Latest / Space Nuts: Astronomy Insights & Cosmic Discoveries / Snowball Earth, Dinosaur Asteroids & the Hubble Tension Unravelled

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Snowball Earth, Dinosaur Asteroids & the Hubble Tension Unravelled · Space Nuts: Astronomy Insights & Cosmic Discoveries

0:00
Andrew Dunkley: Space Nuts is taking a bit of a break at the
0:02
moment. Fred and I will be back in the not
0:04
too distant future with fresh episodes. In
0:06
the meantime, enjoy some of the key episodes
0:09
that we have presented over the years.
0:12
Major events in astronomy and space
0:15
science. And we'll see you real soon.
0:18
Space Nuts. Hi there. Thanks for joining us
0:21
on another episode of Space Nuts. Andrew
0:23
Dunkley here and it's good to have your
0:25
company. Coming up on this episode we're
0:28
going to be looking at Snowball Earth.
0:31
There was a time where it was just a frozen
0:34
sphere of nothingness for well, billions
0:37
of years. now they have a new theory about
0:39
that and it's no Irish joke.
0:42
There's a clue in there. the dinosaur
0:45
asteroids origin has been revealed. Yep, the
0:48
thing that started the getting
0:51
rid of them all across the planet. We know
0:53
where it came from. And the so called
0:56
crisis in cosmology might not be a crisis at
0:59
all. We're talking about the Hubble tension.
1:01
We'll talk about all of that on this episode
1:04
of space nuts. 15 seconds.
1:07
Professor Fred Watson: Guidance is internal. 10, 9.
1:10
ignition sequence start. Space nuts. 5,
1:13
4, 3. 2. 1. 2, 3, 4, 5,
1:16
5, 4, 3, 2, 1.
1:18
Andrew Dunkley: Space nuts.
1:19
Professor Fred Watson: Astronauts report it feels good.
1:21
Andrew Dunkley: And to help us unravel all of that,
1:24
decipher it and use his code book
1:27
to figure a few more things out, is Professor
1:29
Fred Watson, astronomer at large. Hello Fred.
1:32
Professor Fred Watson: Hello Andrew. Keep up the good work there.
1:35
It's going very well.
1:36
Andrew Dunkley: It's good to see you.
1:39
I just, I thought I'd sort of start out of
1:41
left field because I spotted a
1:44
story, only today actually,
1:47
which dovetails with something we talked
1:49
about some time ago. And that was the work
1:52
that's being done to perfect
1:55
engine technology to achieve greater
1:58
speeds, for interstellar travel
2:00
in years to come. Or maybe not interstellar,
2:03
but interplanetary perhaps. And we know NASA
2:06
is working on this kind of technology to
2:09
create really
2:12
fast and high performance engines. They're
2:15
working with I think it's General Electric to
2:17
achieve that. they may have been Gesumped.
2:20
Fred, have you heard about this?
2:23
Professor Fred Watson: no.
2:24
Andrew Dunkley: the Chinese, the Chinese claim to have
2:27
developed a new engine
2:30
that can achieve a speed of
2:33
12,000 miles per hour
2:36
or 19,700 kilometers an hour.
2:39
And the aircraft can reach an altitude of 30
2:42
kilometers. Now you compare that to the
2:44
Concorde, it's Mach
2:47
16 versus Mach 2, which
2:50
is an extraordinary claim. Now apparently
2:53
they've released a paper which has been peer
2:55
Reviewed, from what I understand. and it's
2:58
not April 1st, I'm confident of that. So
3:00
they reckon that they've, they've made
3:03
this leap in technology to
3:06
develop a Max 16 engine.
3:09
And just think of this, Fred. You'd be able
3:11
to fly from Sydney to New York
3:14
in 50 minutes.
3:16
Professor Fred Watson: Yes, that's what it was, 50 minutes.
