Shep Doeleman on hunting for black holes

Shep Doeleman is a senior research fellow at the Center for Astrophysics | Harvard & Smithsonian and one of the world’s leading experts on black holes. He heads the globe-spanning Event Horizon Telescope (EHT) collaboration, which in recent years unveiled humanity’s first-ever images of black holes – including the supermassive behemoth at the centre of our own Milky Way galaxy. Doeleman takes Lauren and Colin behind the scenes of the EHT’s discoveries, which earned the collaboration the prestigious Breakthrough Prize in Fundamental Physics in 2020. He also looks ahead to the next big milestones in black hole science, such as the Next-Generation EHT (ngEHT) and the Event Horizon Explorer, which will bring these mysterious phenomena into even sharper focus. View the episode transcript here.

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, the challenges they encounter, and the drive that keeps them searching for answers.

The podcast is produced by the Perimeter Institute for Theoretical Physics, a not-for-profit, charitable organization supported by a unique public-private model, including the Governments of Ontario and Canada. Perimeter Institute acknowledges that it is situated on the traditional territory of the Anishinaabe, Haudenosaunee, and Neutral peoples. Perimeter’s educational outreach initiatives, including Conversations at the Perimeter, are made possible in part by the support of donors like you. Be part of the equation: perimeterinstitute.ca/donate

Episode Transcript

(00:01):
- Hello, everyone.
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(light music)

(00:24):
- Hey, everyone.
And welcome back to"Conversations at the Perimeter."
I'm Colin here at Perimeter Institute,
as always with Lauren.- Hi.
- And we are so glad to be bringing you
the conversation that wehad with Shep Doelman.
Shep is the leader of theEvent Horizon Telescope,
or EH, a globalcollaboration of scientists
on every continent that gave us humanity's

(00:45):
first ever glimpse of a black hole.
- Now, chances are you'vealready seen the images captured
by the EHT.
In 2019, the collaborationunveiled an image
of the super massive blackhole in the M87 Galaxy,
and in 2022 they imagedthe black hole at the heart
of our own Milky Way galaxy.
Shep tells us how theseincredible discoveries were made

(01:07):
through the collaborationof hundreds of scientists
around the world, half a dozen telescopes,
and of course, incredibleamounts of ingenuity.
- Yeah, it really is amazingto hear Shep describe
not only the power and themystery of black holes,
but also the monumental global effort
that went into seeing themfor the very first time.
And Shep has such a sharp sense of humor

(01:27):
and a knack for storytelling,
this conversation just flew by for me.
- Shep also assured usthat in black hole science,
the best is yet to come.
He tells us about the next generation EHT,
which will expand theearth-based telescope array
to observe black holes in even more detail
and future projects
that will include space-based observations

(01:47):
and even capturing moviesof black holes in action.
It's a fascinating rideand we felt so fortunate
to be a part of this conversation.
So, let's step inside theperimeter with Shep Doelman.
- Shep, thank you for being here
at "Conversations at the Perimeter."
- It's a pleasure to be here.
- You and I have talkeda number of times before
on Zoom calls where we each have

(02:09):
just been a little a cubeon a tic-tac-toe board,
but this is the firsttime chatting in person
and there's a question I'vealways wanted to ask you.
What's a black hole?
- What is a black hole?
So if you ask different people,
they might have different viewpoints
on what a black hole is.
I mean, quantum physicists will want
to dive into information theory.

(02:29):
I'm an astronomer, so I livekind of in the real world
and my idea of a black holeis that it's a condensation
of matter that's so dense
and in such a small region that it creates
an event horizon around it.
And that's a point wherelight can't escape.
Even if you travel at the speed of light,
you can't escape thegravity of that black hole.

(02:50):
That for me is a black hole.
And what's more, theseblack holes we know exist
in the universe.
So, they're something we can study.
And it's not just a theory,
it's not just somethingon a piece of paper.
It's something we can seewith advanced instruments.
- And you know what, Shep,
today I was getting ready to come to work
and I have to tell you,
I was talking to my twoand a half year old son
and I told him, "Guess what?

(03:12):
Today I'm gonna talk tosomeone named Shep Doelman
and we're gonna talk about black holes."
And he really lovesdigging with his shovels.
And he told me, "Mom,I've seen a black hole
when I was in the forest."
So, you know, I think eventhese really young kids,
they have a picture cometo mind when they hear
about a black hole, how muchof that picture that we have,

(03:35):
as soon as we just hear that phrase,
how much of that is really true?
- Well, it is true in thatlike when you dig a hole
in the forest, maybe the onethat your son is thinking of,
you can put things in it,
you can forget about them, you know?
So, we think of a hole as being something
where you can store things
or it's out of sight, out of mind.
And a black hole really is like that.

(03:57):
When things fall into the black hole,
when they go through the event horizon,
there's really no causalconnection left to our universe.
They're gone forever.
So, it's really a hole that youcan't withdraw anything from
in the future.
So in that sense, yourson has it exactly right.
It's the universe's big pocket.
It's something that you put something in,

(04:18):
you can't take it out again.
- Is there anything misleadingabout what we might picture
when we hear black hole?
- I study black holes for a living.
We observe them, but blackholes exist in literature.
They exist in even music.
They exist in art.
So, a lot of the things thatwe know about black holes come
from the culture in which we live.

(04:40):
So, it's perfectly fineto think about black holes
and interpret them in your daily life
in a way that makes sense to you.
And if you talk, again,to a quantum physicist,
they'll have a differentway of looking at it.
If you talk to an astronomer like me,
I'll be thinking about, you know,
the hot gas that swirlsaround the black hole
that allows us to even see thatthere's a black hole there.
So, everyone can think about black holes

(05:03):
in the way that they want to.
When you get down to it,there are some formulas,
there are some equations,there are some real world,
telltale signatures of black holes.
But I really enjoy the factthat they have an existence
beyond the theory,beyond the observations.
I embrace that.

(05:24):
- How long was it before black holes moved
from purely an idea, a theory,
to something that you know is out there?
- Black holes have a deep history.
When we made our firstimage of a black hole
using the event horizon telescope
that I'm sure we'll talk about,
we felt a deep connectionwith that history.

(05:45):
I like to phrase it inthis way, that we have
a 100 year handshake with Einstein,
that we are living in an erawhere if Einstein were here,
he would be part of our team.
There's a deep visceralconnection to all the people
who came before us and studied this.
And it begins with general relativity.
It begins with Einstein in1915 coming with this idea

(06:06):
that gravity was differentthan Newton had theorized.
That there was a differentway of thinking about gravity.
It was a deformation in space time,
and things would move inthat deformed space time.
And then the question is, well,
how do you know that that'sthe right new theory?
Well, it explained things
like the perihelion shift of mercury.
When mercury orbits the sun,

(06:28):
it changes its orientation a little bit,
it gets a little kick thatgeneral relativity predicts
that Newton's gravity would not.
So, it explained that right away.
And then the next thing that happened
was Karl Schwarzschild, inthe trenches of World War I,
solves Einstein's equations
and he comes up with this ideaof the Schwarzschild radius.

(06:49):
This is where the event horizon is.
And Einstein is sotickled by this solution,
by this scientist who'sserving in World War I.
He presented to the PrussianAcademy of Sciences.
And for many years,
that was just a theoreticalmathematical oddity.
No one really thought youcould make a black hole.

(07:09):
And indeed Einstein went to his death,
convinced that naturewould never allow you
to make a black hole.
There would be somethingthat would prevent it.
Things would be orbitingthe black hole so fast that
the centrifugal forcewould prevent the collapse
into a black hole.
And now, of course, weknow that they do exist.
There was work by Oppenheimerand Snyder in the 30s

(07:30):
that really showed youcould condense something
beyond the event horizon.
And astronomers began to get the inkling
that there was something outthere looking at Cygnus X-1,
a black hole that'sdevouring another star.
And the signature,
the radiation signature fromthat was such that it's hard
to explain it unless you have a black hole

(07:50):
that is devouring another star.
And then the story goteven weirder in a sense
because we began to see thecenters of galaxies glowing
so brightly that only the conversion
of gravitational potential energy,
a matter falling in and turningthat into radiant energy,
which a black hole can do,was the only explanation.

