9:59
you uh, would just free fall into it?
10:03
Can explain that and make
10:06
more sense of it.
10:08
Andrew Dunkley: Thank you, Steve. Uh, Tin Can Bay. What a
10:10
beautifully named place. I love it.
10:13
Professor Fred Watson: Have you ever been, Andrew?
10:15
Andrew Dunkley: I haven't been there, no.
10:16
Professor Fred Watson: No, I haven't either.
10:18
Andrew Dunkley: Yeah, sounds like it's a great place to
10:20
visit, especially at night if it's a dark sky
10:22
area. Fantastic.
10:23
Professor Fred Watson: Yep. Cheque it out.
10:24
Andrew Dunkley: Um, so we're talking about different sized
10:27
black holes and if you fell into them, well,
10:30
we all know what would probably happen. But
10:32
uh, what if it's super large? Uh, is
10:35
its gravitational gradient spread evenly
10:37
and does that mean you could fall into it
10:39
without too much trouble?
10:42
Professor Fred Watson: I think, um, so if you think about the um,
10:45
the gravitational, well the shape of this,
10:48
this sort of vortex that is the black
10:51
hole in gravity. Um, yes,
10:54
for a bigger black hole, ah, black hole, uh,
10:57
it will be less steep. It will
11:00
basically extend over a much wider area than
11:03
for a small black hole and will start
11:05
off less steep because it's, it's a gentler
11:08
slope, um, which means, and
11:11
what that's telling you is the event horizon
11:13
is bigger, uh, for a larger
11:16
black hole, a larger mass black hole, but the
11:19
end product is pretty well all always
11:22
the same. Uh, maybe your
11:24
spaghettification will be a bit gentler, but
11:27
you're always going to end up in a very, very
11:29
steep gravity gradient. Um, and
11:32
yes, I think, um,
11:35
uh, you know, Steve's question, Steve's
11:37
thinking I think is right, that
11:40
the way that gradient changes is what
11:43
uh, tells you how quickly you're going to be
11:45
spaghettified. Um, and it changes
11:48
more slowly for a larger mass black hole than
11:51
for a smaller black hole. But uh,
11:54
you're still going to wind up in deep trou,
11:56
um, you're still going to get spaghettified
11:59
in the end.
12:00
Andrew Dunkley: Yeah, I suppose depending on the size and
12:02
gravity effect of the black hole, it could be
12:04
spaghettified or linguinified
12:07
you know, it could, it could be variables
12:10
like that.
12:11
Professor Fred Watson: It could be. Yes, that's right. Yes. Yeah.
12:14
Andrew Dunkley: Well, I haven't thought to fly pastified.
12:16
That would be. That would be really
12:18
different.
12:19
Professor Fred Watson: Yeah.
12:20
Andrew Dunkley: Uh, very unusual. But, um, I think in the
12:22
movie Interstellar, they broke the laws of
12:24
physics when they actually did successfully
12:26
go through a black hole at one point in that
12:29
film. Um, I think they did. I think they
12:32
described it as a. It was a supermassive
12:34
black hole, but it was very, very well
12:36
tempered, something to that effect.
12:40
Um, but yes, that, that, um. Because what
12:43
they were looking for was only available to
12:45
them, uh, in terms of research on the
12:48
inside of a black hole. And so they had to go
12:51
in there and find what they needed to save
12:53
the world.
12:54
Professor Fred Watson: Yeah, Y.
12:57
Yes, that's right.
12:59
Andrew Dunkley: Great film though. One of my favourites. Uh,
13:01
thank you, Steve. Hopefully we answered, uh,
13:04
your question today on Space Nuts. Uh,
13:07
and you're listening to a Q A edition with
13:10
Andrew Dunkley and Professor Fred Watson
13:12
Watson.
13:16
Speaker C: M. Space Nuts.
13:18
Andrew Dunkley: Okay, uh, next question, Fred Watson. Over
13:20
the years, Fred Watson has explained how
13:22
astronauts orbiting the Earth are affected by
13:25
gravity about the same as us because
13:28
they are in effect continually falling. When
13:30
they leave orbit and head into space, how far
13:33
do they need to travel before they no longer
13:36
feel the effects of gravity? Also,
13:39
uh, when they orbit the moon, is it the same
13:41
as orbiting the Earth? Uh, that one comes
13:43
from Wayne. Hi, Wayne. Thanks for the
13:45
question.
