Disaster looms for gas cloud falling into Milky Way's central black hole

Dec 14, 2011
This view shows a simulation of how a gas cloud that has been observed approaching the supermassive black hole at the center of the galaxy may break apart over the next few years. This is the first time ever that the approach of such a doomed cloud to a supermassive black hole has been observed and it is expected to break up completely during 2013. The remains of the gas cloud are shown in red and yellow, with the cloud's orbit marked in red. The stars orbiting the black hole are also shown along with blue lines marking their orbits. This view simulates the expected positions of the stars and gas cloud in the year 2021. Credit: ESO/MPE/Marc Schartmann

The normally quiet neighborhood around the massive black hole at the center of our Milky Way Galaxy is being invaded by a gas cloud that is destined in just a few years to be ripped, shredded and largely eaten.

Many, if not all, galaxies have massive at their centers. But this is the only one close enough for astronomers to study in detail, so the violent encounter is a unique chance to observe what until now has only been theorized: how a black hole gulps gas, dust and stars as it grows ever bigger.

"When we look at the black holes in the centers of other galaxies, we see them get bright and then fade, but we never know what is actually happening," said Eliot Quataert, a and University of California, Berkeley professor of astronomy. "This is an unprecedented opportunity to obtain unique observations and insight into the processes that go on as gas falls into a black hole, heats up and emits light. It's a neat window onto a black hole that's actually capturing gas as it spirals in."

"The next two years will be very interesting and should provide us with extremely valuable information on the behavior of matter around such massive objects, and its ultimate fate," said Reinhard Genzel, professor of physics at both UC Berkeley and the Max Planck Institute for (MPE) in Garching, Germany.

The discovery by Genzel; Stefan Gillessen of the MPE; Quataert and colleagues from Germany, Chile and Illinois will be reported online Wednesday, Dec. 14, in advance of the Jan. 5 publication of the news in the British journal Nature.

Since 2008. Genzel, Gillessen, Quataert and their team have seen the gas cloud about three times the mass of Earth speeding up as it has fallen deeper into the gravitational whirlpool of the black hole. Its edges are already beginning to fray.

"It is not going to survive the experience," said first author Gillessen. He built the infrared detector on the European Southern Observatory's Very Large Telescope in Chile used to observe the movement of stars and gas in the center of the Milky Way, 27,000 light years from Earth.

By 2013, scientists should see outbursts of X-rays and radio waves as the cloud – composed mostly hydrogen and helium gas gets hotter and is torn asunder. The light emitted around the black hole could increase by a hundredfold to a thousandfold, Quataert calculated.

The Chandra X-ray satellite has already scheduled its largest single chunk of observation time in 2012 near the Milky Way's central black hole.

Black hole normally quiet

Astronomers have long observed clouds of gas streaming toward the center of our , presumably destined to fall into the 4.3 million solar-mass black hole lurking there. But this black hole "has a surprisingly low amount of matter falling inward at the moment," Quataert said.

Since MPE astronomers began observing the black hole in 1992, they have seen only two stars as close as this gas cloud to the black hole. The crucial difference is that those stars "passed unharmed through their closest approach, (while) the gas cloud will be completely ripped apart by the tidal forces around the black hole," Gillessen said.

This particular cold cloud (about 550 Kelvin or 280 degrees Celsius) may have formed when gas pushed by stellar winds from two nearby stars collided, and is glowing under the strong ultraviolet radiation from surrounding hot stars. As the cloud skirts the gravitational influence of the black hole, it will come within about 40 billion kilometers 250 times the distance between Earth and the sun of the event horizon, the limit beyond which nothing, not even light, can escape.

Even at that distance, the gas will get stretched out, with probably half spiraling into the black hole and the rest flung outward.

As the cloud falls towards the black hole – its current velocity is about 2,350 kilometers per second, twice what it was seven years ago – it will interact with the hot gas present in the accretion flow around the black hole and become disrupted by turbulent interaction.

Thanks to the Very Large Telescope's years of observations of the black hole at many different wavelengths, the scientists were able simulate the time evolution of the cloud and predict that the temperature of the should increase rapidly to several million Kelvin near the black hole, dramatically increasing X-ray emissions.

