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Black Holes, Gravity Theories & the Quest for Planet Nine · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Hi there. Thanks for joining us. This is a Q
0:02
and A edition of Space Nuts. My name is
0:04
Andrew Dunkley. It's good to have your
0:06
company. Uh, today, uh, we will be
0:09
hearing questions about, uh, the
0:12
universe being inside a black hole. In fact,
0:14
I think they're suggesting it was born in a
0:16
black hole and is stuck in there. And how do
0:19
we get out? We'll also be looking at a new
0:21
gravity theory. Uh, theory Hubble tension.
0:25
Not surprisingly, questions about planet nine
0:28
with the most recent announcement of
0:30
something being out there that's not planet
0:32
nine. And, um, getting
0:35
gravity assistance to Max Delta V.
0:38
Those are all the questions coming up on this
0:40
episode of space nuts.
0:42
Voice Over Guy: 15 seconds. Guidance is internal.
0:45
10, 9, ignition
0:48
sequence time. Uh, space nuts. 5, 4, 3,
0:51
2. 1. 2, 3, 4, 5, 5, 4,
0:54
3, 2, 1. Space nuts. Astronauts
0:57
report it feels good.
0:59
Andrew Dunkley: And Fred Watson Watson is with us again to
1:01
solve all these little riddles.
1:03
Professor Fred Watson: Hello, Fred Watson. Hello Andrew. Nice to,
1:05
um, help you solve the riddles.
1:08
Andrew Dunkley: Uh, I don't know anything.
1:11
That's why I bring you along.
1:12
Professor Fred Watson: Oh, good. Well, I'm about to be of assistant.
1:14
Andrew Dunkley: Makes it so much more interesting when
1:16
there's two people talking. Monologues are
1:18
just so boring, don't you reckon?
1:23
Unless it's a super interesting person like
1:25
yourself. Right.
1:26
Professor Fred Watson: No, I'm, I'm capable of boring the pants off
1:28
people as, uh, people have assured me before.
1:31
So that's all right.
1:34
Andrew Dunkley: So we've got a lot to get through and uh,
1:37
it's, it's even trickier this week because we
1:40
do have a technical, uh, issue, which means
1:43
you are going to have to lip ring.
1:46
Professor Fred Watson: Okay. Uh,
1:49
so. Right. I'll do my best.
1:51
Andrew Dunkley: We'll see how that.
1:52
Professor Fred Watson: I'm wondering where the lips are going to be.
1:54
That's the only thing.
1:55
Andrew Dunkley: Yes, yes. Well, the first set of lips come
1:57
from Paul. Uh, so let's hear his question.
2:00
Paul: G' day, Fred Watson, Andrew, Johnty,
2:03
Heidi, whoever happens to be at the helm. Uh,
2:06
this is Paul from Sunnybris, Vegas. Thanks,
2:08
uh, for doing a great job as always.
2:10
I have a quick question about surprise
2:13
black holes. Um, Dr. Shamir
2:16
put out a paper recently about
2:19
his ideas regarding the fact that, uh,
2:22
some galaxies are spinning one way and
2:25
uh, a lot of them, most of them the other
2:26
way. And another fellow chipped in,
2:29
Nikodem Poplowski from New
2:32
Haven, suggested that maybe that was because
2:34
our universe was born inside a black hole.
2:37
If that is true, how the heck did we get
2:40
out? And if we didn't get
2:42
out and we're still inside, then
2:46
how is that possible given that, you know,
2:48
anything that goes inside a black hole, uh,
2:51
is spaghettified according to our current
2:53
thinking and therefore incoherent. I mean I
2:56
know I'm incoherent, but you know what I'm
2:59
talking about. Talking about when it comes to
3:00
ordinary baryonic matter. Uh,
3:03
love to get your thoughts on this.
3:06
Anyway, uh, keep up the good work and
3:09
catch us later. Cheers.