(08:12):
And all of a sudden youcould have black holes
that were millions oftimes the mass of our sun,
billions of times the mass of our sun,
at the centers of these galaxies.
So, the evidence beganto become overwhelming,
but we had never seen one,
we didn't have the angular resolution,
we didn't have the instrumentationthat would've allowed us
to really see it.

(08:33):
And that's what we've been working on
for the past 20 years.
So, from Einstein toSchwarzschild, you know,
all the way through likethinking about quantum effects
around black holes fromStephen Hawking and Bekenstein,
all the way through towhat we're doing now,
which is observing black holes,
it's been a wild rideand it's hard to believe
this has all happened insuch a short amount of time.

(08:55):
- So, can you tell us a little bit
about the event horizontelescope and how it works,
how it's achieved this?
- This is just about myfavorite thing to talk about,
but so when you think aboutobserving a black hole,
it's totally counterintuitive.
Something that's designedby nature not to emit light,
that swallows all the light.
How do you go about viewing it?

(09:17):
So, when you think about takinga picture of a black hole,
which is what we did withthe event horizon telescope,
I wanna first talk about why they glow.
So, all this matter isfalling into the black hole,
let's say the center of a galaxy.
And as it falls in, it encountersthis cosmic traffic jam.
It's trying to get intoa very small space.
And so it backs up,

(09:37):
it collides with thegas that came before it,
and it soon heats up tohundreds of billions of degrees.
So, in a paradox of their own gravity,
black holes glow extremely brightly,
especially at the centers of galaxies
where there's so much gas.
So, we have this intenseflashlight illuminating

(09:57):
from all directions, this event horizon,
and the light gets bent around it.
So in about 1916, Hilbert asked,
"Well, how big would this ring of light be
around the event horizon?"
He came up with some clear formulas
and Max von Laue in 1921 confirmed that.
And then a bunch of simulationswere done in the 70s

(10:21):
and then later in the 2000s that showed,
given a super massive blackhole at the center of a galaxy,
you would be able tosee this ring of light.
And the dimensions ofthat ring would tell you
how massive the black hole,
if Einstein's theory was correct.
So, in one measurementyou could measure the mass
of the black hole andconfirm Einstein's theories.

(10:43):
And then we had to ask,
well what wavelength of light
is the right wavelength to look at?
Because this thing can glowat all different wavelengths,
in the optical, in the x-ray, ultraviolet.
And it turns out that you wannabe able to see all the way
to the event horizon.
And in the optical youprobably can't do that.
It's probably optically thick.
You'd see like a cloud of emission outside

(11:05):
of the event horizon.
But with radio waves,you can see all the way
to the event horizon.
So, now the event horizon telescope,
so now we know whatwavelength to look at it in
and we know that we can see this ring
and we decided that we coulddo this in the radio waves,
but we needed a telescopethat was as big as the earth
because the size of theobjects you can see on the sky

(11:28):
is basically the wavelength of light
at which you're observing,
divided by the size of your telescope.
A very simple formula.
So, if you're looking in the radio,
maybe a few millimeters of wavelength,
you need to see the nearestblack hole, Sagittarius A star
in the center of our galaxy,
or M87 at the next distant galaxy.
You need to have an angular resolution

(11:51):
that's about 50 microarcseconds.
Okay, and what does that mean?
This is equivalent tobeing able to read the date
on a quarter if you're in Los Angeles
and the quarter's in NewYork, or equivalently,
it's being able to see likea tangerine on the moon.
So, we had to devise a telescope that had

(12:11):
the greatest resolvingpower of anything ever done.
And the way we did itis we took telescopes
on different sides of the earth,
we recorded lights from the black hole,
stored it on hard disks,
and then brought those discstogether to a central facility
and we played them back and wewere able to form a telescope

(12:33):
as big as the distancebetween the telescopes.
So, by linking telescopesacross the earth,
we made a telescopethe size of our planet.
And when you think about it,
what we're doing is pretty much the way
an optical telescope works.
An optical telescope is a perfect parabola
and it's a highly reflective surface light

(12:53):
from an object bounces off that.
And it all comes to a focus
and that's where youput your camera, okay?
And it's the shape of thatlens that gets all of the light
to that one focus at the same time.
And what we do with theEvent Horizon Telescope
is we take these recordings of radio waves
from the black hole,

(13:13):
we bring them to a supercomputerand we play them back
and align them perfectly.
So, we replicate what anoptical telescope does
with its mirror in silicon.
We delay the light and play itback so it perfectly aligns.
And that gives us thisearth-sized telescope.
And even that's not enough,
'cause you need manytelescopes around the globe.

(13:35):
So, it's not just two telescopes,
but in the first instance ofthe Event Horizon Telescope,
we took eight telescopes,observed simultaneously,
and that was just enoughto make the first image
of a black hole.
- It seems like an almostimpossible undertaking.
How was this idea even conceived?
Did you have a eurekamoment one night and wake up

(13:56):
and think we could make a telescope
the size of planet Earth?
It's almost crazy.- Yeah.
It is like mind bogglingwhen you think about it.
And I do pinch myself occasionally,
not just because it was avery interesting project,
but because we got to do it.
As with many ideas, this hasbeen burbling for a long time
on the theory side, as I mentioned,

(14:17):
back in the early partsof the 20th century,
people have been thinkingabout how big a black hole
might appear to be on the sky.
And then there were manysimulations done in the 70s
and the 2000s to showwhat it might look like.
And at the same time, thisidea of radio interferometry,
of linking telescopes aroundthe globe, was in full flower.

(14:39):
So, we had already begun tolook at longer wavelengths
with less angular resolution on the sky,
at galaxies, at stars.
And we had come to understandthat this was a way
of getting the most extremeangular resolutions possible
from our planet.
What we did was we justtook it to the next level.
We said, we can see allthe way to the heart

(15:01):
of the black hole at short wavelengths,
and we can make the electronics now work
at these short wavelengths,
which had been harder to do prior to
the Event Horizon Telescope
and everything willconverge and we'll be able
to make this image of a black hole.
So, it was really anadvancement of the technology

(15:21):
with an idea that had already been around
for a while that made this possible.
- So, it really had tohappen when it happened
because the technology hadn'tcaught up with the ideas
until fairly recently?
- Yeah, it was reallytechnologically based,
like a lot of the ideaswere there and it came
at just the right time.

(15:42):
And as with all things like this,
you need a few crazy people whoare willing to champion this
and risk their careers on it.
So, one of the firstthings we did was we said,
even with this short wavelength,
even with the Milky Way Galaxy,there as a prime target,
even with a few telescopesaround the globe,

(16:04):
we're still short on sensitivity.
Given the instrumentation that we had
in the early 2000s, wewould not have been able
to detect the super massive black hole
at the center of the Milky Way Galaxy.
So, we began to developthis very wideband system.
So, instead of justrecording a small sliver

(16:24):
of the radio spectrum,
we broadened that torecord many frequencies.
And that took about four years to develop.
But once we had that,
the increase in sensitivity was dramatic.
That proved to be theenabling new capability.
And then in 2007, we tookthe systems to Hawaii,

(16:47):
California, and Arizona and welooked at Sagittarius A star.
For the first time
we discovered eventhorizon scale structure
around a black hole.
So, we knew all of a suddenthat there was something
really small and that we couldmove towards real imaging.
So it was that moment in2007, 2008, when we realized

(17:08):
that the Event HorizonTelescope could succeed.
We had the technology, we had the theory,
but now we had the actualmeasurement that there was
something really small there.
And that set us on the path.
- And I'm curious too about thenumber of telescopes needed.
You said you had eightto make that first image.
So, with the technologythat you had at that time,

(17:28):
how much would've changedif you had had seven
or if you had nine, howmuch does this change?
And also how much morecomplicated does it become
as you add more telescopes?
- Yeah, what a great question.
So, is eight telescopes enough?
So, we did our first experimentswith three telescopes
and we knew that wasn't enough.
We could tell there wassomething going on there.

