|MLA Citation:||Bloomfield, Louis A. "Question 589"|
How Everything Works 22 Apr 2018. 22 Apr 2018 <http://howeverythingworks.org/print1.php?QNum=589>.
A better way to deal with moving particles, particularly massless particles, is to incorporate momentum into the problem. The full equation, correct for any particle, is E2=m2c4+p2c2. In this equation, E is energy, m is the rest mass of the particle (if any), p is the momentum of the particle (if any), and c is the speed of light. While light has no rest mass, it does have momentum and it's this momentum that gives light an energy. Light travels along at the speed of light with a finite momentum and a finite energy. On the other hand, the momentum of a massive particle increases without limit as the particle approaches the speed of light and so does the particle's energy. Thus massive particles can't ever reach the speed of light.