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Europa’s Ocean Secrets, Gravitational Waves & Black Hole Mysteries | Space Nuts: Astronomy... · Space News Today

0:00
Hi, Andrew Dunley here. Fred and I are
0:02
taking a little bit of a break over the
0:04
Christmas New Year period just to catch
0:06
our breath. We'll be back uh sometime
0:09
around mid January. In the meantime,
0:11
we've been digging through the archives
0:13
at some of the most perplexing and
0:16
popular episodes that we've done in
0:18
recent times. So, sit back and enjoy.
0:22
>> 15 seconds. Guidance is internal. 10 9
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ignition sequence start. Space Nuts.
0:29
>> 5 4 3 2
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>> 1 2 3 4 5 2 1
0:34
>> Space Nuts.
0:35
>> Astronauts report. It feels good.
0:38
>> Hi there and thanks for joining us on
0:40
the Space Nuts podcast. My name is
0:42
Andrew Dunley, your host. And joining
0:44
me, as always, Professor Fred Watson,
0:47
astronomer at large from the department
0:49
of da da da da da. It's a pretty long
0:52
title. That's what we'll call it from
0:54
now on. Good day, Fred. You could call
0:56
me the AAL because AAL.
0:58
>> Yeah. When I was when I was astronomer
1:00
in charge, I was AIC.
1:03
The only trouble is AAL actually has
1:05
another significant meaning in
1:07
Australian astronomy because it doesn't
1:09
only stand for astronomer at large. It
1:11
also stands for Astronomy Australia
1:13
Limited. So, uh, just throw that idea
1:16
out. That's a rubbish idea. It'll just
1:17
be a Yeah,
1:18
>> I was once given the title URS.
1:22
But anyway, um,
1:25
some people will understand that.
1:27
>> Yeah. You've got lovely friends, haven't
1:29
you?
1:29
>> I've got a lot of good friends. Yes.
1:31
>> Yeah. Yeah.
1:31
>> Now, today we're going to talk about
1:33
some very exciting things. It looks like
1:35
black holes are still in people's minds.
1:37
So, we're going to be talking about um a
1:40
couple of questions that have come in
1:41
from people about infinite density. Uh,
1:44
density. I keep getting it mixed up with
1:46
destiny. I don't know why. might have
1:48
been a Back to the Future movie that
1:50
confused me on that front. Uh, and
1:52
issues photographing a black hole. Why
1:55
were they issues at all? And another
1:57
question about space travel and near
2:00
light speed travel. Uh, we're also going
2:03
to look at um the cause of a
2:07
gravitational wave that was detected
2:08
recently. This is exciting because they
2:10
think they've pinpointed an actual
2:12
cause.
2:14
And we're going to start off today,
2:15
Fred, by talking about this rather
2:17
exciting mission that's one step closer
2:19
to happening. A mission to Jupiter's ice
2:22
moon Europa. And that's what we'll start
2:25
with this uh well this afternoon, this
2:27
morning, tonight, this evening,
2:28
yesterday,
2:30
whenever
2:31
>> whenever it is. Yeah, it's Yeah. So
2:34
look, a terrific story, very good news
2:36
from uh NASA that they um the powers
2:40
that be within NASA have uh given the
2:42
go-ahad um for a mission called Europa
2:46
Clipper, which is is one of the uh
2:48
missions that's been uh postulated or or
2:52
sorry proposed is a better word for um
2:55
exploring the moons of the outer
2:56
planets. There are a number that are
2:58
kind of on the on the table at the
3:00
moment. Some further advanced than
3:01
others, but Europa Clipper is pretty
3:04
well advanced and as you can tell it's
3:07
target, its main target is Jupiter's
3:09
moon Europa, which is one of these um
3:12
ocean moons, uh ice ocean moons. Uh we
3:16
believe it has a covering of ice, and we
3:18
don't know whether it's thin ice or
3:20
thick ice. So that will be one of the
3:21
things that Europa Clipper would find
3:23
out. um and an ocean underneath it and
3:26
and a rocky core. Uh so Europa Clipper I
3:30
think they are talking about having it
3:33
ready for launch in 2023 which is um you
3:37
know fantastic if if they can do that.
