Floating mirrors

We discuss a new technology that promises large, inexpensive mirrors. We argue that it should be possible to tilt a rotating viscous liquid by perhaps as much as a few tens of degrees. The tilted liquid parabolic surface is used as the support for a thin reflecting metallic film. It may also be possible to use it to support an ultrathin glass mirror. We demonstrate two critical steps: that a viscous liquid mirror can be tilted and that an optical-quality metallic film can be deposited on a liquid. The advent of astronomically useful tilted floating-mirror telescopes is contingent on the development of high-viscosity, high-reflectivity liquids. It is a good omen that we already have identified two classes of such liquids; however, there remain technical challenges to overcome before such liquids can be used in viable telescopes.