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Gravitational Wonders, Fast Radio Bursts & Your Questions Answered · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hello, once again, thanks for joining us on
0:02
yet another edition of Space Nuts, or
0:05
more common than a daily breakfast. Uh, my
0:08
name is Andrew Dunkley. It is great to have
0:09
your company. Uh, this is a Q and A
0:12
edition, and that means, uh, we only use two
0:15
letters of the Alphabet. Uh, but, uh, we
0:18
also answer questions from the audience. Uh,
0:21
Tony wants to know about binary planets and
0:23
moons. Are there such things? Uh,
0:26
Kevin asks, can light last
0:28
forever? Alan wants, uh, to talk about,
0:31
um, a story that we did do not so long
0:34
ago. The strongest fast radio burst ever
0:37
recorded. And Rennie is back with
0:39
vertical oceans. That's all coming up
0:42
on this episode of space nuts.
0:45
Generic: 15 seconds. Guidance is internal.
0:48
10, 9. Uh, ignition
0:51
sequence start. Space Nuts 5, 4,
0:53
3, 2. 1. 2, 3, 4, 5, 5, 4,
0:56
3, 2, 1. Astronauts
0:59
report it feels good.
1:01
Andrew Dunkley: Joining us once again to unravel all of that
1:04
is Professor Fred Watson Watson, astronomer
1:06
at large. Hello, Fred Watson.
1:08
Professor Fred Watson: Andrew. Good to see you again. What a
1:10
surprise.
1:11
Andrew Dunkley: Yes, indeed. It's good to see you, too. I
1:14
actually got to see your office for real the
1:16
other day, which is nice. Yeah.
1:19
Professor Fred Watson: And you couldn't believe how small it is.
1:22
Andrew Dunkley: That's the thing about, uh, cameras in
1:24
general. They tend to make things look much,
1:26
much bigger than they really are.
1:28
Professor Fred Watson: Um, um, but, well, ah, yes, it's in. It's big
1:30
enough. But, yes, it's.
1:32
Andrew Dunkley: It does the job. I mean, mine's probably
1:35
a bit smaller than yours by the look.
1:37
Professor Fred Watson: There you go. Yes.
1:40
Andrew Dunkley: Um, now, uh, we should get straight to
1:42
business. Uh, we've got, uh, four questions
1:44
to tackle today, all text questions. And
1:47
while I'm at it, I will send out an appeal
1:49
for new questions. We're running short.
1:52
Um, we sort of threw some together the other
1:55
day because I didn't have much to work with
1:57
when I got back because I had completely
1:59
erased everything that I had done and left it
2:02
all to you and Heidi. But, um, now I
2:04
need some stuff. So send us some questions
2:07
via our website, spacenutspodcast.com or
2:09
spacenuts IO audio or text?
2:12
We don't mind which. And, uh, yeah, we'll get
2:15
stuck into them.
2:17
Um, now, Fred Watson, question one.
2:20
Hi, Fred Watson. Andrew and or Heidi, Love
2:22
the podcast. Keep up the good work, dad jokes
2:24
and bizarre background animal noises.
2:27
Congratulations on being. Wait for this,
2:29
Fred Watson. Congratulations on being the
2:32
seventh biggest, uh, astronomical
2:34
show. Seventh biggest.
2:37
Professor Fred Watson: We were,
2:39
um, seven out of the top 50. Yeah.
2:43
Andrew Dunkley: Yeah, I thought there were only eight.
2:45
Anyway, carry on.
2:48
Uh, Tony says the podcast often talks about
2:50
binary stars, but can planets and
2:53
moons also form in a paired
2:55
configuration? Could this happen or would
2:58
competing gravitational forces from larger
3:00
mass objects make it impossible? I presume
3:03
that as we haven't found any binary
3:06
planets or moons amongst the myriad
3:08
satellites in the solar system, that it's
3:10
very unlikely. But is it impossible? That
3:13
comes from Tony in Scotland. He's 20
3:16
minutes from St Andrews. He thought you'd
3:18
like to know that.
3:19
Professor Fred Watson: Yeah, that's lovely. Indeed. Uh,
3:21
Saint Andrews is right behind me on the wall.