3:40
That's right. Uh but apparently that's
3:43
um that's the the the the baseline
3:46
commitment as it's called supports a
3:48
launch readiness date by 2025. Um, it's
3:51
all being done at the Jet Propulsion
3:53
Laboratory in Pasadena. That's where the
3:56
spacecraft will be built. So, they've
3:58
got the go-ahad. It's um it's got a you
4:02
know, the next step in uh in approval
4:06
from NASA, which I think is a pretty
4:09
solid one. So, I think we you and I in
4:12
2025
4:14
will be talking a lot about Europa
4:16
Clipper maybe. Yeah. and it and what
4:18
will be the basis of the of the mission?
4:20
Are they just going there to have a look
4:22
because
4:23
>> it is a bit like that but it's a very
4:25
good look. Um so it's not going to land
4:28
on Europa. It is a proposal to go into
4:30
orbit around Europe actually to go into
4:32
orbit around Jupiter. Uh and of course
4:35
orbiting Jupiter is always hazardous
4:37
because of the the intense um you know
4:40
the intense uh radiation belts that
4:42
Jupiter has. It's got a magnetic field
4:45
thousands of times bigger than the
4:47
earth's and has these high energy
4:48
radiation belts around it that threaten
4:51
to melt the inards of spacecraft. Uh so
4:54
like uh the Juno mission which is
4:56
currently in orbit around Jupiter, this
4:59
uh Europa Clipper will go into a very uh
5:02
elongated orbit um which will give it 45
5:08
flybys of Europa. Uh, and the altitudes
5:12
will vary from 2,700 kilometers to 25
5:15
kilometers. So, it will really be
5:17
skimming over the surface.
5:18
>> Oh, will.
5:19
>> And it's got this huge science package
5:21
with all the kind of, you know, the
5:23
goubbins that you would expect to find
5:25
on board something like that, including
5:28
a mass spectrometer,
5:30
uh, which basically measures, you know,
5:34
the the weights of atoms, as you might
5:36
guess. Uh it um that is interesting
5:39
because Europa like Saturn's moon
5:42
Enceladus is thought to have although it
5:44
hasn't really been properly confirmed
5:45
but thought to have uh ice uh fountains
5:49
coming out of it. Um which are water
5:52
that's squirting up through its uh
5:54
through its icy shell and instantly
5:56
freezing. It's not frozen. But if you
5:59
fly through it as Cassini did with
6:01
Enceladus, then you can sample what the
6:03
atomic makeup is. And so the mass
6:06
spectrometer will help with that. Uh and
6:09
also um it's got this ground penetrating
6:12
radar and that's going to be crucial in
6:16
characterizing Europa's crust um and
6:19
revealing how much of you know the
6:22
potential water within is oceanic as as
6:25
is expected or whether it is just
6:27
pockets of water as we find in
6:29
Antarctica and indeed around the south
6:31
pole of Mars. Will they be able to tell
6:33
what kind of water it is?
6:36
>> Um uh to to some extent they will. Um it
6:40
it may require a bit of um you know
6:44
inference from other measurements. But
6:46
if you've got samples of ice crystals,
6:49
uh then you can do exactly that. you can
6:52
you know you can uh basically tell tell
6:56
whether it's saline water or fresh water
6:59
because you can see the you can measure
7:01
the salt content of it. So like um
7:04
Saturn's moon and Celadus uh which is
7:07
actually quite rich in minerals and and
7:09
it's the silicut in that that tells you
7:11
that this water was once in contact with
7:13
with rock. Uh, I think the Europa
7:17
Clipper will be able to sample exactly
7:18
those things too, assuming these plumes
7:21
are real because they're then they're
7:23
not well observed. There are there is
7:25
evidence. I've seen images that that
7:27
seem to show these plumes coming from
7:29
Europa. Uh, assuming they're real, when
7:31
they fly through, um, hopefully we will
7:33
be able to tell what kind of water it is
7:35
exactly.
7:36
>> And will they be able to tell how much
7:38
water there is underneath the surface?
7:40
Yes, they will because that will very
7:43
much be revealed by the um the ground
7:46
penetrating radar in exactly the way
7:49
that um one of the spacecraft in orbit
7:51
around Mars. I think it was the I think
7:53
it was might even have been Mars
7:54
Reconnaissance Orbiter, I'm not sure,
7:56
detected this lake of liquid water
7:59
underneath the ice cap of the southern
8:01
ice cap of Mars about a year ago. You
8:03
and I spoke about it. Um, and they can
8:06
tell exactly how much there is there
8:08
because you you can see the boundary
8:10
with this sort of radar. You can see the
8:12
boundary between an ice surface and a
8:14
water surface. And that's crucial to
8:16
doing this. So, this mission won't
8:18
actually be looking for life, but it
8:21
will be looking for uh the potential for
8:25
life to perhaps exist on a on a moon
8:28
like this.
