What Is Gravity

Gravity is a force that pulls objects with mass toward each other. This force acts between all objects in the universe. You cannot see gravity, but you can observe its effects everywhere. When you drop a ball, gravity pulls it toward Earth. When you jump, gravity brings you back down. Scientists explain that gravity is a non-contact force because objects do not need to touch for gravity to work between them.

Every object with mass has gravity, including you. However, Earth has much more mass than you do. Evidence shows that objects with greater mass have stronger gravitational pull. Earth's mass is so large that its gravity pulls everything near its surface toward the center of the planet. This is why objects fall downward. The gravitational force between two small objects, like two books on a table, is extremely weak. You cannot feel this tiny force because Earth's much stronger gravity overwhelms it.

Scientists observe that gravity acts over great distances. The Moon orbits Earth because Earth's gravity pulls on it continuously. Similarly, Earth and other planets orbit the Sun because the Sun's enormous mass creates powerful gravitational attraction. The strength of gravity decreases as objects move farther apart. This means the Moon experiences less gravitational pull from Earth than objects on Earth's surface do. Understanding how distance affects gravity helps scientists predict the motion of planets, moons, and satellites.

In 1687, scientist Isaac Newton measured how fast objects fall near Earth's surface. He found that gravity accelerates falling objects at about 9.8 meters per second squared. This measurement applies to all objects regardless of their mass. A feather and a hammer fall at the same rate in a vacuum where air resistance is removed. Astronauts on the Moon demonstrated this phenomenon during the Apollo 15 mission. They dropped both objects simultaneously, and both hit the ground at the same time.

Gravity matters because it shapes our daily lives and the universe around us. Gravity keeps our atmosphere close to Earth so we can breathe. It holds water in oceans and lakes. Gravity allows us to walk on the ground instead of floating away. On a larger scale, gravity formed stars, planets, and galaxies. Without gravity, the universe would look completely different. Understanding gravity helps scientists design buildings, predict tides, and send spacecraft to other planets.

Interesting Fact: Gravity on Mars is only about 38% as strong as gravity on Earth. If you weigh 100 pounds on Earth, you would weigh only 38 pounds on Mars!