I highly recommend a physics/astronomy project to any school that wants to give its students a fascinating challenge…and to bring the school itself some newsworthy bragging rights. How would you like your school to have perhaps the biggest telescope in its area…built very easily by students and teachers…out of water (or some other fluid)?
Back in the early ’60s, my younger brother Byron (who was around 10 at the time) came to me with a sheet of equations. He said he had proved that if you centered a container of water on a record player turntable and set it rotating, when all of the water reached the same speed, its surface would form a perfect parabola…in balance between gravity and centrifugal force. And if you upped the turntable’s speed from 33.3 RPM to 45 and 78, you’d in effect have a “zoom” telescope!
So we built it. And it worked wonderfully. We first tested it in our bedroom, with a bare light bulb attached to a vertical rod beside the turntable. From Byron’s equations, we computed where the water’s “focal point” would be at 33.3 RPM, set the bulb at that height above the water, lit it up, and started the turntable. A blurry bright area appeared on the ceiling, and at the instant when all water had reached the same speed, a sharp image of the bulb snapped into view.
We then lowered the bulb to the telescope’s computed focal length at 45 RPM, upped the turntable’s speed, and a bigger glowing blob swirled again on the ceiling. And when all of the water reached 45 RPM, a bigger image of the bulb snapped into view. Same with 78 RPM.
We took our new 12-inch Water Telescope out into the back yard one night, and quickly noticed its one drawback. It could only point straight up. If you tried to tilt it, the water would lose its parabolic surface. But a couple big, movable, parallel mirrors were all we needed to divert most of the stars’ and planets’ light down toward the spinning water.
Water worked OK, but we discovered that painting the inside of its container black boosted the image’s contrast. And you know what worked best of all? Black molasses…LOTS of it. Its viscosity also damped out small vibrations from the turntable motor.
Byron was a true pioneer. A decade later, Scientific American published a news item about an astronomer in South America who had built the “world’s first liquid telescope.” He used liquid mercury…but Byron’s water/molasses telescope spun its astronomical images 10 years earlier…and was much safer to use.
So let your school’s science students build their own, at any size that’s practical, using a variety of fluids. Who knows, they may also discover the truly “astronomical” scientific benefits of plain ol’ black-strap molasses!
