Cambridge: Renowned physicist Stephen Hawking was not well enough to attend a conference in honor of his 70th birthday, a University of Cambridge official said on Sunday.
Hawking's remarkable career is being honored as part of a day-long conference on cosmology being hosted at the university, but the celebrity scientist will not be in attendance, according to Vice chancellor Leszek Borysiewicz.
Borysiewicz told conference attendees that Hawking was released from hospital on Friday and that "unfortunately his recovery has not been fast enough for him to be able to be here."
He didn't say when Hawking was hospitalized or specify the nature of his condition, although he did say that Hawking would be well enough to meet some of the attendees over the next week.
Hawking has had Lou Gehrig's disease - an incurable degenerative disorder known as motor neurone disease in the UK - since he was 21.
Most people die within a few years of the diagnosis, but Hawking has defied the odds and gone on to revolutionize the field of theoretical astrophysics and become one of the best-known scientists since Albert Einstein.
The condition has left him almost completely paralyzed and in a wheelchair since 1970. He now communicates only by twitching his right cheek. Since catching pneumonia in 1985, he has needed around-the-clock care and relies on a computer and voice synthesizer to speak. His fragile health has forced him to cancel appearances in the past.
Borysiewicz said he hoped that Hawking would follow the proceedings via videolink.
"If you're listening Stephen, happy birthday from all of us here today," Borysiewicz said to a round of applause.
Hawking's celebrity status was evident on Sunday at Cambridge's Lady Mitchell Hall, where hundreds crowded into the auditorium to hear prominent researchers outline the latest developments in cosmology.
Outside the venue, three teenage students - self-described "groupies" - waited for a chance to catch a glimpse of the eminent scientist.
"It's a once-in-a-lifetime thing," said 18-year-old Marianna Sykopetritou, a Cambridge engineering student who said she was on the long waiting list to attend the event?
Borysiewicz said that Hawking had "transformed our understanding of space and time, black holes, and the origins of the universe," adding that his success in the face of adversity was a "beacon of hope and encouragement for those in difficulty everywhere."
Hawking is also known for his work popularizing the field of theoretical astrophysics in a series of best-selling books such as "A Brief History of Time" and "The Universe in a Nutshell."
Astronomer Royal Martin Rees and Nobel Prize-winning physicist Saul Perlmutter were among the scientists who addressed the crowd on the current understanding of the universe. A recorded message from Hawking was due to be played later.