Every mass in the universe exerts a force of attraction on every other mass. This is the fundamental principle of gravity, as described by Newton's Law of Universal Gravitation.

Therefore, there is no single "mass" that exerts a force on everything else. Every single mass in the universe contributes to the gravitational force felt by all other masses.

Here's a breakdown:

* Newton's Law of Universal Gravitation: This law states that every particle in the universe attracts every other particle with a force that is:

* Proportional to the product of their masses: The more massive the objects, the stronger the gravitational attraction.

* Inversely proportional to the square of the distance between their centers: The farther apart the objects are, the weaker the gravitational attraction.

* The "Force of Attraction": This force is known as gravity. It's the weakest of the four fundamental forces of nature, but it's the force responsible for holding everything together in the universe – planets orbiting stars, galaxies clustering together, and even the formation of stars and planets themselves.

So, the universe is a complex web of gravitational interactions, with every single object contributing to the force felt by all others.