Appearing as a hovering, wraith-like vision above the Cornell University Physics Building where he taught for years, the ghost of recently deceased astronomer/author Carl Sagan warned former colleagues Monday against a belief in superstition. 'Exercise skepticism!' Sagan said, clanking a large metal chain. 'Whenever possible, there must be independent confirmation of all facts pertaining to any so-called 'magical' or 'mystical' event or phenomenon!' Added Sagan: 'One should always encourage vigorous debate on the nature of rational inquiry and empirical evidence. A thinking person must always utilize the scientific method, or wear the chains of superstition throughout eternity!' Cornell physics department head Arthur Ludyvik said that he would heed Sagan's warning and buy a special anti-superstition crystal amulet and incense cone. 