CAMBRIDGE, England — Renowned physicist Stephen Hawking was too ill to attend a conference in honor of his 70th birthday Sunday, but in a recorded message played to attendees he repeated his call for humans to colonize other worlds.
University of Cambridge vice chancellor Leszek Borysiewicz told the conference that Hawking, who is almost completely paralyzed because of Lou Gehrig's disease, had only recently been discharged from the hospital for an unspecified ailment.
"Unfortunately his recovery has not been fast enough for him to be able to be here," Borysiewicz said.
In his recorded speech, Hawking pleaded for interplanetary travel, arguing that humans faced a grim future unless they spread out from their terrestrial home. "I don't think we will survive another thousand years without escaping beyond our fragile planet," he said.