Scientists often use models of the earth because

Scientists often use models of Earth to study the movement of earth and it's moon. They figure out what the distance is from the moon to the point between earth and moon where the gravitational pulls of earth and moon are equal.

the framers of the constitution insisted that federal judges be nominated instead of elected due to their desire to have judges above the shifting whims of the masses.

the hope, whether achieved or not, was that federal judges would only be beholden to the law and that by not having judges be elected, they would be protected if that law dictated an outcome that ran counter to popular opinion.