【英语时差8,16】虫子，涟漪与水上行走-上

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On our last program, we learned how water bugs² manage to stand on the surface of a pond: The pads of their feet resist contact with the water just like wax paper does. This allows the bug¹ to rest on the thin film of surface tension that naturally covers the pond. This surface tension film is caused by the strong attraction the surface water molecules³ have toward each other, as well as toward the water beneath them. While this is fine for standing⁴ on water, you might wonder how a water bug actually starts moving. After all, there’s virtually no contact between the bug’s feet and the water, so there’s no friction⁵ for the bug to push against. It would be like wearing slippery shoes on flat, wet ice-you might slide your feet around, but you couldn’t get anywhere.

 

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