Inside the black hole image that made history | Sheperd Doeleman


Chris Anderson: Shep,
thank you so much for coming. I think your plane landed
literally two hours ago in Vancouver. Such a treat to have you. So, talk us through how do you get
from Einstein’s equation to a black hole? Sheperd Doeleman: Over 100 years ago, Einstein came up with this
geometric theory of gravity which deforms space-time. So, matter deforms space-time, and then space-time tells matter in turn
how to move around it. And you can get enough matter
into a small enough region that it punctures space-time, and that even light can’t escape, the force of gravity
keeps even light inside. CA: And so, before that,
the reason the Earth moves around the Sun is not because the Sun
is pulling the Earth as we think, but it’s literally changed
the shape of space so that we just
sort of fall around the Sun. SD: Exactly, the geometry of space-time tells the Earth
how to move around the Sun. You’re almost seeing a black hole
puncture through space-time, and when it goes so deeply in, then there’s a point at which
light orbits the black hole. CA: And so that’s, I guess,
is what’s happening here. This is not an image, this is a computer simulation
of what we always thought, like, the event horizon
around the black hole. SD: Until last week, we had no idea
what a black hole really looked like. The best we could do were simulations
like this in supercomputers, but even here you see this ring of light, which is the orbit of photons. That’s where photons
literally move around the black hole, and around that is this hot gas
that’s drawn to the black hole, and it’s hot because of friction. All this gas is trying to get
into a very small volume, so it heats up. CA: A few years ago,
you embarked on this mission to try and actually image
one of these things. And I guess you took — you focused on this galaxy way out there. Tell us about this galaxy. SD: This is the galaxy — we’re going to zoom into the galaxy M87,
it’s 55 million light-years away. CA: Fifty-five million. SD: Which is a long way. And at its heart, there’s a six-and-a-half-billion-
solar-mass black hole. That’s hard for us
to really fathom, right? Six and a half billion suns
compressed into a single point. And it’s governing some of the energetics
of the center of this galaxy. CA: But even though that thing is so huge,
because it’s so far away, to actually dream
of getting an image of it, that’s incredibly hard. The resolution would be incredible
that you need. SD: Black holes are the smallest
objects in the known universe. But they have these outsize effects
on whole galaxies. But to see one, you would need to build a telescope
as large as the Earth, because the black hole
that we’re looking at gives off copious radio waves. It’s emitting all the time. CA: And that’s exactly what you did. SD: Exactly. What you’re seeing here is we used telescopes
all around the world, we synchronized them perfectly
with atomic clocks, so they received the light waves
from this black hole, and then we stitched all of that data
together to make an image. CA: To do that the weather had to be right in all of those locations
at the same time, so you could actually get a clear view. SD: We had to get lucky
in a lot of different ways. And sometimes, it’s better
to be lucky than good. In this case, we were both,
I like to think. But light had to come from the black hole. It had to come
through intergalactic space, through the Earth’s atmosphere,
where water vapor can absorb it, and everything worked out perfectly, the size of the Earth
at that wavelength of light, one millimeter wavelength, was just right to resolve that black hole,
55 million light-years away. The universe was telling us what to do. CA: So you started capturing
huge amounts of data. I think this is like half the data
from just one telescope. SD: Yeah, this is one of the members
of our team, Lindy Blackburn, and he’s sitting with half the data recorded at the Large
Millimeter Telescope, which is atop a 15,000-foot
mountain in Mexico. And what he’s holding there
is about half a petabyte. Which, to put it in terms
that we might understand, it’s about 5,000 people’s
lifetime selfie budget. (Laughter) CA: It’s a lot of data. So this was all shipped,
you couldn’t send this over the internet. All this data was shipped to one place and the massive computer effort began
to try and analyze it. And you didn’t really know what you were going to see
coming out of this. SD: The way this technique
works that we used — imagine taking an optical mirror
and smashing it and putting all the shards
in different places. The way a normal mirror works is the light rays bounce
off the surface, which is perfect, and they focus in a certain point
at the same time. We take all these recordings, and with atomic clock precision we align them perfectly,
later in a supercomputer. And we recreate
kind of an Earth-sized lens. And the only way to do that
is to bring the data back by plane. You can’t beat the bandwidth
of a 747 filled with hard discs. (Laughter) CA: And so, I guess a few weeks
or a few months ago, on a computer screen somewhere, this started to come into view. This moment. SD: Well, it took a long time. CA: I mean, look at this. That was it. That was the first image. (Applause) So tell us what
we’re really looking at there. SD: I still love it. (Laughter) So what you’re seeing
is that last orbit of photons. You’re seeing Einstein’s
geometry laid bare. The puncture in space-time is so deep that light moves around in orbit, so that light behind the black hole,
as I think we’ll see soon, moves around and comes to us
on these parallel lines at exactly that orbit. It turns out, that orbit is
