Question on Michelson Morley experiment and length contraction

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Discussion Overview

The discussion revolves around the Michelson-Morley experiment and its implications for the concept of length contraction in the context of light propagation. Participants explore how length contraction might explain the null result of the experiment, as well as the historical context of ether theories and their evolution in light of experimental findings.

Discussion Character

  • Exploratory
  • Debate/contested
  • Technical explanation
  • Conceptual clarification

Main Points Raised

  • One participant seeks clarification on how length contraction relates to the null result of the Michelson-Morley experiment.
  • Another participant shares animations intended to aid understanding of the experiment and its implications.
  • Concerns are raised about whether the interference pattern would change if the light traveled at the same speed along both arms of the interferometer.
  • A participant presents a swimming analogy to illustrate the effects of relative motion on speed and distance, relating it to the concept of length contraction.
  • Some participants argue that the null result of the experiment suggests modifications to the understanding of light propagation, particularly in relation to ether theories.
  • Questions are posed about whether the non-changing interference pattern could be explained without invoking length contraction.
  • There is a discussion about the relationship between length contraction and the concept of ether, with some suggesting that early scientists' interpretations preserved ether concepts.
  • Clarifications are made regarding the use of "c" in equations, with some confusion about its representation as the speed of light versus a swimmer's speed.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the Michelson-Morley experiment for length contraction and ether theories. There is no consensus on whether length contraction is necessary to explain the null result or if alternative explanations could suffice.

Contextual Notes

Participants highlight the historical context of ether theories and the evolving understanding of light propagation. The discussion reflects varying interpretations of the experiment's results and the implications for modern physics.

  • #61
ghwellsjr said:
Even if this were true or even if it were false but you believed it to be true, it won't hamper you from learning relativity which is what this forum is for. I'm only interested in helping those people who want to learn about Special Relativity. Are you one of those people?

I am interested in learning about Special Relativity, and I appreciate your taking the time to go through it with me. For me though learning doesn't simply mean accepting what is said, it involves questioing it and challenging it so that it is understood; that includes challenging the assumptions of it.

As for the truth of the notion that time is a system of measurment and not a property, that is easily verified with some honest questioning.
 
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  • #62
mangaroosh said:
I would agree that the concept of time arose from observing such natural cycles, coupled with man's innate capacity for memory; but that is all time is, a concept.

EDIT: regardless of how the concept arose though, it doesn't support the contention that time is a property of the universe which can be measured; or that any kind of clock, natural or manmade, actually measures a property called time.

Everything that we measure relates to human concepts about nature. This is really philosophy, and although interesting, it's a bit off-topic here. You may be interested to read a philosophically oriented paper about special relativity, as you will probably appreciate the introduction:

The evolution of space and time, Langevin.
http://en.wikisource.org/wiki/The_Evolution_of_Space_and_Time
 
  • #63
harrylin said:
Everything that we measure relates to human concepts about nature. This is really philosophy, and although interesting, it's a bit off-topic here. You may be interested to read a philosophically oriented paper about special relativity, as you will probably appreciate the introduction:

The evolution of space and time, Langevin.
http://en.wikisource.org/wiki/The_Evolution_of_Space_and_Time

cheers, I'll give that a look.

It is essentially a philosophical consideration, because it is a philosophical assumption [apparently] inherent in the model. The difference between measurnig time and other concepts about nature is that other concepts about nature actually correspond to real things, which can be measured, time doesn't appear to be; that is, it is assumed to be, but when considered, it doesn't appear to be.
 
  • #64
ghwellsjr said:
I'm only interested in helping those people who want to learn about Special Relativity. Are you one of those people?
I am, ghwellsjr. hi, :smile:, and I hope you'll be patient with me, too!

If I may: "time" is a concept, an abstract idea (a *category) we need to describe only a dynamic world (being, entity, existing), if world were static, we would not need it (if absolute time would exist all the same, is a philosophical speculation, but we surely couldn't measure/perceive it)
so, we describe dynamic(ity), dynamism, or (choosing a common word) "change", we can measure change with every thing, phenomenon; it must not be repetitive, only regular, in order to be reliable. Motion, of course, is the obvious, patent phenomenon representing change[(of place], but we can use any invisible, internal phisical process as a "standard".
We measured "time-change" counting oscillation of a pendulum (gravity), measuring space, length, distance traveled by Sun etc, but also measuring mass, volume (water, sand) etc, now we measure "transitions ...of caesium", to-morrow who knows?
This is fundamental if we want to understand relativity: one standard of measurement doesn't and can't influence another standard. We do not measure time, not even change bu: space, mass etc.

(* "property, quality, attribute" has same ontological status as "time": category of being)

[If you allow me, I want to draw your attention to a problem similar to MM but in which length contraction doesn't help:
Imagine a platform and a train speeding N(orth) at 50 m/s. On both, a man pushes a ball (mass= x Kg) N. One ball moves at 51 the other at 1 m/s, N. The two men do same work? one ball gets 2500 times KE?]
EDIT: I know it doesn't regard SR and length contraction, I am presenting it just as a possibly interesting analogy with MM. I do not expect a reply
 
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  • #65
logics said:
[..]
If you allow me, I want to draw your attention to a problem similar to MM but in which length contraction doesn't help:
Imagine a platform and a train speeding N(orth) at 50 m/s. On both, a man pushes a ball (mass= x Kg) N. One ball moves at 51 the other at 1 m/s, N. The two men do same work? one ball gets 2500 times KE?
[..]

That doesn't fit in this topic, and it isn't specifically a problem of SR but the same in classical physics. Coincidentally it is a fresh topic there, so please comment in that thread:

https://www.physicsforums.com/showthread.php?t=534883

If next you have a question how the same works in SR (roughly the same), then please begin a topic on that here.
 
  • #66
harrylin said:
That doesn't fit in this topic..If next you have a question.
my note is not a question, just a "frame-of-reference analogy" hint, regarding [topic]MM experiment, my post, regards time.
 
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