Art Unwin wrote:
I would have no problem of accepting the presence of photons but the
link you gave me stated that it had zero mass.

If they didn't say zero *rest* mass, they should have.
A particle with zero rest mass cannot ever travel at
the speed of light as its mass would increase without
limit. Photons do travel at the speed of light but
are known to possess energy and momentum which is
equivalent to mass related by e=mc^2.
--
73, Cecil http://www.w5dxp.com