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<DIV><FONT color=#000080 size=2 face=Arial>Dear All,</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>[Notably Chandra &
Chip],</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial></FONT> </DIV>
<DIV><FONT color=#000080 size=2 face=Arial>I'm having a bit of a problem over
this question of: 'How does a photon carry momentum'? (or similar
words.)</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>It seems to me that in order to even
beginning to address this question, one needs a clear definition of 'momentum'
that's applicable to the momentum carried by a photon.</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>I may be looking in the wrong places
(if so please advise), but the only definitions of momentum that I can find
either refer to 'mass' or refer to some other phenomenon which in turn refers to
momentum - i.e. circular references.</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>If I'm going to figure, or be
persuaded, how a photon carries momentum I first need to know what momentum IS
in respect of a photon (yes, I know it's E/c, that's a measure it's not a
definition).</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>Of course I'm aware of the paper
"Light is heavy", but I don't feel it's appropriate just to extract from
that some sort of mass-equivalence of a photon. If we do, we get the
result that 'm'=E/c^2, so 'm'c = E/c - gives the right result, but appears to be
some sort of convoluted self-confirmation (i.e. a circular argument dressed up
in fancy clothes). It certainly doesn't DEFINE a photon's momentum, just
evaluates it.</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial></FONT> </DIV>
<DIV><FONT color=#000080 size=2 face=Arial>Does anyone have a convincing
definition of momentum that's applicable to a photon? One that can be used
as a firm basis for theorising?</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>(I'd be glad if colleagues
didn't use this as an excuse to yet again present their own personal
theory/model - I'm looking for a definition that would be agreed by all, or at
least most, physicists.)</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial></FONT> </DIV>
<DIV><FONT color=#000080 size=2 face=Arial>Thanks in anticipation,</FONT></DIV>
<DIV><FONT color=#000080 size=2 face=Arial>Grahame</FONT></DIV></BODY></HTML>