WEBVTT

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Space, the final frontier.

NOTE Paragraph

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I first heard these words
when I was just six years old,

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and I was completely inspired.

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I wanted to explore strange new worlds.

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I wanted to seek out new life.

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I wanted to see everything
that the universe had to offer.

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And those dreams, those words,
they took me on a journey,

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a journey of discovery,

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through school, through university,

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to do a PhD and finally
to become a professional astronomer.

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Now, I learned two amazing things,

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one slightly unfortunate,

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when I was doing my PhD.

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I learned that the reality was

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I wouldn't be piloting
a starship anytime soon.

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But I also learned that the universe
is strange, wonderful and vast,

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actually too vast
to be explored by spaceship.

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And so I turned my attention
to astronomy, to using telescopes.

NOTE Paragraph

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Now, I show you before you
an image of the night sky.

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You might see it anywhere in the world.

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And all of these stars are part
of our local galaxy, the Milky Way.

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Now, if you were to go
to a darker part of the sky,

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a nice dark site, perhaps in the desert,

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you might see the center
of our Milky Way galaxy

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spread out before you,
hundreds of billions of stars.

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And it's a very beautiful image.

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It's colorful.

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And again, this is just
a local corner of our universe.

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You can see there's
a sort of strange dark dust across it.

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Now, that is local dust

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that's obscuring the light of the stars.

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But we can do a pretty good job.

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Just with our own eyes, we can explore
our little corner of the universe.

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It's possible to do better.

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You can use wonderful telescopes
like the Hubble Space Telescope.

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Now, astronomers
have put together this image.

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It's called the Hubble Deep Field,

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and they've spent hundreds of hours
observing just a tiny patch of the sky

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no larger than your thumbnail
held at arm's length.

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And in this image

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you can see thousands of galaxies,

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and we know that there must be
hundreds of millions, billions of galaxies

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in the entire universe,

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some like our own and some very different.

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So you think, OK, well,
I can continue this journey.

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This is easy. I can just
use a very powerful telescope

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and just look at the sky, no problem.

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It's actually really missing out
if we just do that.

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Now, that's because
everything I've talked about so far

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is just using the visible spectrum,
just the thing that your eyes can see,

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and that's a tiny slice,

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a tiny, tiny slice
of what the universe has to offer us.

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Now, there's also two very important
problems with using visible light.

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Not only are we missing out
on all the other processes

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that are emitting other kinds of light,

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but there's two issues.

NOTE Paragraph

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Now, the first is that dust
that I mentioned earlier.

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The dust stops the visible light
from getting to us.

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So as we look deeper
into the universe, we see less light.

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The dust stops it getting to us.

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But there's a really strange problem
with using visible light

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in order to try and explore the universe.

NOTE Paragraph

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Now take a break for a minute.

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Say you're standing on a corner,
a busy street corner.

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There's cars going by.

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An ambulance approaches.

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It has a high-pitched siren.

NOTE Paragraph

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(Imitates a siren passing by)

NOTE Paragraph

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The siren appeared to change in pitch

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as it moved towards and away from you.

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The ambulance driver did not change
the siren just to mess with you.

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That was a product of your perception.

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The sound waves,
as the ambulance approached,

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were compressed,

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and they changed higher in pitch.

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As the ambulance receded,
the sound waves were stretched,

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and they sounded lower in pitch.

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The same thing happens with light.

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Objects moving towards us,

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their light waves are compressed
and they appear bluer.

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Objects moving away from us,

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their light waves are stretched,
and they appear redder.

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So we call these effects
blueshift and redshift.

NOTE Paragraph

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Now, our universe is expanding,

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so everything is moving away
from everything else,

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and that means
everything appears to be red,

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and oddly enough, as you look
more deeply into the universe,

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more distant objects
are moving away further and faster,

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so they appear more red.

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So if I come back to the Hubble Deep Field

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and we were to continue
to peer deeply into the universe

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just using the Hubble,

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as we get to a certain distance away,

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everything becomes red,

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and that presents something of a problem.

