What do we mean when we say that the universe is homogeneous?

Question

Quizplus · Accepted Answer

When we say that the universe is homogeneous, we mean that it looks the same at all locations at a given time and on a large enough scale. This means that there are no preferred locations, and on average, the density of matter is the same everywhere.

Option B is incorrect because there are mass concentrations in the form of galaxies, clusters of galaxies, and even larger structures known as superclusters.

Option C is also incorrect because the universe is dynamic and constantly evolving. It had a beginning (the Big Bang), and it has been expanding and cooling ever since.

Option D is partially correct, but it's not as comprehensive as option A. The universe does look the same in all directions, which astronomers call isotropy, but it's important to note that this is also true for a non-homogeneous universe as long as the variations are smooth and gradual on large enough scales.

What Do We Mean When We Say That the Universe