Here's why:

* Mass: The more massive the objects, the stronger the gravitational force between them.

* Distance: The closer the objects are, the stronger the gravitational force between them.

Newton's Law of Universal Gravitation describes this relationship mathematically:

F = G * (m1 * m2) / r²

Where:

* F = gravitational force

* G = gravitational constant

* m1 and m2 = masses of the objects

* r = distance between the centers of the objects

As you can see from the equation, the force is directly proportional to the product of the masses and inversely proportional to the square of the distance. This means:

* Increase mass: Force increases

* Decrease mass: Force decreases

* Increase distance: Force decreases

* Decrease distance: Force increases