Dr. Fred Whipple, director of The Smithsonian Astrophysical Observatory, at Cambridge, Mass., explains the flight of the small artificial moon launched by Russia, in this Oct. 5, 1957 file photo. Efforts to trace the satellite by the U.S. were centered at the observatory under direction of Dr. Whipple. Whipple, a pioneer in astronomy who proposed the 'dirty snowball' theory for the substance of comets, died Monday Aug. 30, 2004. He was 97. (AP Photo/File)
