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Skaters slide
Regarding the article “Skateboarders rock at physics” (SN: 12/3/11, p. 10), the skateboarders’ “intuitive” conclusion that the ball will roll faster down the blue ramp (which is longer but has two steeper sections compared with the shorter red ramp with a single shallower section) depends on the particular geometries chosen for the two ramps.

I’ve programmed the solution for a point particle sliding (so no rolling) without friction down the two ramps and find that for certain ratios of the heights and lengths of the various ramps, it can actually be faster to slide down the red (single) ramp. Intuition can only go so far in such problems.

A full examination of the problem requires analysis and calculation to aid intuition. Nowadays, this means using a computer to explore all the possibilities.
Don Polvani, Arnold, Md.

Seldon crisis
Tom Siegfried’s editorial about “econophysics” (“Perhaps physics can also solve economic puzzles,” SN: 11/5/11, p. 2) makes it evident that the world needs a real Hari Seldon, the fictional person who mathematically described sociology in Isaac Asimov’s Foundation trilogy.
Mike James, Ottawa, Canada

Living on Venus
I enjoyed reading “Venus Unveiled” (SN: 12/3/11, p. 26). I have always felt that we have slighted Venus in our explorations. If there is one planet that has real promise for human habitation, it is Venus. Of course the current atmosphere is a problem. But I believe a bacteriological terraforming solution could be found that would modify that atmosphere to the point of usability.

We focus so much attention on Mars, but Mars has a much more fundamental problem — not enough mass. Even if you were to magically give Mars an Earthlike atmosphere today, it could not hold onto it. Venus, on the other hand, is 95 percent Earth’s size and has 90 percent of Earth’s surface gravity.  This similarity to Earth makes Venus a much more attractive target for exploration and worth the effort to develop a solution for the atmosphere issue.
Tom DuBois, Glens Falls, N.Y.

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