For the first time, astronomers have measured the radius of a black hole

Sep 27, 2012 by Jennifer Chu
For the first time, astronomers have measured the radius of a black hole
This image, created using computer models, shows how the extreme gravity of the black hole in M87 distorts the appearance of the jet near the event horizon. Part of the radiation from the jet is bent by gravity into a ring that is known as the 'shadow' of the black hole. Credit: Avery E. Broderick (Perimeter Institute & University of Waterloo

(Phys.org)—The point of no return: In astronomy, it's known as a black hole—a region in space where the pull of gravity is so strong that nothing, not even light, can escape. Black holes that can be billions of times more massive than our sun may reside at the heart of most galaxies. Such supermassive black holes are so powerful that activity at their boundaries can ripple throughout their host galaxies.

Now, an international team, led by researchers at MIT's Haystack Observatory, has for the first time measured the radius of a black hole at the center of a —the closest distance at which matter can approach before being irretrievably pulled into the black hole.

The scientists linked together in Hawaii, Arizona and California to create a called the " Telescope" (EHT) that can see details 2,000 times finer than what's visible to the . These radio dishes were trained on M87, a galaxy some 50 million light years from the Milky Way. M87 harbors a black hole 6 billion times more massive than our sun; using this array, the team observed the glow of matter near the edge of this black hole—a region known as the "event horizon."

"Once objects fall through the event horizon, they're lost forever," says Shep Doeleman, assistant director at the MIT Haystack Observatory and research associate at the Smithsonian Astrophysical Observatory. "It's an exit door from our universe. You walk through that door, you're not coming back."

Doeleman and his colleagues have published the results of their study this week in the journal Science.

Jets at the edge of a black hole

Supermassive black holes are the most extreme objects predicted by 's —where, according to Doeleman, "gravity completely goes haywire and crushes an enormous mass into an incredibly close space." At the edge of a black hole, the is so strong that it pulls in everything from its surroundings. However, not everything can cross the event horizon to squeeze into a black hole. The result is a "cosmic traffic jam" in which gas and dust build up, creating a flat pancake of matter known as an . This disk of matter orbits the black hole at nearly the speed of light, feeding the black hole a steady diet of superheated material. Over time, this disk can cause the black hole to spin in the same direction as the orbiting material.

An accretion disk (orange) of gas and dust surrounds super-massive black holes at the center of most galaxies. These disks of galactic matter emit magnetic beams (pink lines) that spew out from the center of the black hole, drawing matter out from both ends in high-powered jets. Credit: NASA and Ann Field

Caught up in this spiraling flow are magnetic fields, which accelerate hot material along powerful beams above the accretion disk The resulting high-speed jet, launched by the black hole and the disk, shoots out across the galaxy, extending for hundreds of thousands of light-years. These jets can influence many galactic processes, including how fast stars form.

'Is Einstein right?'

A jet's trajectory may help scientists understand the dynamics of black holes in the region where their gravity is the dominant force. Doeleman says such an extreme environment is perfect for confirming Einstein's theory of general relativity—today's definitive description of gravitation.

"Einstein's theories have been verified in low-gravitational field cases, like on Earth or in the solar system," Doeleman says. "But they have not been verified precisely in the only place in the universe where Einstein's theories might break down—which is right at the edge of a black hole."

According to Einstein's theory, a black hole's mass and its spin determine how closely material can orbit before becoming unstable and falling in toward the event horizon. Because M87's jet is magnetically launched from this smallest orbit, astronomers can estimate the black hole's spin through careful measurement of the jet's size as it leaves the black hole. Until now, no telescope has had the magnifying power required for this kind of observation.

"We are now in a position to ask the question, 'Is Einstein right?'" Doeleman says. "We can identify features and signatures predicted by his theories, in this very strong gravitational field."

This artist's impression of the innermost regions of M87 shows the relationship between the black hole, the orbiting accretion flow, and the launching of the relativistic jet. Credit: Perimeter Institute for Theoretical Physics

The team used a technique called Very Long Baseline Interferometry, or VLBI, which links data from radio dishes located thousands of miles apart. Signals from the various dishes, taken together, create a "virtual telescope" with the resolving power of a single telescope as big as the space between the disparate dishes. The technique enables scientists to view extremely precise details in faraway galaxies.

Using the technique, Doeleman and his team measured the innermost orbit of the accretion disk to be only 5.5 times the size of the black hole event horizon. According to the laws of physics, this size suggests that the accretion disk is spinning in the same direction as the black hole—the first direct observation to confirm theories of how black holes power jets from the centers of galaxies.

