Gravitational waves help understand black hole weight gain

Oct 17, 2013
Gravitational waves distort space, altering the regular signals from pulsars received by the CSIRO Parkes Radio Telescope. Credit: Swinburne Astronomy Productions.

Supermassive black holes: every large galaxy's got one. But here's a real conundrum: how did they grow so big?

A paper in today's issue of Science pits the front-running ideas about the growth of supermassive against observational data—a limit on the strength of gravitational waves, obtained with CSIRO's Parkes radio telescope in eastern Australia.

"This is the first time we've been able to use information about gravitational waves to study another aspect of the Universe—the growth of massive black holes," co-author Dr Ramesh Bhat from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) said.

"Black holes are almost impossible to observe directly, but armed with this powerful new tool we're in for some exciting times in astronomy. One model for how black holes grow has already been discounted, and now we're going to start looking at the others."

The study was jointly led by Dr Ryan Shannon, a Postdoctoral Fellow with CSIRO, and Mr Vikram Ravi, a PhD student co-supervised by the University of Melbourne and CSIRO.

Einstein predicted gravitational waves—ripples in space-time, generated by massive bodies changing speed or direction, bodies like pairs of black holes orbiting each other.

When galaxies merge, their central black holes are doomed to meet. They first waltz together then enter a desperate embrace and merge.

"When the black holes get close to meeting they emit gravitational waves at just the frequency that we should be able to detect," Dr Bhat said.

Played out again and again across the Universe, such encounters create a background of gravitational waves, like the noise from a restless crowd.

Astronomers have been searching for gravitational waves with the Parkes radio telescope and a set of 20 small, spinning stars called pulsars.

Pulsars act as extremely precise clocks in space. The arrival time of their pulses on Earth are measured with exquisite precision, to within a tenth of a microsecond.

When the waves roll through an area of space-time, they temporarily swell or shrink the distances between objects in that region, altering the arrival time of the pulses on Earth.

The Parkes Pulsar Timing Array (PPTA), and an earlier collaboration between CSIRO and Swinburne University, together provide nearly 20 years worth of timing data. This isn't long enough to detect gravitational waves outright, but the team say they're now in the right ballpark.

"The PPTA results are showing us how low the background rate of is," said Dr Bhat.

"The strength of the gravitational wave background depends on how often spiral together and merge, how massive they are, and how far away they are. So if the background is low, that puts a limit on one or more of those factors."

Armed with the PPTA data, the researchers tested four models of black-hole growth. They effectively ruled out black holes gaining mass only through mergers, but the other three models are still a possibility.

Dr Bhat also said the Curtin University-led Murchison Widefield Array (MWA) radio telescope will be used to support the PPTA project in the future.

"The MWA's large view of the sky can be exploited to observe many pulsars at once, adding valuable data to the PPTA project as well as collecting interesting information on pulsars and their properties," Dr Bhat said.

Explore further: Image: Galactic wheel of life shines in infrared

More information: "Gravitational-Wave Limits from Pulsar Timing Constrain Supermassive Black Hole Evolution" Science, 2013.

Journal reference: Science search and more info website

Provided by International Centre for Radio Astronomy Research

4.3 /5 (39 votes)

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scottfos
3.5 / 5 (6) Oct 17, 2013
good article in Scientific American a month or 3 ago about different approaches to 'listening' to these gravitational waves. don't think i'm allowed to enter the full url but it's scientificamerican / article.cfm?id=gravitational-wave-detectors-get-ready-to-hunt-for-the-big-bang
hemitite
2.1 / 5 (14) Oct 17, 2013
Gravitational waves have been indirectly detected in the changing orbits of double neutron stars where the observed energy loss matches up well with the predictions of Special Relativity. If GW's are not detected, then something is spacetime may be damping them out close to their source. And if so, what happens to all of that energy?
Tuxford
1 / 5 (26) Oct 17, 2013
'Supermassive black holes: every large galaxy's got one. But here's a real conundrum: how did they grow so big?'

Easy. They grow like plants, sucking nutrients from the underlying etheric sub-quantum medium of undetectables that pervades all of space, and turning it into matter deep inside their cores. The more massive they have grown, the faster they grow.
vacuum-mechanics
1 / 5 (23) Oct 17, 2013
"This is the first time we've been able to use information about gravitational waves to study another aspect of the Universe—the growth of massive black holes," co-author Dr Ramesh Bhat from the Curtin University node of the International Centre for Radio Astronomy Research (ICRAR) said.

It seems that Einstein himself did not believe in the black hole.
Einstein predicted gravitational waves—ripples in space-time, generated by massive bodies changing speed or direction, bodies …..

The only problem is how the gravitational waves could propagate via empty space….
http://www.vacuum...=7〈=en
Neinsense99
2.3 / 5 (16) Oct 17, 2013
'Supermassive black holes: every large galaxy's got one. But here's a real conundrum: how did they grow so big?'

Easy. They grow like plants, sucking nutrients from the underlying etheric sub-quantum medium of undetectables that pervades all of space, and turning it into matter deep inside their cores. The more massive they have grown, the faster they grow.

