# Mathematician Calculates Rotational Speed of Fidget Spinner in Fidgets Per Second

iStock // fullempty

How fast does a fidget spinner spin? It's a simple question with a simple answer, but a complex path to that answer. The issue lies in analyzing an extremely fast-moving object with simple tools, like a smartphone.

In the video below, mathematician Matt Parker turns to a spectrogram sound-analyzing app to solve this problem. Spectrograms are visual representations of sound, allowing the viewer to pick out certain frequencies within an audio clip and measure their intensity. By figuring out the sound the fidget spinner makes, Parker can sort out how many Hertz (cycles per second) the spinner is rotating at.

The first task is making the spinner itself stable, so it's easy to spin and becomes a reliable target for audio recording. Parker attaches the device to a drinking glass, and mounts the smartphone above it, with the microphone pointed at the edge of the spinner. Then by blowing the fidget spinner with compressed air, the mathemagic happens.

Parker calculates the absolute speed of the tips of the fidget spinner, as well as the speed of the spinner in revolutions per minute—the latter is roughly 3750 rpm! (For comparison, a typical car engine runs around 2000-3000 rpm when cruising.) The video is full of further analysis and methodology.

Tune in for some delightful applied mathematics...and be sure to wear your safety gear!

Incidentally, Parker used the SpectrumView app, though there are others like it. He also posted a screenshot of the spectrogram, as seen in the video, in case you want to test your own spinner.

# It 'Rained' Spiders in Brazil Last Week—and You Can Watch It If You Dare

iStock.com/aury1979

If recent events are anything to go by, you should be less concerned about swallowing spiders in your sleep and more concerned about bird-eating spiders raining down on your head. As The Guardian reports, recent footage from the Brazilian countryside shows thousands of spiders seemingly suspended in mid-air. (Arachnophobes might want to give the video below a miss.)

In reality, they aren’t falling at all. The spiders, which likely belong to a South American species called Parawixia bistriata, are merely crawling on an ultra-fine and nearly invisible web that attaches to two objects, like trees or bushes, to form a canopy.

So why do they do it? To catch prey, naturally. They’re likely to snag a variety of insects and maybe even small birds in their communal web, which can stretch up to 13 feet wide. (And yes, they eat the birds, too.)

Brazilian biology professor Adalberto dos Santos tells The Guardian that P. bistriata are some of the rare “social” spiders that do this. They leave their webs up overnight, hide out in the nearby vegetation, and then return at dawn to feast.

While this natural phenomenon is certainly unsettling, it isn’t exactly rare. Residents of the southeast municipality of Espírito Santo do Dourado, where the video was shot, said these “spider rains” are common when the weather is hot and humid.

Here’s another video from Santo Antônio da Platina in southern Brazil in 2013.

Other species of spider have been known to jump into the wind and "surf" on strands of silk as a means of getting around. They do this to escape threats or get to food or mates in other locations, and cases of "spider flight" have been recorded all over the world. Some especially adventurous spiders have even been known to cross oceans by “ballooning” their way from one land mass to the next.

[h/t The Guardian]

# Watch a Baby Polar Bear Open Its Eyes for the Very First Time

Zoo und Tierpark Berlin, YouTube

Sometimes, after a long week, all you need is something wholesome to lift your spirits. Here to do just that is the Berlin Zoo's newest resident.

In this polar bear video spotted by Geek.com, a 5-week-old cub can be seen opening its eyes for the very first time as its mom, Tonja (pronounced like Tania), cleans and cuddles it. “While it was previously only able to explore its surroundings by groping and cuddling, the little bear can now see and hear things,” according to a translated version of the zoo’s polar bear video caption.

Like kittens and puppies, polar bears are functionally blind and deaf when they’re born. It takes polar bears several weeks longer to develop their senses compared to puppies or kittens, though—about 30 days total. Their claws come later, too.

The diminutive nature of newborn cubs may also come as a surprise. Although full-grown adults can tip the scale at more than 1300 pounds, newborns weigh just 16 to 24 ounces—about the size of a guinea pig. But they pack on the pounds quickly, and can weigh over 100 pounds by the time they’re 8 months old.

A Berlin Zoo spokesperson reportedly said the cub has a big appetite and ate a lot over the holidays (just like the rest of us, apparently). It’s now attempting to walk, but mom and baby aren’t expected to leave the cave in their enclosure before spring arrives.

According to DW Science, zoo staff don’t know the sex of the cub yet. For its protection, they plan to give mom and baby lots of alone time before they approach. Newborn polar bears are quite vulnerable—especially in the wild, where about 85 percent of the bears die before they’re 2 years old.

Meanwhile, zoo staff are keeping a watchful eye on the cub, courtesy of the infrared cameras they have set up in their den.

[h/t Geek.com]

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