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Stephen Hawking seems to have turned into the man with the sandwich board that says: "The end is nigh."

Not only has he warned us that aliens might destroy us, but he's also been worrying that artificial intelligence might do the same.

Now he's perceiving a threat that might not merely put an end to Earth, but to the whole Universe.

As the UK's Sunday Times reports, Hawking is worried about the God particle. This, discovered by physicists during experiments within CERN's Large Hadron Collider, is a vital ingredient to explaining why things in our world have mass.

However, in a preface to a new book called "Starmus" -- a collection of lectures given by famous scientists and astronomers -- Hawking worried that the Higgs Boson might become unstable.

He wrote: "The Higgs potential has the worrisome feature that it might become metastable at energies above 100bn gigaelectronvolts (GeV)."

What might this lead to? Hawkins explained: "This could mean that the universe could undergo catastrophic vacuum decay, with a bubble of the true vacuum expanding at the speed of light. This could happen at any time and we wouldn't see it coming."

Before you prepare your loved ones for an evacuation to some distant star, Hawking did offer some hope with, it seems, a wry smile: "A particle accelerator that reaches 100bn GeV would be larger than Earth, and is unlikely to be funded in the present economic climate."

In essence, then, his fears might be theoretically valid, but their likelihood of actually coming to pass is somewhat smaller than that of the New York Jets winning the next Super Bowl.

Still, you have to wonder about Hawking's relationship with the Higgs Boson discovery. First, there's the fact that he lost a $100 bet over its unearthing. Then he mused last year that now the Higgs Boson had been identified, physics has become less interesting.

However, given that he believes we only have perhaps 1,000 years left on Earth anyway, it's as well to explore every possible scenario, before the robots and algorithms secure minds of their own and, as their first step, eliminate us all.