Conversation so far:
what is earth's motion around the sun in a path called
The Earth orbits, or revolves around the Sun. This movement is called revolution.
who used a pendulum to test earth's rotation
Léon Foucault was a French physicist best known for his demonstration of the Foucault pendulum, a device demonstrating the effect of the Earth's rotation.
how long does it take earth to make one rotation
Earth rotates once in about 24 hours with respect to the Sun, but once every 23 hours, 56 minutes, and 4 seconds with respect to other, distant, stars
what is the axial tilt of earth
Today, the Earth's axis is tilted 23.5 degrees from the plane of its orbit around the sun.

Question: does the tilt vary
Self-contained rewrite: does the axial tilt of earth vary