‘Friction is one of the oldest and most intricate problems in physics,’ yet ‘it is difficult to predict and control’
Bookmark popover
‘Friction is one of the oldest and most intricate problems in physics,’ yet ‘it is difficult to predict and control’open image in gallery
‘Friction is one of the oldest and most intricate problems in physics,’ yet ‘it is difficult to predict and control’ (Copyright 2024 The Associated Press. All rights reserved)
Your support helps us to tell the story
Read moreSupport Now
From reproductive rights to climate change to Big Tech, The Independent is on the ground when the story is developing. Whether it's investigating the financials of Elon Musk's pro-Trump PAC or producing our latest documentary, 'The A Word', which shines a light on the American women fighting for reproductive rights, we know how important it is to parse out the facts from the messaging.
At such a critical moment in US history, we need reporters on the ground. Your donation allows us to keep sending journalists to speak to both sides of the story.
The Independent is trusted by Americans across the entire political spectrum. And unlike many other quality news outlets, we choose not to lock Americans out of our reporting and analysis with paywalls. We believe quality journalism should be available to everyone, paid for by those who can afford it.
**Your support makes all the difference.**Read more
The distinctive squeak of basketball shoes on court, a sound as integral to the game as the swish of the net, has finally been scientifically explained by researchers at Harvard University. The ubiquitous noise, which caught the ear of materials scientist Adel Djellouli during a Boston Celtics game, prompted an investigation into its origins.
"This squeaking sound when players are sliding on the floor is omnipresent," Djellouli observed. "It’s always there, right?" This constant rasp of rubber soles against hardwood, as players pivot and defenders shift, became the subject of a new study published in the journal Nature.
Upon returning from the game, Djellouli, driven by curiosity, collaborated with colleagues to recreate the phenomenon in a lab. They repeatedly slid a sneaker against a smooth glass plate, recording the resulting squeaks with a microphone and filming the interaction with a high-speed camera to capture the microscopic details.
Their findings revealed that the squeak is produced as tiny sections of the shoe’s sole rapidly change shape, momentarily losing and regaining contact with the floor thousands of times per second. This rapid oscillation occurs at a frequency that precisely matches the pitch of the audible squeak. "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.
‘Friction is one of the oldest and most intricate problems in physics,’ yet ‘it is difficult to predict and control’open image in gallery
‘Friction is one of the oldest and most intricate problems in physics,’ yet ‘it is difficult to predict and control’ (Copyright 2024 The Associated Press. All rights reserved)
The study also highlighted the crucial role of grip patterns. When researchers tested flat, featureless rubber blocks against the glass, they observed chaotic, disorganized ripples but no accompanying squeaks. This suggests that the ridge-like designs on shoe soles are essential for organising these bursts, enabling them to produce a clear, high-pitched sound.
While friction has been extensively studied, this research is notable for examining it at much faster speeds and, for the first time, directly linking these rapid pulses to the squeaking sound they generate. The implications extend beyond the basketball court. As physicist Bart Weber noted in an accompanying editorial, "Friction is one of the oldest and most intricate problems in physics," yet "it is difficult to predict and control."
A deeper understanding of friction could offer insights into how Earth’s tectonic plates slide during earthquakes or help develop methods to reduce energy loss from friction and wear in various applications. On a more mundane level, it could even lead to the elimination of awkward squeaks in quiet environments, such as office hallways.
Though the study doesn't offer an immediate fix for noisy footwear – and internet advice like rubbing soap on soles can be risky – its insights could pave the way for designing squeak-free shoes in the future. For instance, experiments showed that altering the thickness of the rubber could change the pitch of the squeak. This raises the intriguing possibility of fine-tuning shoes to squeak at frequencies too high for human ears to detect.
"We can now start designing for it," said Weber, from the Advanced Research Center for Nanolithography and the University of Amsterdam. "We can start making interfaces that either do it if we want to hear this sound, or don’t do it if we don’t want to hear it."