Ars Technica's Beth Mole reports: Editors of the environmental chemistry journal Chemosphere have posted an eye-catching correction to a study reporting toxic flame retardants from electronics wind up in some household products made of black plastic, including kitchen utensils. The study sparked a flurry of media reports a few weeks ago that urgently implored people to ditch their kitchen spatulas and spoons. Wirecutter even offered a buying guide for what to replace them with. The correction, posted Sunday, will likely take some heat off the beleaguered utensils. The authors made a math error that put the estimated risk from kitchen utensils off by an order of magnitude. Specifically, the authors estimated that if a kitchen utensil contained middling levels of a key toxic flame retardant (BDE-209), the utensil would transfer 34,700 nanograms of the contaminant a day based on regular use while cooking and serving hot food. The authors then compared that estimate to a reference level of BDE-209 considered safe by the Environmental Protection Agency. The EPA's safe level is 7,000 ng -- per kilogram of body weight -- per day, and the authors used 60 kg as the adult weight (about 132 pounds) for their estimate. So, the safe EPA limit would be 7,000 multiplied by 60, yielding 420,000 ng per day. That's 12 times more than the estimated exposure of 34,700 ng per day. However, the authors missed a zero and reported the EPA's safe limit as 42,000 ng per day for a 60 kg adult. The error made it seem like the estimated exposure was nearly at the safe limit, even though it was actually less than a tenth of the limit. "We regret this error and have updated it in our manuscript," the authors said in a correction. "This calculation error does not affect the overall conclusion of the paper," the correction reads. The study maintains that flame retardants "significantly contaminate" the plastic products, which have "high exposure potential."

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Slashdot reader jjslash brings word that Casio "has reintroduced its iconic calculator watch featuring a retro design with green text on a negative LCD and a classic keypad layout." TechSpot reports that the watch was based on the Casio Mini personal calculator first released in the early 1970s — even offering a keypad using the original fonts (with numbers separated by grid lines): Even the mode button, colored red, is a nod to the calculator's power indicator. The watches' calculator function can add, subtract, multiply, and divide up to eight digits. As for watch functions, you get dual time, an alarm, stopwatch functionality, and more... Casio's original personal calculator debuted in 1972, and cost $59.95. It featured a six-digit display, was a quarter the size of its competitors, and cost just a third of rival products. The calculator was an instant hit for Casio, selling a million units in the first 10 months on the market and more than six million units over the span of the series. Long-time Slashdot reader antdude says "I still wear one! Casio Data Bank 150 model...!" Share your own vintage calculator memories in the comments...

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Australian mathematicians have proven the famous "infinite monkey theorem" impossible within the universe's lifespan. The theorem suggests monkeys typing randomly would eventually produce Shakespeare's complete works. Scientists Stephen Woodcock and Jay Falletta calculated that even 200,000 chimpanzees typing one character per second until the universe's heat death would fail to reproduce Shakespeare's writings. A single chimp has only a 5% chance of typing "bananas" in its lifetime, with more complex phrases facing astronomically lower odds. "This finding places the theorem among other probability puzzles and paradoxes... where using the idea of infinite resources gives results that don't match up with what we get when we consider the constraints of our universe," Associate Prof Woodcock was quoted as saying by BBC.

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Former Nvidia engineer Luke Durant, working with the Great Internet Mersenne Prime Search (GIMPS), recently discovered the largest known prime number: (2^136,279,841)-1 or M136279841 (where the number following the letter M represents the exponent). The achievement was detailed on Mersenne.org. Tom's Hardware reports: This is the largest prime number we've seen so far, with the last one, M82589933, being discovered six years prior. What makes this discovery particularly fascinating is that this is the first GIMPS discovery that used the power of data center GPUs. Mihai Preda was the first one to harness GPU muscle in 2017, says the GIMPS website, when he "wrote the GpuOwl program to test Mersenne numbers for primarilty, making his software available to all GIMPS users." When Luke joined GIMPS in 2023, they built the infrastructure needed to deploy Preda's software across several GPU servers available in the cloud. While it took a year of testing, Luke's efforts finally bore fruit when an A100 GPU in Dublin, Ireland gave the M136279841 result last October 11. This was then corroborated by an Nvidia H100 located in San Antonio, Texas, which confirmed its primality with the Lucas-Lehmer test.

