To Henri,

Indirectly that is exactly what I am saying; that light travels at c in
relation to other light it meets (which in turn is travelling at c in any
given electromagnetic field of reference).

That is to say, light travels at c in relation to the earth when measured on
earth.  However if another planet collided with the earth, which caused the
earth to travel away from the sun at high speed, light would still be
travelling at c in relation to the earth but no longer at c in relation to
the sun.  Of course light in the vicinity of the sun would still be
travelling at c in relation to the sun.

It takes courage to think for yourself, in spite of what other people
proclaim to be the truth.  As I said before, science is based on logic not
on faith.

Len.