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Dr. Phil Metzger @DrPhiltill
, 8 tweets, 2 min read Read on Twitter
My son and daughter were going to sleep on the float at the end of the dock, tonight, but at 2 am the boy came back to the house leaving her fast asleep but alone down there. So now I'm trying to sleep on the hard, rocking, wooden float, next to her. /1
2/ I hear seals howling occasionally in the distace, the bell buoy chiming steadily in the middle of the bay, little waves sloshing against the rocky shore, a kayak banging against the float, and -- I think -- waves crashing far away.
3/ Which makes me wonder. If the waves are so large I can hear them crashing violently against some shore, why are they so small where I am? Where does the wave energy die away? The bell buoy seems to be in an intermediate state, rocking just enough to make constant chimes.
4/ I can't see out to the ocean where I am. MacMahan Island blocks the view. Large ocean swells often come north up the bay in the deepest, central part, and they crash on islands and rocks. But they would have to refract westerly around MacMahan's corner to come to me.
5/ Wave refraction is a cool phenomenon. Huygens explained it like this: imagine at every point the wave tries to go equally in all directions. Two adjacent waves try to go into each other's space, blocking each other and forcing each other to go straight. en.m.wikipedia.org/wiki/Huygens–F…
6/ But when there is no adjacent wave, like at the corner of an island, the wave just past the edge of the island CAN go into the adjacent space, wrapping around the island's corner. So waves go around corners and fill all the space.
7/ So why aren't the violent ocean waves that are coming up the bay, rocking the bell buoy, also refracting around MacMahan Island and rocking our float more? (This is what we must wonder, while lying on a float at night and listening to the clues.)
8/ I suppose the particular shape of the underwater landform off the coast of MacMahan prevents waves refracting around that corner. So the wave energy stays out in the channel where the bell buouy is. And I am finally getting sleepy.
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