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Radio Astronomy – Listening to the Invisible Sky · Talking Science

0:00
So I want you to picture yourself years ago.
0:02
You are in the backseat of a car driving somewhere
0:06
completely remote after dark. Right, way out
0:09
there. Yeah, like the streetlights vanished an
0:10
hour ago. And you're just idly turning the dial
0:13
on an old car radio, searching the empty spaces
0:16
between stations. And for a moment, you land
0:18
on nothing but hiss. Just that, you know, soft,
0:22
structureless, white noise that sounds like empty
0:24
air. But the wild thing is that static isn't
0:27
just terrestrial interference. I mean, sure,
0:30
some of it is lightning from a storm hundreds
0:32
of miles away or the spark plugs in the car engine
0:36
itself. Right. But buried inside that really
0:38
mundane noise washing over the car in these waves,
0:41
far too faint for that little antenna to isolate,
0:43
is genuine radiation arriving from deep space.
0:47
Oh, wow. You are literally listening to the cosmos.
0:49
And some of those faint crackles, they're actually
0:51
older than the stars themselves. I really love
0:54
that. Because, you know, we spend so much time
0:57
looking up at the night sky and we just assume
0:59
the universe is this silent, peaceful tapestry
1:01
of pinpricks of light. Exactly. It looks so still.
1:04
It does. But the mission of today's deep dive
1:08
is really about the reality that the sky is actively
1:11
broadcasting. It is constantly screaming with
1:14
energy, just in a way that is completely invisible
1:16
to our human biology. We are going to explore
1:18
how humanity finally figured out how to listen
1:21
to that invisible sky, right? We'll look at the
1:23
engineering miracles that let us actually tune
1:25
in. And what those radio waves reveal about the
1:28
hidden structure of our galaxy that, like a normal
1:31
telescope, physically cannot show us. Yeah. And
1:34
we'll also get into why the vast silent stretches
1:36
of the Australian outback have become one of
1:39
the premier listening posts on Earth. Totally.
1:42
But to really get why this matters, I think we
1:45
have to talk about our own biological biases
1:47
first. because we tend to think of light as just
1:50
the colors we can see with our eyes. Right, which
1:52
is such a tiny, limited view. Yeah, visible light
1:55
is just this one minuscule sliver of the whole
1:58
electromagnetic spectrum. We are swimming in
2:00
a much larger family of waves. I mean, visible
2:03
light, X -rays, ultraviolet, infrared, and radio
2:05
waves, they are all fundamentally the exact same
2:08
phenomenon. They're all just light. Exactly.
2:11
They are all oscillating electric and magnetic
2:14
fields traveling through the vacuum of space
2:16
at the speed of light. The only real difference
2:19
is their physical scale. And the scale difference
2:21
is just staggering. We don't need to get bogged
2:24
down in the textbook definitions here, but just
2:26
think about the physical length of a single wave.
2:28
Right. Visible light waves are microscopic, like
2:31
a single wave is smaller than a speck of dust.
2:34
But radio waves? They can be massive. Oh, absolutely
2:38
massive. We are talking about waves that stretch
2:41
from a few millimeters to literally several kilometers
2:44
long from one peak to the next. Kilometers long.
2:47
Yeah. And because of that sheer physical size,
2:49
they interact with the universe in a completely
2:52
different way than visible light does. Well,
2:54
and it makes you wonder why we only see the tiny
2:56
ones. Right. Like why did human eyes evolve to
2:59
detect that one tiny microscopic band? It's simply
3:02
because that happens to be the frequency where
3:05
our sun shines. Oh, sure. And it's where the
3:08
Earth's atmosphere happens to be mostly transparent.
3:11
So it was purely a biological survival adaptation.
3:14
It's not because visible light is objectively
3:17
the best way to view the universe. It's like
3:20
our eyes are basically an old AM FM radio where
3:23
the dial has been like permanently super glued
3:27
to just one single station. That is a great way
3:29
to put it. Right. We're getting that one local
3:31
broadcast loud and clear. Yeah. But we are completely
3:34
blind. to the high -energy, wild broadcast happening
3:38
all across the rest of the dial. And when we
3:40
finally figure out how to unglue that dial, radio
3:43
waves give us two really massive advantages over
3:46
optical light. Okay, what's the first one? The
3:48
first advantage is penetration. So if you point
3:51
a standard optical telescope at the center of
3:53
the Milky Way, you don't actually see the center.