3:20
Andrew Dunkley: that's extraordinary if it's real. And I
3:23
don't see why it wouldn't be, but you never
3:25
know with these things. But apparently,
3:28
according to the paper, the engine operates
3:30
in two modes. There's a continuous rotating
3:32
detonation engine, which is a scary thing in
3:34
itself by the sound of it, which will get it
3:36
to Mach 7. And you know, the air and
3:39
the fuel create a rotating shock wave with
3:41
continuous thrust and then a straight line
3:44
oblique detonation engine which
3:47
fires above mark seven and pushes it all
3:50
the way to Mach 16. it
3:53
sounds amazing. Sounds amazing.
3:56
how far short they are of getting this
3:58
into production, I don't know. But, it
4:01
certainly sounds like it's in development.
4:03
That would be amazing to be able to achieve
4:06
those kinds of speeds. it would revolutionize
4:09
travel around the world.
4:11
Professor Fred Watson: But it's been done already.
4:15
Yeah, the British have been working on this
4:18
for decades now with,
4:22
it's an air breathing, it's a hybrid
4:24
engine that breathes air
4:27
at low altitudes and turns into a rocket
4:30
motor when you get above the Earth's
4:31
atmosphere.
4:32
Andrew Dunkley: Yeah, I think I did hear about that. I didn't
4:34
know it got to those sorts of speeds.
4:36
Professor Fred Watson: Yeah, well, it's capable of entering orbit,
4:38
so it can get up to, you know, 26,000
4:41
kilometers an hour. But it's then acting as a
4:44
rocket motor. So it's The project was called,
4:48
well, Hotol was the style of thing,
4:50
horizontal takeoff and landing. so it
4:53
flies like a plane, takes off like a plane
4:56
with the air burning. Jet engines just
4:58
gradually accelerates, clicks, over
5:02
into being a, rocket
5:04
motor, when the atmosphere gets too rarefied
5:07
and then sends you up to orbit. but as
5:10
I remember right, I think it's called the
5:12
Sabre, the engine. If I remember rightly,
5:14
it's Sabre. But the big problem
5:17
was, keeping the air
5:19
cool. And there was some. The
5:22
main breakthrough was apparently a heat
5:24
exchanger that could bring the temperature of
5:27
the air, down from
5:29
700 degrees Celsius or something, to
5:32
liquid nitrogen temperatures in something
5:34
like a thousandth of a second as it passes
5:36
through the engine. and that was a big
5:39
breakthrough. Now I think we've spoken about
5:41
it before a long, long time ago because there
5:43
hasn't really been much news. It was being
5:45
supported by the British government. I don't
5:47
know whether that support has now dwindled,
5:50
because it would be, you know, the idea about
5:53
this was economics. It was to be able to have
5:55
the same spacecraft that will take you up
5:57
there and bring you back and was completely
5:59
reusable. And to some extent I think,
6:02
Elon Musk, SpaceX and their Falcon 9s have
6:05
kind of cornered the market on that because
6:07
they've now got reusable spacecraft which are
6:10
routinely being used every day, almost.
6:12
So maybe there's no space for it. But yeah,
6:16
extraordinary technology and I'm sure the
6:18
Chinese technology is, is above board what
6:21
you've just been describing.
6:22
Andrew Dunkley: Yeah, it's from the Beijing Power Machinery
6:24
Institute and they've published their paper
6:26
in the Chinese Journal of Propulsion
6:29
Technology. I can, I can see a problem with
6:31
it though. Let's say they do create an
6:33
airliner, that can do that trip in 50 minutes
6:35
from New York to Sydney, for example. You'd
6:38
leave at 7 o' clock in the morning in New
6:40
York. You'd arrive at 11pm 50 minutes later
6:43
in Sydney. So you get up
6:46
and get on the plane then get to Sydney and
6:49
then have to go to bed wide away.
6:50
Professor Fred Watson: Yes, that's right.
6:53
That's the issue. It's always the issue.
6:55
Andrew Dunkley: It would make jet lag all the more worse.
6:58
Professor Fred Watson: But you know, I think I'd put up with that
7:00
rather than have all those 20 hours.
7:03
Andrew Dunkley: Yeah, 20 hour flight. Yeah, I've got one of
7:06
those coming up very soon actually.
7:07
Professor Fred Watson: You do, that's right, yeah, yeah, yeah.
