Modern Special Relativity and Mass

[DW]

Originally posted by Arcon
Mass is the source of a gravitational field in the same way the charge is the source of of an EM field.

Actually the analogy is closer to the four vector current being the source to the vector potential which is like the stress energy tensor being the source for the differential spacetime geometry. The comparison being compared are
A^\mu ;^\nu _\nu = \mu _{0}J^\mu
and
G^\mu ^\nu = kT^\mu ^\nu .

Originally posted by Stingray
You guys shouldn't be mixing special and general relativity. The stress-energy tensor is the source for gravity in GR ... The current 4-vector can be made one number in a certain frame (charge), so its reasonable to say that charge sources the EM field. The energy-momentum tensor cannot in general be reduced to a single number (mass density).

This point is in fact why I kept saying that the stress energy tensor, NOT either mass, was the source term for gravitation in relativity. So you shouldn't say "you guys" here.

Originally posted by Arcon
That is not always true.

So what you should be arguing is that like the stress energy tensor not mass is the source in gravitation, the four vector current not charge is the source in electromagnetism.