Researchers Use Legos to Demonstrate Time Reversal Experiments

All in the name of science

Using Legos and lasers to study acoustics; BYU physicist demonstrates time reversal
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Legos are pretty resilient. Neither repeated stomps nor multiple trips through the vacuum really affect the plastic bricks or their squat companions. But, as new research out of Brigham Young University shows, they don’t hold up too well against time reversal. “Time reversal” doesn’t have anything to do with time travel. It refers to reversed sound waves, which, when focused on an object such as a Lego, knocks it the hell over.

The below demonstration, included in the online version of the Journal of the Acoustical Society of America, features physics professor Brian Anderson and his 28 Lego men. Anderson and his team played a sound and recorded the waves bouncing back from a targeted location. This allowed them to send out reversed sound “aimed” at that location. Then when the sound hit the Lego man, it was man down.

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“Time reversal is really like ventriloquism,” Anderson explained in the press release.”But instead of throwing our voice to another place, we’re focusing vibrations at a target location that may be far from where the vibrations originated.”

Researchers didn’t just conduct this experiment to be adorable. They were testing time reversal to see how these targeted sound vibrations can help medical technology, nuclear waste management, underwater submarine location, better noise canceling headphones, and many other things. And if that’s not an excuse to play with Legos at work, not much else is.

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