(17:49):
It was a great discoverythat put us on this path,
but we couldn't make an imageand we decided to just get
as many telescopes as we couldand that when we had enough,
we'd be able to analyze thedata and then this image,
if it was there, would emerge.
But there really is a piece of the puzzle
that set us at this levelof eight telescopes.

(18:10):
I told you before that weneeded more sensitivity
and we increased ourbandwidth and that was true.
Without that extra bandwidth,
this would not have been possible.
But in addition,
there was a new facilitythat was just emerging called
the Atacama Large MillimeterArray, or ALMA, for short.
And it was a new facility in Chile
and it consisted of roughly 60 dishes,
each 12 meters diameter.

(18:32):
If we had recorded datafrom one of those dishes,
we might have been able to pull this off.
But we realized that if we gotall those dishes in one area
to act as a single dish,
if we could add all thesignals from those 60 dishes,
we would have effectively a gigantic dish.
And that would increase our sensitivity,

(18:52):
again by a factor of 10.
So, we took our time and wedeveloped a whole system over
about seven years to phase up
or combine all of thosetelescopes together.
And while we were doing that,
other telescopes were made ready.
So when ALMA was ready,we had seven other dishes
and then we kicked offour observations in 2017.

(19:14):
we had amazing weather,
I mean just absolutely fantastic weather.
And it was a combination of having ALMA,
having the wide bandwidths,
having seven other dishes, andhaving this amazing weather
that put us at just the rightmoment, just the right time.
People say, "Were you lucky?"
I think we were fortunate, butfortune favors the prepared

(19:36):
and we had spent almost twodecades preparing for this.
So when the time was right,
we had everything in place
and then we were able to make the image.
- I remember shortly afterI first started working here
at Perimeter, this iseight or nine years ago,
I was talking to yourcolleague, Avery Broderick,
who works here, and we'vechatted with him on the podcast.
And he told me, I actually thought he was
a little bit out of his mind at the time.

(19:56):
He said, "We're gonna takethe world's first image
of a black hole, and mark my words,
when we do it will be on the front page
of the 'New York Times' above the fold."
And I said, "Okay, Avery."
Sure enough, in 2019 youhave a press conference.
You issue the image of the M87 black hole.
And not only the front pageof the "New York Times"
above the fold, but all ofthem, all the major newspapers,

(20:19):
it seemed to be, had themright on the front page.
And I'm curious, A, Ishould have trusted Avery,
he knows this stuff better than I do,
but also why do you think
it captured people's imagination.
There are breakthroughs inscience that get relegated
to page C19, but this onecaptured the world's imagination.
- True.

(20:39):
When we came down the morningafter this announcement
on April 11th of 2019 and wesaw the "Wall Street Journal"
and the "New York Times," "Boston Globe,"
every major newspaper hadthis picture above the fold,
as you say, it reallyrocked us back on our heels
because we had been sofocused on getting this image.

(21:03):
We'd been so focused onsome of the materials
that would explain it to the public
that we hadn't really thoughtabout where it would land.
Right?
Or I hadn't thought aboutwhere it would land.
I knew it was gonna be big,but the visceral connection
with the curious public,and the curious public
is they ask the best questions.

(21:24):
Like they're really curious, right?
And the connection was dramatic.
So, we were surprised.
I was surprised anyway.
I mean you might havepredicted there'd be some play
in the media, but you know,
I got into cabs and I would say,
"Hey, what do you think aboutthat black hole business?"
Not letting them know that Ihad anything to do with it.

(21:46):
And they would say, "Ohyeah, it's amazing."
You know, and they would startexplaining how it was done,
you know, and I would say, "Really?"
And they were like, "Come on, get with it.
I mean this interferometrystuff, it's here, it's now."
You know, so people were very invested
in understanding the result,
but your question was why?
And I think it's due toa few different factors.

(22:07):
One is, people are alwaysinterested in monsters
and there's no biggermonster than a black hole
that sits at the center
of a galaxy devouringeverything that comes near it.
All throughout history, Greek mythology,
there are these monsters
and we're just fascinated with them.
And to be able to see one
that you've only heard about before
and has been the subject of sci-fi movies,

(22:29):
that captured everyone's imagination
just to know that it was out there.
That's the first thing.
The second thing is,black holes are unique
in that once you fall into one,you can never get out again.
It's a knot that you can'tuntie, that is scary.
So in addition to being a monster,
it's also especially scary.
And to know that there'sreally something out there

(22:50):
that's a portal from our world
to a place where youcan never return from,
that captured people's imagination too.
And then I think a reallyimportant aspect of it
was that we did it as a team.
There was early work that putall of this on solid footing,
you know, on the theory side,
also at the early experimentsthat I told you about.

(23:12):
But to make the image,required connecting people
from around the globe, youknow, sidestepping borders,
all the things that normallydivide us as humans.
We brought the best peoplewith the best expertise,
no matter where they came from,
we brought them togetherto form this team.
We used telescopes around the globe

(23:34):
and then we used the earth itself,
the geometry of our planetas part of the telescope.
I mean, you can't geta more kumbaya moment
than this, right?
Everybody working together,everybody contributing,
the planet itself forming thescaffolding of our telescope
and then addressing oneof the greatest mysteries

(23:57):
that we have ever really contemplated.
And then coming with a success.
All of that I think just gavepeople a sense of wellbeing,
of knowing that humans could pull together
to do something truly extraordinary.
And now that we're facedwith things like, you know,
the pandemic and we're facedwith the climate change,

(24:19):
and we're faced withhunger, and all these things
that we're gonna have todeal with on a global basis,
this is a beacon,
this is an exemplar of how wecan come together as people
to tackle the really big questions.
- And your role on this very big team
is the founding director of this project.
How do you describe your role?

(24:42):
- I led many of the earlyexperiments that showed this
was gonna be possible.
And that was with a small team.
And that for me is probablythe thing I'm most proud of.
The thing, you know,these early experiments
where we had no idea ifthis was remotely possible
and working with a smallgroup of colleagues
and seeing for the firsttime that there was

(25:03):
this event horizon scalestructure, scientifically,
that was the greatest momentI have felt in my career.
And that motivated me greatly.
But, my role later grew to beorganizing this global effort
and while in the early stagesI derived most satisfaction

(25:24):
from the results, like lookingat a graph and seeing, yes,
we've seen something that's only
like 30 microarcsecondsacross, it's like amazing.
But later ,I began torealize that I was deriving
as much satisfaction fromorganizing this effort,
from putting this team together,
from getting the theorists together,

(25:45):
the instrumentalists together.
And I view it a littlebit as herding cats.
So, my role was reallyto get everyone together,
to focus us all with a common vision
and see it through to the end.
That was the most important part.
- In 2019, that firstimage that was released,
that was the M87 black hole.

(26:05):
Since then you've also unveiled an image
of the Sagittarius A star black hole.
Can you tell us about those two?
Why those two and how are they different?
How are they similar?
How did you choose them?
- Well, so you're asking
how did we chooseSagittarius A star and M87?
And in a sense they chose us.

(26:25):
We can't engineer the universe, right?
We can engineer our telescopes,
we can engineer our instrumentation,
but we can't engineer the universe, right?
It turns out that there are two sources.
Sagittarius A star in thecenter of the Milky Way
and M87, 55 million light years away
at the center of the Virgo A galaxy,
that are massive enough and close enough

(26:50):
that they present a ring of light,
this lensed photon orbitaround the black hole
that we can hope to image.
So, we knew going into thisthat Sagittarius A star
was our primary target,
and M87 whose mass was alittle bit less well-defined
was likely our secondary target.
And we observed both of them in 2017
with the Event Horizon Telescope.

