Photon mass (was: [Still off-top] Physics)

[Thomas 'PointedEars' Lahn]

Gene Heskett wrote:

> I've never heard of a massless photon,

That is unfortunate as it should be common knowledge by now.

> and they do exert a push on the surface they are reflected from, […]

Photons exert a force on surfaces because they carry *momentum* or, as it 
had been understood in terminology that is obsolete now, a non-zero 
“*relativistic* mass” (that had been distinguished from “rest mass”).

<https://en.wikipedia.org/wiki/Mass#Mass_in_relativity>
<https://en.wikipedia.org/wiki/Mass_in_special_relativity#Relativistic_mass>

F'up2 sci.physics.relativity

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PointedEars

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