Avery Broderick on a black hole breakthrough from the EHT

On May 12, 2022, the global Event Horizon Telescope (EHT) collaboration unveiled the landmark first image of the black hole at the heart of our own Milky Way galaxy, called Sagittarius A* (or Sgr A*). On this special episode of Conversations at the Perimeter, Lauren and Colin talk with astrophysicist Avery Broderick about the significance of this discovery. He explains how the EHT collaboration created an “Earth-sized telescope” – a network of eight radio telescopes on five continents, all focussed on a single spot on the night sky: the heart of the Milky Way, 27,000 light-years from Earth. Broderick holds the Delaney Family John Archibald Wheeler Chair at Perimeter, and is an associate faculty member jointly appointed to Perimeter and the University of Waterloo. He also leads the EHT Initiative at Perimeter Institute, which is one of the 13 partner organizations in the EHT. Although his childhood dream of voyaging through the universe on the Starship Enterprise remains out of reach, Broderick says hunting black holes (or "fire donuts," as he playfully calls them) is the next-best thing. View the episode transcript here.

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Conversations at the Perimeter is co-hosted by Perimeter Teaching Faculty member Lauren Hayward and journalist-turned-science communicator Colin Hunter. In each episode, they chat with a guest scientist about their research, their motivations, the challenges they encounter, and the drive that keeps them searching for answers.

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Episode Transcript

(00:00):
(twinkly music)
- Hi everyone and welcometo this very special episode
of "Conversations at the Perimeter".
- Today we're talking to Avery Broderick.
He's a researcher hereat Perimeter Institute
and at the University of Waterloo
and he's one of the world'sleading experts on black holes.

(00:22):
He's part of the Event HorizonTelescope Collaboration
who've just come outwith a big announcement.
- We don't want to give any spoilers here.
So let's move into ourconversation with Avery.
- Avery, thank you so much for being here.
- My pleasure.
- We're so excited to talk to you.
Personally I think that black holes

(00:44):
are the most fascinating,amazing things in the universe
and you're my favorite personto explain black holes.
You're the source of all ofmy knowledge of black holes.
So I'm hoping you can tellus the news that has come out
about black holes and theEvent Horizon Telescope
that you're involved with.
What's new, what'shappening with black holes?
- First Colin let me say,
you're my favorite personin the universe now too

(01:06):
because you love the same thing I love.
I shouldn't say that,
because of course my favorite people
are my family that support usand make this all possible.
You're my favorite PR person.
- I'll take it.- Favorite podcaster.
- All right.
- So.- What?
- Sorry Lauren.- Tied for first.
Tied for favorite podcaster.- Yes, yes.
Well she could be favorite in a minute,
depends on how she starts her question.
- All right.- The news now
is that Horizon Telescope

(01:28):
has now released the imageof the second black hole
that it has observed.
And this black hole is the one
at the center of our very own galaxy.
All right, so this is near and dear to us
and it looks very muchlike the first image
that we released three years ago.
It's a fire donut on the sky okay?
But it's an important and Ithink striking confirmation

(01:51):
that the first image was notunique, it was not special.
We didn't get lucky.
That in fact imaging the event horizons
of black holes is a going concern.
We now have done it with two objects
and it looks the way that Einstein
and many others afterwards predicted.
- And you mentioned thefirst one a few years ago.
Can you tell us about that one

(02:11):
and you said they look similar
but they also have differences,significant differences in.
- Absolutely.
Yeah so what we released three years ago
was an image of the six anda half billion solar mass.
So it's not just the mass of the sun
which dwarves of course themass of any terrestrial object
but of the sun and six and a half billion

(02:31):
of its closet friends.
Almost the mass of a galaxy.
All collected into one point in space
out in the giant ellipticalgalaxy, Messier 87.
54 million light years away right?
So it's an enormous distance away
and the photons that left M87left, departed the black hole,

(02:53):
the dinosaurs had just gone extinct.
Mammals had not yetbecome ascendant right?
- That's cool.- It's an incredible,
incredible distance.
Mind-boggling scales.
The one that we just saw today,
the one that we just released today.
It came from the same observation route
but it's the black hole atthe center of our galaxy.
Okay, so it's still a long distance away.

(03:14):
If you wanted to get intoyour car and drive there,
it would take you about as long.
Essentially an infinite amount of time.
I don't know what gasmileage your car gets
but it's, I guess unless you're Elon Musk.
- If your car went the speedof light just to clarify
you could get there inhow many million years?
- It would take 24,000.- 24,000 that's a lot, okay.
- 24,000 years.
So that means that thelight that left Sag A*,

(03:37):
that's the name we give the black hole
at the center of our galaxy.
Left in the late Stone Age.
Not only were there humans
but they were well on their wayto becoming what we are now.
So it really drives home howmuch closer this new beast is.
It's closer but it's also1500 times less massive.
More typical, not thisreally extreme kind of thing

(03:57):
that M87 was.
It's our black hole.
So I think a lot of usfeel an affinity for it
and it means that it changes.
M87 is the stately oldlion, just sitting there.
Letting take its photograph every night.
Sag A* is the puppy
that's constantly movingaround, wagging its tail,
won't stay still.

(04:18):
On minutes, maybe hours time scale.
Because that's acompletely different face.
And that's a massive difference right?
Different time scale thatit takes to image it.
Different time scale thatthings are changing on.
- How do you do this?
How do we image black holes?
- With great difficulty
and with a global groupof extraordinary people
who all come togetherfor this one purpose.

(04:39):
The imaging of M87, the imaging of Sag A*
begins with telescopes atfar corners of the earth.
Each planning and executingcoordinated observing campaigns.
Collecting these subtlephotons from the universe.
Recording them on literallytons of hard drives.
That then gets shippedback to a central facility
where we try to piecetogether what is effectively

(05:03):
an earth-sized telescope.
So then once we have theselittle bits of information
pieced together in anearth-sized telescope,
then we can complete theprocess of forming an image
in a large supercomputer.
And that involves effectivelyimplementing something
like an inverse Fourier transformer.
Unmixing little bits of information
from each of these around the globe.
- So it's some difficulty.

(05:24):
- A little bit, yes.
Yeah yeah, yeah.
- And it's a really involved procedure
but at the end of the dayyou're getting this one image
that we can look at.
As you said, it looked like a fire donut.
What are we seeing whenwe look at that image?
- The fire in the fire donutis the luminous hot plasma
that has rushed headlongtowards an inexorable fate
crossing the event horizon.

