When we look at the action of gravity at the elementary particle level of Energy Body Theory, we can see that elementary particles and gravitational fields act and react, forming distortions in the foot of elementary particles and generating kinetic energy, which is a wave in space. This is the cause of gravitational mass and is the same cause as inertial mass. The gravitational field forms a spherical layer with a Planck scale thickness in which the amount of energy decreases as it approaches the star. For this reason, the action and reaction between the gravitational field and elementary particles occurs continuously toward the center of the star. For this reason, the increase in distortion in the foot of elementary particles and the increase in kinetic energy are continuously generated and added up. This is explained using a model airplane and a photon released from a free-falling elevator. When photons are in a gravitational field, their speed increases, but since they do not act or react with the space of the gravitational field, there is no increase or decrease in shape or energy.