February 7, 2025: Today we're covering controversial Alzheimer's guidelines, AI that gazes into goat faces and the wild history of mathematical symbols. —Robin Lloyd, Contributing Editor | | | A not-to-scale illustration of an asteroid's orbital path crossing the orbit of Earth around the sun. Nazarii Neshcherenskyi/Getty Images | | | The Wild History of Math Symbols | In the mid 1500s, scholars waged "the battle of the equals sign." This complex conflict is one of the previously untold stories that comes up during applied mathematics Ph.D. candidate Max Springer's discussion with mathematician Raúl Rojas about his recent book, The Language of Mathematics: The Stories behind the Symbols. Thinkers also historically have debated and continue to discuss the invention of the symbol for zero as well as other mathematical notation questions. Some mathematical notation has varied regionally. And you might never have been aware of some of the symbols Rojas explores, such as the "for all" symbol.
Why this matters: Students who dozed during conventional curriculum in math class became energized and excited when Rojas assigned each of them to study the origins of a math symbol. The interest in these human stories inspired Rojas's book, he says.
What the experts say: "The excitement of doing mathematics comes from this knowledge that you are building on a framework developed by fascinating people over thousands of years," Rojas says. | | |  | A number of scientists now think that Alzheimer's disease (AD) should be diagnosed on the basis of its underlying biology, not symptoms, which they see as the condition's end-stage, writes Laura Hercher, who directs student research at a graduate program in human genetics. Such an approach could enable diagnoses at earlier or asymptomatic stages, such as mild cognitive impairment. "Dementia is a result. Dementia is a symptom," says neuroradiologist Clifford R. Jack, Jr. Detractors think that biomarkers alone are insufficient for an AD diagnosis.
What the experts say: Although the U.S. Food and Drug Administration has yet to approve any curative treatments for AD, diagnosing it only once dementia fully sets in is "detrimental to care for patients affected by the disease," neurologist Bruno Dubois wrote in a 2018 paper.
Why this matters: A more precise, biologically grounded definition of AD could yield more specific information for patients as well as risk assessments for relatives. And it could enable screening for people at risk of AD as well as stronger study populations of people who truly have or do not have the condition. However, screenings have a mixed track record elsewhere in medicine in terms of delivering patient benefits versus harms. | | | If you're enjoying all the science we cover in this newsletter, dive deeper with a subscription to Scientific American. You'll have access to all our articles and will be supporting crucial science journalism. | | | • We should teach children that their emotions and related behavior need not mirror gendered social expectations, writes behavioral and data scientist Pragya Agarwal. Such expectations can harm kids as they develop a sense of self and learn to regulate their emotions. | 6 min read | | | Do you know the answer to the first question of today's science quiz? Also, don't miss today's Spellements. If you spot any science words missing from Spellements, email them to games@sciam.com. In recent days, reader Donald R. found inion. Joaquin M. of Madrid, Spain, found otitis. Margaret M. found recurve, noting that a recurve bow is "an interesting device. Because of its shape and the way it's strung, a recurve bow is able to store more energy and then use that energy more effectively upon shooting an arrow than a more traditional bow." | | | MOST POPULAR STORIES OF THE WEEK | | | • Bonobos can tell when a human doesn't know something. | 3 min read | • A newfound asteroid may hit Earth in 2023, scientists say. | 6 min read | | | Earth has seven continents, most of us were told as kids. Perhaps we were exposed to the " Seven Continents Song." Later on, armed with earth science and better pattern recognition skills, you might have questioned this received wisdom. So it's satisfying when it comes to light that scientists are not in full agreement about the number of Earth's continents (nor what a continent is). The former could be six, according to this recent quick story, published this week. Or two or three, per this longer coverage published in October. In 2017, some researchers argued for 8. It's probably a good thing that Schoolhouse Rock! and Interplanet Janet never tackled the subject. | —Robin Lloyd, Contributing Editor | | Subscribe to this and all of our newsletters . | | | | Scientific American
One New York Plaza, New York, NY, 10004 | | | | | | Support our mission, subscribe to Scientific American | | | | | | | | | |
