The 150-year-old theory of the shape of another world proposed by Sir Kelvin, one of the greatest physicists in history, has finally been tested — and his speculation is now questionable.
1871, William Thomson, more commonly known as Sir Kelvin — a well-known British physicist and electromagnetic hypothesis, thermodynamics, Navigation and absolute temperature His eponymous system — proposed a theory of strange virtual shapes that he called isotropic helicoids.
The shape resembles a sphere with a large number of fins protruding from the surface and looks the same (isotropic) from any angle. Kelvin believed that the helicoid would rotate like a small propeller if it could be submerged in water.
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However, a new experiment led by two professors of physics (Greg Voth at Wesleyan University in Connecticut and Bernhard Mehlig at Gothenburg University in Sweden) questioned Kelvin’s predictions. The team found that by 3D printing five different isotropic helicoids according to Kelvin’s instructions and dropping them into silicone oil, they eventually did not rotate when the shape fell.
According to Voss, the 150-year delay between Kelvin’s theory and the recorded experiments to test it may have been the result of intentional omissions by later scientists and Kelvin himself. .. It is possible that Kelvin devised the concept of helicoids to better understand one of his early theories, the vortex theory. atom.. The theory of describing an atom as a stable knotted vortex in a space medium known as ether has long been unreliable.
But when the experiment went wrong, Kelvin might have quietly abandoned it, Voss speculated.
“Kelvin’s manuscript clearly describes how to make an isotropic helicoid, including the materials used, suggesting that he created it,” Voth told Live Science. “I personally did not publish the measurements because I observed that the measured translational-rotational bond was determined by the quality limits of the production since Kelvin et al. Manufactured the isotropic helicoid. I doubt. “
To get an accurate picture of what was happening to confuse Kelvin’s predictions in the experiment, the team analyzed how the fluid in the tank flows around the helicoid.
They found that Kelvin was actually correct — there was a bond or relationship between the movement of the helicoid through the fluid and its rotation. As the shape sinks through the silicone oil friction Caused by particles of oil flowing around the body of the shape, which are guided from one fan of the helicoid to the next, they generate a force that rotates the helicoid, and the faster it falls, the faster it spins.
However, the bond between movement and rotation was so weak that it could not have a clearly measurable effect or rotate at all when the helicoid moved. Kelvin nailed the theory, but he may have exaggerated the strength of the effect.
According to researchers, this may be because only a small portion of the fins or vanes on the helicoid interact by directing the flow of fluid to each other-not enough to rotate the helicoid.
Having evaluated how the helicoid rotates (or does not rotate) in real-world experiments, researchers plan to create a new helicoid with precision manufacturing techniques to remove defects. I also want to tweak the Kelvin design to amplify the coupling between movement and rotation. If they succeed, in the end, they can finally prove Kelvin.
At that point, “we will continue to look for shapes that have the potential to increase coupling,” Voth said. “The exact fabrication of these complex 3D shapes is difficult, so theoretical and computational guidance for the shapes to be manufactured is essential.”
Researchers published their findings in the journal on July 13th Physical Review Fluid..
Originally published in Live Science.
Was Sir Kelvin wrong? The 3D-printed shape casts doubt on his 150-year-old theory.
Source link Was Sir Kelvin wrong? The 3D-printed shape casts doubt on his 150-year-old theory.