7:10
Andrew Dunkley: yeah, to watch this space story, but I just
7:12
find it fascinating these, these kinds of
7:14
leaps in technology.
7:16
Let's move on. a new theory about
7:18
snowball Earth. Fred, I said there's
7:21
there's no Irish joke attached to this and
7:23
there's a good reason I said that.
7:27
Professor Fred Watson: Which I'm probably going to sidestep
7:28
completely. it's about rocks in Scotland
7:31
and in Australia.
7:33
Andrew Dunkley: I thought it was, I thought they said there
7:35
was some of these rocks in Ireland as well.
7:37
Professor Fred Watson: Yeah, I think, I think there are. I think
7:38
that's right. that' think we've got.
7:40
Andrew Dunkley: That's the loose connection I made with.
7:44
Professor Fred Watson: also includes rocks in Namibia, and North
7:46
America, as well as Scotland,
7:50
you're probably right in Ireland because it's
7:52
the west of Scotland where these, where these
7:54
rocks are. That have recently been analyzed.
7:57
and I mean, it's an interesting story. I've
8:00
often wondered about Snowball Earth. I never
8:02
really looked at. At the details of it. So
8:05
it's a period of about 60
8:08
million years ago. Oh, sorry, 60
8:11
million years long. But it was a long
8:14
time ago. It began 700 million years ago,
8:17
in fact, probably more like 720 million
8:20
years ago and lasted until about
8:22
635 million years ago. And it's called
8:25
the cryogenian. Cryogenian geological
8:27
period. And anything with cryo in the front
8:30
of it means it's frozen solid.
8:34
so I thought, well, how do we know this and
8:37
the way we know it and the
8:40
way we know that, glacial ice covered
8:43
the whole planet is because you
8:46
can see in the geology the
8:49
effects of glaciation,
8:51
everywhere. It's not just, you know,
8:54
I grew up in a country where, 10,000 years
8:57
ago, the whole of the northern part of
8:58
Britain was under ice. And so my. All
9:01
my school lessons were about glacial
9:03
features, in the north of England. And
9:06
so, so you could tell from rocks,
9:09
whether something has been glaciated.
9:12
And that's how we know everywhere there is
9:14
this layer of rock, ah, corresponding to,
9:17
looking back, you know, 6, 6 or 700
9:20
million years where you see the evidence of
9:23
glaciation. and so the interpretation of that
9:26
is that, you had
9:29
an ice age that was the. Put it,
9:32
the grandfather of all ice ages. the whole
9:34
planet was frozen. and so
9:38
the new research concerns, evidence from
9:40
rocks in Scotland. and what's
9:42
remarkable is that, the
9:45
sort of the glacial evidence there
9:49
shows up really clearly, for some
9:51
reason that has been preserved very well,
9:54
there, you know, underneath the sediments
9:56
that were dropped on top of it,
9:59
later on. But, the bottom line
10:02
about.
10:04
Professor Fred Watson: The reason why we got this ice age
10:08
is a question. I'm not sure that in the
10:10
article I sent you, it goes into detail about
10:13
it. but the thinking is that
10:16
we were seeing a period when,
10:19
or before this period, we were seeing a time
10:23
when, volcanic rocks
10:28
were being, eroded. They were being weathered
10:31
very rapidly. And apparently these were
10:33
particularly in Canada. these volcanic rocks,
10:36
I'm looking back now perhaps 720
10:38
million years. they were
10:41
eroded by weathering. And that process
10:44
sucks carbon dioxide out of the atmosphere.
10:48
and so, what you're seeing is
10:51
a situation where the atmospheric
10:54
carbon dioxide is lower
10:56
than normal. And in fact, it is
11:00
probably was probably about half,
11:02
what today's level Is today's level's in
11:05
the region of 400 parts per million of carbon
11:08
dioxide in the atmosphere. And that's enough
11:10
to blanket our planet and keep the
11:12
temperature stable. unless you put more in,
11:14
in which case the temperature goes up, as you
11:16
know. But if, you drop too far down,
11:20
then you get an ice ball. they
11:22
estimate the atmospheric carbon dioxide
11:25
levels, back in
11:28
the cryogenic period or cryogenonian
11:31
period, they estimate they were below 200
11:34
parts per million. And what that does is lets
11:36
the heat just radiate out into the, into
11:39
space and you lose heat. The Earth's, surface
11:42
becomes very cold. and basically, you
11:45
get the snowball Earth, you get an Earth that
11:47
is covered with ice.