3:11
Andrew Dunkley: Thank you Paul and hope all is well in
3:13
Brisbane. Paul is asking about the universe
3:16
being born inside a black hole. How do
3:19
we get out? And why don't we get
3:21
spaghettified as a consequence of that?
3:24
Amongst many other things. But uh, that was
3:27
the basis of the question.
3:28
Professor Fred Watson: So. Yes. So as you've already uh, mentioned,
3:31
I didn't hear any of Paul's question there.
3:33
Not at all. However, I did listen uh, to it
3:36
yesterday. So I've got a bit of an idea of
3:38
what Paul was suggesting. The fact that um,
3:41
we have uh, new
3:43
observations which uh, have been made with
3:46
the James Webb Space Telescope,
3:49
uh, that um, are
3:51
intriguing in the sense that uh,
3:54
these scientists, uh, and they
3:57
are basically uh, mostly
4:00
located at Kansas State University.
4:03
Uh, the, the rotation of galaxies in the
4:06
deep universe isn't random. Uh,
4:08
you'd expect, you know, galaxies to
4:11
be rotating in.
4:14
They can only go one way or the other. But
4:16
you would expect an equal balance of
4:19
rotations. Uh, and uh,
4:22
what find, uh, or what these scientists
4:25
find at Kansas State University using
4:28
the James Webb Space Telescope
4:31
Advanced Deep Extra galactic survey or
4:33
jades, um, what they find is out of
4:36
263 galaxies,
4:39
um, which you know, which
4:43
give away their rotation because we know that
4:45
spiral arms nearly always trail. There's at
4:47
least one galaxy where the spiral arms are
4:49
leading but most of them trail.
4:52
And what they find is that out of these 263
4:55
galaxies, about two thirds of them
4:57
are going clockwise and the rest are going
5:00
anticlockwise. And that is an imbalance.
5:03
That's a statistically significant imbalance,
5:06
uh, that suggests that something's going on
5:08
that we don't understand and that
5:11
leads to the possibility that
5:14
perhaps the universe itself is
5:17
rotating. Um, and I've seen
5:20
other um, papers um, on
5:23
this topic that suggest that maybe the
5:25
universe rotates once in every 500 billion
5:27
years. That's one figure that I've seen
5:31
now, um, a consequence of the
5:33
rotating universe. And I think this is where
5:36
Paul's question went. I'm trying to remember
5:38
having heard it yesterday, uh, is that
5:42
it lend some weight to the
5:45
idea that the universe is
5:48
inside a black hole. Uh, in other
5:51
Words that there is an event horizon at some
5:54
huge distance from where we are,
5:57
uh, and we are all within this
5:59
black hole. Um,
6:03
what does that mean for observational
6:05
cosmology? I suspect it's going to be very
6:08
difficult for us to confirm
6:11
that ever. Uh, and I
6:13
think, um, you know, this is
6:16
speculative research. It's important
6:19
research because you, you, you want to know
6:21
um, how some of these things interact. And I
6:24
might just mention, and I think we've
6:25
discussed this before, Andrew, on space nuts,
6:28
that the idea of a rotating universe actually
6:31
relieves some of the issues, uh, that
6:34
we find uh, in observing the universe. One of
6:37
them is the Hubble tension. And I know
6:38
there's a question coming up about that. Um,
6:41
so a rotating universe has certainly
6:43
attractive possibilities, but we absolutely
6:45
don't know whether it is a rotating universe
6:48
and indeed whether that means that we're
6:50
inside a black hole. Uh, so what I was going
6:52
to say was the idea of a universe within a
6:54
black hole is akin to the idea of
6:56
multiverses. The idea that um,
6:59
um, multiple universes exist and we
7:02
are just one of them. I'm not really, I
7:04
don't think giving a sensible answer to
7:07
Paul's question, partly because I couldn't
7:08
hear it. But I think he was basically asking,
7:11
you know, what happens? How does it happen?
7:14
Uh, how are we not being spaghettified?
