Computer solves a major time travel problem

Posted by K R on

It is more than 120 years since H.G. Wells published The Time Machine, the novel that was to popularise the concept of time travel and lead to myriad stories on the theme. But it is only now that we have finally developed a plotline for time travel that makes logical sense – and it has been penned by a machine. The breakthrough involves the grandfather paradox – that favourite plaything of philosophers where somebody travels into the past and kills their own grandfather, preventing the existence of one of their parents, and therefore their own. But the problem is, if the protagonist doesn’t exist, then how could they go back in time to set off the chain of events in the first place? The paradox is often extended, in various guises, to regard any action that alters the past – such as Marty McFly avoiding the amorous attention of his mother, Lorraine, and ensuring she marries his father, George, in Back to the Future. Meanwhile, physicists such as Stephen Hawking use the impossibility of such causal chains (called, in physics-speak, “closed time-like curves”) to argue that travel into the past must be impossible. There has, of course, always been the possible solution that invokes the “many worlds” interpretation of quantum mechanics. That says that when you travel back in time you end up in an alternate universe, so any damage you might wreak affects that universe only, not the one you were born in. That solution works, but it requires the existence of many alternate universes and for your time machine to double as a universe hopper. Resolving the paradox with just one universe has proved trickier. Now, Doron Friedman, a computer scientist at the Interdisciplinary Center in Herzliya, Israel, has employed automated reasoning to tackle the problem, with his work published on the arXiv (meaning it is yet to go under peer-review). Read More: Cosmos

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