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Science Frontiers ONLINE No. 107: Sep-Oct 1996 |
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More Sparks On The Beach
Sharp eyes often pick out unusual phenomena in very usual places. From California, A. Hastings writes:
"I also had an experience with 'Sparks on the Beach' as in SF#104/4. This was on the Pacific Ocean Beach at San Gregorio, south of San Francisco, several years ago. I was walking on fairly wet sand, just above the tide line. As I stepped, the sand around my feet lit up with small bright dots of phosphorescence. I would not have said that the color was blue, but it could have been like blue-white, like the star Rigel. I found that if I stepped hard or stamped my foot, the lights flashed brighter and the lit area went out farther from my foot. I could see the movement expanding out. After a stamp or two, they did not light up as much. I assumed that this was caused by some organism that lit up when it felt pressure, and 'wore out' after it had done this a few times -- a refractory period probably occurred."
(Hastings, Arthur; personal communication, March 21, 1996)
Comment. This is probably a pressureinduced biological phenomenon, but we have no idea what kind of organism produces the lights. Footsteps do produce a rapidly expanding pressure wave on damp sand, which whitens the sand as it moves outward. But we have never seen any luminosity on our Atlantic beaches, even on dark nights.