Andrew Dunkley: 15 seconds. Guidance is internal.
10, 9. Ignition
sequence start.
Professor Fred Watson: Space nuts I.
Andrew Dunkley: 4, 3, 2,
1. Space nuts. Astronauts
reported meals Good. Hello once again
and thank you for joining us on this edition
of the Space Nuts podcast.
And my name's Andrew Dudley, your host. And
with Me for episode 193 is
Astronomer in Charge from Professor Fred
Watson. Hello, Fred.
Professor Fred Watson: Hello, Andrew. I did used to be the
Astronomer in charge. That was my.
Andrew Dunkley: I thought I said Astronomer at Large.
Professor Fred Watson: Well, it's quite all right.
Andrew Dunkley: No, it's Freudian slip.
Professor Fred Watson: It's very. And of course, um, uh,
that's why I became the Astronomer at Large.
Because you only had to change four letters
on the office door to make it unknown to you.
Yes, yes.
Andrew Dunkley: Um, the organ. And that sort of harps on
something we talked about a while ago where
your organization has changed names about two
or three times, but didn't change the
lettering. So didn't change the logo.
Professor Fred Watson: Exactly. Same logo since
1991.
Andrew Dunkley: I think that's amazing. Uh, very
good.
Now, um, Fred, have you got enough toilet
paper at your place? Is my big question.
Professor Fred Watson: Well, it's very kind of you to ask. Um,
we haven't yet started tearing pages out the
Astrophysical Journal to use in the bathroom.
Andrew Dunkley: Did you hear about the Northern Territory
News? Uh, the newspaper in Darwin?
They published an edition last week with
several blank pages for people.
This whole thing is just insanity at the
highest level. There's so many people
panicking over nothing. It's.
Professor Fred Watson: You might want to explain the toilet paper
issue, though.
Andrew Dunkley: I think most people are aware, but if you're
not aware, I don't know where you've been.
But, uh, there's been a panic buy up of
toilet paper in Australia and all the
supermarket shelves are empty. Every
supermarket where I live has got no toilet
paper because people have been panic buying
because the prime minister said stock up
because you might have to be isolated for a
couple of weeks because of the coronavirus.
And everyone's freaking out about it. Well,
not everyone. I mean, we don't care. But a
lot of people are freaking out about it. But,
uh, I'm going to bring some astronomy
into this, Fred.
Professor Fred Watson: Oh, good. I wondered where it was going.
Andrew Dunkley: I think this is the 2020 version
of a caveman seeing an eclipse and thinking
the world's going to end. Oh, probably that's
what this is.
Professor Fred Watson: Yeah.
Andrew Dunkley: So I think people need to take a long, hard
look at themselves and give themselves an
uppercut, to use an Australian term, and just
get on with it. This is
ridiculous. Totally ridiculous.
Professor Fred Watson: The good news is that um,
those particular people will, you know,
they'll never need to go and buy another
toilet roll again.
Andrew Dunkley: Not for eternity. They'll
get like, they'll get buried with the stuff.
Professor Fred Watson: Yeah, that's right.
Andrew Dunkley: I'm suggesting that if they're going to, you
know, panic, buy toilet paper, get some baked
beans and some long life milk so that when
you eat it it'll taste a bit better.
M Now let's get down to business.
Today on Space Nuts we're going to uh, look
at something that scientists have discovered
for the first time and that is that space
time is dragging. Not everywhere, but they've
found that it is dragging in one particular
place, which sounds unusual. And what does
dragging actually mean? Uh, we're also going
to look at a couple of clever, uh, students,
um, uh, in terms of a name for the
next Martian rover. This follows on from
Sojourner, which I think is a great name.
Spirit, Opportunity, Curiosity. So what are
they calling the next one? We will tell you.
And a 17 year old intern at
NASA Day 3 on the job has
found a planet six times, uh, or nearly seven
times larger than Earth. I mean,
how lucky is that? Uh, those are some of the
things we'll look at today on Space Nuts with
Fred Watson.
Let's uh, start off Fred, with um, the
fact that space time is dragging. What is it
dragging and why?