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Theoretical Physicist Jacques Treiner, from the University of Paris Cite, explains why you should run in the rain: ... Let p represent the number of drops per unit volume, and let a denote their vertical velocity. We'll denote Sh as the horizontal surface area of the individual (e.g., the head and shoulders) and Sv as the vertical surface area (e.g., the body). When you're standing still, the rain only falls on the horizontal surface, Sh. This is the amount of water you'll receive on these areas. Even if the rain falls vertically, from the perspective of a walker moving at speed v, it appears to fall obliquely, with the angle of the drops' trajectory depending on your speed. During a time period T, a raindrop travels a distance of aT. Therefore, all raindrops within a shorter distance will reach the surface: these are the drops inside a cylinder with a base of Sh and a height of aT, which gives: p.Sh.a.T. As we have seen, as we move forward, the drops appear to be animated by an oblique velocity that results from the composition of velocity a and velocity v. The number of drops reaching Sh remains unchanged, since velocity v is horizontal and therefore parallel to Sh. However, the number of drops reaching surface Sv -- which was previously zero when the walker was stationary -- has now increased. This is equal to the number of drops contained within a horizontal cylinder with a base area of Sv and a length of v.T. This length represents the horizontal distance the drops travel during this time interval. In total, the walker receives a number of drops given by the expression: p.(Sh.a + Sv.v). T Now we need to take into account the time interval during which the walker is exposed to the rain. If you're covering a distance d at constant speed v, the time you spend walking is d/v. Plugging this into the equation, the total amount of water you encounter is: p.(Sh.a + Sv.v). d/v = p.(Sh.a/v + Sv). d This equation proves that the faster you move, the less water hits your head and shoulders, but the amount of water hitting the vertical part of your body remains constant. To stay drier, it's best to move quickly and lean forward. However, you'll have to increase your speed to offset the exposed surface area caused by leaning.

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Apple's latest iOS update has removed the "C" button from its Calculator app, replacing it with a backspace function. The change, part of iOS 18, has sparked debate among users accustomed to the traditional clear function. The removal of the "C" button represents a significant departure from decades-old calculator design conventions, The Atlantic writes. From the story: The "C" button's function is vestigial. Back when calculators were commercialized, starting in the mid-1960s, their electronics were designed to operate as efficiently as possible. If you opened up a desktop calculator in 1967, you might have found a dozen individual circuit boards to run and display its four basic mathematical functions. Among these would have been an input buffer or temporary register that could store an input value for calculation and display. The "C" button, which was sometimes labeled "CE" (Clear Entry) or "CI" (Clear Input), provided a direct interface to zero out -- or "clear" -- such a register. A second button, "AC" (All Clear), did the same thing, but for other parts of the circuit, including previously stored operations and pending calculations. (A traditional calculator's memory buttons -- "M+," "M-," "MC" -- would perform simple operations on a register.) By 1971, Mostech and Texas Instruments had developed a "calculator on a chip," which condensed all of that into a single integrated circuit. Those chips retained the functions of their predecessors, including the ones that were engaged by "C" and "AC" buttons. And this design continued on into the era of pocket calculators, financial calculators, and even scientific calculators such as the ones you may have used in school. Some of the latter were, in essence, programmable pocket computers themselves, and they could have been configured with a backspace key. They were not.

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chalsall writes: After more than six years of work since the last discovery, the Great Internet Mersenne Prime Search (GIMPS) has found the 52nd known Mersenne Prime number. This is also the largest prime number known to humans. The number is 2^136,279,841-1, which is 41,024,320 decimal digits long. Luke Durant, a researcher from San Jose, CA, found it after contributing a fantastic amount of compute to the GIMPS project.

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