The approach to the treatment of mass in relativistic mechanics advocated in the article by Keith
Atkin in the January 2015 issue of Physics Education (2015 Phys. Educ . 50 46) conflicts with the
viewpoint promoted of many eminent physicists for over half a century. This comment attempts to
explain some of the ideas behind the latter approach and to illustrate how it helps to simplify the
teaching and learning of the topic.