Does Light Really Have Mass or Not?

[Hypercase]

light light??

hi u guz.
heres a confusing question. does light have mass.
I have always belived so , but i received a confusing argument,:- light may be a wave particle and be effected by gravity, but that is becuz energy and mass are two forms of thesame thing. so light is the
form of a packet of energy rather than something that has mass.


So Plz help clear this confusion Does light have mass?
does a photon have mass?
If not then why is it affected by gravity?
Thanks in advance.

 

[suyver]

A photon (quantum of light) does not have mass.

Here is an identical question

 

[ZapperZ]

Originally posted by Hypercase
hi u guz.
heres a confusing question. does light have mass.
I have always belived so , but i received a confusing argument,:- light may be a wave particle and be effected by gravity, but that is becuz energy and mass are two forms of thesame thing. so light is the
form of a packet of energy rather than something that has mass.


So Plz help clear this confusion Does light have mass?
does a photon have mass?
If not then why is it affected by gravity?
Thanks in advance.

Y'know, we get so many of these questions repeatedly. I know we have an FAQ for this Physics Forums dealing with users and administrative stuff. How about a physics FAQ dealing with these common questions? (Or do we have one already and I'm too dumb to notice?) I know the USENET has a huge database of FAQ's. Maybe we should have something similar? It doesn't even have to contain anything other than a set of links to various websites that answer these questions satisfactorily.

... or maybe I'm just barking at the wrong tree by suggesting it on here? :)

Zz.