On 2017-10-05 06:24, Steve D'Aprano wrote: > On Thu, 5 Oct 2017 02:14 pm, Stefan Ram wrote: > >> Chris Angelico <ros...@gmail.com> writes: >>> You can get through a lot of life believing that mass is conserved, >>> but technically it is not, as can be proven. >> >> Well, in fact, it is conserved. > > It certainly is not. The whole point of Einstein's equation E = mc² is that > energy and mass are freely convertible. Neither energy nor mass alone are > conserved.
You're both right, you're just defining "mass" in different ways. > > >> When an electron and a positron annihilate to give a gas of >> two photons, this gas as a whole still has the same mass as >> the electron before. And its center of gravity moves with >> less than c. > > That doesn't sound like any description of matter/anti-matter annihilation > I've every seen before. > > I think you may be conflating the concepts of clouds of virtual > electron/positron particles with actual annihilation events between real > electron/positron particles. > > In actual annihilation events, there is (as far as I know) generally a single > real photon produced, with momentum equal to the sum of the momentum vectors > of the original electron and positron. That moves away from the point of > production at the speed of light. > > > -- https://mail.python.org/mailman/listinfo/python-list