3:25
That 17th century map there.
3:27
Andrew Dunkley: Yes, yes, I see that. Nice.
3:30
Professor Fred Watson: Um, so, uh,
3:34
yeah, the answer is yes. Um, now
3:36
clearly planets can form moons. We've got
3:39
one. And most of the other planets actually,
3:42
uh, Mercury and Venus don't have moons, but
3:44
all the rest do. Um, but I think that's not
3:47
what, um, uh, Tony's asking
3:50
about. Uh, it's about,
3:53
you know, the idea of things forming in
3:55
pairs like, like binary stars where you've
3:58
got two stars which might have fairly
4:01
comparable masses and orbit around a,
4:04
um, you know, a common centre of mass. Yeah.
4:07
Uh, which we call the barycenter. So,
4:09
um, yes, uh, objects,
4:12
stars. We think actually stars form more
4:14
commonly in pairs than singly, which is quite
4:17
interesting because we don't. The sun doesn't
4:19
have a binary companion. Got lost a few
4:22
billion years ago and we still don't know
4:23
where it is. Uh, that's one of the things
4:26
that people actually look for. Sun's sibling
4:28
star one that's got identical chemistry to
4:31
the sun. There's a few candidates.
4:33
Anyway, uh, can planets do that?
4:36
Uh, and the answer is yes. Um,
4:40
uh, and in fact it's not just
4:43
planets, but the smaller,
4:46
uh, bodies of the solar system perhaps
4:49
more readily form in binaries,
4:52
uh, as pairs. Uh, and,
4:55
uh, the kind of classic example of
4:58
this, um, is when we look
5:01
at many asteroids, not all of
5:04
them, but many of them are shaped like
5:06
peanuts in, you know, a peanut shell
5:09
because they've got two lobes to them, two
5:11
blobs which are stuck together. And that's
5:14
thought to be because, uh, they formed as a
5:17
pair of objects, uh, and gradually
5:20
spiralled together, not colliding,
5:23
but in a fairly gentle, um,
5:26
coming together, uh, where basically
5:29
they. Gravity just pulls them together and
5:31
they stick together and they often form a
5:33
region around the join, if I can put it that
5:36
way, where material tumbles down from the
5:39
surface and collects in that area. And you've
5:41
only to think of some of the best known ones,
5:44
like, um, uh. Do you remember
5:46
Arrokoth? We thought it was a snowman
5:49
in the deepest depths of the solar
5:52
system. Um, it's actually two pancakes Joined
5:54
up effectively. But that's, that's a binary
5:57
object. Um, you and I spoke
6:00
um, uh back in the um, mid
6:03
20 mid 2010s I
6:06
think about um, the
6:09
comet known as Churyumovka,
6:12
Otherwise known as 67p which looked like a
6:14
rubber duck. And that's because it had two
6:16
lobes as well, a big one and a small one. So
6:19
that two lobe um situation very
6:21
common among the smaller objects in the solar
6:24
system. Uh probably binary
6:27
systems that have come together. Not only
6:30
that, we know of many uh
6:32
asteroids that have moons, um and perhaps the
6:35
best known uh, and certainly as far as space
6:38
nuts is concerned is that pair known as
6:41
Didymos and Dimorphos, uh
6:43
which are uh, the pair of asteroids
6:46
that the DART spacecraft targeted a
6:49
few years ago. Dart uh,
6:52
clouted uh Dimorphos uh
6:55
firmly in its face, uh at a speed of
6:58
6 kilometres per second, half tonne uh of
7:01
material and changed its orbit around the
7:04
uh, around Didymos by no fewer
7:07
than 30 minutes. It was quite a
7:10
successful venture. Um, so
7:12
that's all telling you that there's pairs of
7:15
objects are very, very common. Um
7:18
and I suppose the best example
7:21
of what you might call a binary planet
7:23
because a binary planet you'd expect the two
7:25
masses to have roughly equal or similar
7:29
characteristics. Uh but the dwarf planet
7:32
Pluto and its uh, satellite
7:34
Charon, uh, I think Charon is half the
7:37
diameter of Pluto if I remember rightly. It's
7:40
quite large compared with Pluto and they
7:42
orbit around their common centre of Pluto
7:45
mass, the barycenter. So uh,
7:50
the kind of informal definition of a binary
7:52
object um is when the
7:55
centre of mass of the two halves of it
7:58
are uh, is outside either
8:01
body if I can put it that way. So the centre
8:04
of mass is somewhere in the space between
8:05
them rather than being inside as
8:08
the centre of mass of the Earth and Moon is
8:10
actually inside the Earth which is why we
8:12
consider the moon to be a satellite and not
8:14
really a binary object. Making sense
8:17
there. Um, that's basically the story. It's
8:20
a very common phenomenon.
