Has Stephen Hawking been replaced with a 'puppet'?

Professor Stephen Hawking is one of the world's most well-known scientists and has had his life story told in books, documentaries, and Oscar-winning dramas. But conspiracy theorists claim we hardly know anything about the award-winning physicist, who celebrated his 76th birthday on Monday. For there are certain corners of the internet where people are convinced that the real Professor Hawking died decades ago and that in the intervening years the political and scientific elite have installed a lookalike to act in his place. Some of those who believe he has been supplanted think Professor Hawking, Director of Research at the Centre for Theoretical Cosmology within the University of Cambridge, died in 1985 - three years before the publication of his best-selling book A Brief History of Time. The idea might seem outlandish, but conspiracy theorists have outlined six signs that they claim clearly support their idea, ranging from the way he looks to the complexity of his theories.