The age of the Universe is now known to within a couple of hundred million years, and measurements have continued to improve. When I wrote my first book it was 13.7 billion years old but we now believe it to be a bit older—13.8 billion years from the so-called Big Bang. Note that it is not only the changing Hubble parameter, but the discovery of the dark energy that I mentioned in Chapter 1, that led to this more refined result, since the age of the Universe depends on both.
