Why does a ball fall to the ground when you drop it? Why don't we float off into space? The answer to both questions is the same: gravity. Gravity is a force that pulls objects toward each other. It's an invisible string, connecting everything in the universe.

Everything that has mass—from the tiniest speck of dust to the largest star—has gravity. The more massive an object is, the stronger its gravitational pull. This is why we are stuck to the Earth. Our planet is so massive that its gravitational pull is strong enough to hold us, the oceans, and the atmosphere in place.

The story goes that scientist Isaac Newton was sitting under a tree when an apple fell and hit his head. This simple event sparked a profound question in his mind. He wondered why the apple fell straight down, not sideways or up. He realized the same force that pulled the apple to the ground might also be the force that keeps the Moon in orbit around the Earth.

You experience gravity every moment of every day. When you pour milk into a bowl, gravity pulls it down. When you jump, gravity brings you back to the ground. It's the reason a thrown baseball eventually curves back to Earth.

While you have your own gravitational pull, it's incredibly tiny because your mass is small compared to Earth's. You don't see people or objects being pulled toward each other because the force is too weak to overcome other forces, like friction.

The force of gravity depends on two things: the mass of the objects and the distance between them. The more massive the objects, the stronger the pull. The farther apart they are, the weaker the pull becomes.

For now, just remember that gravity is the silent force that keeps our feet on the ground. It governs the motion of everything from falling apples to the planets themselves.