the square root of 27 times just a handful
of fundamental constants. It’s extraordinary
when you think about it. CA: When … In my head, initially,
when I thought of black holes, I’m thinking that is the event horizon, there’s lots of matter and light
whirling around in that shape. But it’s actually
more complicated than that. Well, talk us through this animation,
because it’s light being lensed around it. SD: You’ll see here that some light
from behind it gets lensed, and some light does a loop-the-loop
around the entire orbit of the black hole. But when you get enough light from all this hot gas
swirling around the black hole, then you wind up seeing
all of these light rays come together on this screen, which is a stand-in
for where you and I are. And you see the definition of this ring
begin to come into shape. And that’s what Einstein predicted
over 100 years ago. CA: Yeah, that is amazing. So tell us more about
what we’re actually looking at here. First of all, why is part of it
brighter than the rest? SD: So what’s happening
is that the black hole is spinning. And you wind up with some of the gas
moving towards us below and receding from us on the top. And just as the train whistle
has a higher pitch when it’s coming towards you, there’s more energy from the gas
coming towards us than going away from us. You see the bottom part brighter because the light is actually
being boosted in our direction. CA: And how physically big is that? SD: Our entire solar system
would fit well within that dark region. And if I may, that dark region is the signature
of the event horizon. The reason we don’t see light from there, is that the light that would come
to us from that place was swallowed by the event horizon. So that — that’s it. CA: And so when we think of a black hole, you think of these huge rays
jetting out of it, which are pointed
directly in our direction. Why don’t we see them? SD: This is a very powerful black hole. Not by universal standards,
it’s still powerful, and from the north and south poles
of this black hole we think that jets are coming. Now, we’re too close
to really see all the jet structure, but it’s the base of those jets
that are illuminating the space-time. And that’s what’s being bent
around the black hole. CA: And if you were in a spaceship
whirling around that thing somehow, how long would it take
to actually go around it? SD: First, I would give anything
to be in that spaceship. (Laughter) Sign me up. There’s something called the —
if I can get wonky for one moment — the innermost stable circular orbit, that’s the innermost orbit at which
matter can move around a black hole before it spirals in. And for this black hole, it’s going to be
between three days and about a month. CA: It’s so powerful,
it’s weirdly slow at one level. I mean, you wouldn’t even notice falling into that event horizon
if you were there. SD: So you may have heard
of “spaghettification,” where you fall into a black hole and the gravitational field on your feet
is much stronger than on your head, so you’re ripped apart. This black hole is so big that you’re not going to become
a spaghetti noodle. You’re just going to drift
right through that event horizon. CA: So, it’s like a giant tornado. When Dorothy was whipped by a tornado,
she ended up in Oz. Where do you end up
if you fall into a black hole? (Laughter) SD: Vancouver. (Laughter) CA: Oh, my God. (Applause) It’s the red circle, that’s terrifying. No, really. SD: Black holes really are
the central mystery of our age, because that’s where the quantum world
and the gravitational world come together. What’s inside is a singularity. And that’s where
all the forces become unified, because gravity finally is strong enough
to compete with all the other forces. But it’s hidden from us, the universe has cloaked it
in the ultimate invisibility cloak. So we don’t know what happens in there. CA: So there’s a smaller one of these
in our own galaxy. Can we go back
to our own beautiful galaxy? This is the Milky Way, this is home. And somewhere in the middle of that
there’s another one, which you’re trying to find as well. SD: We already know it’s there,
and we’ve already taken data on it. And we’re working on those data right now. So we hope to have something
in the near future, I can’t say when. CA: It’s way closer
but also a lot smaller, maybe the similar kind of size
to what we saw? SD: Right. So it turns out
that the black hole in M87, that we saw before, is six and a half billion solar masses. But it’s so far away
that it appears a certain size. The black hole in the center of our galaxy
is a thousand times less massive, but also a thousand times closer. So it looks the same
angular size on the sky. CA: Finally, I guess,
a nod to a remarkable group of people. Who are these guys? SD: So these are only some of the team. We marveled at the resonance
that this image has had. If you told me that it would be
above the fold in all of these newspapers, I’m not sure I would
have believed you, but it was. Because this is a great mystery, and it’s inspiring for us,
and I hope it’s inspiring to everyone. But the more important thing is that
this is just a small number of the team. We’re 200 people strong with 60 institutes and 20 countries and regions. If you want to build a global telescope
you need a global team. And this technique that we use
of linking telescopes around the world kind of effortlessly sidesteps
some of the issues that divide us. And as scientists, we naturally
come together to do something like this. CA: Wow, boy, that’s inspiring
for our whole team this week. Shep, thank you so much for what you did
and for coming here. SD: Thank you. (Applause)

