Two ways of detecting absolute motion

  • Context: Graduate 
  • Thread starter Thread starter avito009
  • Start date Start date
  • Tags Tags
    Absolute Motion
Click For Summary

Discussion Overview

The discussion revolves around the concept of absolute motion and the methods proposed for its detection, specifically through measurements related to light and inertial effects. Participants explore the implications of the Michelson-Morley experiment and Einstein's special theory of relativity in this context.

Discussion Character

  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that absolute motion could be detected by measuring motion with respect to a beam of light or through inertial effects during acceleration.
  • One participant questions the validity of detecting absolute motion, stating that all motion is relative, thus challenging the premise of absolute motion.
  • Another participant argues that special relativity did not prove the constancy of the speed of light but rather started with the assumption that it is constant, citing experimental evidence and consistency with established laws of electricity and magnetism.
  • It is noted that acceleration cannot be used to detect absolute motion due to Newton's laws, which state that the effects of acceleration are the same regardless of the state of motion.
  • One participant reiterates the claim that special relativity implies the speed of light remains constant across all reference frames, leading to the conclusion that using light as a reference will always yield the speed of light.

Areas of Agreement / Disagreement

Participants express differing views on the nature of absolute motion and the implications of special relativity, indicating that multiple competing perspectives remain unresolved.

Contextual Notes

There are limitations regarding the assumptions made about absolute motion and the definitions of motion and acceleration, which are not fully explored in the discussion.

avito009
Messages
184
Reaction score
4
There are two ways by which absolute motion might be detected: by measuring motion with respect to a beam of light, and by making use of inertial effects that arise when an object is accelerated. So why MichelsonMorley experiment showed the first method to be unworkable? Einstein's special theory of relativity explained why.

Correct me if I am wrong. Special relativity proved that no matter the position or speed with which a person is moving, the speed of light will be the same. Is this correct? otherwise how does SR prove that the first method is unworkable?
 
Physics news on Phys.org
Absolute motion relative to what? That's not a joke; all motion is relative.
 
Special relativity didn't prove that the speed of light is the same, it started with the assumption (Einstein's second postulate) that it was.

We choose to make this assumption because:
- It agrees with all the experimental evidence we have (including the Michelson-Morley experiment).
- It is consistent with the laws of electricity and magnetism, which were solidly established more than a half-century before the discovery of relativity.
- The conclusions that follow from that assumption can be tested, and when we test them they are confirmed.

That doesn't mean that it's right, but it does mean that any alternative that doesn't do all of the above has to be wrong.
 
  • Like
Likes   Reactions: PeroK
avito009 said:
There are two ways by which absolute motion might be detected: by measuring motion with respect to a beam of light, and by making use of inertial effects that arise when an object is accelerated.
You can't use acceleration detect absolute motion because per Newton's first and second Laws of Motion, acceleration works the same regardless of your current state of motion.
 
avito009 said:
There are two ways by which absolute motion might be detected: by measuring motion with respect to a beam of light, and by making use of inertial effects that arise when an object is accelerated. So why MichelsonMorley experiment showed the first method to be unworkable? Einstein's special theory of relativity explained why.

Correct me if I am wrong. Special relativity proved that no matter the position or speed with which a person is moving, the speed of light will be the same. Is this correct? otherwise how does SR prove that the first method is unworkable?

Since the speed of light is the same in any reference frame measuring your speed using it as a reference will always produce: ta-da, the speed of light.
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
1K
  • · Replies 57 ·
2
Replies
57
Views
4K
  • · Replies 16 ·
Replies
16
Views
2K
  • · Replies 7 ·
Replies
7
Views
2K
  • · Replies 10 ·
Replies
10
Views
3K
  • · Replies 34 ·
2
Replies
34
Views
4K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 38 ·
2
Replies
38
Views
4K
  • · Replies 6 ·
Replies
6
Views
2K
  • · Replies 19 ·
Replies
19
Views
10K