This is the first course in the cosmology series offered on this platform. We will study an approximate picture of the universe, in which the universe is homogeneous and isotropic. In cosmological perturbation theory, the third course in this series, this is called the background universe. We will start with Hubble`s observation that the universe is expanding, and derive Friedmann`s equations. We will familiarize ourselves with the framework for answering two big questions.
What is the age of the universe? What is the content of the universe?
A deeper question is how much evidence we have in the favor of the Big Bang. To gain some understanding into why we believe in the Big Bang, we need to complete all courses in this series. Some of our questions will remain open at the end of this series.
We all may have our own conjectures about various open questions. It is possible that our understanding of the universe, as it stands today, may experience a radical shift by some new observation down the road.