3:55
Because there's stuff in the way. Right. You
3:57
see this massive dark wall of interstellar dust
4:00
and gas blocking the view. Visible light waves
4:03
are so incredibly small that when they hit those
4:05
dust particles, they scatter and just get absorbed.
4:08
Okay. I like to think of this like a short, choppy
4:11
wave on a lake hitting a wooden pier. The wave
4:14
crashes into the obstacle, breaks apart, just
4:17
stops. Exactly. But a radio wave is entirely
4:20
different because of its size. It's more like
4:21
a massive, slow -rolling ocean swell. Oh, I see.
4:25
When that huge, long ocean swell encounters that
4:28
exact same wooden pier, it just glides right
4:31
past it, completely undisturbed. So that rolling
4:34
ocean swell allows radio waves to travel what?
4:38
tens of thousands of light years straight through
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the densest, dustiest parts of our galaxy. Yeah,
4:43
carrying information directly to us from the
4:46
galactic core, stuff we could never see with
4:48
our eyes. That is so cool. And you said there
4:50
was a second advantage. Yeah, the second advantage
4:52
is that radio waves trace entirely different
4:54
physical processes in the universe. Meaning what
4:57
exactly? Well, because when we look at a star
4:59
with our eyes, we are mostly just seeing thermal
5:02
radiation. So we're seeing it glow simply because
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it's hot. Right. Exactly like a campfire or an
5:07
old incandescent light bulb. But when you turn
5:10
into the radio frequencies, you start picking
5:12
up what physicists call synchrotron radiation.
5:15
Synchrotron radiation. OK, that sounds intense.
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It really is. And it has absolutely nothing to
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do with temperature. Synchrotron radiation happens
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when charged particles like electrons get caught
5:25
in unbelievably powerful magnetic fields. Oh,
5:29
wow. These fields act like cosmic particle accelerators.
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They whip the electrons. around at close to the
5:35
speed of light. And as they get flung along these
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magnetic pathways, they bleed off energy in the
5:40
form of radio waves. So we aren't just looking
5:42
at hot gas anymore. We're looking at like...
5:45
The most violent, extreme environments in the
5:47
universe. Exactly. We're looking at the chaotic
5:49
aftermath of exploded stars or the churning magnetic
5:53
maelstroms surrounding black holes. Things that
5:56
would just look dark to a normal telescope. Yeah,
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in a normal telescope, those environments might
6:00
be totally obscured. But in a radio telescope,
6:03
they are blazing beacons of activity. Which brings
6:06
us to the history part of this deep dive. Because
6:08
finding this out was a complete, brilliant accident,
6:12
wasn't it? It really was. I mean, to see how
6:15
humanity first tuned into these synchrotron broadcasts,
6:18
we have to go back to the early 1930s. Enter
6:20
Carl Jansky. Right. A guy named Carl Jansky who
6:23
was working as an engineer for Bell Telephone
6:26
Laboratories. And his job was incredibly... grounded,
6:30
right? He wasn't looking for black holes. No,
6:32
not at all. He was just tasked with figuring
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out what was causing static interference on the
6:37
company's new transatlantic radio telephone service.
6:40
He was literally just trying to clear up the
6:42
line for international phone calls. So he builds
6:44
this wild contraption. People actually nicknamed
6:47
it Jansky's merry -go -round. Yeah, it was this
6:50
large, awkward antenna structure built on a turntable
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made out of salvaged wheels from an old Ford
6:55
Model T. Just brilliant backyard -style engineering
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at a major lab. Totally. And he just slowly rotates
7:01
this thing, methodically mapping every single
7:04
crackle of static he can find. And he tracks
7:07
down the obvious culprits pretty easily, right?
