Millions of Problems:

Ground jiggling.

Louisiana-- Careful site selection for low noise.

Interferometer built, and logging company moved in and logged the

trees around the interferometer (they owned the land).

Trucks on highways, wind storms, hail,....

Waves on ocean breaking on land 300km away causes enough jiggling

to destroy sensitivity.

Light interacts as photons.-- shot noise in detection and in pressure

on mirrors—tradeoff. (Increase power to decrease detection shot noise

increases shot noise on mirrors. -- ultimate limit.)

Increase power to reduce shot noise. (Heating of mirros?)

Make mirrors heavier to reduce pressure noise.

Measurement Noise

Light scattering

Vacuum-- less than a billionth of atmospheric.