Professor Fred Watson: Uh, it's a phenomenon
to do with the theory of general
relativity, or rather the general theory of
relativity, which of course was produced by
Albert Einstein in 1915. Uh, not
long after that, I think about three years
later. Well, uh, let me just step back a
minute. That theory of course says that
as soon as you put matter into space time
and space time's really just space, but with
a fancy name as, uh, soon as you put matter
into it, because of course time's part of it
as well. Uh, as soon as you put matter into
space time it is distorted and that
distortion is what we feel as gravity. Uh,
and that in itself is pretty hard to
get your head around. Space time bends
because matters there. But it was about,
uh, I think three years later
that two Austrian
scientists, uh, by the name of
Josef Lenzer unt Hans Turing,
um, they worked out that
uh, you would get a phenomenon,
um, if you have a
massive object rotating, you get a
phenomenon which is almost a swirling of
the space time around the object. It's called
frame dragging. Um, and
so as the Earth does it, as the Earth
turns, it's not only distorting the
space that's holding us on with the Force
of gravity, but to a much less,
a much lesser degree, it's also
dragging the surrounding space time with
it. Now I know you're
looking baffled, Andrew.
Andrew Dunkley: It's just a lack of sleep because I'm worried
about where I'm going to get a roll of toilet
paper.
Professor Fred Watson: Well, just watch out. Don't drag your space
time with it when you find it.
Um, we usually Anglicize,
uh, uh, Josef and Hans
names to the lens theory
precession or lens theorying effect.
Andrew Dunkley: Okay.
Professor Fred Watson: Um, that's um, how most people speak of
it, even though they wouldn't have called
themselves that. Uh, so, uh,
okay, it has been tested, this
theory. It was um, as I said, I think it
was 1918 when it was uh, when
it was produced. Um, but
uh, the first test of it was
done in the early 2000s.
A spacecraft called Gravity Probe B
was launched into orbit around the Earth
by NASA in collaboration, I think with
Stanford University, um,
which carried on board very, very sensitive
gyroscopes. And by using
those, uh, the
uh, physicists running the experiment could
detect the frame dragging of the Earth
itself. So it's all about subtle
motions in the satellite
and that tells you that yes, you have proved,
because there's nothing else that would give
rise to those subtle motions, you've proved
that frame dragging is true, uh,
but it's only been detected around the Earth.
So now cut to the chase, uh, because
uh, for the first time, uh, it has
now been detected in an astronomical object.
Uh, and this is a really nice story because
it pulls together uh, the
fundamental physics of frame dragging with
some of the big adventures that here
in Australia we are taking part in, uh,
particularly in terms of radio astronomy. The
story goes back 20 years actually, Andrew,
uh, to the Parkes Radio
Observatory, uh, in New South
Wales, the very same state that we are both
in at the moment.
Andrew Dunkley: One hour drive from that telescope.
Professor Fred Watson: Yeah, yeah, that's right. You are indeed.
Exactly. It's just down the road for you. Ah,
very, very well known telescope, uh, the Big
Dish it's usually called.
Andrew Dunkley: And very distracting when you're driving
along the highway because you just want to
look at it.
Professor Fred Watson: You can't stop looking at it. I know
I don't have that problem because usually
when I go down there, that's where I'm going.
So I just watch it getting bigger as you get
nearer to it. Um, 20 years ago,
uh, the Parkes radio telescope
discovered uh, a white
dwarf pulsar binary system.
Um, I'll tell you its name and then we can
get that out of the way. It is, actually.
I've got to magnify the screen so I can read
it.
Now, Fred, you're showing your PSR, uh,
J1141 minus 6545.
There you are. Uh, put that in your diary.
That's good already. As have
I. Uh, it is a white dwarf pulsar, uh, binary
system. What does that mean? It means you've
got a white dwarf star, which is, um, an
object the size of the Earth, but with the
mass of a star in it. Uh, made of electrons
all crushed together. Uh, or the electrons
are the only thing that hold that. Hold the
thing that start the thing from collapsing.
So, um, that is a massive object. Uh,
around it is this pulsar, which is another
massive object, uh, a neutron star. Uh,
the two are in mutual orbits and
the, uh. So the
telescope discovered that
phenomenon, the binary system. So the
pulsar itself is beaming out radiation from
its poles. Pulsars, as you know, because you
and I have spoken about this before, uh,
effectively are extremely accurate clocks.
They basically blip out
radio radiation as they rotate.