7:09
Like nearby thunderstorms. Yeah, thunderstorms
7:11
are easy to find. But there was this one persistent,
7:14
faint hiss. that he just couldn't isolate. It
7:18
was this steady background hum. I love this part
7:21
of the history because the vital clue wasn't
7:23
in the sound of the hiss itself. The clue was
7:26
in the clock. Dansky notices that this faint
7:29
hiss hits its absolute strongest point every
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23 hours and 56 minutes, which is a very specific
7:36
number. It is because a normal Earth day, which
7:39
is tied to the sun, is 24 hours. But 23 hours
7:43
and 56 minutes is what we call a... sidereal
7:45
day. And that four minute difference changes
7:47
literally everything. It does. A sidereal day
7:50
is the time it takes for the Earth to rotate
7:52
relative to the distant background stars, not
7:55
the sun. So the moment he saw that 23 hour and
7:58
56 minute cycle, he knew without a doubt that
8:01
whatever was causing the static on his phone
8:02
lines was not coming from Earth. Right. It wasn't
8:05
coming from our sun. It was locked to the rotation
8:07
of the stars themselves. Yeah. And he eventually
8:10
traces the strongest part of that signal to the
8:12
constellation Sagittarius, which we now know
8:15
is the exact location of the supermassive black
8:18
hole at the center of the Milky Way. It's just
8:20
wild. Jansky accidentally discovered that our
8:23
galaxy was radiating immense amounts of energy.
8:26
Yes. And then this is the part that gets me.
8:29
He takes this monumental paradigm shifting discovery.
8:33
back to his bosses at Bell Labs. And they completely
8:36
ignore it. They just shrug. They basically say,
8:39
well, the static isn't something we can fix,
8:41
so get back to working on the telephones. It
8:44
is baffling to me. How does a company stumble
8:47
onto the radio emissions of the cosmos and just
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go back to fixing phones? Well, corporate priorities
8:52
rarely align with accidental astrophysics. Yeah,
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it's not. And honestly, the professional astronomy
8:56
community didn't pay much attention either, mostly
8:58
because this was seen as radio engineering, not
9:01
traditional astronomy. Right. So who actually
9:03
took it seriously? It took an amateur enthusiast
9:06
in Illinois named Groot Reber to actually push
9:09
the field forward. Oh, right. He reads about
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Jansky's work and just becomes completely obsessed.
9:14
Yeah. Reber decides that if the professionals
9:17
aren't going to look into this, he'll just do
9:18
it himself. So in 1937, he builds the world's
9:22
first purpose -designed radio telescope right
9:26
in his own backyard. In his backyard. That's
9:29
amazing. It was a nine -meter parabolic dish
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built entirely out of sheet metal and wood. And
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for years, Reber worked alone out there, meticulously
9:38
mapping the radio emission of the Milky Way.
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He was producing the very first real surveys
9:44
of the radio sky, long before any university
9:46
took it seriously. Exactly. But Reber's backyard
9:49
project quickly highlighted a massive physics
9:52
problem for anyone who wanted to follow in his
9:54
footsteps. Right, because if astronomers wanted
9:56
to actually see this new radio universe clearly,
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they couldn't just build slightly bigger dishes.
10:02
No, they ran headfirst into something called
10:04
the diffraction limit. Can you break that down
10:06
for us? Sure. Diffraction is a fundamental property
10:08
of waves. Whenever a wave passes through an opening
10:11
or bounces off a dish, it naturally spreads out
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and blurs. So the sharpness of your image, what
10:16
we call your resolution, depends entirely on
10:19
a really simple ratio. It's the size of your
10:21
telescope dish compared to the wavelength of
10:24
the light you're collecting. Okay, so with visible
10:26
light, the waves are totally microscopic. So
10:28
a tiny backyard optical telescope gets a perfectly
10:32
crisp image of, like, Jupiter. Right. But radio
10:36
waves are meters or even kilometers long. So
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to get that exact same crisp resolution using
10:41
radio waves, you can't use a normal telescope.
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What would you have to use? You would literally
10:46
have to build a single solid mechanical dish
10:49
the size of a city. Which is structurally impossible.
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It would just collapse under its own weight.
10:54
Exactly. So astronomers developed what I honestly
10:56
think is one of the most elegant workarounds
10:58
in modern science, which is called interferometry.
