Gravity Waves: Energy Transfer from Observation

[NC_Seattle]

I'd be interested in hearing some thoughts on this.

Does the fact that a set of gravity waves were observed imply that some energy, presumably a very small amount, was transferred from the gravity wave to observing instruments? If so, where in the apparatus and how did this transfer occur?

 

[jerromyjon]

If so, where in the apparatus and how did this transfer occur?

The gravity waves simply pass through matter similar to how sound passes through matter. As the waves passed over the interferometer arms it changed the length ever so slightly but enough to be measured then they returned to their normal length. I don't think gravity waves "change" matter or "change" back into matter, they just dissipating energy.

 

[bcrowell]

Does the fact that a set of gravity waves were observed imply that some energy, presumably a very small amount, was transferred from the gravity wave to observing instruments? If so, where in the apparatus and how did this transfer occur?

Yes, the waves caused the arms of the interferometers to oscillate in length. Those oscillations had kinetic and potential energy.

Historically, there was a lot of confusion on this point. Feynman came up with an argument called the sticky bead argument to demonstrate that gravitational waves would carry energy and could donate energy to an antenna: https://en.wikipedia.org/wiki/Sticky_bead_argument

 

[jerromyjon]

https://en.wikipedia.org/wiki/Sticky_bead_argument

Thanks, a very good point!

 

[PeterDonis]

Feynman came up with an argument called the sticky bead argument

As an amusing historical note, Feynman apparently came up with this out of frustration with other scientists at the Chapel Hill conference, who he felt were stuck in abstract math instead of looking at the physics, and as a result were confusing themselves unnecessarily. In a letter he wrote from the conference (to his wife Gweneth, IIRC--I read about this in the foreword to the Feynman Lectures on Gravitation), he said something like "This is what comes of looking for conserved tensors, etc., instead of asking: can the waves do work?"