Prof Stephen Hawking
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Stephen Hawking misses 70th birthday celebrations

British scientist Stephen Hawking has had to miss a symposium to mark his 70th birthday because of ill health.

Prof Hawking was discharged from hospital only on Friday, vice-chancellor of Cambridge University, Prof Sir Leszek Borysiewicz, told the event.

A recorded speech was played to the symposium at the university, in which Prof Hawking, who was diagnosed with motor neurone disease aged 21, urged the continued exploration of space "for the future of humanity".

David Shukman reports.