What is the cosmological principle?

Answer 1

The cosmological principle is the working assumption in cosmology that matter and energy is distributed over the cosmos homogeneously and isotropically, when viewed on a large enough scale. Basically it means that wherever you are in the universe, and whatever way you look, you should see pretty much the same thing.

Answer 2

Large scale studies suggest that the universe is homogenous (the same everywhere) on scales larger than a few hundred megaparsecs. In other words, no matter where in the universe you look on a large scale, the universe would look pretty much the same. The universe also appears to be isotropic (the same in all directions) on large scales. We count about the same number of galaxies no matter what direction we look. All of this will lead to what we call cosmology. This is the study of the structure and evolution of the entire universe. Now we have no idea whether our assumptions are correct, but they are consistent with current observations. These 2 assumptions (that we will assume are true) are called the cosmological principle. Everything that has been stated throughout this book also assumes one other thing: the laws of physics hold true throughout the universe. If these are true, then it says that there is no edge to the universe because that would violate the idea of homogeneity. It also implies that there is no center because that would mean that the universe would not look the same from everywhere.

Answer 3

That our position in the Universe is not unique, i.e., that the Universe would look similar if you watch it from a far-away position.

Answer 4

It refers to the assumption that on a large scale, the Universe looks the same here than in any other part of the Universe.