Law of Universal Gravitation

The Law of Universal Gravitation is a law that states that every mass in the universe attracts every other mass with a force proportional to the product of their masses and inversely proportional to the square of the distances between their centers.

$F={\frac {GMm}{r^{2}}}$

Where

• $F$ is the gravitational force
• $G$ is Newton's gravitational constant
• $M$ is the mass of the first mass
• $m$ is the mass of the second mass
• $r$ is the distance between the two masses

The observed acceleration in the expansion of the universe is difficult to reconcile with the Law of Universal Gravitation, and large amounts of unseen Dark Energy has been hypothesized to address this.