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William Jones: The First Math Teacher to Use Pi

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Eighteenth-century mathematician William Jones had a problem with pi—namely, it didn’t exist yet. At the time of his working and teaching in the field of mathematics, there was no term for the ratio of a circle’s circumference to its diameter, despite the value’s importance to even the most basic study of geometry. In his 1706 book, Synopsis Palmariorum Matheseos, or A New Introduction to the Mathematics, he made a modest proposal: that the universal constant be known as pi, and thus was mathematical history born.

Before being ascribed a modern name, pi existed under the guise of a bulkier, more antiquated phrase: quantitas in quam cum multiflicetur diameter, proveniet circumferencia—Latin for “the quantity which, when the diameter is multiplied by it, yields the circumference.” While descriptive, the collection of words required to denote pi before “pi” did not lend itself to clear or efficient discussion of the concept. Prior to Jones publishing his bold decision, fractions like 22/7 or 355/113 often served to fill in for the mysterious constant, but gave the erroneous impression that the number was a rational one, which can be fully expressed by one whole number divided into another—an assumption that had not yet been disproved, but with which Jones firmly disagreed. For this reason, only an idealized symbol would suffice to represent the concept, and so the Welshman turned to the Greek alphabet.

π, written in Roman letters as “pi,” is the Greek equivalent to our letter ‘p’. For this reason, 17th-century mathematician William Oughtred used π to denote the “periphery,” or the circumference of any given circle—a value that changed as the circle changed. Jones borrowed this earlier logic and applied it to his theory of an irrational, but universal constant value for the circle’s circumference-to-diameter ratio. Johann Lambert’s definitive proof in 1761 that π was an irrational number justified Jones’s earlier instinct, and once Swiss mathematician Leonhard Euler began to use and widely disseminate the symbol π in correspondence with his contemporaries, π was here to stay.

In honor of William Jones, unsung hero of pi, throw on one of these two new mental_floss t-shirts and have a moment of silence for the man responsible for turning pi from a letter into a number.

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Why America Still Hasn’t Switched From Fahrenheit to Celsius
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If you grew up in America, you know that when the thermometer reads 32° F it’s time to bundle up, and if it’s 85° F outside you should break out a t-shirt. But say these temperatures to someone living in a different part of the world and you’ll likely be met with confusion. That’s because the United States joins Myanmar and Liberia as one of only three nations that don’t recognize the metric system.

In its new video, Vox explains why the U.S. is still measuring degrees in Fahrenheit long after the rest of the world decided to make the switch to metric. It wasn’t for the government’s lack of trying: In 1975, the country passed the Metric Conversion Act with the intention of selling the system to Americans. But while Canada, the UK, and Australia made adopting metric measurements mandatory, there was no such enforcement in the U.S. So, given the option to stick with what they know or teach themselves a whole new system, U.S. citizens chose the former.

To learn about the history of Fahrenheit and Celsius, and to see how the imperial system is more than just a nuisance for people visiting the U.S., check out Vox’s full report below.

[h/t Vox]

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148 Lost Alan Turing Papers Discovered in Filing Cabinet
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Courtesy University of Manchester

You never know what you’re going to uncover when you finally get around to combing through that decades-old filing cabinet in the back room. Case in point: The University of Manchester recently unearthed 148 long-lost papers belonging to computer science legend Alan Turing, as ScienceAlert reports.

The forgotten papers mostly cover correspondence between Turing and others between 1949 and his death in 1954. The mathematician worked at the university from 1948 on. The documents include offers to lecture—to one in the U.S., he replied, “I would not like the journey, and I detest America”—a draft of a radio program he was working on about artificial intelligence, a letter from Chess magazine, and handwritten notes. Turing’s vital work during World War II was still classified at the time, and only one document in the file refers to his codebreaking efforts for the British government—a letter from the UK’s security agency GCHQ. The papers had been hidden away for at least three decades.

A typed letter to Alan Turing has a watermark that says 'Chess.'
Courtesy University of Manchester

Computer scientist Jim Miles found the file in May, but it has only now been sorted and catalogued by a university archivist. "I was astonished such a thing had remained hidden out of sight for so long," Miles said in a press statement. "No one who now works in the school or at the university knew they even existed." He says it’s still a mystery why they were filed away in the first place.

The rare discovery represents a literal treasure trove. In 2015, a 56-page handwritten manuscript from Turing’s time as a World War II codebreaker sold for more than $1 million.

[h/t ScienceAlert]

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