# Mass and Energy conversion in photon

If energy can be converted into mass then why isn't photon's energy being converted into mass?

• It's called an intrinsic property of photons. If they had finite rest mass, they wouldn't be able to travel at c and as and at the same time follow Maxwell's equations. They would be a different kind of particles – rnels12 Jan 30 at 11:30
• Where did you find that photon's energy isn't converted into mass. as far as I know,photons itself is energy – user212727 Jan 30 at 11:39
• It has to do with closed vs. open systems. A photon in a closed system gives that system rest mass. – Digiproc Jan 30 at 11:57

You probably mean something different than you ask: a photon is influenced by gravity and it behaves as it had a mass when traveling through the space. When it is said that photon is a massless particle, it is in a context that it has no rest mass $$m_0$$ i.e. $$E^2=m^2c^4=p^2c^2 + m_0^2c^4$$ turns into $$p^2c^2$$ ($$p$$ is momentum), but $$mc^2$$ still speaks about the amount of its gravitational interaction.
I have also a funny answer (slightly less correct) - based on recent Ethan Siegel's popular article: photon is converted into mass (or something) instantaneously. Since the photon travels by velocity $$c$$, it itself (because of special relativity) doesnt experience the time flow and its birth and death are (from his own point of view) instantaneous.