Here's why:

* Newton's Law of Universal Gravitation: This fundamental law states that the force of gravity between two objects is directly proportional to the product of their masses and inversely proportional to the square of the distance between their centers.

* Formula: F = G * (m1 * m2) / r^2

* F = force of gravity

* G = gravitational constant

* m1 and m2 = masses of the objects

* r = distance between the centers of the objects

* The bigger the mass, the stronger the pull: The formula shows that if you increase either m1 or m2 (the masses of the objects), the force of gravity (F) will also increase.

In simple terms: The more massive an object is, the stronger its gravitational pull on other objects around it.

Examples:

* The Earth: The Earth has a large mass, which is why we are held to its surface by gravity.

* The Sun: The Sun's immense mass is what keeps the planets in our solar system in orbit around it.

* Black Holes: Black holes have incredibly high densities and enormous masses, resulting in such strong gravitational pulls that not even light can escape.