by David Tong



The primary purpose of these html notes is to allow screen reading software to convert equations into synthesised speech. This should (hopefully) work. I have made no effort to make the equations look pretty and while they appear nicely on some browsers, they fail to render correctly on others. It's a bit hit and miss with some of the figures as well. If you're not using speech conversion software then you will likely be better served by the lecture notes in pdf form.


This is an introductory course on cosmology aimed at mathematics undergraduates at the University of Cambridge. You will need to be comfortable with the basics of Special Relativity, but no prior knowledge of either General Relativity or Statistical Mechanics is assumed. In particular, the minimal amount of statistical mechanics will be developed in order to understand what we need. I have made the slightly unusual choice of avoiding all mention of entropy on the grounds that nearly all processes in the early universe are adiabatic and we can, for the most part, get by without it. (The two exceptions are a factor of 4/11 in the cosmic neutrino background and, relatedly, the number of effective relativistic species during nucleosynthesis: for each of these I’ve quoted, but not derived, the relevant result about entropy.)