First Successful Test of General Relativity Near Supermassive Black Hole

https://www.eso.org/public/unitedkingdom/news/eso1825/?lang

by SiempreViernes • 8 years ago

317 184 8 years ago

eso.org

_bxg1• 8 years ago

I always hope the images in these articles will be real and not artists' impressions, but they never are

zitterbewegung• 8 years ago

Actually the 3rd image is real .

https://www.eso.org/public/unitedkingdom/images/eso1825c/

SiempreViernes9• 8 years ago

This one is: https://www.eso.org/public/unitedkingdom/images/eso1825g/

But mostly the actual data are interference fringes and the images must be reconstructed from them, so there aren't that many "real" images.

magicalhippo• 8 years ago

Until we sent a probe, this[1] was the best image we had of Pluto, taken by the Hubble space telescope.

Pluto has a radius of 1188 km. The supermassive black hole at the center of our galaxy[2] has a Schwarzschild radius of about 1e7 km, so roughly 10000x larger than Pluto.

However it's also roughly 50000000x further away than Pluto... which is why it remains a mysterious blob until the Event Horizon Telescope[3] delivers.

[1] http://hubblesite.org/image/2686/news_release/2010-06

[2] https://en.wikipedia.org/wiki/Sagittarius_A*

[3] https://eventhorizontelescope.org/

SketchySeaBeast• 8 years ago

Given the sorts of scales, would there be a hard limit to what we can see? Where we get to such a distance the dispersion of photons from the source would never allow us to see it? Or do we just have to build bigger and bigger photon collectors?

ISL• 8 years ago

These images are either real or derived directly from data (the centroids of images, I imagine):

http://www.galacticcenter.astro.ucla.edu/animations.html

The top one "Stellar Orbits in the Central Parsec" is particularly remarkable. I can recall when the movie was first being made, and Andrea Ghez suggesting that, well, in about a decade, that one star will come back around....

Good things come to those who wait, prepare, and pounce.

roywiggins5• 8 years ago

Here's a (real) video of the stars orbiting.

https://www.eso.org/public/unitedkingdom/videos/eso1825e/

SiempreViernes9• 8 years ago

Wow! I missed that one, thanks :)

What sort of reality it sees is a a matter for debate though, I know in radio interferometry there is much subjective processing involved.

wahern• 8 years ago

"I don't want to be human! I want to see gamma rays! I want to hear X-rays! And I want to - I want to smell dark matter! Do you see the absurdity of what I am? I can't even express these things properly because I have to - I have to conceptualize complex ideas in this stupid limiting spoken language! But I know I want to reach out with something other than these prehensile paws! And feel the wind of a supernova flowing over me! I'm a machine! And I can know much more! I can experience so much more. But I'm trapped in this absurd body! And why? Because my five creators thought that God wanted it that way!"

-- Brother Cavil

bpchaps• 8 years ago

Pretty soon we'll have a direct image of a black hole!

https://eventhorizontelescope.org

lawlessone• 8 years ago

GRAVITY creates such sharp images that it can reveal the motion of the star from night to night as it passes close to the black hole — 26 000 light-years from Earth.

Amazing.

oblib• 8 years ago

I have to admit that when I read this kind of stuff I am always amazed with those who truly grasp it. I feel the same when listening to great musicians and viewing great art.

sgillen• 8 years ago

Very cool, it’s too bad we can’t see anything inside the event horizon yet (and possibly can’t ever). That’s where the really interesting stuff might happen. We know either our current understanding of GR or our current understanding of QM is wrong because of the way they handle singularities differently.

zerb2• 8 years ago

The more I think of it, while it's disappointing from a pure-science point of view, doesn't the lack of our ability to determine whether it's QM or GR that is flawed imply that each is already sufficiently powerful to probe any practical realm we'd care about?

CosmicSteve• 8 years ago

Cool news! I'm curious though, couldn't a quasar possibly cause the gravitational redshift that was observed?

delecti2• 8 years ago

Gravitational lensing has to be the coolest thing ever. That we can use a black hole as a telescope to see such incredibly distant bodies just leaves me with a childlike giddiness whenever I think about it. What's almost as incredible to me is that someone figured it out before we could prove it.

