Here's why:

* Newton's Law of Universal Gravitation: This law states that the force of gravity between two objects is directly proportional to the product of their masses. This means that the more massive an object is, the stronger the gravitational force it exerts, and the stronger the gravitational force it experiences from other objects.

* Mass vs. Weight: It's important to distinguish between mass and weight. Mass is a measure of the amount of matter in an object, while weight is the force of gravity acting on that object. So, while a heavier object has a greater weight, this is because it has more mass, and therefore experiences a stronger gravitational force.

Let me know if you'd like to explore this further!