That's what the Parkes dish detected.
And, um, the precision with which
they do that is better than atomic clocks.
They are so regular. Um, Just
as one smaller piece of information in this.
The pulsar itself orbits the white
dwarf every 4.8 hours.
So it's, you know, it's a. It's
whizzing round. That's right. Um,
now what has happened over the last 20 years
is that astronomers have been able to use
this timing phenomenon,
the regular timing of the pulsar,
to measure the pulsar's
position in respect to the white
dwarf. Uh, because
essentially time. Accurate time means
accurate distance in terms of, uh, measuring
where the pulsar is. And it's that
measured over 20 years that has
demonstrated that this frame dragging
phenomenon is taking place out there,
uh, at PSR, whatever it was. Uh,
J1141 minus 6545.
Um, so what the
scientists. And there's a group of scientists
from, uh, many different institutions,
including, uh, institutions in Germany, the
Square Kilometer Array Organization. That
is, uh, the headquarters of this great
new telescope that we're planning, the Square
Kilometer Array in Western Australia and in
South Africa. Uh, the headquarters are in
Manchester, uh, or near Manchester at the
Jodrell Bank Radio Observatory. One of the
scientists involved with this work, uh, comes
from that organization. Uh, so that
means, uh, he is relatively closely connected
with Australia because Australia is one of
the host nations. Uh, and
I should just mention that the Parkes dish,
uh, plus another telescope called the
Malonglo Observatory Synthesis Telescope
again here in Australia, uh, which has been
involved with this work. They are both
Pathfinder telescopes for the Square
Kilometer Array. So very important
in this large scale project that
is currently uh, under construction or,
uh, soon will be under construction, um,
that's getting in the plug for ska. But the
research itself, as I said, involves
scientists from Germany, Australia, New
Zealand and actually Denmark too. Um, and
what they've done is they've um, looked at
the way these pulsar signals have changed
over the 20 years and they find
a change in the pulsar's
orbit which amounts to
150 kilometers. Uh, and
we're now talking about something that's
10,000 light years away. Andrews Being
able to measure uh, a change in orbit of
150 kilometers, uh, at that distance is
an astonishing accomplishment. But it turns
out that that change is exactly what you
would expect from frame dragging by
the white dwarf itself. And that's the only
thing that can account for it. So it is the
first time that we've demonstrated this
swirling of space actually, uh, uh,
beyond the Earth's vicinity. And it's an
important, um, you know, a really important
result which is rightly being celebrated all
over the science media, um, astronomers,
detective, Distant space time dragging for
the first time.
Andrew Dunkley: So I guess the point of
this is the massive um, or the
mass of this event rather than, you know, we
talked about how Earth does it, but we're
talking about something on a much larger
scale.
Professor Fred Watson: That's right, yes. Uh, well, the white dwarf
itself, whilst it's probably not much bigger
than the Earth, uh, its mass is much larger.
Yeah, uh, and yeah, you're talking about,
um, you know, you are talking about something
happening on a larger scale. I
confess that um, I am not an
expert on the lens searing effect, uh, but
it is very interesting stuff. Uh, and when
you read up about it, it's quite inspiring
that, you know, all those years ago these
guys worked out that space time is being
dragged around by the Earth.
Andrew Dunkley: And if you like me and you don't want to read
anything about it, there's a fabulous
animation on the
skatelescope.org website where you
can see um, in about 1 minute
and 20 seconds what they've learned over 20
years. It shows you how uh, effect works.
It's very, very good.
Professor Fred Watson: Um, I might give a call out to the, the
person who put that uh, animation together,
Mark Myers, who's at Swinburne University,
uh, because I was in touch with him
yesterday. I'm using one of his, um, graphics
in a newsletter that I prepare and I asked
him if that was all right. He said he, uh,
was delighted to let us use it. And
I absolutely agree with you, Andrew. His
animation, uh, which is on that website, the
skatelescope.org website, is terrific.
Andrew Dunkley: Yes, indeed.
All right, you're listening to the Space
Nuts podcast. Andrew Dunkley here with Fred
Watson. Let's
take a break from the show and hear a word or
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And now back to Space Nuts.
Three, two, one.
Space Nuts. Now, Fred, uh, just,
uh, another shout out to our patrons who
support our podcast with dollars and cents.
