Another gravity wave question

[jnorman]

i have read quite a bit about gravity waves, and even worked (as a lab tech) on an early GW experiment at LSU back in the 70s. i have become ever more convinced that the search for GWs is relatively fruitless.

the reason i feel that way is that, given any particular example of an event which would cause GWs, such as exploding star or orbiting binary neutron stars, the center of gravity will not be changed, and local GWs will be smoothed out in very short distance (astronomically speaking).

for any GW to be actually noticeable or measureable at any astronomical distance, the center of gravity of some very massive system would need to be altered significantly, and frankly i can't even think of a single example of how that might occur.

perhaps one of you could please enlighten me on the error of my thinking on this. thanks.

 

[bcrowell]

the reason i feel that way is that, given any particular example of an event which would cause GWs, such as exploding star or orbiting binary neutron stars, the center of gravity will not be changed, and local GWs will be smoothed out in very short distance (astronomically speaking).

It's true that the center of gravity can't change. That's why gravitational waves are quadrupole radiation, not dipole radiation.

The intensity (watts/m2) falls off as 1/r^2. It can't fall off faster than that because of conservation of energy.

This is all assuming that GR's description of gravitational waves is right. However, the extremely good agreement of the Hulse-Taylor pulsar's behavior with GR suggests that GR's description is right.

 

[Naty1]

jnorman: I hope you are wrong. here is why: There is a satellite ystem that is supposed to be able to detect subtle differences between gravitational waves emanting from a big bang that will be slightly different than those emanting from a brane collision in a cyclic universe. That would be fun if it works!

I posted details in another thread based on information from THE ENDLESS UNIVERSE by Steinhardt and Turok and all I remember is that it had to do with the polarization of such waves. Ok it's dubbed the BBO or Big Bang Observatory...and is described in the book around page 218...

I'll see if I can find the prior thread...

 

[Naty1]

Could not find it...anyway LIGO and LISA according to the above authors are not sensitive enough for the big bang, and... WMAP came up with nothing so far...but should be able to detect major collisions, like black holes, etc...