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Re:Physicists Create Time-Reversed Waves of Optical Light by gmuslera on Thursday December 17, 2020 @09:44PM (#25463221)
Could this be used for making something perfectly black or something like that? There was an A.C.Clarke story about a silence machine that reemits the sound with a delay to cancel it.
Re:Physicists Create Time-Reversed Waves of Optical Light by _underfl0w_ on Friday December 18, 2020 @01:50AM (#25464515)
Not a physicist, but this might not work quite the same since light is both a particle and a wave, whereas sound is just a pressure wave on a given medium. Would happily be proven wrong though!

Seems like the cancelation happening in your scenario would likely be from a delay of half the period of the sound waves, effectively making them roughly "complementary" or "inverse". Can't say I'm familiar with the research, though.

On a sillier note, have you heard of the Speech Jammer? [0]

It's a device to disrupt a person's speech by playing it back to them with a delay of a few milliseconds. Hilarious results. Also easily reproducible at home if you're bored.

[0] https://phys.org/news/2012-09-speech-jammer-ig-nobel-winners...

Re:Physicists Create Time-Reversed Waves of Optical Light by tzs on Thursday December 17, 2020 @11:24PM (#25463853)
The story is “Silence Please” (1).

(1) https://en.wikipedia.org/wiki/Silence_Please

Re:Physicists Create Time-Reversed Waves of Optical Light by Throwaway1771 on Thursday December 17, 2020 @10:11PM (#25463378)
Re-emits the opposite sound?
Re:Physicists Create Time-Reversed Waves of Optical Light by foobarbecue on Thursday December 17, 2020 @10:32PM (#25463500)
Like noise - canceling headphones, presumably.
Re:Physicists Create Time-Reversed Waves of Optical Light by TheOtherHobbes on Friday December 18, 2020 @03:32AM (#25465062)
Exactly like noise cancelling headphones. Also like any number of industrial noise cancelling systems.