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Take a Summer Time Trip

iStockphoto / mstay

iStockphoto / mstay

By Guy Micklethwait

Backwards time travel, parallel universes and temporal paradoxes – take a ride with the best time travel movies.

Filmmakers have been using ideas about time travel as plot devices for many years. These films speculate about the physics and philosophy of time travel, including parallel worlds and the consequences of temporal paradoxes. Here are five highly recommended time-bending movies to while away those long hot summer days and nights when time slows down.

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In a causal loop, information that comes back from the future can trigger changes that end up causing the predicted event to take place. There are several examples of this in the sci-fi mystery thriller Twelve Monkeys (1995). Scientists use a time machine to send James back from the year 2035 to 1996 to gain a sample of a virus in its pure form. Each time he returns from the past, nothing has changed in his world; however, each of his trips to the past creates a “change” to the timeline that inadvertently creates his future.

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In 1961 Edward Lorenz created a simple weather forecasting model and noticed that the slightest change in his input data would give very different long-term weather predictions. He later commented that the flap of a butterfly’s wing could cause a tornado in some other part of the planet, and thus the term the “Butterfly Effect” was born. In the psychological thriller The Butterfly Effect (2004), Evan learns to travel back in time to his childhood and make small but significant changes. Each time he returns to his adult life, he and all of his friends are following a completely different destiny.

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If you went back in time and killed your grandfather when he was a child, this means that you would never have been born and would therefore cease to exist. This is known as the “Grandfather Paradox” and occurs in the sci-fi adventure Back to the Future (1980). Marty goes back in a time machine and meets his parents before they were married, but his presence causes his mother to fall in love with him and reject his father. Marty fears this will prevent his birth, so spends the rest of the film trying to get his parents back together again. Unlike Evan, Marty is trying to prevent the future from being changed.

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In his Many Worlds Interpretation of Quantum Physics, theoretical physicist Hugh Everett III suggested in 1955 that when we measure quantum objects, the world actually splits into two parallel realities. Nowadays, many scientists believe that if we were to travel back in time and make a small change, a new timeline would be created in parallel to the unchanged original, thus avoiding the consequences of the Grandfather Paradox. The romantic drama Sliding Doors (1998) follows the fortunes of Helen in two different parallel timelines that are caused by a brief time reversal at the start of the movie.

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In the mid-1980s Dr Igor Novikov developed the Novikov Self-Consistency Conjecture, which stated that if time travel was possible there must be a law of physics that would prevent time travellers from doing any action that would cause an inconsistent timeline and hence a paradox. This is exactly what happens in the sci-fi action thriller Terminator 3: Rise of the Machines (2003). No matter what the protagonists do, or whom they kill, they can’t stop the inevitable war against the machines, which has to take place or else the robots would never have been sent back in time. This allows for a self-consistent timeline.

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Why are time travel films so popular? Maybe it is because they inspire their audiences to dream about one day being able to venture back and change their past, just as people once dreamed of taking a rocket to the Moon. As we move into the era of space tourism, who can say if and when backwards time travel will be possible?

Guy Micklethwait recently completed his PhD thesis, Models of Time Travel: A Comparative Study, using films at the Australian National University.