7:16
That's because, uh, I can tell you the answer
7:19
to that. Uh, we're not in a region, um,
7:22
of the black hole where the um,
7:26
gravitational pull is
7:29
changing very, very rapidly with space.
7:33
And that's what makes a black hole
7:34
spaghettify. You, you go from one point to
7:37
another and your gravitational pull is very
7:39
different. So your head feels a different
7:40
gravity from your feet and you get
7:42
spaghettified. We're not in a place where
7:45
that would be happening if we were inside a
7:47
black hole. But uh, you know, all bets are
7:50
off because inside a black hole, uh, there
7:53
might. We're in a different dimensional
7:55
space. A black hole is a singularity. Are,
7:57
ah, we in a singularity? A singularity is a
7:59
point with no dimensions. Work that one
8:02
out. So we'd have to be almost in a different
8:05
dimensional space. So it's an interesting
8:07
question, um, to which I don't
8:10
think anybody knows the answer, but there are
8:12
a few people who are probably thinking
8:14
through it a lot more clearly than I am.
8:17
Andrew Dunkley: Well, Paul mentioned uh, a physicist by the
8:19
name of Nicodem, um, Poplaus,
8:22
uh, he's one that's put this theory
8:25
forward that um, our
8:28
observable universe is not just a part of a
8:30
larger universe, but is in fact the interior
8:33
of a black hole within a larger context.
8:36
Professor Fred Watson: Yes. So you've got extra dimensions somewhere
8:38
out there within, uh, which we exist.
8:41
Uh, that's right. It's, um, uh,
8:44
you know, I, I, Yes, I remember, um, checking
8:47
out the, the researchers that, uh, that Paul
8:49
mentioned yesterday when I looked at it. Uh,
8:51
it's interesting stuff. Yeah.
8:54
Andrew Dunkley: What do you think, personally? I mean, is
8:56
there any possibility that this could be
8:59
real?
9:00
Professor Fred Watson: Um, to me it's on the same level
9:03
as does heaven exist? Uh, you know,
9:06
it's questions to which we really can't
9:09
find answers. We can theorise, we can
9:12
conjecture, we can speculate, we can write
9:14
equations down. And probably some of the
9:17
equations do support the idea that we're
9:19
within an event horizon. It goes back a very
9:21
long way. It's not a new idea at all. Um,
9:24
but, um, I mean, people have put new numbers
9:27
on it, I think, and, um, new observations. I
9:30
think we, we watch this space. Next time this
9:32
question comes up, I might be able to hear it
9:34
properly and might be able to give a more
9:35
cogent answer.
9:38
Andrew Dunkley: Yes, indeed. I'll be working on that
9:40
technicality.
9:41
Professor Fred Watson: I don't, I'm sure it's not your fault,
9:42
Andrew. I know what these gremlins are like.
9:44
We get them all the time.
9:46
Andrew Dunkley: Yeah, I'll blame the equipment. Never ever,
9:49
though.
9:49
Professor Fred Watson: Never the place. New Z. No, that's true.
9:54
Andrew Dunkley: Thank you, Paul. Hope we covered that
9:55
adequately, as we strive to do here on Space
9:58
Nuts.
10:03
Professor Fred Watson: Space Nuts.
10:04
Andrew Dunkley: Uh, our next question, Fred Watson, comes
10:06
from Casey in Colorado. In fact, he has
10:09
two. Could you please explain the new
10:11
theory of gravity in simple terms?
10:15
Does it, uh, have any merit? And could you,
10:17
uh, please explain hubble tension and what it
10:20
means for our understanding of the universe?
10:23
Professor Fred Watson: Yes. Uh, so
10:26
that's the answer. The answer is yes. Yes, I
10:28
can. The new
10:31
theory of gravity, which I like very much.