We, um, thank you again for doing that. If
you would like to become a patron or just
look into the possibility, uh, you can go to
Our Patreon website, patreon.com
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it's not mandatory. We're not asking you to
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But uh, anybody who contributes does get the
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website. Uh, they also get the commercial
free edition of the podcast,
uh, ahead of time. So, um, something to
consider anyway, um, now, uh, by the
way, Fred, um, my uh, new book,
um, Shameless Plug coming up, uh, is now
available for pre order as an
ebook. So, um, have a look for that
on the Amazon website. So, um,
that's, that's pretty exciting. I very, very
pleased with how it's all turned out. Uh,
someone actually messaged me the other day
and said I've ordered it, better be good.
Professor Fred Watson: Uh, you've got to remind us of the title,
Andrew.
Andrew Dunkley: It's called, uh, the Turanian Enigma. The
Tyranny Enigma. I'm starting. First time I
wrote that down and read it out, my tongue
tripped over it and I thought, no, this is,
this is too hard. But I'm getting used to it
now.
Professor Fred Watson: Very good.
Andrew Dunkley: I've developed a couple of synapses in my
brain that have got my mouth around the
Turanian in. No, no, I tripped over it. But
um, yeah, have a look for it. Uh, the
official release date of the ebook and
the paperback will be April 15th.
And um, a few people have
asked if I could turn it into an audiobook as
well. So I'll look into that. It's just
so time consuming to create an audiobook.
Uh, not so much the reading and recording of,
but the editing. Oh my gosh, that's a
nightmare. Uh, having.
Professor Fred Watson: Well, you did that for, um, almost.
Andrew Dunkley: There's Mud, which was a World
War I story about my grandfather in the Great
War. But that, that started
as an audiobook. So that was. I sort
of flipped the egg on that. I did the
audiobook and then, uh, made the paperback.
But these last two I've done the other way
around or haven't done the other way around.
But um, I'll, I'll look into it. I'll just.
It's got to be feasible. And that,
that sort of becomes the question. But, um,
we'll see how the demand goes. But yeah, have
a look for it. Um, Huw tells me he's going to
put it on our um, bytes.com
spacenuts page. So you might be able to pre
order through there. I haven't checked.
Uh, now let's get down to a couple of things
involving students. Fred. These are, uh,
um, exciting stories. I particularly like
this one, which involves the naming of the
next Mars rover. Now we've uh, heard of
Sojourner and Spirit and Opportunity and
Curiosity, uh some of which
have gone above and beyond the call of duty.
Uh, but um, they aren't the last rovers.
They'll be future rovers. And uh, it looks
like some students have got involved in the
naming of the next one.
Professor Fred Watson: Well, that's right. It was uh, uh,
uh, you know, I think this is what NASA
does normally with its rovers. Uh, it puts
out a um, competition, uh,
to uh, actually to
school students, uh, and
says suggests names for our next
rover. And of course the next rover is
what's been called until now Mars 2020.
Um, it will be launched uh, July or August
this year. I think its landing date
on Mars is the 18th of February next
year. So, um, uh, just under a year
away until now, called Mars
2020. So during the closing
months of last year, NASA put out the
invitation to school
students, I think it was, uh, school students
of all ages from kindy to year 12.
Uh, and uh, invited
them to submit
suggestions
uh, for the um, name, uh, of the
rover. And they received
uh, 28,000
submissions.
Andrew Dunkley: I know, that's amazing.
Professor Fred Watson: It's not bad, is it? That was uh, back in
August, at the end of August last year when
they put the invitation out. Uh,
but fortunately, uh, it wasn't just one
person who had to read all 28,000 because
these were essays, uh, saying why it should
be a particular name. They had 4,700
volunteer judges. They were educators, uh,
professionals in the space field and space
enthusiasts. And they eventually got down
to 155 semi
finalists and then nine finalists. And I
think, I can't remember, but I think you and
I talked about this last year because
there was a list of uh, very elegant. They
were all great names actually for uh, a
rover.
Andrew Dunkley: Robert.
Professor Fred Watson: Uh, and then they put that out for public
voting and in fact it was worldwide and there
were many submissions came from Australia.
They received a total of
770,000 votes
to, to, you know, to chew through, to work
out what uh, the final name should be.
