A 150-year-old theory about the other form proposed by Lord Kelvin, one of history’s greatest physicists, has finally been tested – and his guess is now in doubt.
In 1871, William Thomson, better known as Lord Kelvin – a famous British physicist who made major contributions to the electromagnetic theory, ThermodynamicsNavigation and launcher temperature The system that bears his name – he proposed a theory about a strange hypothetical shape, which he called an isotropic helical.
The shape resembles a sphere with a number of fins protruding from its surface and appears symmetric (isotropic) from any angle. Kelvin believed that if immersed in water and allowed to sink, the helicoid should rotate like a small fan.
Related: The funniest theories in physics
But a new experiment led by two physics professors – Greg Voth of Wesleyan University in Connecticut and Bernard Muhlig of the University of Gothenburg in Sweden – has cast doubt on Kelvin’s predictions. By 3D-printing five helical materials of different properties according to Kelvin’s instructions and then dropping them into silicone oil, the team discovered that the shapes did not rotate because they fell after all.
According to Voth, the 150-year lag between Kelvin’s theory and the recorded experiment to test it may have been the result of deliberate omissions by later scientists and even Kelvin himself. It is possible that Kelvin created the concept of the spiral to better understand one of his earlier theories: the vortex theory in corn. The theory – which depicts atoms as stable, complex vortices in a cosmic medium known as the aether – has long been discredited.
But when the experiment didn’t work, Kelvin may have quietly abandoned it, Voth speculated.
“In Kelvin’s manuscript, he explicitly describes how to fabricate isotropic helical properties, including the materials used, which suggests that he invented one,” Voth told Live Science. “I personally suspect that Kelvin and others have since synthesized anisotropic helicals and noted that the measured translation-spin coupling is determined by limitations on fabrication quality, and therefore, have not published their measurements.”
To find out what exactly was going on to make their experiment confounding Kelvin’s predictions, the team analyzed how the fluid in their tank flowed around the helicopter.
They found that Kelvin was indeed right – there was a coupling, or relationship, between helical motion through a fluid and its rotation. When the shape sinks through silicone oil, the friction Caused by the particles of oil flowing around the body of the figure, directed from one helioid propeller to the next, must cause it to be subjected to a force that causes it to rotate, and the faster it falls, the faster it must rotate.
But the coupling between motion and rotation was too weak to have an obvious scaling effect or for the helices to spin at all as they moved. Kelvin allowed the theory, but he may have exaggerated the strength of the effect.
According to the researchers, this may be because only a few fins, or quills, on the helicoid interact by directing the flow of fluid into each other – and this is not enough to turn the helicoid.
Now that they’ve evaluated how the helixes spin (or don’t spin) in a real experiment, the researchers plan to create a new helix with precise fabrication techniques to remove any defects. They also want to modify the Kelvin design to amplify any coupling between motion and rotation. If they succeed, they can finally prove Kelvin correct after all.
“We will continue to search for potential forms that would increase the coupling,” Voth said. “Theoretical and computational guidance of the shapes to be fabricated will be essential, as the precise fabrication of these complex 3D shapes is a challenge.”
The researchers published their findings on July 13 in the journal physical revision fluids.
Originally published on Live Science.