8:23
Andrew Dunkley: Could it work for
8:26
planets the size of ours though? Let's say
8:28
Venus was out here. Could
8:30
we sort of get into that kind of dance with
8:33
Venus because they're similar sized planets.
8:35
Similar, similar mass.
8:38
Professor Fred Watson: They are, that's right. And um,
8:41
I'm sure it's not impossible
8:44
that a situation like that might
8:47
arise. I suspect why it
8:50
doesn't is it's linked with
8:52
the way we define a planet Andrew.
8:55
Uh, because to be a planet an object's got
8:58
to have pulled itself into a spherical shape,
9:01
but it's also got to have cleared all the
9:03
debris around it. Um, and
9:06
that's the process of accretion. That's
9:08
gravitational sweeping up of the material
9:12
within the old protoplanetary disc that
9:15
used to be around the sun but is now the
9:17
planets. Uh, and so I suspect that
9:19
that process itself perhaps
9:22
favours, um, single
9:24
objects, because anything that looks as
9:27
though it's going to be another object the
9:28
same size will get swept up by, uh, one.
9:31
One or the other. There'll be one of them
9:33
that turns out to be dominant. And it's
9:35
possible that that's why we see the planets
9:38
singly, because they're big and they've swept
9:40
up the material around them. Whereas when we
9:42
look at the aster moons and things like that,
9:45
dwarf planets like Pluto, um, uh,
9:48
you might find binary objects are much more
9:50
common, uh, because there hasn't been that
9:52
gravitational cleaning up of. Of their
9:55
environment, if I can put it that way. Yeah.
9:57
So I suspect that's the way it works.
9:58
Andrew Dunkley: That makes sense. Very good.
10:00
All right, so, Tony, it's taken us 10 minutes
10:02
to tell you. Yes.
10:04
Professor Fred Watson: Sorry about that, Tony, but. Yes, but
10:07
great. Give my love to Saint Andrew.
10:09
Andrew Dunkley: Yes, yes. He says he's from darkest
10:12
Fife.
10:14
Professor Fred Watson: Well, Fifes, Um,
10:16
it'll be dark soon when we get to
10:20
the winter solstice in the northern
10:21
hemisphere. But it is a very, very pretty
10:24
part of the world. Um, in fact, it was.
10:28
It might have been. James, one of the early
10:31
kings of Scotland, described it as
10:34
a beggar's mantle. Uh, what was it? A
10:37
beggar's mantle fringed with gold. And what
10:40
he was referring to is that it's this green
10:42
landscape, uh, with a lot of agriculture.
10:45
Fields are like a beggar's, uh. A beggar's
10:48
scarf, which is bits of material sewn
10:50
together and fringed with gold because it's
10:52
got golden beaches all the way around it.
10:54
Andrew Dunkley: Nice. Very nice.
10:55
Professor Fred Watson: Yeah. It's a great place.
10:56
Andrew Dunkley: Yeah. Thanks, Tony. Thanks for your question.
10:59
Next one comes from Kevin.
11:00
Professor Fred Watson: Hello.
11:00
Andrew Dunkley: I love your show. And please keep Heidi
11:03
coming back, even as a guest host with both
11:05
of you. We're actually talking about that,
11:08
uh, the three of you would be great together.