The team plans to expand its telescope array, adding radio dishes in Chile, Europe, Mexico, Greenland and Antarctica, in order to obtain even more detailed pictures of in the future.

Explore further: The changing laws that determine how dust affects the light that reaches us from the stars

More information: www.eventhorizontelescope.org/

Ref. "Jet Launching Structure Resolved Near the Supermassive Black Hole in M87," by S.S. Doeleman et al., Science, 2012.

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Claudius
3.5 / 5 (13) Sep 27, 2012
OK, so what's the radius?
Sonhouse
not rated yet Sep 27, 2012
6.2345 meters.:)

I wonder if that technique can be used for close in stars like Alpha Centauri, that would represent about 500 mile or 800 Km resolution there.
Jeweller
5 / 5 (1) Sep 27, 2012
The way this article was written, conjured up (in me) an image of The Mad Hatters Tea Party from Alice in Wonderland.
Once you go through that door, you're never coming back !
On a more serious note though, 2000 times more powerful than that which Hubble can detect. That may be so.
I look forward to what the Webb telescope will be able to detect.
cantdrive85
1.3 / 5 (14) Sep 27, 2012
Only ever "artist's impressions" of black holes, makes sense being all it really is, is a "mathematicians impression" of reality, however skewed that may be.
joefarah
1.7 / 5 (18) Sep 27, 2012
Please, can we get Einstein's theory, and physics, right. It says nothing can travel faster than c (speed of light). It does not limit acceleration. If I have a force (other than gravity, for example), say due to the incredible spin rate of charged matter in the rotating black hole, that is acting to accelerate a charged particle away from the black hole, it may certainly escape the black hole. Similarly, if two black holes travel past each other such that their accretion disks overlap, one can certainly accelerate matter out of the other black hole if that matter otherwise has sufficient acceleration acting on it.

Light cannot escape from a black hole. But give me a strong enough electric field, and I'll send a proton or electron out of the black hole. Or a sufficient magnetic field, and I'll send an iron atom out of the black hole. IT DOES NOT HAVE TO TRAVEL FASTER THAN C TO ESCAPE. It can move at net 10mph from the black hole and will eventually escape.
Claudius
2.5 / 5 (8) Sep 27, 2012
...give me a strong enough electric field

And a place to stand?
antialias_physorg
4.8 / 5 (17) Sep 27, 2012
Please, can we get Einstein's theory, and physics, right.

...
if two black holes travel past each other such that their accretion disks overlap, one can certainly accelerate matter out of the other black hole if that matter otherwise has sufficient acceleration acting on it.

I think you missed the part where Einstein said something about relativistic mass increase.

IT DOES NOT HAVE TO TRAVEL FASTER THAN C TO ESCAPE

Yes it does. Otherwise a photon emitted by your atom of iron would also escape (and much earlier). But it can't.
Shinichi D_
1.3 / 5 (4) Sep 27, 2012
Maybe 3-4 times the size of Pluto's orbit.
christ_jan
1.9 / 5 (9) Sep 27, 2012
If nothing can escape than what is hawking radiation? Also are we going to continue calling them black holes or are we going to call them black suns? Or does that sound too much like nazi symbolism?
axemaster
3.7 / 5 (14) Sep 27, 2012
@joefarah

Sorry, but you're wrong. The real reason you can't escape from a black hole is that once you pass the event horizon, the space becomes closed. In other words, every path in every direction ends at the singularity. The singularity surrounds you, and the more you accelerate yourself, the sooner you smash into it. That's all there is to it.

Also, I would point out that this picture bears direct analogy to our universe as a whole. The edge of the universe is contracting towards us continually - just as one would expect to see a singularity do inside a black hole. Moreover it shares a similar property - it is the point at which the energy of incoming radiation drops to zero due to the relative expansion of space at the speed of light.

I don't care how big an electric field you have, you can't escape from a black hole any more than you can the universe itself - the problem is that there is no appropriate direction in which to push yourself.
dogbert
1.9 / 5 (9) Sep 27, 2012
The article title mentions the radius, but the article seems to be discussing the circumference.

Can anyone actually measure the radius of a black hole? Is the distance not effectively infinite?
Silverhill
5 / 5 (4) Sep 27, 2012
I've read that it makes more sense to discuss the circumference of the event horizon. The radius (according to something falling in) is effectively infinite, since the time of fall is stretched out indefinitely.
One could compute the radius of a sphere whose circumference equaled that of the event horizon, of course; sort of like the "classical radius" of an electron.
javjav
3.7 / 5 (3) Sep 27, 2012
What I don't understand is how can the gravity force escape from the blackhole . If a black hole is moving, how can the inner mass tell the exterior space that she is there and that he has to warp accordingly?