(05:45):
Out of the visible universe.
Black holes are a nice place to look
but if you linger toolong, you're in trouble
and that plasma is lingering too long.
But by virtue of having fallen down
deep into the potential well
presented by the black hole
that has heated up toenormous temperatures,
billions of degrees
and that's producing the fire that we see.
That's what we would callsynchrotron emission.

(06:08):
It's an emission mechanism that happens
when you have very energetic electrons,
very hot electrons zippingaround magnetic fields.
The hole in the donut,
which is of course the defining feature.
That's the black hole.
That's the gravitational bending of light
around the central black hole.
It leaves behind a shadow.
And that's the defining feature.
We talk about the Event Horizon Telescope.
That's what we were built to observe.

(06:28):
- I always thought blackholes were by definition,
impossible to see,impossible to photograph
and the idea that theicing around the donut
and my initial perception would be,
well everything falls inand you can't see anything.
So what are we seeing light
that has just barely escapedfrom this pit of gravity?
- Yeah, so the darkness of black holes.

(06:49):
That's an isolated black hole statement.
Right, black holes aredefinitely the perfect prison.
Nothing escapes, even light.
But black holes plus the stuff,
that's the icing right?
That they are the most luminousobjects in the universe.
What we're seeing isemitted far enough out
that it's not quite so dire.
A non-trivial fraction of the light

(07:10):
is captured and absorbed by the black hole
depending on where exactlywe're talking about.
It can be as high as 50%, maybe less.
So I don't know, what kind of odds
do you want to give our photon?
- Not great.- Not great, yeah, yeah.
So yeah, it's an extreme environment
but it's not right up against the horizon.
- Yeah, I want to goback to this word horizon
'cause you've said it a few times

(07:30):
and it's even in the name ofthe Event Horizon Telescope.
What's the event horizon andwhere is that on the image?
- The event horizon is mathematically
that point of no return.
The surface in space thatseparates those things
that can reach out to infinityand those things that can't.
A good definition might be event horizon
is that line you crosswhen people stop responding

(07:52):
to your tweets.
That puts it in a very contemporary frame.
In the image, the reasonwhy we see a dark shadow
is because light can't traversethrough the black hole.
The light that tries totraverse through the black hole
would cross that event horizon.
Then that's captured forevermore
and that's what leaves this deficit
that you can see from any vantage point.

(08:15):
It's kind of a funny idea
that no matter whatdirection you're looking
at the black hole at,
it casts the same shadowon the surrounding material
and it's because the light can't propagate
through this event horizonand come back to it.
So that we shadow we seeis literally the image
of the event horizon.
Or the absence of image from
the event horizon.- Right.
- I remember one of the firsttimes I ever spoke to you,

(08:35):
this was about eight years ago.
You said, "You knowwe're working on getting
"the first image of a black hole
"and mark my words, when wedo, it'll be on the front page
"of the New York Times, above the fold."
And then you announcedit and the next day,
I remember I picked you up at the airport
and I looked at the newsstandand there's the black hole
on the front page of the NewYork Times above the fold
and I thought, "Well he gotthat prediction correct."
And if the predictions of theblack hole itself are correct,

(08:57):
why do you think there'ssuch a public fascination?
It's, New York Times abovethe fold is prime real estate
for an object that's impossibly far away
for us to ever experience.
- Now this is one of the great joys
of working on black holes.
I think it connects withpeople on a deep level.
I think most people,
they may not have amathematically exact concept

(09:18):
of what a black hole is.
But black holes have penetrated
the public consciousnessso well that most people
have a reasonable conceptual idea,
that perfect prison fromwhich nothing escapes.
Maybe they see them in movies,black holes don't suck.
But beyond that, youknow they're not Hoovers
sucking up the universe.
But the idea of a thing that you go into
and you don't come out.

(09:38):
It also ends up being a useful reference,
many things that people experience right?
I mean there's a real mystery.
What happens on the otherside of that event horizon
and how would you know?
You can't send an undergraduateacross the event horizon
and then report back to you right?
They cross the eventhorizon and it's a mystery.
That's an obvious metaphor

(09:58):
for a lot of things.- There's also ethical reasons
why you shouldn't send anundergraduate to the black hole.
- Undoubtedly yes, yes, yes and practical.
It's very, very expensive.
You would at least senda graduate student.
It's a metaphor for changes in life
that you can't see the other side of.
So people in a visceralsense connect with it
and it's visual.
You know a large part of your brain
is focused on visual processing.

(10:18):
So this is a profound science result
that talks about thesekind of extreme objects
that people already kind of get.
And it's presented to them in a format
that they can easily absorb.
I think that's why this ends up
being a really excitingprospect for public engagement.
- Yeah.- And as you said,
it relies on a global collaboration.
Can you talk a little bitabout that collaboration?

(10:39):
How many people, where thedifferent telescopes are located.
- Maybe your role in that collaboration,
which piece of the puzzle are you?
- Right so the collaborationis more than 400 people.
They are on six of the seven continents.
We managed to get ontoAntarctica before Australia.
There's not enough tallmountains in Australia.

(10:59):
We'll have to find a solution for that.
These are people who range from engineers
who design and build hardware,put steel on the ground.
All the way to people like me, theorists
who try to make sense of what we see.
So my role in all of thishas been trying to determine
what does it mean that wesee this particular brand

(11:22):
of fire donut.
You know is it a French cruller?
Is it a Boston cream?
And what does that mean for black holes
and how they impact the galaxy?
The telescopes are at thehighest stria sites on earth.
It's absolutely critical
because we are looking atmillimeter wavelength photons.
These are about 10 timessmaller than the size of photons

(11:43):
that are bouncing around your microwaves.
A few times smaller than your microwaves.
The reason why we use microwave ovens
is because those photonsare absorbed well by water.
If you put a steak in the microwave
and it comes out even lookinglike you boiled a steak,
that's 'cause that's what you did.
You heated up all the water,
then you cooked thesteak with the hot water
inside the steak.

(12:04):
So that's slightly tragicbecause we have these photons
that came from the late Stone Age,
from the center of our galaxy
or just after the end of the dinosaurs.
From M87 they've traversedthe universe to come to us
and in that last moment of their journey,
they slam into our upper atmosphere
and get absorbed by water right?
I mean it's sort of abrutal Game of Thrones type.

(12:25):
- That long journey.- Game of Thrones for photons.
- And then just shy of reaching us, they.
- No payoff.
So we try to help those photons
by getting above as muchof the water as we can.
So you have to be inthose highest locations
and try to choose the placesthat don't have lots of water.
So South Pole's a good example.
First it's pretty high and second,
the water has precipitatedout, it's all frozen out.
Chile, the Atacama Plain.