11:10
Oh, that's nice. Uh, my question is,
11:13
if the universe is 13 and a half or
11:15
so billion years old, uh, how long
11:18
before we stop seeing the light from 13 and a
11:21
half billion years ago? It seems that every
11:24
20 or 30 years we launch a new telescope and
11:26
it keeps being able to see further and
11:28
further back, but eventually the light that's
11:31
13 billion years old will have to be 4
11:33
billion years old. Uh, the light can't keep
11:36
lasting forever, can it? Uh, I hope
11:39
I'm clear enough. I know they say the
11:41
universe is expanding out to 46 billion light
11:44
years. But uh, we don't know for sure because
11:47
we can't see beyond the cosmic microwave
11:49
background. Thank you. From Kevin.
11:52
It's a good question. We have talked about
11:55
the life of light. Um,
11:58
that's a good title for a book. The life of
12:00
light before. And
12:03
I think you did say it does have
12:06
a um, you know, a
12:09
termination age. Uh,
12:11
sometimes light ends where it hits something
12:14
or and it turns into something else. But um,
12:17
yeah, I can't remember.
12:18
Professor Fred Watson: But yeah. So actually it, if it
12:21
doesn't hit something, it does pretty well go
12:23
on forever. Is that true? Yeah, um,
12:27
and it is sort of
12:30
counterintuitive. We tend to think things
12:32
that go on forever, something wrong with
12:34
them.
12:37
Um, but uh, electro.
12:40
It's not just light, it's electromagnetic
12:42
radiation. Uh, it, it basically
12:45
keeps going to infinity. Now it might get
12:47
very very weak. Um, because of the inverse
12:50
square rule. Every uh, as the distance
12:53
doubles the um, you know the intensity goes
12:56
down by a factor of four because it's the
12:58
square of the distance. Um,
13:01
but uh,
13:04
the, the question that, that Kevin poses,
13:07
uh, is, is an interesting one. I
13:10
mean uh, where it's absolutely true
13:13
that we are seeing the flash of the Big Bang
13:15
when we look at the cosmic microwave
13:17
background radiation. Um, exactly as he
13:20
says, we can't see beyond that. So we
13:23
see that as um, brightness
13:26
of the sky in microwaves, radio
13:28
waves that is everywhere in the sky and it's
13:31
almost completely uniform. It's not quite.
13:33
And it's just as well because that uh, non
13:36
uniformity is caused by the sound
13:39
waves within the Big Bang plasma
13:42
which eventually uh, is what gave rise to
13:45
galaxies and stars and all the rest of it. We
13:47
think so. Um, so yes, we're so
13:50
we're looking at a, a
13:53
boundary uh, beyond which we can't see.
13:56
And so I think um,
14:00
just clarifying uh, Kevin's
14:03
comment, um, that
14:05
46 billion light years is
14:08
probably what we call the proper radius of
14:11
the universe. In other words, it's the radius
14:13
of the universe if we could see it all. But
14:16
we can't because we're always looking back in
14:18
time. So we tend to talk about uh, co.
14:21
Moving universe
14:23
looking back at a time time. Um,
14:27
if we think in terms of look back times
14:29
rather than in terms of distances. That's the
14:32
short answer. So I'll look back time to the
14:35
cosmic microwave background radiation is 13.8
14:38
billion years. Um, but the universe probably
14:41
goes on a lot further beyond that, exactly as
14:43
Kevin said. So we can't really define its
14:45
size. Uh, but
14:48
what is interesting is that that boundary,
14:52
that cosmic microwave background boundary,
14:54
is actually receding from us at speed of
14:57
light. Uh, and,
15:00
um, I, uh, won't go into the details of why
15:02
we know that, but it is. It's moving away
15:04
from us at the speed of light, but it, but
15:06
it's still. The light that it has emitted
15:09
is still going on through the universe and
15:11
will continue to do so. Uh, eventually, as
15:14
the universe expands, it'll get very weak,
15:16
particularly if it turns out that dark energy
15:18
just keeps on, uh, going. Uh, there's
15:21
new evidence that suggests that dark energy
15:23
is, is reducing. Uh, which might mean that
15:26
one day there is a turnaround and we
15:28
might one day be back to the Big Crunch idea
15:31
that we had in the 1970s. Or the Gnab
15:33
Gibbers, uh, as Brian Schmidt calls
15:36
it, so.