And eventually, uh, they
got one answer and it came.
Andrew Dunkley: Hang on, Drumroll, drumroll.
Professor Fred Watson: Uh, it came from uh,
a youngster by the name of Alex
Mather, uh, who's at a school. I've
forgotten. I think he's in Virginia. I can
check that in a minute. Uh, but he. And
here's the drum roll. He was the person who
suggested the name Perseverance,
which is nice of the new
spacecraft. Yeah, yeah.
Andrew Dunkley: That is a fabulous name for it because it
does actually tell a story
behind all the missions to Mars over the
years and all the work that's gone into it.
They just, you know, uh, all the successes
and the failures and the near misses. It
is Perseverance that's going.
Professor Fred Watson: That's right. I mean this spacecraft as well
could be uh, it could be the one that
discovers life on Mars because
that's what it's, you know, what the aim is.
Um, uh, unlike Curiosity, whose mission was
to discover whether Mars was ever habitable,
which it did within about the first fortnight
of its presence on the planet, um, uh,
Perseverance is looking for evidence of past
or present life, um, with many different
instruments that will, will do that. Uh,
and I suspect perseverance might be
the characteristic that it needs more than
anything else. It will probably be quite a
long mission. Uh, it's unlikely that, you
know, as soon as it drops down it's going to
find evidence of um, Martian
microbes. One would expect that it might have
to move around on the surface a bit, but it
will do that.
Andrew Dunkley: Only slightly pipped, uh, the number
two, which was Do I have to go to Mars?
Professor Fred Watson: Yeah, that's the one.
Andrew Dunkley: Yeah. Um, I'm fascinated by the fact
that uh, they got 28,000 submissions for the
name. It reminds me of an author, a
children's author in Sri Lanka last week who
got 20,000 submissions for the ending of her
latest book. And they came out
and they're going to publish it with
1,250 endings, which is,
which is a, um, Guinness World Record. And I,
I think those sorts of responses really show
where you stand in the world. So when I asked
for a title for my book, I got five.
Professor Fred Watson: Yeah, you did. I think that's pretty good.
More than, more than the number of people who
read my book. Um, um,
the bottom line here is congratulations to
young Alexander Mather. He
is uh, a year, sorry a grade
seven student. Now I, I'm, I'm guessing that
that means he's about 13, uh, or
thereabouts. Um, and
uh, he put in, put together a really
uh, remarkable, um, you know,
remarkable uh, um,
entry. Um, he said some
very, very, very uh,
nice comments about the, the competition. And
his, his uh, his, his um
entry to it, he says, um, this
is actually in the NASA press release. He
says this was a chance to help the agency
that put humans on the moon and we'll soon do
it again. This Mars rover will help pave the
way for human presence there. And I wanted to
Try and help in any way I could. Refusal of
the challenge was not an option.
Lovely. That is great stuff, isn't it?
Andrew Dunkley: Good on him. Okay, uh, so watch out for
perseverance, uh, which should hit
the Martian surface in little under a year.
Still, uh, on students doing great things.
Uh, this is a fabulous story about a 17 year
old who's doing an internship at NASA and
has found a planet on day
three.
Professor Fred Watson: Day three. That's right, it is.
It's great stuff. Um, so, uh, this
is a young man called, uh, Wolf, Cukier,
I hope I'm pronouncing his name correctly.
Uh, he scored a two month
internship with NASA. Uh, so during
last northern summer he was at the Goddard
Space Flight center in Greenbelt in Maryland.
And, um, what he was doing, uh, on
day three, I think he probably started off
doing this. He was trawling through data from
tess. Uh, so TESS is a
NASA spacecraft. It is currently operational,
doing a great job. The name is an acronym
for Transiting Exoplanet Survey Satellite.
So it's actually looking for the dimming
of the light of stars as planets
pass in front of them. And unlike Kepler,
which only looked at a small, uh,
area of the sky to do the same job,
Kepler, now effectively defunct tess, uh,
actually looks at the whole sky. Uh, so
the word survey in its name is very important
because it actually has a chance to look at
the entire sky. So he was looking
through the data. Actually there's a nice
quote again, um, from Wolf. He
says, I was looking through the data for
everything the volunteers had flagged as an
eclipsing binary. That means, uh,
two stars orbiting around their common center
of mass. One passes in front of the other as
seen from the Earth. And so you get what we
call an eclipse. So they're well known stars.