(12:47):
Alma's built on a high plateau,
that's in the middle of a desert.
Montecito in Hawaii
is a mountain that protrudes up very high
and it's in a very stablethermal environment.
So all of these places high and dry
help us get to these photonsbefore the water vapor does.
- THE EHT has beendescribed by you and others
as an earth-sized telescope.

(13:07):
Can you explain what you mean by that?
- All astronomical observations
must fundamentally contendwith the wave nature of light.
It's unfortunately not an option.
Light's a wave and that means
that when we see small structures,
they get blurred out bysomething called diffraction.
You experience diffractionand as I get older,

(13:29):
I might see it a littleworse than I did before
but you experience diffractionevery time you drive at night
and you look out into the distance
and you see the streetlights.
You'll notice they alllook like little stars,
not stars in the sky.
Multipointed star bursts.- Star bursts.
- Yes, thank you.
And if you look closely you'll notice

(13:49):
that every street lightlooks like the same star
and if you turn your head,the star moves with your head.
It's always oriented the same way
and the because the staris not in the light,
it's in your eye.
You're looking at diffractionspikes through your pupil.
You see this in movies whenyou see the diffraction spikes
on the camera.
You can tell how many sidestheir pupil on the camera has.

(14:11):
Or how many sides they thoughtthe pupil on the camera
would have when they doit all in post processing
and add lens flare and things.
- The JJ Abrams shot.
- That's right.
And so the same thing happensto astronomical instruments.
Your ability to resolvesomething goes down
as your telescope gets bigger.
Let me turn that around.
The smallest thing youresolve gets smaller
as your telescope gets bigger.

(14:32):
- Okay.- Bigger telescope,
you can see smaller objects.
At millimeter wavelengthswhich is where microwaves
that the EHT observes.
We really do need atelescope that is the size
of the planet.
The 10,000 kilometer diameter telescope.
That's an unpopular thing tobuild in people's backyards.
They somehow object ifyou completely cover
their entire yard in shade.

(14:54):
The solution is that it turns out
you don't need a whole telescope.
You just need to fill in enough of it
to spread out acrossthat 10,000 kilometers
and the Event Horizon Telescope uses
this very clever techniquewhere we have telescopes
that are spaced around the world
and they're in each filling in.
In fact, it's each pairof them are filling in
a little point on this mirror.

(15:16):
The strategy is one, moretelescopes is better.
We get more points on themirror and two, patience
as the earth rotates underneath the sky
and as the earth rotates,
those telescopes areat different locations
and they're filling in adifferent part of the mirror.
So when we say we havean earth-sized telescope,
we mean that very literally.
So we really do effectivelyconstruct a sparsely-sampled

(15:40):
but nevertheless,earth-sized primary mirror
but it's also a computational telescope
because that process has to be completed
in large computers after the fact
which is effectivelypropagating the photons
from the mirror where normallyyou would have the mirror.
You've flecked your photons off the mirror
up to your primary focus
and then you'd make your image there.

(16:00):
We reflect, we'll redetectthe photons on the mirror
and then on a computer and say,
"Well, this photon would have done this
"up to our primary focus."
And then we make images.
- So all of these telescopes that existed
for other purposes,
they were built forother astronomical uses,
you've sort of hijackedisn't the right word.
Piggybacked?
Capitalized.

(16:21):
- Borrowed.- What's the good word?
Borrowed, made the most of.- Leverage
- Leverage, there's the word
I was working for.- Leverage, leverage yeah.
- So these telescopesweren't built themselves
for black hole hunting is that right?
- That's right.
In fact one of the largesttelescopes in the world,
if not the largest had AtacamaLarge Millimeter Array.
It's this telescope in the Chilean desert.

(16:41):
Canada is a partner.
It's so big that it couldn'tbe made with a single region.
So you got Europe, it's got North America
and it's got the Asian partners.
And they all came togetherand they built this
one enormous radio telescope.
Two billion dollars.
This was not the thing they built it for.
They built it for a whole host of things.
Finding birth places of planets.

(17:03):
The disks around youngstars where planets form.
One of the first images it produced
shows these beautiful rings
where you can see the planetsare forming inside of the gas
and dust disk around a young star.
Understanding how stars form.
Understanding the formationand evolution of galaxies
and any number of other things.
I'm shortchanging Alma by a long shot.
Then there's a wholebunch of other telescopes

(17:24):
that were built for very similar purposes.
None of which by themselves
could even hope to do theexperiment that we're doing.
But what the Event HorizonTelescope really did
was provide the secret sauceor the clever application
that connects them all.
And it's a good exampleof how you can have
a lot of excellent piecesbut until you assemble them,

(17:44):
maybe there's something you're missing.
All right, the EHT is really,
allows these telescopestogether to be far more
than the sum of their parts.
- How did you even conceive,
you or your colleagues think of.
Maybe if we connect these telescopes,
we could resolve this mysterious object.
Where did this idea comefrom, to built the EHT?
- To be fair, this technique,radio interferometry

(18:05):
is a venerable technique.
I mentioned Alma, I went onand on about Alma a moment ago.
It actually uses radio interferometry.
It's 64 individual dishesthat all connect up
to form one effective telescope
that's maybe 10 kilometers across.
100 kilometers across sometime.
They move the dishes around.
The idea of using telescopes

(18:25):
separated by earth-sizeddistances also is not new.
People have been doing thatfor almost half a century.
The Very Long Baseline Array,
so the technique is verylong baseline interferometry
and there's a dedicatedarray that does this.
Very Long Baseline Arrayat much longer wavelengths.
Seven millimeters is really pushing it

(18:47):
and then they go all the wayout to a meter wavelength.
So the VLBA has beendoing this for 30 years.
What's new in the EHT ispushing that technique
down to one mil.
It is expensive to make the earth bigger.
You can do it at the priceof launching rockets.
It's difficult otherwiseto make the earth bigger
but if you want to improve the resolution,
the other thing you can do is observe

(19:08):
at shorter and shorter wavelengths.
Higher and higher frequencies.
Bluer and bluer color andthe Event Horizon Telescope
really is the cleverelement of figuring out
how to make that techniquewhich is very challenging,
very significanttolerances at each station,
work on this heterogeneousarray of telescopes
that were otherwise already built
to do the millimeter science,

(19:28):
in part for the reasons whyI talked about microwaves.
Because looking at water is interesting
and it's not just water thatshows up in a microwave right?
- And these are features ofthe technique in general.
Did you have to modify orimprove any of the techniques
when you went from studyingM87 to studying Sag A*?
- The observationalside of it is the same.

