A few days ago, I stayed in the Vatican (more about this one day symposium in another post). During the stay, I naturally visited St. Peter's Basilica. Near Bernini's Altar, I saw corpuscular rays. It may seem like some godly thing (quite appropriate for the location), but from a physicists point of view, it is simply scattering by dust particles. Here is one can say about this holy dust with the help of a little envelope.