11:50
it's the same sort of thing that we think
11:51
happened on Mars. Mars is very low carbon
11:53
dioxide content and that's why we think it
11:55
got cold and dry rather than warm and white
11:58
as it once was.
12:00
Andrew Dunkley: The other, there's a lot of moving parts to
12:02
this story, but one of the things I found
12:04
most interesting was if this
12:08
mega freeze hadn't happened,
12:11
life as we know it may not have developed
12:14
because up until this time it was just
12:16
microbial. Just that was it.
12:19
Professor Fred Watson: That's, that's correct. so, and the thinking,
12:22
yes, it was, it was single celled organisms
12:24
until that time. And they were around for
12:27
you know, 3 billion years or so.
12:30
nothing happened except these single celled
12:32
organisms, principally
12:34
cyanobacteria, they just did their thing and
12:37
got on with life, but didn't evolve in any
12:39
way. but the end this,
12:42
this end of the glacial period
12:45
was such a sort of rapid
12:48
climate change by the standards of the,
12:51
of the time, by geological standards, that
12:54
the thinking is that you'd got almost
12:56
an arms race, to adapt,
13:02
to this new situation where
13:04
the microbes are not permanently in deep
13:06
freeze, you've got a warming climate
13:10
and the evolution of the microbes kicks in
13:12
at a much higher level than it was before.
13:15
And that is where we think that the multi
13:18
celled organism started to be formed. And
13:21
that's what are, the ancestors of all the
13:23
animals that we see today.
13:24
Andrew Dunkley: Yeah, so basically those who survived the
13:27
thaw or adapted to it,
13:29
created life as we know it. Yeah, that's this
13:32
extraordinary, sort
13:35
of factor to come out of it. The other thing
13:37
I, and correct me if I'm wrong, but, these
13:40
rocks we were talking about in Ireland and
13:43
Scotland and Australia and everywhere else,
13:46
the reason that these are so different is I
13:48
believe these were rocks that actually stuck
13:51
out of the ice. Is that
13:53
correct?
13:55
Professor Fred Watson: During that period they may have done,
13:58
or at least been subject to less
14:01
glacial activity. So yes, they may
14:04
have, you know, had only a thin layer of ice
14:07
over them rather than be under kilometers of
14:09
ice. so I think you're right there.
14:12
And just to confirm, you're quite
14:15
right that some of these rocks are in Ireland
14:16
as well. I hadn't spotted that Andrew, in my
14:19
reading of the paper. but yes, so you've got,
14:24
particularly you've got these rocks
14:27
on some of the Scottish islands. These are
14:30
small islands called the Gavelis. and it's
14:33
basically in the west of Scotland.
14:36
it's under the Portaske formation. This is a,
14:39
ah, geological area. Portaske, very well
14:41
known to Scots people because it's the name
14:43
of a well known pipe tune. so let me quote
14:45
from one of the authors of this work. and
14:48
he's actually a Ph.D.
14:51
candidate at the
14:54
university, College London. the layers of
14:57
rocks exposed on the Gyvelichs are globally
15:00
unique. Underneath the rocks laid down during
15:02
the unimaginable cold of the glaciation,
15:05
70 meters of older carbonate rocks formed
15:08
in tropical waters. These layers
15:11
record a tropical marine environment with
15:13
flourishing cyanobacterial life that
15:15
gradually became cooler, marking the end of a
15:18
billion years or so of a temperate climate on
15:21
Earth. most areas of the world are missing
15:23
this remarkable transition because the
15:25
ancient glaciers scraped and eroded
15:28
the way the rocks underneath. But in
15:31
Scotland, by some miracle, the transition can
15:33
be seen. And I think that's underlining what
15:35
you said. They were either sticking up
15:36
through the ice or they weren't particularly
15:38
deeply covered by ice. so it's minerals
15:41
and radiometric dating of the minerals that
15:44
have allowed this discovery to be
15:47
made.