13:48
Professor Fred Watson: Yes. So how far do you need to
13:51
go?
13:52
Andrew Dunkley: I had a question, but it dropped out of my
13:53
head. But, um, uh, I suppose that the first
13:56
point we look at, if you're orbiting Earth,
13:58
you're continually falling, but
14:00
you're still, uh, feeling weightlessness,
14:03
aren't you?
14:04
Professor Fred Watson: Yes. So that's how it works. You're
14:07
being pulled towards the centre of the Earth
14:09
by gravity. Uh, and you're feeling much the
14:12
same gravity as we do on the surface. Uh, but
14:14
what's stopping you from falling is your
14:16
forward motion. You're always, um,
14:19
moving, uh, in an orbit that means
14:22
that you never actually reach the centre of
14:25
the Earth. Uh, which is just as well because
14:27
it's not a nice place. No, um, not really,
14:30
but. Okay. So then you, uh, you fire your
14:34
rockets, you do translunar injection or
14:36
whatever that is. Uh,
14:39
wherever you're going, if you're going to the
14:41
moon, it's a translunar injection, that's
14:42
what they call it, which puts you.
14:45
Takes you from the orbit that you're in, a
14:48
circular orbit around the Earth and puts you
14:50
into a different orbit which,
14:53
uh, will carry you out towards the moon.
14:56
Uh, and if you don't do anything, uh,
14:59
as happened with Artemis 2, there were a
15:01
couple of minor course corrections, but
15:03
basically that will bring you back to Earth
15:05
because you're still in an orbit,
15:08
even though it's a very long thin one. It was
15:10
a figure of 8:1 in the case of Artemis 2. But
15:13
you're still in orbit, you're still being
15:14
pulled towards the Earth. Uh, the Earth's
15:17
gravity is
15:19
reducing, uh, as you go further out,
15:24
uh, um, but you're still
15:27
feeling it. And okay, uh, if
15:29
you go out, uh, to Saturn,
15:33
um, you're still feeling the Earth's gravity.
15:35
Um,
15:39
there comes a time, uh, which is when
15:41
you expand your voyage beyond the
15:44
Earth moon system. There comes a time when
15:46
you're feeling the sun's gravity more so
15:50
of technically in orbit around the sun. And
15:51
that's what happens with interplanetary
15:54
probes. You go to Saturn,
15:58
you're in an orbit, but you're still being
16:01
pulled back towards the sun. And if you don't
16:03
do anything when you get to Saturn, like fire
16:06
your braking rockets to slow you down, to put
16:08
you in orbit around Saturn, if you don't do
16:10
anything, you'll wind up going back to the
16:12
sun. You'll end up coming back.
16:15
Andrew Dunkley: Is that what's happening with comets and
16:17
asteroids?
16:18
Professor Fred Watson: Yeah, yeah. They're just feeling the pull of,
16:21
so, um, comets in particular. Out there in
16:24
the Oort cloud, they get a little bit of a
16:25
nudge. That means that um,
16:28
their velocity is not enough to keep them
16:31
from falling in towards the sun. Uh,
16:34
and so they do. And it takes them a long time
16:36
to get in towards the sun. Hundreds of
16:39
thousands of years, but they still do it.
16:41
They're still in orbit.
16:43
Andrew Dunkley: Okay, so how, how far would
16:46
you have to go outside the solar system
16:49
to not feel that effect?
16:53
Or you're always going to feel something
16:55
somewhere.
16:55
Professor Fred Watson: Yeah, gravity's not something that
16:59
disappears. It actually falls
17:01
away and uh, effectively becomes zero at
17:04
very big distances. But it's still there, as
17:07
witnessed by the oak clouds a light year away
17:10
or something like that. Um, you know,
17:13
um, the,
17:16
what eventually happens in interstellar space
17:19
is you feel, you still feel the pull of stars
17:22
around you, including the sun, but
17:24
you're also under the influence of the
17:27
galaxy itself. So our,
17:30
uh, sun for example, is in orbit around the
17:32
galactic centre. It's falling towards the
17:35
galactic centre, but its velocity of, uh,
17:38
200 kilometres per second,
17:41
uh, actually about nearer
17:44
to 250 kilometres per second around the
17:47
centre of the galaxy. That's what's stopping
17:49
it falling in towards the galactic centre
17:52
goes around in about 200 million years.