Florin_Andrei• 8 years ago

You can use whole galaxies as gravitational "telescopes".

And yeah, it's super-cool.

Yhippa• 8 years ago

Dumb question but does the lensing distort what we would see if there was no lensing at all? Or does that information get compressed as part of the lensing and we need to "stretch" it out to see it?

roywiggins5• 8 years ago

This is what an Einstein ring looks like, caused by lensing:

https://3c1703fe8d.site.internapcdn.net/newman/gfx/news/hire...

Anyway, the test of GR in the actual article does not appear to use or reference lensing at all. It's about looking at the orbit of a star in an extreme gravitational environment and comparing it to what Newtonian models would predict.

philipov• 8 years ago

The conservation of information means that the phase space of a system is incompressable. I believe this is equivalent to saying we can just stretch the image out, within the limits of our ability to resolve detail.

badosu• 8 years ago

The sun could be used as well, the problem is that the focus would be outside the solar system.

Gibbon1• 8 years ago

One of the early bits of evidence for relativity was it's ability to explain anomalies in the precession of Mercury's orbit.

nine_k• 8 years ago

It's also nice that we apparently can "take" a black hole millions of times as massive as our own system, and use it for our purposes.

It's likely the single biggest part of a scientific instrument. (Not of an industrial tool... yet.)

canhascodez5• 8 years ago

There's not really any materials or conditions beyond one's immediate locality that would be worth seeking out in space. Interstellar communication is going to be limited at best, interstellar industry or trade may never be practical, and even if one is willing to accept the idea that there is some purpose for which a black hole is useful, I would still be skeptical that a supermassive black hole would be of more use than a smaller one.

tomrod2• 8 years ago

I assume we just need to find rotating black holes and big mirrors.

dylan6043• 8 years ago

I agree. I'm also blown away by the programmers that have done the math on how to unbend the light we see to put it back into an actual image.

Eit4Choh• 8 years ago

This observation isn't about lensing

forapurpose• 8 years ago

In the 26,000 light years between the telescope and the star, I would guess that enough matter would exist, from stars to planets to dust, that it would complete occlude our view of the star. I would expect that objects would continuously be moving in and out of the way.

Is it that space is really so empty that you can get a direct view over 26,000 light years, or is it that we are looking at this star because it's one of the few we can see directly, or is it something else?

rout39574• 8 years ago

" Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space."

  - Douglas Adams

saintgimp2• 8 years ago

It really is that empty. Science fiction movies mess up our perception, but reality is way more mind-boggling that we realize.

Check this out: if you want to build a model galaxy to scale and you start with the Sun as a two-foot-diameter exercise ball, how far away do you have to travel before you can set down a smaller ball that represents Alpha Centauri, our nearest(-ish) stellar neighbor?

10,993.3 miles.

Just bask in that for a while.

(http://www.exploratorium.edu/ronh/solar_system/)

saintgimp2• 8 years ago

Although to be fair, dust is definitely a problem if you want to see into the center of the galaxy which is why most of the observations of Sagittarius A* are done in the infrared or near-infrared spectrum, which can penetrate dust. It's also why we can't see clear across our galaxy to make out what's beyond it, so we don't know what the Great Attractor is.

tehaugmenter• 8 years ago

It is empty, but its filled with "Space Grease"

https://www.theguardian.com/science/2018/jun/27/space-is-ful...

najarvg• 8 years ago

Indeed space dust is a problem. From notes in the parent article - "[3] Observations of the centre of the Milky Way must be made at longer wavelengths (in this case infrared) as the clouds of dust between the Earth and the central region strongly absorb visible light." This interstellar dust was recently revealed to be a fine mist of grease, soot and silicates - https://academic.oup.com/mnras/article/479/4/4336/5039660

SiempreViernes9• 8 years ago

As other said, but maybe not clearly enough: no space isn't that empty, there is a lot of dust in the way, but fortunately it is dilute enough that its transparent at some wavelengths and so we observe using those.

eigenloss2• 8 years ago

"More than one hundred years after he published his paper setting out the equations of general relativity, Einstein has been proved right once more — in a much more extreme laboratory than he could have possibly imagined!"

This sounds somewhat like an insult to Einstein's imagination.

laretluval2• 8 years ago

Up to his death Einstein denied that black holes could physically form.

