from Hacker News

Vibration overcomes gravity on a levitating fluid

by bencoder on 9/7/20, 9:29 AM with 10 comments

  • by pfdietz on 9/8/20, 2:10 AM

    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.

  • by georgewsinger on 9/8/20, 1:42 AM

    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...

  • by kencausey on 9/8/20, 12:23 AM

  • by ta1234567890 on 9/8/20, 12:42 AM

    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.

  • by vertbhrtn on 9/8/20, 8:11 AM

    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."