Why Things Fall: The Force Called Gravity

Grab a pencil and a rubber eraser. Hold them out at the same height — one in each hand. Now let go at exactly the same moment. Which one hits the ground first? Most people guess the heavier one wins. But watch carefully. They land at almost the same time! Why does that happen? That puzzle stumped scientists for hundreds of years. Today you are going to find out the answer.

Gravity is a pulling force. A force is a push or a pull that can make objects move, speed up, slow down, or change direction. Gravity is the force that pulls every object towards the centre of the Earth. Everything that has mass has gravity. Mass means the amount of stuff (matter) inside an object. The more mass an object has, the stronger its gravitational pull. Earth is enormous, so its gravity is very strong — strong enough to keep you on the ground, hold the oceans in place, and even keep the Moon orbiting around us. Gravity always pulls downward — towards the centre of the Earth. That is why when you throw a ball into the air, it always comes back down. Gravity never stops pulling. Now, back to the puzzle from the starter. Isaac Newton, a scientist who lived in the 1600s, worked out that gravity pulls all objects with the same acceleration — that means it speeds them up at the same rate as they fall. A heavy book and a light pencil both speed up at the same rate as they drop. So they should land at the same time! In real life, air pushes against falling objects and slows some of them down more than others. This is called air resistance. A feather falls slowly because air pushes against its wide, flat shape. A stone falls quickly because its shape cuts through the air easily. On the Moon, where there is no air, a feather and a hammer really do land at exactly the same moment — astronauts actually tested this in 1971!