(27:11):
Why are there only two?
That's a mystery.
Why aren't there more?
That's a mystery.
Are there others?
Undoubtedly there are othersand new instrumentation
that we're developing will likely bring
other super massive black holes into range
of our planet-sized telescopes.
We'll be able to makemeasurements of other galaxies
and other black holes.

(27:32):
But these two were special because we knew
that we had a shot at imaging these two.
And what I'd like to say
is if I was on a desertisland with two black holes,
these would be the ones I'd want, right?
Because Sagittarius Astar is in our backyard.
It's our own black hole.
But what that means isthat it's very faint.
It's eating very timidly.

(27:54):
So, it glows with justlike a faint luminosity.
And it's a kind of black holethat is probably at the center
of most galaxies out there.
'Cause most galaxies are kindof like the Milky Way Galaxy,
small, non-descript, run-of-the-mill,
working day black holesthat just go out there
and do their thing.
So, we're able to see Sagittarius A star

(28:15):
because it's so close.
So, it's one kind of black hole.
M87 is a monster.
M87 is so powerful that itenergizes a jet of material
that likely leaves fromthe north and south pole
of this spinning black hole.
And this jet is so powerful,it pierces the entire galaxy.

(28:37):
It goes for tens ofthousands of light years
from the center of the galaxy.
You would not wanna be inthe way of that jet, right?
You wouldn't wanna live tooclose to that black hole.
- Why, what would happen?
- It would create conditions that life
would never have existed there, right?
It would just like vaporize everything.
So, what what I'm getting atis that M87 is a different kind

(28:57):
of black hole.
It's a black hole that'saccreting enough matter
that it glows very, very brightly.
And so, it gives us a windowon a different kind of galaxy.
So, what's really wonderfulabout being able to look
at Sagittarius A star andM87 is it gives us an idea
of how to study two differentkinds of black holes.

(29:18):
One black hole that's faint,
one black hole that's eating a lot,
one black hole that's ina large elliptical galaxy,
that's M87, one that's in a spiral galaxy.
So, it gives us two differentflavors of these black holes.
And that's very interesting
from an astronomical perspective.
- When you describe the differences
between M87 and and Sag A star,

(29:39):
like how vast are these differences
in terms of power and size?
Can you give us a sort of amore terrestrial comparison?
- Well, one way of saying itis a Sagittarius A star weighs
about 4 million times what our sun does.
So, you would think that ifthere's a stellar phenomena,
if there's a energetic phenomenaassociated with a star,

(30:00):
that you'd be looking at something
that's 4 million times brighter,
okay, if it scales with mass.
But, it turns out that Sagittarius A star
is surrounded by such a tenuous gas,
such a thin vapor, thateven though it's accreting
what's around it,
it's insufficient to really glow beyond
what a normal star would show.

(30:20):
So, there are these stars wherethe star is being devoured
by a black hole.
They're called X-ray binaries.
So two stars,
one of which has gone supernova,is turned into a black hole
and then is devouring this other star.
Sagittarius A star doesn'treally emit more energy
than one of those star pairs.
That's really extraordinary.

(30:41):
You have this behemoth,
this 4 million solar mass black hole,
and it's the most timid of giants.
So in that sense, Sagittarius A star,
the black hole there, isvery faint, very quiet.
It represents a part ofthe evolutionary life cycle
of a super massive black hole
in which it's just not perturbing

(31:03):
what's around it too much.
M87 on the other hand,is devouring much more,
probably a hundred thousandtimes a greater rate
than Sagittarius A star for its mass.
And so, it is extremely luminous.
It's probably billionsof times more luminous
than Sagittarius A star.

(31:24):
And it ejects this jet that goes
for tens of thousand light years.
So not only is it bright,
but it's also dynamicallydisrupting what's around it
in a way that Sagittarius A star is not.
So, they're very differentfrom that perspective,
just in levels of energyand in the phenomena
that surrounds them.

(31:44):
- And are any of these differences things
that we can see when wecompare these images?
- In a way, yes, and in a way, no.
I hate when people dothat, like yes and no.
So, when you get veryclose to the black hole,
even though there are some differences,
Einstein's gravitydetermines what you'll see.
The space time around theblack hole is so warped

(32:06):
that even though you have M87,
which is accreting at a muchhigher rate than Sag A star,
you see the same ring of light.
And when you look at Sagittarius A star,
you see this ring of light,
you're seeing the geometryof space time and no matter
how you light it up, whetherwith a bright flashlight,
which is M87, or a dim flashlight,

(32:27):
which is Sagittarius A star,
all the light gets bent into this ring
and that's what captures your attention.
If you look at things inthe time domain though.
So, imagine we fast forward a few years,
we're going to engineer something called
the next generationEvent Horizon Telescope.
And the goal is to makemovies of black holes,

(32:48):
to capture the dynamics,to capture the action
around the event horizon.
There you'll see something different.
Sagittarius A star,
because it's 4 million solarmasses entrains the matter
around it to orbit aboutevery half an hour.
So, every half an hour things
will move around Sagittarius A star.
So, during an evening of observing,
you will see a change shape.

(33:09):
It will shimmy while you're watching it.
M87 is six and a halfbillion solar masses.
And the dynamical time scaleis related linearly with mass.
So, the same orbit willtake three weeks for M87.
So if you look at M87,
it will not be changing moment to moment
during a night of observing,

(33:30):
while Sagittarius A starwill be madly spinning.
- Even though M87 is the moreactive, hungry of the two?
- Even though on a largerscale M87 is more luminous,
it changes much more slowlywhen you take a picture of it.
So, when we moved totaking motion pictures
of black holes,
then you will see the moviesfor Sag A star and M87

(33:51):
be completely different.
- So, you've mentionedthe next generation EHT,
what is that?
How does it expand upon the original EHT?
- So you ask yourself,well how can we do better?
The Earth is only so big, sohow do you take the next step?
And, I would add that I thinkit's the human condition
to always be restless.
And it's not just for scientists,
we wanna do the next thing,but also the curious public.

(34:13):
After a while they start asking, okay,
so you've made the image ofa black hole, what's next?
When you think about it,
people are really curiousabout these things
and they're not content withwhat you've done just recently,
what have you done for me lately?
Yes, you imaged a black hole,yawn, you know, what's next?
(Lauren and Colin laughing)
And I get that becausepeople are naturally curious,
they push in the sameway that scientists do.

(34:35):
So, if we're gonna take the next step,
we do have to make movies of black holes
because this will showcase the difference
between M87 and Sagittarius A star.
So, I'll give you just alittle bit of motivation.
The size of the ringaround these black holes
doesn't change much if theblack hole is not spinning

(34:55):
or if it's spinning asfast as it possibly can.
These are very importantparameters for theorists
and observers because if youhave a spinning black hole,
then you can get these jets that erupt
from the north and south polelike the one we see for M87.
And if it's not spinning,as we suspect the black hole
in the center of the Milky Wayis, you don't get these jets.