(19:48):
In fact it's the same observing route.
Detecting those subtle radio photons,
that was effectively identical.
But because Sag A* is that frenetic puppy
and constantly changing,
that means that if we are patient
as we have to be to make an image
'cause we do have to fill in that mirror.
Remember that mirror isjust a couple points.

(20:09):
I mean you can imaginewhat it would be like
trying to get ready in themorning and all you have
are 15 points on your mirror.
Maybe 15 little dime-sized pieces.
Some of us might be able todo that but most of us won't.
The patience part fills that in.
Is absolutely critical and that's the part
that is a real problem for Sag A*
because as we are patient,Sag A*'s changing.

(20:29):
So it's really like we'releaving the shutter open,
trying to get that photo in dim light
and the puppy is not standing still.
In fact we're chasing it around.
The M87 required a whole new set of tools
to operate in a challengingdata environment.
The Event Horizon Telescope,as wonderful as it is
is still just barely capableof doing what we ask.

(20:52):
I mean it's really agroundbreaking instrument
which also means that you're the first
to find all the difficulties.
All the problems.
We don't have enough telescopes,
we always want more telescopes.
We don't have enoughpieces of that mirror,
we always want more.
There are some calibration challenges
that we hadn't anticipatedthat we had to overcome.
We had to rewrite most ofthe data processing software.

(21:14):
There are packages thatpeople use for the VLBA
or for these other instrumentsand they just did not work
for EHT.
But then on top of that
we had to relax this patience assumption.
We could just stare it,leave the shutter open
and make a picture.
And that required I think a revolution
in how we think about makingthese sorts of pictures.

(21:35):
That's what took us the three years.
We had to develop theanalysis techniques necessary
to allow us to be patient.
- These images that you come up with,
they take years of effortfrom many different people.
How do you choose which blackhole you're gonna focus on?
What factors do you consider?
- Unfortunately that's easy.

(21:57):
- Sounds like the one easy thing.
So far.- Yeah, yeah.
You observe the black holes you have,
not the black holes you wish you had.
As this groundbreaking experiment
and being confined toearth-sized baselines,
earth-sized mirrors,there's only two black holes
that exhibit a shadowthat we could resolve

(22:17):
that we are aware of.
And those are the black holes in M87
and the black hole atthe center of our galaxy.
The one at the center of ourgalaxy because it's so close.
It's very typical in manyways but it's right next door.
And the one in M87because it's much further
but it's also much largerand those two, that's it.
Then after that, the nextone is three times smaller.

(22:40):
So just barely on the cusp.
Of course we do look at other objects.
There's a lot of interestingscience to be done.
To be looking at mostly accreting,
it turns out accreting black holes
but those are the only two horizon,
what we call horizon science targets.
Targets where we canresolve the fire donut,
resolve the shadow.
- I have to ask you about the fire donut.
Why you're calling

(23:00):
it a fire donut.- Yeah, yep.
One of the members of the EHT,
just before the firstannouncement put our M87 picture
into a Google image search.
Just to find out what Googlethought this might look like.
I think actually therewere some predictions,
that's not the fun ones though.
The fun one is they came up with fire,
rings of fire and donuts.
Also because it's a little bit fuzzy.

(23:22):
I know we have this picture of very sharp,
ring-like structures from these beautiful
and numerical simulationsthat run on supercomputers.
But we're just pushing the envelope,
we're just at the boundary.
The resolution we have is what we show
and that kind of smears it out into this.
Looks kind of like a French cruller.
- You said to us the other day though
that these two blackholes that you have now
are kind of like an odd couple

(23:42):
and if you had to choose just two,
there are two pretty good black holes
to have at your disposal now.
Can you explain why that is?
- There's the movers andshakers in the universe
and then there's everybody else.
Black holes are theengines of the universe.
Pumping out huge amounts of energy
but that's only a subset.
M87 is one of these very,

(24:03):
certainly historicallypowerful black holes.
It sits at an enormous galaxy,
in an enormous galaxy cluster.
It's thousands of galaxiesall orbiting each other.
It's not just that it sitsin a galaxy that's 100 times
more massive than our own
and it's down at thecenter of all of that.
Benefiting from all thatcommotion, driving gas down to it.
And while these days it's onsomething of A*vation diet,

(24:26):
certainly historically it wasn't.
That's how it got to be sixand a half billion times
the mass of the sun.
And it powers a powerful outflow.
Powers what we call a jet.
These are light-speed emanation.
Right, remember blackhole's perfect prison.
This is exactly the oppositeof what you would expect.
Stuff going out, not in.
And that stuff is being launched
right near the event horizon

(24:48):
and we think we understandsomething about how that work.
One of the goals of the EHTis really to nail that down.
So that's M87.
Launching these counterintuitive,
paradoxical light speed outflows,
center of all the commotion.
The one at the center of our galaxy
is the black hole next door.
It's really this typicalaverage black hole.

(25:08):
Our galaxy is kind of atypical average galaxy.
It's ours, so we like it.
But it's not terribly unique.
Out of four million solar masses,
our black hole is reallysimilar to all the other ones.
We only see it becausewe're so close to it.
It's on starvation diet andwere it a couple galaxies away
we would not be able to see it.

(25:29):
So it is as differentas you could imagine,
one of these enormous behemoths,
these super massive monsters
at the centers of galaxies it could be.
We have one power jet, it's enormous.
At the center of all the commotion
and then we have anotherone that's kind of typical
of everything else.
Not really growing very much,not feasting on very much gas.

(25:50):
Hardly observable, almost shy.
And it is the comparison then
that allows you to ask questions
like why is our black holelittle and that one big?
You know I'm not complaining right?
I don't want to live next to M87,
that would probably be dangerous.
What makes a black hole producethose light speed outflow?
What allows a blackhole to grow very fast?
What determines how brightthey are, how big they are?

(26:12):
- You've said, these are your words.
"There is a monster, asuper massive fire donut
"behaving like an unrulypuppy in our neighborhood."
Should we be scared, thisall sounds very scary.
- It's the astronomical neighborhood.
- Not right next door.
- Not right next door.
There's 24,000 light years
is a comfortable distance for now.
Remember black holes don't suck.

