I wonder if there is any major part of physics that has changed so fundamentally in the last thirty years as cosmology.

Back in 1987 cosmology was more or less the last module we were taught as part of the astrophysics degree. But what we were taught then seems like basic arithmetic compared to today’s differential calculus.

The depth of the change in perspective has been brought home to me by reading Max Tegmark‘s Our Mathematical Universe. Tegmark’s book has only just been published but is already out of date in the sense that he speculates that the imprint of gravitational waves in the cosmic microwave background will be a key piece of evidence to support theories of an inflationary cosmology – and we now know that such imprints have been found.

But what is really shocking is Tegmark’s – convincing – argument that what we already knew supports inflation and inflation means we must live in an infinite multiverse. Moreover he completely clobbers the idea that multiverses are unscientific speculation: the evidence, he says, is all around us and the theory fully falsifiable in Karl Popper’s sense.

The book is an easy read – it is semi-autobiographical – and I have made a lot of progress with it in just a couple of days. Certainly recommended.