- #141
Islam Hassan
- 226
- 4
Is this equivalent to the annihilation of three solar masses worth of matter in an instant? Was such energy release predicted by present models of BH merger/collision or is this a new phenomenon?
IH
We'll know more in a week.
A loss of three solar masses in the merger would correspond to a power above 1046 W (probably much higher), the most powerful event we ever saw.
The combined luminosity of all stars in the observable universe is about 1049 W.
Yes.Is this equivalent to the annihilation of three solar masses worth of matter in an instant?
It was predicted. Without these enormous energies, the signal wouldn't be strong enough for LIGO to see, and we would never have built it.Was such energy release predicted by present models of BH merger/collision or is this a new phenomenon?
Where does the spin 2 prediction come from?All under the assumption that gravitons exist ...
I've been lurking on the thread about this fascinating announcement but this question got me to wondering. Can gravity waves be theoretically affected by gravitational lensing? My guess would be that they are but I don't know the details enough to know.What happens with gravitational waves? Do they exist forever or can they be absorbed or transformed?
Matter (dark or not) between us and a GW source is invisible to the GW.
Is this equivalent to the annihilation of three solar masses worth of matter in an instant?
This depends on what you mean by "annihilation".
Three solar masses worth of energy were converted to the energy of gravitational waves, which are "invisible" (they interact very weakly).
The "annihilation" as in matter-antimatter reaction would generate electromagnetic radiation (gamma rays), not gravitational radiation.
His statement is not about the gravitational lensing. It is about how the GW would interact with matter and dark matter.I've been lurking on the thread about this fascinating announcement but this question got me to wondering. Can gravity waves be theoretically affected by gravitational lensing? My guess would be that they are but I don't know the details enough to know.
Edit: It seems that I'm wrong.
Right. I have no knowledge of an analysis of lensing for GW; it is a great question. A purely heuristic argument to expect it is that if GW travel at c, and can be treated similar to the EM geometric optics approximation of treating a piece of the wave front as having a world line, then that world line ought to be a null geodesic. Then, the lensing would be basically the same as light. But this is just a general argument - I would not be very confident in it without more analysis or information.His statement is not about the gravitational lensing. It is about how the GW would interact with matter and dark matter.
I agree with this. It is my naive expectation as well. Do the math on a Minkowski metric background and the perturbation satisfies the wave equation in flat space. It is a reasonable expectation that doing the perturbation in a curved background you might end up with the wave equation in the curved space. Then again, I have not done the math either.Right. I have no knowledge of an analysis of lensing for GW; it is a great question. A purely heuristic argument to expect it is that if GW travel at c, and can be treated similar to the EM geometric optics approximation of treating a piece of the wave front as having a world line, then then world line ought to be a null geodesic. Then, the lensing would be basically the same as light. But this is just a general argument - I would not be very confident in it without more analysis or information.
Ah, I see the difference. Gravity waves would not be blocked but they still might be lensed. Thanks for your responses.His statement is not about the gravitational lensing. It is about how the GW would interact with matter and dark matter.
Ah, I see the difference. Gravity waves would not be blocked but they still might be lensed. Thanks for your responses.
And indeed, they've already thought of that, and the answer is yes. The references in this paper list similar work as well:I agree with this. It is my naive expectation as well. Do the math on a Minkowski metric background and the perturbation satisfies the wave equation in flat space. It is a reasonable expectation that doing the perturbation in a curved background you might end up with the wave equation in the curved space. Then again, I have not done the math either.
At the moment, I can't think of any analog. Certainly not EM - a charge does not deflect light.So Gravity is able to act like a waveguide for its own waves? Is there any other precedent or analogy for this in nature?
Well, any time you have path bending you can model it as speed slow down, but, in GR, this is considered a coordinated dependent feature (as are all speeds in GR). What makes the EM case invariant is the ability to compare light through a medium to light through a vacuum on 'nearly the same path'. As with the twin scenario versus coordinate dependent time dilation, the ability to do this comparison is what gives you an invariant effect.Is the speed of gravitational waves a constant?
I mean is there anything analogous to a refractive index that can slow them down, or is their speed truly absolute?
This question came up in a recent meal with my students where I was joking that me trying to hula hoop might be detected by the Livingston facility.
Not just from now on. Luckily we already have a theory that can handle this: General Relativity.I agree that Newton's formula doesn´t have included this principle. But is it plausible to speculate that our calculations with gravity must deal, from now on, with retarded potentials or similar resources ?
3 solar masses within ~0.2 seconds, with an estimated peak power of 3.6*1049 W, more power than the luminosity of all stars in the observable universe combined.Is this equivalent to the annihilation of three solar masses worth of matter in an instant? Was such energy release predicted by present models of BH merger/collision or is this a new phenomenon?
Right, forgot about that part.So, while a single measurement is not very constraining, it shows that the speed of gravitational radiation is of the same order as the speed of light.
GEO600 wouldn't be sensitive enough for a clear detection, and I doubt it would have seen it at all.This nature article mentions that other interferometers such as Geo600 in Germany and Virgo in Italy were not operating at the time . Is it known whether Geo600 would have detected the gravitational waves?
What happens with gravitational waves? Do they exist forever or can they be absorbed or transformed?
That is one of the questions LIGO tries to anwer. We'll have to wait until more data is available.How often such apparatus will be able to confirm these measurements?
How often such experimental conditions are fullfilled in nature?
How did the scientists conclude that the source was the collision of two black holes?
An EM field can deflect an EM wave -- an extremely weak QED phenomenon known as Delbruck scattering.At the moment, I can't think of any analog. Certainly not EM - a charge does not deflect light.
By the pattern of the detected waves. Scientists have done detailed numerical simulations of the gravitational wave patterns we should expect from various events. The pattern detected by LIGO from this event matched the pattern the simulations gave for a black hole collision. The patterns for other types of events are different.
Very interesting. I was, of course, thinking classically, but anyway wasn't familiar with this.An EM field can deflect an EM wave -- an extremely weak QED phenomenon known as Delbruck scattering.
Considering that G waves transport energy, or else LIGOS wouldn't work, they must transfer some of that energy to the objects that they move. however, this question is important from the perspective of possible quantum gravity theories. If gravity is quantized and if gravitons exist then they will not transfer their energy in a continuum but in quanta. This is a whole new area of research enabled by this discovery.This nature article mentions that other interferometers such as Geo600 in Germany and Virgo in Italy were not operating at the time . Is it known whether Geo600 would have detected the gravitational waves?
What happens with gravitational waves? Do they exist forever or can they be absorbed or transformed?
If gravity is quantized and if gravitons exist then they will not transfer their energy in a continuum but in quanta. This is a whole new area of research enabled by this discovery.
Not just from now on. Luckily we already have a theory that can handle this: General Relativity.
concerning GR, does it have a well defined prediction for the GW's velocity?