15:48
Andrew Dunkley: Yeah, it's incredible, isn't it? All the
15:51
answers are right there in front of us in the
15:52
dirt sometimes.
15:54
Professor Fred Watson: Simple as that. That's how we,
15:57
we know so much about the history of
16:00
not just our planet but the, you know, the,
16:02
the other planets of the solar system. Just
16:04
learn from looking at the rocks. That's
16:06
right, yeah.
16:07
Andrew Dunkley: Fantastic. if you'd like to read the article
16:10
or chase up that story, it's on the cosmos
16:13
magazine.com website. This is
16:16
Space Nuts Andrew Dunkley here with Professor
16:18
Brad Watson.
16:21
Roger, your labs right here.
16:22
Professor Fred Watson: Also Space Nuts.
16:24
Andrew Dunkley: speaking of dirt, Fred, we've got
16:27
the dirt on the dinosaur asteroid. we
16:30
now know, thanks to a new study where it came
16:33
from. This is fascinating too.
16:36
Professor Fred Watson: It is, that's right. and you know, it's not
16:38
that long ago that people were really still
16:40
speculating about where the remnants of this
16:43
asteroid was. we're now pretty certain
16:45
that it's in the Chicxulub,
16:48
basin in the Gulf of Mexico. That that
16:51
is the site which actually
16:54
was the impact site of this asteroid. So
16:57
what you can do is you can look at the rocks,
17:00
that you find in that region. Once again,
17:03
we're looking down at the dirt, but
17:06
basically look to see whether we know of
17:08
anything like it out there
17:11
in the solar system. and
17:14
the bottom line is
17:17
that yes, we do find that,
17:20
in particular, and this is work being done at
17:23
the University of Cologne in Germany,
17:27
the element ruthenium,
17:30
is basically a chemical
17:33
marker, if I can put it that way, that is
17:36
found in the debris around the
17:39
Chicxulub impactor, and apparently in
17:41
other sediments around the world. Because the
17:44
debris from that explosion spread all around
17:46
the world. It was so, you know,
17:49
ah, such a major
17:52
piece of explosive material.
17:55
It was only explosive because it hit the
17:57
ground at a very high speed, probably 30
18:00
or 40 kilometers per second. but the
18:03
fingerprint of ruthenium has been found in
18:05
that debris and it turns out
18:08
that that coincides with
18:11
rocks in m, the main
18:14
asteroid belt. That's the region between Mars
18:17
and Jupiter, but at the outer edge.
18:21
Outer, edge of the main asteroid belt. Not
18:24
sort of, not the kind of place you'd expect.
18:26
You would think if the, if that rock had come
18:29
from the asteroid belt, you'd think it would
18:31
be near the inner edge. But the chemical
18:34
specifics tell you that it's actually at the
18:36
outer edge. and that is
18:39
really very, very interesting
18:42
deduction. Who would have thought that we
18:44
will be able to pinpoint where that asteroid
18:46
came from, ah, 66 million years after the
18:49
event. and maybe the asteroid,
18:53
I guess.
18:54
Andrew Dunkley: They worked it out on the chemical
18:55
composition elements rather than
18:57
backtracking.
18:59
Professor Fred Watson: Yes, that's right. we don't have enough
19:01
information to backtrack. We don't know what
19:03
angle it came in at or you know, what its
19:06
orbit was before it collided with Earth. So
19:09
it's all about chemistry is this. And in
19:11
particular some quite
19:13
sophisticated, well I suppose you call it
19:15
chemical physics because they're using
19:17
radiation techniques, basically to
19:21
look for these levels of ruthenium,
19:25
basically in the debris from the
19:28
asteroid, crater and
19:31
Surroundings. and,
19:33
basically, looking at,
19:36
how it compares with other,
19:39
asteroid impacts and carbonaceous
19:42
meteorites which also come from that
19:44
region of the solar system.
19:48
Andrew Dunkley: So what might have caused a rock from
19:51
that particular part of the solar system to
19:54
turn its attention to us? Did Saturn get
19:57
upset and chuck a rock at us or something?
