Newton stated in his Universal Law of Gravitation that every particle in the universe is attracted to every other particle. The mass of the particle determines the amount of pull. Mass is the quantity of substance in the particle. The mass and the distance between the particles cause the gravitational pull.

Newton’s Law of Gravitation states that:

• Any object or piece of matter, from a planet to a pinhead, has an attracting or gravitational force.
• The gravitational force between two objects is proportional to the product of their masses.
• The gravitational force varies with the distance between the two objects (the gravitational force of an object weakens extremely quickly as you get farther from it). Mathematically, the force weakens according to the inverse square of the distance (in math, a square is a number multiplied by itself, and an inverse square is that number divided by one). If the distance between two objects is doubled, the force between them is reduced to one-fourth. It the distance is tripled, the force is reduced to one-ninth, and so on.
• The formula is:

F = Gm₁m₂/r²,

Where F is the gravitational force, G is the gravitational constant (a number that is always the same), m₁ and m₂ are the masses of the two objects, and r is the distance between them.