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Why are photons mass less? do photons decay?

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also with all the gunk in the universe how do we see light from other stars?

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  1. YES!!! they do decay........... whats are photons?


  2. Generally, photons are considered "massless" because it makes equations work well. If we were to attempt greater accuracy, we would say that their "rest mass" mass is extremely small and generally assumed to be zero.

    It is very difficult and possibly impossible to "weigh" a photon, and what we presently have are very small upper limits. By studying magnetic fields of planets, the most certain figure is 6 × 10^(-16) eV.

    Any limit lower than that or proposals, including that they have absolutely zero mass, remain in the realm of theory. For now, we simply consider them massless and consider only their energy.

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    As far as we know, photons do not decay "of their own accord" in empty space. There are theories that they do decay, but it has never been observed, and no evidence supports the idea.

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    Most of the air and even the solids around you are open space. There is "gunk" in the universe that makes it difficult to see in certain directions (like through the galactic core of our own Milky Way), but most of it is completely empty. Especially between stars and even more so between galaxies, there is extremely little matter. The things which we do see, such as nebula clouds, are even extremely widely distributed, but if you look trough many light years of thin gas, it will look quite thick.

  3. Photons don't have quiet mass but they've rough mass.Photons don't decay with v=3.10^8 m/s but they decay when they hit gainst and lose the energy. Photons communicate the energy to the eyes with  their wavelength so we can see light & color from the stars. It's so nice.

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