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LIGO is designed to detect changes in length on the order of 10,000ths the scale of a proton. I know they are extremely well isolated from their surroundings, but how could we even approach isolation at such a scale? Wouldn't even the vibration of the molecules making up the system be picked up by the sensor?

Qmechanic
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jonahs
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    This is the sort of question that deserves a good answer, but it will be difficult, given that LIGO has spent the past several decades doing almost nothing except incredible feats of engineering to accomplish this one task. –  Feb 13 '16 at 01:02
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    Knock yourself out: https://dcc.ligo.org/cgi-bin/DocDB/ListBy?topicid=23 and https://dcc.ligo.org/cgi-bin/DocDB/ListBy?topicid=8... what the heck... just read all of it: https://dcc.ligo.org/cgi-bin/DocDB/ListTopics. :-) – CuriousOne Feb 13 '16 at 01:35
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    Also not a duplicate -- thermal vibrations and seismic disturbances are unrelated, and dealt with entirely differently. –  Feb 18 '16 at 01:06
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    The vibrations of molecules are averaged out because of the laser beam's spatial extent. Also, very important to note, we are always looking at noise spectral densities, that is we are in frequency space! LIGO can detected changes of the mentioned magnitude - but only in a certain frequency band around 100 Hz. It is not very sensitive regarding absolute changes (i.e. at 0 Hz) or very fast changes, as in these frequency regions the remaining noise is higher (see spectrum in above-linked question). – dodi Jul 14 '17 at 15:12

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