Another good question: Upon what authority did the Catholic Church change the Sabbath to Sunday?
One answer comes from a book for which the author received a gold medal from the pope for his scholarship:
From Sabbath to Sunday: A Historical Investigation of the Rise of Sunday Observance in Early Christianity by Samuele Bacchiocchi
see:
http://www.amazon.com/From-Sabbath-Sunday-Investigation-Christianity/dp/9998203945
That and a buck might get him a cup of coffee...