20:03
Professor Fred Watson: it's probably, a
20:06
just a gravitational disturbance, you know,
20:09
something that disturbed
20:12
the, orbit of this asteroid. in its
20:15
comfortable zone of the asteroid belt may be
20:18
an interaction with another asteroid. Because
20:20
when objects come together, they needn't
20:23
necessarily collide. But if they can interact
20:26
with each other gravitationally so that one
20:28
of them gets thrown out of its orbit
20:31
and, you know, it's possible that that would
20:33
have been the case.
20:34
Andrew Dunkley: it's kind of like being in a crowd at a
20:36
Chinese supermarket, really. That's.
20:39
Professor Fred Watson: That's what it's like. Yes, yes.
20:41
Andrew Dunkley: You didn't want to go that way, but you ended
20:44
up.
20:45
Professor Fred Watson: You have to. You have to go that way. Yeah.
20:47
Just because everything's so crowded. It's
20:50
a bit like that. The, the thing is
20:53
that that event, whatever tipped it out of
20:56
its comfortable orbit, that might have
20:58
happened a long time before the 66 million
21:01
year date ago,
21:04
that we had for the impact for the extinction
21:07
of the dinosaurs. So it might have been in an
21:10
orbit that intersected the Earth's orbit for
21:12
a long, long time, before the
21:15
crunch finally came when it tried to be in
21:17
the same place at the same time as the Earth.
21:19
so. Yes, so there's details for this story
21:22
that we still have a long way to finding
21:25
out. but it may well have been,
21:28
as I said, it's either a collision with
21:29
another, asteroid. Or maybe
21:32
even something like the gravitational pull
21:35
of gas giants, maybe Jupiter,
21:38
perturbed that object's orbit in such a
21:41
way that it interacted with another asteroid
21:43
and got thrown out of, thrown out of the
21:46
asteroid belt. We probably will never know
21:48
that. It's interesting enough, I think, to
21:50
discover whereabouts it came from.
21:52
Andrew Dunkley: Yes. The other thing that, came out of this
21:54
is that it all but writes off
21:57
that this was a comet impact.
21:59
Professor Fred Watson: Yes.
22:00
Andrew Dunkley: but not absolutely.
22:03
Professor Fred Watson: Yeah, that's right. there's still a
22:05
possibility, but, you know, comets are, a
22:08
different beast from asteroids. They
22:10
contain lots of ice, as well as the rock.
22:13
And that means that the chemistry of
22:17
the residual material from the impact would
22:20
have different properties. so I think,
22:23
it's, you know, you can never say never,
22:26
but the Body of
22:28
opinion seems to be that it was actually an
22:30
asteroid rather than a comet.
22:32
Andrew Dunkley: Yeah. I do have just one more question about
22:35
this story and this is the most important one
22:37
for it. Most important. You mentioned
22:40
the element ruthenium.
22:43
So was the person who discovered that named
22:45
Ruth?
22:48
Professor Fred Watson: that's a good question. I'd have to take that
22:50
one unnoticed. But my guess is that that's
22:52
where the name came from.
22:56
Maybe it was somebody who was ruthless
22:59
and they thought, yeah, I'll call it
23:01
Ruthenian because I'm ruthless. Who knows
23:04
that?
23:04
Andrew Dunkley: Yeah, that's a thought too.
23:07
that story, if you would like to read it, is
23:10
available@spare.com.
23:13
this is Space Nuts. Andrew Dunkley here with
23:15
Professor Fred Watson.
23:22
Professor Fred Watson: Space Nuts.
23:23
Andrew Dunkley: now Fred, to the so called crisis in
23:26
cosmology. We're talking about, the Hubble
23:29
tension. Now we've done this story a few
23:31
times over the years. This is where
23:35
the, basically the expansion
23:37
speed of the universe, depending on how you
23:40
calculate, that number comes up with
23:43
two different answers. And they have never
23:45
been able to figure out why. But
23:48
now they're starting to think, well, there's
23:50
no crisis at all. Everything's right.