(35:17):
And indeed around Sagittarius A star,
we don't see these jets, not yet anyway.
The motion of matter around the black hole
is exquisitely sensitive to spin.
So let me put it this way,
if the black hole at thecenter of our Milky Way Galaxy
is not spinning,
it'll take matter about half an hour
to orbit the black hole.
If it's spinning at its full potential,

(35:39):
it would take four minutes.
So, you'll be able to seejust by looking at a movie
if the black hole is spinning or not.
So, it gives you a whole new dimension
into the fundamentalparameters of black holes.
So now you ask, wellhow do we make a movie?
And the the answer is,
you wanna be able to engineeryour Event Horizon Telescope

(36:00):
so that from moment to moment you are able
to make a snapshot image oflet's say Sagittarius A star
and stitch those together into a movie.
We were able to make the image
of M87 pretty much immediately
because it doesn'tchange moment to moment.
So, we were able to takeall the observations
from a single night of observing
as the earth turned and all the telescopes

(36:22):
had different lookdirections and they filled in
this earth-sized virtual lens,
we combined all that datato make a still image.
For Sagittarius A starit's much more complicated
because it's changing its appearance
during a night of observing.
So, there we need to makea motion picture camera
and we have determinedthrough a bunch of simulations

(36:42):
that if we double the number of dishes,
if we go from about 10 dishesnow to about 20 dishes,
that will give us enoughcoverage in this Earth-size lens
so that every five minutes we'llbe able to make a new image
and we'll stitch those together
to make the first motion picture
of the Sagittarius A star black hole.
So, when we think about thenext generation instrument,

(37:04):
we think of a few things,adding more telescopes,
that's the first.
Broadening the bandwidth even further
to make it more sensitive,that's the second thing.
And then observing at a higher frequency
than we currently do.
Right now, the EventHorizon Telescope observes
at 230 gigahertz which limitsour angular resolution.
But by going to 345gigahertz and recording

(37:26):
that simultaneously with 230 gigahertz,
this will give us more angular resolution,
fill in the Earth-sizedvirtual telescope even more
and allow us to make movies.
So it's those three things,
more telescopes, morebandwidth, and more frequencies,
that will transform the EHTinto a motion picture camera.

(37:46):
- And when you're addingthose 10 new telescopes,
you have to choose 10 newlocations where they're gonna be.
Can you tell us a bit aboutthat process of how you choose
where to put the new telescopes?
- So, it turns out that there are
a couple of different factors.
One is you can ask yourself,
if I could put a telescopeanywhere on the planet,
where is the place thatstarts filling in the holes

(38:08):
that I currently have in theEarth-sized virtual lens?
And you can think that there'ssome places where you don't
have a telescope now,and if you put one there,
you would immediately get sharper images.
So, we go through manysimulations and we've identified
some key sites around the globe
that will be very importantto populate with telescopes.
But then you have to ask yourself,
well, I don't wanna put itin the middle of nowhere

(38:29):
because there's no power,there's no communication,
there are land rightsissues, et cetera, et cetera.
So, there's a balance tobe struck between where you
might be able to put a telescope,
where there's already some infrastructure,
and where the ideal placefor this new telescope is.
So, we're playing that game now.
We're going to sites in Mexico,going to sites in Chile,

(38:50):
going to sites in thewestern United States.
I just came back fromTanzania where we're thinking
about putting telescopes in that country
because it fills in very nicely
this Earth-sized virtual lens.
And we're looking at localuniversities that can help us.
We're looking at localinfrastructure where we can use
some of that for power and communications

(39:11):
for these telescopes.
And we've come with a two-phased approach.
The first phase will be toadd about five new telescopes
and that will allow usto make movies of M87
and then we'll add anotherfive or eight telescopes
in phase two which will allow us
to make movies of Sagittarius A star.
And it's been a blastgoing to different places

(39:32):
around the globe andsurveying these new sites.
You feel a little bit like anexplorer with your pith helmet
and you know youradventure pants, you know,
going to these these far flung places.
And it's a new dimension for us
because with the Event Horizon Telescope,
we used telescopes thatwere already in place.
We brought bespoke specializedelectronics to these sites

(39:57):
so that together they could do something
that no one telescope could do alone,
but we used existing telescopes.
Now we're thinking expansively,
where do we put newtelescopes around the globe
that don't have telescopes right now?
And that is very interesting and exciting.
- We've received some questions
from elementary school students for you
and Ria has a question about Sag A star.

(40:19):
- Hi, my name is Ria andI'm from grade seven.
And will Sagittarius Aget bigger or smaller
over the coming years
and what would be theconsequences if it gets bigger?
- Wow, Ria, that's a great question
and it's a very intuitive question too
because black holes digestall the gas around them

(40:39):
and they do grow becausenothing can ever escape
from a black hole.
It's always gaining weight,it's never on a diet, right?
When you think about that.
But it turns out thatSagittarius A star is in a phase
right now where it'seating very, very slowly.
I think the way to say it isthat if Sagittarius A star
was a person,
the way it's eating isequivalent to that person eating

(40:59):
a grain of rice in a million years.
- Oh my God.
- That is the level of starvation.
I may have that wrong.
I know it's a grain of rice in a human
for a very long amount of time.
I think it's about a million years.
It's not gaining weightat an appreciable level.
So, over the course oflike a human time scale,

(41:21):
we won't see SagittariusA star grow at all.
But if it were to grow,
we would see the ringof light surrounding it
increase in size, we wouldsee the time it takes matter
to orbit the black hole increase.
So it would wouldn't take half an hour,
it may take 40 minutes or an hour
to orbit the black hole.

(41:42):
If we're growing appreciably,
we would see it with theEvent Horizon Telescope.
Unfortunately, neither Sag A star nor M87
really is growing fastenough for humans to see it.
Maybe a million years from now,
our ancestors will say, "Hey,Sagittarius A star has grown,"
but we won't.
- And talking about the NGEHTand what may come after it,

(42:04):
there's another questionfrom a student named Jackson.
- Hi, my name is Jacksonand I'm in grade eight,
and my question is,
how detailed do you thinkthe images of black holes
will be able to get?
- Oh, what a great question, Jackson.
And that's what consumesus all the time, right?
- Thought you'd like that one.
- The only thing wethink about is how sharp
can we make these images?

(42:25):
So, lemme put it to you this way.
We've seen this ring of lightand it's a little fuzzy,
I'll be the first to admit that.
But the reason it's fuzzy
is not that we made a fuzzy picture,
it's that we are at the absolute limit
of what astronomers can do.
We've seen this ring, it's a clear ring,
but we're at the limit,
but we're motivated to takean even sharper picture

(42:45):
because we think that that ring
is actually a compilation ofan infinite number of rings.
We see some of the light gentlybent around the black hole,
that's what we callthe n equals zero ring.
But there's some light that does a U-turn
around the black hole and that creates
an even thinner sub-ring closerto the actual photon orbit

(43:09):
and within that larger ring.
And then, there's some lightthat does a full loop to loop
around the black hole, thatcreates an even thinner ring.
And when you think about it,
there's an infinite nestednumber of rings that go closer
and closer to the true photon orbit.
And if we could see pastthe n equals zero ring.
This ring that we've already seen,

(43:30):
and we could resolve the very,
very thin ring just interior to that.
That ring so closely holdsto Einstein's equations
that we'll be able to, in a single stroke,
read off the spin of the black hole,
look for deviations from Einstein's theory
at a much deeper level than we can now.

(43:51):
So, we're actively focusednow on being able to see that
and we think that with
the Next GenerationEvent Horizon Telescope,
we'll be able to see that first inner ring
and make our image of SagA star and M87 sharper
by many factors, right?
So, we're aiming at exactlywhat Jackson is thinking about
and then we can think evenmore expansively and ask,

(44:15):
can we make a telescopelarger than our planet?
And there we're thinkingabout launching a satellite
so that the size of the telescope
would be about the distancebetween telescopes on the Earth,
but the distance betweentelescopes on the Earth
and a distant satellite.
And that will allow us to seethese infinite nested rings
using a different technique,using space interferometry.

(44:37):
So, it's all very exciting.
- Is that the next, next generation EHT?
- Yeah, yeah.
Well, so we have differentnames for these things.
The Next Generation EHT is on the Earth.
And then we have this eventhorizon explorer concept,
which takes a satellite,
launches it into like a mid-Earth orbit
or a high-Earth orbit.

