CAMBRIDGE, England -- Renowned physicist Stephen Hawking is not well enough to attend a conference held to celebrate his 70th birthday, a University of Cambridge official said Sunday.
Hawking's remarkable career is being honored as part of a daylong conference on cosmology being hosted at the university.But the celebrity scientist, who suffers from Lou Gehrig's disease, 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 specify the nature of Hawking's condition, although he said he believed Hawking would be well enough to meet some of the attendees over the next week.
Hawking is wheelchair bound and dependent on a computerized voice system for communication.
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 was diagnosed with Lou Gehrig's disease - known as motor neurone disease in the U.K. - when 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.
An expert on black holes, Hawking also gained wide acclaim for popularizing astronomy in best-selling books such as "A Brief History of Time" and "The Universe in a Nutshell."
Other speakers scheduled for Sunday include Astronomer Royal Martin Rees, Nobel Prize-winning physicist Saul Perlmutter, and Hawking's longtime collaborator Kip Thorne. Among the topics due to be discussed are supernovae, black holes, and dark matter.
View a slideshow of some of Hawking's most memorable lines below.
People who boast about their IQ are losers.
My goal is simple. It is a complete understanding of the universe, why it is as it is and why it exists at all.
I don't think the human race will survive the next thousand years, unless we spread into space. There are too many accidents that can befall life on a single planet. But I'm an optimist. We will reach out to the stars.
I think computer viruses should count as life ... I think it says something about human nature that the only form of life we have created so far is purely destructive. We've created life in our own image.
We are so insignificant that I can't believe the whole universe exists for our benefit. That would be like saying that you would disappear if I closed my eyes.
We are just an advanced breed of monkeys on a minor planet of a very average star. But we can understand the Universe. That makes us something very special.
What I have done is to show that it is possible for the way the universe began to be determined by the laws of science. In that case, it would not be necessary to appeal to God to decide how the universe began. This doesn't prove that there is no God, only that God is not necessary.