Explore further: Professional and amateur astronomers join forces

More information: This research was presented in a paper "A gas cloud on its way towards the super-massive black hole in the Galactic Centre", by S. Gillessen et al., to appear in the 5 January 2012 issue of the journal Nature. DOI: 10.1038/nature10652

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rynox
4.8 / 5 (4) Dec 14, 2011
"Falling into Milky Way's central black hole"... p'shaw... That's nothing- I just signed up for an HDHP/HSA insurance plan.
Cave_Man
1.6 / 5 (16) Dec 14, 2011
"In a few years"? Wouldn't this have happened several tens of thousands of years ago due to the speed of light not even including gravitational time distortion or the fact that nothing can really enter a black hole because if you were to travel toward a black hole the universe would evolve at an ever increasing rate until the moment you cross the Schwartzchild horizon at which point an infinite amount of time will have passed in the outside universe.

Black holes fascinate me, just the word black hole shows how little we know about them. Singularity is slightly more definitive but still woefully simplistic compared to the reality of a phenomenon that destroys what we consider to be reality.

Heh.
bewertow
4.2 / 5 (9) Dec 14, 2011
@Cave Man

Obviously this happened a long time ago, you noob. Everyone knows that. The point is that we get to observe it "in a few years."
0FET
not rated yet Dec 14, 2011
is anyone aware of how strongly the ionosphere on Earth is going to be affected in the night hours by the additional X-ray source? Of course no Mögel-Dellinger effect I'd presume :-)
douglas2
4 / 5 (1) Dec 14, 2011
@Cave Man
the fact that nothing can really enter a black hole because if you were to travel toward a black hole the universe would evolve at an ever increasing rate until the moment you cross the Schwartzchild horizon at which point an infinite amount of time will have passed in the outside universe.


Objects can cross the event horizon, and do not see an infinite amount of time on the outside. This dilation, stopping objects from crossing the horizon, is observed by in Schwartzchild time, not proper time.
ED__269_
1 / 5 (4) Dec 14, 2011
thats crock.

get to observe jack? show me your equations/observations that predict the decay in 2 years?
ED__269_
1 / 5 (4) Dec 14, 2011
show me any calculations that decay a gas cloud.
Pirouette
1.6 / 5 (7) Dec 14, 2011
What we are seeing now happened long ago. Therefore, the cloud has already been swallowed up long ago and no longer exists. Since the black hole is a part of our observable universe, but the present pictures are of the past, how do they know that the black hole hasn't already consumed the cloud, the stars in that region, has gotten much bigger and has already consumed all of the stars and gas in the center of the Milky Way, but our telescopes can't detect that the black hole has moved closer our way until another million years have passed?
Pirouette
1.7 / 5 (6) Dec 14, 2011
@Cave Man

bewertow says:
Obviously this happened a long time ago, you noob. Everyone knows that. The point is that we get to observe it "in a few years."

now now, be nice. . :)
I will look forward to the new pictures. .it would be better if they were in TRUE color instead of false. But maybe true color might be too washed out. Who knows?
BTW. . .i'm not a researcher for black holes
TrueProphecy
5 / 5 (1) Dec 14, 2011
Just a thought tell me if this is nonsense;
Say this event is happened a thousand yrs ago, this means the light took a thousand yrs to transmit this image, so say there was an effect on earth from this event then this effect would take a thousand yrs maybe more to reach us, so this event could be in real time. A bit of a head twister but try to see where I am coming from
astro_optics
1.8 / 5 (10) Dec 14, 2011
and how this impacts on CLIMATE CHANGE?
Cave_Man
2.3 / 5 (3) Dec 14, 2011

~50k lightyears is the distance, thats 50k years not even close to 1 million. gravity is also supposed to travel at the speed of light so unless there is some independent variable with which to measure any possible increases or changes in the gravitational force (which I understand is only used as an ambiguous relative coordinate system).