If that is possible for mass, could not a falling object pass the event horizont and then convert.mass into energy on purpose to reduce gravity , as a way to send information outside?
VendicarD
4 / 5 (4) Sep 27, 2012
Sorry Joe. It doesn't work that way. Once inside the event horizon, all possible trajectories point inward, toward the singularity, be it a point or a circle.

You can't get out because there is literally no outward path to take.

"It can move at net 10mph from the black hole and will eventually escape. - JoeFarah
VendicarD
5 / 5 (6) Sep 27, 2012
"If a black hole is moving, how can the inner mass tell the exterior space that she is there and that he has to warp accordingly?" - Javjav

That is an exceptionally good question.

The answer is that the curvature of space in at least in part caused by the curvature of space, so all effects are strictly local.

Gravity doesn't radiate from the center of a black hole. It is constrained to effect only the space in immediate contact with it.

Objects falling into a black hole, from our perspective never reach the event horizon. They just fall toward it forever. So from out perspective their mass never leaves the realm of detection.

VendicarD
5 / 5 (5) Sep 27, 2012
You have to define it before you can measure it.

"Can anyone actually measure the radius of a black hole?" - DogBert

Presuming that you are referring to the event horizon,
currently there are no instruments precise enough to do so.

If you are defining the size to be the extent of it's gravitational field, then it has some now large radius defined by the parameters of cosmic inflation, provided such a thing occurred.
VendicarD
5 / 5 (5) Sep 27, 2012
It is a surface effect.

"If nothing can escape than what is hawking radiation?"- christian

With Hawking radiation you have a particle/antiparticle pair created near the event horizon. One particle has sufficient energy to be detected at some distance. The other falls into the hole. The result is that the particle that can be detected must have reduced the local gravitational stress near the event horizon and hence the particle that fell in must have reduced the black hole's mass (presuming that energy is conserved).
cantdrive85
1 / 5 (14) Sep 27, 2012
Those "extra galactic jets" are the birkeland currents that are powering the galaxy. The thing they call an accretion disk is actually the plasma torus at the center of the galaxy. As the electric currents flow into the core of the galaxy, the interacting plasmoids create a Faraday or homopolar motor effect where the electrical energy flows out through the spiral arms where the circuit then returns to the galactic circuit via the galaxy's plasmasphere. The large "halo of hot gas" encircling the Milky Way is probably the signature of the galaxy's own plasmasphere. A key aspect of the EUT is that the properties of plasma are scalable, so what happens on an atomic or laboratory level can be extrapolated to solar and galactic phenomenon.
LarryD
1.3 / 5 (12) Sep 27, 2012
All very interesting, you guys, BUT it is all just theory. May when someone gets close enough to identify an actual B.H. then they can ask the 'mad hatter' what's inside! Maybe 'ejection' will be a 'white hole'...oh but wait, someone said W.H. can't exist so maybe all B.H. meet at the same point where all answers come before the questions....
rah
2 / 5 (8) Sep 28, 2012
I guess including the radius would have been too much math.
dompee
4.6 / 5 (9) Sep 28, 2012
@LarryD...someone has identified an "actual B.H." they are not "just a theory" actually their has been more than just a someone, many black holes have been detected by many diff people. Not sure what type of evidence you require BUT we have many diff lines of evidence proving they exist. Do some research and don't forget to check your sources, apparently your lacking credible ones...on top of the already convincing evidence currently their is a team working on taking a picture of a shadow cast by a black hole perhaps when those results come in you will be confident they are not "just a theory"
Shinichi D_
1 / 5 (3) Sep 28, 2012
ShotmanMaslo
1.8 / 5 (5) Sep 28, 2012
What I don't understand is how can the gravity force escape from the blackhole . If a black hole is moving, how can the inner mass tell the exterior space that she is there and that he has to warp accordingly?


The explanation I read somewhere is that CHANGES in gravity field travel at c. When something falls into a black hole, the changes cannot travel outside and the field simply stays the same as it was - attractive.

Note that this question is just as relevant for electric fields, too. Black holes can be charged.

If that is possible for mass, could not a falling object pass the event horizont and then convert.mass into energy on purpose to reduce gravity , as a way to send information outside?