11:01
Okay. I have a way to visualize this. Imagine
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you're trying to hear a single person whispering
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on the far side of a massive crowded football
11:10
stadium. Right. Impossible. Building a single
11:13
100 -foot mechanical ear on one side of the stadium
11:16
to hear it isn't going to work. No, of course
11:18
not. But you could take thousands of normal human
11:22
ears, place them all throughout the bleachers,
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and wire them all together. Yes, perfect analogy.
11:29
If you electronically combine everything those
11:31
individual ears are hearing, you can digitally
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reconstruct the exact sound of that whisper.
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As if you had one giant ear the size of the entire
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stadium. That is exactly what interferometry
11:42
does with radio dishes. Astronomers build dozens
11:45
of smaller manageable antennas and spread them
11:48
across a huge landscape. And when they combine
11:51
the signals, they synthesize the resolving power
11:53
of a single dish as wide as the distance between
11:57
the furthest antennas. Wow. And that distance
11:59
is called the baseline. But they didn't just
12:01
stop at a few miles, right? They pushed this
12:04
to the absolute planetary limit with what they
12:06
call very long baseline interferometry or VLBI.
12:10
Oh, yeah. They link dishes on opposite sides
12:13
of a continent or even opposite sides of the
12:15
planet. But doing that requires terrifying precision.
12:18
You can't just wire them together with cables
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anymore when they're that far apart. Right. So
12:22
how do they actually sync the data if the dishes
12:25
are in completely different countries? They use
12:27
atomic clocks. Wait, real? Yeah. Every single
12:30
radio wave hitting a dish in Australia is timestamped
12:33
down to the microsecond. And the exact same waves
12:36
hitting a dish in Spain are also timestamped.
12:38
That is wild. Then they take hard drives full
12:41
of this data. physically fly them to a central
12:44
supercomputer, and align the peaks and troughs
12:47
of the waves based on those atomic timestamps.
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It's just digital magic. They're literally synthesizing
12:52
a virtual telescope the size of the Earth. They
12:55
are. To put that into perspective for you listening.
12:57
An Earth -sized telescope has the resolution
12:59
to stand in New York and clearly read the date
13:02
on a coin sitting in London. Exactly. And that
13:05
exact technique is how humanity captured the
13:08
very first silhouette image of a black hole just
13:11
a few years ago. Incredible. So armed with these
13:13
planet -spanning virtual telescopes, astronomers
13:16
were able to tune into one very specific foundational
13:19
frequency, the 21 -centimeter hydrogen line.
13:23
Right. Hydrogen is the most abundant element
13:26
in the universe. It's very simple, just a single
13:28
proton orbited by a single electron. But to understand
13:32
the 21 centimeter line, we actually have to look
13:35
at the quantum mechanics of that atom, don't
13:36
we? We do, but it's not too complicated. Both
13:40
the proton and the electron have a property called
13:42
spin. You can basically think of them as tiny
13:45
magnets. Okay, magnets, got it. Usually they
13:48
spin in the same direction, but very rarely the
13:51
electron will spontaneously flip its spin so
13:53
it's pointing in the opposite direction of the
13:55
proton. And when it makes that flip, it settles
13:57
into a slightly lower energy state, right? Right.
14:00
And to shed that leftover energy, it emits a
14:03
single radio wave that is exactly 21 centimeters
14:06
long. But for any single individual atom, this
14:10
flip is incredibly rare. Like an electron might
14:12
only do this once every 10 million years. That's
14:14
right. But space is vast and the sheer volume
14:17
of cold hydrogen gas floating between the stars
14:20
is just incomprehensible. So even if one atom
14:24
only flips every 10 million years, there are
14:26
so many trillions upon trillions of atoms that
14:29
at any given second, countless electrons are
14:32
flipping. Okay. It's like standing in a stadium
14:34
filled with a trillion people. And the rule is
14:37
each person is only allowed to clap their hands
14:39
once every 10 million years. You'd think the
14:42
stadium would be totally silent. But because
14:44
the crowd is so unimaginably huge, you don't
14:47
hear silence. You hear a constant, deafening
14:49
roar of applause. That is exactly what's happening.
14:53
That roar of applause translates to a perfectly
14:55
steady, detectable radio hum at exactly 21 centimeters.
