0:00:15.570,0:00:18.330
Space, the final frontier.

0:00:20.370,0:00:23.826
I first heard these words[br]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[br]that the universe had to offer.

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And those dreams, those words,[br]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[br]to become a professional astronomer.

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I learned that the reality was

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I wouldn't be piloting[br]a starship anytime soon.

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

0:00:57.090,0:00:59.890
actually too vast[br]to be explored by spaceship.

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

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Now, I show you before you[br]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[br]of our local galaxy, the Milky Way.

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If you were to go[br]to a darker part of the sky,

0:01:17.229,0:01:19.523
a nice dark site, perhaps in the desert,

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you might see the center[br]of our Milky Way galaxy

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spread out before you,[br]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[br]a local corner of our universe.

0:01:31.430,0:01:34.522
You can see there's[br]a sort of strange dark dust across it.

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Now, that is local dust

0:01:36.290,0:01:38.946
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[br]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[br]like the Hubble Space Telescope.

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Now, astronomers[br]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[br]observing just a tiny patch of the sky

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

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And in this image

0:02:02.330,0:02:03.986
you can see thousands of galaxies,

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and we know that there must be[br]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,[br]I can continue this journey.

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This is easy. I can just[br]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[br]if we just do that.

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

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

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and that's a tiny, tiny slice[br]of what the universe has to offer us.

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There's also two very important[br]problems with using visible light.

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The first is that dust[br]that I mentioned earlier.

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The dust stops the visible light[br]from getting to us.

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

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

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in order to try and explore the universe.

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Say you're standing on a corner,[br]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.

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(Imitates a siren passing by)

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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[br]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,[br]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,[br]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[br]and they appear bluer.

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Objects moving away from us,

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their light waves are stretched,[br]and they appear redder.

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So we call these effects[br]blueshift and redshift.

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Our universe is expanding,

0:03:49.261,0:03:53.356
so everything is moving away[br]from everything else,

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and that means[br]everything appears to be red.

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And oddly enough, as you look[br]more deeply into the universe,

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more distant objects[br]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

0:04:10.659,0:04:13.356
and we were to continue[br]to peer deeply into the universe

0:04:13.380,0:04:14.916
just using the Hubble,

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as we get to a certain distance away,

0:04:17.660,0:04:19.260
everything becomes red,

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and that presents something of a problem.

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Eventually, we get so far away

0:04:24.140,0:04:27.116
everything is shifted into the infrared

0:04:27.140,0:04:28.876
and we can't see anything at all.

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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,

0:04:34.380,0:04:38.106
not just whatever I can see,[br]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[br]using this for decades.

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It's a fantastic technique.

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I show you the Parkes Radio Telescope,[br]affectionately known as "The Dish."

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You may have seen the movie.

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And radio is really brilliant.

0:04:50.911,0:04:53.448
It allows us to peer much more deeply.

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It doesn't get stopped by dust,

0:04:55.690,0:04:57.946
so you can see everything in the universe,

0:04:57.970,0:04:59.826
and redshift is less of a problem

0:04:59.850,0:05:03.050
because we can build receivers[br]that receive across a large band.

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So what does Parkes see when we turn it[br]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.

0:05:13.050,0:05:14.706
All that dust has gone.

0:05:14.730,0:05:18.170
As I mentioned, radio goes[br]straight through dust, so not a problem.

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But the view is very different.

0:05:20.730,0:05:24.546
We can see that the center[br]of the Milky Way is aglow,

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and this isn't starlight.

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This is a light called[br]synchrotron radiation,

0:05:30.090,0:05:34.690
and it's formed from electrons[br]spiraling around cosmic magnetic fields.

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The plane is aglow with this light.

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

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and objects which don't appear to line up

0:05:43.460,0:05:45.780
with anything that we can see[br]with our own eyes.

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But it's hard to really[br]interpret this image,

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

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Radio waves have a wavelength that's long,

0:05:53.900,0:05:56.196
and that makes their resolution poorer.

0:05:56.220,0:05:58.186
This image is also black and white,

0:05:58.210,0:06:01.970
so we don't really know[br]what is the color of everything in here.

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Well, fast-forward to today.

0:06:04.260,0:06:05.716
We can build telescopes

0:06:05.740,0:06:08.266
which can get over these problems.

