British scientist Stephen Hawking was forced to miss a second celebration of his 70th birthday due to illness, organisers said late Thursday.
The physicist and cosmologist, who suffers from motor neurone disease, was due to attend a VIP reception at the Science Museum in London to honour his work and celebrate his birthday.
But he was not well enough to attend the event on Thursday, just as he missed a special debate held in his honour at Cambridge University earlier this month following a spell in hospital.
His daughter, Lucy Hawking, told the audience: "It's really sad that he can't be here this evening. He would have loved to have been here with you all."
Lucy Hawking accepted a special gift for her father from the Science Museum's inventor-in-residence, Mark Champkins, an illuminated model depicting spirals of light falling into a black hole entitled "black hole light."
The museum, which the scientist describes as "one of my favourite places," on Friday opened a new exhibition of his life and achievements.
It includes objects and papers from the professor's archives including notes, the annotated script for a 1999 guest appearance on "The Simpsons" and the blue suit he wore for a zero-gravity flight in 2007.
Hawking's fame moved beyond academia in 1988 with the publication of his book "A Brief History of Time" explaining the nature of the universe to non-scientists, which sold millions of copies worldwide.
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