Comments 100

  • Einstein did not predict it.  His E=MC^2 allowed for it to exist.  A young German astronomer named Swartzchild sent Einstein his equations created along the western front.  Einstein was so intrigued he responded, but he always say this black hole thing just doesn't smell right.  Swartzchild was killed a few weeks later.   Lost to History.  He is the man who predicted the Black Hole… get it right!

  • 9:15 -By Standing on The Shoulders of (red)Giants 😀

  • Does a present generation understand that the universe is made of LIGHT, and made of light all central systems?

  • Can anyone explain to me why they can't take a picture of a blackhole in the Andromeda Galaxy 2 million LY away, and can see a blackhole 55 million LY away?

  • Hey, look white male blowhard stealing Katie Bouman's thunder. Piss off.

  • Some alien somewhere is shaking his head like "Aaaahh those Earth people, they finally got something. I fly near that black hole every weekend." 😁

  • For anyone who hasnt seen Ted yet:
    hes still on top of Skylar.

  • A dark soul

  • Scientist: here's what the inside of a black hole looks like huehuehueharhue

    Me: cool, but tell me what's at the very bottom of OUR ocean. The one that's on OUR home planet.

    Scientist: …look! A supernova!

    Me: but what about-

    Scientist: A SuPErNoVa!!!!!!

  • The speaker explains really well.

  • They spend billions of dollars for just ah orange flavore donut,

  • With that super telescope, I wonder how planets would look from earth.

  • I started to think that The Movie Interstellar is Amazing.
    If you haven't watched it ,I suggest you should.

  • I dont understand a thing about how that light is created around the black whole??? Anybody wants to put energy into explaining it to me?

  • the biggest black hole that there is is right here on earth its called NASA money just gets sucked into that place and gone

  • Hot gas is emmitted from the famous brown hole in Dallas

  • Einstein predict the black hole exist before scientist can really see them. I cannot even predict the ending of Endgame 🙄

  • Anybody know what’s inside Uranus?

  • its not a blackhole image its the light around it

  • Believe it or not
    Black panther gets his superpower from black hole

  • Is a black hole three dimensional? Is it a ball or a tube? If it were a tube, wouldn’t we be able to see a linear effect on light as well as a singular point in space? Does that make sense?

  • One eyed smiley

  • Shows how far we've really came from looking at lame mars pictures to seeing a black hole.

  • Great people! Thank you for letting me see black hole in my life !

  • This is my first time ever seeing a BLACK HOLE. Thanks.

  • Ok so it looks like the computer simulation they showed a few minutes before.

  • check out theoria apophasis on youtube to find out what a black hole is ! Einstein was an idiot !

  • Mother

  • I did a project on Balck Holes.

  • That looks more like Uranus

  • you want your mind blown? what if we could never stop falling in a black hole as time gets comprimized so dense that it runs infinitly slow at its center. and what if we are in an never ending but just scaling infinit big bang which has no start and no end.

  • Humans they think they are the center of the universe they think they are the only one who have been made by gods image they think that the tehnology its good no actuali it makes life better till 2080 after that its difrent thwy just realized that they did a mistake they tought that the tehnology was part of the evolution process for humanity but it wasnt i didmt came here to give just a random opinion in random time just for some random guy to read it i came here for

  • So we are supposed to believe that this is a black hole based on what empirical evidence?