15:38
Andrew Dunkley: Or the, or the Big Crack.
15:40
Professor Fred Watson: Well, the Big Crack could be if it keeps on
15:42
expanding. Yeah, the Big Rip, where space
15:44
itself just tears apart. I, um,
15:47
think that's a weird quantum phenomenon that
15:50
I'm not going to get into now. But, um,
15:52
something to look forward to anyway in the
15:53
distant future.
15:55
Andrew Dunkley: Yes, yes, we can
15:57
wait. We usually say we can't wait. We can't
16:00
wait to examine the samples from
16:02
Mars. But we can wait for the Big Rip. Or the
16:05
Gnab Gib. Definitely no hurry for that.
16:08
Uh, thank you, Kevin. Lovely to hear from
16:11
you. And this is Space Nuts Q A
16:14
edition with Andrew Dunkley and Professor
16:16
Fred Watson Watson.
16:20
Generic: Roger, your lot is right here.
16:21
Professor Fred Watson: Also Space Nuts.
16:23
Andrew Dunkley: Our next question comes from Alan. He's in
16:25
San Antonio, Texas. Recently, I was listening
16:28
to another podcast where they talked about a
16:31
news story about the strongest fast radio
16:34
burst ever recorded. Yes, we have talked
16:36
about that before. Uh, it's not an astronomy
16:38
or science podcast, so, uh, they'll not be
16:41
able to answer my question. And he thinks we
16:44
can, Fred Watson.
16:46
Professor Fred Watson: Anyway, we can put him right.
16:49
Andrew Dunkley: They mentioned that most fast radio bursts
16:52
were from billions of light years away. My
16:55
first thought was, hold on. If we don't know
16:58
the cause of FRBs, how can anyone
17:01
know the distance to the source? Hopefully
17:03
Fred Watson can answer that. Then maybe
17:05
Fred Watson will talk about the news item. If
17:07
I heard right, the, FRB that, uh, it was
17:10
talking about is intrinsically the brightest
17:13
ever, and it was in the Milky Way.
17:16
Uh, if that is the case, then it's apparent
17:18
brightness must have been so powerful that it
17:20
saturated the instruments on the telescope.
17:22
That comes from Alan in Texas. Yeah, we spoke
17:25
about that when it was first uh, published.
17:27
The uh, findings. First published. Yeah, the
17:29
um, the, the brightest um, ever
17:33
fast radio burst or something to that effect.
17:35
Uh, so we probably should talk about that
17:37
first before we um, answer
17:40
the first part of the question.
17:42
Professor Fred Watson: Yeah, the goat, wasn't it greatest of all
17:45
time? Yes,
17:49
but I think we're talking about two different
17:50
things because, um,
17:53
if you have the intrinsically
17:56
greatest of all time within our own Milky
17:58
Way, don't get fried. I think,
18:01
um. Whoops. Uh, or at least as
18:04
exactly as. As Alan
18:07
says it would fry the instruments on the
18:09
telescope. Exactly right. There certainly
18:12
have been, um,
18:14
FRBs which
18:17
uh, which come from our galaxy.
18:20
Um,
18:23
they're, they're thought to be flares
18:26
on magnetars. Uh, a magnetar is
18:29
a highly magnetic neutron star.