They've been well known for more than a
century. It was looking, uh, through
everything Volunteers had flagged as an
eclipsing binary. A system where two stars
circle around each other and from our view,
eclipse each other every orbit. About
three days into my internship, I saw a signal
from a system called TOI
1338. At first I thought it was a
stellar eclipse, but the timing was
wrong. It turned out to be a planet.
Uh, I noticed a dip or a transit from the TOI
1338 system. And that was the first signal of
the planet. First saw the initial dip and
thought, oh, that looked cool. But then when
I looked at the full data from the telescope
at that start, I and my mentor also
noticed three different dips in the system.
So great stuff and very well
spotted.
Andrew Dunkley: And it's a big one too.
Professor Fred Watson: Yeah, that's right.
Andrew Dunkley: Planets, I suppose.
Professor Fred Watson: Um, it's somewhere between the size of
Neptune and Saturn. Uh,
rather larger than Uranus, about seven
times larger than the Earth. It's in the
constellation of Pictor and it's about 1300
light years away.
Andrew Dunkley: Um, is it a gas giant or a rocky planet?
Professor Fred Watson: Probably. Probably a gas giant. Yeah.
The name, uh, uh, uh,
TOI 1338. TOI
is an acronym for TESS, Object of
Interest. Uh, and, uh, um,
it's one that's floating around a lot these
days with a number attached to it.
So of course, um, because of the convention,
uh, that planet that, uh, Wolf has
discovered is now called TOI1338B
because the B signifies it is the first
discovered planet around the star.
Andrew Dunkley: Excellent. All right.
Professor Fred Watson: Great stuff.
Andrew Dunkley: Yeah, good, good stuff with involving
students, um, doing wonderful things. You're
listening to Space Nuts with Andrew Dunkley
and Professor Fred Watson.
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Now, Fred, uh, we have a couple of questions.
I didn't, uh, preview these because I forgot,
but, uh, we, we are going to tackle a couple
of questions and then we're going to do, um,
a little bit of homework or go back to
something we talked about a couple of weeks
ago just to finish it off, which was the
Roche limit, which, which actually came about
as a result of a question.
But our first question today comes from
Andrew Mitchell. I think Andrew's been in
touch with us before. Dear Fred and Andrew,
all this recent talk about black holes has
been fascinating. And the last installment
got me thinking. According to Einstein's
equations, black holes are supposed to have,
uh, infinite, uh, supposed to be infinitely
small, infinitely dense singularities
at their center. If that's the case, then how
do uh, two actually merge into one black.
Shouldn't they just keep orbiting each other,
getting closer forever? Or is the fact that
black holes do merge actually evidence that
singularities have size? Perhaps a sphere
with a diameter of one Planck length?
Uh, your regular plugs and YouTube Music
channel have been paying off. I just became
subscriber number 993, so it would, you know,
we're a bit overdue getting your question
done, Andrew. Thanks for joining us on
YouTube Music though still loving the show.
Um, please keep up the mind blowing stories.
Thank you, Andrew. Um, black holes, gee, we
don't talk about them very often.
Um, but yeah, it's an interesting
question because we talk about how the, the
black hole itself is quite small when
you compare it to the event horizon or the,
or the, you know, what's going on around it.
Um, but yeah, two
merging black holes, do they actually merge?
And how is it. So.
Professor Fred Watson: It'S a really good question. Um,
it's,
you know, the
whole black hole thing is hard to get your
head around, whether you're a physicist or an
astronomer or somebody fighting
over toilet rolls in the ah, aisle.
Andrew Dunkley: Vesuva involves a black hole too, doesn't it?
Professor Fred Watson: I'm sure it does, yeah. They are very, very
hard, uh, objects to understand. Uh,
and Andrew's question
made, um, how do two black
holes merge into one?
Um, I don't think
there is any need for them
to keep orbiting around each other
if they are of infinitely small
size. I do get his point that if you've got
something that's infinitely small, uh, and
you put something else that's infinitely
small next to it, they're never going to,
they're never going to touch, uh, because
the dimensions are infinitely small. But in
fact, as Andrew says, they do merge.
