Some version of the Hula-Hoop has been around for millennia, but the popular plastic version was introduced by Wham-O in the 1950s and quickly became a fad. Now, researchers have taken a closer look at the underlying physics of the toy, revealing that certain body types are better at keeping the spinning hoops elevated than others, according to a new paper published in the Proceedings of the National Academy of Sciences.

“We were surprised that an activity as popular, fun, and healthy as hula hooping wasn’t understood even at a basic physics level,” said co-author Leif Ristroph of New York University. “As we made progress on the research, we realized that the math and physics involved are very subtle, and the knowledge gained could be useful in inspiring engineering innovations, harvesting energy from vibrations, and improving in robotic positioners and movers used in industrial processing and manufacturing.”

Ristroph's lab frequently addresses these kinds of colorful real-world puzzles. For instance, in 2018, Ristroph and colleagues fine-tuned the recipe for the perfect bubble based on experiments with soapy thin films. In 2021, the Ristroph lab looked into the formation processes underlying so-called "stone forests" common in certain regions of China and Madagascar.

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Emergent gravity is a bold idea.

It claims that the force of gravity is a mere illusion, more akin to friction or heat—a property that emerges from some deeper physical interaction. This emergent gravity idea might hold the key to rewriting one of the fundamental forces of nature—and it could explain the mysterious nature of dark matter.

But in the years since its original proposal, it has not held up well to either experiment or further theoretical inquiry. Emergent gravity may not be a right answer. But it is a clever one, and it's still worth considering, as it may hold the seeds of a greater understanding.

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A little more than a year ago, a snippet of video that wasn't supposed to go public made its way onto United Launch Alliance's live broadcast of an Atlas V rocket launch carrying three classified surveillance satellites for the US Space Force and the National Reconnaissance Office.

On these types of secretive national security missions, the government typically requests that the launch provider stop providing updates on the ascent into space when the rocket jettisons its two-piece payload fairing a few minutes after launch. And there should be no live video from the rocket released to the public showing the fairing separation sequence, which exposes the payloads to the space environment for the first time.

But the public saw video of the clamshell-like payload fairing falling away from the Atlas V rocket as it fired downrange from Cape Canaveral, Florida, on September 10, 2023. It wasn't pretty. Numerous chunks of material, possibly insulation from the inner wall of the payload shroud's two shells, fell off the fairing. The video embedded below shows the moment of payload fairing jettison.

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