18:32
Intense magnetic fields, sort of unbelievably
18:34
intense. And eventually occasionally you get
18:37
flares on these things which give you this
18:39
very brief uh, burst of
18:41
radio radiation which we call an frb, a
18:44
fast radio burst. Um,
18:47
but, but that was. So that was one that
18:50
was not as powerful as the ones that we see
18:53
deep in the universe. The goats. The greatest
18:55
of all time. Um, so I'm, I'm m probably
18:58
not covering that news item very well. Uh,
19:00
but let me just briefly answer the first part
19:03
of Alan's question. Um, if we don't know the
19:06
cause of FRBs, how can anyone know the
19:08
distance to the source? It's a great
19:10
question. And um, that was one of the
19:13
puzzles. In the early era of fast
19:16
radio bursts, there were a lot of them were
19:18
detected. They only happened once. There are
19:20
a few repeating ones, uh,
19:23
but um, most of them only
19:26
happen uh, once. Um,
19:29
what you have to do is,
19:32
uh, when you detect one of these things,
19:35
you have to use a radio telescope that is
19:37
capable of pinpointing its
19:40
direction with very high accuracy. And
19:43
that's where ASCAP came in. The Australian,
19:46
uh, um, Square Kilometre Array
19:49
Pathfinder. Ascap, uh, which is a
19:51
telescope in Western Australia. It's an array
19:53
of 36 dishes. Um, and
19:56
because it's an array like that, it's very,
19:59
very good at pinpointing where signals
20:02
come from to a very high degree of accuracy.
20:04
So if you could do that, and it took them a
20:07
while to get that act together, but
20:10
they did. Um, and what you can do is then
20:13
take that position and look at that point
20:16
with a visible light telescope. And
20:19
uh, what was found consistently with
20:22
fast radio bursts is yes, they come from
20:25
distant galaxies. Uh, um,
20:28
the puzzle was that they're not usually in
20:30
the centre of these galaxies, which is where
20:31
you expect all the high energy processes to
20:34
take place because there's a supermassive
20:35
black hole there. Often they're in the kind
20:38
of suburbs of galaxies, which is one
20:41
reason why we believe they're these magnetar
20:43
flares because then they're not something
20:45
associated with a, um, high energy
20:47
supermassive black hole. They're associated
20:50
with very compact stars. So
20:54
if you can identify in a galaxy,
20:56
then you can measure the redshift of the
20:59
galaxy itself using an optical, a visible
21:02
light telescope. That gives you the redshift
21:04
which we equate to distance. Uh, so that's
21:06
how we know where they are and how far away
21:08
they are. And that's really, um, you know,
21:11
one of the great stories of the, of the FRB
21:14
saga that we have managed to pinpoint these
21:17
brief flashes of radiation, they last a
21:19
thousandth of a second at most, uh, and find
21:22
out where they come from. And it's just
21:24
because we can pinpoint their positions very
21:26
accurately and then follow it up with optical
21:28
or visible light telescopes. I have to say
21:31
that one of the, um, uh, great
21:35
collaborations uh, in that regard has been
21:37
ascap, the Australian Square Kilometre Array
21:39
Pathfinder, ah, uh, linking with the
21:43
telescopes of the European Southern
21:45
Observatory down in Chile, the optical
21:47
telescopes, what we call the VLT, the Very
21:49
Large Telescope, those four 8.2
21:52
metre telescopes that are so good
21:55
at uh, measuring the distances to very
21:57
distant objects. So that's been a really
21:59
great collaboration.
22:00
Andrew Dunkley: M. Now, um, you probably
22:03
already answered this in the past and my
22:05
brain won't let me find the answer,
22:08
but what causes fast radio bursts?
22:10
Professor Fred Watson: It's what we were saying, the idea of a flare
22:14
taking place on the surface of a, ah, highly
22:16
magnetised neutron star. Now we find
22:19
that very hard to envisage because you and I
22:21
have struggled to imagine what neutron stars
22:24
are like when we know that they've got
22:26
mountains on them that are a few millimetres
22:28
high. Um, you know, um, what is
22:31
the surface of an neutron star like? It's
22:33
just, ah, it's impossible to imagine, um,
22:36
and so it's kind of equally impossible to
22:38
imagine a flare on one of these things that
22:40
is so bright that it outshines the sun for
22:43
um, you know, for a thousandth of a second or
22:45
outshines the sun's entire radiation,
22:48
uh, uh, history for a thousandth of a second.
22:51
Amazing stuff.
22:52
Andrew Dunkley: Extraordinary. Thanks for the question, Alan.
22:54
Hope you're well.
22:57
Generic: Zero G and I feel fine.
23:00
Andrew Dunkley: Space nuts.