(44:58):
And that will give us theanger resolution necessary
to begin to see these inner rings
with high degrees of clarity.
So, that's where we're goingprobably after the next decade.
So, first will be the NGHT on the Earth,
then we'll be expanding into space.
So, if you thought that buildingan Earth-sized telescope
was hard, just try launchingsomething into space

(45:19):
to do the same thing.
I mean everything is harder in space.
Launching the atomicclocks that are necessary
is very, very difficult.
Getting the data back fromspace is very, very difficult.
Knowing the precise orbitis very, very difficult.
So, everything gets harder when you launch
a telescope into space.
But, we think we have a handle on a lot

(45:41):
of the fundamental concepts.
So, we think this reallyis possible in the same way
that we thought the EventHorizon Telescope was possible.
I wanna add one thing.
So, you asked before about
how the Event Horizon Telescope works,
and we do use telescopes atdifferent parts of the globe.
We record the light andwe combine that light
to create a telescope asbig as the Earth itself.

(46:02):
But, a key part of it is thatwe have atomic clocks at each
of these locations becausewhen the radio waves come in
from the black hole,
you can think of themas crests and troughs.
Troughs coming in from theblack hole, these radio waves.
We need to be able toalign the radio waves
that we record at one part of the earth,

(46:22):
exactly with the radio waves we record
at another part of the earth.
So, we need an atomic clockso we can time tag all
the radio waves that weget at both these locations
so we can line them up perfectly.
If we don't have a reallystable atomic clock
at both these locations,
then you can think ofit as like the waveforms
would be jittering back and forth.

(46:43):
If they're stable,
then we can line them up perfectly
and that's how you make thisEvent Horizon Telescope work.
So, getting one of theseatomic clocks into space
and not disrupting it or not breaking it
during launch or something like that,
that is quite a challenge.
- There's just so many piecesthat clearly have to fall
into place to give us thatone image of a black hole.

(47:03):
And I'm just curious,
how many failed images did you see
that you might have expected?
I might see it today andthen it just didn't look
like what you expected?
- Well, I love that questionbecause in this business
you have to embrace failure.
Failure is your companion.
Failure is not a problem.
If you're not failing early on,
you're not really doing your job.

(47:25):
So first, I'll address yourquestion about the images,
but first I want to go back to 2006.
In 2006 we tried tomake our first detection
of event horizon scale structurefor Sagittarius A star.
And we went to Hawaii and weput specialized instrumentation
on the Caltech Submillimeter Observatory,
which is a telescope onthe summit of Mauna Kea

(47:48):
on the big island of Hawaii.
And we also put this samekind of instrumentation
on a telescope in Arizona, the SMT,
the Submillimeter Telescope.
And we failed.
Everything seemed likeit was working correctly.
All the instrumentationseemed like it was going well,
but we didn't get anydetections, nothing worked.
Even when we steered thetelescope towards very,

(48:10):
very bright objects, we thoughtfor sure we would see it.
We didn't see anything.
And we spent months pouring over the data.
It turned out that a littlepiece of metal had fallen into
the superconducting junctionof the telescope in Hawaii.
So, we were receiving theradiation from the black hole,

(48:32):
but the wave form wasjittering back and forth
because that little piece of metal
was ruining all the phase of our waveform.
So, it was vibrating in thereand causing the whole waveform
to move back and forth.
We were doomed from the start.
And it was only afterwards,
like months later, thatwe realized the problem.
And then we had to dustourselves off, pick ourselves up,

(48:54):
get our heads in the game again,we were horribly, you know,
saddened by this.
And the next time we wentout, which was in 2007,
we added another dish in California
to make the whole array more robust.
We triple checkedeverything 'cause we learned
from what had happened andthen we succeeded that year
in discovering horizon scale structure

(49:16):
around Sagittarius A star.
So, failure is important andyou have to be resilient,
but also learn from it.
On the images, for M87 in 2019,
we were very fortunate becausethe signal was so strong
that you could even look at the raw data
and you could see there wassomething that was ring-like.
I'll never forget, I wasat a dinner at a conference

(49:39):
and one of the postdocswho was deeply involved
in the analysis of the data,his name is Amachek Vilgas,
he came and he showed methe freshly calibrated data
and I think there'ssomewhere in the internet,
there's a picture of thetwo of us just like looking
at this computer screen.
Like, oh my god, Ithink I'm like pointing.
Like that's it, andAmachek is beaming, right?

(50:02):
And that was the moment where we realized,
even though we didn't have an image,
that there was something so crystal clear
that we were seeing this ring of light
around the black hole.
So, for M87 we were lucky and fortunate.
Fortunate, not lucky,that nature provided us
with this very, very clear signal
that we could see with the instrument.
So, there weren't too many false starts.

(50:24):
We did separate the team intofour separate imaging groups
because we wanted to make surethat if we did see a ring,
there wasn't cross contamination.
So, we didn't want everyonein one room and someone says,
"I think I see a ring" andthen someone else says,
"Oh, me too, I also see a ring."
And pretty soon everyonesays they're seeing a ring.
So, we kept four groups totally separate.

(50:44):
We gave them all the data,
but we didn't let them talk to each other.
And then in July of 2018,
we all came together
at the Smithsonian AstrophysicalObservatory in Cambridge
and each group showed their image
and you could see immediatelythat we had four rings.
And that was the moment whenwe all realized this signal

(51:05):
is so clear that even fourdifferent teams that are working
with different algorithms,different approaches,
all found the same structure.
That was when we realizedthat we had a discovery
of great magnitude on our hands.
- What was the mood inthe room at that point?
- Pretty subdued.
No, no, it was like, wewere like going crazy.

(51:25):
It was absolutely a joyful celebration
and the fact that we had all done it
with different methods, right?
And we all got to the same point.
That was really something.
I like to think of that asbeing like a beer stein moment.
Like, we were clinking ourbeers, we were like drinking.
It was a moment of real comradery.

(51:47):
The champagne moment wasreally unveiling the image
and it's a very important distinction
because even though wehad this great result
and we were convinced it was right,
we spent another six monthsdoing everything we could
to make that ring go away.
Because if you're going to come
with a great result like that,

(52:07):
you have to be your own worst critic.
So, we tried to model it withtwo bright sources on the sky.
We tried to model it with afilled disc with no shadow.
We tried to model itwith elliptical rings,
not circular rings.
We did everything we couldto fit the data in a way
that would not havecorroborated Einstein's theory.

(52:28):
And it was only after wehad ruled everything out
with high statistical significance,
then we realized that we had something
that all astronomers, all physicists,
everybody would look at and agree,
this is a very robust result.
It's an amazingly importantand indispensable part

(52:49):
of the scientific process,
being your own worst critic,
because you will fool yourself.
You are the easiest person to fool.
So, splitting us up intoteams, red teaming this
over the course of six months,
that's what gave us confidence.
And then I would say even then waiting
until we had Sag A star,
waiting until a completelydifferent object

(53:11):
in a different part of the sky,
different mass, alsoshowed this ring structure,
that now has beyond any doubt showed us
that the Event Horizon Telescope
has seen what Einsteinpredicted 100 years ago.
- Is there any limit inthe Next Generation EHT,
or the Event Horizon Explorer?