8:30
>> Exactly. So, as the as the blurb um on
8:33
the NASA website says, uh it will help
8:36
scientists investigate the chemical
8:38
makeup of Europa's potentially habitable
8:40
environment while minimizing the need to
8:43
drill through layers of ice. So, that
8:45
what they're going to try and do is as
8:46
much as they can from orbit.
8:49
Um and then you know if there's like if
8:52
they find lipids and amino acids and all
8:54
this sort of thing in the uh in the
8:56
plumes of ice coming coming from Europa
8:59
then clearly the next step will be a
9:01
lander that starts digging holes in the
9:03
ice.
9:04
>> Yes.
9:04
>> I mean you know before you do that the
9:06
first thing you need to know is how
9:08
thick the ice is.
9:09
>> Yes.
9:10
>> If it's a couple of miles thick
9:14
>> actually a couple of miles is better
9:16
than what they're expecting.
9:17
>> Oh is that right? more like 25 or 30
9:20
>> miles or kilometers. That's right.
9:23
Choose your units. Um yes. So yes, a a
9:26
thinish layer of ice would be pretty
9:29
pretty um good to you know to cope with.
9:32
You could probably do that. I mean by
9:34
thin I mean less than a kilometer
9:35
probably.
9:36
>> Yes. But the likelihood is it's it's
9:39
probably more. But I guess we'll we'll
9:40
have to wait and see.
9:42
>> The thing is and um Europa is covered in
9:44
all these cracks that are that are
9:45
brownish in color. Yes,
9:47
>> that's thought to be the effect of
9:49
sunlight on brine on basically on salt
9:52
water. So, you've already got a hint
9:54
there that it's probably a salty ocean
9:57
underneath the surface.
9:58
>> Well, salt's probably not that uncommon
10:00
in the universe really. Um,
10:02
>> that's right. It's not.
10:03
>> It's one of one of the base materials,
10:05
isn't it? Uh, of course, this doesn't
10:08
guarantee they're actually going to go.
10:10
This is just another step forward in the
10:12
approval process. It it does. It does.
10:14
Correct. very longitudinal process and
10:16
they have to get over a lot of hurdles
10:18
before they actually hit the launch
10:19
button. So, uh hopefully they're um
10:22
they're going to get there and u it's
10:24
it's a long trip to
10:26
>> Yes, it is. That's the other thing.
10:27
>> So, they got to time it right. They've
10:29
got to get in the right place at the
10:30
right time.
10:31
>> Exactly. All of the above. That's right.
10:33
So, at least what it you know, at least
10:36
uh it's not a knock back. That's the
10:37
good news.
10:38
>> Yes, indeed. All right. Well, we'll keep
10:40
an eye on this story because I'm sure
10:42
there'll be more to report in the not
10:44
too distant future about a mission to
10:46
Europa. You're listening to Space Nuts
10:49
with Andrew Dunley and Fred Watson.
10:53
Let's take a break from the show to tell
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Or you can tap on the link in the show
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notes.
12:46
>> Roger, you're here also.
12:48
>> Space nuts. Now, Fred, we've uh
12:50
discussed
12:52
uh gravitational waves before and a few
12:55
of those have been detected in recent
12:57
times. Uh the problem with them is what
13:01
is the cause? And now in a recently
13:04
detected gravitational wave, they think
13:07
they've got a candidate. That's that's
13:10
right. This is so this is, you know,
13:11
it's a an ongoing story. Uh what I like
13:15
about this story is it's got a nice
13:16
Australian component because there is um
13:19
there's a a a basically a a
13:22
collaboration here in Australia which is
13:24
called Osgrav uh which is about
13:26
gravitational waves. It's a you know
13:28
kind of fairly predictable name but um
13:30
it includes people from the Australian
13:32
univers national university and I think
13:34
University of Western Australia other
13:36
places which are strong in gravitational
13:38
wave astronomy. So um it's very nice
13:41
that it has this Australian component.
