In 1972-73 I was on sabbatical leave at the Kingston, Jamaica, campus of the University of the West Indies. I taught a few classes and developed a series of demonstration lectures that were given on Saturday mornings for enrichment purposes. The two most popular were “Physics Without Friction” and “Suspension Bridges,” and these were taken on tour throughout the island for school and teacher audiences. In the spring of 1973 I was sent to Georgetown in the Cayman Islands to give these two talks to general audiences. To cool down, I donned mask and fins and swam down about 10 feet to the sandy bottom of Seven Mile Beach. There was no wind and the surface of the sea was like glass. When I looked up, I could see starfish in the sky!

The figure shows what was happening. The starfish were actually on the bottom, and I was viewing...

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