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The photon has no electric charge, [17] [18] is generally considered to have zero rest mass [19] and is a stable particle. The experimental upper limit on the photon mass [20] [21] is very small, on the order of 10 −50 kg; its lifetime would be more than 10 18 years. [22] For comparison the age of the universe is about 1.38 × 10 10 years.
"Does mass change with velocity?" by Philip Gibbs et al., 2002, retrieved August 10, 2006 "What is the mass of a photon?" by Matt Austern et al., 1998, retrieved June 27, 2007; Max Jammer (1997), Concepts of Mass in Classical and Modern Physics, Courier Dover Publications, pp. 177– 178, ISBN 978-0-486-29998-3
The photon (carrier of electromagnetism) is one of two known gauge bosons that are both believed to be massless; the other is the gluon (carrier of the strong force).The only other confirmed gauge bosons are the W and Z bosons, which are known from experiment to be extremely massive.
This minuscule amount of energy is approximately 8 × 10 −13 times the electron's mass (via mass–energy equivalence). Very-high-energy gamma rays have photon energies of 100 GeV to over 1 PeV (10 11 to 10 15 electronvolts) or 16 nJ to 160 μJ. [5] This corresponds to frequencies of 2.42 × 10 25 Hz to 2.42 × 10 29 Hz.
It has no intrinsic spin, and for that reason is classified as a boson with spin-0. [34] The Higgs boson plays a unique role in the Standard Model, by explaining why the other elementary particles, except the photon and gluon, are massive. In particular, the Higgs boson explains why the photon has no mass, while the W and Z bosons are very
The photon having non-zero linear momentum, one could imagine that it has a non-vanishing rest mass m 0, which is its mass at zero speed. However, we will now show that this is not the case: m 0 = 0. Since the photon propagates with the speed of light, special relativity is called for. The relativistic expressions for energy and momentum ...
Their high masses limit the range of the weak interaction. By way of contrast, the photon is the force carrier of the electromagnetic force and has zero mass, consistent with the infinite range of electromagnetism; the hypothetical graviton is also expected to have zero mass.
The photon must have higher energy than the sum of the rest mass energies of an electron and positron (2 × 511 keV = 1.022 MeV, resulting in a photon wavelength of 1.2132 pm) for the production to occur. (Thus, pair production does not occur in medical X-ray imaging because these X-rays only contain ~ 150 keV.)