23:53
Professor Fred Watson: yes. So,
23:58
let me just explain how this tension, the
24:01
Hubble tension comes about because
24:04
there are two ways of
24:06
measuring, the expansion
24:09
of the universe. one
24:12
uses standard candles and the
24:14
other uses a standard ruler. And
24:17
put it that way. So the standard candle's
24:20
taking that first. if you know how bright
24:22
your candle is, then you can work out how far
24:25
away it is from you. because,
24:28
you know, it's real brightness, it's
24:30
intrinsic brightness. Then you can work out
24:32
what is going on, in terms of.
24:35
Because we know the way light gets fainter,
24:38
we know the rule by which light gets fainter
24:40
as you move to greater and greater distances.
24:42
It's what we call the inverse square law. it
24:45
goes as the square of the distance one over
24:47
the square of the distance. So, standard
24:49
candles are usually, stars
24:52
in galaxies. and in
24:55
fact this is what led us
24:58
detect the expansion of the universe in the
25:01
first place. Because, in the early years of
25:03
the last century, around 1900,
25:06
a group of astronomers, in the United
25:08
States measured the intrinsic brightness of a
25:11
particular kind of variable star, one whose
25:13
brightness varies, but it varies in a
25:16
periodic way. And it turns out that there's a
25:18
relationship between how frequently it varies
25:21
and what the intrinsic brightness is. And you
25:24
usually take it at peak brightness or minimum
25:26
brightness, whichever. It doesn't really
25:28
matter as long as you know what it is. and so
25:30
that's the time honored way of working out
25:33
how far away galaxies are, to look for
25:36
these variable stars and then
25:38
basically look at, at you
25:41
know, how bright they look to us. And from
25:43
that work out the distance, and that lets
25:46
you produce a value for what we call the
25:48
Hubble constant, which is the number
25:51
that basically tells you how fast the
25:54
universe is expanding. the Hubble
25:57
constant is in units of kilometers per second
25:59
per megaparsec. But we don't really need to
26:02
worry about that because at the moment all
26:03
we're interested in is the number. And so
26:06
until now, the best estimates,
26:09
from the standard candles, in other words,
26:11
the Cepheid variables have come,
26:14
out at about 74 kilometers
26:17
per second per megaparsec. But then the
26:20
standard ruler method is looking back at the
26:23
flash of the Big Bang, the cosmic microwave
26:25
background radiation, which we see, as it was
26:28
about 13 billion years ago. And there
26:30
are features in that variation which
26:33
have separations that we know would
26:36
be characteristic of a certain
26:39
particular time. And what we're talking about
26:41
here, when I say features, I mean peaks and
26:43
troughs in the temperature of the Big Bang,
26:46
effectively what you're looking at. and from
26:49
that you can also deduce the Hubble constant,
26:51
the expansion rate as it is today. but
26:54
the answer you get from that is 67.5
26:57
kilometers per second per megaparsec. Yeah.
27:00
Which is round about six and a half
27:03
kilometers per second per megaparsec,
27:05
different from the other one that is now
27:07
we're in such a precise era that now
27:10
has people worried. so what's
27:13
happened? Well, the same team
27:15
who've done a huge amount of this work in the
27:18
past, led by, Dr. Wendy Freeman
27:20
Friedman, one of the big names in this kind
27:23
of science in the United States. Wendy
27:26
and her team have used our
27:29
new toy, the James
27:31
Webb Space Telescope.
27:33
Andrew Dunkley: we always knew it would solve this problem.
27:37
Professor Fred Watson: We knew it would certainly help. It would
27:39
either make it worse or it would solve it.
27:40
And yeah, you're right. To cut to the chase,
27:42
it's probably solved it because it's now
27:44
looking as though the
27:47
method, is more like that. You know,
27:50
the method where you measure the brightness
27:52
of these variable stars is giving an answer
27:54
more like 70km per second per
27:56
megaparsec, which is much closer to that
27:58
67.5 that you get from the cosmic microwave
28:01
background radiation. And it turns out that
28:04
when you think about the error,
28:06
potential error of both of them, then it
28:09
overlaps. So in that regard, you've got
28:12
something that falls within the error bounds
28:13
of both of these methods. And so maybe we are
28:16
seeing the right answer at last.