We have evidence of that, uh, from the
gravitational wave observations that have
been made, um, over the past, uh, two or
three years. Um, and
uh, there is this phenomenon, um,
called the ring down, which is
the sort of aftermath of the merging. Now I
don't know enough about black hole physics to
understand specifically what the mechanism of
the ring down is, but I suspect that is where
the evidence comes that you actually
have now merged black holes. In fact,
we know the evidence is there, um, because
you wind up with a black hole whose mass
is actually usually slightly less than the
sum of the masses of the two black holes that
have merged. And um, the excess has gone into
creating the gravitational waves. It's mass
into energy. Uh, but um,
Andrew goes on to make an interesting point.
He says, or is the
fact that black holes do merge. Actually
evidence that singularities have a size,
perhaps a sphere with a diameter of one
Planck length. Now
introducing the Planck length is a
really, ah, neat way of sidestepping the idea
of an infinitesimally small object,
because the Planck length is defined
as being the smallest
distance. And it does have a
proper physical definition. In fact, it's
actually the distance that light travels in
one unit of Planck time. Uh, so that
raises the question, well, what's Planck
time? Um, let me just
summarize though, and this is coming directly
off Wikipedia. The Planck length can be
defined. Uh, sorry, uh, from. Yeah,
let me read it. The Planck length can be
defined from three fundamental physical
constants. The speed of light in a vacuum,
the Planck constant. That's something, um,
which physicists are very familiar with. And
the gravitational constant. It's the smallest
distance about which current
experimentally corroborated models of
physics can make meaningful statements.
So what it says is. And I'll go on. At such
small distances, the conventional laws of
macrophysics no longer apply, and even
relativistic physics requires special
treatment. The bottom line is that a Planck
length below that, all bets are off. We
really don't understand what is happening to
the physics. And maybe Andrew's point is well
made that, uh, a Planck length
black hole is actually what you
have at the center of, uh,
constituting a black hole system. Um, I need
to talk to my, uh, expert friends about
this because, um, at this level of
technicality, my knowledge is
not specialist, But I do know people
whose knowledge is far better than mine.
And next time I run into them, uh, I'm going
to ask them exactly about these questions and
hopefully feed back to space nuts and to
Andrew and his, um, fellow listeners.
Andrew Dunkley: Okay, so the question remains open, Andrew.
Professor Fred Watson: Yeah.
Andrew Dunkley: I think we'll give you a definite maybe.
Professor Fred Watson: Maybe it's the answer. Yes.
Andrew Dunkley: All right, thanks, Andrew. Thanks for the
question. Let's move on to a question from
Ulf Petersen in Sweden.
Yeah, uh, alf, I've got some news from you
which you may or may not be aware of, but,
uh, a young lady named Julia Engstrom,
A professional golfer from Sweden, Just
won the new south wales women's open,
which we hosted here in dubbo a couple of
weeks ago.
Professor Fred Watson: Great.
Andrew Dunkley: I. Because our course was closed to play for
members, um, uh, we got to go out there and
watch these young ladies go around. It was a
European tour event. Uh, she won
not only her share of the prize money, but a
two year exemption on the European tour.
She's 18 years old. And she
swings it like a champion. I mean, she was
hitting it 260 to 280 meters,
whaling it past me. And she's just a slip of
a kid, but, uh, remarkable player and
someone to watch out for in the future, if
you're a golfer. Julia Engstrom is her name.
So there you go, Ulf. A little bit of. I can
feel his pride swelling now.
Um, now he says hello, uh, Andrew and
Fred, uh, what a fantastic community you've
started. And it's a global one, too. I've
been a faithful listener of your pods now for
a year and enjoy them very much. Never
imagined Thursdays could be that exciting.
I'd usually say something derogatory, but I'm
feeling good today. Um, don't know if
this question might be of interest to the
show. Is there any chance that it's a black
hole question? By the way, Fred, is there any
chance that a black hole might not exist in
its, uh. Inside its event horizon? After all,
black holes are claimed to be singularities
that is infinitesimal in size.
In practical terms, nothing. Right. Uh, if
so, could an event horizon act as a sort
of a delayed postal service, never
informing anyone outside what has
happened? So, like Australia Post, really?
Um, no, they're great. Actually, uh, there's
another piece of news. Dubbo Post Office
here in town. Got Post Office of the Year.
