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As far as I know photons don't have mass but they do have momentum ($p=mv$). Scientists say that if we put a shiny (reflective) shield of large radius in the vacuum of space, then light from sun will will start moving the shield. How can these two facts be commensurate?


marked as duplicate by Kyle Kanos, John Rennie, Willie Wong, dmckee Feb 19 '14 at 16:02

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