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Eventually, we get so far away

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everything is shifted into the infrared

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and we can't see anything at all.

NOTE Paragraph

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So there must be a way around this.

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Otherwise, I'm limited in my journey.

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I wanted to explore the whole universe,

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not just whatever I can see,
you know, before the redshift kicks in.

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There is a technique.

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It's called radio astronomy.

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Astronomers have been
using this for decades.

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It's a fantastic technique.

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I show you the Parkes Radio Telescope,
affectionately known as the Dish.

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You may have seen the movie.

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And radio is really brilliant.

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It allows us to peer much more deeply.

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It doesn't get stopped by dust,

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so you can see everything in the universe,

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and redshift is less of a problem

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because we can build receivers
that receive across a large band.

NOTE Paragraph

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So what does Parkes see when we turn it
to the center of the Milky Way?

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We should see something fantastic, right?

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Well, we do see something interesting.

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All that dust has gone.

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As I mentioned, radio goes
straight through dust, so not a problem.

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But the view is very different.

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We can see that the center
of the Milky Way is aglow,

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and this isn't starlight.

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This is a light called
synchrotron radiation,

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and it's formed from electrons
spiraling around cosmic magnetic fields.

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So the plane is aglow with this light.

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And we can also see
strange tufts coming off of it,

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and objects which don't appear to line up

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with anything that we can see
with our own eyes.

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But it's hard to really
interpret this image,

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because as you can see,
it's very low resolution.

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Radio waves have a wavelength that's long,

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and that makes their resolution poorer.

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This image is also black and white,

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so we don't really know
what is the color of everything in here.

NOTE Paragraph

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Well, fast-forward to today.

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We can build telescopes

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which can get over these problems.

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Now, I'm showing you here an image
of the Murchison Radio Observatory,

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a fantastic place
to build radio telescopes.

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It's flat, it's dry,

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and most importantly, it's radio quiet:

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no mobile phones, no Wi-Fi, nothing,

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just very, very radio quiet,

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so a perfect place
to build a radio telescope.

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Now, the telescope that I've been
working on for a few years

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is called the Murchison Widefield Array,

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and I'm going to show you
a little time lapse of it being built.

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This is a group of undergraduate
and postgraduate students

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located in Perth.

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We call them the Student Army,

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and they volunteered their time
to build a radio telescope.

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There's no course credit for this.

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And they're putting together
these radio dipoles.

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They just receive at low frequencies,
a bit like your FM radio or your TV.

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And here we are deploying them
across the desert.

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The final telescope
covers 10 square kilometers

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of the Western Australian Desert.

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And the interesting thing is,
there's no moving parts.

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We just deploy these little antennas

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essentially on chicken mesh.

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It's fairly cheap.

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Cables take the signals

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from the antennas

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and bring them
to central processing units.

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And it's the size of this telescope,

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the fact that we've built it
over the entire desert

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that gives us a better
resolution than Parkes.

NOTE Paragraph

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Now, eventually all those cables
bring them to a unit

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which sends it off
to a supercomputer here in Perth,

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and that's where I come in.

NOTE Paragraph

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(Sighs)

NOTE Paragraph

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Radio data.

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I have spent the last five years

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working with very difficult,
very interesting data

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that no one had really looked at before.

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I've spent a long time calibrating it,

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running millions of CPU hours
on supercomputers

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and really trying to understand that data.

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And with this telescope,

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with this data,

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we've performed a survey
of the entire southern sky,

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the GaLactic and Extragalactic
All-sky MWA Survey,

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or GLEAM, as I call it.

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And I'm very excited.

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This survey is just about to be published,
but it hasn't been shown yet,

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so you are literally the first people

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to see this southern survey
of the entire sky.

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So I'm delighted to share with you
some images from this survey.

NOTE Paragraph

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Now, imagine you went to the Murchison,

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you camped out underneath the stars

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and you looked towards the south.

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You saw the south's celestial pole,

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the galaxy rising.

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If I fade in the radio light,

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this is what we observe with our survey.

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You can see that the galactic plane
is no longer dark with dust.

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It's alight with synchrotron radiation,

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and thousands of dots are in the sky.

