¿Dónde se me habrá perdido la masa?
(Pedimos disculpas por escribir este post en inglés, pero en este caso nos ha parecido más apropiado usar este idioma para comentar un artículo escrito en él.) After a period of silence that we have devoted to our real-life jobs, we are back, with replenished energies, to comment the article Where is the mass of a black hole? Recently published by Francisco Villatoro ( Francis ) in the otherwise interesting blog Mapping Ignorance . We are afraid that in this case the title of the blog describes the content of the article very well. Francis is a well-known science blogger who also give many popular science talks, participates in podcasts etc. We have commented some of his work in other posts… to no avail. We will keep trying, because his articles start our alarms and red lights very often and many people read them... This article contains so many and so deep misconceptions about the mass in General Relativity that it is not surprising that he arrives to such a great deal of w