The Air Isn’t Just Gas. Scientists Have Found a Way to Track What’s Really Floating in It

Thanks to a breakthrough study, scientists now have a more accurate way to predict the behavior of irregularly shaped airborne particles, such as dust and microplastics. This could transform everything from climate modeling to disease tracking.

In 1910, British scientist Ebenezer Cunningham developed an equation to measure the drag force on small particles moving through a gas. This equation, known as the Cunningham correction factor, was groundbreaking at the time. However, it assumed that the particles were spherical, an unrealistic model for many types of particles that appear in the natural world. A new study, led by Duncan Lockerby, a mathematician at the University of Warwick, revisits Cunningham’s formula and adjusts it for particles of any shape.

The Spherical Assumption

In 1910, British scientist Ebenezer Cunningham devised a solution. Known as the Cunningham correction factor, his equation in fluid dynamics allowed researchers to calculate the drag on small particles suspended in gas. It was a handy tool, and it became a cornerstone of aerosol science. But it came with a major downside: the math assumed every particle was perfectly spherical.

As explained by Duncan Lockerby, a mathematician at the University of Warwick, that assumption was always a bit of a stretch.

“If  we can accurately predict how particles of any shape move, we can significantly improve models for air pollution, disease transmission, and even atmospheric chemistry,” he noted. “This new approach builds on a very old model—one that is simple but powerful—making it applicable to complex and irregular-shaped particles.”

For decades, this oddity threw off even the best efforts to model how particles move. Even though Nobel laureate Robert Millikan refined the formula in the 1920s, the basic issue of shape was never addressed, until now.

Revising a Century of Physics

Lockerby, working at the intersection of mathematics and engineering, decided it was time to revisit the old texts. His goal was not just to tweak the numbers, but to fundamentally expand the model. The results of his work were recently published in the Journal of Fluid Mechanics.

“The motivation was simple,” Lockerby explained in a statement released by the university. “If we can accurately predict how particles of any shape move, we can significantly improve models for air pollution, disease transmission, and even atmospheric chemistry.”

He found that a broader solution had been overlooked for years. While Millikan’s adjustments were useful, they didn’t address the main issue of irregular shapes.

The ‘Correction Tensor’ Breakthrough

To solve the puzzle, Lockerby introduced what mathematicians call a “correction tensor.” The term might sound like something out of a physics textbook on relativity, where tensors are used to define the geometry of space-time, but in this context, it serves a very grounded purpose.

According to him, this new mathematical object accounts for drag and resistance on particles of any configuration. Instead of forcing a jagged microplastic fragment or a spiky virus into a spherical box, the tensor calculates how the air flows around its actual shape.

“It provides the first framework to accurately predict how non-spherical particles travel through the air,” he said.

And that matters for our health, since these nanoparticles are closely tied to cancer and breathing problems.

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