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Our large Magellanic Cloud,
our nearest galactic neighbor,

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is orange instead
of its more familiar blue-white.

NOTE Paragraph

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So there's a lot going on in this.
Let's take a closer look.

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If we look back
towards the galactic center,

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where we originally saw the Parkes image
that I showed you earlier,

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low resolution, black and white,

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and we fade to the GLEAM view,

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you can see the resolution
has gone up by a factor of a hundred.

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We now have a color view of the sky,

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a technicolor view.

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Now, it's not a false color view.

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These are real radio colors.

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What I've done is I've colored
the lowest frequencies red

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and the highest frequencies blue,

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and the middle ones green.

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And that gives us this rainbow view.

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And this isn't just false color.

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The colors in this image
tell us about the physical processes

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going on in the universe.

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So for instance, if you look
along the plane of the galaxy,

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it's alight with synchrotron,

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which is mostly reddish orange,

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but if we look very closely,
we see little blue dots.

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Now, if we zoom in,

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these blue dots are ionized plasma

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around very bright stars,

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and what happens
is that they block the red light,

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so they appear blue.

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And these can tell us
about these star-forming regions

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in our galaxy.

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And we just see them immediately.

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We look at the galaxy
and the color tells us that they're there.

NOTE Paragraph

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You can see little soap bubbles,

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little circular images
around the galactic plane,

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and these are supernova remnants.

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When a star explodes,

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its outer shell is cast off

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and it travels outward into space
gathering up material,

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and it produces a little shell.

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It's been a long-standing
mystery to astronomers

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where all the supernova remnants are.

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We know that there must be a lot
of high-energy electrons in the plane

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to produce the synchrotron
radiation that we see,

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and we think they're produced
by supernova remnants,

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but there don't seem to be enough.

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Fortunately, GLEAM is really, really
good at detecting supernova remnants,

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so we're hoping to have
a new paper out on that soon.

NOTE Paragraph

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Now, that's fine.

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We've explored our little local universe,

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but I wanted to go deeper,
I wanted to go further.

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I wanted to go beyond the Milky Way.

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Well, as it happens, we can see a very
interesting object in the top right,

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and this is a local radio galaxy,

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Centaurus A.

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If we zoom in on this,

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we can see that there are
two huge plumes going out into space,

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and if you look right in the center
between those two plumes,

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you'll see a galaxy just like our own.

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It's a spiral. It has a dust lane.

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It's a normal galaxy.

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But these jets
are only visible in the radio.

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If we looked in the visible,
we wouldn't even know they were there,

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and they're thousands of times larger
than the host galaxy.

NOTE Paragraph

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What's going on?
What's producing these jets?

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At the center of every galaxy
that we know about

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is a supermassive black hole.

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Now, black holes are invisible.
That's why they're called that.

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All you can see is the deflection
of the light around them,

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and occasionally, when a star
or a cloud of gas comes into their orbit,

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it is ripped apart by tidal forces,

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forming what we call an accretion disk.

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The accretion disk
glows brightly in the x-rays,

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and huge magnetic fields
can launch the material into space

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at nearly the speed of light.

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So these jets are visible in the radio

00:12:27.240 --> 00:12:29.400
and this is what we pick up in our survey.

NOTE Paragraph

00:12:30.040 --> 00:12:34.056
Well, very well, so we've seen
one radio galaxy. That's nice.

00:12:34.080 --> 00:12:36.256
But if you just look
at the top of that image,

00:12:36.280 --> 00:12:38.016
you'll see another radio galaxy.

00:12:38.040 --> 00:12:41.280
It's a little bit smaller,
and that's just because it's further away.

00:12:41.800 --> 00:12:44.456
OK. Two radio galaxies.

00:12:44.480 --> 00:12:46.056
We can see this. This is fine.

00:12:46.080 --> 00:12:47.816
Well, what about all the other dots?

00:12:47.840 --> 00:12:49.400
Presumably those are just stars.

00:12:49.880 --> 00:12:51.096
They're not.

