Are Electric and Gravitational Fields Different for Moving Objects?

Click For Summary

Discussion Overview

The discussion revolves around the differences between electric and gravitational fields for moving versus stationary objects, particularly in the context of special relativity (SR). Participants explore the mathematical formulations of these fields and their behavior under different conditions, addressing both theoretical and conceptual aspects.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • One participant questions whether the electric field for a moving observer differs from that for a stationary observer, suggesting that the electric field increases as the distance decreases.
  • Another participant asserts that the electric field does change for moving charges and mixes with the magnetic field under Lorentz transformations, while also stating that there is no gravitation in special relativity.
  • A further reply challenges the claim that there is no gravitation in SR, arguing that forces can still be treated in SR regardless of their nature.
  • Another participant emphasizes that gravitation is not treated as a force in relativity and that assuming the gravitational field remains unchanged is problematic.
  • It is noted that special relativity considers inertial systems, which implies no forces or accelerations, but this is contested as a misconception, with some arguing that accelerated frames and forces can be addressed in SR.

Areas of Agreement / Disagreement

Participants express disagreement regarding the treatment of gravitational fields in special relativity and whether forces can be considered in accelerated frames. There is no consensus on the implications of these concepts.

Contextual Notes

Participants highlight limitations in understanding the nature of forces in relativity and the implications of treating gravitational fields in the context of special relativity. There are unresolved assumptions regarding the behavior of electric and gravitational fields under different conditions.

Silviu
Messages
612
Reaction score
11
Hello! I was wondering if the electric and gravitational fields are the same for a moving and a stationary object. The electric field (assume it is created by a stationary charge) is ##E = \frac{q}{\epsilon_0 4 \pi r^2}##, for a stationary observer, but it is higher for a moving one, as the r is getting smaller, while all the other are constant. Is this correct? For gravitational field, the formula would be ##G\frac{M}{r^2}##. The same reasoning can be applied here, only that in this case the mass M seems to increase. Are my reasoning correct? And if so, why does the electric and gravitational field behave differently, beside the math involved? Thank you!
 
Physics news on Phys.org
The electric field is not the same for a moving and for a stationary charge. Not only does the electric field change, it also mixes with the magnetic field under Lorentz transformations.

There is no gravitation in SR.
 
Orodruin said:
The electric field is not the same for a moving and for a stationary charge. Not only does the electric field change, it also mixes with the magnetic field under Lorentz transformations.

There is no gravitation in SR.
What do you mean by there is no gravitation in SR. You can still treat problems in SR when forces are involved. The nature of the force shouldn't matter, so it can be created by gravity, right?
 
Silviu said:
You can still treat problems in SR when forces are involved.
Gravitation is not a force in relativity. Forces in relativity need to be local as action at a distance would violate causality. You cannot go about just assuming that nothing will change with the gravitational field and it is best to keep away from all considerations of gravity in SR.'

On the other hand, classical electromagnetism (in the form of Maxwell's equations) is fully relativistically covariant. It is in fact one of the cornerstones in how relativity was conceived.
 
SR considers inertial systems. No force, no acceleration. Constant straight velocity.
 
Thuring said:
SR considers inertial systems. No force, no acceleration. Constant straight velocity.
This is not correct, but a common misconception among laymen. It is perfectly possible to work with accelerated frames and forces in SR.
 

Similar threads

  • · Replies 16 ·
Replies
16
Views
1K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 24 ·
Replies
24
Views
3K
  • · Replies 0 ·
Replies
0
Views
1K
  • · Replies 3 ·
Replies
3
Views
964
  • · Replies 14 ·
Replies
14
Views
3K
  • · Replies 18 ·
Replies
18
Views
2K
  • · Replies 23 ·
Replies
23
Views
3K
  • · Replies 3 ·
Replies
3
Views
1K