17:55
It's weird. Yeah, it is
17:58
weird. It's very weird.
17:59
Andrew Dunkley: I mean we're talking about that next with
18:01
oddities in space, but that's one of them. I
18:04
mean we've got this situation where these
18:06
things been doing this for billions of years
18:09
and that's not going to stop in a hurry.
18:12
And, and even when our
18:15
solar system ultimately has the
18:18
sun go, you know, boom,
18:21
it's still going to be happening like that,
18:24
is it not?
18:26
Professor Fred Watson: Yes, well, I mean the sun will
18:28
swell, uh, to possibly
18:31
engulf the inner planets, but the centre of
18:33
its gravity is still where it is now,
18:36
effectively. Um, so yes.
18:39
Andrew Dunkley: What about maybe uh, you know, getting
18:42
yourself into a Lagrange point?
18:45
Professor Fred Watson: Yeah. So that's where those points
18:47
are, where gravity and often
18:50
centrifugal force balance out.
18:53
So you've got this stable point
18:56
M. You still. They're not that stable
18:58
actually. The, you can tip one way or the
19:01
other. It's more like a saddle in the
19:03
gravitational pull, but they're still
19:06
more stable.
19:07
And I was actually going to mention that, um,
19:09
that leads then to this idea of the
19:12
interplanetary superhighway.
19:16
The planets and their Lagrange points are
19:20
kind of interlinked by these low energy
19:22
pathways through the solar system. So if you
19:25
push uh, an object into one of these low
19:28
energy pathways, they are feeling the gravity
19:30
of not just the sun and the Earth, but the
19:33
moon and other planets as well. But they can
19:35
wander their way along one of these pathways,
19:38
uh, till they get to the other Lagrange
19:40
point. And that's something that's been
19:42
looked at for slow speed
19:44
interplanetary travel, maybe for supply ships
19:47
or something like that. But you're going to
19:49
take decades to get to wherever you want to
19:52
go.
19:52
Andrew Dunkley: And by then, um, um, your
19:55
iPhone's probably defunct.
19:58
Uh, the technology would be too old.
20:00
Professor Fred Watson: Yeah, yeah, yeah, yeah.
20:02
Andrew Dunkley: Uh, so if you get far enough away from the,
20:05
the pull of the Earth and the moon, the sun's
20:08
going to grab you.
20:09
Professor Fred Watson: You, you feel other things as well. Yeah,
20:11
Jupiter's another.
20:12
Andrew Dunkley: Oh yeah. Well it, yeah, it does not
20:15
like being ignored.
20:16
Professor Fred Watson: No it doesn't. That's right.
20:18
Andrew Dunkley: In fact, that's another factor in our
20:21
uh, solar system that Jupiter, because of its
20:24
size and gravitational effect, is
20:28
a good barrier for Earth when it comes to
20:31
big, um, rocks heading in this direction.
20:34
Professor Fred Watson: That's right. That's been um,
20:37
postulated as one of the reasons why the
20:40
Earth has evolved life because
20:42
it's protected to some extent, particularly
20:45
by comets. From comets, uh,
20:48
by Jupiter, which turns a lot of comets
20:51
from having fallen in from the Oort Cloud.
20:54
They get grabbed by Jupiter's gravity and
20:55
become what we call short period comets.
20:58
Uh, so. But I've read papers that
21:01
say the opposite is true. Jupiter's effect is
21:04
not as protective as we'd like it to be. And
21:07
maybe some of Jupiter's
21:10
malevolence, uh, is when it redirects comets
21:12
into short period orbits and we run into
21:14
them.
21:16
Andrew Dunkley: Yeah, not nice. Not nice at all.
21:19
Um, so basically, doesn't matter where
21:22
you go, you're going to be affected by some
21:24
sort of gravity?