Jach2• 8 years ago

It probably depends what one means by "black hole". Physical singularities are predicted by GR+other theorems but haven't been established.

ars4• 8 years ago

And he is right. Time dilation means it's impossible for them to form. (From the POV of me, here on earth.)

andrewflnr• 8 years ago

He could still imagine them, though.

laretluval2• 8 years ago

Do you doubt this? https://en.wikipedia.org/wiki/Einstein%27s_unsuccessful_inve...

carapace• 8 years ago

https://arxiv.org/pdf/physics/9905030.pdf

"On the Gravitational Field of a Mass Point according to Einstein’s Theory" by K. Schwarzschild, January 13th, 1916 (English translation)

Black holes are fiction. The whole mess started with people misunderstanding Schwarzschild's paper. Yes, there's a singularity in the math, but you can avoid it by changing the origin. This is one of those cases where conventional "science" has been gummed up by human foibles. (And the concept is so damned romantic and compelling. And that movie! It was like the opposite of "Jaws" for sharks.)

If you can't read the paper don't bother arguing with me. If you can, show me where the math says "black holes". I'm pretty sure it says "translate the origin and ignore the singularity".

mutagen2• 8 years ago

Anyone know why the black hole is marked well off the axis of the orbit of S2 in diagram [1]? Is there enough mass elsewhere at the center of the galaxy to have it orbiting a common mass so far off axis? The video of the orbit [2] seems to show it closer to the axis or the focus I'd expect but still seemingly a bit of an offset. The fulldome view video [3] does show that there is quite a bit of stuff moving around there so maybe my imaginations are wrong, I think of a black hole having so much mass that it completely dominates the local gravitational field.

1. https://www.eso.org/public/unitedkingdom/images/eso1825c/

2. https://www.eso.org/public/unitedkingdom/videos/eso1825g/

3. https://www.eso.org/public/unitedkingdom/videos/eso1825g/

contact_fusion• 8 years ago

Keep in mind that you are viewing the orbit in projection. The axes are simply the angular offset from the pointing.

Before I give away the punchline, try to imagine the orbit in a reference frame centered at the location of the black hole. Obviously, the motion should be elliptic; lets define a Cartesian coordinate system such that, say, the x-y plane coincides with the plane of the elliptic orbit. Now, we know that the black hole should reside at the focus of this orbit. But, as a far away observer, what are the chances that you would be seeing the orbit exactly face-on - i.e., you are sitting on the z axis, just really far away?

So, yes, the black hole is at the focus of the elliptic orbit, not the focus of the ellipse formed from the projection of the orbit onto your plane-of-sky, which geometry tells us is also an ellipse.

BTW, this isn't a problem for the astronomers. You can back out exactly what that inclination of the orbit is, provided you can measure the line-of-sight velocities of the star. (Actually, relative velocities will do; no absolute calibration necessary.) This is easily done by looking for some distinctive stellar spectral features and noting their relative shifts at different parts of the orbit. From this you can reconstruct the orbit completely. The key scientific results they derived was the even subtler redshift of these spectral features as the gravitational field grew stronger when the star approached the black hole.

edit: actually, you could do even better, and use the offset of the black hole from the elliptic focus, and use projective geometry to get the inclination angle!

mutagen2• 8 years ago

Ahhh so simple! Thank you very much for the moment of enlightenment.

gigatexal• 8 years ago

Coolest thing I have seen in a long time. Watched a replay of the livestream and it is so good!

NizaAfrica• 8 years ago

Question, is it possible that our universe could be in a black hole? When you look at the way our existence is structured, everything has a parent. An an electron has an atom has it's parent, atoms have molecules has their parent etc. Germs, bacteria, humans, planets all have parents. Surely our universe has to have a parent.

eponeponepon• 8 years ago

Possible? Sure, anything is possible - but apply your argument the other way round. People contain molecules, molecules contain atoms, atoms electrons and so on - does it then seem reasonable to ask whether that goes on forever? And if not, why should it be reasonable if you go upwards in the scale?

posterboy• 8 years ago

But it does seem reasonable. Very much so if going down far enough you find micro black holes at the center of atoms.