  • So the universe is…flat??

  • Lol orange donut. Obviously glazed. Dumb-dumb-dumb are the minds of men

  • Reading all these comments is Interesting,,,,,,
    YouTube is totally just Entertainment,,,,its Informative at its basic level but yet just still Entertainment !
    One commentor says,,,it took 200 people and many COUNTRYS joined together to get this info on the Black HOLE,
    wouldn't it be GREAT if everyone in the world could work to gather to SOLVE THE PROBLEMS on our own planet ????
    Great questions,,,,I see 3 main problems with achieving that goal,,,,
    MONEY,,POWER AND GREED !!!!! that's it !
    AS FUNNY AS IT MAY SEEM the DIAGRAM for that type of "COUNTRYS AND PEOPLE WORKING TOGETHER" TO SOLVE THE WORLDS PROBLEMS IS ON YOUR T.V. ????
    STAR TREK ? everyone in the world WORKS FOR THE COMMON GOOD,,,,,WITHOUT MONEY ? NO PAYCHECKS,,,NO MONEY !
    A REPLICATOR PROVIDES EVERYTHING YOU NEED TO LIVE !
    EVERYONE HAS A NICE PLACE TO LIVE AND NO NEED FOR A CAR BECAUSE EVERYONE HAS THE USE OF TRANSPERTATION WHEN THEY NEED IT,,,
    OH AND LETS NOT FORGET THE " TRANSPORTER " !!!!!
    BUTT ,,,,,,,,,,THEY STILL HAVE WEAPONS IN THE FUTURE ,,,,,,,BUT ONLY TO PROTECT AGAINST THE GREEDY ALIENS!

  • I wish someone would do a TED on what happens to all of my socks.

  • Glad I clicked this video now blackholes are a considerablely less scary now

  • Maybe black holes can take out trashes

  • Why the masses are so stupid? That guy is full of it all the way. Why is no body ask him, how matter deforms space-time? How space-time in turn tells matter how to move around?

  • If anybody's is wondering half a petabyte is five hundred thousand gigabytes or five hundred million megabytes

  • Either one of them couldve come up pn stage and do this talk. The interviewer obviously knows the answer to his own leading questions 😂

  • Very inspiring!

  • Never thought that this is the only original picture of black hole we have but Einstein laid out the mathematics 100 years ago

  • Let's hurl Trump into it

  • That old guy kinda sounds like Bruno

  • 6:18 Most important, rarest, & most necessary animation ever!! THIS is what I needed to see to understand what we're looking at.

  • Imagination is key to understanding what's beyond conception within this dimension.Einstein wasn't a genius…he was BEING human infant,child, adolescent,adult.He employed his childlike imagination with an adult perspective and maturity and sensed truth that couldn't be spoken but felt.

  • Looks like a ring of fire to me

  • It’s the eye of a galactic beast.

  • THIS IS OSCAR !!!!!!

  • What a beautiful mind and a perfect talker..

  • I have a black hole and it looks nothing like what is on this video.

  • What if dark matter is on the other side of black holes

  • Litteraly our scientific laws are not enough to describe all the activities of this gigantic cosmic arena. May be there is no explanation behind all these phenomenon.

  • Great video, vary informative and a beautiful ending too 💫

  • Setting aside political boundaries in a mission to seek for truth.

  • Hehe great video, but I do think the scientist would have done just fine on his own 🙂

