Water surface tension

If you look closely at a puddle during a rainstorm, you see a weird thing: little balls of water skating around as though the are being rejected by the receiving pool. They disappear quickly, so it’s hard to keep your eye on them. What’s going on? What would it look like if you had faster eyes?

Via Steve Crandall I came across this lovely slow motion video of bouncing water drops. For an instant, before the intervening air is squeezed out, the taut surface of the puddle is essentially a trampoline for descending droplets. I’ve always wondered about the physics of this. Watch!

One thought on “Water surface tension”

  1. I was struck by the comment about “letting the air molecules get out of the way” before the surfaces can coalesce, and was thinking, “I wonder what would happen if you did the experiment in a vacuum?” Then I remembered…

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