Energy has gravity. Converting mass to energy does not change gravitational attraction.
antialias_physorg
4.6 / 5 (12) Sep 28, 2012
If nothing can escape than what is hawking radiation?

Hawking radiation is virtual particle pairs (vacuum fluctuations) which are created near (but outside) the event horizon.

Far away from black holes virtual particle pairs just annihilate shortly after being created. Close to a black hole event horizon you can have the case that one of the pair falls in and therefore cannot annihilate with its counterpart (forcing it to become real). The now real particle may be able to escape the gravity well (or it may not: in which case - meh).

If it does escape it LOOKS like it was emitted from the black hole (but it wasn't actually emitted).

The freaky thing is that the energy balance can be so that the black hole loses energy in the process (by the amount of energy contained in the 'emitted' particle because the part that fell in had negative energy.). So black holes can 'evaporate' by this process.

That's the theory, at least. Hawking radiation has not been verified,
antialias_physorg
4.7 / 5 (9) Sep 28, 2012
If a black hole is moving, how can the inner mass tell the exterior space that she is there and that he has to warp accordingly?

Gravity is a geometric effect. If it's not mediated by particles then there is no speed limit.

That's what some of the experiments for gravity waves are trying to find out, whether gravity waves travel at finite speeds or not.

In QM the graviton is the carrier of gravity (at speed of light and massless). But there are some problems with this, as all other forces mediated by gauge bosons (photons, W and Z boson, gluon) can be shielded (i.e. the force is transmitted by emission and absorption of these gauge bosons)

Gravity is different. It cannot be shielded from (as far as we know), so a transmission via a finite number of 'gravitons' emitted from a source is problematic (unless there are so many that we just haven't been able to measure the shielding effect of, say, planets yet). The jury on this is still out.
Fleetfoot
5 / 5 (6) Sep 28, 2012
IT DOES NOT HAVE TO TRAVEL FASTER THAN C TO ESCAPE.


Yes it does, that is the definition of the event horizon.
Shinichi D_
1 / 5 (2) Sep 28, 2012

In QM the graviton is the carrier of gravity (at speed of light and massless). But there are some problems with this...


Black holes - by definition - would not have gravity at all in this case for example.
antialias_physorg
4 / 5 (7) Sep 28, 2012
Black holes - by definition - would not have gravity at all in this case for example.

Well, sorta. If gravitons don't interact with each other then to them the universe would always look flat. So they could escape a black hole. But yes: the graviton/gauge boson view needs some tweaking to work.

The Enhanced LIGO experiment will probably tell us more. But the precision needed for the measurement apparatus is mind-boggling.
From:
http://en.wikiped...iki/LIGO

"Based on current models of astronomical events, and the predictions of the general theory of relativity, gravitational waves that originate tens of millions of light years from Earth are expected to distort the 4 kilometer mirror spacing by about 10E-18 m, less than one-thousandth the 'diameter' of a proton."

Fleetfoot
4.6 / 5 (9) Sep 28, 2012
OK, so what's the radius?


The article says the mass is 6 billion Msun which gives radius of 17 billion km or 16.4 light hours for the event horizon. The observed inner radius of the accretion disc is 5.5 times that or 90 light hours.
Fleetfoot
3.7 / 5 (3) Sep 28, 2012
The article title mentions the radius, but the article seems to be discussing the circumference.

Can anyone actually measure the radius of a black hole? Is the distance not effectively infinite?


The radial coordinate effectively becomes time-like and there is a coordinate singularity at the event horizon so the usual definition of radius is difficult. Instead it is usual to define the radius as the circumference divided by twice Pi.
ccr5Delta32
1.7 / 5 (6) Sep 28, 2012

Gravity is a geometric effect. If it's not mediated by particles then there is no speed limit.

Why can't the geometry of space/time have a speed limit ? ( The universe we live in does not have instantaneous gravitational effect distribution )
So it's either particles or the premiss is wrong . And here I am , one who thought phlogiston was a good idea , Are we still hooked on Plato ?
I'll bag in with a third alternative " It's neither "
I do enjoy the questions and comments on relativity things ,none of them are stupid but the answers may be
Oh and ,Thank You Antialias for your endeavors here
Fleetfoot
5 / 5 (9) Sep 28, 2012
Incidentally, if anyone thinks the writers of the scientific paper were claiming to have "measured the radius of a black hole", the title of the paper is actually "The size of the jet launching region in M87". Never trust the popularisations.
indio007
2.6 / 5 (5) Sep 28, 2012
"gravity completely goes haywire"
Is that the scientific terminology?
Shinichi D_
3 / 5 (4) Sep 28, 2012

Why can't the geometry of space/time have a speed limit ? ( The universe we live in does not have instantaneous gravitational effect distribution )


I am not sure. I think the debate is still ongoing, it's just very hard to check it.
antialias_physorg
4.3 / 5 (6) Sep 28, 2012
Why can't the geometry of space/time have a speed limit ?