(53:32):
Could you see other blackholes beside Sag A star and M87
or is there a limit to theresolution that you can get?
- So, there are two ways we might increase
the number of sources
for which we can image the event horizon.
So, one is that we'll be ableto go deeper in sensitivity.
So, there are some sources out there,

(53:53):
we just need to find themand they might even be as big
as Sagittarius A star, as big as M87,
but they're too faintright now for us to see.
So, by increasing the bandwidth,
increasing the size of our telescopes,
we may be able to see those.
Okay, that's one areathat we're examining.
And with the Next GenerationEvent Horizon telescope,
we are predicting that wewould see at least a few more

(54:16):
of these super massive black holes.
One of the postdocs working in our group,
or he was a postdoc,now he's a staff member,
Dom Peche, has gone through
very detailed calculations showing
that we are likely to seeat least a few more with
the Next GenerationEvent Horizon telescope.
The other possibility isthat we could increase

(54:36):
the angular resolution.
And we know there aresome sources right now
that we can see with theEHT that are very bright,
that were sensitive enough to see already,
but we don't have the angular resolution
to see all the way to the event horizon.
And by going to higher frequencies,
let's say to 345 gigahertz,maybe even 450, dare I say it,

(54:57):
690, we're dreaming, right?
If you did that, then evenfrom the surface of the planet,
you'd have enough angular resolution
to zoom in on some of thesources we are already looking at
to potentially see these eventhorizon scale structures.
So, we're coming at this froma number of different angles,
from sensitivity, angular resolution,

(55:18):
on the planet, in space.
Everything is geared towardsgiving us better images
of the sources we currently have
and increasing the number of sources
for which we can do this.
- You have mentioned that these projects
are huge team efforts,
and I know we have a lot of students
that listen to this podcast.
So, can you speak tothe role that students
and early career scientists play

(55:40):
in these big team collaborations?
- It is so important to talk about this.
This is not a bunch of expertswho have long been working
on this for their entire careers,
alone, bringing this result.
In fact, it's the early career people.
It's the undergraduatestudents, the graduate students,

(56:02):
the postdocs, the early career scientists
who have put the energy
that's required into thisproject to make it succeed.
And I would go so far as to say
that we would not have succeeded
if we had not created an environment
that made it comfortable for all
of these early career students
to dedicate a big portionof their lives to this.

(56:23):
It's one thing to have this idea early on,
it's a completely differentnotion to work 24/7
and to dedicate yourselvesas a young person to this.
It was the early careerastronomers that allowed us
to succeed in this.
So, to all the students out there,
to the early career people,
there is absolutely a placefor you to make substantial,

(56:47):
even formative contributionsto these kinds of projects.
So get involved,
find something that otherpeople aren't working on,
throw yourself into it.
It will always be of great value.
I can't stress that enough.
- Well, on the topic of students,
there's another question here.
This one's from Reba and it'sabout general relativity,

(57:08):
which has come up earlierand hoping we can talk
a bit more about it.
But Reba, take it away.
- Hi, my name is Reba from grade eight,
and does Einstein's theory of relativity
work near a black hole?
- Wow, so Reba, that isexactly one of the questions
that we set out to answer withthe Event Horizon Telescope.
So, the answer is we don't know for sure.

(57:29):
With theories like this,
you can only make everbetter measurements.
And what I would say is that we know
that Einstein's theory has to break down.
I said it.
Okay?
The reason is that we do notyet have a way of understanding
how the quantum world andgeneral relativity merge.

(57:50):
And we know that somewhereinside the black hole,
this has to happen becauseinside the black hole,
once you go through the event horizon,
things get so dense andthe gravity is so strong
that gravity and the quantum world merge.
Okay?
So, we know there has to bea new theory that will emerge
inside the black hole.
We are testing for Einstein's theory,

(58:13):
we are testing the validityof Einstein's theory
around the black hole.
Currently, all the measurements we've made
with the Event Horizon Telescope
are consistent with general relativity.
So, we have made these black holes,
these super massive black holes,
the most extremelaboratories in the universe.
And we are testing Einstein'stheory in these laboratories.

(58:35):
So far, those theories arepassing all of our tests,
but as we get betterand better observations,
as we get more precision,
we'll be able to test it even more.
Now, whether or not we'll find
that Einstein's theory breaks down outside
the event horizon, whichis all we have access to,
that's an open question.
There are some theories thatmodify Einstein's gravity

(58:58):
and we might be able to see some effects.
So that's what I impels us,
that's what motivates us tomake better and better images
using the Event Horizon Telescope
or the Event Horizon Explorer.
Reba, we're on the job.
That's what I can tell you.
We're moving in thatdirection and we don't know
where we're going,
but we know that we're gonna get better
and better estimates.

(59:19):
- There's actually one morestudent question that I'd love
to hear your response to.
This one is from Vera.
- Hi, my name is Vera from grade eight,
and I was wondering if we couldlive inside of a black hole
or if it's even possible?
- Wow.
Okay, so that is also avery interesting question.

(59:40):
Once you fall into the black hole,
something very interesting happens.
You know, the time axisand the spatial axis flip.
So, there's no way youcan escape the black hole.
And in fact,
any path you're on moves you closer
to the center of the black hole.
So in a finite amount of time,
you will reach the centerand you will be ripped apart.

(01:00:03):
- Ah, okay.
- So, you could live inside a black hole
for a while probably, butit wouldn't be forever.
As an example,
if you pass through theevent horizon of M87,
you wouldn't be ripped apart
because the differential gravity
between your feet andyour head is minuscule.
So, you would go through the event horizon

(01:00:24):
and you would still be, ifyour friend went with you,
you'd be chatting with them,
you'd be able to havea cup of tea, you know,
but you would be inexorablyfalling to the center.
There's no way you could backout at that point, right?
So you could have a little vacation maybe,
but you're not gonna bespending a lot of time
before you zoom into the centerand truly are ripped apart.

(01:00:46):
- It's a one-way ticket.
- It's a one-way ticket.
Now, there are ways ofviewing the universe.
I mean, there are somepeople and some formulations
that describe the Big Bang as a black hole
and that we are kind ofinside of a black hole.
So, there's a way in which wecould potentially be living
inside a space time that'sequivalent to a black hole,

(01:01:08):
that's more theoretical.
But, if you think aboutjust about falling into
a black hole, you'd haveonly a finite amount
of time to enjoy yourself.
- And you wouldn't be able totell anybody what it was like.
- And you couldn't, yeah, nopostcards from that vacation.
- Right.
You spoke about the nextstages of the EHT and the NGEHT
as making movies of a blackhole instead of still images.

(01:01:29):
And I have to ask, whenyou mentioned movies,
has Hollywood ever gottena black hole right?
- So first of all,
I love a good sci-fi movieand really astronomers
and physicists I think love to see
what Hollywood's gonna come up with next
when they depict a black hole.
I guess the closest truedepiction of a black hole
came with "Interstellar"because, of course,
they had Kip Thorne who's,you know, won the Nobel Prize

(01:01:53):
for gravitational wavesconsulting on that movie.
And they got it just aboutright for a very particular kind
of black hole.
So, the kind of black hole they showed
in "Interstellar" has a thindisc orbiting the black hole
and it's lens over thetop and on the bottom.
So, you wind up seeingthis kind of iconic ring

(01:02:14):
with a line drawn through it.
But when I talked toKip, I said, "You know,
that's not quite right."
And he said, "I know, right?"
So, Kip knows that therewas a problem with this
because when you're looking at it,
part of the emission shouldbe coming towards you
near the speed of light,
and part of it shouldbe going away from you.
So, that disc part ofit's coming towards you,

(01:02:36):
like this side is coming towards you,
this part is going away from you.
So, part of it should be muchbrighter than the other part.
The part that's coming towardsyou is Doppler boosted,
kind of in the same way thata train whistle is higher
in pitch as it's coming towards you
and it's lower in pitch asit's going away from you.
One side, the sidethat's coming towards you
should be brighter around a black hole.
And the part going awayfrom you should be dimmer.

(01:02:58):
And in "Interstellar,"
they didn't do that becauseI think they thought
that the public in thetheater would not be able
to appreciate why that was the case.
So, they made it uniformlybright all around.
So, have they gottenit right in Hollywood?
I think they've donea lot of things right,
but sometimes just for cinema,they cut a couple of corners.

(01:03:19):
- Was science fiction yourfirst introduction to the idea
of black holes, or wasscience your introduction?
- Well, my first introductionwas my father Nels Doelman.
He was a high school science teacher.
I remember him tellingme about X-ray binaries,
like Cygnus X-1,
which was one of the firstpossible black holes.

