i read an article on bbc where they said scientists froze a photon for about 10-20 microseconds. Doesn't this contradict einstein's theory that photon has no mas because if you are able to stop a photon, then it should have some type of rest mass and if it has rest mass, then it can't possibly achieve the "speed of light". Please correct me if i am wrong. And also, if light can be slowed down to a speed of bullet, then how can you call light a constant and how can we rely on light to tell us distances in space since it can slowed down drastically.Sorry if it's a bit long.
Article: http://news.bbc.co.uk/2/hi/science/nature/3308109.stm
http://www.livescience.com/php/video/player.php?video_id=itm1005_freezinglight