They picked the perfect "host" to play Robert Porter ... by demeanor and namesake.
Dr. Mark Powell: What if I were to tell you that according to a man who lived on our planet, named Einstein, that nothing can travel faster than the speed of light?
Prot: I would say that you misread Einstein, Dr. Powell. May I call you Mark? You see Mark, what Einstein actually said was that nothing can accelerate to the speed of light because its mass would become infinite. Einstein said nothing about entities already traveling at the speed of light or faster.