[ExI] Gravity wave math

[John Clark]

One thing I found mind boggling about the October 12 2015
​event​
 is that in a fraction of a second a amount of matter equivalent to 3
​suns​
 was converted entirely into energy, in this case into gravitational waves
​. By comparison the Hiroshima bomb converted less than the mass of a dime
into energy. ​A
nd yet spacetime is so stiff
​and it's so hard to deform that if you were in orbit around the Black Hole
collision site at the same distance the Earth is from the sun the
gravitational
waves would make your ears pop but that's about it. So how could LIGO
detect those waves from a distance of a billion light years? One reason is
that LIGO is so sensitive it can tell when the distance between 2 mirrors 4
kilometers apart changes by 1/10000 the width of a proton, the other reason
is LIGO detects the displacement the gravitational waves produce not their
energy as telescopes do with light, so the strength of the signal LIGO
detects decreases linearly with distance not as distance squared as with
electromagnetic detection. That means it can hear things far far away.

John K Clark   ​


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