21:25
Professor Fred Watson: That's right. Yes, you will. Even if you're
21:27
deep in interstellar space, you'll still be
21:29
feeling the effect of the gravity as a whole,
21:31
as that
21:32
Andrew Dunkley: means weightlessness is a myth in real terms.
21:35
Professor Fred Watson: Um, yeah. Yes,
21:38
in a sense it is. Uh,
21:42
weight needs gravity. Um, and
21:46
if you are experiencing forces
21:49
that balance that, uh, force of gravity, then
21:52
you're weightless and that's what happens
21:53
when you're in orbit. There you go.
21:55
Andrew Dunkley: All right, Good question. Thanks, Wayne.
21:58
Lovely to hear from you. Our final question
22:00
in this episode comes from Casey.
22:03
Speaker C: Hi, guys, this is Casey from Colorado.
22:06
There's a lot of weird stuff in space and I
22:08
was wondering what some of your favourite
22:09
oddities are. Thanks for the podcast
22:12
and shout out to Huw for fixing the audio
22:15
submissions. Bye.
22:17
Andrew Dunkley: Thank you, Casey. Oh, Huw did some work. My
22:19
goodness. Um,
22:22
only took a couple of months. Um, no, thanks,
22:25
Casey. Uh, oddities in space. I love this
22:27
question, uh, because there are many,
22:30
uh, if you go through an official list, of
22:32
course, number one would be dark matter,
22:35
number two would be dark energy.
22:37
Um, those are obvious. Um,
22:41
have you had a think about this one,
22:42
Fred Watson? What have you come up with?
22:44
Professor Fred Watson: Well, you know, we've just been talking about
22:45
what, Something that's really odd and
22:47
counterintuitive. A diamond star?
22:49
Andrew Dunkley: Yeah.
22:50
Professor Fred Watson: Um, a, uh, metal asteroid. That would
22:53
be an oddity. We think Psyche is a metal
22:56
asteroid. We'll find out when the Psyche
22:58
spacecraft reaches Psyche. I, uh,
23:00
think in 2031 or thereabouts. I think it's
23:03
got a way to go yet. Uh, maybe not
23:06
that far anyway. Sure, it's going to happen.
23:09
Um, but I think
23:14
some of the coincidences, uh, are
23:16
oddities. And the one that always
23:19
blows my mind is the coincidence of the sun
23:21
and the moon looking to be the same size in
23:24
the sky. That's a complete random thing
23:27
with no physical
23:30
mechanism that has caused that. And you've
23:32
got these two objects which are the most
23:33
prominent objects in our skies and they
23:35
appear to be exactly the same size.
23:38
Andrew Dunkley: And it's just a coincidental, just a
23:40
coincidence proximity thing, isn't it?
23:42
Professor Fred Watson: Very weird.
23:43
Andrew Dunkley: Yeah. Actually I've got one that involves the
23:45
moon I just, uh, found. And um,
23:48
despite the fact that we look at it in the
23:50
night sky and it's round, um, they say it's
23:53
lemon shaped. Is that true?
23:56
Professor Fred Watson: Um, it's
23:59
got a slight deviation. Yes, that's right.
24:03
Uh, ah, a bulge.
24:06
Because it's always feeling,
24:08
uh, because it always faces the same
24:11
side to the Earth, I think it's slightly
24:15
elongated in that direction.
24:17
Andrew Dunkley: Okay.
24:17
Professor Fred Watson: Um, I think that's the case. But
24:20
in the, from the direction
24:23
we see it, uh, because that lemon
24:26
shape is towards us, what we see
24:29
is an object that is almost perfectly
24:31
circular. The moon. Very, very,
24:34
very, very, uh, perfectly circular.
24:37
Andrew Dunkley: And while we're talking about that, because
24:39
you just popped into my head while you were
24:41
talking, the sun in terms of,
24:44
um, being spherical is almost the perfect
24:47
circle, isn't it?
24:48
Professor Fred Watson: It is, um, it differs from
24:51
being spherical by something like 10
24:54
kilometres and it's 1.4 million
24:57
kilometres in diameter. That's right. And
25:00
actually that raises another oddity in my
25:02
mind, uh, which we've talked about many
25:05
times. The mountains on neutron stars. Oh,
25:07
yes. A few millimetres high.
