Stephen Hawking cancels lectures over ill health
Celebrated physicist Professor Stephen Hawking has been forced to cancel a number of public engagements because of ill health, his university has confirmed.
They include this year's prestigious Reith Lectures, which have been postponed by the BBC.
A spokeswoman for Cambridge University, where the 73-year-old cosmologist is director of research in the Department of Applied Mathematics and Theoretical Physics, said: "Prof Hawking is not very well and a few public appearances have had to be cancelled."
She could not say anything more about the condition of the professor, who is thought to be the longest living survivor of motor neurone disease.
Prof Hawking had been due to record the Reith lectures at the Royal Institution in London on Thursday evening. They were due to be broadcast on BBC Radio 4, starting on Tuesday November 24.
In his talks, the professor planned to describe the nature of black holes and answer questions from BBC Radio 4 listeners.
A BBC spokesman said: " Unfortunately, Thursday's recording of the BBC Reith Lectures with Professor Stephen Hawking is no longer going ahead as he is unwell.
"We are postponing the broadcast of the lectures on Radio 4 and are liaising with Professor Hawking and his team about the next steps once he is better."
Prof Hawking had earlier said he hoped his lectures would "encourage people to imagine and explore the possibilities of science - both the known and the as-yet unknown".
In a statement released by the BBC, he said he intended to describe the "remarkable properties" of black holes, "including the fact that very small black holes aren't black at all, but glow like hot bodies".
He added: " We should never stop trying to tell these extraordinary stories from science and I hope my Reith lecture will enthuse a new generation to develop ideas that will have an impact on our understanding of the world and never to be overwhelmed by the task of discovery."
Although unwell, the state of the professor's health is not understood to be a serious cause for concern.
Prof Hawking, who rose to fame in 1988 with the publication of his best-selling book A Brief History of Time, was diagnosed with incurable motor neurone disease at Oxford University when he was just 21.
He was given only two years to live but defied the odds and is now believed to be the longest-living survivor of the condition, which destroys the nerves that affect movement but does not impair the brain.
The disease robbed Prof Hawking of movement and an operation to save his life ended his ability to speak naturally.
His computerised speech synthesiser - controlled by cheek movements - has given him one of the most instantaneously recognisable voices in the world.