Gravity Waves in the News

http://www.space.com/25088-gravitational-waves.html

This is great news. Well a 10% to 15% chance for this to be great news.

IMHO Detecting these waves is the critical step needed in proving the theory that gravity propagates at the speed of light in a vacuum. I wonder if this discovery will help or compound the dark matter problem?

Yes, it would be great news. How would it possibly confound dark matter theory?

Well the dark matter problem exists because the observed quantity of light matter produces insufficient gravity to keep large bodies together across large distances as observed from even farther distances. Gravity waves implies a finite velocity to the change in this attraction field. Could this mean more or less gravitational attraction happens over these distances? Maybe a standing wave effect happens that leads to more attraction without a need for vastly more matter to exist?

Maybe we should wait for a better than a 15% reliability in detection before grasping for any other straws?

"Gravity waves implies a finite velocity to the change in this attraction field. Could this mean more or less gravitational attraction happens over these distances?"

No. Firstly, gravitational waves do not change the average gravity - it's a tiny oscillation. Secondly, the energy in them over larger distances is extremely feeble - that's why it's so difficult to detect them directly.

BTW, the term "Gravity Wave" is a bit of a misnomer here, although it would have been the ideal word for the phenomenon. Unfortunately, it has been taken for atmospheric gravity waves long before Einstein's time. Hence we are stuck with the more cumbersome "gravitational waves" for ripples in the gravitational field.

Oh, I know that this is a very tiny oscillation in the average gravitational field strength and that this average field strength gets attenuated through space. What I was wondering is if detection of this variation, at all, might imply the gravitational field strength does not asymptotically approach zero with distance but some tiny non-zero magnitude.

My speculation is very premature to say the least. This detection has yet to be confirmed.

Jorrie-"Gravity per se does not exactly propagate - it is a field and only changes in that field propagate at c. AFAIK, gravity played no significant role in "standard" cosmic inflation, if such an effect indeed happened. I think we do not quite understand what happened there - never mind how and why it happened".

Gravitational field does not stop, but the effects of the field attenuate far from mass, and drastically increase near mass.

If gravity can only propagate at the speed of light (en vacuo), then how does one exactly explain cosmic inflation? Maybe gravitational waves can better understood in the future, and some means of producing energy/propulsion as a result??

"If gravity can only propagate at the speed of light (en vacuo), then how does one exactly explain cosmic inflation? "

Gravity per se does not exactly propagate - it is a field and only changes in that field propagate at c. AFAIK, gravity played no significant role in "standard" cosmic inflation, if such an effect indeed happened. I think we do not quite understand what happened there - never mind how and why it happened.

Today we think that if the standard picture is close to the truth, gravitational waves must have been generated during inflation. We can never hope to directly detect those waves, but we may be able to 'see' them in the CMB radiation.

Some bounce cosmology theories sidestep inflation and do not produce primordial gravitational waves. So if we detect such waves, it may rule out a certain class of bounce theories.

Thanks Jorrie, Happy New Year to you sir!

There is very good indirect evidence of gravitational radiation in binary pulsar systems.

http://www.astro.cardiff.ac.uk/research/gravity/tutorial/?page=3thehulsetaylor

The figure (from Weisberg and Taylor (2004)) shows the cumulative shift of periastron time for PSR 1913+16. This shows the decrease of the orbital period as the two stars spiral together. Although the measured shift is only 40 seconds over 30 years, it has been very accurately measured and agrees precisely with the predictions from Einstein's theory of General Relativity. The observation is regarded as indirect proof of the existence of gravitational waves. Indeed, the Hulse-Tayor pulsar is deemed so significant that in 1993 its discoverers were awarded the Nobel prize for their work.

It would be good news if there is direct evidence.