A liquid mirror telescope is made by spinning a reflective fluid, such as mercury, at a constant rate. This rotation produces a parabolic surface, which is an ideal shape for a telescope mirror. (You can try this yourself.) While these mirrors can be built to be large and orders of magnitude cheaper than solid mirrors, they have the disadvantage that they can only look straight up. Creating mirrors this way is not new; they have a history [.ps] that dates back to Newton. However, they have recently regained attention as the technology behind proposals to build an enormous (20m+) telescope on the moon. (A less technical treatment here.)
posted on Jul 1, 2008 - View this thread

Reversible flow! In the 1960s, the National Committee for Fluid Mechanics Films produced a series of films for education in fluid mechanics. This clip is part of "Low Reynolds Number Flow"; you can find the entire collection streamed here. Interesting demonstrations abound. (1st link is QT; rest are RealPlayer.)
posted on Aug 17, 2007 - View this thread

MizPee works on your mobile phone to help you locate the nearest, cleanest bathroom.
posted on Jul 3, 2007 - View this thread

Order from chaos! Fill a cylindrical bucket with water and make it so the bottom can spin. At certain speeds, stable regular polygonal shapes will spontaneously form at the turbulent surface of the water. See the video. [2.6MB avi] [via last week's PRL]
posted on May 10, 2006 - View this thread

This cornstarch, it vibrates. (wmv 4MB)
posted on May 19, 2004 - View this thread