(26:33):
It's a great line for a sixth grade class.
The black hole at thecenter of our galaxy,
even at four milliontimes the mass of the sun
is only massive enough torule the gravity in its area.
Rule the dynamics andmaterial in its area.
Where a distance that's kind of typical
is the distance betweenstars where we are.
Now it has almost no moreauthority than the sun.
The sun is ruling the areaaround in our vicinity

(26:56):
of about that distance as well.
Now there's a lot more stuff there
so it's a little bit more impressive.
It has a larger retinueof more interesting things
but nevertheless it's relatively small.
Because the mass of thegalaxy is 10 billion times
that of the sun.
At four million with an M.
So 10 billion with a B,that's still a tiny fraction
of the galaxy which ispart of the magic trick.
How do black holes achievesuch enormous energy output

(27:18):
while being such a tinyfraction of the mass
of their host galaxy?
It's not gonna suck us up.
We're not gonna fall into it.
At least not in any time scale
that is even astronomically conceivable.
Long before that the sun will have grown
into a supergiant, envelop the earth.
Had gone out.- Oh great.
What a relief.- Yeah, yeah.
I mean like there's other things.
I'm not saying don't be worried,I'm just saying that's not.

(27:40):
But that doesn't mean that it's safe.
That's because
if it ever decides to gooff the starvation diet,
it can suddenly start producing
a lot of high energy emission.
A lot of x-rays,
a lot of ultravioletand a lot of gamma rays
and we know that a millionyears ago it was doing that.
There are these giant bubbles of hot stuff
above and below the planeof the Milky Way Galaxy

(28:03):
and it's believed that that is caused by
a episode of energetic behavior.
An episode of rapid accretionwhich suddenly produced
a lot of energy, producedjets like we see in M87.
Those light speed outflows.
- But we haven't seen in Sag A*?
Not any evidence inthe past million years.
In fact everything you seelooks like the luminosity

(28:24):
is dropping exponentially,dropping like a rock.
So now is the time to do this.
Million years from now, it might not be.
If it ever did thatagain, you know who knows?
We might all get irradiated.
You know, living next toan active galactic nucleus
is a little danger.
- You did say, you gave usan analogy the other day
of it's like living in the plain
next to a cosmic volcano.
It's dormant.- Yeah yeah yeah.

(28:44):
- But it may not always stay dormant.
- That's right, it mightbe beautiful at night
as long as it's not erupting.
- You make these nice analogies
to the type of diet thatthe black hole is on.
Whether it's starving or feasting.
Does this effect howdifficult it is to measure it?
- Yes, there's a sweet spotbetween starved and feasting
that we have to hit.
If it's feasting, it'sbright and that sounds good.

(29:06):
It's easier to see bright objects.
I mean these things are,these things are so dim
astronomers have a special unit.
Because it just gets really cumbersome
to carry around 10 to theminus 26 all the time.
It doesn't matter whatunit you're talking about.
It's 10 to the minus 26 something.
So it's 10 to the minus 26watts per second per Hertz.
We all used to havehundred watt light bulb.

(29:27):
Now we all have 15 watt.
10 to the minus 26 watt,
that's what astronomers are measuring,
it's really incredible.
And that's a bright source.
We call that a Jansky.
A Jansky source is a pretty rare source.
Sag A* is three Janskys,two and a half Janskys.
If we're rapidly creating,that'd be brighter,
it's easier to see.
On the other hand, at some point,

(29:48):
you know what we mean by rapid accretion
is that gas is rushing headlongdown towards the black hole
and more accretion means more gas.
You put too much gas, it becomes opaque
and then you can't see the shadow.
You know the big bright ball
at the center of the galaxy telescope.
The Event Horizon Telescope,we have a sweet spot.
It has to be accreting enough.
It has to be feastingenough that it's bright

(30:10):
and there are some galaxies that aren't.
M31, the Andromeda Galaxy.
All right, so you can seethat in the night sky.
The black hole at the centerof that one is a little too dim
and then on the flip side itcan't be feasting too much.
It has to be starving a little bit
or else we won't beable to see through the,
the material around itto get that horizon.
- Is there a spot on the night sky
where we could go out and look and say,

(30:30):
"Sagittarius A* is roughly there
"in the Sagittarius constellation."?
- Yeah, that's why it'sSagittarius A*, that's right.
So the center of our galaxy is located
in the constellation Sagittarius.
It's a teapot.
From the northern hemisphere,
you're really right onthe, right on the limb.
I've never been able to,
actually in my backyard to see it.

(30:51):
Because the light pollution and trees
and so it's always beena sore spot for me.
At some point I'm gonna getinto the southern hemisphere.
The only time that I wasin the southern hemisphere,
I was in Australia andthey had brush fires.
But you couldn't see anything.
- Yeah.- I was really bummed
and I'm a theorist so I didn'teven I was at the wrong.
I asked some of my observing colleagues.

(31:13):
Okay, so where would I have looked?
They kind of looked up at the sky
and they thought for asecond and they said,
"Well, at around noon look at the sun."
That was also the wrong time of year.
So that wasn't gonna happen.
- Sounds like bad advice.- Yeah, yeah.
- The high noon, stare at the sun.
- Yeah exactly.
It's in the constellation Sagittarius
and this is where the name comes from.

(31:34):
Right, so the brightestradio source in Sagittarius
is above Sagittarius A.
And it's a point sourcewhich means until now
it wasn't resolvable as a structure.
It was just a single spot of light
so that become a star.
- Is this black ball inthe center of our galaxy,
does it effect the shape orthe structure or the motion?
Or anything
of the galaxy surrounding it?- Yeah.

(31:55):
No, only the,
only the dynamics of thestars right around it.
So these are the stars that Andrea Ghez
and Reinhard Genzel wona Nobel Prize in 2020
for watching for decades.
They watched them orbit theblack hole and from that,
measure its mass.
It's only those stars really
that are being dramatically affected.
This is a deep question because we do know

(32:17):
that big galaxies, M87's a big galaxy.
It has a big black hole.
Small galaxies have small black hole.
Why is that?
It's certainly a correlationthat people observe,
it doesn't sound that unreasonable.
That whatever allows abig galaxy to accumulate
all the gas and all the massthat produces all the stars
and you see in it also will accumulate
stuff at the centerwhich forms a black hole.

(32:39):
That might make sense.
On the other hand, we knowthat's not the whole story
because we do know thatblack holes like M87
are producing those light speed outflows,
they can outshine theirgalaxies by factors of 100.
And they're producingprodigious amounts of energy.
It's mind boggling
and that energy's notjust coming out as light.
It's not just coming out as radio waves.
It's also coming out askinetic energy in outflows.

(33:02):
It's pushing material out.
It's a giant snowplow.- Actual stuff, matter.
- That's right, actual matter
and you can watch that process happen.
By this, what we callfeedback, gas falls down
into the center of the galaxy.
It feeds the black hole
which then enters this very active state.
Starts pushing all this stuff around.
It's kind of like an unruly baby.

