Permittivity, permeabiltiy and gravity

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    Gravity Permittivity
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Discussion Overview

The discussion revolves around the relationship between permittivity, permeability, and the speed of gravity, exploring whether these electromagnetic properties influence gravitational fields. Participants express confusion and curiosity regarding the implications of these concepts in theoretical physics.

Discussion Character

  • Exploratory
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • One participant notes that the speed of light is constrained by permittivity and permeability, questioning why these properties would also affect the speed of gravity, given that electric and magnetic fields do not seem to influence gravitational fields.
  • Another participant asserts that any massless relativistic wave, including electromagnetic waves, travels at the speed of light, while suggesting that if a photon had mass, its speed would be less than that of light, linking this to the de Broglie relations.
  • A participant requests clarification on who claims that permittivity and permeability constrain the speed of gravity.
  • In response, another participant references various claims made by individuals regarding this topic and provides links to Wikipedia entries for further context.
  • One participant describes the notion of permittivity and permeability affecting gravity as "fringe physics."
  • Another participant argues that without context, the question is difficult to understand, but states that electromagnetic fields have a non-vanishing energy momentum tensor that produces a gravitational field, suggesting a coupling between electromagnetic and gravitational fields.

Areas of Agreement / Disagreement

The discussion contains multiple competing views, with participants expressing differing opinions on the relationship between electromagnetic properties and gravity, and no consensus has been reached.

Contextual Notes

Participants express confusion and uncertainty regarding the implications of permittivity and permeability on gravity, and the discussion includes references to external sources that may not be universally accepted.

Chronos
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The speed of light is theoretically constrained by the pemittivity and permeability of the medium through which it travels. It seems counterintuitive that pemittivity and permeabilty also constrain the speed of gravity since neither electric or magnetic fields appear to have any influence on gravitational fields. My apologies if this sounds like a cranky question, but, it has me confused - which is not necessarily a difficult accomplishment.
 
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Any massless relativistic free wave, electromagnetic or not, will travel at "the speed of light".

If the photon has mass, it will travel at less than "the speed of light". (Actually, its speed will depend on its wavelength, that is the meaning of "mass" applied to waves. The relation of the "mass" of a wave to the mass of a particle is via the de Broglie relations.)
 
Last edited:
Chronos said:
T It seems counterintuitive that pemittivity and permeabilty also constrain the speed of gravity since neither electric or magnetic fields appear to have any influence on gravitational fields.
Who claims this to be the case?
 
"Fringe physics" is an apt description.
 
Ok, without a context, the question is hard to understand. But magnetic and electric fields have a non-vanishing energy momentum tensor which produces a gravitational field. So electromagnetic and gravitational fields are coupled.
 

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