Observations of a planet moving among the stars over the course of a year provide evidence that the Earth revolves around the Sun.

Here's why:

* Retrograde Motion: Planets appear to move backwards (retrograde) in the sky for short periods. This happens because the Earth is overtaking the outer planets in its orbit.

* Changing Position Relative to Stars: The planet's position in the sky changes noticeably over the year, shifting against the background stars. This movement is a direct result of the Earth's own orbital motion around the Sun.

These observations were crucial in supporting the heliocentric model of the solar system, where the Earth revolves around the Sun, rather than the geocentric model, where the Sun revolves around the Earth.