Infinite range of E-M field vs finite age of particles

In summary: Yeah, I think that's it. As I said, I've always thought of the "infinite range" as just a mathematical fiction for all practical purposes, but then I'm an engineer, not a physicist.
  • #1

nomadreid

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It is said (hopefully no need to give references for such a common statement) that the electromagnetic field of a given charged particle is infinite in range (albeit converging to zero as the distance goes to infinity). However, given that charged particles apparently did not exist at the beginning of the expansion of the universe, and that the electric field expands at the speed of light modulo being carried along by the expansion, that the field would be finite? (I am assuming the universe having started out as already very large, possibly infinite.)
 
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  • #2
I believe that the "infinite extent" of charged particles' electromagnetic fields as well as that of the gravitational field of massive bodies are Classical Physics statements (and therefore assume a static space-time)
 
  • #3
The field is actually the fundamental object in modern physics, not the particles. So the field existed before the particles.
As a technical note, particles are modeled as excitations of their underlying fields in modern quantum theory (specifically quantum field theory). So photons are excitations of the EM field, electrons are excitations of an electron field, etc.
 
  • #4
Drakkith said:
The field is actually the fundamental object in modern physics, not the particles. So the field existed before the particles.
As a technical note, particles are modeled as excitations of their underlying fields in modern quantum theory (specifically quantum field theory). So photons are excitations of the EM field, electrons are excitations of an electron field, etc.
While I agree w/ what you say, I still think that the "infinite extent" is a Classical Physics statement (and in practical terms is just a mathematical convenience anyway)
 
  • #5
Drakkith said:
The field is actually the fundamental object in modern physics, not the particles. So the field existed before the particles.
As a technical note, particles are modeled as excitations of their underlying fields
From what I understand (which is too little), the field of which a particle is the excitation of is distinguished from the field which is the object of the effect (attraction/repulsion) of one charged and/or massive particle on other (test) particles in space. The former is infinite, but I am referring to the latter.

phinds said:
the "infinite extent" of charged particles' electromagnetic fields as well as that of the gravitational field of massive bodies are Classical Physics statements (and therefore assume a static space-time)
And hence invalid, so my idea about a finite field is not off the mark?
 
  • #6
nomadreid said:
And hence invalid, so my idea about a finite field is not off the mark?
If it is "invalid" I think it is only "invalid" in the same sense that Newtonian Gravity is invalid. They both work just fine except in extreme cases.
 
  • #7
phinds said:
If it is "invalid" I think it is only "invalid" in the same sense that Newtonian Gravity is invalid. They both work just fine except in extreme cases.
In other words, an E-M field emanating from an electron is "infinite for all practical purposes", i.e., very big (albeit finite, if one wishes to get picky)?
 
  • #8
nomadreid said:
In other words, an E-M field emanating from an electron is "infinite for all practical purposes", i.e., very big (albeit finite, if one wishes to get picky)?
Yeah, I think that's it. As I said, I've always thought of the "infinite range" as just a mathematical fiction for all practical purposes, but then I'm an engineer, not a physicist.
 
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1. What is an "Infinite range" of an electromagnetic field?

An infinite range of an electromagnetic field refers to the fact that electromagnetic waves can propagate through space indefinitely without losing their energy or intensity. This means that the effects of an electromagnetic field can be felt at any distance from its source, potentially reaching across the entire universe.

2. How is the infinite range of an electromagnetic field related to the finite age of particles?

The infinite range of an electromagnetic field is related to the finite age of particles because it means that the effects of an electromagnetic field can potentially reach particles that have been in existence for a finite amount of time. This also means that the particles themselves can be affected by the electromagnetic field, either through absorption, reflection, or interaction.

3. How does the infinite range of an electromagnetic field affect the behavior of particles?

The infinite range of an electromagnetic field can affect the behavior of particles in several ways. For example, particles can be accelerated or decelerated by an electromagnetic field, they can emit or absorb photons, or they can be deflected by strong electric and magnetic fields. This means that the infinite range of an electromagnetic field can significantly impact the motion and interactions of particles.

4. Is there a limit to the range of an electromagnetic field?

Technically, there is no limit to the range of an electromagnetic field. However, the strength of the field decreases as the distance from its source increases, eventually becoming so weak that its effects are negligible. This means that although the range may be infinite, the actual impact of the field decreases with distance.

5. How does the concept of infinite range of an electromagnetic field relate to the theory of relativity?

The concept of an infinite range of an electromagnetic field is consistent with the theory of relativity, which states that the laws of physics should remain the same regardless of the observer's reference frame. This means that the effects of an electromagnetic field, including its range, should be the same for all observers, regardless of their relative motion. Additionally, the theory of relativity also explains how electromagnetic fields travel at the speed of light, allowing for their seemingly infinite range.

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