Stabilising mirrors
Turbulence in the atmosphere is a major problem with Earth-based telescopes. Most modern telescopes take care of this by using adaptive optics, a corrective process in which parts of the telescope mirror are mechanically flexed. This is done by a complex motor system in an amount typically equal to a fraction of the wavelength of the incoming light. Some instruments need very still mirrors to observe the flexing of space-time on a scale much smaller than the size of an atom. Now, physicists in Paris have found a way to measure the thermal agitation of mirrors and reduce this unwanted noise by a factor of 20 with pressure from laser light.