10:34
Um, this comes from scientists in Finland,
10:36
which is a place that I like very much as
10:38
well. Um, and it's
10:41
what they've done, you know, they've
10:44
taken, um, a step
10:46
forward. And I'm assuming
10:49
this is the, uh, this is indeed
10:52
the, um, the, uh, the, the
10:55
new theory that case is speaking about,
10:57
because we get nearly one every week, a new
11:00
theory of gravity. But this is the latest
11:02
one. Um, it's, uh, as I said,
11:04
it's from, uh, it's from, uh, Finnish
11:07
scientists, uh, at Aalto, uh,
11:10
University. Um,
11:13
so it's what they've done
11:16
is what Einstein tried to do for the last,
11:18
for 30 years of his life. Uh,
11:21
which is to unify quantum
11:24
field theory and relativity.
11:27
And uh, that's an issue because uh, they
11:30
are incompatible at ah, the levels that we
11:33
try and look at them now. Um,
11:36
and so uh, to bring a
11:39
quantum theory of gravity into being
11:42
is a big step. So um, what do I
11:45
mean by, by bringing a theory into being?
11:47
Well we know that there are four
11:49
fundamental forces in nature. Uh,
11:52
the strong and weak nuclear forces,
11:55
electromagnetism and gravity. And the
11:58
first three of those have very,
12:01
very well established and well uh,
12:04
understood quantum theories. Um,
12:07
for example, we know that electromagnetism is
12:09
propagated by photons. We're talking about it
12:11
all the time. So the suspicion is that
12:14
gravity uh, is propagated by gravitons. But
12:16
so far there's been no theory of what
12:18
gravitons might be like. So what these
12:20
scientists have done have developed
12:23
a new theory, uh, a new quantum theory of
12:26
gravity. Uh, and I'm actually going to once
12:28
again ah, quote from phys.org, very uh,
12:31
nice account of this, um, uh,
12:34
which is actually, I think it is part of the
12:37
press release from Aalto University in
12:39
Finland. So I'm quoting the university.
12:42
Um, researchers at Aalto University have
12:44
developed a new theory, quantum theory of
12:46
gravity, which describes gravity in a way
12:48
that is compatible with the standard model
12:51
of particle physics, opening the door to an
12:54
improved understanding of how the universe
12:56
began. While the world of
12:59
uh, quant theoretical physics may seem
13:02
remote from applicable tech, the findings are
13:04
remarkable. Modern technology is built on
13:06
such fundamental advances. For example the
13:08
GPS in your smartphone works thanks to
13:10
Einstein's theory of gravity. Uh, and then
13:13
uh, the article goes on to describe
13:16
the theory is published in uh, Research
13:19
Reports on Progress in Physics. Um,
13:22
and this is the quote that I wanted to make.
13:25
This comes from the lead uh, author of the
13:27
paper. Uh, and um,
13:31
um, basically they um,
13:38
they've got lovely Finnish names. That's why
13:40
I'm stumbling. It's Mikko Partanen,
13:43
uh, who's the um, lead author. Uh,
13:46
and the quote is as
13:49
follows. And this kind of puts
13:51
it into perspective, if that's the big
13:54
word. If this turns out to lead to a
13:57
complete quantum field theory of gravity,
14:00
then eventually it will give answers to the
14:02
very difficult problems of understanding
14:05
singularities in black hole and black holes
14:07
and the Big Bang. A theory uh,
14:10
that coherently describes all fundamental
14:13
forces of nature is often called the Theory
14:15
of Everything. Uh, some fundamental
14:18
questions of physics still remain unanswered.
14:20
For example, the present theories do not yet
14:22
explain why there is more matter than
14:24
antimatter in the observable universe. Uh,
14:26
and what they've done is, um, they've
14:28
developed something called a gauge theory.
14:30
And gauge theories are a particular kind of
14:32
theory about the way particles interact with
14:35
each other through a field. Ah, like the
14:37
Higgs field and the Higgs boson. Um,
14:40
so, uh, it's basically a
14:43
very nice a, ah, very nice account. I won't
14:46
read any more because, you know, gauge
14:48
theories got symmetries and things of that
14:50
sort. Um, it's,
14:54
um, a nice account. I recommend people have a
14:57
look@the phys.org uh, paper.