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

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a fantastic place[br]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:

0:06:19.770,0:06:22.866
no mobile phones, no Wi-Fi, nothing,

0:06:22.890,0:06:25.386
just very, very radio quiet,

0:06:25.410,0:06:28.130
so a perfect place[br]to build a radio telescope.

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The telescope that I've been[br]working on for a few years

0:06:31.890,0:06:33.826
is called the Murchison Widefield Array,

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

0:06:36.890,0:06:40.146
This is a group of undergraduate[br]and postgraduate students

0:06:40.170,0:06:41.426
located in Perth.

0:06:41.450,0:06:43.043
We call them the Student Army,

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and they volunteered their time[br]to build a radio telescope.

0:06:45.908,0:06:47.548
There's no course credit for this.

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And they're putting together[br]these radio dipoles.

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

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And here we are deploying them[br]across the desert.

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The final telescope[br]covers 10 square kilometers

0:07:02.540,0:07:04.676
of the Western Australian desert.

0:07:04.700,0:07:07.618
And the interesting thing is,[br]there's no moving parts.

0:07:07.642,0:07:09.899
We just deploy these little antennas

0:07:09.923,0:07:11.780
essentially on chicken mesh.

0:07:11.804,0:07:13.276
It's fairly cheap.

0:07:13.300,0:07:15.276
Cables take the signals

0:07:15.300,0:07:16.935
from the antennas

0:07:16.959,0:07:19.516
and bring them[br]to central processing units.

0:07:19.540,0:07:21.316
And it's the size of this telescope,

0:07:21.340,0:07:23.996
the fact that we've built it[br]over the entire desert

0:07:24.020,0:07:26.820
that gives us a better[br]resolution than Parkes.

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Now, eventually all those cables[br]bring them to a unit

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which sends it off[br]to a supercomputer here in Perth,

0:07:34.580,0:07:35.876
and that's where I come in.

0:07:35.900,0:07:37.051
(Sighs)

0:07:37.075,0:07:38.356
Radio data.

0:07:38.380,0:07:40.396
I have spent the last five years

0:07:40.420,0:07:43.276
working with very difficult,[br]very interesting data

0:07:43.300,0:07:45.276
that no one had really looked at before.

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I've spent a long time calibrating it,

0:07:47.460,0:07:50.676
running millions of CPU hours[br]on supercomputers

0:07:50.700,0:07:52.926
and really trying to understand that data.

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With this data,

0:07:54.125,0:07:58.148
we've performed a survey[br]of the entire southern sky,

0:07:58.172,0:08:03.286
the GaLactic and Extragalactic[br]All-sky MWA Survey,

0:08:03.310,0:08:04.825
or GLEAM, as I call it.

0:08:05.260,0:08:07.155
Imagine you went to the Murchison,

0:08:07.179,0:08:09.075
you camped out underneath the stars

0:08:09.099,0:08:10.716
and you looked towards the south.

0:08:10.740,0:08:12.407
You saw the south's celestial pole,

0:08:12.431,0:08:13.636
the galaxy rising.

0:08:13.660,0:08:16.276
If I fade in the radio light,

0:08:16.300,0:08:18.956
this is what we observe with our survey.

0:08:18.980,0:08:22.036
You can see that the galactic plane[br]is no longer dark with dust.

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It's alight with synchrotron radiation,

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and thousands of dots --

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our large Magellanic Cloud,[br]our nearest galactic neighbor,

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is orange instead[br]of its more familiar blue-white.

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

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If we look back[br]towards the galactic center,

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

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low resolution, black and white,

0:08:43.700,0:08:46.246
and we fade to the GLEAM view,

0:08:46.270,0:08:50.126
you can see the resolution[br]has gone up by a factor of a hundred.

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We now have a color view of the sky,

0:08:53.030,0:08:54.366
a technicolor view.

0:08:54.390,0:08:57.366
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[br]the lowest frequencies red

0:09:03.510,0:09:05.126
and the highest frequencies blue,

0:09:05.150,0:09:06.726
and the middle ones green.

0:09:06.750,0:09:08.966
And that gives us this rainbow view.

0:09:08.990,0:09:10.846
And this isn't just false color.

