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Legos Don’t Stand a Chance Against Time Reversal

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_RE_5951 1703-81 Time-Reversing Acoustics- Legos March 30, 2017 Photography by Nate Edwards/BYU © BYU PHOTO 2016 All Rights Reserved photo@byu.edu (801)422-7322
Photo by Nate Edwards

A crowd of 29 stands still, positioned as lookouts in various directions. A chirp punctuates the silence before being replaced by a distinct buzz. The buzzing grows louder, then abruptly drops back into silence. Twenty-eight Lego figurines shift slightly — they survive. But one unlucky companion lies on his back, toppled by an invisible force.

The culprit of this miniature disaster? Targeted sound vibrations — also known as time reversal — courtesy of BYU physics professor Brian Anderson.

“Time reversal is really like ventriloquism,” Anderson said. “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.”

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