It might. Point is: if it's a geometric effect not mediated by a gauge boson then there is no reason why it should be limited by the speed of light.
The universe we live in does not have instantaneous gravitational effect distribution

We don't know if that's true. The problem is that there is no real place where gravity suddenly turns on or off which one could use to measure it (unlike with all the other forces). That's why gravity waves are so interesting because they at least give us a gradient.

Thank You Antialias for your endeavors here

You're welcome (but please note: I'm not a physicist. Just working on the stuff I learned at uni and read about on my own)
LarryD
2.3 / 5 (3) Sep 28, 2012
Thank you dompee and shinichi for trying to put me right. I am an interested layman not an expert. Yes I aware aware of the 'evidence' you mention but I think you missed my point. I was referring to a B.H. not the evidence for the EXISTENCE of B.H. Eg. (classical B.H.)if nothing can escape from inside the E.H. then we have to rely on what is happening just at, or ouside the E.H. If the speed of sound increases with density then the singularity must be one superspeed, noisey place but I have not read any accounts of sound waves escaping. However, I am relying on the math (Bulk Modulus for example)to be the same inside the E.H. as it would be outside the E.H. and that is the 'theory part'. Then there is the problem that all non-classical B.H. don't behave the same depending on what is the overwhelming process, Grav, Quantum, Time etc.
ValeriaT
1 / 5 (13) Sep 29, 2012
When the massive star explodes, it radiates portion of its mass in form of lightweight particles: photons and neutrinos. These particles do spread in speed of light and they do represent, what the gravitational wave is called in general relativity. But the main portion of energy will escape with superluminal speed and it's responsible for so-called dark matter effect. My guess is, this portion of energy is actually dominant in the same way, like the dark matter is dominant over the visible mass in our Universe. It's speed could vary from speed of light to 10E10 multiple of speed of light and its waves do manifest itself like the changes of CMBR noise intensity.
Fleetfoot
4.3 / 5 (6) Sep 29, 2012
When the massive star explodes, it radiates portion of its mass in form of lightweight particles: photons and neutrinos.


Correct, and a lot (the majority) is also ejected as normal matter as well.

These particles do spread in speed of light ..


Photons do, neutrinos don't (they have non-zero mass).

and they do represent, what the gravitational wave is called in general relativity.


No they don't, a GW is closer to the effect of the Moon on the Earth when it raises tides, a variation of gravity itself.

Note also a symmetrical supernova does not create GW, only an off-centre explosion would produce gravitational waves.

But the main portion of energy will escape with superluminal speed ...


Don't be silly, nothing moves superluminally.

Most of the material is slow moving heavier elements, the matter from which planets are made, and us!
Fleetfoot
4.2 / 5 (5) Sep 29, 2012
However, I am relying on the math (Bulk Modulus for example)to be the same inside the E.H. as it would be outside the E.H. and that is the 'theory part'.


The math says material inside the EH must fall to the centre, the region just inside the EH must be hard vacuum other than any particles just passing through.
ValeriaT
1.5 / 5 (8) Sep 29, 2012
Don't be silly, nothing moves superluminally.
Gravitational waves are spreading like the quantum waves: they don't move, but emerge and disappear again. In general relativity the reference frame is defined with curvature of space-time only - but gravitational wave is nothing but a space-time curvature too. So it must spread with higher speed.
Kron
1.7 / 5 (15) Sep 29, 2012
Blackholes are 2Dimensional. Matter does not go through the event horizon. Blackholes are infinitely dense, so "inside" the blackhole there is zero volume. Objects cannot evolve without space so this means no time. So starting from 4Dimensions we have loss of volume and loss of time which equates to 2Dimensions.

All the infalling energy is trapped on the surface of the blackhole. Blackholes have a surface area which grows with the addition of energy. This surface is the event horizon. The event horizon is the surface that divides infinite density and infinite gravity. Matter cannot overcome infinite density and cross the event horizon. It also cannot overcome infinite gravity and escape the event horizon (except possibly indirectly in special cases like quantum fluctuations).