Personally, I blame the sneaky companies that add sugar to mass throughout the universe. Have you looked at the ingredients for what they call primordial soup these days?
VendicarE
2 / 5 (7) Oct 17, 2013
"And if so, what happens to all of that energy?" - hematite

It vanishes into the fifth, sixth and 7th dimensions.
Urgelt
5 / 5 (4) Oct 17, 2013
It would be good to know the statistical confidence they attribute to their data analysis. Is this a five-sigma analysis? Three?

One?

They don't have many cases yet. They are up against sensitivity limits in their instruments. They're looking for an awfully subtle effect. In a case like this, the sigma is pretty important to report.
Shootist
1.5 / 5 (15) Oct 17, 2013
'Supermassive black holes: every large galaxy's got one. But here's a real conundrum: how did they grow so big?'

Easy. They grow like plants, sucking nutrients from the underlying etheric sub-quantum medium of undetectables that pervades all of space, and turning it into matter deep inside their cores. The more massive they have grown, the faster they grow.


Paging Dr. Manual, we have another cookoo for you.
Zephir_fan
Oct 18, 2013
This comment has been removed by a moderator.
mohammadshafiq_khan_1
Oct 19, 2013
This comment has been removed by a moderator.
typicalguy
3.4 / 5 (5) Oct 19, 2013
First off, we've never directly measured gravitational waves. Second, this article is saying what exactly? They're way too vague. As I read it, either they found indirect evidence of extremely weak gravitational waves or they found no gravitational waves at all. Which was it?
Tuxford
1 / 5 (13) Oct 19, 2013
Easy. They grow like plants, sucking nutrients from the underlying etheric sub-quantum medium of undetectables that pervades all of space, and turning it into matter deep inside their cores. The more massive they have grown, the faster they grow.


Actually, the concept is quite sophisticated, and depends on an understanding an appreciation of dynamic systems theory, which few outside electrical engineering can truly appreciate. I am simply trying to put the concept in simple terms that might be understood here. Unless you have closed many servo loops, I doubt you would have a chance to grasp the implications of the systems model. Instead, most fall back on faulty conclusions, intellectual certainty, and physical LAWS. Nature isn't Texas. And it isn't math.
TheGhostofOtto1923
1 / 5 (7) Oct 19, 2013
How did mohammad exceed the 1000 character limit I wonder? Magic?
ACW
1 / 5 (1) Oct 19, 2013
I was also unaware of the gravitational "wave" detection and as was already pointed out, the article only references the strength of the gravity, not the wave.

I am also unsure about circumventing the character limit.
Q-Star
3.6 / 5 (9) Oct 19, 2013
How did mohammad exceed the 1000 character limit I wonder? Magic?

Dark Matter Exists
Posted on August 21, 2006 by Sean Carroll
The great accomplishment of late-twentieth-century cosmology was putting together a complete inventory of the universe. We can tell a story that fits all the known data, in which ordinary matter (every particle ever detected in any experiment) constitutes only about 5% of the energy of the universe, with 25% being dark matter and 70% being dark energy. The challenge for early-twenty-first-century cosmology will actually be to understand the nature of these mysterious dark components. A beautiful new result illuminating (if you will) the dark matter in galaxy cluster 1E 0657-56 is an important step in this direction. (Here's the press release, and an article in the Chandra Chronicles.)
A prerequisite to understanding the dark sector is to make sure we are on the right track. Can we be sure that we haven't been fooled into believing in dark matter and dark energy? After all, we only infer their existence from detecting their gravitational fields; stronger-than-expected gravity in galaxies and clusters leads us to posit dark matter, while the acceleration of the universe (and the overall geometry of space) leads us to posit dark energy. Could it perhaps be that gravity is modified on the enormous distance scales characteristic of these phenomena? Einstein's general theory of relativity does a great job of accounting for the behavior of gravity in the Solar System and astrophysical systems like the binary pulsar, but might it be breaking down over larger distances?
A departure from general relativity on very large scales isn't what one would expect on general principles. In most physical theories that we know and love, modifications are expected to arise on small scales (higher energies), while larger scales should behave themselves. But, we have to keep an open mind — in principle, it's absolutely possible that gravity could be modified, and it's worth taking seriously.
Q-Star
3.5 / 5 (8) Oct 19, 2013
Sean Carrol cont:
Furthermore, it would be really cool. Personally, I would prefer to explain cosmological dynamics using modified gravity instead of dark matter and dark energy, just because it would tell us something qualitatively different about how physics works. (And Vera Rubin agrees.) We would all love to out-Einstein Einstein by coming up with a better theory of gravity. But our job isn't to express preferences, it's to suggest hypotheses and then go out and test them.
The problem is, how do you test an idea as vague as "modifying general relativity"? You can imagine testing specific proposals for how gravity should be modified, like Milgrom's MOND, but in more general terms we might worry that any observations could be explained by some modification of gravity.
But it's not quite so bad — there are reasonable features that any respectable modification of general relativity ought to have. Specifically, we expect that the gravitational force should point in the direction of its source, not off at some bizarrely skewed angle. So if we imagine doing away with dark matter, we can safely predict that gravity always be pointing in the direction of the ordinary matter. That's interesting but not immediately helpful, since it's natural to expect that the ordinary matter and dark matter cluster in the same locations; even if there is dark matter, it's no surprise to find the gravitational field pointing toward the visible matter as well.
What we really want is to take a big cluster of galaxies and simply sweep away all of the ordinary matter. Dark matter, by hypothesis, doesn't interact directly with ordinary matter, so we can imagine moving the ordinary stuff while leaving the dark stuff behind. If we then check back and determine where the gravity is, it should be pointing either at the left-behind dark matter (if there is such a thing) or still at the ordinary matter (if not).
Q-Star
4.2 / 5 (5) Oct 19, 2013
How did mohammad exceed the 1000 character limit I wonder? Magic?


