Gravity: The Main Attraction
Gravity's effect is apparent even at the largest scales: just as gravity keeps the Earth orbiting the sun, it holds these two irregular galaxies M32 and M110 in orbit around the larger Andromeda galaxy.
In the late 1600s, the English mathematician Sir Isaac Newton gave the first scientific description of gravitation. Gravity is an attractive force existing between any two objects that have mass, causing them to accelerate towards each other. It is the weakest of the four fundamental forces but can act over great distances and is responsible for the formation of planets, stars, galaxies, and even larger scale structures such as groups and superclusters. Gravity is also the force that governs the motion of celestial bodies.