I may not be a mathematician but I understand science and while I may assume too much I think the whole field needs more new ideas and imagination.

i understand that what we observe as the event horizon is not the black hole, but think about it chance are the only black hole in there is the first tiny point which tore spacetime, everything outside that point is just frozen in time compared to us, we cant see past some relativistic horizon proportional to the gravitational mass but that's not the end of the story. Who says what happens in there is speculating IMHO.
Deesky
4 / 5 (4) Dec 14, 2011
the cloud has already been swallowed up long ago and no longer exists. Since the black hole is a part of our observable universe, but the present pictures are of the past, how do they know that the black hole hasn't already consumed the cloud

The concept of 'NOW' is ill defined when dealing with large distances and different reference frames. What may or may not have happened 'NOW' is of little consequence as we cannot be aware of any events until the light (or gravity) from those events can reach us.
Cave_Man
2 / 5 (4) Dec 14, 2011
Just a thought tell me if this is nonsense;
Say this event is happened a thousand yrs ago, this means the light took a thousand yrs to transmit this image, so say there was an effect on earth from this event then this effect would take a thousand yrs maybe more to reach us, so this event could be in real time. A bit of a head twister but try to see where I am coming from


Not that complicated, the early universe could be a hillbilly riding one of the horses of the apocalypse right 'Now' but we wont see it for 13 billion years. If the sun exploded at the speed of light toward us we wouldn't know a damn thing for 8 minutes.

But that lends the question of what time is the real time?

Thats whats very interesting imo, a black hole may only be a few billion years old relative to the big bang internally right? Not that it's useful to measure things that way.
Deesky
4.8 / 5 (6) Dec 14, 2011
i understand that what we observe as the event horizon is not the black hole, but think about it chance are the only black hole in there is the first tiny point which tore spacetime, everything outside that point is just frozen in time compared to us

You need to take account of different reference frames. An outside observer looking at someone falling towards a BH event horizon will see him slowing down more and more while his image becomes more and more red-shifted. It will appear as if he were stuck in place for eternity while getting dimmer.

However, from the infalling person's point of view, nothing much special will seem to happen (for large BHs) as he crosses the EH, but make no mistake, he will be spaghettified when he gets too close. It's just a 'trick' of perspective.
Deesky
5 / 5 (5) Dec 14, 2011
But that lends the question of what time is the real time?

There is no 'real' time. Time is relative, to coin a phrase. This was the revolution in our understanding of time (and space) since Einstein, compared with Newton's day notion of absolute time.
kochevnik
1.5 / 5 (8) Dec 14, 2011
gravity is also supposed to travel at the speed of light..
Yeah that's the dogma. Were it true planets would spiral into the sun, and there would be a disparity between their orbits and the misalligned centripetal acceleration vector. No, gravity is instantaneous.

It's interesting to note that gravity involves large bodies which might be fundamentally unworkable to sending FTL signals. So causality might be preserved. I have no idea about that I'm speculating.
kochevnik
1.7 / 5 (9) Dec 14, 2011
There is no 'real' time. Time is relative, to coin a phrase. This was the revolution in our understanding of time (and space) since Einstein, compared with Newton's day notion of absolute time.
Time is an effect of the Doppler shift between incoming and outgoing phase waves, the difference which determines the "particle's" [standing wave's] kinetic energy. That's not in your Republican Houghton Mifflin physics book.
Deesky
5 / 5 (5) Dec 14, 2011
Yeah that's the dogma. Were it true planets would spiral into the sun, and there would be a disparity between their orbits and the misalligned centripetal acceleration vector. No, gravity is instantaneous.

That's a crock (unless you're still stuck in the Newtonian world). Not only are there good theoretical reasons why gravity propagates at c, but also due to experimental measurements of relativistic orbital decay rates from pulsars, which are in agreement.
Deesky
5 / 5 (7) Dec 14, 2011
Time is an effect of the Doppler shift between incoming and outgoing phase waves, the difference which determines the "particle's" [standing wave's] kinetic energy. That's not in your Republican Houghton Mifflin physics book.

Oh I see, you are a crank. I won't waste any more time on you.
Shelgeyr
2.3 / 5 (3) Dec 14, 2011
I'm going to put aside my biases regarding the existence or not of black holes, and just roll with the premise of the article for a moment.

My beef here is the portrayal of the event as a terrible negative, to whit:

Disaster looms for gas cloud falling into...


It is NOT a disaster! It is meant to be! It is a predestined consummation, a joyous - nay orgasmic union!

To-MAY'-to, To-MAH'-to.

Except, of course, that I don't know anyone who actually says "To-MAH'-to".

