Amnon Yariv, a 90-year-old Israeli-American physics professor, may have repeated history by discovering something in his bathroom. Four years ago, during the height of the COVID-19 pandemic, the physicist was in the shower when he first noticed something that, after years of research, was confirmed to be a new mode of vibration in nature.
On a hot summer afternoon during the coronavirus lockdown, Yariv was in the shower but left the water running with the shower head dripping.Such an incident doesn’t grab our attention, but it did catch the eye of a National Medal of Science-winning professor who has studied waves and their properties for more than 70 years.
Yariv realized that the showerhead exhibited characteristics that make it more than just a flexible fixture in the bathroom, but part of a vibrating system. Legend has it that 2,000 years ago, Greek physicist Archimedes quickly jumped out of the bath after making a groundbreaking observation. Modern scientist Yariv took a more cautious approach in this regard.
What did Yariv observe?
Yariv noticed that increasing the water flow caused the showerhead to undergo bimodal vibrations. In simple terms, this means that the showerhead began to vibrate in two different ways: one that swung back and forth like a pendulum, and one that twisted in two directions.
What was interesting was that these two vibrations were synchronized and drove each other rather than cancelling each other out.
“This bimodal oscillation is like the Argentine tango, where each dancer must be perfectly synchronized with the other or they will trip over each other,” Yariv said in a press release. “The idea that such intertwined bimodal oscillations can be excited with a constant force has never been proposed or demonstrated before.”
The 90-year-old physicist spent the next few years devising a mathematical model that could explain this behaviour.
Standing on the shoulders of giants
Yariv discovered that to explain the vibrations he had to resort to a single-mode vibration model. Michael Faraday This model, subsequently mathematically explained by Lord Rayleigh, suggests that natural oscillations have a periodic force driving them.
To make it easier to understand, Yariv gives the example of a child on a swing who needs an outside force to stay on the swing. Typically, this force comes from a parent or a friend. But as the child grows, he or she learns to push the swing on their own, using their feet and body weight.
Returning to his bathroom on a hot afternoon in 2020, Yariv witnessed his showerhead vibrating due to the entangled cooperation of two vibration modes caused by the system’s nonlinearities.
As the showerhead begins to twist, the constant force of the water pushes back, creating a cyclical force that drives the pendulum motion, which in turn regulates the twisting motion of the showerhead at twice its frequency, as seen in the video above.
The mathematical model that describes this motion is called Yariv’s Groove, and it could explain why stop signs sway or suspension bridges sway on windy days. It could also have applications in civil engineering and green energy, helping us harness more energy. Wind Energy.
The research comes with a caveat: “My study tracks the system from the onset of bimodal vibration through the early stages of unstable vibration, only to stop it before the heavy showerhead blows a hole in the wall,” Yariv adds. press release“But the new entanglement bimodal oscillations are unstable. They don’t reach a steady state and just get bigger and bigger.”
The findings were published in the journal. PNAS.
About the Editor
Ameya Pareja Ameya is a science writer based in Hyderabad, India. He’s a molecular biologist at heart who put down his micropipette to write science during the pandemic, and he has no plans to go back. He loves writing about genetics, microbiology, technology, and public policy.
