Gravity is the invisible force that causes objects to fall towards the Earth’s surface instead of up into the sky. But what exactly is gravity and why does it make things fall downwards?
Gravity is a fundamental force of physics that exists between all objects that have mass. Isaac Newton was the first scientist to quantitatively describe gravity in the 17th century when he formulated his law of universal gravitation. This law states that every particle in the universe attracts every other particle with a force that depends on the masses of the particles and the distance between them.
The larger the masses of the two objects, the greater the gravitational force. Earth’s gravity is what keeps everything attached to its surface including the atmosphere, oceans, and all lifeforms. The reason objects fall down instead of up when released is due to Earth’s much larger mass compared to the masses of objects on its surface.
Earth has a mass of around 6 x 1024 kg whereas a 1 kg object has a tiny mass in comparison. Therefore, the gravitational force exerted by Earth vastly overpowers any gravitational effects the smaller object may have. This imbalance in gravitational forces causes the smaller object to be pulled towards Earth when released rather than being repelled away from it.
Interestingly, when two objects are far away from any other masses, they will actually orbit their combined center of mass when interacting gravitationally rather than fall towards each other. This is why the Earth orbits the sun – the sun’s mass is so much greater that the center of mass between Earth and sun resides inside the sun itself.
Gravity gets weaker with increasing distance. This inverse square law means that the gravitational pull between two objects decreases by a factor of 4 when the distance between them doubles. This explains why gravity keeps objects attached to Earth’s surface rather than pulling them from farther away.
The gravitational force follows an inverse square law because the field lines from an object spread out in 3D space. With increasing distance, the field lines are spread over a larger and larger surface area which dilutes the field strength. Gravity acts at all distances but its effect drops off exponentially with distance.
So in summary, gravity is the attractive force between all objects with mass. The huge mass of the Earth compared to objects on its surface results in the downward pull of gravity that causes everything to fall downwards instead of upwards when released near Earth’s surface. Gravity gets weaker over distance but is always present as an attractive force between masses according to Newton’s law of universal gravitation.