Capturing The Cosmos
DR. TANYA HILL: Good
afternoon, everyone.
My name is Tanya Hill.
and I'm the astronomer for
the Melbourne Planetarium.
And here at the
Melbourne Planetarium
today, it's a
pretty exciting day
as we're launching a brand
new planetarium show.
It's called "Capturing
the Cosmos."
And we've created
it in partnership
with the scientific
organization called CAASTRO.
And I'm fortunate to
have with me today
two members from CAASTRO,
Ben McKinley and Jack Line.
MR. JACK LINE: Hello.
DR. TANYA HILL: They're
both researchers
at the University of Melbourne.
And so what we'd
like to do today
is talk a little
bit about the show,
some of the Australian science
that's happening right now,
the telescopes that
these guys are using
to explore some of the
really big mysteries
and the big questions
about the Universe.
So guys, do you want to
just say a little bit
about your research?
Maybe Ben, what's the
thing that excites you?
DR. BEN MCKINLEY: Sure.
I work using data from
a radio telescope that's
located in Western Australia
called the Murchison Widefield
Array.
And it's a new and
innovative radio telescope
that uses a lot of
different antennas spread
out right across the desert.
And it's out there to be
far away from any humans
so that we don't
get any stray radio
signals coming
into our telescope
and messing up our images.
And I use this data to
try and peer back right
to the very beginning
of the Universe
before there was any stars
and galaxies to look at.
And so I'm just looking
at hydrogen, which
sounds really super boring.
But there's a big
gap in our knowledge.
And we don't know much
about this hydrogen
and what it was doing.
So it can actually
teach us a lot
about how the Universe
formed and is evolving.
So it's pretty interesting.
DR. TANYA HILL: Yeah,
no, it really is.
Astronomers get really excited.
DR. BEN MCKINLEY: We get
excited about hydrogen gas.
DR. TANYA HILL: --this
idea about hydrogen
and about looking-- because
when we look up in space,
we're looking back
in time, aren't we?
DR. BEN MCKINLEY: That's right.
DR. TANYA HILL: It's
taken light so long
to reach us that we can see
the history of the Universe.
And I know when I was talking
to a lot of astronomers,
they were all
like, we want to go
right back to see how
the Universe first
began, see the first stars
and galaxies that lit up,
and really excited about this.
And one way we used in
the planetarium show
to describe this
excitement is imagine
if you had a photo album, a
photo journal of your life,
and you went back from
what you did today,
and what you did the day
before, but you get to a point
where there's this missing
gap where you have no idea.
Maybe you've lost
all your baby photos,
or you don't know what happened
in that period of your life.
And that's kind of what
these astronomers are doing,
isn't it?
We can map so much of
the life of the Universe
except for this one little part.
And we'd love to know what
was happening right there.
So Jack, what research
are you doing?
MR. JACK LINE: So just like
Ben, I work with the MWA.
And like Ben says, we're
looking at that period of time
where there weren't
actually any stars,
and they've just switched on.
So that's about 13 billion years
ago, and maybe even further.
So just like Tanya was
saying, it's a long time ago.
We're not really sure what
happened in that time.
And you can't really
understand the entire Universe
until you've studied
the whole Universe.
So that's kind of our idea.
DR. TANYA HILL: Yeah, because
CAASTRO, the organization
these astronomers work for, it's
the ARC Center of Excellence
for All-sky Astrophysics.
So it's about looking in as
much of the entire southern sky
as possible to kind of
piece things together.
It's a little bit--
I kind of describe it
like we've been looking at the
individual pieces of a jigsaw
puzzle.
We've looked at this galaxy that
sits in this part of the sky
or this amazing star
cluster over here.
And what these guys
are doing is actually
putting the whole jigsaw
puzzle together and seeing
how it all fits and all works.
So that sounds pretty right?
Excellent, well, if you've got
questions, send them through.
We'd love to hear from you.
So we might start with
one of the first questions
from Keysborough College.
And Jack, I'll hand
it over to you.
What advances are being made
with the wide field arrays,
like the MWA in Western
Australia that you work with?
What advances are being
made with telescopes
like that compared to previous
generations of telescopes?
MR. JACK LINE:
Cool, so wide field
means you can see lots of
the sky at the same time.
Previously, we'd have
telescopes that could only
see small patches of sky.
So as a kind of a
scale view, the Moon
is half a degree
across in the sky.
We call that half a degree.
The MWA, our telescope, can see
around 60 widths of the moon.
So if you think how big
the Moon is in the sky,
we can see all of
that at the same time.
Now to do that, you need
special kinds of hardware.
So I think an image has just
popped up on your screen,
maybe, or is about to pop
up, which is on, awesome.
So this is actually
what the MWA is made of.
It's kind of lots of little
metal spiders, really.
And we work in the radio regime,
so Triple J, things like that.
They're at the same
kind of frequencies
that we're actually
trying to study
this old fog of the Universe.
But due to the way
these things are built,
they can see such a large
patch of sky at the same time.
It means that we
can look at the sky
and map the entire
southern hemisphere
really quite quickly.
We can basically
make up a picture
within days of the entire sky.
So the MWA has been surveying
the sky for over a year
now, and along with the
same area of the sky
as the SkyMapper project.
But the advances
that we're making
is that we can see lots and
lots of things at the same time.
If you want to try to understand
how certain galaxies behave,
you need to check that they
all behave in the same way,
or kind of compare and contrast
different types of galaxies.
You can't do that
unless you have hundreds
upon thousands, sometimes
up to millions, of examples.
So the real big advances in
these wide field telescopes
is that you can make
them super quick.
That's it.
