eldavojohn writes "Want to make a great concave mirror for your
telescope? Put a drop of mercury in a bowl and spin the bowl.
The mercury will spread out to a concave reflective surface
smoother than anything we can make with plain old glass right
now. The key problem in this situation is that the bowl will
always have to point straight up. MIT's Technology Review is
analyzing a team's success in combating problems with bringing
liquid mirrors into the practical applications of astronomy. To
fight the gravity requirement, the team used a ferromagnetic
liquid coated with a metal-like film and very strong magnetic
fields to distort the surface of that liquid as they needed. But
this introduces new non-linear problems of control when trying
to sync up several of these mirrors similar to how traditional
glass telescopes use multiple hexagonal mirrors mounted on
actuators. The team has fought past so many of these problems
plaguing liquid mirrors that they produced a proof of concept
liquid mirror just five centim