I suppose the same way I just did. It's not magic, not AWT & and not Plasma. Some of us refrain from doing out courtesy but trolls have no sense of etiquette or manners. Rules mean nothing to the vandals.
ubavontuba
1.5 / 5 (12) Oct 19, 2013
When galaxies merge, their central black holes are doomed to meet. They first waltz together then enter a desperate embrace and merge.
How can galaxies merge without being in close relative proximity and velocity to begin with? Wouldn't they mostly just slide right through each other?

Also, in regards to the central black holes, isn't this essentially a two-body problem? How do two relatively high velocity/angular momentum gravitational bodies merge, when two gravitational bodies can't capture one another to begin with?

Does the density at the galactic cores account for this? Shouldn't we then see spectacular collision results in virtually every wavelength?

uba confused

ubavontuba
1.5 / 5 (13) Oct 20, 2013
Gravitational waves help understand black hole weight gain
Who writes these awful headlines?

Shouldn't that be, ...mass gain?

And as it appears no such gravitational wave has been detected, shouldn't it read, "Hypothesized gravitational waves may help...?

ubavontuba
1.1 / 5 (11) Oct 20, 2013
How do two relatively high velocity/angular momentum gravitational bodies merge, when two gravitational bodies can't capture one another to begin with?
The black holes are supposed to merge easier just because of radiation of gravitational waves at their proximity. They do behave like the molten planetary bodies, where strong tidal forces do apply: once such a bodies appear in proximity, the loses of energy during mutual motion of planets will cause their merging undeniably.
Even so, this can't happen unless their relative momentums are minimal to begin with.

YORD
not rated yet Oct 20, 2013
Anyone know how fast G waves move?
Fleetfoot
2.5 / 5 (2) Oct 20, 2013
When galaxies merge, their central black holes are doomed to meet. They first waltz together then enter a desperate embrace and merge.
How can galaxies merge without being in close relative proximity and velocity to begin with? Wouldn't they mostly just slide right through each other?


Good question. Have you seen the film "Galaxy Quest"? there a scene where the ship goes through a filed of "magnetic mines" and passes close enough to collect a following. That means the ship's momentum is shared with the mines slowing it down. The same effect happens to every star of one galaxy passing through the other due to gravity.

How do two relatively high velocity/angular momentum gravitational bodies merge, when two gravitational bodies can't capture one another to begin with?


Orbital energy is emitted in the form of gravitational waves, that is what Hulse and Taylor measured in the binary system PSR B1913+16.
Neinsense99
1 / 5 (5) Oct 20, 2013
How did mohammad exceed the 1000 character limit I wonder? Magic?

It remains due to the apparent death of the moderators. Imagine, if you will, someone at a computer reaching a certain threshold of stupidity and uncivility, beyond which their sensibilities cannot cope, resulting in sudden expiration as if the subject of a cartoon segment of a Monty Python film.
Fleetfoot
5 / 5 (1) Oct 20, 2013
Anyone know how fast G waves move?


They have no mass so they travel at c (the speed of light).
Neinsense99
1 / 5 (5) Oct 20, 2013
How did mohammad exceed the 1000 character limit I wonder? Magic?


Extra characters does not equal extra credibility. Does he expect cheating to spam a forum will impress anybody with active critical thinking capacity? FYI, re the Elixir Journal he claims publication in, that's a new journal that has no location specified, no apparent focus, uses a logo and name reminiscent of Elsevier, etc.: http://scholarlyo...2/06/93/
cantdrive85
1.4 / 5 (18) Oct 20, 2013
Gravitational waves help understand black hole weight gain

Yep, and turbulence from Pegasus' wing flaps limit global warming.

http://www.thunde...ence.htm

It's truly astounding that otherwise intelligent (somewhat) people actually invest themselves into the "discovery" of these fictional phenomena. Sadly it's been going on for sometime now...
"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén

Voila! See above.

