>Tell that to a working scientist. Rest/invarient mass = mass. Moving mass is relativistic mass, and obsolete.
He says that "mass is mass". This doesn't take into account that actually two different masses have to be considered - the rest mass, and the mass while the object is moving. The statement that "mass is mass" is one guy's interpretation, with which I don't happen to agree.
The wikipedia, at
http://en.wikipedia.org/wiki/Special_relativity#Mass.2C_momentum.2C_and_energygives a summary of the relevant aspects of the Theory of Relativity. "It is often stated that in special relativity the mass of a body increases as its velocity increases. However, this statement depends on one's definition of mass, and in SR there are actually two different notions of mass."
In summary, the rest mass is invariant.
And the relativistic mass depends on the speed of an object. It is not invariant. This is one of the basic conclusions of the Special Theory of Relativity.
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)
