Yes, a marching band, or the wheels on a truck have a differencial.. (by an large, trains don't, so curve on trains are much wider and rounder than curves on roads.. but there are other differences as well..)
a differencial gear (actually several gears,) allows the inner wheel to turn slower than the outer wheel.. In marching bands, the rows on the inside of the turn take smaller steps, and the rows bunch up a bit.. the marchers on the out side of the turn take larger steps, and the rows splay out slightly.
but i hadn't thought of the tide working the same way--
especially because High tide in lower manhattan come at a different time that high tide in greenwich CT, about 25 miles away.. (something else i have never quite understood)
i guess its sort of like a wave in a stadium.. High tide is standing, low tide is sittting, and high tide moves..but looking at the local tide tables, its doesn't make too much sense..
