The gravitational force between objects increases when the mass of one or both objects increases.

Here's why:

* Newton's Law of Universal Gravitation: This law states that the gravitational force between two objects is directly proportional to the product of their masses.

* Direct Proportionality: This means that if you increase the mass of one object, the gravitational force increases proportionally. If you increase the mass of both objects, the gravitational force increases even more dramatically (because you're multiplying the increased masses).

Let me know if you'd like a more detailed explanation or have other questions!