DR. TANYA HILL:
Yeah, that's amazing.
And Ben, you were
saying about the kinds
of data that is pouring
down from the sky
all the time that these
telescopes are gathering.
Do you want to-- yeah,
you know the numbers.
DR. BEN MCKINLEY: Yeah, sure.
So an optical telescope
actually uses a camera.
And you stick it on the
end of the telescope.
And then you can download an
image straight to your laptop.
Or you could even look
through it and see an image.
Our telescope is
a bit different.
So it's got all these
different elements.
And for each pair
of antennas-- so one
of those tiles that
you see in front of you
with the 16 spiders on
it, that's one tile.
So each pair of those
generates a number, each
depending on how often we
sample it, but like many times
a second.
And so each time you get one of
those numbers from each pair--
and across a whole range
of frequencies as well.
So you multiply
the number of pairs
of antennas with how
many times you sample it
per second with how many
frequency channels you want it
in.
You end up with
this big number that
ends up being like a terabyte
of data for, what is it,
a two minute observation?
MR. JACK LINE: No, every hour.
DR. BEN MCKINLEY: For an hour.
So every hour, we're generating
an external hard drive
full of data.
So we have to pump that
down a big, fast internet
link to a supercomputer
and store it.
And so all we basically
have from our telescope
is a whole bunch of ones and
zeros, just ones and zeros
sitting there on the computer
until an astronomer logs
on and does some fancy magic
with some software to actually
turn it into an image.
Because what we're trying
to do by spreading out
these antennas across the
desert is to sort of mimic
having one huge telescope.
So what we have is
one huge telescope
that has a lot of holes in it.
In fact, most of it is hole.
There's not that much telescope.
And so we have to do
some fancy mathematics
to actually turn those
ones and zeros into images.
And so that creates
even more data.
Because you have the raw data.
And then you have
the calibrated data.
And then you have images.
And so we need big computers.
DR. TANYA HILL:
Yeah, so it really
relies on computer power.
I often talk about
radio telescopes
that in some ways,
as you said, there's
a lot of holes in the data.
It's kind of like you're
looking through a picket fence,
isn't it?
And so what you want to see is
what's beyond the picket fence.
But you only see that between
the little holes in the fences.
But that's enough to then
piece it all together
through the computers.
And we get a really clear
image of what radio waves are
coming down from the sky.
Actually talking about
radio waves, in fact,
we've got another picture of
the same telescope, the MWA.
But what we've done is
we've changed the sky
from being the normal sky to
the radio sky, the signals
that this telescope can detect.
If anyone has been out
and away from the city
and has seen the Milky Way, that
beautiful band of stars that
crosses our sky,
well, that bright line
there in the middle
of the image, that's
how radio telescopes
see the Milky Way.
Rather than it being nice and
broad-- we're not seeing stars.
We're just seeing a very
thin band of hot gas,
of the gas that
makes up our galaxy.
And you might be
able to just notice
there's little dots
that look like stars.
Jack, do you want to explain
what-- they're not really
stars at all, are they?
MR. JACK LINE: Yeah,
they're actually
sort of big collections.
So every single dot there
is actually a galaxy.
So a galaxy can have
anywhere between 100
to a trillion stars, or 100
billion to a trillion stars.
Each of those is a
radio loud galaxy.
So most likely it has a
black hole in the center.
DR. TANYA HILL: You've
got to love black holes.
MR. JACK LINE: Oh, black holes,
they're the interesting one.
But black holes, they're hungry.
If there's gas around them, they
sort of slowly eat this gas.
As this gas heats,
it gets energetic.
And combine that with
some magnetic field lines,
you can produce lots
and lots of radio waves.
And they're super bright.
So every single dot that
you see in that image
is a collection of between 100
billion and a trillion stars.
So it kind of looks
like our galaxy,
which just has stars in it.
But they are radio galaxies.
And something else
which is pretty cool,
which is in the
galactic center there,
you can almost see sort of
bubbles within that center.
That's what we call
a supernova remnant.
Now, when really, really
big stars get super old,
they get to the
end of their life,
they actually end in
this violent explosion,
which we call a supernova,
which you've probably heard of,
which also SkyMapper, which
we'll talk about later,
is good at finding those.
But these supernovae
remnants, once you've
had this big supernova,
you have this big envelope
of sort of material
that gets thrown out,
and it's kind of getting
bigger and bigger and bigger
as we go through the
age of the galaxy.
Each one of those bubbles
is a supernova remnant.
They're easier to
see along the plane,
so that's why we can
see so many there.
But you can make out 10
to 20 just with your eye.
And that's an ancient
blown up star.
They look pretty in optical.
But they also look very
nice in radio as well.
DR. TANYA HILL: Yes,
they're amazing,
these rings from the debris
of a star that's exploded.
So the supernovae and
the Milky Way, that's
part of our own Milky Way
galaxy, which, as Jack said,
a few hundred billion of stars.
And then our galaxy
is just one galaxy
amongst the millions of
galaxies that are out there.
And yeah, we can
peek those galaxies
like those little dots
of light in the radio
waves, which is pretty amazing.
So the MWA looks at the sky
in a completely different way
to how our eyes do.
But another telescope that
CAASTRO astronomers work with
and that we feature in
our planetarium show
is a telescope called SkyMapper.
And it's more of
a usual telescope,
what people are used to
seeing when you think of one.
But it's doing something quite
different as well, isn't it?
It's still in this
wide field space that's
looking at all the sky at once.
Ben, do you want to
explain a little bit
about what makes SkyMapper a
different kind of telescope
to other ones that we have?
