Sean Carroll and the Arrow of Time

Sean Carroll is a cosmologist at CalTech. He is also a gifted teacher.  I became aware of Carroll when my wife and I ordered a lecture series by him from the Teaching Company.  His course was entitled, Dark Matter, Dark Energy: The Dark Side of the Universe.  In the 24 lectures of this course, Carroll explains why the "stuff" we can see in the universe is only five percent of what is thought to be there.  Twenty-five percent is Dark Matter, needed to explain gravitational effects, and seventy percent is Dark Energy, needed to explain the perpetual expansion of the universe.  I would recommend the course. Even though it is taught using layman's language, it is very detailed.

Carroll prepared that course in 2007.  Since that time, he has written a new book called From Eternity to Here: the Quest for the Ultimate Theory of Time.  This book attempts to explain why time goes in only one direction.  "Well", you say.  "Duh?"  But it is not so obvious why time goes in one direction.  The fundamental laws of physics work with time going in either direction.  How can it be that we only get older?  Turns out, entropy has a whole lot to do with it.  Entropy is a measure of disorder and it can only get bigger.  Entropy explains why eggs turn into omelets but not the other way around.

You can see Carroll in action (and for free!) in a two-part video lecture he gave at the University of Sydney in December of last year.  Part One is here and you can see the link for Part Two on the right of that page. Each video lasts 30 minutes. If you like what you see, you can order his book from this link at Amazon or you can read the blog, Cosmic Variance, to which he contributes at Discover Magazine.  He also has his own website. Enjoy.