Gravity is a force that every mass exerts on every other mass. When you jump up in the air, not only does the Earth exert a gravitational force on you, but you also exert a gravitational force on the Earth. You, of course, fall back down to the Earth. Which of the following explains why the Earth is not moving toward you when you jump up in the air? A. Earth exerts a gravitational force on itself. B. You don't weigh enough to affect Earth's surface. C. Your mass is very small compared to Earth's mass. D. Earth's fixed orbit around the Sun keeps it from moving.

 C. Your mass is very small compared to Earth's mass.

According to Newton's third law of motion, every action has an equal and opposite reaction. When you jump up in the air, you exert a force on the Earth downward, and the Earth exerts an equal and opposite force on you upward. This force is gravity, and it affects both you and the Earth. However, the effect of the gravitational force on you and the Earth is not the same due to the significant difference in mass between you and the Earth.

The reason the Earth doesn't move towards you noticeably when you jump is because of its massive size compared to yours. The Earth's mass is so enormous that the acceleration caused by your small force (due to your much lower mass) is imperceptibly small. On the other hand, since your mass is so much smaller, the force exerted by the Earth on you results in a much greater acceleration, which you experience as being pulled back down to the ground.