DR. BEN MCKINLEY:
Sure, so astronomers
have for a long time focused
on tiny little patches of sky,
like if you can imagine
holding a grain of rice
up at arm's length
and seeing just
the bit of sky that's
covered by that grain of rice
and zooming right in on that.
And you can see
thousands of galaxies
and get amazing
detail about that.
DR. TANYA HILL: So that's
the Hubble Space Telescope.
We've seen amazing images from
the Hubble Space Telescope.
Often it's only a small--
DR. BEN MCKINLEY:
Yeah, and that's
the teeny piece of the sky.
So we know a lot about
that little bit of the sky.
But we know very little
about the rest of the sky.
Is that the same as
the rest of the sky?
Does the other parts of the
sky look wildly different?
And what if we want to compare
those galaxies to something
like the MWA where we've looked
at this huge patch of sky?
We only have optical
telescope data
from that little tiny patch.
So what SkyMapper
is doing is it's
programmed in to automatically
search the sky every night
and map the entire sky.
And it can do this
relatively quickly.
Because its field of
view is much larger
than that grain of rice.
So it covers 30 square degrees.
DR. TANYA HILL: So Jack
compared the MWA to the Moon.
DR. BEN MCKINLEY: To the Moon?
I think it's about--
how many Moons is that?
MR. JACK LINE: I think
it's 10 Moons across.
DR. BEN MCKINLEY:
Yeah, 10 Moons across.
DR. TANYA HILL: Whereas
the Hubble can't even
picture the Moon, can it?
It's seeing like a tiny
little crater on the Moon.
MR. JACK LINE: It's like
a quarter of the Moon.
DR. TANYA HILL:
Yeah, yeah right.
DR. BEN MCKINLEY:
Yeah, and if you
point the Hubble at
the moon, it would
burn everything and destroy it.
DR. TANYA HILL:
That's true as well.
You don't want to do that.
DR. BEN MCKINLEY: So that's what
SkyMapper is really good for.
It can visit a large
patch in the sky.
It looks at it for
a minute or so.
And then it moves onto
the next patch of sky,
and the next one,
next one, next one.
And what's also
cool about it is it
revisits the same
areas again and again
in order to fill up
those patches of sky.
And that allows
us also to compare
the images to see how they've
actually changed in time.
And that's one of the
ways that we can find
these things called supernovae.
DR. TANYA HILL:
Yeah, so SkyMapper,
because that's the
important thing,
that it takes a view of the
night sky, and then another one
again over and over.
And we're used to
not much changing.
We don't see much change
in the sky with our eyes.
But this telescope can
pick up these changes too.
Now, I've just hooked into--
there's some great questions
that are coming through.
And one of them was, how
many stars can we find now,
and what's the number?
And I don't know.
I think all of us would
have trouble actually
giving you the number of stars.
It's kind of like counting
up the number of grains
of sand on a beach.
And I know I remember
reading something
on the internet about
how they compared it.
And it's pretty close.
One of the things
about astronomy,
we're dealing with
such big numbers.
Getting things that
precise is pretty hard.
Would you agree, Ben?
DR. BEN MCKINLEY: I guess I
would answer by, it depends.
If you look up at
the sky, I think
you can only see like a few
thousand with the naked eye.
And then if you look
at that little rice
grain in the sky with
the Hubble telescope,
you can see thousands
of galaxies, which
each have billions of stars.
So you're multiplying
thousands by billions
just for that rice grain.
And then you've
got the entire sky.
So to the human brain, there's
an infinite number of stars.
DR. TANYA HILL: Yeah, it's
pretty hard for us to describe.
And someone's also asked, please
tell me the earliest red shift
interval at which galaxy
and quasars are currently
known to exist.
So this is the idea,
we're looking back.
It's about 13 billion
years ago, isn't it?
But they've asked for red shift.
Do you guys know the--
MR. JACK LINE: So the
current record of actually
observed is something
like 11 I think,
or somewhere around
red shift 11.
We think the first
galaxies and stars
formed somewhere around 16, 18.
I can't quite remember.
We're not exactly sure.
And that's exactly
why the MWA works.
The thing about astronomy,
until, well, very recently,
is to do astronomy,
you need light.
That's kind of what
it's actually based on.
You need to look and see.
Before the galaxies
were there, there
was nothing producing light.
That's why it's so
difficult for us to probe,
and why we named that
time the dark ages.
It sounds a bit sinister,
and it kind of is.
Because there was
literally nothing producing
light at that time.
So we can't really see
it until they switch on.
And there's lots
and lots of stuff
in the way with
this hydrogen gas.
DR. TANYA HILL:
Actually we've got
a picture of the fog
of the early Universe.
So the idea is that it
was mostly hydrogen gas.
And it was light
couldn't escape.
Light couldn't get through
and travel all the way
to get to us until the first
stars and galaxies started
forming holes.
It's kind of like they
were burning away.
MR. JACK LINE: It's
a Swiss cheese phase,
I like to call it.
DR. TANYA HILL:
Yeah, there you go.
And that's something.
The MWA is one of
the only-- very few--
telescopes in the world where--
MR. JACK LINE: At
the moment, yeah.
DR. TANYA HILL: Yeah,
the only telescope
that can actually potentially
try and find the Swiss cheese
effect.
It's actually looking
for the holes in the fog
to see how these first stars and
galaxies lit up the Universe.
MR. JACK LINE: And
that's another reason
we need wide field telescopes.
Because these
patches-- obviously,
this is almost a whole
sky representation.
You need to be able to see
large patches of the sky
to be able to pick up
these kind of holes.
And they only still
exist on the imprint
of the sky because of red
shift and the expansion
of the Universe.