"...magnificent mathematical garb which fascinates, dazzles and makes people blind to the underlying errors. The theory is like a beggar clothed in purple whom ignorant people take for a king ... its exponents are brilliant men but they are metaphysicists, not scientists..." Nikola Tesla New York Times, July 11, 1935, p23, c8

Yep, some time now...
IMP-9
4.5 / 5 (4) Oct 20, 2013
[quote]"We have to learn again that science without contact with experiments is an enterprise which is likely to go completely astray into imaginary conjecture." Hannes Alfvén[/quote]

How typical of you to produce quotes rather than any argument based on physics. It's funny you produce this quote in the exact same post that you criticise people for actually running the experiment to find gravitational waves. I'd say you're the one who isn't listening to what he said, you're much happier with your untested blind faith that they can't exist.

Tesla's comment is completely worthless as it contains no scientific criticism.
ubavontuba
1 / 5 (12) Oct 20, 2013
Good question. Have you seen the film "Galaxy Quest"? there a scene where the ship goes through a filed of "magnetic mines" and passes close enough to collect a following. That means the ship's momentum is shared with the mines slowing it down. The same effect happens to every star of one galaxy passing through the other due to gravity.
That's one of my favorite movies, but the towing of the magnetic mines, as depicted, is entirely impossible. Any "magnetic" mines thusly captured, must accelerate toward (and ultimately hit) the towing ship. The only way this could work is if the field was modulated for each mine. Gravity isn't modulated.

Orbital energy is emitted in the form of gravitational waves, that is what Hulse and Taylor measured in the binary system PSR B1913+16.
This is meaningless at the distances and relative momentum of colliding galaxies. And, this doesn't even take into account gravitational time dilation. An observable merger ...is an oxymoron.

Fleetfoot
4 / 5 (2) Oct 21, 2013
.. the towing of the magnetic mines, as depicted, is entirely impossible. Any "magnetic" mines thusly captured, must accelerate toward (and ultimately hit) the towing ship. The only way this could work is if the field was modulated for each mine. Gravity isn't modulated.


No but you would get the same effect if the ship went past at high speed and only imparted a small 'kick' the those it passed. Over many passes going through a galaxy, that adds up to a significant loss of momentum for the high speed star.

Orbital energy is emitted in the form of gravitational waves, that is what Hulse and Taylor measured in the binary system PSR B1913+16.
This is meaningless at the distances and relative momentum of colliding galaxies.


That depends on how close they pass. Even for a near miss, the effect will reduce the relative speeds and may be enough to allow capture and eventual merger.

Gravitational time dilation is negligible.
bluehigh
1 / 5 (12) Oct 21, 2013
Anyone know how fast G waves move?
They have no mass so they travel at c (the speed of light).


They don't exist. So they travel at zero velocity.

Can't drive 5 again. I can't figure out how to rate properly on an iPad.
Could be finger waves.

Who said gravity isn't modulated. Just a guess?

Varying distance from a mass changes the mass attraction. No modulation?

ubavontuba
1 / 5 (11) Oct 21, 2013
No but you would get the same effect if the ship went past at high speed and only imparted a small 'kick' the those it passed. Over many passes going through a galaxy, that adds up to a significant loss of momentum for the high speed star.
Sure, but for capture to occur, the merging galaxies must lose momentum in internal collisions, mostly between dust clouds ("atmospheric braking" of a sort). And for capture to result from this, their relative momentum must have been low to begin with.

That depends on how close they pass. Even for a near miss, the effect will reduce the relative speeds and may be enough to allow capture and eventual merger.
Sure, the cores can initially slow as a result of a braking effect produced from the colliding internal mass/es. Even then, it would take billions of years for for the results to settle out.

continued...

ubavontuba
1 / 5 (11) Oct 21, 2013
Gravitational time dilation is negligible.
Even though it's only an "optical illusion," an outside observer cannot see time pass at a black hole horizon.

Maybe they're thinking gravity waves aren't similarly constrained ...? Wouldn't that mean information can pass faster than the speed of light ...?

Fleetfoot
5 / 5 (3) Oct 21, 2013
Over many passes going through a galaxy, that adds up to a significant loss of momentum for the high speed star.

Sure, but for capture to occur, the merging galaxies must lose momentum in internal collisions, mostly between dust clouds ("atmospheric braking" of a sort).

No, that's the point. Gravitational drag doesn't require collisions, as each star of one galaxy passes millions of stars in the other, the small exchanges of momentum slow it down. Even quite distant passes can lose momentum as the outlier stars can interact yet remain bound to the host galaxy.

And for capture to result from this, their relative momentum must have been low to begin with.


Yes, otherwise you just get distortion of the galaxies.

Even then, it would take billions of years for for the results to settle out.


Not that long, perhaps hundreds of millions. This is a simulation of Andromeda and the Milky way:

http://www.youtub...4syBhj-A
Fleetfoot
5 / 5 (4) Oct 21, 2013
This is meaningless at the distances and relative momentum of colliding galaxies. And, this doesn't even take into account gravitational time dilation. An observable merger ...is an oxymoron.

Gravitational time dilation is negligible.

Even though it's only an "optical illusion," an outside observer cannot see time pass at a black hole horizon.