13:43
So what's the story? Well uh the large
13:47
uh sorry the laser interferometer
13:49
gravitational wave observatory otherwise
13:51
known as LIGO um has been operating
13:55
since uh 2015 in its uh sort of current
13:59
state. It's actually technically called
14:01
advanced LIGO because I think it took 15
14:03
years of de of development to get to
14:05
this stage. But that but they have uh
14:08
now not quite regularly but at fairly
14:12
infrequent intervals sorry fairly
14:14
moderately moderate intervals let me put
14:17
it that way they've been detecting
14:18
gravitational wave events and for the
14:21
last couple of years they've had an
14:22
additional string to their bow. Remember
14:24
there are two of these detectors at
14:25
opposite corners of the United States um
14:29
which um you need because uh otherwise
14:33
you've got no idea where these things
14:34
come from or even if they're real. you
14:36
need to see the gravitational wave pass
14:38
one and then the other with the right
14:40
kind of time interval in between. Um but
14:42
they've been joined in the last few
14:44
years by something called uh uh Virgo
14:47
which uh in fact I think it's called
14:49
advanced Virgo like advanced LIGO. Virgo
14:51
is an Italian gravitational wave
14:53
detector. And of course having three
14:55
detectors widely spread over the surface
14:58
of the earth means you can pinpoint
14:59
things much more accurately in in terms
15:01
of the direction in which these
15:03
gravitational waves come in from. tri
15:05
triangulating the signal.
15:07
>> Exactly. That's exactly what it is. Um,
15:10
what's interesting about this one though
15:12
is that the signal seems to be from a
15:16
black hole absorbing a neutron star.
15:21
>> Um, we actually had a false alarm on
15:24
this, which is embarrassing because um,
15:27
my book has just gone to the printer
15:28
saying, "Yes, we've observed a neutron
15:30
star being absorbed by a black hole."
15:33
Um, and that that I think disappeared
15:36
because it turned out to be um
15:38
terrestrial noise. It was sort of, you
15:40
know, so I don't know whether it was a
15:41
train going underneath
15:44
probably
15:44
>> or Yeah, something like that. That's the
15:46
usual story, isn't it? A microwave oven.
15:48
Um that was earlier this year. And and
15:51
that um has now gone away, but it looks
15:54
as though this one might actually be the
15:57
real thing, a black hole and a neutron
15:59
star. Uh we've had two black holes
16:01
merging. Uh that's that's probably been
16:04
the commonest source of gravitational
16:07
waves. There've been several of those.
16:08
We've had a couple of neutron stars
16:10
merging as well. And that actually comes
16:12
with celestial fireworks that you can
16:15
observe with other types of telescope
16:18
like neutrino telescopes, visible light
16:20
telescopes, radio telescopes, x-ray
16:22
telescopes, all of the above. Um and
16:25
that was a big story actually late last
16:27
year if I remember rightly. But um until
16:30
now we haven't had a confirmed um uh
16:34
observation of a neutron star being
16:36
absorbed by a black hole and we still
16:38
don't have it's still a bit speculative
16:41
but from the masses that are inferred by
16:44
the signal and remember what you get is
16:45
this weird gravitational chirp uh it's
16:49
the frequency of a sound wave going
16:53
as the two things come together. Um, and
16:55
it's that that gives you all the details
16:57
of what it is that that are colliding.
16:59
The suspicion is it's two objects, one
17:02
of which is three solar masses and the
17:05
other is five solar masses. I think I'm
17:09
right in saying that. I uh should check
17:11
those numbers. But anyway, uh that is
17:14
the current uh expectation of what is
17:17
colliding. So something three solar
17:20
masses would have to be a neutron star
17:23
because it's too lightweight uh to be a
17:26
black hole. And so that is what's making
17:30
this interesting. What's what's perhaps
17:33
um a bit surprising
17:36
uh it's is that you might expect there
17:39
to be once again uh radiation coming
17:42
from this of you know not just
17:43
gravitational radiation but uh noise in
17:46
the x-ray spectrum or neutron neutrinos
17:50
uh particles things of that sort but it
17:52
but it hasn't been observed and um the
17:57
one of the Australian astronomers uh Um
18:00
I've forgotten her first name. That's
18:02
embarrassing, isn't it? Susan Susan
18:04
Scott. Uh she's at um ANU, Australian
18:07
National University. Uh she says that uh
18:12
I if she well what she says is we've
18:14
looked for light signatures of the
18:16
event, but no one has found any up to
18:17
this point. That indicates that if it is
18:19
a black hole and a neutron star, then
18:22
very likely the neutron star has been
18:24
swallowed whole by the black hole. Uh uh
18:27
he said and she says this could happen
18:30
if the objects were of different masses.
