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A Mathemusician Explains How Sound Works

Self-proclaimed "recreational mathemusician" Vi Hart has posted an excellent short film explaining the science and mathematics of sound, frequency, and pitch. Basically Hart shows us how the chromatic scale was originally measured, how musical instruments work, and how we hear sound. It's playful and smart -- exactly what you need to watch right now if you have even the vaguest geeky interest in music, math, or sound.

Sample lines (shown as speech bubbles on a map, when describing how some cultures independently created similar systems of tonality):

Africa: "So a note and the note with twice the frequency...totally are like the same note, am I right?"

Germany (ish): "Oh man, octaves! Love 'em."

Madagascar: "Yeah!"

Peru: "OMG me too!"

USA (Motown): "Yo what about 5ths?"

USA (rest of country): "I like 5ths."

UK: "The ones with the 1:3 ratio?"

South Africa: "Yeah, I could go for those."

Hart also notes in her YouTube description a minor narration error. I thought I'd note it here before we got complaints:

Correction: it is the "Basilar" membrane, which is what I say, but somehow between recording the script and actually drawing the stuff I got confused and thought I just pronounced my Vs poorly. Always sad to have such a simple and glaring error in something I put hundreds of hours of work into, but a "Vasilar" membrane can be the kind that a Vi draws to explain Viola Vibrations, I guess! Making up new words is just so prolightfully awstastic.

If you like this, you'll love Hart's blog. She also takes donations to help fund her work, and publishes what I assume is a Google Voice phone number where you can send her text messages or voicemails.

(Via Laughing Squid.)

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Belly Flop Physics 101: The Science Behind the Sting
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Belly flops are the least-dignified—yet most painful—way of making a serious splash at the pool. Rarely do they result in serious physical injury, but if you’re wondering why an elegant swan dive feels better for your body than falling stomach-first into the water, you can learn the laws of physics that turn your soft torso a tender pink by watching the SciShow’s video below.

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What's the Saltiest Water in the World?
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Saltwater is common around the world—indeed, salty oceans cover more than two-thirds of the globe. Typical saltwater found in our oceans is about 3.5% salt by weight. But in some areas, we find naturally occurring saltwater that's far saltier. The saltiest water yet discovered is more than 12 times saltier than typical seawater.

Gaet’ale is a pond in Ethiopia which currently holds the record as the most saline water body on Earth. The water in that pond is 43.3% dissolved solids by weight—most of that being salt. This kind of water is called hypersaline for its extreme salt concentration.

In the video below, Professor Martyn Poliakoff explains this natural phenomenon—why it's so salty, how the temperature of the pond affects its salinity, and even why this particular saltwater has a yellow tint. Enjoy:

For the paper Poliakoff describes, check out this abstract.

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