A large majority of Americans believe that in the year 2050 computers will be able to converse like human beings, cancer will be cured and artificial limbs will perform better than natural ones, according to a Pew Research Center poll based on a survey conducted in April and released Tuesday. The poll was conducted in conjunction with Smithsonian magazine for a special issue marking its 40th anniversary. But while Stanley Kubrick may have foreseen a future in "2001: A Space Odyssey" where a Pan American commercial craft carried civilians to the moon, only 53 percent believe that ordinary people will...