This illustration is meant to show an elevator accelerating upward. A beam of light enters a hole on the upper right and the passenger is accelerated upward while seeing the path of the light inside the elevator. Einstein's "Principle of Equivalence" is that the effect of gravity is the same as that of acceleration. Therefore, this example tells us that The path of light is not altered by gravity The path of light is altered by gravity and that light follows a curved path near massive objects, as if attracted to the object, although it has no mass That light has mass That stars appearing near the Sun during a solar eclipse will be at the same apparent position they would be if the Sun were not there