28:18
Andrew Dunkley: So it basically brings it back to an average.
28:22
Professor Fred Watson: That's right. That's right. Yes.
28:25
You know, when I started my career, Andrew,
28:28
there were two camps. and
28:31
basically they were using similar methods.
28:33
one said that the Hubble, constant was
28:36
50 kilometers per second per megaparsec. The
28:38
other said it was 100 kilometers per second
28:40
per megapar a second. They were both right.
28:43
they thought they were both right. And, it
28:44
turned out that the answer, the real answer
28:47
was the average of them. It was 70 or 75 or
28:49
thereabouts.
28:51
Andrew Dunkley: There you go. pretty simple solution at the
28:53
end of the day, but a lot of hard work went
28:56
into finding it.
28:58
Professor Fred Watson: Yeah, we hope that resolves the Hubble
29:00
tension. It will be great. Hopefully cosmic
29:02
crisis disappeared. Yeah, Yeah.
29:04
Andrew Dunkley: I wouldn't be surprised, though, in months to
29:06
come, somebody comes up with a debunking
29:09
theory.
29:10
Professor Fred Watson: well, there you go.
29:11
Andrew Dunkley: It could happen.
29:12
Professor Fred Watson: It could happen.
29:14
Andrew Dunkley: at this point in time, looks like it might
29:16
have been resolved. This has been frustrating
29:19
for a long time, but, maybe as simple as. Oh,
29:22
hang on a sec. You're both right, and here's
29:24
why. Yeah, yeah, yeah. that.
29:26
Stories on
29:27
scitechdaily.com? without
29:30
notice. Fred, that's come through from one of
29:32
our live viewers, Wayne. Hi, Wayne.
29:35
this harks back to the snowball,
29:38
Earth story we did. Wayne asks, I wonder
29:41
how much bigger the diameter of a frozen
29:43
Earth would be to the current Earth. Do we
29:46
have any idea what that might have been?
29:48
Professor Fred Watson: Yeah, it probably wasn't that much different.
29:51
it, you know, I mean, at the moment,
29:55
a lot of that water's still there, but it's
29:56
wet and, you know, and this
29:59
is. Now it's, it's turned into ice. So,
30:02
it's not going to be. It's certainly not
30:04
going to be, tens of kilometers different.
30:08
it might be a few kilometers different, on
30:11
average. And I'm talking about the average.
30:13
but, but I don't think it would, you know, it
30:15
wouldn't have turned into a gas giant or
30:16
anything like that. That's an interesting
30:18
question, though, because we think it's
30:20
because of frozen water out, in the depths of
30:22
the solar system, adding to the mass of the
30:25
gas giants as they were being formed. We
30:28
think that is one reason why they became so
30:30
big because they had enough mass to hold onto
30:33
a gas envelope. and so it's a
30:35
good question to ask that, ah, what
30:38
difference would the ice make? But this is
30:40
really just a surface layer of ice rather
30:43
than a solid block of ice which may be at the
30:45
core of the gas giants.
30:47
Andrew Dunkley: Indeed. All right, thank you, Wayne. Nice to
30:50
get questions without notice while we're
30:52
going out live during our recording sessions.
30:54
Good to hear from you, Fred. We're just about
30:56
done. Thank you very much.
30:58
Professor Fred Watson: A, ah, pleasure, Andrew. Good to talk and,
31:00
some interesting topics. And there'll be more
31:02
next week.
31:03
Andrew Dunkley: Indeed there will. Thanks, Fred. Professor
31:05
Fred Watson, astronomer at large. Don't
31:07
forget to check us out online
31:09
spacenatspodcast.com spacenats IO
31:12
where you can check out the shop, maybe
31:14
become a supporter of the podcast if you're
31:16
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31:18
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31:29
and thanks, to Huw in the studio, as always,
31:31
and from me, Andrew Dunkley. We will see you
31:34
again soon on the very next episode of
31:36
SpaceNuts. Bye bye.
31:39
You've been listening to the Space Nuts
31:41
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31:53
Professor Fred Watson: Has been another quality podcast production
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