  • Albert Einstein Now Believes In The PERSONAL GOD, The LORD GOD & TRUE JESUS CHRIST, CREATOR and OWNER Of ALL THINGS, Including CREATOR & OWNER of Albert Einstein's Soul, Since Einstein NOW SEES The LORD GOD & TRUE CHRIST FACE TO FACE! ;-)***1 CORINTHIANS 13:12, FOR NOW We SEE THROUGH a GLASS, DARKLY (NOW IT IS HARD TO SEE THROUGH a DARK GLASS CLEARLY); BUT THEN FACE TO FACE: NOW I KNOW IN PART; BUT THEN (WHEN You COME FACE TO FACE WITH The LORD GOD & TRUE JESUS CHRIST) SHALL I KNOW EVEN AS ALSO I AM KNOWN!**2 CORINTHIANS 5:1, 8 FOR We KNOW THAT IF Our EARTHLY HOUSE (FLESH BODY) Of THIS TABERNACLE (FLESH BODY) WERE DISSOVED (DIED), We HAVE a BUILDING Of GOD (HEAVENLY SPIRIT BODY FROM The LORD GOD), AN HOUSE (BODY) NOT MADE WITH HANDS (NOT MADE WITH EARTHLY HANDS), ETERNAL IN The HEAVENS!**8, We ARE CONFIDENT, I SAY, and WILLING RATHER TO BE ABSENT FROM The BODY (FLESH BODY), and TO BE PRESENT WITH The LORD!***We WILL ALL SEE The LORD GOD & TRUE JESUS CHRIST FACE TO FACE, IN Our APPOINTED TIME, and THEN WILL We SEE THINGS & TRUTH MORE CLEARLY, and We WILL KNOW EVEN AS ALSO We ARE KNOWN BY The LORD GOD & TRUE CHRIST!**And SOME PEOPLE MAY NOT BELIEVE THIS NOW, BUT They WILL BELIEVE IT WHEN They SEE IT COME TO PASS FOR Themselves!

  • Incredible video!

  • does he talks like ellon musk

  • My Mrs has a black hole that's totally inaccessible i think id be torn apart trying to enter it aswell

  • My question for life is why are there so many planets if earth is the only inhabitable one

  • This comment is 57 millions years old too like it now

  • The standard of questions is too pathetic.
    Why is he even required to be there and ask the questions ?

  • This is the funniest video in youtube history!

  • i wanna know if Shepard played mass effect .

  • the great attractor

  • Bible stories seem kinda boring next to this.
    RIP Christopher Hitchens.

  • Someone call Eddie Bravo here.

  • He helped me understand that on a whole other level!

  • Finally they caught an eclipse in another galaxy

  • How utterly gullible everyone is; https://youtu.be/kI14fpM3ouU TED is where academia comes to stroke itself until it grants.

  • This is so full of crap. Human technology can not get data from that far away. Period. It’s all deception

  • Einstein predicted 100 years ago of black hole now his discovery became true🙏🙏🙏😍😍😍

  • Incorrect: https://www.youtube.com/watch?v=kI14fpM3ouU

  • The entire solar system can fit in that black area…. Wow how massive 😮 that black hole is……..

  • How can you be so gullible? You are meant, as a scientist, to be using your mind. Not regurgitating concepts you pretend to understand. Its mathematical voodoo, and it has cast a spell on you, reducing you to blithering idiots. Let go of this circular argument.

  • They just went on, but I kept wondering: our whole Solar System could fit into that black hole. I mean we need months to years to reach other planets in our Solar System. Falling into that black hole would be a long fall indeed.

  • Like moon landing by nasa is being said fake..might be uts alos fake coz..its beyound human beings imagination

  • In quran allah said about this about 1500 yrs ago..

  • This is a modelled picture not an actual picture. Oh and where is the pier review?

  • Ok now time to go watch interstellar again.

  • So instead of studying the BLACK HOLE in our own milky way they decided to look for a BLACK HOLE which is 55 millions light years away 🤔

  • 500 billion tons of mass would need to be squeezed and compacted to the size of table tea spoon 🥄 ⭕️ or pupil of and eye 👁 to just start opening a black hole 🕳.

    2 Chronicles 16

    7At that time Hanani the seer came to Asa king of Judah and said to him: “Because you relied on the king of Aram and not on the Lord your God, the army of the king of Aram has escaped from your hand. 8Were not the Cushites b and Libyans a mighty army with great numbers of chariots and horsemen c ? Yet when you relied on the Lord, he delivered them into your hand.

    9For the eyes of the Lord range throughout the earth to strengthen those whose hearts are fully committed to him.

    You have done a foolish thing, and from now on you will be at war.”

    10Asa was angry with the seer because of this; he was so enraged that he put him in prison. At the same time Asa brutally oppressed some of the people.

    11The events of Asa’s reign, from beginning to end, are written in the book of the kings of Judah and Israel. 12In the thirty-ninth year of his reign Asa was afflicted with a disease in his feet. Though his disease was severe, even in his illness he did not seek help from the Lord, but only from the physicians. 13Then in the forty-first year of his reign Asa died and rested with his ancestors. 14They buried him in the tomb that he had cut out for himself in the City of David. They laid him on a bier covered with spices and various blended perfumes, and they made a huge fire in his honor.

