Hi, In a Particle Physics class, our instructor requested me to calculate the life time of proton. There are some sources telling that its life time is ~10^32 years, however there are no basic calculations. There is this article about calculation: http://journals.aps.org/prd/abstract/10.1103/PhysRevD.23.1580 However, its level is pretty higher than our classroom. Could provide a simpler calculation? Thanks in advance.