My biology professor keeps talking about how the speed of light is no longer considered a constant. Anyway, he went on to quote how scientists have stopped a beam of light using magnetic fields. I've read a few popular science articles in the magazine New Scientists but found nothing that would indicate a violation of relativity or even one using magnetic fields. He also stated that the speed of light is changing over time. He used an example regarding how the sun will eventually run out of energy & between that time the speed of light will slow down as a result. So... Can anyone point me in the right direction of information on the stopping light with magnetic fields? (if there really were/are any) Does anyone know of any articles regarding the slowing of the speed of light? Overall, I understand a biology professor is not a physics professor but he keeps using various examples as if they were facts. Often stating "we once though the speed of light was a constant."