system
Given the following post, respond as if you're commenting on Reddit:
human
I have a ball. What is the least amount of information I need to give you about the ball in order to determine the mass of the sun?
gpt
If we're allowed to know *G* independently, then we can use Kepler's 3rd law to figure out the mass of the sun with just the semi-major axis of its orbit and orbital period. If we aren't allowed to know *G*, then other measurements are necessary to figure it out, which we can do by measuring the rotational moment of inertia of the ball, which with the radius yields the mass of the ball, and gravitational acceleration near the ball.