› added 9 years ago

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TIL that sound cancelling headphones work by making a sound exactly 180 degrees out of phase with any unwanted noise. The sound-wave that it sends out interferes with that of the original sound. The two sound-waves cancel each other out and create silence.

Read more electronics.howstuffworks.com

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JnyB TIL Cats are the most popular pets in the world and that 1 out of every 3 American households have one.
xV9PB TIL that Purgatory in the Divine Comedy (1320) is a mountain situated on the opposite end of the world to Jerusalem, and Dante and Virgil reach it by going to the centre of the Earth (via Hell) and up the other side. This is because the Medieval world, and hence Dante, knew the Earth was a sphere.
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