This is especially so, now that scientists from the University of Queensland, Australia have reportedly sent particles of light into the past.
Scientific American reports that the researchers used single particles of light (photons) to simulate quantum particles traveling through time. They have, in effect, shown that one photon can pass through a wormhole and then interact with its older self.
Their findings were published in Nature Communications.
“Closed timelike curves” (CTC) are the source of the time travel conundrum. CTCs are used to simulate extremely powerful gravitational fields, like the ones produced by a spinning black hole. Theoretically, they could (based on Einstein’s theory of general relativity), warp the fabric of existence so that spacetime bends back on itself – thus creating a CTC, almost like a path that could be used to travel back in time.
Many physicists reportedly find CTCs “abhorrent, because any macroscopic object traveling through one would inevitably create paradoxes where cause and effect break down.” But others disagree with this assessment.
In 1991, physicist David Deutsch showed that these paradoxes (created by CTCs) could be avoided at the quantum scale because of the weird behavior of these fundamental particles that make up “matter”. At the quantum scale, these particles do not follow the rules that govern classical mechanics but behave in strange and unexpected ways that really shouldn’t even be possible, reports Collective Evolution.
For the experiment, physicist Tim Ralph and his PhD student Martin Ringbauer simulated a Deutsch’s model of CTCs, “testing and confirming many aspects of the two-decades-old theory.” Scientific American reports that although the experiment is just a mathematical simulation, the researchers (and their team/colleagues) emphasize that their model is mathematically equivalent to a single photon traveling through a CTC.
By measuring the polarization states of the second photon after its interaction with the first, across multiple trials the team successfully demonstrated Deutsch’s self-consistency in action.
“The state we got at our output, the second photon at the simulated exit of the CTC, was the same as that of our input, the first encoded photon at the CTC entrance,” Ralph says. “Of course, we’re not really sending anything back in time but [the simulation] allows us to study weird evolutions normally not allowed in quantum mechanics.”
In order to send something back in time, scientists would have to find a real CTC, which has yet to happen as far as we know.
Consider the ‘grandfather paradox’ to wrap your head around what’s being presented. In the hypothetical scenario, someone uses a CTC to travel back through time to cause harm to their grandfather, thus preventing their later birth. Now, imagine a particle going back in time to flip a switch on the particle-generating machine that created it – this is a possibility that these physicists say they have shown through their simulation.
You can read the specifics of the experiment here.
This particular experiment illustrates how what happens in the present can change what happened in the past. It also shows how time can go backward, how cause and effect can be reversed, and how the future caused the past.
If we attempt to attribute an objective meaning to the quantum state of a single system, curious paradoxes appear: quantum effects mimic not only instantaneous action-at-a-distance, but also, as seen here, influence of future actions on past events, even after these events have been irrevocably recorded. – Asher Peres, pioneer in quantum information theory (source)(source)(source)
Perhaps one day, a wormhole, or a CTC in space, will be discovered, allowing scientists to conduct actual experiments that go beyond this theory.
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