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Name:  Alex W.
Status:  other
Age:  20s
Location: N/A
Country: N/A
Date: 1999 - 2000


Question:
I've read that Physicists have calculated that all the known mass in the Universe is quite less that in should be, considering the Big Bang and how much mass should have been created. Thus, they assume there is "Dark Matter." I had a thought, last night, about Photons. Photons have mass, however miniscule, or so I am told. If you consider the mass of all the photons, traveling from every star and luminous body in the heavens in every conceivable direction, does this eleminate the need to imagine Dark Matter, or had They already considered that?


Replies:
Photons do not have mass. They have momentum, but not mass. This is confusing from a classical mechanical view because we say momentum (p) = mass(m) x velocity(v). But that is a classical concept, and photons are described by quantum mechanics, in which this separation of mass and velocity cannot be made. The "Dark Matter" has to come from something else that is unknown at this time. But your suggestion is by no means silly or improper; it is a valid question, but the answer does not hold up when the correct quantitative mathematical theory is applied.

Vince Calder



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