Dancing with the Salts

More geekiness, in part brought on by the trip to LIGO last week.  My son came home Thursday with two friends and a goal of doing a special experiment and presentation for extra credit for their science class.  Their science teacher had introduced Cymatics and showed them this video on You-Tube:



They rigged up a tone generator from the computer and I helped them cable it into the home stereo. We took a trip to Goodwill, where we found a few big speakers that could be cannibalized ($2.17 total - what a deal!) A little wiring and soldering later, we were able to dial up any frequency and crank it up. Earplugs.

It took some fiddling to get a plate system that would work, but the kids eventually ended with a system that worked and the salt did indeed dance. It wasn't anywhere near as elaborate as the video, but they could see patterns and they did change as they ranged the tones.

With this success, then my daughter described the LIGO demo where they had taped a tiny mirror to the plate in a similar setup and shot a laser pointer at it. As the sound changed, the reflected spot on the wall went crazy due to the vibrating plate! We replicated this with great success, although photographing it was less than representative.

These are called Lissajous figures.  Much fun for me, as I got to play the role of technical consultant.  I could also see the lights flickering behind the eyes of the kids.  I hope they are sparked to further explore. Meanwhile, I must go vacuum the living room...and buy another box of salt.