ИСТИНА

For modern high precision measurements any source of noise can be critical. The gravitation wave detection project LIGO have to account many fundamental sources of fluctuations. The Brownian noise coming from chaotic thermal motion of particles is one of the enemies. The Fluctuation-Dissipation theorem states that each source of dissipation yields corresponding fluctuations. The mirror substrates and suspensions in LIGO are made of silica glass -- amorphous substance that couldn't become a crystal due to high viscosity. Having very high viscosity (ranged from $10^{17}$ to $10^{40}$ in literature) it can be the source of additional noise, and influence performance of LIGO. We re-estimate viscosity value from recent experimental data and present a method to estimate corresponding noise similar to.