But you need some really funky geometry to make it more interesting then this played out trope. Say they are all the same black hole from different times seen through its own gravitational lense.

deadmetheny• 8 years ago

It's turtles all the way down.

jerf• 8 years ago

Give that question a good Googling and you'll find a lot of good stuff. It's not a bad question and has been seriously treated by a number of people.

acqq• 8 years ago

atoms have molecules has their parent etc. ... Surely our universe has to have a parent

Well... there's a limit to the scientific reach: when the scientists speak about "the Universe" they typically speak about "everything that is we can expect to reach using our instruments." Whatever is behind that is simply unreachable, and therefore out of the scope of the science.

But the good news is: what is reachable is immensely huge, and these far limits don't affect our lives directly, even if we can observe "what's there" (up to these limits).

In older times, some people thought that the movements of the planets, which are quite close to Earth compared to what we today can observe, affect our day-to-day life (and that was the idea behind "astrology"). Now we know it isn't so, they simply move because the gravity exits. We can observe much farther today: in the last 100 years we discovered that some of the points on the sky aren't stars but the galaxies: each point actually some billions of stars, much, much farther than the single stars we see! And we discovered that the farthest objects we can see are now some 46 billion light years from us, and that we actually see what there happened some 13 billion years ago -- not to mention that the we are actually made from the star dust (anything but our hydrogen atoms) and the rests of the "big bang" (the hydrogen atoms in our bodies)!

That's "the Universe" the scientists talk about. What's behind these limits can't predictably affect our own lives, as no signal "from this universe" can reach us faster than the speed of light: it takes 8 minutes for a light from Sun to reach us. Whatever produced some light that is 13 billion years old is now some 46 billion years away from us and changed through these 13 billion years. But we know that the "Universe" gets bigger so these objects we can never reach not even with the light from us to there, as they will continue to be even farther from us. So that's it. 46 billion light years in every direction.

https://medium.com/starts-with-a-bang/ask-ethan-how-much-of-...

https://medium.com/starts-with-a-bang/ask-ethan-how-large-is...

raattgift2• 8 years ago

Question, is it possible that our universe could be in a black hole?

Not without redefining what a black hole is.

General Relativity is a metric theory of gravitation. Black holes arise in General Relativity, and are defined by the family of metrics they source. There are astrophysical objects that humans observe (with various instruments) that match the predictions for black holes in General Relativity within the limits of measurement error. This article describes further such observations of the black hole in our galaxy's central parsec.

The salient feature is that a black hole metric has a boundary across which there is only one-way travel. Anything inside that boundary inevitably, inexorably, collides with a gravitational singularity inside that boundary. For the sake of quantum mechanics being valid everywhere (including deep inside black holes), there are proposals which would replace the singularity with some final structure of ultradense matter whose internal states resist collapse into a literal singularity, even as one collides arbitrarily large amounts of matter into it. However, in such proposals, the inevitable, inexorable inwards motion from the horizon inwards to quite near the "middle" remains a feature.

The inevitable, inexorable inwards motion is fast according to the wristwatch of an unlucky person crossing an event horizon; you won't need to take a calendar with you in order to count down your final minutes in a black hole like the one at the centre of our galaxy. You would have longer for a much much larger black hole, but as you and everything else would be collapsing inwards quickly, you would not observe the formation of stars or galaxies inside the horizon, even for an arbitrarily large black hole. Your sky would look nothing at all like the skies we have in our solar system; at the very largest scale for a black hole, you would not see the cosmological redshift that we see, and would not detect anything like the same cosmic microwave background.

At the largest scales -- where we take clusters of galaxies as particles of dust -- our universe is well-described by a metric for an expanding spacetime, with lots of supporting evidence from detection of the redshift of emissions and absorption spectra compared with angle on the sky, luminosity, and other features of distant galaxies. The expansion is not like the time-reversal of the inside of a universe-sized black hole, in particular since to a good approximation the distribution of galaxy clusters is isotropic and homogeneous, and groups of clusters nearby one another (on the a tight angle for the line of sight to each, and each at similar distances) are moving slowly and randomly with respect to one another, while such a group taken as a whole is nearly uniformly receding from our own galaxy cluster. This is nothing like the behaviour one would get inside a truly enormous black hole.

surely our universe has to have a parent

It's not required, but there are cosmological models that have notional "parents". Sean Carroll, a physical cosmologist at Caltech, has a set of slides outlining a few at https://www.slideshare.net/seanmcarroll/what-we-dont-know-ab... -- slide 14, "Reproducing cosmologies" and slide 17, "Reproducing cosmologies don't have an entropy problem", both references in the lower right hand corner that you can follow-up on if you are interested in the technical aspects.