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The colors in this image[br]tell us about the physical processes

0:09:13.830,0:09:15.070
going on in the universe.

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

0:09:18.430,0:09:19.886
it's alight with synchrotron,

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which is mostly reddish orange,

0:09:22.310,0:09:25.430
but if we look very closely,[br]we see little blue dots.

0:09:25.990,0:09:27.566
Now, if we zoom in,

0:09:27.590,0:09:30.126
these blue dots are ionized plasma

0:09:30.150,0:09:31.790
around very bright stars,

0:09:32.350,0:09:35.126
and what happens[br]is that they block the red light,

0:09:35.150,0:09:36.790
so they appear blue.

0:09:37.350,0:09:40.016
And these can tell us[br]about these star-forming regions

0:09:40.040,0:09:41.296
in our galaxy.

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And we just see them immediately.

0:09:42.960,0:09:46.016
We look at the galaxy,[br]and the color tells us that they're there.

0:09:46.040,0:09:47.616
You can see little soap bubbles,

0:09:47.640,0:09:50.834
little circular images[br]around the galactic plane,

0:09:50.858,0:09:52.858
and these are supernova remnants.

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When a star explodes,

0:09:55.300,0:09:57.756
its outer shell is cast off

0:09:57.780,0:10:01.076
and it travels outward into space[br]gathering up material,

0:10:01.100,0:10:03.060
and it produces a little shell.

0:10:03.780,0:10:07.156
It's been a long-standing[br]mystery to astronomers

0:10:07.180,0:10:09.260
where all the supernova remnants are.

0:10:09.940,0:10:14.276
We know that there must be a lot[br]of high-energy electrons in the plane

0:10:14.300,0:10:16.956
to produce the synchrotron[br]radiation that we see,

0:10:16.980,0:10:19.556
and we think they're produced[br]by supernova remnants,

0:10:19.580,0:10:21.356
but there don't seem to be enough.

0:10:21.380,0:10:25.276
Fortunately, GLEAM is really, really[br]good at detecting supernova remnants.

0:10:26.160,0:10:27.416
That's fine.

0:10:27.440,0:10:29.436
We've explored our little local universe,

0:10:29.460,0:10:31.836
but I wanted to go deeper,[br]I wanted to go further.

0:10:31.860,0:10:34.116
I wanted to go beyond the Milky Way.

0:10:34.140,0:10:37.916
Well, as it happens, we can see a very[br]interesting object in the top right,

0:10:37.940,0:10:40.156
and this is a local radio galaxy,

0:10:40.180,0:10:41.420
Centaurus A.

0:10:41.860,0:10:43.011
If we zoom in on this,

0:10:43.035,0:10:46.435
we can see that there are[br]two huge plumes going out into space.

0:10:47.220,0:10:50.116
And if you look right in the center[br]between those two plumes,

0:10:50.140,0:10:52.516
you'll see a galaxy just like our own.

0:10:52.540,0:10:54.996
It's a spiral. It has a dust lane.

0:10:55.020,0:10:56.636
It's a normal galaxy.

0:10:56.660,0:10:59.676
But these jets[br]are only visible in the radio.

0:10:59.700,0:11:02.876
If we looked in the visible,[br]we wouldn't even know they were there,

0:11:02.900,0:11:05.940
and they're thousands of times larger[br]than the host galaxy.

0:11:06.500,0:11:08.900
What's going on?[br]What's producing these jets?

0:11:10.180,0:11:13.716
At the center of every galaxy[br]that we know about

0:11:13.740,0:11:15.996
is a supermassive black hole.

0:11:16.020,0:11:17.509
Now, black holes are invisible.

0:11:18.060,0:11:21.076
All you can see is the deflection[br]of the light around them,

0:11:21.100,0:11:25.396
and occasionally, when a star[br]or a cloud of gas comes into their orbit,

0:11:25.420,0:11:28.156
it is ripped apart by tidal forces,

0:11:28.180,0:11:30.660
forming what we call an accretion disk.

0:11:31.260,0:11:34.476
The accretion disk[br]glows brightly in the x-rays,

0:11:34.500,0:11:38.916
and huge magnetic fields[br]can launch the material into space

0:11:38.940,0:11:40.660
at nearly the speed of light.