My point, if I actually have one and I think I do, is that astronomy is esoteric enough without the coup-de-grace of a needlessly dour spin being put on things.
Graeme
5 / 5 (3) Dec 15, 2011
@Pirouette: in true colour they would be blank due to looking through dust.
If gas radiates as it approaches the black hole it should be possible to determine the spin of the central hole. Hopefully there is continuous monitoring happening, not just the VLT.
Shelgeyr
2.6 / 5 (5) Dec 15, 2011
@Cave_Man asked:

But that lends the question of what time is the real time?


Well, since all units of measurements and their corresponding scales are arbitrary, I'm going to go with "It's 11:12 PM, Central Time (USA)" because that's what my cell phone says.
Shelgeyr
2.8 / 5 (6) Dec 15, 2011
@Graeme postulates:
If gas radiates as it approaches the black hole it should be possible to determine the spin of the central hole.


Due to conservation of angular momentum, if the black hole itself is an infinitesimal gravitational point source, wouldn't its spin be infinite? And for that matter, how can a point source even be said to spin? What is there there that can be said to be spinning?
Pirouette
1.8 / 5 (5) Dec 15, 2011
@Graeme. . . .agreed. . .out of the blackness of outer space, a gray cloud of dust swirls in a spiral vortex towards an unseen, colorless form, emitting a thin stream of escaping radiation from both poles which is only detected by the white light of far off starlight.
Is that about right? :)
jsa09
2 / 5 (3) Dec 15, 2011
Due to conservation of angular momentum, if the black hole itself is an infinitesimal gravitational point source, wouldn't its spin be infinite? And for that matter, how can a point source even be said to spin? What is there there that can be said to be spinning?


Which gets us back to what cave-man said. things fall in and accelerate that acceleration causes rest of universe to speed up. That means it takes infinity to reach center. That means there is nothing in point source yet because infinite time has not happened yet. That means black hole is not point source. That means it can spin.
Graeme
5 / 5 (2) Dec 15, 2011
@Shelgeyr the angular momentum is not infinite as it is conserved (well sort of, some angular and linear momentum may be radiated away in gravitational waves). However a spinning black hole causes space to wrap around the hole, and it may be hundreds of time per second near the event horizon. By the approx calculation for gravitomagnetic field B=GL/2ccrrr where L is angular momentum, and r is radius (here 40billion km) c and G are the constants you can work out L if you can see the effects of B.

@Pirouette : The grey dust I am thinking of is the milky way smoke- it blocks 30 magnitudes of light at the galactic centre.
kochevnik
1.8 / 5 (10) Dec 15, 2011
That's not in your Republican Houghton Mifflin physics book.
Oh I see, you are a crank. I won't waste any more time on you.
Oh I see you are a conservative. I won't waste any more time on you.
stardust magician
1 / 5 (1) Dec 15, 2011
Here's the real scoop!

h**p://w*w.mpe.mpg.de/News/PR20111214/text.html

fix the * appropriately.
MarkyMark
1 / 5 (1) Dec 15, 2011
"In a few years"? Wouldn't this have happened several tens of thousands of years ago due to the speed of light not even including gravitational time distortion [q/]

ouch! What we are seeing is a few thousand years ago as will be the upcomming show that cloud is going to make


or the fact that nothing can really enter a black hole because if you were to travel toward a black hole the universe would evolve at an ever increasing rate until the moment you cross the Schwartzchild horizon at which point an infinite amount of time will have passed in the outside universe. [q/]

bear in mind that to the fallers perspective time is moving normally and if the faller was to look behind it it would see the universe accelerating in time. Its a matter of perspective.

theon
1.4 / 5 (5) Dec 15, 2011
Gas clouds with mass comparable to the earth, predicted in 1996, are plenty, they make up the galactic dark matter. For this theory the present 3 earth mass weight is a confirmation, not an accident. These clouds, by themselves as large as the sun, also feed the black holes, in tandem with forming stars in the bulge and globular star clusters, as was modeled recently, and supported by these observations. Interestingly, there are the regimes of rather small (few solar masses) and very large (several billion solar masses) black holes, and at the crossover there is a maximum in the black hole growth and in the star formation rate.
Nanobanano
3.4 / 5 (7) Dec 15, 2011
theon:

If your theory is true, why hasn't the Earth accreted more than at most a few inches worth of material since it was first here?

Why do none of the other terrestrial planets or moons show evidence of accretion, pretty much since they were first created?

Any such clouds of matter should be encountered constantly if they exist.