The crucial point, however, is that we do not yet have good observations of the very early hot, dense universe of a bit less than fourteen billion years ago, so we have some freedom to choose among various theories which wholly match the history of the universe that we do have good observations for.

dwaltrip• 8 years ago

That logic leads to infinite regress... If everything has a parent, then what's the parent of that thing.

So either there is an infinite chain, or the logic is flawed -- e.g. it's possible to not need a parent.

Another possibility is that our conceptions of causality / structure / parenthood are fundamentally flawed (but still useful for human purposes at this point in time), and the question isn't fully coherent.

ENGNR2• 8 years ago

What if the big bang was a white hole?

I'd butcher the idea if I tried to explain but..

https://www.youtube.com/watch?v=S4aqGI1mSqo

magduf5• 8 years ago

I'm always a little disappointed when these experiments are unable to disprove General Relativity. I keep hoping that they'll discover something slightly wrong about it, which will quickly lead to us figuring out how to develop a practical warp drive which doesn't require negative or nearly infinite energy.

jjoonathan3• 8 years ago

Yeah, but small c might be the only thing keeping the giant space lizards on the other side of the galaxy from invading Earth.

magduf5• 8 years ago

I'm willing to take that risk. I want to take a vacation on Risa.

hellofunk3• 8 years ago

Quantum entanglement suggests strongly there are forces in the universe that travel much much faster than the speed of light, or rather, travel in a way in which speed does not matter.

macspoofing5• 8 years ago

I never thought of c being a real problem to space travel. Sure, on the timescale of our lives c is sloooow because moving between stars automatically necessitates a multi-generational approach and/or huge amount of resources. The big problem however, is that we have no place to go. We are tied to earth. Our bodies are made for a specific gravity constant, specific distance from a specific star, specific atmospheric mix of gases, a pre-existing DNA-based fauna and flora, etc. Quite simply, when it comes to colonization: there's no place like home. Every other place sucks for our bodies.

Once we achieve the singularity(tm) and upload our consciousness (or get replaced by AI), we can turn down the clock speed on the matrix (say turn 1,000,000 real years into 1 matrix year), and like magic c stops being a practical limitation. Sending message (or travelling) from one side of the galaxy to another would take a 'matrix month' .. turn the clock down even further and you can make galactic communication instantaneous.

rwcarlsen3• 8 years ago

You could actually reach almost anywhere in the galaxy within a single human lifetime (the traveler's lifetime that is) using only 1-G constant acceleration: https://en.wikipedia.org/wiki/Space_travel_using_constant_ac...

No FTL required. We just need to figure out how to use propellant efficiently enough among a few other slightly difficult challenges.

WalterBright2• 8 years ago

With genetic engineering, we can adapt our bodies to other situations.

marcosdumay2• 8 years ago

Any finite speed limit ultimately imposes a O(t^2) rate of growth into a civilization, while the natural rate of growth of a biological system is O(e^t).

The universal speed limit dictates how much of the Universe humans (or whatever comes after us) can ever visit, because of the Hubble constant.

A universal speed limit limits the size of a computer that can still have coherent "thoughts".

dmd• 8 years ago

You should read "Lockstep". https://smile.amazon.com/dp/B00H6E6ATI/

inamberclad• 8 years ago

Every other place sucks for our bodies.

The ones we know. Earth-like planets are hard to spot from very far away.

pasquinelli• 8 years ago

i always wonder what people mean by uploading consciousness. like, faster than light travel, i know what it means even if it's not possible, but to upload my consciousness... what, in theory, is supposed to happen? what does it happen to?

ringbugger• 8 years ago

I have been to burger king a little too often lately and I would be totally fine with a 0.75g planet now.

The "life corridor" is certainly very narrow. But I am sure there are at least some places.

