Quantum gravity's tangled time

phys.org | 8/17/2018 | Staff
maddyb7 (Posted by) Level 3
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The theories of quantum mechanics and gravity are notorious for being incompatible, despite the efforts of scores of physicists over the past fifty years. However, recently an international team of researchers led by physicists from the University of Vienna, the Austrian Academy of Sciences as well as the University of Queensland (AUS) and the Stevens Institute of Technology (U.S.) have combined the key elements of the two theories describing the flow of time and discovered that temporal order between events can exhibit genuine quantum features.

According to general relativity, the presence of a massive object slows down the flow of time. This means that a clock placed close to a massive object will run slower as compared to an identical one that is further away.

Rules - Quantum - Theory - Allow - Object

However, the rules of quantum theory allow for any object to be prepared in a superposition state. A superposition state of two locations is different to placing an object in one or the other location randomly—it is another way for an object to exist, allowed by the laws of quantum physics.

One of the open questions in physics is: What happens when an object massive enough to influence the flow of time is placed in a quantum superposition state?

Topic - Physicists - Scenarios - Mechanism - Superposition

This is a controversial topic: some physicists claim that such scenarios are fundamentally impossible—some new mechanism must block the superposition from forming in the first place—while others develop entire theories based on the assumption that this is possible.

"We started by tackling a question: what would a clock measure if it was influenced by a massive object in a quantum superposition state?" explains Magdalena Zych from the University of Queensland.

Scientists - Roadblocks - Scenario - Textbook - Physics

The scientists were expecting to face the roadblocks making the scenario impossible, but surprisingly, using standard textbook physics they were able to exactly describe what happens.

They so discovered that when a massive...
(Excerpt) Read more at: phys.org
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