A team of physicists has uncovered a surprising new way to explore one of science's greatest challenges: uniting the two fundamental theories that explain how our universe works—Einstein's theory of gravity and quantum mechanics.
Despite decades of effort, no one has fully explained how gravity—which governs massive objects like planets and stars—fits with quantum mechanics, which describes the behavior of the tiniest particles in the universe. But now, scientists believe light may hold the key.
Warner A. Miller, Ph.D., co-author and a professor in the Department of Physics at Florida Atlantic University's Charles E. Schmidt College of Science in collaboration with scientists at the University of Seoul and Seoul National University, South Korea, found that light's polarization—the direction it vibrates as it travels—can behave in an unexpected way when passing through curved space. Normally, this polarization shifts slightly due to the warping of space by gravity, a well-known effect.
But the team discovered something deeper: by carefully choosing how the light is measured, they could trigger a strange effect called non-reciprocity. Findings from their study were published in Scientific Reports.
"Non-reciprocity means that light behaves differently when it moves forward compared to when it goes backward," said Miller. "In other words, it doesn't 'undo' its twist, even if it retraces its path. This challenges the conventional belief that light always returns to its original state after traveling a closed loop, especially if its path is influenced only by gravity."
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