Five Proven Methods of Levitation

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Recorded: 2017/03/05 Published: 20017/10/21
Randy shows Jim five different ways in which a body can be levitated: by magnetism, by superconductors, by Lenz' Law, by acoustics, and most recently by thermophoresis.

1. The particular magnetic levitation we talk about is diamagnetic.  A very, very large magnetic field induces a large magnetic moment in an object as a reaction.  If the diamagnetic component of the object's magnetic susceptibility is larger than its paramagnetic component, the resulting magnetic moment will oppose the field.
Superconductors also expel magnetic fields from their body by the Meissner effect, which makes a "perfect dielectric."  This allows the superconductor to levitate.
2. Using Lenz' Law, eddy currents that are induced by time-varying electric fields produce magnetic fields that react with their source, levitating the object.
3. Acoustic levitation occurs when standing sound waves are set up in a region, providing areas where particles can levitate.
4. Optical traps work in a similar way to acoustic levitation with electromagnetic fields instead of pressure fields.
5. Thermophoretic levitation occurs when temperature gradients produce a force that allows small object to float.

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Notes:

1. The papers we read for this program:

• Brandt, E.H., "Levitation in Physics." Science 243 349 (1989).
• Zuza, Fuisasola, Michelini, and Sani, "Rethinking Faraday's Law for Teaching Motional Electromotive Force."  European Journal of Physics 33 397 (2012).
• Brandt, E.H., "Suspended by Sound." Nature 413 474 (2001).
• Ashkin, A., "Optical Trapping and Manipulation of Neutral Particles Using Lasers." Proceedings of the National Academy of Sciences 94 4853 (1997).
• Fung, Usatyuk, DeSalvo, and Chin, "Stable Thermophoretic Trapping of Generic Particles at Low Pressures." Applied Physics Letters 110 034102 (2017). [arXiv]

2. Videos of levitating objects:

• Levitating Frog
• Superconducting Levitation
• Lenz' Law
• Acoustic Levitation
• Optical Tweezers
• Thermophoretic Leviatation

3. Our subreddit.

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Stochastic Electrodynamics

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Recorded: 2017/02/11 Published: 2017/10/04

Is the entire cosmos awash in a sea of invisible energy? Nikola Tesla thought so. And today a few daring theoretical physicists are pioneering the effort to explain the most exotic characteristics of quantum theory by describing the nature of this universal field of energy and its physical consequences. If they’re right, their theory could revolutionize the energy and transportation sectors around the globe, and perhaps even throw open the door to new forms of spaceflight. On this episode of Physics Frontiers, we’ll investigate the theory of stochastic electrodynamics, one of the most intriguing concepts in modern physics and a rising contender to explain the quantum world.

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Notes:

1. The main paper we read for this program: Contribution from Stochastic Electrodynamics to the Understanding of Quantum Mechanics by de la Peña and Cetto [arXiv]
2. The secondary paper we mentioned in program, predicting spontaneous parametric up-conversion: Non-Locality: The Party May Be Over by Marshall [arXiv]

3. Our subreddit.

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