I would imagine so, that part confused me as well. It's possible that the level sensitivity required is just too extreme, and would be subject to too much loca

I would imagine so, that part confused me as well. It's possible that the level sensitivity required is just too extreme, and would be subject to too much local interference. There's one such test [1] that I find interesting that suffers from similar problems. It tries to detect gravitational waves traveling through the universe by pointing a laser at a mirror at the end of a 4km tunnel and measuring any changes in the total distance. [1] http://en.wikipedia.org/wiki/LIGO http://en.wikipedia.org/wiki/LIGO