(33:24):
It's throwing everything against the wall.
You can limit how fast moregas can rain into the galaxy
and so that black hole,
even though it can onlyeffect the dynamics
of the things right around its environment
and spread that influence outto the sides of the galaxy,
out to beyond the sides of the galaxy,
the sides of clusters.
The largest examples ofthese jets that we see

(33:46):
extend many times the distance.
Intergalactic impact, all from that point.
That most compact thingyou could think of,
down deep at the center.
- And you have said a fewtimes that you're a theorist
and so while thiscollaboration requires people
with a lot of different expertise,
you focus on theoretical analysis.
Can you tell us a little bitabout the specific questions

(34:07):
or topics that you focus on studying?
- You know, 20 years agoI started thinking about
trying to explain the phenomenology
of some of these, some of these objects.
Some of these accreting black holes
and understand what it is thatresulted in the distribution
of light that we see.
The polarmetric properties that we see.
Variability properties that we see

(34:28):
and that was inextricably tied up
with what's happeningdown at the Event Horizon.
So how these black holes grow.
How they launch those outflows.
And that led me right awayto be trying to make models
of what that plasma,that astrophysical bluff
around the black hole that is so important
for the astronomers, for us.

(34:49):
Making numerical prediction,explicit predictions.
What that looked like.
And then I did a thing whichis dangerous for a theorist
as I thought maybe wecan answer this question
on timescales that matter for my career.
I have a, kind of a ruleof thumb I try to follow.
I try to make predictionsthat can be proven
or disproven in about 10 years.

(35:10):
I think my going timescaleis about 15 years,
so that's pretty goodfor an astrophysicist.
It's within a factor oftwo, so I'm satisfied.
- Considering you're looking at light
that is started in this direction
when the dinosaurs were around.
- Out at M87, no.- Yeah.
- Right, no that's right, that's right.
So originally I'm building these models,
trying to ascertain whatis the right observation

(35:30):
that's going to allow me to distinguish
between different waysblack holes can grow
and different ways theycan launch outflows
and how that affects theirotherwise observed properties
and how that, how thatrelates to how gravity works.
Right, I mean black holes
that we've talked about themas very astronomical objects
but they're also you know,

(35:52):
this kind of perfect mix oftraits for general relativity.
Extremely simple solutions
to Einstein's equationson the one hand and yet,
completely counterintuitive physics.
Extreme physics in every other sense.
It's all non-linear gravity.
My uncle once asked me,
"Avery if you found that generalrelativity was not right,

(36:12):
"would you report that?"
And I had to explain to himthat we're all theorists,
we're all raging egomaniacs.
The one thing we want to do
is knock Einstein off the pedestal
so we can climb onto it.
That's what we're all hoping to find.
Some inkling, some hint whichyou may already have seen
that there's something not kosher
in the theory of general relativity,

(36:32):
something not quite right
that we have to fix up.
We have theoretical reasons for thinking
that has to be the case
but observationally it'sbeen quite difficult
and the place you mightlook, naturalist look
would be right around black hole.
Since that time I've really gotten into
actually trying to make those tests work.
So this is where I come intothe Event Horizon Telescope.
My job is not to come up with the ideas

(36:53):
that motivate the telescope.
We did that.
We're working on ideas
for the next telescope but we did that
and now we're workingon trying to test them.
And trying to bring thosetheoretical concepts into contact,
direct contact with theunderlying observation.
What prediction do we makefor the fire donuts right?
So for M87 one of them was,
it should be bright in the south,

(37:15):
not bright in the west andthat was a little weird.
That sounds like a very boring prediction
but the reason is because lightspeed emanation goes west.
It's about 10 degrees northwest.
So you'd have thought thatif there was a bright side
to the black hole,
it's in the directionof the emanation but no.
It's not, because the material is rotating
very rapidly and we see theside that's coming towards it.

(37:37):
It's a searchlight effect.
When I say wrap, it's rotatingat half the speed of light.
And there's a search light effect.
The mission gets beamed inthe direction that it's moving
and so we see it, theside coming towards us
and that's the south.
So that the jet as a whole,
it's all spiraling around in a jet
is going towards the east.
And that's not truefurther out in the jet.
As the jet gets wider
and it's just anger moenum constipation.

(37:58):
It's just the figureskater expanding her arms,
slowing down.
But at the black hole
the arms are all tucked innice and tight and we see it,
we see it rise in the south.
So that's the kind ofprediction that we made.
For Sag A* we have predictions about
how much it can vary.
So how frenetic is the puppy right?
It's not enough to say frenetic puppy,
we want to know didthis puppy just wake up?

(38:19):
Is he tired?
Has he received a little bit of training?
Is it a high strung puppy?
Is it a chill puppy?
It was like these are,
we have a quantification of all of that
and it turns out that the large scale
numerical simulations that we have
that give us purchase on that question
are a little bit too variable.
So there's a mystery.
We don't really know,
it's like are those really applicable?

(38:41):
Was there an ingredient we just missed?
Did we forget to put thebaking soda in or something?
We'll find out right?
This is, just leave somethingexciting to think about
and try to develop going forward.
But building out those direct tests,
direct contact with the data
is where we've been focusedfor the past five years.
- The Sagittarius A*, theblack hole in our Milky Way.
How did it come to be there?

(39:02):
How was it formed?
Why is there a black hole there?
That was a brilliantquestion, I don't know.
So there's two kinds of black holes
that we observed in the universe.
We'll have the things likewe've been talking about
that we call super massive.
We think every galaxyhas one at its heart.
Sometimes you'll see two
and we think that's because the galaxies,
we do see galaxies run into each other,
merging galaxies.

(39:23):
They'll ultimately settle down and combine
and distribute and when that happens,
the two will merge and become one.
One of these big ones for gas.
The other kind of black holethat we see in the universe,
that doesn't mean there aren't other ones.
These are the two that wehave direct evidence for
are what we call stellar mass black holes
which is also inconveniently SMBH.

(39:46):
The stellar mass blackholes are the end products
of every star over about 30 solar mass.
So a star that growsbeyond 30 solar masses
during its formation hasa, a unique sentence.
Right, there's nothing it's gonna do
that's gonna stop it from forming
one of these stellar mass black holes.
Now we know that vary massed stars

(40:07):
live only a very short time.
They live only about a million years.
So when you generate a massive star,
it, as far as astronomers are concerned,
the universe is concerned,in the blink of an eye
you've now made a stellar mass black hole.
One of these things that's 10,
maybe 30 times the mass of the sun.
There is some heavy one.
- Which we haven't seen directly.
- We haven't imaged them but LIGO,

(40:28):
so this is gravitation wave experiment
where they're looking not at light,
not at the subtle ripples inthe electric magnetic fields
that we pick up.
But subtle ripples inthe gravitational field.
A subtle jiggling due toripples in space time.
They are seeing the merger
of these stellar mass black holes.
So we know they're there.
We do see them.- The famous LIGO discovery

(40:49):
was two black holes eventuallyslamming in to one another.
- That's right, exactly.- Right.
- So LIGO's you know, very inefficient.
Every time they find two, they lose one.
EHT is very environmentallyfriendly right?
We see one black hole ata time and we leave it be.
So that's a very exciting dynamical event.
Unfortunately, I can'tgive you a formation story.
You asked where do these supermass black holes come from?

