Does the universe has a capacitance?

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    Capacitance Universe
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Discussion Overview

The discussion revolves around the concept of whether the universe can be considered to have a capacitance, exploring the implications of permittivity and the expansion of the universe. Participants examine the theoretical underpinnings of capacitance in relation to cosmic scales.

Discussion Character

  • Exploratory, Conceptual clarification, Debate/contested

Main Points Raised

  • Some participants note that the units of permittivity of space can be expressed as farads per meter.
  • One participant questions whether multiplying the permittivity of free space (\(\epsilon_0\)) by the distance across the universe could yield a measure of universal capacitance, suggesting that this capacitance might change as the universe expands.
  • Another participant challenges the premise by stating that the universe does not have an electrically contiguous surface, arguing that without such a structure, the concept of universal capacitance is not valid.
  • A participant expresses uncertainty about the validity of the original question regarding the universe's capacitance, indicating it arose while trying to understand permittivity in the context of Gauss' Law.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the question of universal capacitance, with competing views presented regarding the applicability of capacitance to the universe.

Contextual Notes

The discussion highlights limitations in applying classical electrical concepts to cosmological scales, particularly regarding the assumptions about the universe's structure and properties.

shpongle
Does the universe has a capacitance?
 
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The units of permittivity of space can be written as farads/meter.
 
shpongle said:
The units of permittivity of space can be written as farads/meter.

so, do we multiply [itex]\epsilon_0[/itex] by the number of meters across the known universe (which might be something like [itex]c[/itex] times 13.7 billion years)? is the capacitance of the universe growing as the universe expands?
 
rbj said:
so, do we multiply [itex]\epsilon_0[/itex] by the number of meters across the known universe (which might be something like [itex]c[/itex] times 13.7 billion years)? is the capacitance of the universe growing as the universe expands?

That is what I meant.

I don't even know if it is a valid question but it occurred to me a few hours ago while I was trying to understand permittivity, which appears as a proportionality constant in the Gauss' Law.
 
No, because it does not have an electrically contiguous surface.

The capacitance of a thing defines its electrical potential given a state of charge on it. As the charge cannot distribute itself on any 'universal' structure (as no such structure exists), so there can be no 'universal' capacitance.
 

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