This is the final project of a class I took at Stanford. While I took it mostly because of the requirement, I have always been interested in astrophysics and cosmology. My friend Xiao once put it “astrophysics is men’s romance,” and that is so true. I would not say I know a lot about astrophysics and cosmology, but I indeed know more than common people’s average and enjoy so much explaining these stuff to others.

I can explain this paper, for example. There are basically three components in our universe that drive the evolution of it, matter (including normal matter and dark matter), radiation (which is important in early universe but pretty insignificant now), and dark energy (we don’t know what it is but we know what it does). Different combinations of the densities of those components leads to different evolution trajectories, which has an observable effect. We can use these observation to determine the possible densities of these components. The conclusion is the current universe is probably flat, with 30% matter and 70% dark energy. Period.