Wednesday, January 13, 2016

Tides are Like Pimples

I still struggle with tide tables and other calculations related to tides and currents. Now I have just learned that what we have always been taught about what causes tides is incorrect.

An interseting video that is part of a fascinating series of videos about physics explains What Physics Teachers Get Wrong About Tides.  The series is largely about quantum physics, but this video explains things only with Newtonian physics.

It starts out saying that the standard diagram we have all seen about how the moon (and to a lesser extent the sun) causes a bulge in the water on each side of the earth in line with it is correct, but the typical explanation is not correct.  The incorrect explanantion is that the moon pulls the water on each side as if it were taffy, whereas in reality the bulges come from the downward pressure of the tidal vector at ninety degrees to the bulges - like squeezing a pimple at the edges and forcing the fluid up in the middle.

How poetic.

Anyhow, the tides still work the way we know them to work and I still struggle with tide tables.

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