23. Theoretical physicists often assert that at the extremely high energies thought to have existed in the first moments of the universe, the W particle (known to have a mass several hundred times that of the proton)

would behave, mass-wise, similarly to the (massless)

photon. Explain this apparently contradictory statement. [Hint: Check Chapter 26 and the relativistic relationships between rest energy, kinetic energy, and total energy.]