So we're lucky that
there's a snapshot in time,
and we can probe back.
But we need really
wide field instruments
that also work at
the right red shifts.
So red shit and
radio frequencies
kind of go hand in hand.
But yeah, I think 11 is
the best we've seen so far.
DR. TANYA HILL: Yeah, no,
that's pretty amazing.
DR. BEN MCKINLEY:
And I guess, yeah,
relating the MWA
to that question
as well, the beauty
of it is the highest
red shift ones have
been found by looking
at individual galaxies.
We're not looking
for the galaxies.
We just infer that
the galaxies are there
because of these bubbles.
So by looking at that
large patch of sky,
we can sort of figure out
and use some detective work
to figure out when the
first galaxies formed,
even though we
can't even see them.
DR. TANYA HILL:
Yeah, it's amazing.
And this is a great
question from Penleigh
and Essendon Grammar School.
They're asking about how
much will the data collected
from the Square
Kilometer Array, which
is the next generation
of radio telescopes,
differ from the Murchison
Widefield Array?
Do you want to talk
about that, Jack?
MR. JACK LINE: Fundamentally,
it is actually the same.
So an interferometer just means
a collection of receivers.
And you combine their
signals in a specific way.
The big difference is it's going
to have lots and lots more,
basically.
In the Murchison
Widefield Array,
we have about 128
different receivers.
In the Square
Kilometer Array, there
may be anywhere up to a million.
And the amount of data
that it produces just
scales astronomically,
unfortunately.
One of the figures that got
thrown around a while ago
was the data rate transfer
inside the Square Kilometer
Array is going to be more than
the global internet traffic.
DR. TANYA HILL: So
global, international,
everything that's happening.
MR. JACK LINE: As in
the entire internet,
the amount of data that's
flying around there--
DR. TANYA HILL: --will
just be in this telescope.
MR. JACK LINE: --will be
in this one telescope.
Then it's an astronomer's
job to work out
how to condense that into a way
of actually getting information
from it.
So we're in the regime when you
can't store your data anymore.
You have to process it.
So you have to kind of
do whatever math you
want to do to it on the fly.
At the moment, we're
actually relying
on a thing called Moore's law.
So there's a law
of computing that
says as time goes on,
computers get better.
That's basically
it in a nutshell.
At the moment, the computers
that we need for the SKA
don't actually exist.
We're just assuming that
they'll get good, good enough
to actually run this telescope.
It's a good law.
It's a fair assumption.
DR. BEN MCKINLEY:
That's you're job.
You're going to be designing
and building those computers.
MR. JACK LINE:
Yeah, it's amazing.
DR. TANYA HILL: Keep
technology advancing--
it's pretty incredible.
So we've had another question
from Penleigh and Essendon
Grammar.
And they want to know, why
is it important to know about
what's happening
in the Universe,
and what do you
think the impact is?
Ben, why is it that
we should learn this?
DR. BEN MCKINLEY: Well, I
think probably the best answer
that I can think of
for that is you just
don't know what applications
are going to come out of it.
And for example, what
we've discovered,
fairly recently, is we
thought that gravity would
be slowing down the Universe.
So we knew it was expanding
and getting bigger and bigger.
But because there's
matter in it,
and things attract each other,
it should be slowing down.
DR. TANYA HILL: Because gravity
should be pulling everything
back together.
DR. BEN MCKINLEY: Yeah,
so they had this idea,
we'll use supernovae,
and we'll measure how
the Universe is slowing down.
And they measured it.
And they said, hang on,
it's getting faster.
It's getting bigger faster.
Why's that?
Basically they
discovered anti-gravity.
So there is a force,
a repulsive force.
And so if someone can figure
out how to actually make
hoverboards out of that, it's
going to benefit everybody
in the entire Universe.
DR. TANYA HILL: Absolutely.
So what you're talking
about, there is dark energy.
Astronomers have given
it this name mostly--
I think it's dark because
we don't know what it is.
And actually it links us back
to SkyMapper, the telescope
that we were talking
about before.
Because SkyMapper can pick
up changes in the sky.
It can pick up supernovae,
these stars that explode.
And then it's by
looking at-- supernovae
are fantastic in
terms of something
called standard candles.
Jack, do you want to explain
what a standard candle is
and why supernovae are so--
MR. JACK LINE: Yeah,
so one of the issues
that we face as astronomers
is the sky kind of almost
looks like 2-D to us, right?
It just looks like a
bunch of stars painted on
to almost like a ceiling.
But in reality, that's not true.
We live in a three dimensional
universe that we can probe.
So we have to try and work our
how far away things actually
are.
And it's not as straightforward
as you might think.
And we have lots of
little tools in our bag.
DR. TANYA HILL: Because all
we can do is see things,
collect the light, isn't it?
So we're trying to measure
distance just by the light.
MR. JACK LINE: Exactly, exactly.
So if you have something that
you know exactly how bright it
is, that's really useful.
So imagine you
have a light bulb.
You put it right in front of
your face, looks really bright.
Put it really far away,
it looks pretty dim.
You know that it's the
same brightness, though.
It's just further away.
So if you know exactly how
bright your light bulb is,
and you put it on the
other side of the room,
you can do a
calculation comparing
how bright it looks to how
bright you actually know it is.
And then you know exactly
how far away it is.
There's a certain
type of supernovae
which we know exactly
how bright it is.
So if you can watch
them going off,
and you can associate
them with a galaxy,
you know exactly how
far away that galaxy is.
The duality of the awesome
thing about red shift
is it means we can see
things in the past.
But it also changes the
frequency that we see them at.
So we need to know how far
away something is to know
exactly what's happening in it.