18:32
So it's the smaller object gets sucked
18:35
in more quickly and and is swallowed
18:37
whole. So you know it's not strung out
18:39
into into this um mess of material uh
18:43
that does emit um signals in the
18:46
electromagnetic uh wave bands. Uh if it
18:49
gets sucked in hole maybe you don't get
18:52
any signal at all except for the
18:53
gravitational wave signal.
18:55
extraordinary.
18:55
>> How how sudden would the impact be? I
18:59
mean, you know, neutron stars, we've
19:01
talked about them, and they're pretty
19:03
volatile individuals and and quite
19:06
dense. Um,
19:08
>> quite quite dense is just a slight
19:10
understatement there.
19:12
>> Yes, indeed. Um, so, so
19:16
I imagine it would be quite a cathlymic
19:18
collision.
19:19
>> Yeah, that's right. Um in fact so when
19:22
you've got two black holes um what you
19:25
get at the end of it is a more massive
19:26
black hole
19:28
>> uh and um you're talking there though
19:30
about
19:32
you know infinitely small infinite
19:34
decimally small points merging uh their
19:37
event horizon there are two event
19:39
horizons merge as well and you get
19:41
something called a ring down where the
19:43
event horizon itself vibrates
19:46
um I think with a neutron star you
19:48
wouldn't have the event horizon
19:50
But it will be possible for the the
19:52
neutron star just basically to disappear
19:54
over the black holes event horizon. You
19:55
don't see anything. But neutron stars
19:58
themselves as you and I have talked
19:59
about many times are active in the sense
20:01
that they've got highly intense magnetic
20:03
fields on their surfaces and they beam
20:06
this radiation out which we see as as
20:08
pulsars. So they're not they're not
20:10
particularly quiet things. I mean, this
20:12
thing could be a pulsar whose lighthouse
20:15
beam of radiation is missing the Earth,
20:18
if if I can put it that way, because the
20:20
only reason we see pulsars is when
20:22
you've got a neutron star whose uh beams
20:25
of radiation from their poles actually
20:27
sweeps across the Earth. And that, of
20:29
course, is a particular uh circumstance.
20:31
Maybe this one wasn't like that and it's
20:34
just got chewed up uh and we haven't kn
20:37
we haven't seen it its demise other than
20:39
in the gravitational waves. I think
20:41
there'll be more about this story Andrew
20:43
and um I hope you and I can bring it to
20:46
our uh our space nuts listener or
20:48
listeners
20:50
>> our fraternity.
20:52
>> Yes. Uh well it's it um you know the the
20:55
more we can gather in terms of data uh
20:58
on gravitational waves the the more we
21:01
will learn and who knows what sort of
21:04
problems it could solve down the track.
21:06
So
21:07
>> exactly it's always my comment that you
21:09
never know what you're what you've
21:11
setting in store for the future from all
21:13
this knowledge.
21:14
>> Exactly. Yeah. I mean you just gather
21:16
the knowledge one day it might just go
21:18
you know a penny will drop with someone
21:20
else maybe
21:21
>> a generation down the track. Who knows?
21:23
It's it's all useful.
21:24
>> And even if it's not, it's good to be
21:26
able to gather it and
21:28
>> well, they use it some some way.
21:30
>> It it's um you know, all these things
21:32
are constantly testing Einstein's theory
21:34
of relativity. And that's um very
21:38
important because we know there's
21:39
something wrong with it, but we haven't
21:40
found anything wrong with it yet. Even
21:42
though it's been tested within an inch
21:44
of its life, it still holds up.
21:47
>> Yeah. Fascinating. All right. Stop.
21:49
>> You're listening to the Space Nuts
21:51
podcast with Andrew Dunley and Fred
21:53
Watson.
21:56
>> Okay, we checked all four systems and
21:58
being with the girls.
21:59
>> Space Nuts.
22:00
>> Now, Fred, I do want to shout out once
22:02
again to our patrons. Uh, the number 39
22:06
now. Uh, thank you so much for
22:08
supporting the Space Nuts podcast. We so
22:11
appreciate it. And if you're interested
22:13
in becoming a patron, you can do so at
22:15
patreon.com/spacenuts.
22:17
That's patreon.com/spacenuts.
22:21
And uh thank you to everybody who has
22:24
joined the Spacenuts podcast group. They
22:27
number in their hundreds now, Fred.
22:29
>> We've only had the page going for a bit
22:31
over a week and already we've we've
22:33
tracked the century.