(41:09):
I can't give you the formation story
for the ones at thecenter of the galaxies.
I know that if I have to wait
for one of these stars to form.
Right, these stars don'tjust automatically form
in the universe out of nothing right?
The first stars are very different
from the stars you see right now.
Stars you see right now
have all kinds of heavy elementsin them that were created

(41:29):
in the furnace of earlier stars.
The first stars don't have that.
First stars are made out ofjust what the universe had
at the beginning.
So they look very different.
The James Webb Space Telescope,
one of the things that it's designed to do
is go see those and tell us about them.
If you wait for those to form
and then create a stellar mass black hole
and then start growing.

(41:50):
You put them in a very advantageous place.
You let them gobble up
all the gas they can get their hands on
and there's a limit to how muchthey can get their hands on.
First you can only grab
what you can gravitationallyaccess and second,
if you start trying to eattoo much, it gets in the way.
At some point you startshining too brightly
and the light that you're putting out,
the electromagnetic radiation you put out

(42:10):
starts pushing back on the flow.
- Right.- It becomes self-regulating.
Just look at a hot dogeating contest right?
At some point, at some pointsyou can't go any faster
and that fundamentallylimits how fast they can grow
and if you put in that limit,
we call that the Eddington limit.
After Sir Arthur Eddingtonwho first identified it.
If you say they're growingat the Eddington limit,
at that maximum rate,

(42:31):
they can't get to the sizesthat we see some quasars at
in the universe.
So we know there are thesesuper massive black holes
floating around earlierthan you could make
from a stellar mass black hole.
So now, how do you do it?
I don't know, it's a great question.
- Is that part of what EHTis hoping to figure out?
How these things come to be?
If there was a way to circumvent

(42:52):
Sir Arthur Eddington'slimit, that would be one way.
Not just looking at the gravity,
but not the essentialgravity, at some sense,
the gravitational stage
on which all of theastrophysical dramas play out.
But instead looking atthose astrophysical dramas,
we try to determine
how does accretion onto black holes work?
Is it really subject to the assumptions

(43:14):
that go into the Eddington limit?
Could you exceed it byorders of magnitude?
If you can, then wecan solve that problem.
The other thing is is ofcourse there's a future
beyond the EHT.
You know there's a near future
but then there's a farfuture which is the one,
I get excited about both.
They're both wonderful but you know,

(43:35):
the one I dream about isthe far future of course.
The EHT in space that we have.
We've made the earth 100 times bigger
by virtue of putting satellitesout there with radio dishes.
This is something that youcould actually talk about doing.
This is, this is aproject that's accessible,
at least technologically,just about accessible today.
So this is something wecould be thinking about

(43:56):
50 years from now, timeline's very,
always very long for that.
And if you built an instrument like that,
we could see every M87 in the universe.
So that would have theresolution necessary to see M87
all the way to the edge of the universe
which is a remarkable, a remarkable thing.
Now maybe they're notall bright enough to see

(44:16):
but that means that you'rereally talking about
looking at black holes
and their evolution across cosmic time
and this gets to exactly this question.
How did they grow, howdid they get to be so big?
- Is M87 one of the biggest we know of?
Are there other M87s floatingaround or is it an anomaly?
- There are other similarly-sizedobjects in the universe
but they are anomalies.

(44:38):
10 billion solar massesis about the limit.
There's a category ofultra massive black holes
which are defined as biggerthan 10 billion right?
So I mean we're gettinginto the superlative game.
- This is where the mind reels
because these numbers are just impossible
for me to comprehend.
I think impossible for most people.
How do you wrap your headaround these distances

(44:59):
and sizes and scale?
- We don't, they're numbers.
- You shut up and you calculate?
- You just write them down.
That's a really great question.
How do you internalizeor connect these things
to a terrestrial scale?
And it really is not, Ithink it's not possible.
You say M87 is bigger than Sag A*
so you get the, and similar things right.

(45:20):
How many 10 billion, how many one billion?
Do that kind of game right?
But what does it mean to be a 10 billion?
That's one I don't know.
It's physically enormous.
- To add another number to this.
Do theorists have estimatesfor how many black holes
there are in the whole universe?
- One per galaxy right?
If I put my Carl Sagan hat on,
that's billions upon billions.

(45:42):
In our galaxy, remember I said before
that every 30 solar mass black hole,
I'm sorry 30 solar massstar makes a black hole
and there is a certain number
of 30 solar mass stars you make
for every solar mass star,every star like the sun.
And stars like the sun don'tdie in a million years right?
They last 10 billion years.
Every solar-type star in the galaxy about,

(46:05):
is still sticking around.
Maybe some have gone.
It's still of the youngwith it generation.
Every half solar mass star
in the universe still exists right?
They have not run out of fuel yet.
So you can just look at thenumber of solar mass stars,
number of half solar mass stars
and you can estimate howmany 30 solar mass stars
must there have been.
And remember, they fly byin the blink of an eye.

(46:26):
10,000 times brighter,10,000 times shorter lives.
Candlelight burns 10,000 times as bright,
burns 10,000 shorter lives right?
As long, 10,000ths okay.
So these are short-lived,
so they're almost instantly transferred.
So we can estimate how many
of these stellar mass blackholes there are in the Milky Way
and the answer is millions.

(46:48):
So we talked earlier,is Sag A* gonna get us?
No, but I've started callingthe closest black hole.
We don't know what it is right?
It was the closet known black hole
and you'll hear about thatevery now and then in the news.
The closest black holecalled proxima opie,
it's probably something like20, 30 light years away.
You could send a mission to it

(47:08):
if you knew where to send it.
Again, people think aboutgoing to the nearest stars.
You see all these science fiction movies
going to the nearest habitable planet,
maybe we'll stop at thenearest black hole on the way.
We just have to figure out where it is.
This comes back to black holesbeing so difficult to see.
Hardly know where they were.
And so we have somethingthat's right next to us.

