Vibration overcomes gravity on a levitating fluid | Hacker News Reader

Vibration overcomes gravity on a levitating fluid

nature.com

37 pointsbencoder10 comments

This reminds me a bit of quadrupole ion (Paul) traps.

These confine charged particles using just electric fields. This is not possible with static fields (Earnshaw's theorem), but can be done with oscillating fields, even with sensors to determine the positions of the trapped ions.

https://en.wikipedia.org/wiki/Quadrupole_ion_trap

If I recall correctly, the principle was also illustrated in Feynman's lecture notes, where a vertical rod supported by a ball joint from the bottom is kept from tipping over by rapidly moving the joint up and down.

"even without sensors"

Vibration can, in principle, be used as a propulsion technology, no?[1]

> Woodward’s MEGA drive is different. Instead of propellant, it relies on electricity, which in space would come from solar panels or a nuclear reactor. His insight was to use a stack of piezoelectric crystals and some controversial—but he believes plausible—physics to generate thrust. The stack of crystals, which store tiny amounts of energy, vibrates tens of thousands of times per second when zapped with electric current. Some of the vibrational frequencies harmonize as they roll through the device, and when the oscillations sync up in just the right way, the small drive lurches forward.

[1] https://www.wired.com/story/mach-effect-thrusters-interstell...

That drive would need extensive testing, because it violates Newton's third law. Similar reactionless drives like the EM drive also warrant skepticism. Occam's razor, it's more likely the tests measuring their thrust were not accounting for a background element, even the article acknowledges this.

A levitating frog warrants even more skepticism, but it's levitating.

No, the levitating frog is exactly what you'd expect if you had a strong enough magnetic field.

https://www.ru.nl/hfml/research/levitation/diamagnetic-levit... "Lesson #1: Everything can levitate It is possible to levitate magnetically every material and every living creature on earth. Molecular magnetism is always present, although it is very weak and usually remains unnoticed. It might give you the impression that materials around us are mainly nonmagnetic. But this is not true. They are all magnetic. We call them ‘diamagnetic’. With magnetic fields high enough you can levitate all diamagnetic materials. At our lab, we develop and build magnets that have a very high magnetic fields. We use it to investigate molecules and materials. And show the world a levitating frog."

Previously: https://news.ycombinator.com/item?id=24362808

In the next few decades, we'll start seeing all kinds of crazy applications of vibration. There might be a physics and engineering revolution coming.

I have wondered about this too, after reading about other interesting experiments with vibrating oil droplets a few years ago.

https://www.sciencealert.com/these-bouncing-droplets-behave-...

My favorite example of these water experiments is sonoluminescence: a tank of water is driven by a high-frequency acoustic transducer to create a 3d standing wave, which forms a tiny bubble of air or other gas that, when collapsing, produces a burst of light.

That tiny burst of light is still an unsolved mystery. Despite it's trivially reproducible, there's still a range of competing theories that estimate the temperature of that bubble from 2,000K to 20,000K (some researchers add a few zeros there), and attribute the light to anything imaginable, including fusion and the Casimir effect. Quoting Wikipedia: "the rapidly moving interface between water and gas converts virtual photons into real photons."

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