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The Largest Prime Number Ever Discovered Has Over 22 Million Digits

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For those in need of a grade school refresher, a prime number is defined as a positive integer that is only divisible by one and by itself. According to New Scientist, Dr. Curtis Cooper of the University of Central Missouri recently discovered the largest prime number ever as part of the Great Internet Mersenne Prime Search (GIMPS). Known as M74207281, the number has 22,338,618 digits, which is five million more than the previous largest prime number (which Cooper also discovered back in 2013).

Curtis Cooper's discovery was announced earlier this month, but the computer found the number way back in September of 2015. A post on the Mersenne blog explains that a "bug prevented the email notification from being sent," so even though the new prime was found months ago, the discovery date reflects when a human first saw it. The number joins the exclusive ranks of only 48 other Mersenne primes—rare numbers (primes that are one less than a power of two) which are named after the French monk Marin Mersenne who studied them in the early 17th century. (There's a handful of helpful YouTube videos if you want a more in depth look at Mersenne primes.)

For the find, Cooper is eligible for a $3000 GIMPS research discovery award, even though the number itself doesn't really have any practical application. As explained in the Mersenne blog post: "While prime numbers are important for cryptography, this prime is too large to currently be of practical value."

That said, the search itself is useful as a means of testing computer hardware, so it's not just about the destination.

To see exactly what a 22,338,618-digit number looks like, head over to the Mersenne site, and check out the video below to hear an interview with Curtis about the discovery.

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History
When Math Discoveries Led to Banned Numbers
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The literature world has seen more than its share of controversy. The best stories tend to provoke the strongest reactions—both positive and negative—in readers, which is why so many classic books have been banned at one point or another. But even a more objective field like math isn’t immune to conflict. In its new video, TED-Ed rounds up the numbers that caused such a stir when they were introduced that they were banned in math circles.

One of the earliest examples comes from ancient Greece. A mathematician named Hippasus was having trouble solving certain equations with fractions and whole numbers alone, so he came up with irrational numbers to make these values easier to express. The ruling school of thought at the time dictated that everything in nature could be explained elegantly with the numbers that already existed. Threatened by Hippasus’s new notion, his fellow mathematicians rejected the irrational numbers and had him exiled.

Other numbers have been banned for legal reasons. When Arab traders brought their positional number system, which included zero, to Italy in the Middle Ages, Florence banned it from record-keeping fearing that they would be easier to forge than Roman numerals. The Arabic way of counting also led to the rise of negative numbers, which were regarded with disdain by many experts into the 19th century. For more banned numbers, including some that are prohibited today, check out the full story below.

[h/t TED-Ed]

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Euclid
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Live Smarter
An Ex-Google Engineer Just Reinvented the Measuring Cup
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Euclid

Recognizing a problem most people didn’t even know they had, former Google and Facebook software engineer Joshua Redstone has made a bold claim for his recent Kickstarter venture: He’s developed a better measuring cup.

According to the Boston Business Journal, Redstone spent four years tinkering with a solution to something that had long annoyed him as an amateur chef: Traditional measuring cups, which are stocky and not very well tapered, don’t do a great job of accurately measuring their own contents. Redstone believes the shape of a cup determines its success, particularly when a cook overfills a liquid or solid by a tiny amount. The smaller the volume, the more the problem is magnified.

Euclid

Redstone’s cup, Euclid, resolves the issue. According to the Kickstarter page: “With traditional measuring cups, the smaller the amount, the harder it is to measure accurately. The culprit? The shape. Straight sides magnify errors when measuring lower down in the cup. Some have tried to solve this problem with conical measuring cups, but their results fall short of Euclid’s by up to 60 percent. Euclid is the only measuring cup with a mathematically optimal, tapered design for consistent accuracy across amounts.”

Euclid is just about ready to overshoot its $30,000 Kickstarter goal. Backers can pay $24 for the cup now, or wait until it’s available at retail for a slightly higher price to be determined. The cup is scheduled for release in May 2018.

[h/t Boston Business Journal]

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