15:00
Uh, uh, sorry, the fizz.org article.
15:03
Casey, I'd send you to that as well to have a
15:05
look. It's a very nice account of, of what's
15:07
happening. You may end up like me thinking I
15:09
really need to know a bit more about gauge
15:11
theory before I can understand this. Uh,
15:14
but, uh, nevertheless, you'll get, um, a good
15:16
idea of what's going on, I think.
15:19
Andrew Dunkley: M. Okay.
15:20
Now, Casey also wanted you to
15:23
explain, if you could, Hubble tension.
15:25
Professor Fred Watson: Yeah, that's an easier one. And, uh, as we've
15:27
spoken about.
15:28
Andrew Dunkley: That's good.
15:29
Professor Fred Watson: As we've spoken about today, uh, that's one
15:31
of the things we might get rid of. Yes,
15:33
Hubble tension is a lot easier than gauge
15:35
theory. Um, and what it amounts to is we've
15:37
got two ways of calculating
15:40
the current expansion of the universe.
15:44
Uh, one is by looking at
15:47
galaxies in our
15:49
vicinity, uh, and looking at the rate at
15:52
which they are speeding away from us.
15:55
They're moving away from us faster as their
15:57
distance increases. This is exactly the
15:59
discovery that hubble made in 1929.
16:02
And, uh, gives us something we call the
16:04
Hubble constant, which is just the rate of
16:07
expansion of the universe. Today we call it,
16:09
ah, h. Naught, um, Hubble
16:12
zero, which is the expansion rate today.
16:16
Now, you can also get an idea of that
16:18
or a measurement of it from the cosmic
16:21
microwave background radiation. And that, to
16:24
recap, is the flash of the Big Bang. We're
16:26
looking back so far in time. We're seeing
16:28
back to a time 380,000 years after the Big
16:30
Bang, when the universe was still opaque and
16:32
glowing brightly. So we see this wall of
16:35
radiation which is now in the microwave
16:37
region of the spectrum, uh, and it's
16:40
peppered with a pattern of
16:43
warmer and cooler places, uh,
16:46
and those, uh, zones of higher
16:49
and lower temperature, and it's only by a
16:51
tiny fraction, uh, they correspond to
16:54
the structure in that fireball. Um,
16:57
in fact, it's caused by sound waves moving
17:00
through it, they're called baryonic acoustic
17:02
oscillations. And we can, by measuring the
17:04
properties of that peppering of warmer and
17:07
cooler regions, we can actually work
17:10
out what the expansion of the universe is
17:13
today. And it turns out that the two
17:15
figures are different, um, by something
17:18
like 4 or 5%.
17:21
And that in modern terms is big
17:24
enough to worry about. It's not just an error
17:27
of measurement. Uh, these have got fairly
17:30
tight limits on the uncertainties, but
17:32
they're different. And that is the Hubble
17:34
tension. Hm.
17:36
Andrew Dunkley: But didn't they recently, recently
17:39
release a paper that suggested that the
17:41
variations are actually within a normal
17:44
range? That this, this,
17:48
these two figures that don't match are, ah,
17:51
close enough?
17:51
Professor Fred Watson: Well, yes.
17:52
Andrew Dunkley: Didn't we talk?
17:53
Professor Fred Watson: We did that. Um, some people have suggested
17:55
that, that it is, that it is actually within
17:57
the experimental uncertainty, but it's
18:00
still seen as attention. They could, they
18:02
should be nearer than what they are.
18:05
Andrew Dunkley: Yeah, okay. Very, very interesting,
18:08
Casey. Thanks for both your questions. And
18:09
no, you haven't spammed us. Two questions
18:12
doesn't equal spam. There's
18:14
probably a definition somewhere online that
18:16
says how many, how many emails become spam.
