On Feb 20, 11:53 pm, Jeff$B"%(BRelf wrote:
I think my " Stupid " question would be best answered by Peter Brown,
not Google. Petedoes not approve of your attitude, Gisse.

Hi Jeff

I assume that you're referring to this question

Did Einstein say a photon has proper mass ?

I don't recall him saying it verbatim but I believe that he would say,
if asked, that a photon has zero proper mass and mass due to its
energy given by M = E/c^2. In fact Einstein was refering to the mass
of light once when he wrote the comment "A beam of light carries
energy and energy has mass."

If so, where ? Did he venture to guess what it was ?

You can't expect to look for modern terminology in days when the
didn't use this modern terminology. If I come across a place where
Einstein indicates that light has zero rest mass (aka proper mass)
then I'll let you know.

Pete