ThiruV wrote:A_Gupta wrote:
1. Like with your two ears, you can somewhat localize where a sound came from, and likewise 2 LIGO detectors can.
2. There was a 7 millisecond interval between the two detectors - the wave traveled at the speed of light, ruling out any acoustic source. The amplitudes detected at the detectors were the same. A nearby source with a 1/r fall-off in wave amplitude and obviously at different distances (0.007 light seconds worth of distance) would not produce equal amplitudes.
Suppose the amplitudes at the two detectors differ by exactly 1% with no noise; the 1/r fall-off then implies that the distance of the source has to be a 100 times the distance between the two detectors; 0.7 light seconds is approximately halfway to the moon.
The two detectors are on a curve (earth surface), and they will encounter the max amplitude of the wave some delta(t) apart, but in 3D space, solving the equations for the source of the disturbance should yield best case, a closed curve in 3D-space that contains the source of the disturbance. So how did they know which point on that curve was the actual solution, to make the claims? I can accept that the math works out for such and such configuration of black hole masses, which would result in the gravitational wave that was seen, and so they believe that to be source of this wave. The 0.4 sec delay between this event and the gamma ray seems to be unexplainable by any known theory, so there seems to be new information that does not fit existing theories. This one point makes me wonder how much of existing theories actually fit in with these recent observations. Lots of sleepless nights for physicists no doubt...
A_Gupta has explained pretty well, let me quickly add:
So how did they know which point on that curve was the actual solution, to make the claims?
- Read the paper, it is explained extremely well. (If you do not have good background in math, (as it seems to me that you do not ( no disrespect , see note #1 below), just use some one who has good math background (say a Math/physics college professor) to go over the basic part).
It is not some "guess" or "likely candidate" but they are virtually sure (sigma > 5). Trust me, there are perhaps millions of people here with good back ground in math who have seen and checked these mathematical steps, and if even a SLIGHT error or unclarity noticed they would have retracted the paper by now.
The 0.4 sec delay between this event and the gamma ray seems to be unexplainable by any known theory,
Again even a slightest discrepancy here --- if the data is not explainable or fit with the known theory -- will kill the paper. (Hint: There is ALWAYS some delay between gamma ray or any EM radiations . this is why one sees rainbows.... EM waves (as opposed to gravitational waves) gets delayed if it passes through earth's atmosphere, or water (slower still), or glass (even slower), burqua (stopped for ever)..
The delays due to neutron stars etc are pretty well calculable.
Let me just add a trivia here. Which will send madarasa mathwala in a tizzy but ask any physics professor or do your own calculations . .
Do you know how long does it take for a photon from the center of our own sun to reach us on the earth..?
The answer is about 4000 years!
(it takes about 4000 years for it to reach from the center to the surface of the sun, and about 8 minutes afterwards. Graviton (irrespective of where it started) will reach in about 8 minutes.
(So time delay between gamma ray burst and gravitational delay is normal - it depends where the photon started and medium it went through. BTW this is one of the reason the we are more excited that we will get new insight about pulsars, supernova etc..)
Point is one has to know some basic physics before one can understand the basic part and then ask the questions.
Hope it helps.
Note1 - No disrespect but the reason I doubt you do not have necessary background even in the most basic aspect is, just to show one example, your this post. (
viewtopic.php?p=1981860#p1981860 Do you now see why?
If not, see my next post for details -- if interested.
I do hope, at least for some this has been helpful.