Will Future Astronomers Observe with Liquid Mirrors?

Experiments with liquid‐mirror prototypes go back at least to the early 1800s. Isaac Newton, who invented the reflecting telescope and certainly thought about spinning liquids, may be the originator of the concept. In 1908 Robert Wood (Johns Hopkins University) made a 0.5‐m liquid‐mirror telescope. Vulnerable to jarring motions, Wood's mirror could detect “the footsteps of a person running 50 yards from the telescope house.” The problems were serious: Variable motor speed caused distorting ripples on the fluid surface and such a transit telescope is unable to point in any direction other than the zenith, that is, straight up. Hence a liquid‐mirror telescope would seem impractical.