23:01
And to our final question today from one of
23:03
our regular contributors. Hi, Rennie. Uh, if
23:06
I look at the Earth from the distance, let's
23:08
say of Earth's moon and Earth is in a
23:11
gravitational well, why aren't the
23:14
vertical, uh, why aren't the vertical
23:16
oceans on Earth that I'm looking at not
23:19
dripping down the sides of the Earth towards
23:21
the deepest parts of the gravitational well?
23:26
Uh, I'm not sure he's serious. Maybe he is.
23:29
Um, some people look at
23:32
the planet and go, okay, it's a sphere, so
23:34
why is everything staying where it is? Why,
23:37
why wouldn't the water drip down.
23:40
Professor Fred Watson: To the bottom
23:43
a big puddle in Antarctica? Um,
23:46
well, it, yes, it is in a gravitational well,
23:49
but it's a three dimensional one. We, you
23:51
know, we look at, uh, depictions
23:54
of a gravitational well and it's
23:57
a, it's like a trampoline. It's a surface
23:59
with a dent in the middle where
24:02
you've got planet Earth or whatever,
24:05
uh, other gravitational objects, uh, we're
24:08
talking about. Uh, so a gravitational well
24:10
is, um, a good description because
24:13
that's sort of what it looks like, except
24:16
that it's a gravitational well in three
24:19
dimensions, not two dimensions, as the
24:21
surface of a trampoline is. Uh, so it's a
24:24
three dimensional entity. And it turns out
24:27
that the gravitational well is at the
24:29
centre of any gravitating object
24:32
like the Earth. So, um, yes, the
24:35
oceans do drip down, but they drip down
24:37
towards the centre of the Earth, which is
24:40
where the gravitational well is, uh,
24:43
because it's a three dimensional well, not a
24:45
two dimensional one. I do love the idea of
24:48
the oceans kind of running down the side
24:50
though. It's quite nice to think
24:53
about. Fortunately, fortunately
24:55
not the way it is because the, uh, the whole
24:58
thing exists in three dimensions and we've
25:00
got, um, the centre of the Earth as being the
25:02
bottom of the gravitational well.
25:04
Andrew Dunkley: Indeed. Simple, uh, answer to that
25:07
one, Rennie. So thanks for sending your
25:09
question in and once again I'll appeal for
25:11
new questions. If you'd like to send them
25:13
into us, jump on our website. I'll just do a
25:16
search for Space Nuts podcast on your
25:19
search engine and uh, find us there and, uh,
25:21
send us text or
25:24
audio questions, uh, um,
25:27
through the AMA tab up the top. And
25:30
don't uh, forget to tell us who you are and
25:32
where you're from. We always like to know
25:34
that just so that we can spam you.
25:37
Professor Fred Watson: Um.
25:39
Andrew Dunkley: Yes, all right.
25:40
Professor Fred Watson: Is that what it's for?
25:41
Andrew Dunkley: No, of course not.
25:44
Of course not. We only send spam to people
25:47
who volunteer for it.
25:49
Professor Fred Watson: Yes, that's right.
25:51
Andrew Dunkley: Uh, thanks, Ronnie, Alan, Kevin and
25:54
Tony for your questions today. And thank you,
25:56
Fred Watson, as always. It's been great fun.
25:58
Generic: Fun.
25:59
Professor Fred Watson: It's, it's great to answer the, you know,
26:01
questions like that or at least have a crack
26:03
at answering them. They're, uh, always
26:05
thought provoking. And, um, thanks to all our
26:07
listeners. And thanks too to you, Andrew, for
26:09
carrying the show forward.
26:10
Andrew Dunkley: Oh, my pleasure. I enjoy it. It's great
26:13
fun. And we'd thank Huw in the studio, except
26:16
he didn't turn up today. He went for a swim
26:19
and ended up in Antarctica. So,
26:21
um, he
26:24
loves it down there. He's, um. Yeah,
26:27
he's a fun guy. Uh, and, uh, that's it
26:30
from, uh, us for another week. We'll see you
26:32
very soon on another edition of Space Nuts.
26:35
And from me, Andrew Dunkley. Bye. Bye.
26:38
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26:41
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26:46
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26:49
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26:51
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26:53
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