25:10
Andrew Dunkley: Yeah. That's just crazy, isn't it?
25:13
Yeah. M. If you do
25:16
Google searches for these things, it's
25:18
millions of them. But uh, you know, if
25:21
we stick to our solar system for a moment,
25:23
um, a day on Mercury
25:26
is twice as long as a year.
25:28
Professor Fred Watson: Yes, that's right.
25:29
Andrew Dunkley: Is that because of its, um, uh,
25:32
what do you call it, um, tidal locking? Yes,
25:35
tidal locking does sound.
25:36
Professor Fred Watson: It's not quite tidally locked, but there's a
25:39
relationship between the rotation and the
25:41
revolution period, which is what you've said.
25:44
Yeah, very weird. Yeah. Some of the
25:46
planets have very weird things. I mean,
25:49
um, Uranus on its side, that's an
25:51
oddity. Um, that's very
25:54
strange. But we think that's caused by a
25:56
collision in the early solar system.
25:58
Andrew Dunkley: Yeah. Uh, all the planets
26:01
could fit between Earth and the moon.
26:03
Professor Fred Watson: Yes, that's right.
26:04
Andrew Dunkley: I mean that just blows my mind.
26:10
Professor Fred Watson: It's actually. Go ahead.
26:12
Andrew Dunkley: No, uh, that would make for some very
26:14
interesting nights of observation, I imagine.
26:16
Professor Fred Watson: Yeah. And it's an issue. It's um,
26:19
quite interesting because the moon's, you
26:22
know, the moon's orbit around the Earth is
26:24
not circular, so sometimes it's nearer than
26:27
at others. Perigee is when it's at its
26:29
closest apogee is when it's at its furthest.
26:32
Uh, the planets. The eight planets. Sorry,
26:35
seven planets. Because the Earth's not part
26:37
of it. Uh, they will only
26:40
fit between the Earth and the Moon when
26:43
the Moon is near apogee, if it's near
26:46
perigee, you can't squeeze them in and it
26:48
becomes a bit ugly, really.
26:49
Andrew Dunkley: Yeah, I imagine so, yeah. Uh, I like
26:52
this one. A teaspoon of neutron star
26:55
weighs the same as the human population.
26:59
I don't know how they figured that out.
27:01
Professor Fred Watson: Uh, yes, yeah, uh,
27:04
that's right.
27:06
Andrew Dunkley: But, yeah, they're very heavy. Heavy.
27:10
Professor Fred Watson: The one I like, the numerical one that I like
27:12
is. And again, it's completely
27:15
bizarre. It's got no reason for it. But the
27:18
number of astronomical units and an
27:20
astronomical unit is the distance from the
27:22
sun to the earth, 150 million million
27:25
kilometres. The number of astronomical units
27:27
in a light year is almost
27:30
exactly the same as the number of inches in
27:33
a mile.
27:35
It's very, very weird. 63,000 is the
27:38
number, so there's a few digits that don't
27:40
fit, but.
27:41
Andrew Dunkley: Yeah, that's incredible. Uh, and then, and
27:44
then there's these ones that sound, um,
27:46
weird, but so logical when you
27:49
explain it. That there are stars in the
27:51
universe that we will never see.
27:54
Professor Fred Watson: Yeah, uh, yes, because the light will never
27:57
reach us. That's right.
27:59
Andrew Dunkley: And that's probably why we'll never, ever
28:02
find alien life too far away.
28:06
Professor Fred Watson: Maybe. Maybe. Maybe the
28:09
SETI people aren't giving up.
28:10
Andrew Dunkley: No, they're not. Uh, now, I did say that,
28:13
um, um, a day on Mercury is twice as long
28:16
as a year. But on Venus,
28:19
I think, um, it's a similar
28:22
storey, isn't it? A day on Venus is longer
28:25
than a year.
28:26
Professor Fred Watson: Very long. Yeah. I can't remember the
28:27
details, but Venus basically rotates the
28:30
wrong way around. Uh, so
28:34
its North Pole is facing downwards.
