For generations, students have been taught that we slip on ice because pressure and friction cause it to melt beneath our feet.
The idea was that when you step onto an icy sidewalk, your body weight and the heat from your shoe create a thin layer of water, which makes the surface slippery.
But new research from Saarland University shows that this long-accepted explanation isn’t quite right.
According to physicist Professor Martin Müser and his colleagues Achraf Atila and Sergey Sukhomlinov, the true reason lies in something called molecular dipoles.
Their study, published in Physical Review Letters, overturns nearly 200 years of scientific understanding.
So what exactly are dipoles? A dipole forms when a molecule has one side with a slight positive charge and another with a slight negative charge, giving it polarity. Water molecules, which make up ice, are naturally polar. Below freezing, they line up neatly in a crystalline pattern, forming solid ice.
When a shoe or ski comes into contact with the ice, it’s not pressure or heat that disrupts this order. Instead, the dipoles in the material of the shoe or ski interact with the dipoles in the ice. This clash scrambles the tidy molecular structure at the surface, breaking it down into a disordered, liquid-like layer.
In physics, this is described as “frustration,” where competing forces prevent the system from staying stable.
In other words, slipping on ice has less to do with melting from body weight or warmth and more to do with tiny molecular forces pulling the surface out of order.
This discovery also challenges another long-held belief: that skiing below –40°C is impossible because it would be too cold for a lubricating water layer to form.
Müser and his team showed that dipole interactions still create a film even at extremely low temperatures, close to absolute zero. At such frigid conditions, the film becomes so thick and sticky it behaves more like honey than water, meaning skiing wouldn’t really work. But crucially, the liquid layer still exists.
For everyday people who slip and fall on icy sidewalks, whether pressure, friction, or dipoles are to blame might not matter much. But for science, the difference is significant. Understanding the true physics of why ice is slippery could influence fields ranging from winter sports to materials science.
“There are still a lot of surprises when it comes to something as familiar as ice,” Müser explains. This new perspective shows how even centuries-old assumptions can be overturned when scientists look more closely at the invisible forces shaping our world.