But guess what? Not even the gas giants have accreted much of anything since they were first created. Uranus is actually colder than it "should be" in the standard model of the solar system, so clearly, it hasn't had a significant "accretion event" since before any of the other planets...

If the stars were just moving around in gas clouds, we would be in deep shit.

The planets would experience drag forces and chaotic orbits, as they encountered mass on different momenta vectors, and of course Earth would gain millimeters or even inches of average soil deposition at a time, and we would know this pretty obviously...
Noumenon
4.6 / 5 (53) Dec 15, 2011
That's not in your Republican Houghton Mifflin physics book.
Oh I see, you are a crank. I won't waste any more time on you.
Oh I see you are a conservative. I won't waste any more time on you.


As pointed out by Deesky, you are ignorant of basic physics. Go away, troll.
Nanobanano
3.5 / 5 (6) Dec 15, 2011
But I mean, if we went through a 3 earth mass cloud of dust, and it was distributed somewhat evently, most of it would be picked up by the Sun and the Gas Giants, but that wouldn't be peaceful proces.

Suppose the Solar System was moving 1km/s relative to the Cloud....

This would SEVERELY alter the orbits of the gas giants relative to the Sun and relative to the Earth, by the time their gravity captured the material, due to conservation laws.

In some cases, moons' orbits would become unstable and either decay inward, or be ejected from the system, or collide with other planets.

It would be complete and utter chaos in the SS for centuries or even millenia, and possibly (PROBABLY) destroy life on the Earth...
Nanobanano
2.9 / 5 (7) Dec 15, 2011
I mean, nevermind a collision with a cloud.

let's just magically increase the Sun's gravity by like a half Earth mass, and magically increase each of the Gas giant's mass by half an earth mass, and assume Earth itself "somehow" manages to avoid picking up an immediately catastrophic amount of extra mass...

What do you figure that would do to the orbits of everything?

The Sun's gravity would increase by 0.33 parts per million, which is a "tiny" amount compared to what it is now, but then pretty much everything in the SS would be SCREWED and fall into it over the next several years, decades, or centuries.

This is why I don't buy the whole dust cloud thing, or for that matter, most of cosmology.

If such clouds and "nebula" were really what scientists claim they are, we just HAPPEN to have never encountered one in the history of the universe...yeah, right...
Nanobanano
2.9 / 5 (7) Dec 15, 2011
Hey, if there is so much Dark Matter floating around between the Stars, why don't we detect local gravitational perturbations?

Based on the alleged galactic average, there should be about 4 solar masses worth of Dark Matter within a radius of about 3 or 4 light years of the Sun.

Yet CONVENIENTLY absolutely no significant gravitational perturbations have been found since oh, the last time we named a PLANET!...

If Dark Matter exists, it certainly doesn't obey anything at all like Newton or Einstein's gravity, else we'd see these local perturbations.

Not to mention, the Sun and Gas Giants would be constantly gaining "unexplained mass" as we passed through the alleged DM clouds that would need to be evenly spaced in the galaxy.

So explain that, standard model believers.

The whole field of cosmology is riddled with more holes than a piece of swiss cheese.
Vendicar_Decarian
4.2 / 5 (5) Dec 15, 2011
"Hey, if there is so much Dark Matter floating around between the Stars, why don't we detect local gravitational perturbations?" - Nano

First, the term "dark matter" is a place holder. We don't know what it is, although it's name implies that the anomaly is matter.

Second, such matter, if it were all in one lump and close enough would be detectable. But if far enough away, or distributed more finely, then it would not be.

Third, I doubt if much, if any effort is being expended in looking for suggestive variances in the orbits of the members of the ort cloud.

Nanobanano
2 / 5 (6) Dec 15, 2011
V_D:

See you hit on something I thought of, but didn't mention yesterday.

What if Dark Matter isn't matter at all, and has no gravity at all?

What if Dark Matter is literally a 5th force that is linear, represented by a field, and has no "particle" carrier?

en.wikipedia.org/wiki/File:GalacticRotation2.svg

I mean, the gravity curve is 1/r^2, but the star curve evens out near the edge of the hub.

And line A isn't even what it should be. If you had a SMBH in the heart of a galaxy, then stars should orbit assymptotically near light speed, at least until they are too close to hold themselves together. The left side of both curves is wrong, and should be a vertical assymptote of V as "infinity" when D is 0.