All we have is a 2Dimensional surface, so nothing falls into a blackhole.
Kron
1.7 / 5 (15) Sep 29, 2012
The event horizon is like a photograph, a snapshot, of 4 dimensional space-time. All the information is left on the 2 dimensional film that is the event horizon. The 3 dimensional objects are captured on a 2 dimensional surface, the objects are lost forever but the information of their prior existence is forever documented in a timeless, volumeless state.
ValeriaT
1 / 5 (8) Sep 29, 2012
I often model the space-time like the water surface - at the distance all ripples get scattered, which appears like the universe event horizon. The black holes are something like the dense blobs at the water surface - the surface ripples gets scattered inside of them too, so that their content remains hidden from human observers. This model appears silly, but it helps to decide the recent controversy, if the even horizon behaves like the firewall or complementarity. From this scheme follows, it's both.
ValeriaT
1.3 / 5 (8) Sep 29, 2012
The 3 dimensional objects are captured on a 2 dimensional surface, the objects are lost forever but the information of their prior existence is forever documented in a timeless, volumeless state.
What does it mean "documented"? When you fall into black hole, you'll simply evaporate and most of you will radiate back in form of accretion radiation, the rest will be dissolved into gravitons, which will mix together. Nothing observable will remain from you after then.
All we have is a 2Dimensional surface, so nothing falls into a blackhole.
Which is nonsense - we are observing jets and accretion disks, which are evidence of matter falling into black hole. Sometimes it's good to get a real life instead of misleading abstract schematic geometry.
Shinichi D_
3.7 / 5 (6) Sep 30, 2012
Which is nonsense - we are observing jets and accretion disks, which are evidence of matter falling into black hole. Sometimes it's good to get a real life instead of misleading abstract schematic geometry.


Yes, but jets and accretion disks are not part of the black hole itself, just side effects of the immense gravitational pull of it.
bsummey
1 / 5 (3) Sep 30, 2012
Please, can we get Einstein's theory, and physics, right. It says nothing can travel faster than c (speed of light). It does not limit acceleration.


You missed the point of what goes on inside a black hole, or its event horizon. The gravity or mass however you want to look at it create such an effect on time that no matter how fast below the speed of light the particle is traveling it will NEVER get out. Thats the key to the whole thing, the particles emitted from within the event horizon can be any speed you want, below the speed of light even 10mph from the center, time is so distorted that the particle traveling the speed of light will never have the time to escape. The same works both ways. In theory no matter ever reaches the black hole center after it was created. Its all stuck somewhere between the event horizon and the center. It can be moving the speed of light towards the center and never have enough time to reach. You described newtonian physics not relative
Fleetfoot
5 / 5 (3) Sep 30, 2012
Don't be silly, nothing moves superluminally.
Gravitational waves are spreading like the http://www.freeim...t/gq68w: they don't move, but emerge and disappear again. In general relativity the reference frame is defined with curvature of space-time only - but gravitational wave is nothing but a space-time curvature too. So it must spread with higher speed.


Garbage, GR is classical and GW are variations of the geometry, they move at c relative to any matter they encounter. Please don't repeat this pseudo-scientific disinformation, if you want to post here, find out what you are talking about first.
Fleetfoot
5 / 5 (2) Sep 30, 2012
Blackholes are 2Dimensional.


The Scwarzschild Solution is 4D.

Matter does not go through the event horizon.


True for the coordinate system of a distant observer but matter crosses the horizon and travels to the singularity in finite proper time.

Blackholes are infinitely dense


In the classical limit, the singularity would be infinitely dense, not the region between it and the horizon.

Objects cannot evolve without space so this means no time.


The radial direction becomes timelike, "inwards" becomes "future".

Blackholes have a surface area which grows with the addition of energy. This surface is the event horizon.


Correct, though it is just a surface in the vacuum and its location depends on the motion of the observer.

The event horizon is the surface that divides infinite density ..


No, there is vacuum either side, infinite density is at the singularity.
Fleetfoot
5 / 5 (4) Sep 30, 2012
I often model the space-time like the water surface


which is silly because ..

at the distance all ripples get scattered


that doesn't happen in water, they simply reduce in amplitude as the inverse of their distance from the source.

which appears like the universe event horizon.


