Re: Increasing Mass of Particles

[DSCHROEDER@cc.weber.edu]

> Feel free to correct my naive response - but in less rarified contexts,
> a current is a time-related value, and charge is time invariant?
>
> Whatcott

The charge density (rho) and the three components of the current
density (j_x, j_y, and j_z) together form a four-component object
called the four-vector current density.  This object is a four-
vector in the same sense that energy and momentum (E,p_x,p_y,p_z)
form a four-vector:  the components mix with each other under
Lorentz transformations in the same way as (dt,dx,dy,dz).
The first component of any four-vector is called the "time 
component".  See, for instance, chapter 10 of Griffiths E+M.

Hope this helps,

Dan