18:20
You're well, well outside that tolerance. So
18:22
no problem there. Uh, this is Space
18:25
Nuts Q A edition with Andrew Dunkley and
18:28
Professor Fred Watson Watson.
18:34
Space Nuts. Okay, Fred Watson, let's uh, move
18:37
on to our next question. It's an audio
18:39
question so you won't be able to hear it, but
18:42
it comes from Simon.
18:45
Simon: Hi, it's uh, Simon from Vasey in
18:48
New South Wales here. Uh, my question's
18:50
around, uh, the search for Planet Nine,
18:55
uh, other exoplanets. Ah, few have been found
18:58
using radial velocity methods. Is
19:01
that something we could do with the sun?
19:04
Um, I guess Planet nine being so far
19:07
out, probably wouldn't have much influence,
19:10
but we would have so much data on the
19:13
sun as well
19:16
that it might be easy to suss out.
19:19
Anyway, Ah, that's my question.
19:23
Andrew Dunkley: Thank you, Simon. Good to hear from you. Hope
19:26
all is well in Veyce in New South Wales. Uh,
19:29
he's asking, in the search for Planet nine,
19:32
um, we've used the radial velocity method,
19:35
uh, in the past to find other objects. Could,
19:38
uh, we use the sun in the
19:41
search for Planet Nine?
19:42
Professor Fred Watson: Yeah, and it's a great question. Uh, I'm
19:45
very well posed, Simon. Uh, I did actually
19:47
manage to hear that through my own, um,
19:50
recording, which I found and listened back
19:52
to. So I know what Simon asked.
19:56
And what he's saying is
19:59
that we know that when we look for
20:00
exoplanets, planets around, uh, other
20:03
stars. What we look for is the change in
20:05
position of the star itself as it's
20:08
pulled one way and another by the planet
20:10
orbiting around it. And yes,
20:13
indeed, the solar system, uh,
20:16
has such an effect. So Jupiter
20:18
principally is the main planet that's
20:22
pulling the sun's centre one way or the
20:24
other. Uh, but the other planets all
20:27
intervene as well. And so what we
20:30
have is something that's called the solar
20:32
system's barycenter, the centre of mass
20:35
of the solar system and that moves as the
20:38
planets wander around. And,
20:42
um, we've exactly as, um,
20:45
Simon says, we've managed
20:48
to work out the position of the
20:50
barycenter very, very accurately,
20:53
uh, partly because we know where the planets
20:56
are and things of that sort of. Now,
20:59
Simon's question is
21:02
actually exactly the same as a
21:05
question that I found on Stack Exchange
21:07
Online. The question was, wow, can
21:10
the paper narrowing the solar system's
21:13
barycenter to within 100 metres help
21:16
find Planet Nine? Uh,
21:19
so that's basically what Simon asked. And the
21:21
bottom line, there's a long, long set
21:24
of calculations here which I won't go
21:27
through, but the answer is probably
21:29
not. Um, uh, it's because
21:32
the Planet
21:35
nine's influence on the solar system's
21:37
barycenter, it's helped by the fact that
21:40
Planet nine's a long way away. Um,
21:42
um, so it's got sort of leverage, uh, as it
21:45
goes around. Um, um,
21:49
the short answer is
21:52
maybe we could do it, but we wouldn't be
21:55
able to do it without hundreds, if not
21:58
thousands of years of precise data. And
22:01
that's because Planet nine is probably
22:03
orbiting the sun on that kind of timescale.
22:07
And so you don't see any, you know, what
22:09
you'd be looking for is,
22:11
um, changes in the position of the
22:13
barycenter, which are not caused by the known
22:16
planets. But it'll take you
22:19
hundreds or thousands of years to see that
22:21
because of the great distance that Planet
22:24
nine is at. So the answer is probably
22:27
not, but it's a great question and really
22:29
nice thinking. I like Simon's thinking there.
