briefs

The persistent squeak of sneakers on basketball courts, a sound synonymous with the sport, has been definitively explained by physicists at Harvard University. A study published Wednesday in the journal Nature details how the noise isn’t simply friction, but a complex interplay of stick-slip motion and the unique design of sneaker treads.

Adel Djellouli, a materials scientist at Harvard, initially became curious about the phenomenon while attending a Boston Celtics game. “This squeaking sound when players are sliding on the floor is omnipresent,” Djellouli said, according to the Associated Press. “It’s always there, right?” This observation spurred a research project involving high-speed cameras and a glass plate used to simulate a basketball court surface.

The research revealed that the squeak originates from thousands of tiny, rapid detachments and reattachments between the sneaker sole and the floor, occurring at a rate of approximately 4,800 times per second. These minute “ripples” create fluctuations in air pressure, resulting in the high-pitched sound. “That squeaking is basically your shoe rippling, or creating wrinkles that travel super fast. They repeat at a high frequency, and this is why you get that squeaky noise,” Djellouli explained, as reported by the Independent.

Crucially, the study found that the tread patterns on sneakers are essential to producing the squeak. When researchers tested flat, featureless rubber blocks against the glass plate, they observed disorganized ripples but no discernible squeaking sound. The ridges on sneaker soles appear to organize these pulses, creating a clear, consistent pitch. According to Science News, the thickness and stiffness of the rubber block also influence the pitch of the sound.

The findings build on the concept of “stick-slip motion,” where surfaces alternately adhere and slide against each other. This process, previously understood in broader physics contexts, has now been specifically applied to explain the mechanics of sneaker squeaks. The research team used total internal reflection to image the shoe’s sole, highlighting areas of contact and detachment during the sliding motion.

The study, inspired by a single observation during an NBA game, provides a detailed physical explanation for a sound that has long been a part of the basketball experience. Researchers have not yet indicated plans to investigate methods for reducing or eliminating the squeak, leaving the distinctive sound to continue as a hallmark of the game.

Mexico City – Climate change may imperil the monarch butterfly’s remarkable annual migration, potentially disrupting a natural phenomenon that spans thousands of kilometers across North America, according to latest research published Monday in PLOS Climate.

The study, conducted by biologists at the National Autonomous University of Mexico, utilized computer simulations to project the future availability of suitable habitat for the monarch butterfly in Mexico. Researchers found that by 2070, the area of ideal overwintering habitat could shrink from approximately 19,500 square kilometers to around 8,000 square kilometers. This reduction is driven by shifting climate patterns that could push the necessary conditions for milkweed growth – the sole food source for monarch caterpillars – further south.

“That extra distance might push some individuals to stay in Mexico instead of continuing north,” said Carolina Ureta, a biologist at the National Autonomous University of Mexico in Mexico City, and a co-author of the study. “In this case, the species is not in danger because of climate change, but the migration might be.”

The monarch butterfly is unique in its multi-generational, two-way migration, comparable to that of birds. Unlike other butterfly species, monarchs cannot survive the cold winters of northern climates and must travel south to warmer regions for the winter months. Eastern North American monarchs overwinter in the oyamel fir forests of the Sierra Madre Mountains in Mexico, while those in the western part of the continent overwinter in California.

The potential loss of habitat isn’t the only threat facing the iconic insect. Monarch populations have already declined by more than 80 percent since the 1990s, falling from nearly 700 million to significantly lower numbers. Habitat loss, extreme weather events, pesticide use, and parasitic infections are all contributing factors to this decline, according to researchers.

Citizen scientists have observed a trend of monarchs remaining in central and northeastern Mexico, rather than completing the full migratory cycle, according to Víctor Sánchez Cordero, a conservation biologist also at the National Autonomous University of Mexico. This behavior, he noted, is not uncommon among butterfly populations globally, as some species do not undertake long-distance migrations.

The simulations suggest that climate change could not only reduce the overall habitat area but also fragment it, creating a more challenging and energy-intensive journey for the butterflies. The increased distance could lead some monarchs to forgo the return flight north, potentially establishing resident populations within Mexico. Researchers suggest that wing size could be a key indicator of whether butterflies are completing the migration or remaining in Mexico, as resident populations tend to have smaller wingspans than migratory ones.

The overwintering sites in Mexico, located at elevations between 2,400 and 3,600 meters, provide a specific microclimate crucial for the butterflies’ survival. Temperatures in these oyamel fir forests typically range from 0 to 15 degrees Celsius, allowing the monarchs to conserve energy. Still, shifting climate patterns could alter these conditions, making the existing overwintering sites less hospitable.

An extreme close-up of the silk spun by the Australian net-casting spider, Asianopis subrufa, has been awarded top prize in the Royal Society Publishing Photography Competition 2025. The winning image, captured by arachnologist Martín Ramírez, reveals the intricate structure of the spider’s unique silk, which allows it to effectively ensnare prey.

The photograph, taken using a scanning electron microscope (SEM), depicts a section of silk just 50 microns in width – approximately 0.05 millimeters. Ramírez, a research scientist at the Bernardino Rivadavia Natural Sciences Argentine Museum in Buenos Aires, prepared the sample by coating it with a thin layer of gold and palladium to enhance visibility under the high vacuum conditions of the microscope. The image showcases the elastic core of the silk, surrounded by strengthening fibers.

Unlike orb-weaver spiders that rely on sticky, poisonous droplets, the net-casting spider employs elasticity to capture its meals. The spider constructs a small, postage stamp-sized net from cribellate silk, produced by an organ called a cribellum, which contains thousands of tiny holes. Individual silk fibers, each nanoscale in thickness, are drawn from these holes and woven together to create a strong, woolly net.

“Just from observing the behaviour, we knew something spectacular was going to be there,” Ramírez said. “The web is incredibly stretchy; no normal silk can extend in that way to then return to its original form.” Ramírez and collaborator Jonas Wolff, from Greifswald University, have been studying the tension and stretchiness of the silk, conducting dissections to measure its elastic properties.

The net-casting spider holds the web between its front legs and throws it over approaching insects. The ability of the silk to stretch significantly during the cast and then return to its original shape, is crucial to the spider’s hunting success. The SEM image provides a detailed view of the structural elements that enable this unique elasticity.

The Royal Society Publishing Photography Competition aims to highlight the wonders of scientific phenomena through visual imagery. The winning photograph serves as a reminder of the intricate details often hidden from the naked eye, requiring specialized tools like the electron microscope to reveal them.