1. Newton's Law of Universal Gravitation
* Equal and Opposite: Newton's law states that every object in the universe attracts every other object with a force that's directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers. This means that the apple exerts a gravitational force on the Earth, just as the Earth exerts a force on the apple. These forces are equal in magnitude but opposite in direction.
* Why the apple moves: While the forces are equal, the Earth is vastly more massive than the apple. This means that the apple experiences a much larger acceleration due to the force of gravity than the Earth does.
2. Acceleration and Inertia
* The apple's motion: The apple accelerates towards the Earth because of the gravitational force acting on it. It has very little inertia (resistance to change in motion) compared to the Earth.
* The Earth's (almost) imperceptible motion: The Earth also accelerates towards the apple, but because of its enormous mass, the acceleration is extremely small and practically immeasurable. It's as if the Earth is completely stationary.
3. The Illusion of Rest
* Relative motion: The apple falls towards the Earth because the apple is much smaller and less massive than the Earth. The Earth's motion is so insignificant compared to the apple's that it appears the Earth is stationary and the apple is the only object moving.
In Summary:
The gravitational force between the apple and Earth is indeed equal and opposite, but because of their vastly different masses, the apple experiences a much greater acceleration and appears to move towards the Earth. This is why we perceive the Earth as being stationary while the apple falls.