(47:29):
No idea where it is.
- Avery, you have a verycool job and I'm curious,
how did you get into black hole research?
- First like many people,I love science fiction.
Love Star Trek.
Just watched originalStar Trek all the time
and the thing that Iloved about Star Trek,
aside from the kind ofsciencey stuff and the phasers,

(47:50):
and of course now we all havecommunicators and the like.
They stopped flipping awhile ago.
One of the things thatI really liked about it
was the exploration.
Every episode goes someplace new.
See something never seen beforeand so that motivated me,
being scientifically ormathematically inclined
to seek out a job where Iget to travel the universe

(48:11):
and Starfleet didn't exist.
Couldn't go on a starship.
I guess you could go now,Musk is making starship.
- Can you afford it?
- Can you afford it?
No, it's getting cheaper every day.
There was no Starfleetto join to go you know,
investigate or explore the universe.

(48:31):
So instead I found a job
where I could explorethe universe in computers
and on blackboards and in my mind.
That's what astronomy really is right?
It's a way to go and see the most extreme,
the most unusualenvironments in the universe
and try to understand them.
After becoming enamored with that,

(48:52):
you know my path is pretty similar.
I went to university,majored in math and physics.
Couldn't get enough and so never left.
- Does it feel likeyou're getting to do that?
You're getting to explore the universe
with this research and others?
- Absolutely, I couldn'thave done it any better
than able to put images ofblack holes up on a view screen.

(49:15):
It's basically an episoderight out of "Star Trek".
- Do you know what youwant to explore next?
- That's a great question.
We have had our heads down thegrinding wheel for so long,
I don't think much about it.
But what to look for next?
Really this era of resolvingEvent Horizons has just begun

(49:37):
and we are now in a veryspecial, a special period
where it's not just theEvent Horizon telescope
but we also have LIGO.
We also have neutrino experiments
that are looking at the universe.
Not in terms of the kinetic waves
or gravitational waves.
But neutrinos as particles.
We have the CTA, theCherenkov Telescope Array

(49:59):
looking at the universein high energy gamma rays.
Again, a very different way to look at it.
And all of these are focusedpredominately on black holed.
We are at the era wherethe theoretical musings
of Schwarzschild and Kerr and Einstein,
you know when theythought about the things
that nobody could ever possiblysee, that's being seen.

(50:21):
Black hole science hasgone from being theoretical
to being empirical over the past 10 years
and we're just at the beginning.
You know the things thatoccupy my future time
in as much as I find it,
are really thinking about how to move from
making that first image to you know,
doing something akin toblack hole meteorology.

(50:43):
We don't want to see a picture.
I want to see beautifulhigh resolution movies.
I want to see magnetic flux tubes.
Little magnetic vortices zipping around.
I want to see flares popping off
that look like solar flares orsolar coronal mass ejections.
Sudden snapping of magnetic field lines,
huge amounts of energy going off

(51:04):
right around the Event Horizon.
Tracking all of these things in real time.
And then understandinghow that all interplays
with the gravity of black hole.
The future in this contextis higher resolution,
higher cadence, higher sensitivity.
It's our Olympics of black hole science.
Was it stronger, faster, higher?

(51:27):
So yeah, that's my future and right,
there's ways to do that.
We've talked about the nextgeneration EHT, the NGHT.
This is not an evolution ofthe Event Horizon Telescope
but a revolution of theEvent Horizon Telescope
where we add 10 or more new dishes
that are dedicated to doingthis sort of millimeter VLVI.

(51:48):
This sort of
earth-side telescope.- On top of
the existing telescopes already?
- On top of the existing ones.- Wow.
- Right, and every telescope you add
is not just one piece better
because it's really thenumber of pairs of telescopes.
The way we fill in thatmirror goes as the square
of the number of the telescopes.
So the difference between 20 and eight
is not the difference.

(52:09):
Is not 12 right?
It's 400 versus 64.
So that's going to allowus to start mapping out
that black hole meteorologyto very large distances
away from the black hole.
So how do you connect theenvironment to the horizon?
And then there's thatspace fantasy almost right?
Musings about EHT and space

(52:31):
which we have to start doing now
if it's going to happen.
That just opens up the entire universe
to this sort of thing.
Now we're not talkingabout two, maybe 10 targets
if we really push it.
We're talking about million.
That would be anextraordinary change right?
So then we would go fromtheoretical black hole science
to empirical black holescience to surveys right?

(52:54):
Having so much data,
who knows what you're gonna do
with all of what you're gonna find.
- I'm curious.
When you look at theseimages that you get.
I remember in 2019, with the M87 image,
when you sort of had the imageyou came up to me and said,
"Colin, you want to see something?"
And you showed me on yourphone and I was like,
"That's incredible."
I'm one of the first peopleon earth to see this image

(53:16):
but you were probablyamong the very, very first
and with the Sag A* too.
You've now been the first,among the first people on earth
to see something.
What's that like for you?
And do you, are you ableto look at that data
and the fire donut and sortof let your imagination
take you to the place itself?
- So often those firstimaging experiments,

(53:38):
you're just trying to geteverything to work right.
So there's a sense of elation
which doesn't necessarilycome from the importance
of the moment.
But oh thank God it, itfinally did what I asked.
We actually producedsome of the first images
of Sag A* at a workshopright here at Perimeter
and shortly after M87 in August 2019,

(53:59):
we had a workshop toidentify the main challenge
and begin game planning out
how we were going to solve all of them
and it turned out that many of those,
I think all of those gave lights
of what we ended up following.
So that was a momentousmeaning and there we did see,
we didn't share.
So we kind of sequestered the groups.

(54:20):
Each analysis team istrying to make their,
their particular image withtheir particular method
and we have a method that we use.
But everybody was producing images
and you kind of knew that wewere getting something good
because everyone was smilinga lot and yeah, yeah.
We've produced the first image
and it looks about like whatwe thought it should look like.
There was a lot of happiness in that room.

(54:42):
Did we feel the weight of history?
Thinking oh we've seen thisthing for the first time?
I'm not sure I'd go that far.
- That was just me.- But we do now.
We do look back on it and we think,
you know it's a very special thing.
M87 was seen by half thehuman beings on planet earth.
We're talking about Sag A* today,
it was just released but I imagine that

(55:02):
it will also be seen by a similar number
and there's few cultural phenomena
that transcend at that level.
It's an amazing privilegeto be part of that.
- Well Avery,
thank you so much for justspending this time with us
and once again helpingus understand black holes
and the EHT.
It's like I said, it's oneof my favorite subjects.
- Well my pleasure

(55:23):
and thank you for havingme Lauren and Colin.
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