0:11:41.053,0:11:43.831
These jets are visible in the radio

0:11:43.855,0:11:46.015
and this is what we pick up in our survey.

0:11:46.660,0:11:49.436
Well, very well,[br]so we've seen one radio galaxy.

0:11:49.460,0:11:51.636
But if you just look[br]at the top of that image,

0:11:51.660,0:11:53.396
you'll see another radio galaxy.

0:11:53.420,0:11:56.660
It's a little bit smaller,[br]and that's just because it's further away.

0:11:57.148,0:11:59.836
OK. Two radio galaxies.

0:11:59.860,0:12:01.334
We can see this. This is fine.

0:12:01.358,0:12:03.095
Well, what about all the other dots?

0:12:03.119,0:12:04.679
Presumably those are just stars.

0:12:05.060,0:12:06.276
They're not.

0:12:06.300,0:12:07.900
They're all radio galaxies.

0:12:08.550,0:12:11.446
Every single one of the dots in this image

0:12:11.470,0:12:13.150
is a distant galaxy,

0:12:13.174,0:12:16.031
millions to billions of light-years away

0:12:16.055,0:12:18.726
with a supermassive[br]black hole at its center

0:12:18.750,0:12:22.190
pushing material into space[br]at nearly the speed of light.

0:12:22.214,0:12:23.713
It is mind-blowing.

0:12:24.850,0:12:28.586
And this survey is even larger[br]than what I've shown here.

0:12:28.610,0:12:31.146
If we zoom out to[br]the full extent of the survey,

0:12:31.170,0:12:34.538
you can see I found 300,000[br]of these radio galaxies.

0:12:35.140,0:12:37.244
We've discovered all of these galaxies

0:12:37.268,0:12:40.828
right back to the very first[br]supermassive black holes.

0:12:41.680,0:12:44.640
There's something even more in this image.

0:12:45.320,0:12:47.716
I'll take you right back[br]to the dawn of time.

0:12:47.740,0:12:50.896
When the universe formed,[br]it was a big bang,

0:12:50.920,0:12:54.816
which left the universe as a sea[br]of hydrogen, neutral hydrogen.

0:12:54.840,0:12:57.616
And when the very first stars[br]and galaxies switched on,

0:12:57.640,0:12:59.736
they ionized that hydrogen.

0:12:59.760,0:13:03.200
So the universe went[br]from neutral to ionized.

0:13:04.080,0:13:07.256
That imprinted a signal all around us.

0:13:07.280,0:13:09.016
Everywhere, it pervades us,

0:13:09.040,0:13:10.465
like the Force.

0:13:10.489,0:13:11.494
(Laughter)

0:13:11.518,0:13:14.358
Because that happened so long ago,

0:13:14.920,0:13:16.720
the signal was redshifted,

0:13:17.480,0:13:20.776
so now that signal[br]is at very low frequencies.

0:13:20.800,0:13:23.256
It's at the same frequency as my survey,

0:13:23.280,0:13:24.656
but it's so faint.

0:13:24.680,0:13:28.560
It's a billionth the size[br]of any of the objects in my survey.

0:13:29.240,0:13:33.866
So our telescope may not be quite[br]sensitive enough to pick up this signal.

0:13:33.890,0:13:36.386
However, there's a new radio telescope.

0:13:36.410,0:13:38.066
So I can't have a starship,

0:13:38.090,0:13:39.346
but I can hopefully have

0:13:39.370,0:13:42.226
one of the biggest[br]radio telescopes in the world.

0:13:42.250,0:13:45.866
We're building the Square Kilometre Array,[br]a new radio telescope,

0:13:45.890,0:13:48.626
and it's going to be a thousand[br]times bigger than the MWA,

0:13:48.650,0:13:51.866
a thousand times more sensitive,[br]and have an even better resolution.

0:13:51.890,0:13:54.106
So we should find[br]tens of millions of galaxies.

0:13:54.130,0:13:56.466
And perhaps, deep in that signal,

0:13:56.490,0:14:00.666
I will get to look upon the very first[br]stars and galaxies switching on,

0:14:00.690,0:14:03.050
the beginning of time itself.

0:14:03.514,0:14:04.665
Thank you.

0:14:04.689,0:14:11.689
(Applause)