This post is a bit off topic to my blog, but there are some things in popular science that really bother me. One of the groups that I follow on Facebook posted a clip on Twins Paradox in Special Relativity. Again! There is no such thing as Twins Paradox in Special Relativity. In order to compare the ages of the twins, you need to return them to the same point. You have to accelerate (decelerate) at least one of them, making his/her frame of reference a non-inertial one. This means we cannot longer use Special Relativity. Only General Relativity has non-inertial frames of reference. For detailed explanations one can look at the famous Landau & Lifshitz book.

To me, it was always a criterium of a good vs bad book on Special Relativity: if there is a chapter on Twins Paradox, I would never buy a book.