Remember the difference between weight and mass?An anvil will be weightlessin space because there is no gravity.But it still has mass, so it would be hard to shake.Something with a large mass requires a large force to make it accelerate
The origin of the gravitational forceAny two objects with masses M, m attract each other with a force (G is Newton’s constant):The gravitational force which we experience is due to the Earth.
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Newton’s insight was that the same force which causes the Moon to accelerate (why?) towards the Earth also causes an apple to accelerate towards the Earth.The Moon is less massive than the Earth (but its radius is also smaller).I just lost 150 lbs! If you weigh 180 lbs on Earth, you would weigh only 30 lbs on the moon.