1/R^2 approaches infinity as R approaches 0, therefore a stable orbit velocity would also approach infinity, but of course in relativity it's limited to C.

So neither the "hypothetical" star line isn't even right to begin with.
Nanobanano
2.2 / 5 (5) Dec 15, 2011
That is, unless there's another spike to the left side of the red and blue curves which simply isn't plotted on that graph...

We KNOW matter in an accretion disk on a black hole flies around at nearly light speed as it falls into the SMBH, so this graph should DEFINITELY have a "relativized" vertical assymptote of V = C when R = 0.

That would also seem to undermind "MOND" theory, which would not explain the DIP on the left side of the graph.

I hope you can see what I'm talking about, and why it's not on the graph is a mystery to me...they just sort of pick up the curve apparently on the outer edges of the hub, instead of following it all the way into the SMBH, which makes a huge, huge difference...
Nanobanano
2.5 / 5 (4) Dec 15, 2011
What if Dark Matter does exist, and it is a "rubber band"?

And it behaves like a "rubber band" tying two particles together. There isn't even a mystical "attractiveness", but rather, every particle in the universe has a connection to every other particle, and these "rubbers" have very high elasticity individually, so that you woudln't notice them locally.

But if you made a big wad of them on galactic scales, then you have jillions and jillions of these "Rubbers" in a big invisible knot tying all the matter together, and therefore, it is much less elastic, mimmicking a "force" (like Tension,) over a very long distance of super-massive objects, such as galaxies.

Like if you imagine a ball of rubber bands (a galaxy,) it is not nearly as elastic as any one rubber band (representing two connected particles).

If there are a trillion solar masses in a galaxy, then that's um, 2E42kg, and if a mole of hydrogen is a gram, then that would be:

1.2044274E69! (factorial)
Nanobanano
2.5 / 5 (4) Dec 15, 2011
Yes, there would be:

1.2044274E69! number of Rubbers connecting all the atoms to one another.

Now maybe the Rubbers have a maximum length equal to a few Galactic Radii.

And so, an example of this would be one of those circular swings like you see at a carnival. There is a rod on a swivel holding a bucket that the rider sits in, and the rod keeps tension so that as the rid goes, they aren't thrown away.

The Rubbers are the same principle, but much more elastic. Like ridiculously elastic so that you'd never notice them on Earthly scales.

And so, the Rubbers would be able to hold the outer Stars in circular orbits, even at very high velocities, even though Gravity by itself isn't strong enough.
Nanobanano
2.2 / 5 (5) Dec 15, 2011
And for stars that are very close to the center, the Rubbers wouldn't make much difference, because they wouldn't be stretched to maximum tension yet, explaining why close stars appear to follow Newton's Laws...
kochevnik
2 / 5 (6) Dec 16, 2011
That's not in your Republican Houghton Mifflin physics book.
Oh I see, you are a crank. I won't waste any more time on you.
Oh I see you are a conservative. I won't waste any more time on you.
As pointed out by Deesky, you are ignorant of basic physics. Go away, troll.
How is that? You're ignorant about Mach. That makes you a grandstanding windbag who doesn't know squat. You'd be there nodding with the flat-earthers at Galileo's trail. The trolls here are conservatives. But don't let a fact like that waste precious space in your skull.
IamMeuru
2.3 / 5 (3) Dec 17, 2011
I bet we are already in the black hole and the area we observe as the black hole is the exit...
Shelgeyr
1 / 5 (2) Dec 21, 2011
I would just like to point out that the Oort Cloud (supposedly starting roughly a light-year out from the sun) is merely hypothetical - not even "theoretical" as there has never been any direct observation of anything there, unlike the Kuiper Belt (at 30 to 50 AU, and in which we can see actual objects), or the Kuiper-belt-overlapping "Scattered disc" region.

So I can guarantee that nobody is looking for variances in the orbits of members of the Oort Cloud, since have no knowledge of any such members.