(01:03:42):
And he had some booksin the library at home
on general relativity.
And he's a very curious person,
and I had great conversations with him
and that got me thinking about black holes
and not really in an academic sense,
but just knowing they wereout there and understanding
that these kinds of things existed.

(01:04:02):
And that's a very nice memory.
And then thinking aboutscience fiction, of course,
then you start to think about, you know,
stories you've read andstories about neutron stars,
about black holes.
I mean, there have been somegreat failures, frankly,
there were some depictionsof black holes as portals
to like, hell, or thingslike this, which got very,

(01:04:23):
very scary for me as a young kid.
And I think when thingsgo in that direction,
it gets problematicbecause you can mix a lot
of different emotions with a black hole.
In truth, I think that'spart of their power.
I mean, you can imbuethem with like cultural,
even like religious meaning,
and that's because they aresuch strange objects, right?

(01:04:47):
So, it's part of the whole package.
They're very powerful,
they're very meaningful andyou can ascribe to them a lot
of different attributes and that's part
of what makes them so compelling.
- So, on the topic of how youwent from someone interested
in some of these topics todoing them for a career,
Avery Broderick told us thatwe had to ask you of some

(01:05:09):
of your earlier experiences.
I think after you finishedyour undergraduate degree,
you spent some time in Antarctica.
Could you tell us a little bit about this?
- Oh yeah, I did.
When was that?
So in 1986, I graduatedfrom undergraduate.
I went to Reed Collegeand studied physics there.
And I was a little bitburned out at the time.

(01:05:31):
Many people leave undergraduateand they're like, wow,
that was intense, and that's how I felt.
And I saw a poster when I wasthinking about what to do next
for a program wherepeople went to Antarctica
to look after all the experiments
that were set up there for astronomy.
And so, I applied for thatand I got the position
and I wound up going toAntarctica for a year.

(01:05:53):
I lived at McMurdo Base onthe coast of Antarctica.
I also went to the South Polea few times to help set up
some equipment there.
And that gave me a reallyinteresting perspective
in a couple of ways.
It showed me that you coulddo really interesting science
at remote sites in verydifficult circumstances

(01:06:13):
and what it took to do it.
And I kind of fell in lovewith the swashbuckling aspect
of doing science, you know,going to a difficult place,
making it work.
And that has colored my entire career.
It also taught me how to dealwith a lot of different people
because in Antarctica youhad this very interesting mix

(01:06:34):
of the Navy, which took careof a lot of the construction
and the meteorology and someof the day-to-day comforts
at the base at McMurdo.
You had the Air Force, whichwas doing all the flights in.
You had construction workers
who were building new dormitories
and helping withconstruction of laboratories.

(01:06:56):
And you also had thescientists funded primarily
by the National ScienceFoundation at those sites.
And I got my first taste ofseeing how different communities
work together and thateach community plays
a very vital role.
And you can't just be a scientistin that remote location.
You can't just be someoneinvolved with construction.

(01:07:16):
You can't just be in the military.
You need to find a way foreveryone to work together
to make that base function.
And if you wanna do sciencein that environment,
you need to work with alot of different people.
So in addition toworking in a remote site,
it also taught me how to deal with people.
And that has helped, as you might imagine.

(01:07:37):
- That's funny, to learnhow to deal with people,
you go to the continent thathas the fewest people on Earth,
but they're all workingtoward a sort of common goal?
- Well, that's a very interesting point.
Often it is in these extreme environments
where people come together,it's not an accident.
When you're just happy and you're content,

(01:07:58):
you make friends and youare often with people
who believe the way you do.
You're often with peoplewho think the way you do.
Maybe even at work,
you're with people most of theday who do the things you do.
But it's when you goto a unique environment
and you are focused on avery interesting mission
that requires many people come together,

(01:08:19):
that's where you really needto broaden your perspective.
So it's in these extreme environments,
it's in these experiments
where you've gotta havepeople coming together.
And coming back to somethingthat we talked about before,
if we're gonna address the big problems
that face us as humanity,
we're going to have to come together.

(01:08:40):
Solving a problem like climate change
is not gonna happen because a bunch
of scientists get together.
It's gonna happen because industry,
politics, science, the generalpublic, even like cultural,
religious leaders, allcome together and realize
this is a problem that faces everyone.
So it's in these extreme environments,

(01:09:02):
it's in these turning point problems
that face us as a planet.
This is where peoplehave to come together.
So, I don't think it's an accident.
I think it's almost by designthat we're thrown together
in these unique moments.
- And when we do face suchterrestrial challenges
of climate change andpolitics and everything else,

(01:09:22):
why is it important forus to look at black holes,
millions of light years away,
that won't necessarilyaffect our day-to-day lives?
- So, it's a really interesting point.
We have so many things facing us now,
why pay attention to M87?
Why look at the centerof the Milky Way Galaxy?
The best answer I have is that you need

(01:09:43):
to play the long game inany financial portfolio.
So, this will make senseto people who are saving
for retirement and things like this.
You need to have your blue chip stocks,
which are going to do well over time.
You also wanna have somemore high risk element
of your portfolio.
Like any normal financialmanager will tell you this.

(01:10:05):
And it's the same thing with science.
It's the same thing with business.
It's the same thing with really humanity.
You need always to payattention to the here and now.
You need to pay attentionto what's in front of you.
Part of you needs to bethinking about the future
and sometimes the far futureand investing in basic research
that doesn't necessarily pay off tomorrow

(01:10:26):
is never a bad idea.
It always pays off inthe long run, always.
And I think more than that,
it speaks to the human condition
because we're conditioned nowto think about the news cycle.
Every Tuesday something happens.
And if it's not thisTuesday, you forget about it.
We are used to thinking aboutthe quarterly bottom line,

(01:10:47):
how is my company doingand how will I report
to the shareholders?
We're thinking aboutthe next election cycle.
A couple of years down the road,
who will be leading the country
and what kind of politicsshould we be dealing with?
Science and the pursuit of basic research
is the deep rudder in the water.
It is the long game that we play.

(01:11:09):
It is what connects us acrossthe centuries to the thinkers
that came before us.
It's really what defines humanity.
We are not what happens this week.
We are what happens over centuries.
We are what happens over millennia.
We are building the history
that people will lookback on later and say,
"These people were thinking

(01:11:30):
about the deepestmysteries of the universe."
If you went back and talkedto Einstein and you could go
in a time machine and say, "Einstein,
100 years from now you'llbe able to use your phone.
And using a constellation of satellites,
you'll be able to pinpoint your location
on the earth using your theories."
As I like to say, he'd be very excited,

(01:11:51):
but of course he wouldjust say, "What's a phone?"
Right?
Because it's so far beyond his conception.
He didn't even know whatphones were back then, right?
So, he didn't realize that unless
you make general relativistic corrections
to the GPS system that we all rely on
to get us from point Ato point B in our cars,

(01:12:13):
if you don't make thosecorrections, you're off by miles.
But, he never could have known that.
So, we are making the discoveriestoday with basic research
that are not gonna pay off
until maybe 100 years from now.
But we'll look back and say, "Ah,
that was so important to think about."
And I will add one more thing.
If you only look at the things you know,

(01:12:34):
if you only try to make the ideas
that you currently understand better,
then you're doing engineering.
And engineering is amazing.
I consider myself to be an engineer.
In fact, my job title isengineer and I love it.
But if you limit yourself to engineering
what you already know,
then you're missing out on the new ideas.

(01:12:57):
So, you need to be askingthese big questions.
You need to be lookingat M87 and Sag A star
because they will leadyou in the directions
that you have no idea about now.
And many of those will not pay off,
but the ones that dowill be truly new windows
on the universe.
And that's what humanity Ithink should be focused on.

(01:13:17):
- Well, I think that's abeautiful sentiment to wrap up on.
Shep, thank you so muchfor this conversation.
- It was a real pleasure.
Thank you both.
- Thanks for steppinginside the "Perimeter."
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(01:13:39):
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