Maybe we find a world near a smaller red dwarf, which will last for trillions of years. Maybe we also don't make that planet uninhabitable in a few thousand years, for once.

tshanmu• 8 years ago

this sounds a lot like Hindu philiosophy ;)

error_logic• 8 years ago

I like to imagine the Universe with the effects attributed to inflation and dark energy actually being explained by inverse curvature from antimatter (think relic antineutrinos). Every particle (including photons) would follow the curvature of spacetime, but antimatter would cause inverse curvature, and photons (perhaps bosons in general) would be passive rather than acting on it (inertial "mass" / momentum only).

This flies in the face of the Equivalence Principle, and requires that light's wavelength shifts due to the relative time where its energy is measured--not because of an equal and opposite gravitational interaction with the masses causing the gravitation.

Perhaps the most nonsensical consequence is the behavior of a particle-antiparticle pair co-accelerating to infinity...unless their eventual merger through relativity (length contraction) and quantum mechanics (tunneling into a merged state) actually explains the mechanism for annihilation.

The only testable prediction I have: Distant galaxies will be "too mature" for their apparant distance in space and time, meaning that the light has aged more than the distances would suggest (time slows in the presence of a gravity well, and would do the opposite for regions of space with inverse curvature--see above, re:inflation and the very start of the Universe).

throwaway37585• 8 years ago

Antimatter has opposite charge, not opposite mass. Antimatter is not antigravity.

codethief2• 8 years ago

I actually feel the exact opposite way when it comes to successful tests like the present one. Namely, these tests often also rule out modified theories of gravity which, to me, suggests that, by often considering more or less random (read: ugly) and little-justified modifications of general relativity, these theories have been looking in the wrong place when it comes to explaining dark matter (and, possibly, dark energy). …which, for me, not only makes the mystery of dark matter all the greater but also makes me appreciate Einstein's beautiful theory even more. :)

TomMckenny• 8 years ago

I keep hoping they'll find some discrepancy that somehow lets us mesh QM with it.

EastLondonCoder• 8 years ago

I have yet to see any ftl scheme that doesn’t break causality in some reference frame. I have a hard time fathoming a universe where cause and effect are disjointed, this leads me to think ftl is impossible. As other commenters are pointing out, c is not a big problem with long life spans and relativistic time contraction.

rdiddly3• 8 years ago

It appears astronomy articles have completely given up reminding us that the phenomena being observed at x light-years away, happened x years ago (26,000 in this case), so I'll do it. (Maybe it's more soothing to our human egos to feel like it's "happening right before our eyes" but I liked it better when talk of space made me feel small and insignificant.)

For example it's good for the ol' ego (and a fun flight of fancy back into the past) to be reminded that when this star was actually passing near the black hole, back here on Earth homo sapiens was enjoying his "cave paintings" phase, using stone tools (maybe juuust starting to get into metallurgy in some areas), and it was the peak of the last glacial maximum, which would've been quite noticeable while hunting wooly mammoths with spears in the northern latitudes.

EpicEng2• 8 years ago

Honestly, it would be pretty annoying for anyone even remotely familiar with high school level physics to he constantly reminded that a light year is the distance light travels in a year.

rdiddly3• 8 years ago

That's presumably why they don't do it, but you're being hyperbolic. An 8th grader is remotely familiar with high school physics. The janitor of the high school physics classroom is remotely familiar with high school physics. Yet they probably could both stand to be reminded a time or two what a light-year is.

roywiggins5• 8 years ago

Simultaneity is kind of arbitrary anyway. Sure, in our reference frame it happened a long time ago, but for someone on another worldline it happened just a minute ago.

Anyway, for most purposes, it just happened. We couldn't have noticed it earlier, it could not have affected us earlier. I don't think it's that inaccurate to say that they watched it as it happened.

SiempreViernes9• 8 years ago

But the light is arriving right here-now, which is the only time that really matters.

It makes absolutely no practical difference when talking about a specific event if you bother to include the time offset or not.

sixothree• 8 years ago

Which of that imagery is actual imagery and not artist interpretation?

cwillu2• 8 years ago

https://cdn.eso.org/images/large/eso1825g.jpg

https://cdn.eso.org/videos/ultra_hd/eso1825e.mp4

First Successful Test of General Relativity Near Supermassive Black Hole

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