Based on the context (above) I thought you meant merger of galaxies, not the black holes.

Maybe they're thinking gravity waves aren't similarly constrained ...? Wouldn't that mean information can pass faster than the speed of light ...?


Gravitational waves ("gravity waves" are something different) are produced far outside the horizon from the system as a whole so that's not a problem.
ubavontuba
1 / 5 (10) Oct 22, 2013
No, that's the point. Gravitational drag doesn't require collisions, as each star of one galaxy passes millions of stars in the other, the small exchanges of momentum slow it down. Even quite distant passes can lose momentum as the outlier stars can interact yet remain bound to the host galaxy.
I can see that. The masses accelerate on approach, decelerate on escape, with a subsequent angular momentum exchange causing vector changes ...having an over all braking effect! ...I find that fascinating... The over all momentum is conserved, but the effect on each part of the system is ...awkward. Obviously, I've not worked with such large systems before.

And for capture to result from this, their relative momentum must have been low to begin with.
Yes, otherwise you just get distortion of the galaxies.
...as I suggested all along.

Not that long, perhaps hundreds of millions. This is a simulation of Andromeda and the Milky way:
Seen similar already. Very cool.

ubavontuba
1 / 5 (10) Oct 22, 2013
Based on the context (above) I thought you meant merger of galaxies, not the black holes.
It appears clear to me that I was commenting on the subject of the article, but I have the advantage of knowing what I was thinking when I wrote it. I'll give you a pass...

Maybe they're thinking gravity waves aren't similarly constrained ...? Wouldn't that mean information can pass faster than the speed of light ...?
Gravitational waves ("gravity waves" are something different) are produced far outside the horizon from the system as a whole so that's not a problem.
But in the context of the article, they're suggesting gravity waves might divulge information light cannot. So either the gravity waves must receive this information spontaneously, the article is in error, or I misunderstand the limitations of information and causality (probably the latter).

Fleetfoot
4.5 / 5 (2) Oct 22, 2013
But in the context of the article, they're suggesting gravity waves might divulge information light cannot. So either the gravity waves must receive this information spontaneously, the article is in error, or I misunderstand the limitations of information and causality (probably the latter).


The waves are a measure of how often BH mergers occur, they don't tell us anything from inside the BH at all.

There's a graphic here of how the waves are produced, I'm sure you've seen it:

http://upload.wik...Wavy.gif

This shows it in more detail

http://www.astron...aves.gif

Just as the Sun's gravity keeps the Earth in orbit but doesn't tell us anything about the interior, the mass of the BHs creates the waves but it's a system-wide effect, not something specific to the holes.
GSwift7
5 / 5 (1) Oct 23, 2013
Gravitational waves ("gravity waves" are something different) are produced far outside the horizon from the system as a whole so that's not a problem


No, gravity does not originate from the empty space outside the event horizon. The gravity of a black hole originates from the massive object at the center and extends through the event horizon as if it wasn't there. Magnetism cannot do that, nor can light. The gravitational waves originating from the merger of two black holes also originate from the objects at the center of the black holes. The fact that gravity is able to ignore the event horizon is not explained by modern theory. The inside of the event horizon remains a black box, beyond the limits of our theories. All modern physical theory fails at the event horizon.

How gravity works outside of the event horizon but originates from inside it remains a mystery. Solving that mystery would probably get you close to a GUT or TOE.
Fleetfoot
4 / 5 (2) Oct 23, 2013
Gravitational waves ("gravity waves" are something different) are produced far outside the horizon from the system as a whole so that's not a problem


No, gravity does not originate from the empty space outside the event horizon.


I didn't suggest it did, I said the gravitational waves are produced by the system as a whole, not either black hole individually.

The gravitational waves originating from the merger of two black holes also originate from the objects at the center of the black holes.


A single BH doesn't produce waves, the binary system is required.

The inside of the event horizon remains a black box, beyond the limits of our theories. All modern physical theory fails at the event horizon.


That is not true, if you use Kruskal-Szekeres coordinates for example, you can apply GR to the region inside as well as outside the event horizon and the metric is not singular at the event horizon. The theory only fails at the singularity.
ubavontuba
1 / 5 (10) Oct 24, 2013
I didn't suggest it did, I said the gravitational waves are produced by the system as a whole, not either black hole individually.
Whatever. It still appears from this article they're expecting information concerning the mergers of the event horizons which (I think) should not be available to an outside observer.

Fleetfoot
4.3 / 5 (3) Oct 24, 2013
I didn't suggest it did, I said the gravitational waves are produced by the system as a whole, not either black hole individually.
Whatever. It still appears from this article they're expecting information concerning the mergers of the event horizons which (I think) should not be available to an outside observer.


If you think what the system would be like a few weeks before merger, the BH would be still separate but very close and moving very rapidly round each other. That generates intense gravitational waves which rise to a peak around the time of merger. It is that burst of waves they are studying, not the merger itself.
GSwift7
5 / 5 (2) Oct 24, 2013
you can apply GR to the region inside as well as outside the event horizon and the metric is not singular at the event horizon. The theory only fails at the singularity


You can work out solutions to some of the terms, but that does not mean there is a real world analog for the situations those solutions describe.

