I've heard so much debate on wether the speed of light is constant or not. So I just had to post this.
http://www.newscientist.com/news/news.jsp?id=ns99992650
http://aca.mq.edu.au/lightspeed.html
http://www.newscientist.com/news/news.jsp?id=ns99992650
http://aca.mq.edu.au/lightspeed.html