Gravitation

Newton's law of gravitation says the force between two masses is proportional to the product of the masses and inversely proportional to the square of the distance between their centers. Double the distance and the force drops to a quarter. Triple it and the force drops to a ninth. This square-law falloff is why gravity feels strong up close and fades fast as you move away, even though it never fully disappears.

That same law explains why a hammer and a feather hit the moon's surface together. The moon pulls on the hammer with a bigger force because the hammer has more mass, but that bigger force has to accelerate a bigger mass. Acceleration is force divided by mass, and the mass cancels out, so both objects speed up at the same rate and land at the same instant. On Earth, air resistance hides this, but on the airless moon it shows plainly.

Orbits run on the same idea. A satellite with its engines off is in constant free fall toward Earth, pulled by that same square-law force. What keeps it from hitting the ground is sideways speed: it moves fast enough across the sky that as it drops, the curved Earth falls away beneath it at matching rate. The satellite is always falling and always missing. Gravitation, falling motion, and orbital motion are really one mechanism viewed from three angles, and the shift in scale is exactly where weight, free fall, and orbital speed problems connect.