This brought to mind a cute way to think about the Foucault Pendulum.
The idea is to select a given latitude on Earth, and then imagine a cone that "just fits" that latitude, in the sense that it is tangent to the earth all the way around at that latitude. Draw a line all the way around the cone at the given latitude. Then imagine using a pair of scissors to cut the cone vertically up to its apex, and flattening it out to make a circle that is missing a pie slice.
A single full rotation of the earth would be equivalent to "driving a car" from one edge of the pie slice all the way around the latitude line to the other edge of the pie slice. At the end of the trip, the car will be pointing in a different direction from the one it started, for every latitude except the poles and the equator.
The angular rotation of the car from the start to the end of its trip is the amount a Foucault pendulum would rotate in 24 celestial hours at a given latitude on Earth.
The idea is to select a given latitude on Earth, and then imagine a cone that "just fits" that latitude, in the sense that it is tangent to the earth all the way around at that latitude. Draw a line all the way around the cone at the given latitude. Then imagine using a pair of scissors to cut the cone vertically up to its apex, and flattening it out to make a circle that is missing a pie slice.
A single full rotation of the earth would be equivalent to "driving a car" from one edge of the pie slice all the way around the latitude line to the other edge of the pie slice. At the end of the trip, the car will be pointing in a different direction from the one it started, for every latitude except the poles and the equator.
The angular rotation of the car from the start to the end of its trip is the amount a Foucault pendulum would rotate in 24 celestial hours at a given latitude on Earth.