Absolute Maxwellian acceleration?

  • Context: Graduate 
  • Thread starter Thread starter HarryWertM
  • Start date Start date
  • Tags Tags
    Absolute Acceleration
Click For Summary

Discussion Overview

The discussion revolves around the concept of acceleration as it relates to electromagnetic fields, specifically in the context of two spaceships, one charged and one uncharged. Participants explore whether it is possible to determine which craft is accelerating based solely on measurements of electric and magnetic fields, without referencing other physics frameworks such as Newtonian or Einsteinian mechanics.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant proposes a thought experiment involving two spaceships, questioning if electromagnetic field measurements can distinguish which craft is accelerating.
  • Another participant states that an accelerated charge will radiate, but emphasizes that radiation is only observed from differently accelerating frames.
  • A different viewpoint suggests that if the electric field of a point charge deviates from the expected Coulombic shape, it indicates acceleration of the observer's craft.
  • One participant presents two tests comparing the electromagnetic fields measured by an observer craft and a charged craft, questioning if the fields will match under identical acceleration conditions.
  • Another participant asserts that one can always tell if they are accelerating by feeling a force, and notes the limitation of measuring fields from a specific object.
  • A later reply claims that acceleration is absolute within relativity theory, suggesting that the accelerated charge will radiate energy while the unaccelerated one will not.

Areas of Agreement / Disagreement

Participants express differing views on the nature of acceleration and its relationship to electromagnetic radiation, with no consensus reached on whether the fields measured in the proposed tests will match or on the implications of acceleration in this context.

Contextual Notes

Participants acknowledge limitations in measuring specific fields and the dependence on the observer's frame of reference, highlighting unresolved aspects of the thought experiments presented.

HarryWertM
Messages
99
Reaction score
0
This recent thread:
https://www.physicsforums.com/showthread.php?t=386121"
leads me to the following thought experiment:

Your spaceship flies by another spaceship which appears to be highly electrically charged. From measurement of E and B fields on board your craft, you conclude that either you or the other craft is accelerating. Without referencing any other physics besides Maxwell, can you tell which craft is accelerating? That is, you do not use any Newtonian or Einsteinian or galactic far field acceleration measurements. Only EM field measurements.
 
Last edited by a moderator:
Physics news on Phys.org
An accelerated charge will radiate...
 
jrlaguna said:
An accelerated charge will radiate...

Accelerating charges only radiate when viewed from differently accelerating frames.
Two charges side-by-side, accelerating together do not cause radiation fields to appear against one another.

The way to tell is (for example) to map the electric field of a point charge in your ship. If it deviated from the basic Coulombic shape, then you are accelerating. Put a different way, gravity and acceleration deform electric and magnetic lines of force the same way as they change the trajectory of a moving ball. If your ball doesn't move in a strait line, you ship is accelerating or is in gravity.
 
Ah, thank you. Now I know what I was trying to ask.

Two thought experiments. In both cases we have two space craft,. One is highly charged with a static electrical charge. The second, uncharged, craft is the observer. The two fly by each other. The observer craft measures ONLY the electromagnetic fields generated by the OTHER craft's passage, even though it obviously could do other measures. The observer measures the exterior E and B over a suitable time period.

Test 1: The charged craft flies by while accelerating at a constant rate. The observer does not accelerate.

Test 2: The observer craft flies by while accelerating at a constant rate. The charged craft does not accelerate.

Question: For identical rates of acceleration, will the the fields measured in Test 1 match the fields in Test 2?
 
First, you can always tell if you are accelerating. You feel a force.

Second, it's not possible to build a device that measures the fields from a specific object. One can measure only the total fields.
 
Acceleration is absolute, at least within relativity theory (both special and general) and therefore, electromagnetism. The accelerated charge will lose energy through radiation, the other one will not. @Antiphon: an accelerated dipole radiates too.
 

Similar threads

Undergrad 3 clocks thought experiment - Absolute vs. relative aspects?
  • · Replies 50 ·
2
Replies
50
Views
5K
Graduate Voltage and current waves in a transmission line
  • · Replies 4 ·
Replies
4
Views
3K
Undergrad Is acceleration a more absolute/fundamental quantity in the universe?
  • · Replies 16 ·
Replies
16
Views
2K
Graduate Electron speed and acceleration in an electric field
  • · Replies 9 ·
Replies
9
Views
5K
Graduate Weyl tensor and coordinate acceleration
  • · Replies 12 ·
Replies
12
Views
3K
Undergrad Can a Gyroscope in a Satellite Detect Orbit?
  • · Replies 51 ·
2
Replies
51
Views
7K
High School Realistic Window View from a Starship: Gravity, Rotation, and Blue/Red Shifting
  • · Replies 22 ·
Replies
22
Views
2K
Undergrad How do you get to the conclusion that there is accelerating expansion?
  • · Replies 23 ·
Replies
23
Views
4K
Undergrad Is acceleration absolute or relative - follow up
  • · Replies 38 ·
2
Replies
38
Views
4K
Undergrad Non-Inertial Relativistic Dynamics
  • · Replies 18 ·
Replies
18
Views
2K