Why can’t a charged particle accelerate to the speed of light?

Question: Why can't a charged particle accelerate to the speed of light?
- Keywords:
  accelerate,
  charge,
  light,
  particle,
  speed
Asked by charlie13 to David, Luna, Probash on 25 Mar 2011 in Categories: General.
- David Pyle answered on 25 Mar 2011:
  
  A charged particle could, in principle, travel at the speed of light. What is not possible is for a particle with mass to accelerate to the speed of light. The explanation is a little complicated, but comes from Einstein’s theories about the way that mass appears to change at speeds close to the speed of light.

Question: Why can't a charged particle accelerate to the speed of light?