So the standard
rule is essential.
And things like
SkyMapper are able to see
them all the way across the
sky, which is very, very useful.
DR. TANYA HILL: Yeah, so it
can find these supernovae.
They're called type
Ia supernovae, not
the most original of names.
But the cool thing
about these supernovae
is that it's not
just a star that
reaches the end of
its life and explodes.
It's a star that is actually
orbiting around another one,
and it's funneling gas
off that second star
until it just gets too
heavy, can't cope anymore,
and pretty much implodes.
It's an implosion that
causes the supernovae.
So we know how bright that
supernova event should be.
And as you said,
that's our standard.
The dimmer it appears, then we
can get to measure distance.
And that's where things are much
further away than we thought.
So the Universe, rather
than just getting
this kick at the Big Bang and
expanding, for some reason dark
energy switched on and
is pushing everything
even further apart.
Now, I've got a
great question here.
I'm not sure what
school it's from.
But what is the
Universe expanding into?
Ben, do you want to
try and help out?
It's a bit of a
misnomer about it.
How do we talk about
the Universe expanding?
DR. BEN MCKINLEY: Yeah,
it's not something
that our human brain can
really picture or comprehend.
Because you're
talking about sort
of an extra dimension of space
that you're not aware of.
So it's not the Universe
expanding into anything.
There wasn't an empty universe
with a little seed that got
bigger and bigger and bigger.
It's the Universe itself.
It's the space that
we're moving through
is getting bigger, which
is kind of mind blowing.
You don't notice things so much.
Because there's
other forces that
are holding things
together here on Earth,
like this table and me.
But the space around
us is getting bigger.
But it's not an
effect you can really
notice until you look at
things that are really, really
far away.
So the amount of stretching
is proportional to how far
two things are apart.
So that's why we need to
look at these really, really
bright supernovae that
are really far away
to see how the universe
is actually expanding.
So it's space itself.
So it's not expanding
into anything.
There is no middle.
Everything around us
is just getting bigger.
DR. TANYA HILL: Yeah, and
so it's one of these things.
The Big Bang was the
start of the Universe.
And in some ways, that big bang
is all around us, isn't it?
Even right now, because
it happened everywhere
in the Universe.
And so it happened right
where we are as well.
It's one of these
crazy, crazy ideas.
And so the Universe
is expanding.
Dark energy tells
us that expansion
is getting faster and faster.
Jack, what do you
think's going to happen
in billions and billions
of years into the future?
MR. JACK LINE: Well, if it
goes the way that it is,
everything's just kind of
going to get a bit cold.
And it's all going to turn
into a rather boring universe,
unfortunately.
We're going to kind
of have a big freeze.
And the temperature
will just slowly, slowly
go towards absolutely zero.
Lots of interesting stuff
will happen in between.
There'll still be lots
of stars blowing up
and radio galaxies switching
on and turning off.
But yet at the
moment, we think it's
going to be pretty boring
in the end with everything.
DR. TANYA HILL:
Yeah, so it'll even
get to the point--
so at the moment,
on sort of small
scales, which even
I'm talking about
the size of a galaxy,
gravity is able to hold
the galaxy together.
And so it's not expanding
against dark energies yet.
It's kind of the
distance between galaxies
that's expanding.
But eventually we
could get to a point
where dark energy can overcome
the forces of a galaxy holding
together.
We would lose the stars in
the night sky, I'm guessing.
Would it get to that point, that
the stars would be moved away,
and some would be all
alone, and eventually--
MR. JACK LINE: Well, we might
run out of hydrogen eventually.
So there wouldn't be any
fuel left to make stars.
DR. TANYA HILL: Nothing
more to make stars?
DR. BEN MCKINLEY: So
gravity is strong enough
to hold our little
island galaxy together.
And I think the local galaxies
that are orbiting around,
they're pretty much bound.
So I think the
stars will probably
stay until they all
burn out and disappear.
But the MWA image that we
saw would completely change.
So that will fade away.
And it will be blank.
And future MWA astronomers will
just be staring at nothing.
It'll make the
surveys a lot easier.
[INTERPOSING VOICES]
DR. BEN MCKINLEY: So yeah,
get into astronomy now.
Because it's all going away.
DR. TANYA HILL: And
again, of course,
astronomers talk about
time in billions of years.
So it's, well, who knows
how humanity and things may
have evolved by then.
So let's see, what other
questions do we have there?
So one of them sounds
quite interesting.
If there's so much
missing mass, why
is the expansion of the
Universe still accelerating?
MR. JACK LINE: Do
you want to tell us?
Yeah, we're not entirely sure.
The reason we call
it dark energy
is because we can't see it.
And we don't really know
where it comes from.
And similar with dark matter is
the fact that we can't see it.
They're kind of holes
in our current theory.
It can be slightly
embarrassing as an astronomer
to admit that, what is it,
about 70% of the Universe,
of the energy budget of the
Universe, is dark energy.
DR. TANYA HILL:
Which we don't know.
MR. JACK LINE: We
just shrug, right?
You can't know
everything straight away.
We have to put in
effort and work out.
But that is one of
the big questions.
I don't know.
No one does, I think.
DR. TANYA HILL: Yeah, and I
suppose actually going back
to that earlier
question about impact
as well-- what was it,
almost 100 years ago
when quantum mechanics
was discovered.
And so this is talking
about the physics
of how things work on
a really tiny scale,
on the scale of an atom.
And well, there's all these
strange probability effects.
And at the time, the
scientists were going, look,
it's interesting.
It tells us something
about our universe.
But whether it's ever useful--
and now every device we use,
all our computers, iPads,
all the rest, they're built,
they're made, to be so miniature
because of quantum mechanics.