00:12:51.120 --> 00:12:52.720
They're all radio galaxies.

00:12:53.320 --> 00:12:56.216
Every single one of the dots in this image

00:12:56.240 --> 00:12:57.976
is a distant galaxy,

00:12:58.000 --> 00:13:00.856
millions to billions of light-years away

00:13:00.880 --> 00:13:03.496
with a supermassive
black hole at its center

00:13:03.520 --> 00:13:07.096
pushing material into space
at nearly the speed of light.

00:13:07.120 --> 00:13:08.880
It is mind-blowing.

00:13:09.680 --> 00:13:13.416
And this survey is even larger
than what I've shown here.

00:13:13.440 --> 00:13:15.976
If we zoom out to
the full extent of the survey,

00:13:16.000 --> 00:13:20.096
you can see I found 300,000
of these radio galaxies.

00:13:20.120 --> 00:13:23.016
So it's truly an epic journey.

00:13:23.040 --> 00:13:25.696
We've discovered all of these galaxies

00:13:25.720 --> 00:13:29.280
right back to the very first
supermassive black holes.

00:13:29.960 --> 00:13:32.680
I'm very proud of this
and it will be published next week.

NOTE Paragraph

00:13:33.280 --> 00:13:36.096
Now, that's not all.

00:13:36.120 --> 00:13:40.456
I've explored the furthest reaches
of the galaxy with this survey,

00:13:40.480 --> 00:13:43.440
but there's something
even more in this image.

NOTE Paragraph

00:13:44.320 --> 00:13:47.616
Now, I'll take you right back
to the dawn of time.

00:13:47.640 --> 00:13:51.296
When the universe formed,
it was a big bang,

00:13:51.320 --> 00:13:55.376
which left the universe
as a sea of hydrogen,

00:13:55.400 --> 00:13:56.896
neutral hydrogen,

00:13:56.920 --> 00:13:59.696
and when the very first stars
and galaxies switched on,

00:13:59.720 --> 00:14:01.816
they ionized that hydrogen.

00:14:01.840 --> 00:14:05.280
So the universe went
from neutral to ionized.

00:14:06.160 --> 00:14:09.336
That imprinted a signal all around us.

00:14:09.360 --> 00:14:11.096
Everywhere, it pervades us,

00:14:11.120 --> 00:14:12.536
like the Force.

00:14:12.560 --> 00:14:16.280
Now, because that happened so long ago,

00:14:17.000 --> 00:14:18.800
the signal was redshifted,

00:14:19.560 --> 00:14:22.856
so now that signal
is at very low frequencies.

00:14:22.880 --> 00:14:25.336
It's at the same frequency as my survey,

00:14:25.360 --> 00:14:26.736
but it's so faint.

00:14:26.760 --> 00:14:30.640
It's a billionth the size
of any of the objects in my survey.

00:14:31.320 --> 00:14:36.216
So our telescope may not be quite
sensitive enough to pick up this signal.

00:14:36.240 --> 00:14:38.736
However, there's a new radio telescope.

00:14:38.760 --> 00:14:40.416
So I can't have a starship,

00:14:40.440 --> 00:14:41.696
but I can hopefully have

00:14:41.720 --> 00:14:44.576
one of the biggest
radio telescopes in the world.

00:14:44.600 --> 00:14:48.216
We're build the Square Kilometre Array,
a new radio telescope,

00:14:48.240 --> 00:14:50.976
and it's going to be a thousand
times bigger than the MWA,

00:14:51.000 --> 00:14:54.216
a thousand times more sensitive,
and have an even better resolution.

00:14:54.240 --> 00:14:56.456
So we should find
tens of millions of galaxies.

00:14:56.480 --> 00:14:58.816
And perhaps, deep in that signal,

00:14:58.840 --> 00:15:03.016
I will get to look upon the very first
stars and galaxies switching on,

00:15:03.040 --> 00:15:05.400
the beginning of time itself.

NOTE Paragraph

00:15:05.920 --> 00:15:07.136
Thank you.

NOTE Paragraph

00:15:07.160 --> 00:15:09.920
(Applause)