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Does light have mass? - Desy

www.desy.de/user/projects/Physics/Relativity/SR/light_mass.html

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Light is composed of photons, so we could ask if the photon has mass. The answer is then definitely "no": the photon is a massless particle. ... Energy, they say, is equivalent to mass according to Einstein's famous formula E = mc². They also say that a photon has momentum, and momentum p is related to mass m by p = mv.

How much does light weigh ? | Notes and Queries | guardian.co.uk

https://www.theguardian.com/notesandqueries/query/0,5753,-12551,00.html

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At the same time, a photon cannot have mass and, therefore, weighs nothing. The theory of relativity tells us that the mass of an object is proportional to the ...

 

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