Deep Outerspace
Galaxies in deep space are seen in a 2005 handout photo from NASA. A giant hole in the Universe is devoid of galaxies, stars and even lacks dark matter, astronomers said on Thursday. REUTERS

Using single particles of light, scientists from the University of Queensland, Australia, have shown that a photon can pass through a wormhole to interact with its older self. The quantum experiment was aimed at simulation of time travel by quantum particles.

The Collective Evolution, citing the Nature Communications, which published the findings of the quantum experiment, says the difficulty in time travel lies in the existence of “closed timelike curves” (CTCs). A CTC refers to the line of a material particle in spacetime that is closed, enabling it to return to its starting point. The report says CTCs are used to simulate powerful gravitational fields of the kind produced by a spinning black hole. Based on Albert Einstein’s relativity theory, CTCs can theoretically warp or distort existence to bend space-time back on itself, enabling time travel.

The Scientific American says many physicists find the idea of CTCs “abhorrent, because any macroscopic object travelling through one would inevitably create paradoxes where cause and effect break down.”The Grandfather paradox (what happens if a person travels back into time and kills his grandfather?) is a commonly cited example of such a breakdown. However, in 1991, theorist David Deutsch came out with a model showing that CTC-related paradoxes in time travel could be avoided at the quantum level, or the level of the smallest possible unit of any physical property such as energy or matter. He attributed this to the behavior of fundamental particles, which, according to him, follow not the rules of strict determinism but of probability.

The latest experiment, simulating Deutsch’s CTC model, has been conducted by University of Queensland physicist Tim Ralph, along with his student Martin Ringbauer. He points out that though the theory of general relativity predicts strange paradoxes (apparent and logical contradictions) in time travel, such paradoxes seem to disappear when time travel is considered at the quantum level.

An increasing number of physicists agree that particles at the quantum level do not follow the rules of classical mechanics but behave in unexpected ways.

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