[syhprum]

Is there a polarization component to gravitational waves ?
The LIGO installations consist of two horizontal tubes at right angles would a third vertical tube albeit expensive to construct provide useful information ?.   

[evan_au]

Is there a polarization component to gravitational waves ?

Yes. That is why researchers want at least 4 gravitational wave observatories around the world: 2 in USA, with 1 in Japan and 1 in India being built.

If the polarization is "wrong", one observatory may not be able to pick up the signal at all (or it might be so low that it is buried in noise).

However, the other 3 observatories, with different orientations on the surface of the Earth should (in principle) be able to pick up the signal (if it is strong enough).

Astronomers want the same signal to be picked up by 3 observatories, as this allows them to triangulate the position of the source in the sky - at least for a neutron star merger, that should produce a signal that can be picked up by optical, X-Ray and radio telescopes.

With the first signal back in September 2015, it was detected at just 2 observatories; the signal could have come from anywhere in a thin band that circles half way around the sky. That doesn't tell you where to point your telescopes (not that you would expect to see much from a merger of black holes).

The LIGO installations consist of two horizontal tubes at right angles would a third vertical tube albeit expensive to construct provide useful information?

Yes, but it's easier to build another two 4km vacuum tubes flat on the ground in another part of the world, than to build a 4km vacuum tube up in the air, or down into the ground.

Geographical dispersion also provides some protection from sources of interference like earthquakes, cosmic rays, power glitches, hardware failures, software bugs, etc.

[syhprum]

Yes with tightly time controlled communication now available another installation 90° around the world is a better solution than a vertical tube.
As you say if a source could be observed by both electromagnetic radiation as well as gravitational waves by the variation in timing it would give some clues as to the mass of the Graviton (if it has any!) or confirmation of the mass of Neutrinos if they are also observed at the same time

[jeffreyH (OP)]

If life had evolved in a zero gravity environment then lots of things would be different. How would Lavoisier have determined the conservation of mass without gravity? How would mass even be determined. Any experiments that can attempt to pin down the speed of gravity will open many new avenues in physics. Will string theory survive?

[dhjdhj]

I also wondered about the speed of the wave and whether if new matter was created which included a graviton( if it exists ) its field would presumably extend to infinity, but would it do that instantly? or would it have a finite speed related to C?

[evan_au]

I also wondered about the speed of the (gravitational) wave

This is covered in another thread: http://www.thenakedscientists.com/forum/index.php?topic=65812.0

[evan_au]

The LIGO installations consist of two horizontal tubes at right angles would a third vertical tube albeit expensive to construct provide useful information?

A European proposal suggests:

three 10-kilometer arms arranged in the shape of an equilateral triangle rather than an L. That configuration would help it pinpoint the sources of gravitational waves on the sky

Looking at it geometrically:
- three tubes at right-angles would represent a corner of a 3D cube, with sensitivity in all three planes of the cube surface.
- three tubes in an equilateral  triangle represents a cut-off corner of a 3D cube. They imply that this gives enough information to determine the direction of the source from a single detector?

eLISA (in space) would also be a triangle, but with sides of a million km.

Unfortunately, neither detector is currently funded.
See: http://www.scientificamerican.com/article/the-future-of-gravitational-wave-astronomy/