Gravity

Gravity is the natural force by which celestial bodies are atracted to each other, specially when a body with a large mass pulls a smaller one towards it. The gravity is directly proportional to the mass, the larger the mass, the stronger the pull of gravity. In space stars are the bodies with the strongest gravitational attraction, as celestial bodies, but as celestial entity, it is the black holes.

To make it graphical for a better understanding of this natural phenomenon, let's imagine that space were a big mattress. Let's put a wooden ball on the mattress. The ball will distort a bit the surface of the mattress, but if we put a marble ball of the same diameter nearby, the distortion will be deeper as the wooden ball will roll down towards the marble ball. What will happen if we put a steel ball of the same diameter? The two former balls will roll down the mattress slope towards the steel ball. So, the moon is under the gravitational attraction of the Earth, and the Earth is under the sun's gravitional pull, as the sun has a much greater mass. So, we can say that mass warps space.

It was the English mathematician Sir Isaac Newton (1642-1727) who formulated the Law of Gravity in 1687. Gravitational force = (G m1 . m2) / (d2)
where G is the gravitational constant, m1 and m2 are the masses of the two objects for which you are calculating the force, and d is the distance between the centers of gravity of the two masses.