22:35
>> And have over 100 people that are all
22:38
Space Nuts fans who are all now talking
22:40
to each other and uh answering each
22:42
other's questions and uh having a fair
22:45
bit of fun. So, it's I'm so pleased we
22:47
were able to put um those people
22:49
together and uh who knows friends
22:51
friendships may be forged
22:54
>> um or collaborations that might solve
22:56
some of the mysteries of the universe.
22:58
Who knows? Uh that would be a lovely
23:00
legacy. I think uh let's um
23:03
>> and of course if you would like to be a
23:05
uh a member of the Space Nuts podcast
23:07
group um just find it. It's on Facebook
23:10
uh Space Nuts podcast group in your
23:12
search engine. And um yes, just ask to
23:14
join and we will click the approve
23:17
button. Everybody seems to be
23:19
like-minded and enjoying themselves. So
23:21
uh that's what it's all about.
23:23
Now Fred, some questions, if you will.
23:27
Um hello again, fellow nutters. I have a
23:29
question. I'm hoping you can help me um
23:32
understanding an old chestnut. Black
23:35
holes. If a black hole is an infinite
23:37
dense point, why does it have a
23:39
diameter? I don't understand why
23:41
astronomers refer to black holes by
23:43
their size in terms of diameter when
23:45
it's meant to be a point of infinite des
23:47
uh density. Are they mistakenly
23:49
referring to the event horizon? Mario
23:52
from Melbourne. Hello Mario. Thanks for
23:54
the question. And the answer is yes.
23:57
Thank you Mario. Thanks for the
23:58
question. Um Mario then goes on to you
24:02
know everything he says is absolutely
24:04
right that um uh if you've got a a a
24:07
point of infinite density it's got zero
24:10
dimensions so you can't refer to its
24:13
diameter. Uh what you can refer to is
24:15
its mass because the the mass is uh is
24:19
variable. uh but the fact that it has no
24:22
volume means that when you you know when
24:25
you look at the mass per unit volume
24:26
you've got something of infinite density
24:28
which is how density is defined. So
24:31
Mario is absolutely right. Uh what does
24:33
vary though with the mass is the event
24:36
horizon the diameter of the event
24:37
horizon which you and I have spoken
24:39
about before. Um it's uh uh it's a a
24:44
quantity that I I suppose is important
24:47
because if we are observing an um a
24:51
black hole as we did with the event
24:53
horizon telescope then that's what you
24:54
see. Uh so a big one's going to be
24:56
easier to observe than a smaller one and
24:58
that's why a super massive black hole uh
25:00
in the center of a galaxy called M87 was
25:02
chosen for the the first target for that
25:04
event horizon telescope. But no Mario
25:07
you're quite right. Um it is that uh
25:09
astronomers when if they talk about the
25:11
diameter of a black hole and that
25:13
probably includes me as well uh are
25:15
actually really referring to the event
25:17
horizon because that's the that's the
25:18
parameter. And I love the way Mario
25:21
signs off by saying thanks in advance to
25:23
Dave and Fred although he does say aka
25:26
Andrew.
25:28
>> Yes, that one's going to stick for a
25:29
while. Sorry to say. Thank you Mario.
25:35
Moving on. Uh hi Andrew and Fred. It's
25:37
Andrew from Newcastle with another
25:39
question if I may. Just watched a doco
25:41
on the quest to capture the first
25:43
photograph of a black hole. Uh rather
25:45
accurately the shadow of a black hole as
25:48
Fred so eloquently explained and I
25:50
didn't understand one thing amongst
25:53
others of course with the multiple
25:54
observatories around the world and the
25:56
use of atomic clocks to synchronize the
25:58
data acquisition. Why were they uh on
26:01
tender hooks uh regarding the weather at
26:04
all the sites with bad weather at just
26:07
one putting the whole venture in peril?
26:09
I understand from the show and other
26:11
sources that they were collecting radio
26:13
wavelength data and I thought that this
26:15
was unaffected by the weather and
26:17
atmospheric conditions. I thought that
26:19
was the intrinsic beauty of radio
26:22
astronomy day and night rain and shine.
26:24
Hope you can enlighten me. Wait for it
26:27
but over the radio. Dear, oh dear. H
26:30
Andrew Broadhost. Thank you, Andrew.
26:32
>> That's a great question, Andrew. Leave
26:34
the jokes to me, man.
26:37
>> Yeah. Well, I always leave them to you.
26:39
So,
26:41
>> um if they're good.
26:43
>> Oh gosh. When was the last Oh, never
26:46
mind.