So I often like to think at
the moment, on the other scale,
in terms of the big
scale of the Universe,
we've got this dark energy, 70%
of the Universe we don't know.
Who knows what advances
that may lead to?
MR. JACK LINE:
Yeah, that is cool.
DR. TANYA HILL: It's a
really interesting field.
OK, we've got a couple
of questions coming in
on my favorite topic,
the topic of black holes.
Jack, do you want
to explain what
would happen if you got a bit
too close to a black hole?
MR. JACK LINE:
Spaghettification.
 
So gravity is basically set
up by how much stuff you have.
And in a black
hole, you have a lot
of stuff in a very,
very tiny point.
So you get this really
intense gravitational field.
And gravity, you feel
the force of gravity
more the closer you are.
But it also has this
very strange effect
of changing the way time works.
So at the edge of
a black hole, you
have crazy things
happening where
gravity is getting stronger
the closer you get to it.
And also time is
kind of slowing down.
So essentially you can kind of
almost see your feet going off.
Because they're kind of
getting pulled off anyway
and sheered off.
But the time the light takes
to get to your head changes
as well.
So you get spaghettification,
pretty much.
DR. TANYA HILL: So stretched
out into a long, thin piece.
Because even over-- gravity
changes on Earth, too.
Gravity at the
surface of the Earth
is much stronger
than when you go
into space 100 kilometers up.
But over the distance
of how tall we are,
the gravity change
is pretty minimal.
But you get close
to a black hole,
and the gravity change between
your feet and your head
is enormous.
And that's what
stretches you out.
And I love the whole
time dilation idea,
the fact that-- and it is.
Time for you actually--
you feel time the same way.
But it all slows down.
So you can look
back and actually
kind of see the Universe
speeding up in a way.
Because the Universe is ticking
away at its normal rate.
So time out there seems to
move faster than for you.
MR. JACK LINE: And it isn't
actually fully theoretical.
We have proven these things.
If you put a clock
on the surface
of the Earth-- a very,
very accurate clock,
not just your stopwatch.
But if you put a very
accurate clock on the surface
and stick it up on a space
station, just the fact
that you're orbiting
around the Earth
means that the passage
of time changes slightly
for the clock on the ship.
And we've done this.
We've seen that there
is a slight difference
in the time measured up in
space versus on the Earth.
So whenever we throw it around,
it sounds like science fiction.
But it's just science.
It's actually true.
DR. TANYA HILL: And it's
another thing we use every day.
If you've ever used
GPS to get somewhere,
you're talking to a
satellite which relies
on a very, very accurate clock.
And its clock is
ticking-- can I remember?
It's in the order
of microseconds
different to our
clocks here on Earth.
But that would translate to--
if you didn't take that time
difference into
account, then you
would start to be like a meter
away from where you wanted
to go, and then a kilometer,
and then it would just
get worse all the time.
So all the time we're using it.
DR. BEN MCKINLEY:
They calculated
what that time difference is.
And then they set the
clocks differently on Earth.
And then they send them up so
they're exactly synchronized.
MR. JACK LINE: Pretty cool.
DR. TANYA HILL: Yeah, so we're
using relativity and time
dilation all the time,
which is amazing.
DR. BEN MCKINLEY: Yeah,
and Einstein never
got to see this,
unfortunately-- poor fellow.
DR. TANYA HILL:
So someone wanted
to ask a really good-- I think
it was from Gympie High School,
about if black holes are sucking
material in, like we say,
turning things to
spaghetti, and they're
black-- that's why they
were named that way--
how do we see them?
We just put up a radio image of
all those little dots and said,
you're looking at
sort of black holes,
at galaxies powered
by black holes.
Why is it that we
can see a black hole?
DR. BEN MCKINLEY:
OK, well there's
an exciting new way
that we can actually
see black holes directly, which
we can talk about in a sec.
DR. TANYA HILL: Let's
do the normal way first.
DR. BEN MCKINLEY: But
the normal way first
is we're not actually
seeing the black hole.
So we're seeing the stuff
around the black hole.
So what happens,
because the gravity is
so strong around a black
hole, and as Jack said,
they're really hungry,
things are going into them.
But it's actually really hard
to fall into a black hole.
So if things start going
really, really fast
and getting torn apart--
and it's really violent.
And you end up with
these big jets of energy
that are shooting out either
side of the black hole.
And so that's the bit
we're actually seeing.
What we're seeing from
the radio telescope
is the radiation caused by
little particles, electrons,
that are whizzing
around very, very
close to the speed of light
through a magnetic field.
So they're whizzing and
whizzing and whizzing around
out of these jets.
And that's what we see.
DR. TANYA HILL: Yeah, so the
radio telescope sees the jets.
They're kind of spewing out.
I don't know if anyone
does it these days.
But there's-- is it Vita
Brits or something or other?
They're always the biscuits.
And if you squish them together,
all the butter and the Vegemite
can come out through the holes.
It's kind of like that,
the jets of the Milky Way.
So that's what a
radio telescope sees.
And x-ray telescopes,
they see all the material
as it's spiraling down and
going around and around slowly
trickling into the black hole.
It heats up due
to friction, just
like rubbing your
hands together.
And it gets so hot,
millions of degrees,
that the gas actually
shines at x-ray wavelengths.
And so that's another
way we see them.
But very recently,
just last month, we
found a new way of
looking for black holes
and what happens when two
black holes actually circle
around each other and
eventually collide
from a single black hole.
I'm talking about
the amazing discovery
of gravitational waves.
So Jack, you're nodding there.
Do you want to explain what
is it that's happening?
