>Its not a matter of semantics per se, its a matter of mathematical definitions. The mathematical defintiion of mass does not change with velocity.
Sure.
I have catched up on my reading, and it seems that, indeed, the terms "rest mass" and "relativistic mass" are no longer very popular.
But the fact remains that the relativistic mass increases with speed, and whether you call it relativistic mass or energy, this is what will interact gravitationally with other objects.
The article at
http://math.ucr.edu/home/baez/physics/Relativity/SR/light_mass.html , while explaining that (according to modern terminology) a photon "has no mass", it does have a gravitation attraction (small, because the - er - energy of a photon is usually insignificant). See especially the last paragraph.
Difference in opinions hath cost many millions of lives: for instance, whether flesh be bread, or bread be flesh; whether whistling be a vice or a virtue; whether it be better to kiss a post, or throw it into the fire... (from Gulliver's Travels)