26:48
Uh Andrew's on the money there is, you
26:49
know, I thought radio waves were
26:51
unaffected by the weather. And the
26:53
answer is that radio waves come in
26:54
different flavors. Uh and so what you
26:58
might call low frequency radio waves um
27:01
which are still relatively you know
27:03
they're way outside the medium wave band
27:05
of radio and things of that sort but low
27:08
frequency in radio astronomy um I guess
27:10
goes up to a couple of gigahertz or
27:12
something like that. Um those are
27:15
largely unaffected by weather. That's
27:18
absolutely right. So that's why it can
27:19
be pouring down at parks at the radio
27:22
dish there and the astronomers are still
27:23
happily observing through that. But the
27:25
event horizon telescope used higher
27:27
frequencies. Uh in fact one of the
27:31
telescopes that was incorporated into it
27:33
was ALMA the Atakama large millimeter
27:35
array which has featured very uh very
27:38
widely on space notes. That is a high
27:40
frequency
27:42
uh radio array. In fact they have
27:46
receivers that go up to uh more than 900
27:49
gigahertz. So that's like, you know,
27:51
nearly a thousand times higher
27:53
frequencies than what we've just been
27:54
talking about. And at those sorts of
27:56
frequencies, uh, the weather plays a
27:59
very important role because water vapor
28:02
actually dramatically absorbs the
28:05
microwave signals. And that's what
28:08
experienced that watching satellite
28:09
television. If there is a storm and it
28:12
rains heavily, the wavelengths of the
28:14
raindrops can absorb the signals from
28:17
the satellite and you get nothing.
28:19
That's interesting. I've never tried to
28:21
watch satellite television, so that's
28:24
good thing to know.
28:25
>> Um,
28:26
>> it's one of the pitfalls.
28:28
>> Yes. Yes. In fact, I seldom watch
28:29
television at all. So, that's probably
28:31
why. Um, but but the bottom line is um,
28:35
you know, it's why facilities like ALMA
28:38
and some of the other radio telescopes
28:40
that were used uh to to to be become the
28:44
event horizon telescope, it's why
28:45
they're all at high altitudes. Alma is
28:48
at almost 5,000 meters above sea level.
28:51
Um that's you know 15 16,000 feet and at
28:55
that height there is very little water
28:57
vapor in the atmosphere. Uh but you can
29:00
still get weather and that's why they
29:01
were indeed on tent hooks about the
29:03
weather because they don't want any of
29:05
these if you lose one of those arrays
29:09
and I think there were eight of them
29:10
that came together all around one
29:12
hemisphere of the earth uh to to to make
29:14
up the event horizon telescope. if you
29:17
lose one of them, you lose a significant
29:19
amount of your ability to reconstruct
29:21
the image that they're seeing. Uh, and
29:23
so that was why they were worried that
29:25
the the weather on just one of them
29:26
might be uh moist uh or damper than they
29:30
can cope with and that would have
29:31
screwed up the whole thing. But as it
29:33
happened, it wasn't. It didn't happen
29:35
and it was great.
29:36
>> They got global good weather.
29:38
>> They did global good weather at these
29:40
high altitude sites. That's right.
29:41
>> Did the job. All right, there you are,
29:42
Andrew. Uh, thank you for your question.
29:45
And we've got one more we'll squeeze in
29:47
from John Spoo. I hope I pronounced that
29:50
correctly. John, thanks for your
29:52
question. Hi, I have a question that's
29:53
been bugging me for some time and I need
29:55
an expert to help me out. I think we
29:58
should stop there, Fred.
30:00
>> There's nobody here, is there? Who's
30:01
that? Hang on, I'll go and see if I can
30:03
find somebody.
30:04
>> Maybe the cat could probably answer this
30:05
one. Now, um, imagine a spaceship
30:09
traveling close to the speed of light.
30:11
Disregarding that we don't have that
30:12
sort of propulsion just yet, would the
30:15
increase in its relativistic mass at
30:18
some point turn the spaceship into a
30:20
black hole? And if so, would that spell
30:24
the end of the ship and its crew? Or
30:26
would they be able to slow down to
30:28
reverse the process? What a great
30:30
question.
30:30
>> It is a fantastic question. Do you want
30:32
to have a go at it?
30:33
>> Uh, the answer is no.
30:35
>> It is. You got right. Yeah, you were
30:37
right on the money there. See, see,
30:39
there is an expert. It's called Andrew
30:40
Dunley or Dave
30:42
>> 50/50 chance.
