Surfing with electromagnetic waves

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Discussion Overview

The discussion revolves around the interaction of electromagnetic (EM) waves with charged objects, exploring concepts such as acceleration due to EM waves, reflection of EM waves, and the comparison of electromagnetic phenomena with gravitational effects. The scope includes theoretical and conceptual aspects of electromagnetism and optics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant proposes that a charged vehicle could be accelerated by a spherical wave propagating at the speed of light.
  • Another participant clarifies that electromagnetic waves are transverse and that the main acceleration would be sideways, with effective acceleration in the direction of the beam due to absorption or reflection.
  • A participant expresses confusion about the nature of EM waves, asking if they are solutions to Maxwell's equations and how they interact with particles to transfer momentum.
  • Responses indicate that EM waves can indeed transfer momentum and that reflection occurs due to interactions at the atomic level, with electrons absorbing and re-emitting energy.
  • There is a discussion about the limitations of classical electrodynamics in explaining optical phenomena and the necessity of quantum mechanics for a deeper understanding.

Areas of Agreement / Disagreement

Participants express varying levels of understanding regarding the interaction of EM waves and charged objects. There is no consensus on the sufficiency of classical electrodynamics to explain optics, with some arguing for the necessity of quantum mechanics while others seek more classical explanations.

Contextual Notes

Participants note limitations in classical explanations for atomic interactions and the need for effective theories like the refractive index. There is also an acknowledgment of the theoretical nature of gravitational wave detection and its comparison to electromagnetic phenomena.

HomogenousCow
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Let's say I have some source that generates a spherical wave that propagates outwards at the speed of light, and I have a vehicle that is charged.
The wave will accelerate my vehicle periodically and eventually bring it to great speeds.
Does this work?
 
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Spherical wave of what?
Electromagnetic waves are transversal - the main acceleration of your charged object would be sidewards, and changing its direction with the frequency of the electromagnetic wave.
The charged object would absorb or reflect some fraction of the wave, which gives an effective acceleration in the direction of the beam - but you do not need to charge the whole object, everything non-transparent will work. Solar sails use this concept.
 
hmm right.
Actually I'm a bit confused, could someone correct me if I'm wrong.
As i understand it, EM waves are just solutions to maxwells equations and they themselves interact with particles, transferring momentum in the form of a force?
And by the way, why do EM waves reflect off of surfaces? That has always bothered me.Gravity certainly does not reflect off of things, why electromagnetic waves?
 
As i understand it, EM waves are just solutions to maxwells equations

and they themselves interact with particles, transferring momentum in the form of a force?
They can do that.

And by the way, why do EM waves reflect off of surfaces?
As quantum mechanical description: Electrons (and sometimes other particles) can absorb the energy and re-emit it.
As classical description for metals: EM waves can lead to oscillations of electrons in the surface, those emit electromagnetic waves.

You cannot compare electromagnetic waves to gravity in that way. I think gravitational waves can be scattered in material - but gravity is so weak, we cannot even detect the waves themself with current experiments (might change in 2-3 years), so this is just a theoretic thing.
Gravity (as force between matter) does not reflect, and neither do electrostatic forces (as forces between charges)
 
I was hoping for a more elegant classical explanation..but I guess that makes sense.
So basically classical Electrodynamics is not enough to explain optics?
 
It cannot explain atoms or solid objects without effective theories (like a refraction index and so on). As soon as you want to understand that on a microscopic level, you need quantum mechanics.
 

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