Not even close. This is the closest water model you'll get to a non-rotating black hole (Schwarzschild), the event horizon is where the slope of the infalling material is 45 degrees to the distant surface, inside which ripples the flow is faster than ripples move across its surface:

http://bizmum.com...pool.jpg

In general though, angular momentum of the infalling material makes this a better analogy:

http://uvs-model....pool.jpg
rah
1 / 5 (4) Sep 30, 2012
No, they have not.
Moebius
1 / 5 (4) Sep 30, 2012
This is interesting. It makes me wonder if this can tell if singularities exist. I would think that the relationship between radius and mass would be different if there is a singularity at the center of black holes.
ValeriaT
1 / 5 (6) Sep 30, 2012
they simply reduce in amplitude as the inverse of their distance from the source
Only theoretically. In reality small portion of wave energy gets scattered into underwater, which can be seen with gradual increasing of the wave wavelength.
this is the closest water model you'll get to a non-rotating black hole
Such a model doesn't explain the complementarity of black holes, for example.
angular momentum of the infalling material makes this a better analogy
Analogy of what?
joefarah
1 / 5 (4) Sep 30, 2012
@Axemaster @VednicarD - Thank you for putting my mind straight (i.e. space bending inward). So the first obvious question: from inside a black hole if a star entered the event horizon, where would it seem to have come from, since it could not then have come from inside the closed space.

Just as the black hole creates a singularity in our "universe", could there not be singularities within the black hole.

OK - I admit - it's difficult to picture a black hole from the inside.

And the second question is whether it's possible that other forces affect the fabric of space-time (unified theory?)?
LarryD
1 / 5 (2) Oct 01, 2012
'All we have is a 2Dimensional surface, so nothing falls into a blackhole.'
As I said I am a layman. Now you expets are really confusing me. I thought that the common geometrical 'ball on a rubber sheet' example was just that, a 2D representation of a real life 3D or 4D situation. For example, the mass of the Earth curves space-time in its 3D (or 4D) reality, that is, the curvature takes place all around the globe and not at some perticular orientation. Is it not the same for B.H.? Doesn't a B.H. deform S-T in a 3D (4D) spherical manner so that no matter from which angle/position one approaches the B.H. the gravitational effect is the same? I admit that perhaps some matter falling into the B.H. might produce 2D accretion 'ring' given certain conditions but surely matter can fall into the B.H. any angle. Am I wrong?
rjsc2000
not rated yet Oct 01, 2012
Why don't they train it to a closer location? Wouldn't that give a better resolution?
antialias_physorg
3.7 / 5 (3) Oct 01, 2012
And the second question is whether it's possible that other forces affect the fabric of space-time

There's the possibility of ultra short range forces (shorter than the weak nuclear force) and ultra long range forces (longer range than gravity).

The first type we're probing with stuff like the LHC, the latter type is really hard to detect and would show up only at cosmological scales. There's still room for that type of force (as a way to codify the dark matter/dark energy concepts)

So the first obvious question: from inside a black hole if a star entered the event horizon, where would it seem to have come from

There is no path from you to it, but there is a path from it to you. So you'd see it as a massively redshifted and slowed down process (but there would be no special event to mark its crossing the event horizon from your POV).
Fleetfoot
5 / 5 (2) Oct 01, 2012
they simply reduce in amplitude as the inverse of their distance from the source
Only theoretically. In reality small portion of wave energy gets scattered into underwater,
.

Energy lost through viscosity turns to heat.

which can be seen with http://www.josesa...ples.jpg of the wave wavelength.


If the wavelength was changing (which it isn't), your image would show them getting shorter:

http://www.flickr...7517344/

Can't you tell the difference between "short" and "long" yet?

this is the closest water model you'll get to a non-rotating black hole
Such a model doesn't explain the complementarity of black holes, for example.


Analogies never show everythig, but that is far closer than your attempt which doesn't model a horizon at all.

angular momentum of the infalling material makes this a better analogy
Analogy of what?


In reality, zero rotation would be a special case.
Fleetfoot
5 / 5 (2) Oct 01, 2012
Just as the black hole creates a singularity in our "universe", could there not be singularities within the black hole.


The singularity is an extrapolation of classical GR without QM and is a single point at the centre, i.e. within the hole.

So the first obvious question: from inside a black hole if a star entered the event horizon, where would it seem to have come from, since it could not then have come from inside the closed space.

OK - I admit - it's difficult to picture a black hole from the inside.


This site is excellent at answering that:

http://casa.color...hw.shtml

And the second question is whether it's possible that other forces affect the fabric of space-time (unified theory?)?


Yes, a charged black hole behaves differently from an uncharged one:

http://en.wikiped...m_metric

http://en.wikiped...n_metric
Fleetfoot
5 / 5 (3) Oct 01, 2012
'All we have is a 2Dimensional surface, so nothing falls into a blackhole.'

