All forms of energy can be converted into another, for example, the Sun's nuclear energy changes to radiant energy that travels through space to Earth. The leaves of an orange tree take in this radiant energy. During photosynthesis the leaves change the radiant energy to chemical energy stored in the plant's cells. When you drink the orange juice, you take in this stored chemical energy. Your body changes some of the chemical energy to thermal energy to keep you warm. Some thermal energy is lost to the air as heat. You change chemical energy to kinetic energy as you move around.