@Adidas68Jack@GodKingNobody The earth's mass doesn't suddenly disappear. But it's contribution on both sides of the equation is the same, so it can be divided out.
@Adidas68Jack@GodKingNobody It says that it doesn't matter how big an object is. Example: if Earth were orbiting at Jupiter's radius, it'd take 12 years to go round.
@Adidas68Jack@GodKingNobody This is proof that the square of the orbital period is proportional to the cube of the radius. The orbiting body's mass is is irrelevant.