One way to observationally prove whether that is true or not would be to detect gravitational waves from the merger of two black holes, which has not yet been done. If the two centers of mass continue to oscillate after they are both inside their combined event horizon, then what you suggest would seem to be true. On the other hand, some solutions suggest that they might suddenly collapse into a single object at the instant the two event horizon boundaries meet. That would indicate that physics inside the event horizon is fundamentally different than outside (a singularity in our equations all the way from the event horizon to the center).
GSwift7
5 / 5 (2) Oct 24, 2013
Whatever. It still appears from this article they're expecting information concerning the mergers of the event horizons which (I think) should not be available to an outside observer


Yeah, I've tried to make that point before, but most people here are too hard-headed to think about it.

As I said in my previous post, it depends on what the behavior of the system actually turns out to be.

If you can detect gravitational waves from anything orbiting a black hole inside the event horizon, then you can calculate the mass of both the black hole and the object trapped inside the EH (it doesn't matter if the second object is another black hole or not really). This would indicate that the EH itself has deformed from a perfect sphere, which would be an information paradox, and break the whole speed of light/time travel thing.

Therefore, I don't think it's possible for two black holes to remain seperate objects once they cross event horizons. They should collapse instantly.
ubavontuba
1.4 / 5 (11) Oct 25, 2013
If you can detect gravitational waves from anything orbiting a black hole inside the event horizon, then you can calculate the mass of both the black hole and the object trapped inside the EH (it doesn't matter if the second object is another black hole or not really). This would indicate that the EH itself has deformed from a perfect sphere, which would be an information paradox, and break the whole speed of light/time travel thing.
My point, exactly.

Therefore, I don't think it's possible for two black holes to remain seperate objects once they cross event horizons. They should collapse instantly.
I would agree, except this collapse would then have to transcend the speed of light too.

I therefore suggest black hole mergers are impossible, relative to an outside observer.

ubavontuba
1.4 / 5 (11) Oct 25, 2013
I would like to add another suggestion: I suggest (relative to an outside observer) they would actually smear around each other in a vortex, which can eventually collapse.

But could an outside observer ever perceive the collapse ...?

Fleetfoot
3.8 / 5 (5) Oct 25, 2013
There is a lot of speculation about mergers in the last few posts. It may be useful to have a look at what is actually predicted, there are various simulations here:

http://www.black-...re2.html

Several show the gravitational waves produced at the bottom of the simulation as well and you can see how they are almost entirely generated in the period prior to the merger. The seventh and eight videos freeze when the merger starts and it is clear how close to the end this happens in the waveform at the bottom.

A detailed merger of two horizons is also shown in the last video. The decay of the initial distortion to a perfect ellipsoid results in the emission of the last few wave cycles but the amplitude is far lower than those prior to the merger.
ubavontuba
1.4 / 5 (11) Oct 26, 2013
look at what is actually predicted, there are various simulations here:
Pretty computer simulations, but it appears they fail on many levels. ...mostly having to do with that whole information/causality issue.

Fleetfoot
2.7 / 5 (3) Oct 26, 2013
look at what is actually predicted, there are various simulations here:
Pretty computer simulations, but it appears they fail on many levels. ...mostly having to do with that whole information/causality issue.


As you can see, the waves are mostly produced when the objects are far apart. They originate in the region between and around the black holes so they don't fail on any level, there is no failure of causality.
ubavontuba
1 / 5 (10) Oct 27, 2013
As you can see, the waves are mostly produced when the objects are far apart. They originate in the region between and around the black holes so they don't fail on any level, there is no failure of causality.
According to the article, sure there is. The whole concept, from an external observer's point of view, fails.

From the article:
"When the waves roll through an area of space-time, they temporarily swell or shrink the distances between objects in that region, altering the arrival time of the pulses on Earth."

...I would suggest: It appears relativistic effects are poorly considered, as the measure of time is similarly swollen and shrunk, therefore generally canceling out any observable effect.

Fleetfoot
5 / 5 (1) Oct 27, 2013
From the article:
"When the waves roll through an area of space-time, they temporarily swell or shrink the distances between objects in that region, altering the arrival time of the pulses on Earth."


That is correct, the waves are quadrupole, transverse spatial waves. There's an animation here:

https://en.wikipe...nal_wave

...I would suggest: It appears relativistic effects are poorly considered,


The calculation is purely relativistic and complete.

as the measure of time is similarly swollen and shrunk,


Incorrect, there is no component on the time axis.
ubavontuba
1 / 5 (10) Oct 27, 2013
Incorrect, there is no component on the time axis.
You do know it's called space-TIME, don't you?

Fleetfoot
3.7 / 5 (3) Oct 27, 2013
Incorrect, there is no component on the time axis.
You do know it's called space-TIME, don't you?


To be pedantic, it's called "spacetime" without the hyphen but that's beside the point.

