Re: Positrons

"Paul.B.Andersen" <relativity@paulba.no> wrote or quoted:

  e⁺ + e⁻  →  γ + γ
Energy and momentum are preserved.
The energy equivalence of an electron and a positron is 0.511 MeV,
so the energy of each of the gamma particles is 0.511 MeV. (0.024 Å)
(Mass is converted to pure kinetic energy of photons)

  BTW:

  Mass is /not/ changed in this process when the mass of the system
  "γ + γ" is being compared with the mass of the system "e⁺ + e⁻".

  The total momentum of the system "γ + γ" is 0 when we assume that we
  had chosen coordinates in which the total momentum of the system
  "e⁺ + e⁻" was 0. So all the energy of "γ + γ" still is mass energy
  (zero momentum, non-zero mass).

  Only when one (mentally) changes the definition of the system and
  looks at one of those "γ" in isolation has one a system with zero
  mass and non-zero momentum!