Planetary Analogues: Other Planets Here on Earth

One of the most incredible things about the universe we live in is that the laws of physics are the same everywhere. Let go of an object above the surface of the Earth, and it will be accelerated downward at a velocity determined by the ratio of total mass of the matter below and the object’s distance from the center of that mass. Let go of an object above a planet a billion light-years away, and it will be accelerated downward by the exact same ratio of mass and distance. The fundamental rules that make the universe “work” are the same across the entire cosmos.