15:00
And mapping that hum changed everything. It did.
15:03
By mapping it, astronomers were finally able
15:05
to trace the cold gas across the Milky Way, which
15:08
actually allowed them to map out our galaxy's
15:11
spiral arms from the inside. Which is so hard
15:14
to do, since we're stuck inside it. But the map
15:17
itself wasn't even the biggest discovery here.
15:19
The biggest discovery actually came from the
15:20
speed of the gas. Oh, absolutely. But how does
15:23
a radio hum tell us how fast a cloud of gas is
15:26
moving? It all comes down to the Doppler effect.
15:29
Think of an ambulance driving past you. As it
15:31
speeds toward you, the sound waves are compressed
15:34
so the pitch of the siren sounds higher. And
15:37
as it speeds away, the waves stretch out and
15:39
the pitch drops. The same thing happens with
15:41
light and radio waves. Exactly. We know the hydrogen
15:44
wave is exactly 21 centimeters. But if the gas
15:48
cloud is moving away from Earth, that wave gets
15:51
stretched out to maybe 21 .1 centimeters. And
15:55
if it's speeding toward us... it compresses to
15:57
20 .9 centimeters right so by measuring that
16:00
microscopic stretching and squishing astronomers
16:03
calculated the exact orbital speed of the gas
16:06
at the very outer edges of the milky way and
16:08
the results kind of broke our understanding of
16:10
physics didn't they they completely broke it
16:12
the gas was moving entirely too fast too fast
16:15
for what too fast for the amount of gravity holding
16:17
it in Based on all the stars and visible matter
16:19
we could see, there wasn't nearly enough gravity
16:21
to keep that fast moving gas tethered to the
16:24
galaxy. It should have just been flung out into
16:26
deep space. Exactly. The only way the math worked
16:28
out was if the galaxy was packed with an invisible
16:31
mass, mass that exerts a powerful gravitational
16:34
pull but doesn't emit any light, heat or radio
16:38
waves. Dark matter. Dark matter. The 21 centimeter
16:41
line provided some of the most undeniable, crucial
16:44
evidence that the vast majority of the universe
16:47
is. made of something we literally cannot see.
16:50
So radio astronomy revealed the invisible skeleton
16:52
of the galaxy. But it also unveiled some of the
16:55
most violent objects in the universe. Oh, definitely.
16:58
Because in 1967, a postgraduate student named
17:01
Jocelyn Bell noticed something really bizarre
17:04
in her data. Yeah, she found a remarkably regular
17:07
pulse of radio energy repeating roughly every
17:09
1 .3 seconds. Which is very fast. And the timing
17:12
was so flawless, so perfectly metronomic, that
17:15
it honestly defied any natural explanation they
17:17
had at the time. formerly nicknamed the signal
17:20
lgm1 which stood for little green men they did
17:23
and i have to admit If I was sitting in an observatory
17:26
in the 60s and saw a signal that perfect, my
17:30
mind would immediately jump to an engineered
17:31
alien beacon too. When she found that perfectly
17:34
repeating signal, how did astronomers eventually
17:37
rule out aliens? Oh, it was a genuine historical
17:40
mystery for a short time. They really had to
17:42
entertain the alien hypothesis. But as they scanned
17:45
the sky, they found more of these perfectly repeating
17:48
signals in completely different locations. Oh,
17:50
I see. So they realized they hadn't found aliens.
17:54
They had found pulsars. Which honestly might
17:56
be even wilder than aliens. What exactly is a
17:58
pulsar? A pulsar is a rapidly spinning neutron
18:02
star. When a massive star reaches the end of
18:05
its life, it explodes in a supernova. The outer
18:08
layers are blast away, but the core collapses
18:10
inward under its own gravity. And it collapses
18:13
so violently that the atoms are physically crushed
18:15
together. Electrons are forced into protons,
18:18
creating this hyper -dense sphere of pure neutrons
18:21
roughly the size of a small city. And the density
18:24
of that is just incomprehensible. Like, a single
18:27
teaspoon of material from a neutron star would
18:31
weigh... Billions of tons here on Earth. Exactly.
