This discussion about energy and masses of particles has nothing to do with Python, and I am hoping that it will be dropped. That being said, I feel compelled to correct what are completely wrong statements.
On Friday, 4 March 2016 13:36:11 UTC-4, Oscar Benjamin wrote: > On 4 March 2016 at 10:38, Marko Rauhamaa <ma...@pacujo.net> wrote: > > Oscar Benjamin <oscar.j.benja...@gmail.com>: > > ... > > That's just a casual use of terminology. If we want to be precise then > it's pointless to even refer to the "rest mass" of something that is > never at rest. The masslessness of photons comes from an extrapolation > that leads to a divide by infinity: strictly speaking it's just > undefined. This is simply wrong. In Quantum Field Theory, particles can have "bare" mass term included in the Lagrangian and the measured mass either includes the bare mass + quantum corrections OR is a purely dynamically generated term. In the Standard Model, there is no bare mass term for the photon, nor is there any dynamically generated mass. In fact, to preserve gauge invariance symmetry, the mass of the photon MUST be identically equal to zero. (Of course, the Standard Model could be incorrect but all meausurements done so far are completely consistent with a massless photon; see http://pdg.lbl.gov/2015/listings/rpp2015-list-photon.pdf for current experimental limits.) > > > As for the existence of a negative mass, it is interesting to note that > > the (rest) mass of an alpha particle is less than the sum of the (rest) > > masses of its constituents. About 1% of the mass is "missing." > > Since the binding is associated with negative energy it has a negative > contribution to the energy/mass of the particle as a whole. This is > true of any bound state. > > Something I don't know is if there's some theoretical reason why the > binding energy could never exceed the sum of the energies of the > constituent particles (resulting in an overall negative mass). The (magnitude of the) binding energy is DEFINED as the difference between the (energy equivalent) sums of the individual masses of the consistuents and that of the bound state. === Now, could we forget about Physics and go back to discussions related to Python? André Roberge > > -- > Oscar -- https://mail.python.org/mailman/listinfo/python-list