As I said I am a layman. Now you expets are really confusing me.

..

Am I wrong?


No, the person you quoted was wrong even by layman standards.

About half the contributors to this site are amateurs (like myself) so treat any answers as only a hint on what to look for on reputable sites.
Fleetfoot
5 / 5 (2) Oct 01, 2012
Why don't they train it to a closer location? Wouldn't that give a better resolution?


They need a target which isn't obscured by dust etc. and has the right orientation to us.
tadchem
1 / 5 (2) Oct 01, 2012
There is no 'passing the event horizon. All matter that reaches the event horizon merges instantly and completely with the black hole. The black hole itself only has mass, charge, and angular momentum. These properties are conserved and accumulated from the infalling matter.
It also has zero entropy.
Gravitons are the 'fairy dust' of particle physicists whose mathematics cannot deal with curved space-time.
Fleetfoot
3.7 / 5 (3) Oct 01, 2012
There is no 'passing the event horizon. All matter that reaches the event horizon merges instantly and completely with the black hole.


There's a treatment of that aspect here which covers the difference between proper and coordinate time:

http://physics.uc...an11.pdf
Kron
1 / 5 (6) Oct 04, 2012
There is no physicality beyond the event horizon of a bh. The density is far too great for matter/energy to enter a blackhole. what happens instead is that matter leaves a 2D imprint on the surface of the bh. So information is not lost. If information were lost (as classical treatment dictates) then radiation would be impossible. So for eg. the infalling proton loses volume and freezes in time as it imprints on the eh, the eh surface area and the mass of the bh increase. Now radiation: as the bh evaporates the mass is lost, the 2D proton gains volume and regains time. So bh evaporation reverses the process. Infalling: 4D > 2D, radiating 2D > 4D.

Inside of the bh there is no physicality. A hologram may be created inside of the bh as a projection of the 2D information that is on the surface, the event horizon (eh). So inside of the bh there may be an illusion of a 4Dimensional reality, but there is no real space.

amateurs

I am one.
Kron
1 / 5 (6) Oct 04, 2012
Leonard Susskind masterfully explains this concept and the reasons behind the conception. Look into the Holographic Principle.
ValeriaT
1 / 5 (6) Oct 04, 2012
There is no physicality beyond the event horizon of a bh.... so information is not lost..
Apparently some unphysical information resides there...;-) I dunno, it Susskind explained it masterfully or not - but you apparently failed to reproduce him.

In AWT the situation with black hole is similar, like with hollow in the fog. You cannot see inside it, but if you would get closer, you would reveal another and another portion of it. In this moment this analogy fails, because you would evaporate near black hole, but if you could survive it, then you probably would find another piece of Universe there, not very difficult from our one (the appearance of infinite random Universe is essentially always given with the geometry of its observer, which is alway way smaller).
Kron
1 / 5 (6) Oct 04, 2012
People who live in glass houses shouldn't throw bricks.
you apparently...failed to...masterfully...reproduce [Leonard Susskind]

I don't doubt it. Just trying to bring a new aspect to the discussion.

But back to the glass house. Do you think the negative reception of AWT may be due in part to your inability to present it clearly? ;-)

"A question that drives me hazy, am I or the others crazy?"

I can't make out the hollow in your fog.
Fleetfoot
5 / 5 (2) Oct 04, 2012
People who live in glass houses shouldn't throw bricks. ... But back to the glass house. Do you think the negative reception of AWT may be due in part to your inability to present it clearly? ;-)


The reason is that there is no such thing as "AWT", he doesn't have a theory to present. The phrase "AWT says" is just his way of introducing statements that are just random speculation with no backup at all.
Kron
1.4 / 5 (10) Oct 04, 2012
All theories have an axiom as a foundation. An aspect of reality that is assumed to be true as the basis of the theory. Theories are therefore never true. They are only proven based on the assumptions residing at their core.

For an idea (such as AWT) to become a real theory, proof must be provided that ties the axioms together with mathematical rigor. At this point an equation surfaces into which REAL WORLD VARIABLES can be plugged in. The theory is proven when real world results equal the results of your formulae. This doesn't mean that the theory is the ultimate reality, only that the theory is applicable towards the real world.

I cannot find any mathematical proofs of AWT. Can you prove that it applies to the real world? Can you provide a way of connecting your Aether Wave [Model] to the REAL WORLD? Does AWT have any useful formulas?

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