Re:LIGO's vibration isolation system
by andrepd on Thursday February 11, 2016 @10:22PM
(#11085093)
10 to the minus 19! It's mind boggling. Semiconductor process nodes constantly boggle my mind, and yet they sit at a cool 10 to the minus 9. These vibrations are smaller relative to a CPU transistor than a CPU transistor is to me.
[ Parent
| on HN ]
LIGO scientist here. The way this is presented can be a little deceptive - the isolation is very frequency dependent. At high frequencies (>10Hz), the pendulums and blade springs in the suspension isolate the mirrors very well, so they are moving by only these small amplitudes (10^-19 meters). But at low frequencies (<1Hz) the isolation ratio is essentially 1, so the amplitude of the mirror motion is roughly the same as that of the ground (about 10^-6 meters).
Yes, which makes sense physically. If the earth's rotation slowed by a constant velocity, in order to damp that motion the mirrors would have to displace themselves in the opposite velocity. Of course, there's no room for them to do so, so damping such low frequencies is not possible.