# If photons don't have mass, how can they accelerate objects? [duplicate]

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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?

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

This question was marked as an exact duplicate of an existing question.

okay got it! it doesnt have nothing to do with momentum the electric charges that forms light make it sail.. – Arun Malik Feb 19 '14 at 15:46
It does have everything to do with momentum. Light does not have charge or mass, but it does have momentum. en.wikipedia.org/wiki/Photon#Physical_properties – Hans-Peter E. Kristiansen Feb 19 '14 at 15:56
It comes down to them having momentum, which brings us to physics.stackexchange.com/q/2229 – dmckee Feb 19 '14 at 16:01