MR. JACK LINE: Yeah, so this
is some extreme physics.
When you have two
black holes, and they
start kind of doing this one
Swan Lake dance that they're
about to go, they're
about to collide and die,
they kind of do like
a whirlpool going down
the plughole thing where they
orbit each other very, very
quickly.
Now because they
have so much mass,
and we said the mass
affects gravity,
there's huge
gravitational effects.
Well it turns out the
gravitational effects actually
change the shape of space.
So you actually
stretch it and warp it.
Because you're going in this
regular pattern, the way
that these two black holes
kind of orbit each other,
they warp space in a
pattern, in a systematic way.
Essentially, you can almost
think it as just doing this,
really.
DR. TANYA HILL: And
this way as well.
MR. JACK LINE: And this
way, exactly right.
DR. TANYA HILL: You're
getting squeezed
and pulled, aren't you?
MR. JACK LINE: So kind of if
I was at one end of the laser,
and Ben was at the
other end of the laser,
I'd start doing this,
and you'd do that, right?
You'd go away.
I come in, go away.
So what we can do with these
instruments that we set up
is you can look at
space stretching.
We know how long light should
take to go a certain distance.
And lasers use light.
So if you can shoot a laser
from one point to the other
and watch how time
changes, how long
it takes that laser to get
from one point to the other,
and you watch it changing
in a rhythmic pattern,
the only thing that could
cause that are things
like binary mergers, things
like black holes going
around each other.
So you can actually watch
space warp and change shape.
And Einstein predicted
these things.
They're called grav waves,
gravitational waves.
We've only just got
to the point where
the optics, the lasers and
the mirrors that we use,
have got good enough to
actually see these changes.
But they're minuscule.
DR. TANYA HILL: Like
the size of a proton,
smaller than a proton?
MR. JACK LINE: Yeah, I think
it's smaller than a proton.
So things inside the atoms,
which are what make us up,
you have to be able to look
at space changing-- well,
obviously doing this,
that's a little bit bigger
than the size of a proton,
so ridiculous accuracy.
But they've actually
done it now.
DR. TANYA HILL: Which
is pretty amazing.
So the way Einstein
kind of has taught
us to think about the
Universe is this idea
that there's this sort
of fabric of spacetime.
It doesn't really exist,
but it's a nice analogy
to be able to think about it.
And often the way it's
mentioned is that spacetime
is like a trampoline.
And so gravity is just
you put a big bowling
ball on your trampoline.
It's going to create a
big hole in the center.
And that's what gravity is.
But then of course if you
bounce and pat the trampoline,
then it's going to send
ripples through as well.
And so these are what the
gravitational waves are.
They're the ripples that
travel through this fabric
of spacetime when these
big, massive objects are
moving around.
And it was-- does
someone remember?
The two black holes
that collided,
was it 1.3 billion
light years away?
So this happened 1.3
billion years ago,
set off these ripples,
just like you'd
throw a rock into a pond,
set off some ripples.
And the ripples are
going to be dying down.
And yet we've still managed,
1.3 billion years later,
to be able to detect this kind
of dying down of the ripples
as it's passed over the
Earth and made the Earth
sort of squeeze and stretch
by this minuscule amount--
absolutely amazing.
So astronomers, scientists,
around the world
are really excited about
gravitational waves.
What more can they tell us?
DR. BEN MCKINLEY: Well, yeah,
the amazing thing about it
is it's a completely new
way of doing astronomy.
It's not like a different
frequency of light.
It's not light.
It's an entirely new
scientific field.
These gravitational
waves essentially
are so weak and small
you can only detect them
from things that are
absolutely catastrophic,
so the most violent things, like
these two black holes merging
together and getting so close
and then actually smashing
together.
And do you know how to
do the sound of what
that sounded like?
Because what's interesting
is there's actually the two
black holes smashing together.
If you could, it's
in the audio range.
If you could actually
hear this with your ear--
which you can't.
But if you could, it
would sound like, voop!
It makes a really weird sound.
And that's happening all the
time throughout the Universe.
So eventually when we
get even bigger ones
of these interferometers
that are much more sensitive,
we'll be able to look
at the entire sky
and see voop, voop, voop, voop,
all these black holes smashing
together.
And I think the holy
grail of it is actually
looking right back
to the Big Bang
itself and trying to measure
the gravity waves from when
the actual birth
of the Universe,
like actually
looking at and sort
of listening to the birth
of the Universe itself.
So who knows what
amazing physics we'll
be able to learn from that.
DR. TANYA HILL: Yeah,
because that's something
that light can't probe.
DR. BEN MCKINLEY: That's right.
It's impossible.
DR. TANYA HILL: We were
talking about the MWA is
looking for these holes in
the hydrogen [INAUDIBLE].
They're the first stars
and galaxies lit up.
But we go further
back, and there's
this radiation we call the
cosmic microwave, background
radiation.
It's the remnant
of the Big Bang.
And it allows us to
see just 380,000 years
after the Big Bang.
So the Big Bang happened.
380,000 years later, we've got
our first picture of light.
But we can't use light to
probe that first instance.
But gravity waves
we can, can't we?
So eventually as the
technology gets better,
and we're able to detect more
of these gravitational waves,
we can probe right back to
the earliest times, which
would be really very exciting.
So yeah, gravitational
waves is a new way
of looking at the sky.
We talked about light and
radio with our telescopes.
[INAUDIBLE] has asked
us, what other forms
of electromagnetic
radiation are out there?
MR. JACK LINE: Oh, all
kinds of fun stuff.
Anything under of
the sun-- so UV,
which you're supposed to
avoid with your sun lotion.
