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Grace Hopper Explains Nanoseconds to Letterman

Rear Admiral Grace Hopper is famous both as a computer pioneer and for, at the time of her retirement (at age 79), being the nation's oldest active military officer. Hopper worked on early computers, and is widely credited with popularizing the term "computer bug" after she found a moth stuck inside a relay in Harvard's Mark II computer in 1947. (Thus "debugging" became the term for fixing computer problems....) You can see the first computer bug (they kept the moth!) at the Smithsonian, in the American History museum.

In this 1986 interview with David Letterman, Grace Hopper displays her grace and wit, and explains the concept of a nanosecond, using Bell System telephone wire cut into 30cm lengths -- 30cm is the maximum distance light can travel in a billionth of a second. Here's a representative quote:

"When an admiral asks you why it takes so damn long to send a message via satellite, you point out to him that between here and the satellite there are a very large number of nanoseconds. [Waves the wire at the sky.]"

She also gets into picoseconds! Enjoy:

You can read more about Hopper from Wikipedia.

(Via Waxy.)

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Stradivarius Violins Get Their Distinctive Sound By Mimicking the Human Voice
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Italian violinist Francesco Geminiani once wrote that a violin's tone should "rival the most perfect human voice." Nearly three centuries later, scientists have confirmed that some of the world's oldest violins do in fact mimic aspects of the human singing voice, a finding which scientists believe proves "the characteristic brilliance of Stradivari violins."

Using speech analysis software, scientists in Taiwan compared the sound produced by 15 antique instruments with recordings of 16 male and female vocalists singing English vowel sounds, The Guardian reports. They discovered that violins made by Andrea Amati and Antonio Stradivari, the pioneers of the instrument, produce similar "formant features" as the singers. The resonance frequencies were similar between Amati violins and bass and baritone singers, while the higher-frequency tones produced by Stradivari instruments were comparable to tenors and contraltos.

Andrea Amati, born in 1505, was the first known violin maker. His design was improved over 100 years later by Antonio Stradivari, whose instruments now sell for several million dollars. "Some Stradivari violins clearly possess female singing qualities, which may contribute to their perceived sweetness and brilliance," Hwan-Ching Tai, an author of the study, told The Guardian.

Their findings were published in the journal Proceedings of the National Academy of Sciences of the United States of America. A 2013 study by Dr. Joseph Nagyvary, a professor emeritus at Texas A&M University, also pointed to a link between the sounds produced by 250-year-old violins and those of a female soprano singer.

According to Vox, a blind test revealed that professional violinists couldn't reliably tell the difference between old violins like "Strads" and modern ones, with most even expressing a preference for the newer instruments. However, the value of these antique instruments can be chalked up to their rarity and history, and many violinists still swear by their exceptional quality.

[h/t The Guardian]

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How Michael Jackson's Dancing Defied the Laws of Biomechanics
Phil Walter, Getty Images
Phil Walter, Getty Images

From the time he debuted the moonwalk on broadcast television in 1983, Michael Jackson transcended the label of "dancer." His moves seemed to defy gravity as well as the normal limits of human flexibility and endurance.

Now we have some scientific evidence for that. Three neurosurgeons from the Postgraduate Institute of Medical Education and Research in Chandigarh, India, recently published a short paper in the Journal of Neurosurgery: Spine that examines just how remarkable one of Jackson's signature moves really was.

In the 1988 video for "Smooth Criminal" and subsequent live performances, Jackson is seen taking a break from his constant motion to stand in place and lean 45 degrees forward. Both he and his dancers keep their backs straight. Biomechanically, it's not really possible for a human to do. And even though he had a little help, the neurosurgeons found it to be a pretty impressive feat.

An illustration of Michael Jackson's 'Smooth Criminal' dance move.
Courtesy of 'Journal of Neurosurgery: Spine.' Copyright Manjul Tripathi, MCh.

Study co-author Manjul Tripathi told CNN that humans can't lean forward much more than 25 or 30 degrees before they risk landing on their faces. (He knows, because he tried it.) Normally, bending involves using the hip as a fulcrum, and erector spinae muscles to support our trunk. When Jackson leaned over, he transferred the fulcrum to the ankle, with the calf and Achilles tendon under strain. Since that part of the body is not equipped to support leaning that far forward without bending, the "Smooth Criminal" move was really a biomechanical illusion. The act was made possible by Jackson's patented shoe, which had a "catch" built under the heel that allowed him to grasp a protruding support on the stage. Secured to the floor, he was able to achieve a 45-degree lean without falling over.

But the neurosurgeons are quick to point out that the shoes are only part of the equation. To achieve the full 45-degree lean, Jackson would have had to have significant core strength as well as a strong Achilles tendon. An average person equipped with the shoe would be unable to do the move.

How does this apply to spinal biomechanics research? The authors point out that many dancers inspired by Jackson are continuing to push the limits of what's possible, leading to injury. In one 2010 paper, researchers surveyed 312 hip-hop dancers and found that 232 of them—almost 75 percent of the cohort—reported a total of 738 injuries over a six-month period. That prevalence could mean neurosurgeons are facing increasingly complex or unique spinal issues. The surgeons hope that awareness of potential risks could help mitigate problems down the road.

[h/t CNN]

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