22:32
Andrew Dunkley: Yeah, yeah, it's quite astute. Uh, the
22:35
other factor that comes into play here is
22:38
the new theory that Planet nine doesn't
22:41
exist because there's another planet even
22:43
further out that, uh, has
22:46
only just been sort of put into, um,
22:49
a pager and open for discussion. So we
22:52
only talked about that last week. So the
22:54
search for Planet nine might be a forlorn
22:57
hope anyway, uh, um, because it
22:59
probably, according to the new theory that's
23:02
correct.
23:03
Professor Fred Watson: Yeah. Now, the new theory is based more on
23:05
observations than theory because it's two
23:08
observations separated by something like 30
23:10
years that seem to show something moving very
23:12
slowly in the outer solar system.
23:15
You can bet your life will do more observing
23:17
of that over, uh, uh, coming
23:20
decades. Uh, and maybe that will turn out to
23:23
be what I think is being called Planet eight
23:24
and a half at the moment, because nobody
23:26
really knows whether it's there or not. But
23:28
as you said, if that is real, it rules out
23:31
Planet nine. The two can't exist together.
23:35
Andrew Dunkley: Exactly right. All right, there you go,
23:37
Simon. Um, we'll see where that, uh,
23:40
ends up, but it might take a while.
23:42
Uh, final question comes from Joe
23:45
in Olala in Washington. I hope I pronounced
23:47
that correctly. Is there an upper limit to
23:50
how much Delta V, uh, that can be
23:53
practically generated by gravitational
23:55
assists? Is it possible to develop
23:58
sufficient Delta V for timely interstellar
24:00
travel by winding up a probe in our solar
24:03
system before launching it, uh, to a nearby
24:06
star? Uh, thanks for all that you do. Cheers,
24:09
Joe. Now, Delta V, that is the impulse per
24:11
unit of spacecraft mass, yes?
24:15
Professor Fred Watson: Well, it's basically the change in velocity.
24:19
Um, yes. And impulse is the, uh, that's the
24:21
way people talk about these Delta V's in
24:24
this, in the rocket industry. It's all rocket
24:27
science. What is it anyway, Delta V, uh,
24:30
I think in Joe's context here is
24:33
how much velocity increase you can get
24:35
from a gravity assist, from a, ah,
24:38
slingshot. Uh, and the answer is
24:41
probably no, um, in terms of trying to wind
24:44
up, you know, the speed of things so that
24:46
you, you know, you tell something out of the
24:49
solar system at 10th, uh, the
24:52
speed of light or something like that. Um,
24:55
the reading that I've done on this, and I did
24:58
check it out seems, uh, to suggest,
25:01
excuse me, that um, we are probably
25:05
limited to,
25:08
um, the sorts of velocities that we
25:11
see among the planets of the solar
25:14
system. Now remember, the Earth is orbiting
25:16
the sun at 30 kilometres per second.
25:20
Um, and, um, those velocities
25:23
get less as you get farther away from the
25:25
sun. And that's part of the equation with a
25:27
slingsot, because what you're trying to do is
25:29
steal some momentum from the planet and, and
25:32
give it to the spacecraft. And so there are
25:34
upper limits, uh, on, um, what sort of
25:37
velocity change you can get. It depends on
25:40
how close you go to the planet, depends
25:41
whether the planet's got an atmosphere or
25:43
not. It, uh, depends on the angle that you
25:45
come in. Um, the figure that I've seen
25:47
quoted As a maximum for Jupiter, which is
25:50
the most effective planet for this sort of
25:52
thing, being by far the most massive planet
25:54
in the solar system, is a change of 40
25:56
kilometres per second. Um, now
25:59
that's very good if you're you know, trying
26:02
to get something out to the outer solar
26:04
system, but it's not going to help you
26:06
getting things to other planets.
