Question

The Earth-Sun system contains gravitational and kinetic energy. Discuss what happens to this energy as the Earth goes around the Sun: Is one type of energy continually decreasing or increasing? Is this energy being transformed into thermal energy? Is this energy being replenished constantly somehow?

Answer 1

Earth moves in an elliptical path around Sun. It's distance from Sun keeps changing.

As earth comes closer to sun, gravitational potential energy decrease, while kinetic energy of earth increase. As it moves away from sun, gravitational potential energy increase, while kinetic energy decrease. Sum of kinetic & gravitational potential energies remains constant.

Hence there is no continues increase or decrease of these energies. As sum of these energies remains constant, no thermal energy is generated or energy replenished.