Professor Fred Watson: Oh, uh, fabulous. That's great, Nick.
Andrew Dunkley: About a month ago. So we're doing it right
here, aren't we?
Professor Fred Watson: Uh, you're doing well in Dubbo.
Andrew Dunkley: Extra questions. Would physics allow matter
still to be pulled into the vent event, uh,
into the horizon, even if the black hole was
gone?
Professor Fred Watson: Great, uh, question, Ulf. And, um,
In. In a sense, the. The, um. He's right
about the event horizon acting as a delayed
postal service because,
um, it stops the transfer of information.
We do know that, uh, black holes can
evaporate courtesy of Hawking radiation.
But, um, basically. And that
involves the transfer of information. We know
that, but it's very, very slow. So
the event horizon does shield the black
hole from the outside world, if I can put it
that way. But, um, in terms of
whether the black hole itself exists,
it's kind of the other way around. The only
way the event horizon can exist is if there
is a black hole at the center. Uh,
in other words, this infinitesimally small
singularity, essentially
distorting space time to the extent that
you've got this shield around it, this black
hole. The black hole. Uh, sorry, the black
hole. Event horizon. The event horizon, in
some ways, Is an illusion, Andrew, because,
um, it's just the point of no return. It's
the thing that won't let light out. And it
certainly is black. We've seen that from the
event horizon image, uh, that was released
last year. But, uh, without the black
hole, the event horizon doesn't exist. So,
uh, there has to be this
singularity at the middle with all its
complicated, uh, infinitesimally small
planck length dimensions that we've just been
discussing. Um, yeah, great question though,
and thank you very much. And yes, Sweden
rocks. I was there not very long ago.
Andrew Dunkley: And as monty python says, nothing can come
from nothing. Can't be nothing.
Professor Fred Watson: Yes, yes.
Andrew Dunkley: Um, thanks, alf. Appreciate the question.
One more thing before we finish up, fred, and
this is, um, a little bit of, um, an add on
from a question about the roche limit. A
couple of weeks ago, we were trying to figure
out the roche limit between
the earth and the moon. And as you explained,
the roche limit is the point where gravity,
uh, will destroy one of the
objects involved, um, uh, in
the, uh, situation. So, um, you could
probably explain it better than I just did.
But, um, uh, basically we were trying
to figure out how close the moon could get to
the earth before it was obliterated. Yeah,
life on earth would probably be obliterated
too.
Professor Fred Watson: Well, that's right. It would be a tricky
situation for all of us. But it is. It's much
less than I thought it would be, Andrew.
Um, the roche limit for the moon is
9,492 kilometers.
And I think that's from the center of the
earth. So it's actually 3,004, uh,
114 kilometers above the surface. Imagine
the moon 3,000 kilometers above the surface.
Whoa.
Andrew Dunkley: Wouldn't it look amazing?
Professor Fred Watson: It would look pretty amazing. That's right.
Andrew Dunkley: Just for a few moments until we all died of
fire or die.
Professor Fred Watson: I guess that's right. Yeah.
Andrew Dunkley: But that's okay. We'd have plenty of toilet
paper.
Professor Fred Watson: Ah, ah, we would. We'd be all right. Yes.
Andrew Dunkley: So three, uh, so 9,000.
Professor Fred Watson: Yeah, 9,492 kilometers
from the center of the earth.
Andrew Dunkley: Close as it could get before it was destroyed
by our gravity. And we would go down with the
ship.
Professor Fred Watson: Absolutely. Yeah.
Andrew Dunkley: In a nutshell. All right, now we've got that
sorted out. Uh, thank you, Fred, so much.
It's always a pleasure.
Professor Fred Watson: It's always a pleasure talking to you too,
Andrew. And we'll speak again soon, I hope.
Andrew Dunkley: You will indeed. And thank you for, uh,
listening. Thank you for your contributions.
Keep them coming. We love to hear from you,
whether it's on social media or via our
website where you can send us emails. Uh, we
have a little contact form there, so you can
send us questions and, uh, to the
patrons. There'll be some bonus material
coming up real soon. Uh, other than that,
thank you and we'll see you again next time
on another edition of the Space Nuts
Podcast, Space Notes. You'll be this
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