30:45
>> Um, it's a great question and it it the
30:49
answer is a little bit prosaic I think
30:52
and that is that in the in the rest
30:56
frame of the spacecraft
30:58
you know so if you're on the spacecraft
31:00
and you're going at almost the speed of
31:01
light your mass doesn't change. It's
31:05
only in the rest frame of a a stationary
31:09
observer. And by that I mean somebody
31:10
watching you go past. Somebody watches
31:12
you hurl past and your mass gets very
31:15
much higher to the observer.
31:19
>> But to the the inhabitants of the
31:22
spacecraft or the spacecraft itself,
31:24
your mass doesn't change.
31:25
>> It's you're still normal.
31:27
>> Still normal. Yeah. So and the same
31:29
story is true with time dilation. You
31:31
know you're you know that when you go
31:33
nearer the speed of light, your clocks
31:36
tick slower. Uh that's a scene by a
31:39
stationary observer. Uh and so it's the
31:41
same sort of thing. If you're on the
31:43
spacecraft, your clock is ticking at the
31:44
same rate as it ever was. But to a
31:46
stationary observer, your clocks tick
31:48
slower.
31:48
>> And this has been proven with atomic
31:50
clocks, hasn't it?
31:51
>> It has. And indeed with mass as well.
31:53
You can do this. You can see this sort
31:55
of phenomenon with um uh with uh cosmic
31:59
rays which travel very close to the
32:01
speed of light. You can see their mass
32:02
change. So, um, that's from the point of
32:06
view of somebody who's, you know, not
32:08
moving at the same speed. If you're
32:10
moving at the same speed, you don't see
32:11
any change at all.
32:13
>> That's pretty boring.
32:14
>> I mean, the more the more we discuss
32:16
black holes and the number of questions
32:18
we get about them, people are really
32:21
quite captivated by the strangeness of
32:25
them. I suppose they they throw up all
32:27
these things that seem so alien to what
32:29
we consider normal. Uh, and that's
32:32
because we've only experienced uh what's
32:35
happening on our planet any given time.
32:37
So to to try and comprehend um enough
32:40
gravity to warp time to slow things down
32:44
to the observer and and increase mass
32:46
just it's really whack.
32:50
Sad on the brain. That's true. And you
32:52
know, but uh look, John's question there
32:55
is is a great question because it's it's
32:57
not intuitively obvious what is
33:00
happening uh in a situation like
33:03
something traveling close to the speed
33:04
of light and and so he's right to ask
33:07
would that mass actually turn it into a
33:09
black hole? Uh but the answer is no
33:11
because of the reasons that I've
33:12
outlined. But it's great great thinking.
33:14
>> It is indeed. Thank you, John. Thanks
33:16
for the question. Do appreciate it. Keep
33:18
your questions coming in. We're trying
33:19
to um run them down, but they it's it's
33:22
it's an ever growing mass really.
33:25
>> It's all right. Look, as you said
33:27
earlier, Andrew, um all the space
33:29
nutters are going to get together and
33:30
sort them out for themselves and we'll
33:32
be
33:34
>> encourage actually if uh if people want
33:35
to ask questions of the group and and
33:39
discuss it, they Yeah, by all means. Um
33:41
that that's part of the reason we set up
33:43
the Space Nuts podcast group. So, um,
33:45
it's a good opportunity to not only meet
33:48
like-minded people who enjoy these these
33:50
topics, but also to maybe come up with
33:52
your own ideas on on what might be. And,
33:54
you know, I'll keep an eye on it, and if
33:56
something pops in there that we think is
33:57
worthy of further discussion, we will
34:00
certainly investigate that. Uh, thanks
34:03
to everyone who um who who sent in their
34:05
questions uh and contributed and joined
34:08
the Space Nuts podcast group and Patreon
34:10
and everything else. We really
34:11
appreciate it. Uh but most of all we
34:14
appreciate you Fred. Thank you so much.
34:16
>> It's a pleasure. Thank you for having me
34:18
as always.
34:19
>> And we will catch you next week.
34:21
Professor Fred Watson, uh astronomer at
34:24
large. And from me, Andrew Dunley, thank
34:26
you again and we'll catch you next time
34:28
on another edition of Space Nuts.
34:30
>> Space Nuts.
34:31
>> You've been listening to the Space Nuts
34:34
podcast
34:36
>> available at Apple Podcasts, Spotify,
34:39
iHeart Radio, or your favorite podcast
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