    Ephesians 6:12 New International Version (NIV)

    12 For our struggle is not against flesh and blood, but against the rulers, against the authorities, against the powers of this dark world and against the spiritual forces of evil in the heavenly realms.

    Galatians 5:17
    For the flesh desires what is contrary to the Spirit, and the Spirit what is contrary to the flesh. They are in conflict with each other, so that you are not to do whatever you want.

  • Is this true

  • https://m.youtube.com/watch?v=_Lp_2EG1dfk&feature=youtu.be

  • 1111

  • Love

  • Hindi dubbed please

  • This is video

  • ~New studies show how the INSIDE of a magnet represents a black hole perfectly. Remember the black hole image taken about 5 months ago? This will blow your mind. All toroidal magnets have vortex centers where nothing can go. Not even light. This guy found a way for LED lights to get caught up in the field lines of magents, and see what's going on INSIDE a Magnet. It's like a magnet Xray. Never been done before.

    https://youtu.be/-Hzvvjh3_8g

    Here's how he visually demonstrates planets being made, using magnetic putty, and a tyroidal magnet. The magnetic putty EATS the magnet, at takes it to its center. He also does a perfect representation visually demonstrating Saturn also. Perfectly.
    https://youtu.be/YZ1SaJ0–To

    A more descriptive video of magnetic fields bending light, PERFECT representation.
    https://youtu.be/w-ES78p5zfE

    Here's a video representing the magnetics of our galaxies.

    https://youtu.be/b4a77HfiRFs

    More and more of this guy's videos make sense, and fit so well into absolutely everything cosmos related. Using magnetics. Something NONE of us study, even in High School. Do they even tell tales of Tesla anymore in school? Have they ever???

    Here's some NASA footage of the STS missions in 1996. It's tether that broke off, was 12 miles long. You can use it as a cosmic ruler. Notice how ALL the objects are emitting so much energy, they pulsate. Except for the center. Where not even light can go. Theres no other reasons for that to show up as a cold spot. NASA told the public these were ice particles BTW.
    https://youtu.be/JuFBUS0kiSA

    https://youtu.be/YZ1SaJ0–To

    Gravity is fake. It's effects are very much real, but it's cause is something entirely different. Our Ancient Ancestors knew this science. They knew it very well.
    We've been dooped by government funded scientists in desperate attempts to CONTINUE getting their funding. They literally created results to keeping their funding.
    Look at his explanation of galaxies. Unreal how right he is, and how simple it really is.

    Galaxies, are perfectly mimicking what's going on inside magnets

    https://youtu.be/9yi0WHKtRd4

    https://youtu.be/JuFBUS0kiSA
    Check this video out showing how pyrimid magnetics work, based on a Magent expert. And I mean, expert. Think, pyrimid of Giza.

    https://youtu.be/fO_6cZUtmWg

    here's a fun fact. 90 percent of scientists read. That's it. They read books. Government printed books by government funded scientists. If those scientists don't "produce" results, their funding stops. Theres such a SMALL amount of scientists working with real equipment to contribute to finding answers. They all work for the government.  EVERYTHING Einstein ever said, needs to be scrapped.
    Mother nature is really quite simple. And she doesn't work with numbers. And she's not some crazy cross-eyed hooker on crack with a bag of magic particles either.
    The universe, is indeed Electric. Without electricity, magentism cannot exist. Without magentism, electricity cannot exist.
    https://youtu.be/5AUA7XS0TvA
    Why not blow the whistle on subjects that would help this species build in their garages, crafts to leave this planet. Instead of building hot rods from the ground up.
    Government funded scientists are lying to us too.

  • Another funnel for taking tax dollars-NASA

  • Nope. https://youtu.be/kI14fpM3ouU

  • Imagine if the aliens in that galaxy are taking a picture of Sagittarius A

  • I am more confused

  • Interstellar (the movie) made a pretty realistic black hole and it's honestly so beautiful.

  • I wish Stephen Hawking lived to see this… https://www.youtube.com/watch?v=kI14fpM3ouU

    Even I called it the night before the image was released…"it would be a glowing doughnut with a dark center"…its called a Taurus, …Theoretical Astrophysics has become the laughing stock of the 21st century…it is the biggest joke on the planet…by this account, the earth must be flat too.

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