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Mercury + Sound = Kooky Mad Science Party

Now let's watch what happens when you take a blob of mercury and subject it to different audio frequencies. Spoiler alert: the mercury forms geometric shapes and appears to dance. This is slow-motion footage (with music added, not the tones the mercury is reacting to -- we'll get to those original tones in a moment):

Okay, so what happened there?! I spoke to photographer Nick Moore about how this was filmed. (My suspicion was that he might be building a T-1000.) He wrote:

The mercury is sitting in a concave plastic lens from an old projection TV (it was convenient), the lens is stuck to a 12inch speaker using Silly Putty to stop it from rattling around or bouncing.

The tone is a pure sine from an old signal generator (1960s) I believe it was between 10Hz and 120Hz. The higher the frequency the more nodes (bumps) appear on the mercury. They are actually 3 dimensional standing waves.

And here's the video in regular speed, with the original tones, so you can see how crazy this really is:

This phenomenon is part of a discipline called cymatics, the study of visible sound and vibration. According to Wikipedia, observations of these kinds of effects date back to Galileo and Hooke, among many others.

See also: Cymatics: Making Sound Visible, 600-Year-Old Music Found Encoded in Chapel Walls, and Burning Matches in Slo-Mo. I also recommend checking out Moore's YouTube channel for tons of great stuff like this.

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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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