Please note: I'm not saying there is no Oort Cloud, not at all, just stating the obvious - that we have no evidence of it. We can hypothesize all we want - and the hypothesis may even one day be proved true - but at this point it remains just that: a hypothesis.
Seeker2
1 / 5 (1) Jan 09, 2012
Not only are there good theoretical reasons why gravity propagates at c, but also due to experimental measurements of relativistic orbital decay rates from pulsars, which are in agreement.
I've fought this gravity battle for too long. I finally deduced gravitational radiation propagates but the gravitational field doesn't. The gravitational field is actually part of the object because the field and object are together a reconfiguration of spacetime. I think gravitational radiation is actually heat waves generated by motion through spacetime. They're probably drowned out by the CMBR, but that needs to be checked. Anyway it may take light billions of years to get here but by that time the gravitational field has long gone, as well as its gravitational radiation. So what you see with a gravitational wave detector, along with its radiation, is a current event - the greatest breakthrough in astronomy since the telescope. But don't try to relate anything you see to any current event.
Seeker2
1 / 5 (2) Jan 09, 2012
I'm concerned however about the zero point energy wiping out the gravitational effects in the gravitational wave detectors.
Seeker2
1 / 5 (2) Jan 09, 2012
To-MAY'-to, To-MAH'-to.

Except, of course, that I don't know anyone who actually says "To-MAH'-to".[/]True. I think it's tow-mah-tow. Trivial technicality, I know.

My point, if I actually have one and I think I do, is that astronomy is esoteric enough without the coup-de-grace of a needlessly dour spin being put on things.

Seeker2
1 / 5 (2) Jan 09, 2012
That was not my point. Sorry. Garbage in garbage out.
Seeker2
1 / 5 (2) Jan 09, 2012
@Graeme postulates:
If gas radiates as it approaches the black hole it should be possible to determine the spin of the central hole.


Due to conservation of angular momentum, if the black hole itself is an infinitesimal gravitational point source, wouldn't its spin be infinite? And for that matter, how can a point source even be said to spin? What is there there that can be said to be spinning?
An infinite spin also means an infinite centrifugal force, meaning I guess the BH would fly apart. But since it doesn't what goes on inside the BH could be very interesting. For example the matter distribution of particles would depend on the BH's spin. Equal mass particles particles would aggregate in concentric rings inside the BH, sort of like a giant centrifuge. Also there may be some correlation between the size of the event horizon and this distribution of spinning matter.
yyz
5 / 5 (1) Jan 09, 2012
A paper recently posted on arXiv contains computer sims of several possible encounter scenarios for cloud G2 and details a few predictions of what this encounter may present: http://arxiv.org/...14v1.pdf

Now where are those numerical sims from the [insert favorite:plasma cosmology, anti-gravity matter, gravitohydrodynamics, AWT, etc] people?
Seeker2
1 / 5 (2) Jan 09, 2012
Gas clouds with mass comparable to the earth, predicted in 1996, are plenty, they make up the galactic dark matter.
But...are they really dark?
Seeker2
1 / 5 (2) Jan 09, 2012
If Dark Matter exists, it certainly doesn't obey anything at all like Newton or Einstein's gravity, else we'd see these local perturbations. So explain that, standard model believers.
Dark matter was invented to explain the gravitational wells where galaxies form, but really nothing inside the galaxy. Ad hoc, you might say. Actually dark matter is a region of higher than normal energy density spacetime on a galactic scale, just as particles are a region of higher energy density on a microscopic scale. I believe you can see these regions in the CMBR that are destined to become galaxies. So does that make me a believer? Scary.

The whole field of cosmology is riddled with more holes than a piece of swiss cheese.
It's difficult to perform table-top experiments. You just have to watch and make an educated (maybe) guess.
Graeme
not rated yet Jan 23, 2012
@seeker2 says: An infinite spin also means an infinite centrifugal force

You are on the right track with a point containing no angular momentum. What you get is a ring singularity. See https://secure.wi...gularity
Vendicar_Decarian
5 / 5 (2) Jan 23, 2012
"However, from the infalling person's point of view, nothing much special will seem to happen (for large BHs) as he crosses the EH" - Yum yum

That is true as long as he keeps his eyes closed or if he has his head in a box.

If he looks outside he would see a circle of darkness below him that grows wider and wider until it extends to the horizon and then closes in around him from behind.

On the horizon he would see a bright ribbon of light with the star field around him repeated many times, and stars flattened to the horizon as their light orbits the BH one or more times before it enters his eyes.

But inside a box, the laws of nature would pretty much play out as normal as he falls through the event horizon.

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