Nothingness

[pocaracas]

Page 23 The Mass of the Classical Vacuum
By: R. Penrose
Think now of Maxwell’s electromagnetic field. As Maxwell himself clearly pointed out (1865, 1873), this fieldcarriesenergy. Thus, by E=MC2, the field must also have mass. Thus, Maxwell’s field is also matter! ----- If there are many continuous media present (e.g. quantum field descriptions of particles), then we have an energy density, and hence a corresponding tensor, for each one.

Had to stop reading here....
E = mc^2
That 'm' in the formula is a very special 'm'.
It is the relativistic mass, which can be written as:
m = m0 / sqrt(1 - v^2/c^2)

and m0 is the mass at rest, v is the present velocity of said mass and c is the speed of light in vacuum.
When v = c, as is the case of an electromagnetic wave, you get something nasty....m = m0 / 0 -> ∞

So saying that light has mass is just showing that you don't understand the basics of special relativity.