18:34
And because it shrank so dramatically, it spins
18:37
incredibly fast, much like an ice skater pulling
18:40
their arms in. That makes total sense. These
18:42
neutron stars possess magnetic field that are
18:45
millions of times stronger than Earth's. And
18:47
these fields channel fierce beams of radio emissions
18:50
straight out of the star's magnetic poles. It's
18:53
exactly like the beam of a lighthouse sweeping
18:55
across a dark ocean. That's a perfect analogy.
18:58
As the star spins, that beam sweeps through space.
19:01
And if Earth happens to be in the path of that
19:04
beam, our telescopes pick up a bright flash of
19:06
radio waves every single time it rotates past
19:08
us. And some of these, known as millisecond pulsars,
19:11
are spinning hundreds of times a second. Yes.
19:14
And their rotation is so stable over decades
19:17
that they rival the accuracy of our best atomic
19:19
clocks. And astronomers are using them as actual
19:22
galactic scale tools now, right? I've heard of
19:24
pulsar timing arrays. Yeah, pulsar timing arrays
19:27
are where scientists monitor a network of these
19:29
pulsars across the sky. What are they watching
19:31
for? They watch for microscopic delays in the
19:34
timing of those pulses. If a gravitational wave,
19:37
which is a literal ripple in the fabric of space
19:40
-time caused by a colliding supermassive black
19:42
holes washes through our galaxy, it momentarily
19:46
stretches and squeezes the space between Earth
19:48
and the pulsar. So by measuring a pulse arriving
19:51
a fraction of a nanosecond late, we can detect
19:54
the stretching of space itself. Exactly. That
19:56
is amazing. Pulsars are just these ultimate predictable
19:59
cosmic metronomes. But recently we found something
20:03
that is the exact opposite of that. Fast radio
20:05
bursts or FRBs. Right. FRBs are incredibly fleeting
20:09
and chaotic. They were first discovered in archival
20:12
data back in 2007. What are they exactly? An
20:15
FRB is a flash of radio energy that lasts just
20:17
a few milliseconds. But in that tiny fraction
20:20
of a second, it releases as much energy as our
20:22
sun produces in an entire day. And most of them
20:25
are arriving from far beyond our own galaxy,
20:27
right? What kind of cataclysmic event can release
20:30
that much energy in a millisecond? Well, it's
20:32
one of the most active debates in astrophysics
20:34
right now. But a major breakthrough happened
20:37
in 2020. Astronomers managed to catch an FRB
20:40
originating from inside our own Milky Way, and
20:43
they trace it to a magnetar. A magnetar. That's
20:46
a specific type of neutron star, right? Yes,
20:49
a neutron star with a magnetic field so intense
20:52
it basically strains the limits of physics. How
20:55
intense are we talking? The magnetic field is
20:57
so strong that if one were located halfway to
21:00
the moon, it would wipe the magnetic stripes
21:02
off every single credit card on Earth. Oh, my
21:05
God. Yeah. And when that magnetic field snaps
21:08
and reconnects, it releases a devastating blast
21:11
of radio energy. And Australia has actually been
21:14
at the forefront of this FRB research, specifically
21:17
the Parks Observatory in New South Wales. Oh,
21:19
definitely. This is the massive dish that famously
21:22
relayed the live TV pictures of the Apollo 11
21:24
moon landing. Right. And it was recently given
21:27
the name Murrayang, a word from the local Wariria
21:30
people meaning sky world. Which is a beautiful
21:32
name. Murrayang has discovered roughly half of
21:34
all known pulsars. But it was also the site of
21:37
a very different, highly amusing mystery. Regarding
21:41
radio bursts, wasn't it? It was. For years, the
21:45
astronomers there were baffled by these strange
21:47
fleeting signals they called peritons. And they
21:50
spent years trying to track down what exotic
21:53
cosmic phenomenon was causing these peritons.
21:56
I mean, what did it turn out to be? It turned
21:58
out it wasn't a magnetar or... A black hole.