That's out there.
Infrared we use to look at dust.
It doesn't sound interesting,
but dust is actually
very important in the way
that light signals reach us.
You've got x-rays, as
Tanya talked before.
Gamma rays-- so there
are these things
called gamma ray bursts that
go off every now and again.
Again, they're very energetic.
So gamma rays are the
most energetic light
that we can see.
And they are pretty
cataclysmic events.
And then microwaves-- so
we use microwaves as well.
There's an interesting new
development in radio waves
which are called FRBs,
which are Fast Radio Bursts.
It turns out you can mimic
the signal of these FRBs
by opening your
microwave oven right
next to your instrument, which
we just recently had problems
with at the Parkes telescope.
It's quite a funny
interesting bit of science.
But there's an actual paper
on, don't open your microwave
next to your radio telescope.
DR. TANYA HILL: So the
key is it's the microwave.
If you're too fast
to want your food--
if you use the microwave,
and you wait the full minute,
and then you get
your food, you're OK.
But if you decide
after 50 seconds,
oh, I'm hungry now, I want
it, and you open, then there's
enough microwave
energy that sets out.
And the telescope
thinks that it's
one of these fast radio
bursts, a different thing
than astronomers are
seeing in the night sky.
But all the different
kinds of-- and they're
all different kinds of light.
It's just their
frequency changes
or their wavelength
changes across.
And each of them tells us
something new and different,
doesn't it?
So you were saying about
the infrared with dust.
One of the great things
with that is firstly,
there is a lot of dust
out there in the Universe.
And so things are
hidden behind the dust.
And we can use infrared to kind
of see some hidden things, can
look into star forming regions.
Ben, do you want to
talk about that at all?
DR. BEN MCKINLEY: I don't
know a lot about the infrared.
I do know that one of the
tricky things about infrared
is that it can't actually
penetrate our atmosphere very
well.
Because it hits the water
molecules and basically gets
blocked.
So in order to see this
different view of the Universe
where you can peer and look at
the dust and the warming that's
happening, you have to get
away from the atmosphere.
So they either stick
it on a satellite, one
of these telescopes,
or a cool thing,
they actually mounted a
telescope inside a Boeing 747.
And they fly it up above
most of the atmosphere.
And that's called a
Stratospheric Observatory
for Infrared Astronomy.
And it's one of the reasons
why I called my daughter
Sofia with an F.
DR. TANYA HILL: Oh, OK, yeah,
because of the observatory.
That's fantastic.
That's great.
Yeah, so we have all
the different types.
Ultraviolet light that
you were talking about,
that allows us to see some
of the really young stars,
doesn't it?
When stars first
are born, they're
very energetic in
ultraviolet light.
So you can kind of use all the
different wavelengths of light.
And again, I think
it's something
that CAASTRO does really well
in terms of it's not just
looking at all the sky, but
then it's all the wavelengths
as well to really piece together
what's going on out there.
 
And now, look, the
last question I
think we might have,
we're going to bring it
all the way right back to
home, back to our little Solar
System, our sun, which is
just one of the many millions
of stars in our galaxy with
all its planets around it.
Back in the '70s, the
Voyager spacecraft
was launched off
Earth and has gone out
to probe the Solar System.
And the question is, has
it left the Solar System?
Jack, have you been
following Voyager at all?
MR. JACK LINE: It has, yeah.
Technically it has.
DR. TANYA HILL:
There's different kind
of edges to the Solar
System, though, isn't there?
So go for it.
MR. JACK LINE: So it
is still sending us
data, which is an absolute
testament to the instrument.
That's insane.
DR. TANYA HILL: What would be
the computer power on Voyager?
Wouldn't it be a watch?
MR. JACK LINE: Maybe like
less than a Casio calculator
that you can get these days.
I mean, that's what they
sent people to the Moon with.
DR. TANYA HILL: And
that was amazing.
Yeah, that was
amazing at the time.
MR. JACK LINE: So
it can basically
sample how many particles
it's surrounded by.
So we know that
our Solar System is
traveling through our galaxy.
And you have what we call
a bow shock at the front.
So essentially there's a
bunch of particles and matter
associated with
our Solar System.
And then there are things
that aren't bound to it.
They're sort of outside it.
And it's almost like
we're a ship sailing
through some water.
You can look at the
way the water flies off
the front of the hull.
So there's a big rise in
the density at that point.
And then after that, it's
kind of there's nothing.
And Voyager, it suggests
from the data, the way
that the density has changed,
how much stuff it can see,
that it has pierced
through that.
It's gone outside.
So it looks like Voyager is
outside the Solar System, which
is the only thing that
has ever done that.
Universally, tiny scale,
but on human scale,
massive, really interesting.
DR. TANYA HILL: Yeah,
it's pretty amazing
that we're able to do that.
So look, I want to thank both
Ben and Jack for being here
today.
They're both researchers at
the University of Melbourne
and part of CAASTRO, the
AIC Center of Excellence
for All-sky Astrophysics.
And as I said at the start
of this, one of the reasons
that we were doing
this today, and it's
a big day here at the Melbourne
Planetarium at Scienceworks,
is that we're launching a brand
new planetarium show called
"Capturing the Cosmos."
It tells you all about the MWA
that we've just talked about,
which these guys work with, and
also the SkyMapper telescope
as well, and what they're
doing to probe dark energy,
to probe the cosmic dark ages,
these big mysteries that we're
trying to solve.
We're trying to understand
more about the Universe.
So thank you all for
your fantastic questions.
And maybe we'll chat
again soon sometime.
Thanks.
DR. BEN MCKINLEY:
Thanks, everyone.
 
