View from the Pennines:A Cosmic Indian Rope Trick

摘要

This year we have had both frogspawn and toadspawn in thepond. The tadpoles emerged first and very quickly startedto eat the toadspawn. Since the toad tadpoles are poisonousto many creatures it is not clear whether the tadpoles were eatingthe developing toad tadpoles or just the jelly, but whichever com-bination they were eating, the carefully roped toadspawn wasrapidly destroyed. It is possible that the frog tadpoles weregetting their retaliation in early and that if they fail to destroy thetoad tadpoles before they leave the spawn they might becomefood for the toads-to-be in their turn. To preserve a few toad tad-poles we removed them from the pond and kept them in a jar. Onecharacteristic I had not appreciated is that whilst frog tadpolesrest horizontally on the bottom of the pond, young toad tadpolesrest vertically with their heads up; a position which would be veryunstable in the absence of the supporting relatively high densitywater. Indeed, I have not discovered the source of the stability ofthis pose, which should be closer to an inverted pendulum thananything else I can think of, but I suppose that a light invertedpendulum could be stable in treacle, though had I been thinkingabout it at the time I would have looked to see whether there wasany periodic oscillation in the tadpoles' tails.