Hertzian waves in EM have no longitudinal component, gravitational waves have no time component.

The problem is that you are trying to guess how they work but just as EM waves have to be a solution to Maxwell's Equations, gravitational waves have to be a solution to the field equations of GR.
ubavontuba
1 / 5 (10) Oct 28, 2013
Incorrect, there is no component on the time axis.
You do know it's called space-TIME, don't you?


To be pedantic, it's called "spacetime" without the hyphen but that's beside the point.

Hertzian waves in EM have no longitudinal component, gravitational waves have no time component.

The problem is that you are trying to guess how they work but just as EM waves have to be a solution to Maxwell's Equations, gravitational waves have to be a solution to the field equations of GR.
In GR, gravity is not a field. It's topology.

GSwift7
2.3 / 5 (3) Oct 28, 2013
Hertzian waves in EM have no longitudinal component, gravitational waves have no time component


That depends on how you solve the problem. For gravity, time and distance are equivalent (since gravity propogates at the speed of light in a vacuum, regardless of the medium). You can use that to cancel out the terms for either time or distance by converting one to the other (oversimplification alert). This is a math trick though, so to say that there isn't actually a time component is a matter of interpretation. You could just as easily say that there isn't a distance component, and keep the time component in stead. A gravity wave passing through clocks sensitive enough to detect it should cause a time distortion proportional to the distance distortion. You could test for either, and I believe the current tests actually do kinda test both at the same time (no pun intended), depending on how you look at it.
GSwift7
2.3 / 5 (3) Oct 28, 2013
I don't understand the meaning of "time component".


That started off like such a reasonable comment, and I was actually thinking about a response.

But in reality (at the water surface in the same way


Oooops! Then we went there, and I realized I was being AWT'd
Fleetfoot
5 / 5 (1) Oct 28, 2013
gravitational waves have no time component
I don't understand the meaning of "time component". The absence of "time component" would just mean, that the gravitational waves have no periodic component ...


Think of a gravitational wave with a period of one hour. As it passed, if there was a time component, your clocks would tick a fraction earlier than expected for 30 minutes and later for the next 30. The absence of a time part just means they tick at a uniform rate as it passes.

But IMO it would be more logical to say, that the gravitational waves shouldn't have the transverse component, because "transverse" is the just dual term to "longitudinal", not "time".


You could equally say they can't have a longitudinal component if they are transverse and that is the case. If a simple gravitational wave is moving in the x direction, objects get stretched in the y direction and compressed in the z direction in one half of the cycle and the opposite in the next half.
TheGhostofOtto1923
1 / 5 (3) Oct 28, 2013
That started off like such a reasonable comment
-Reasonable, you mean like this?
gravity propogates at the speed of light in a vacuum, regardless of the medium
Well if its traveling through a vacuum then vacuum is the medium yes? Its speed will be slower when traveling through other media.
DarkHorse66
2.3 / 5 (3) Oct 29, 2013
1.
Anyone know how fast G waves move?
FF
They have no mass so they travel at c (the speed of light).

2.
That started off like such a reasonable comment
-Reasonable, you mean like this?
gravity propogates at the speed of light in a vacuum, regardless of the medium
Well if its traveling through a vacuum then vacuum is the medium yes? Its speed will be slower when traveling through other media.
GoO
I will post a number of links to help explain my answers, so pls read them first, before assuming..I spent alot of time hunting for the right ones. Perhaps others might want to read up on them too, for other answers.With all due respect to FF, he is correct inasmuch that it is the speed of c, but it is not because they have no mass. No force has mass. With all due respect to Otto, a grav wave DOES travel at the same speed in all media. As will be seen by the quote that I give from my first link, the answer to both is the same,...cont
DarkHorse66
2 / 5 (4) Oct 29, 2013
cont...it has to do with the nature of the medium itself. From the first link:
http://www.learne...secNum=7

"What are the similarities and differences between electromagnetic and gravitational waves? Both waves travel at speed c and carry with them energy and momentum. For electromagnetic waves, spacetime is the background medium in which the waves travel, while for gravitational waves, spacetime itself constitutes the waves. Electromagnetic waves are produced by accelerating or oscillating electric charges, while gravitational waves are produced by accelerating or oscillating mass distributions."

Some other links:
http://en.wikiped..._gravity
http://en.wikiped...nal_wave
http://scienceblo...gravity/

...cont

DarkHorse66
2 / 5 (4) Oct 29, 2013
...cont
For the more knowledgeable:
http://math.ucr.e...eed.html
http://math.ucr.e...ion.html

And lastly, my new favourite (I've even bookmarked this one for myself, as well as the first link):
http://www.speed-...able.htm
That one even has some quite interesting links for further discussion and/or thought
I hope that there is something for most people here, it was certainly fun for myself, to learn more about the nature of gravitational waves.
Best Regards to all, DH66
GSwift7
5 / 5 (1) Oct 29, 2013
With all due respect to Otto, a grav wave DOES travel at the same speed in all media


Thanks for the references DarkHorse. I honestly didn't think anyone would dispute the fact that gravity must propogate at C, no matter what the environment. Otto has been trolling extra hard lately, and just contradicting random stuff to get people to interact with him. I wouldn't bother trying to be reasonable with him, since I think he is just trying to see how much time you'll waste on his nonsense.
GSwift7
3 / 5 (2) Oct 29, 2013
In general, the gravitational wave could spread in the way, it would affect all dimensions of objects at the same moment.