26:09
Especially when you think, you know, if you
26:11
give uh, a planet, sorry
26:14
a spacecraft, an impulse
26:17
Delta V of 40 kilometres per second by
26:19
interacting with Jupiter, you've got to then
26:23
find another planet that's, that's going to
26:25
give it even more. But the other planets are
26:28
all moving slower than that so uh,
26:31
the change in momentum is a lot harder to
26:33
get. Uh, so I think the answer is it's a
26:36
very nice idea. As Joe suggests, winding up
26:39
by all these gravitational interactions, you
26:41
can only do it within limits. You're not
26:44
going to be able to get like 100,000
26:46
kilometres per second or something like that
26:48
from doing that.
26:49
Andrew Dunkley: Yeah, I suppose you could equate it to using
26:52
a slingshot or a shanghai. There's only so
26:55
much tension you can push, put in, into the,
26:57
the rubber band, let's say to fire the rock.
26:59
And you're not going to be able to fire the
27:01
rock any faster than the maximum
27:04
amount of storage the rubber band can hold.
27:06
And I'm guessing it's the same.
27:09
Professor Fred Watson: Yes, there's a, there's a limited amount of
27:11
energy that you can get from, from a
27:13
slingshot. That's right, yeah. Nice
27:16
idea there.
27:17
Andrew Dunkley: Although it's, it's been very effective as
27:19
you said, for sending things to the outer
27:22
solar system. The, the Voyager probes
27:24
particularly uh, used um,
27:27
the slingshot effect, um, several
27:30
times to get to the outer solar system
27:33
because they didn't have the fuel to do it.
27:36
So they figured out through um,
27:39
an alignment of the planets that they
27:42
could get out there just by using
27:45
the rotation of the planets or um,
27:48
the process uh, that uh, uh,
27:51
Joe's been talking about. So um, yeah it does
27:54
work quite effectively for slower,
27:58
slower speeds that uh, yeah,
28:00
interstellar, probably beyond us in that
28:03
regard.
28:04
Professor Fred Watson: Yeah, probably the lasers and um,
28:07
you know in a solar cell or a light sail
28:09
might be a better bet. But even that beyond
28:12
our technology at the moment.
28:16
Andrew Dunkley: Um, probably won't be for long though. I
28:18
think they'll develop that and get some
28:20
spacecraft heading out towards the Alpha
28:23
Centauri sector and um,
28:25
anyway that remains to be seen. Uh, but that
28:28
would still be a pretty slow mission in the
28:30
scheme of things. But um, yeah, great
28:32
question Joe, thanks for sending it in. And
28:34
if you'd like to send us a question, uh,
28:37
you can do that, uh, through our website,
28:40
spacenutspodcast.com spacenuts
28:42
IO. Click on the AMA link at the top
28:45
and you can send us text and audio questions.
28:48
And don't forget to tell us who you are and
28:50
where you're from. We love to know that sort
28:52
of stuff so that we can send the boys around.
28:54
Or, uh, we could send Huw around because he
28:56
can't be with us today, so he must be
28:58
visiting one of you guys, um, with his, with
29:01
his, um, you know, balaclava on,
29:03
maybe. Yeah.
29:05
Professor Fred Watson: Thank, um, you, Fred Watson, as always, a
29:06
pleasure. Andrew, as always. Good to talk and
29:09
uh, good to hear our listeners questions.
29:11
It's.
29:12
Andrew Dunkley: It is, it is. All right, well catch you again
29:15
real soon. Professor Fred Watson Watson,
29:17
astronomer at large, and from me, Andrew
29:19
Dunkley. Thanks for your company. See you on
29:21
the next episode of Space Nuts. Bye for now.
29:24
Professor Fred Watson: You've been listening to the Space Nuts.
29:26
Andrew Dunkley: Podcast, available at
29:29
Apple Podcasts, Spotify,
29:32
iHeartRadio or your favourite podcast
29:34
player. You can also stream on
29:36
demand@bytes.com. um, this has been another
29:39
quality podcast production from Bytes.
29:42
Professor Fred Watson: Com.