In 2019, scientists shook living earthworms at high frequencies to study their changing shapes, uncovering an unusual physics phenomenon that earned one of science’s strangest prizes

An earthworm hardly seems like the obvious place to look for a physics breakthrough. Yet in 2019, researchers turned the humble soil-dweller into an unlikely laboratory, placing living worms on a vibrating surface and watching closely as their bodies began to ripple.

The experiment, led by physicist Ivan Maksymov and applied mathematician Andrey Pototsky of Swinburne University of Technology, was not simply an attempt to make worms wiggle. The researchers wanted to investigate whether a living organism could display a phenomenon normally associated with vibrating liquids. Their work, later published in Scientific Reports, showed that it could.

When a worm starts behaving like a liquid

The key to the experiment lies inside the worm. According to Maksymov and Pototsky, an earthworm has a flexible outer body wall surrounding a largely water-like internal cavity. This arrangement effectively gives the animal a hydrostatic skeleton, with fluid pressure helping support its shape. That makes the worm, from a physicist’s perspective, surprisingly similar to a soft, liquid-filled cylinder.

The researchers were interested in Faraday waves, patterns that can appear when a liquid is subjected to vertical vibration. In a familiar version of the phenomenon, a liquid surface that is shaken strongly enough can stop remaining flat and develop standing wave patterns.

The question was whether something similar could happen inside the body of a living animal.

To find out, the scientists tested four species of earthworms found in southeastern Australia. The worms were placed horizontally on a thin Teflon plate connected to a vibrating subwoofer. The plate was driven vertically at controlled frequencies while the researchers monitored the worms’ movements.

A laser watched the worm’s every ripple

The setup was more sophisticated than the bizarre premise suggests. A laser was directed at the worm, and a photodetector measured changes in the reflected light as the animal vibrated. The researchers then analysed those signals to determine the frequencies and characteristics of the movement. A digital camera was also used to track the worm’s shape.

At one test frequency of 40 hertz, the researchers detected something particularly revealing: alongside the worm’s response at the driving frequency, its body produced a subharmonic response at 20 hertz, half the frequency used to shake it. Video analysis of the entire worm confirmed the same pattern.

That mattered because subharmonic responses are a hallmark of parametrically excited systems, including Faraday-wave phenomena.

The worm was not merely bouncing up and down. Its flexible, fluid-filled body was developing wave-like deformations.

From backyard experiment to Ig Nobel

The unusual research eventually earned Maksymov and Pototsky the 2020 Ig Nobel Prize in Physics, an award designed to celebrate research that first makes people laugh and then makes them think.

There was a serious idea underneath the strange experiment. The broader research was motivated in part by questions about whether acousto-mechanical signals could play a role in biological systems and neuroscience. Their paper suggested that similar nonlinear wave behaviour might eventually be worth investigating in other biological structures.

And the worms themselves survived the unusual encounter. According to the Australian Research Council, the animals recovered after the experiments and were returned to a worm farm.