The effect of a gravitational wave would be exactly like tides. You would see a difference in the pull of gravity from point A to point B. That has a well-known effect on objects, since we see this happen here on Earth every day. There's nothing mysterious about the effect of a gravity wave, it's just hellishly difficult to detect, precisely due to the fact that our own tidal forces are so much stronger by comparison. It's like trying to measure the wind of a passing butterfly in the middle of a hurricane.
Fleetfoot
5 / 5 (1) Oct 29, 2013
Excellent references DarkHorse. I particularly like this one, I feel the animations make the patterns clear.

http://www.einste...gw_waves

If a simple gravitational wave is moving in the x direction, objects get stretched in the y direction and compressed in the z direction


I know about it, but the crosspolarized gravitational waves are special example. In general, the gravitational wave could spread in the way, it would affect all dimensions of objects at the same moment.

Single waves can't do that, (there is no longitudinal motion, see the page above) but of course passing though any region there may be waves from different sources moving in different directions which would combine to produce a complex mix.
Fleetfoot
5 / 5 (2) Oct 29, 2013
They have no mass so they travel at c (the speed of light)
Both halves of this implications are wrong from AWT perspective. The gravitational waves radiate mass of binary pulsar into outside, so they must have mass.


Individual photons can remove mass from a source but have no mass themselves, your assumption is flawed.

And they're spreading with superluminal speed, ...


It's a shame you've gone back to posting mindless garbage, you seemed to be holding it together for a couple of posts there.
Fleetfoot
5 / 5 (2) Oct 29, 2013
Individual photons can remove mass from a source but have no mass themselves
This is a logical contradiction, don't you think?


No, it is rather obvious really. Mass is the difference between energy and momentum (well the squares to be exact) and for a photon the energy is equal to the momentum so the mass is zero.

m^2 = E^2 - |p|^2

Consider the sum of two identical photons moving in opposite directions however. The momenta are equal and opposite so the sum is zero. The energies are scalar so simply add, hence a system of two photons does have mass.

If you don't spend a little time learning these basic definitions, you're never going to understand the more complex stuff, and spouting silly technobabble only makes your lack of understanding more obvious.
TheGhostofOtto1923
2.3 / 5 (6) Oct 29, 2013
With all due respect to Otto, a grav wave DOES travel at the same speed in all media


Thanks for the references DarkHorse. I honestly didn't think anyone would dispute the fact that gravity must propogate at C, no matter what the environment. Otto has been trolling extra hard lately, and just contradicting random stuff to get people to interact with him. I wouldn't bother trying to be reasonable with him, since I think he is just trying to see how much time you'll waste on his nonsense.
No I admit I misread that, thinking you were talking about light. But I rarely post nonsense, especially when I get to expose the nonsense of others by simply doing a little research. Yes or what?

By the way the speed of gravity waves has not been determined conclusively as they haven't yet been measured directly. But this should happen within months. Look it up.
DarkHorse66
5 / 5 (1) Oct 30, 2013
Hi Guys
Glad that you liked the material that I found. At least it seems to have put everyone more on the same page wrt to what knowledge they were relying on. The only person who seemed to have an issue with it, was Teech, who promptly trolled me with 'ones'. Maybe he decided that what I was posting was not AWT-friendly/compatible enough for his tastes. Marking down somebody for NOT espousing a crackpot theory, well that is a new one on me.

@GoO
Not sure why you were trolled with a 'one' for your last comment (by open). You were openly acknowledging that you had misinterpreted something and were letting the other person know, and that seemed perfectly reasonable to me. Nor was your wording lacking in respect or decency. That is why I (equally openly) gave you a 'five'. I'm a believer in acknowledging, where acknowledgement is due. And yes, I too am interested to see what those experiments might yield. No doubt Phys.org will bring the article to us then.

Best Regards to all, DH66
GSwift7
5 / 5 (1) Oct 30, 2013
By the way the speed of gravity waves has not been determined conclusively as they haven't yet been measured directly. But this should happen within months. Look it up


Well, I wouldn't be so sure that anyone will get confirmed results in that short a time. I know it hasn't been proven, but the implications of what it would mean if gravity waves don't propogate at C all the time would be mind-blowing. When we are eventually able to measure their speed, I don't think anyone will be surprised if it is C. That's all I meant when I said that I was surprised anyone would question it.

I'll agree with DarkHorse that you have been reasonable in this thread. If I gave ratings, I wouldn't have down-voted any of your comments in this thread. Personally, I don't see why anyone bothers with the stars though. I check out my comment history to look for 1's sometimes, because most people will post the reason for objecting after giving a 1, and I like to respond to those when they're reasonable