28:37
That's what gives you the funny rotation. You
28:40
define the north and south poles as
28:43
being the direction or the point on a
28:45
planet where, if you're looking at it from
28:48
above, it's rotating anti clockwise.
28:51
Because virtually everything in the solar
28:54
system is rotating and revolving anti
28:56
clockwise as seen from above the. The North
28:58
Pole. Weird.
29:01
Andrew Dunkley: Oh, you like this one, Casey? Neptune has
29:03
only, uh, completed one orbit since it was
29:05
discovered. M Very
29:08
quirky, very quirky. And look, there must
29:11
be billions of these.
29:14
Like, um, you know, the, the weirdness of
29:17
rogue planets or, um. Yeah, or the sun
29:20
losing a billion kilos per second.
29:23
Professor Fred Watson: That's right, yes.
29:24
Andrew Dunkley: We found out the secret to that somebody
29:26
could make billions of dollars on
29:27
Professor Fred Watson: Earth, I reckon needs quite high
29:30
temperatures to do that.
29:32
Andrew Dunkley: Yeah, yeah. Um, and the list goes on.
29:34
You got any more?
29:36
Professor Fred Watson: Uh, well, you know, even black holes are
29:39
things so weird. And the fact
29:41
that we can actually, here's another
29:43
statistic that's mind blowing.
29:45
Um, it's the, the
29:48
ligo, um,
29:50
interferometer, which measures gravitational
29:53
waves. The accuracy that we
29:56
position it or know the mirrors to
29:59
is something like a thousandth of the
30:01
diameter of a proton. It's just incredible.
30:04
But that's technology rather than space
30:06
oddities really. That's technology. Yeah,
30:09
that blows my mind too.
30:11
Andrew Dunkley: And another one that's um, not talked about
30:14
much. But our days are getting longer. I
30:16
think there was an official report not so
30:18
long ago about uh, the new length of a,
30:21
of a day on Earth. But they uh, are getting
30:23
longer because our rotation's
30:26
slowing. Is that what it is?
30:28
Professor Fred Watson: Yeah, it actually speeds up occasionally as
30:30
well due to probably the movement of
30:33
ice and things of that sort. But the overall
30:35
trend is definitely slowing of the rotation.
30:38
Andrew Dunkley: Yeah, there are so many of them, Casey.
30:40
Um, and if, if anybody comes uh,
30:43
across one they'd like to ask us about,
30:45
please, uh, please send it in. But uh, thanks
30:47
Casey. That was a lot of fun.
30:49
Uh, and uh, that brings us to the end of the
30:51
show, Fred Watson.
30:53
Professor Fred Watson: Yes. Another show in the bag.
30:55
Andrew Dunkley: And yeah, we're in the can as you, you know.
30:58
That's the shop talk way of saying it.
31:00
Professor Fred Watson: Shop talk. Yes, in the can. In the can.
31:03
Um, and hopefully there'll be many more,
31:05
Andrew.
31:06
Andrew Dunkley: That would be lovely. Uh, we'll, we'll catch
31:08
you on the next one in uh, a few days time.
31:11
Fred Watson, thank you.
31:12
Professor Fred Watson: Sounds like it. Thanks a lot. Take care.
31:14
Andrew Dunkley: Professor Fred Watson Watson, astronomer at
31:15
large. And thanks to Huw in the studio, uh,
31:18
who couldn't be with us today due to
31:21
some kind of oddity, a space
31:24
oddity. Um, and don't uh,
31:26
forget to visit us online at our website, uh,
31:29
or on social media and send us your questions
31:32
via the Ask me anything link at the top of
31:34
our webpage, uh, in audio
31:37
form or uh, as a text. And uh,
31:40
don't forget to tell us who you are and where
31:42
you're from. Always lovely to hear from you,
31:44
wherever you are, are in the world and from
31:46
me, Andrew Dunkley. Thanks for your company.
31:48
We'll catch you on the next episode of Space
31:50
Nuts. Bye bye. You've
31:53
been listening to the Space Nuts podcast
31:57
available at Apple Podcasts, Spotify,
32:00
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32:06
Professor Fred Watson: has been another quality podcast production
32:09
from bytes.com.