22:02
It was the staff kitchen. The kitchen. It was
22:04
the microwave oven. Oh, my gosh. Yeah. If a hungry
22:07
researcher opened the microwave door just a split
22:09
second before the timer finished its cycle, the
22:12
magnetron inside released a tiny microscopic
22:15
blip of radio interference. And the telescope
22:18
picked it up. Yes. The massive Moriang telescope
22:20
was so sensitive it picked up that tiny blip
22:23
and recorded it as an anomaly from space. It's
22:26
such a hilarious story, but it perfectly highlights
22:28
the biggest existential threat. to radio astronomy
22:31
today, which is human technology. Absolutely.
22:34
The signals these telescopes are hunting for
22:36
are billions of times weaker than a standard
22:38
mobile phone signal. Which is why the future
22:41
of the field requires absolute, uncompromising
22:44
isolation. Which brings us to the deep Australian
22:48
outback. Right. Out in the remote Murchison region
22:51
of Western Australia, on Wajari Yamaji country.
22:55
An international coalition is building the Square
22:57
Kilometer Array, or SKA. And the site is formally
23:01
named Inyarimana Ilgari Bundara, meaning sharing
23:05
sky and stars. Yes. It's going to be this vast
23:08
network of thousands of antennas acting as an
23:11
enormous low -frequency interferometer. And right
23:14
next to it is a companion instrument that's already
23:16
operating called ASCAP. Why is ASCAP so special?
23:20
Well, ASCAP is brilliant because it uses phased
23:22
array receivers. Instead of just having one receiver
23:25
at the focal point of the dish, it has dozens.
23:27
Oh, okay. And the clever part is how they use
23:29
them. Yeah. Because they don't have to physically
23:30
move the massive dish to look at different parts
23:33
of the sky, right? Right. By applying tiny microsecond
23:36
electronic delays to the signals hitting those
23:39
different receivers, computers can digitally
23:41
steer the focus. So they can look in multiple
23:43
directions at once, completely electronically.
23:46
Exactly. It gives them a massive field of view,
23:48
making it the perfect trap for catching those
23:50
random, unpredictable, fast radio bursts we talked
23:53
about. But all of this advanced technology is
23:55
entirely dependent on the Murchison region being
23:58
a legally enforced radio quiet zone. It has to
24:01
be. Just like optical telescopes need dark skies
24:04
free of city lights, radio telescopes need skies
24:07
free of radio frequency interference, or RFI.
24:10
And we are totally surrounded by RFI in our normal
24:13
lives. Oh, completely. mobile phones, Wi -Fi
24:16
routers, the Bluetooth in your car, even spark
24:18
plugs, as we mentioned earlier, out in the quiet
24:21
zone, all of that everyday technology is strictly
24:23
restricted. The silence is protected by law.
24:27
It really reframes how you think about pollution.
24:30
The idea of radio light pollution. It's a real
24:32
issue. These cosmic whispers have traveled for
24:35
billions of years across the void, and they're
24:37
so incredibly fragile that someone's stray cell
24:40
phone signal out in the desert could literally
24:42
drown out the sound of a black hole merging.
24:45
Protecting the silence is just as important as
24:47
building the telescopes themselves. If we don't
24:50
preserve these quiet zones, we essentially blind
24:53
ourselves to half the universe. So the next time
24:55
you find yourself somewhere properly dark and
24:58
quiet. Far from the city lights. Take a moment
25:01
to just look up. Remember that the silent, twinkling
25:04
sky you are seeing with your eyes is only ever
25:06
half the story. Barely even half. Right. Layered
25:10
invisibly over the top of it is this chaotic,
25:12
noisy sky full of static, sweeping lighthouse
25:16
pulsars and the hidden skeletons of galaxies.
25:19
And we have only known how to hear it for less
25:21
than a century. We have only just begun to tune
25:23
the dial. Thank you so much for joining us on
25:25
this deep dive into the invisible sky. But before
25:28
you go, I want to leave you with one completely
25:30
new thought to ponder today. What's that? Think
25:32
about this. If our human eyes evolved to miss
25:35
almost the entire electromagnetic spectrum, and
25:38
it took a literal telephone engineering accident
25:40
just 90 years ago to finally hear the radio universe,
25:44
what other fundamental forces, waves, or signals
25:47
are washing over you right this very second,
25:49
completely undetected, just waiting for the next
25:51
accidental backyard invention to finally tune
25:53
them in? Keep listening to The Static.