Speed of Light: Michelson-Morley Experiment Revisited

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In summary, the conversation discusses the results of the Michelson-Morley experiment and its implications for the speed of light in different conditions. It is concluded that while the Earth has an atmosphere, the speed of light remains isotropic while in motion, but if the Earth does not have an atmosphere, the speed of light is constant for all observers. The conversation also mentions the Fizeau experiments and the debate surrounding the concept of ether-dragging. Finally, it is mentioned that the experiments have been repeated in a vacuum, but the conversation is then locked.
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If we assume that:
  • the Earth has an atmosphere
  • the Michelson-Morley experiment measured an isotropic speed of light inside the atmosphere
We can conclude that the speed of light inside the atmosphere remains isotropic while the Earth is moving through space.

But if we assume that:
  • the Earth does not have an atmosphere
  • the Michelson-Morley experiment measured an isotropic speed of light in space (from the surface of the earth)
We can conclude that the speed of light is constant/isotropic for all observers, irrespective of their motion.

The fact of the matter is, the Earth does have an atmosphere.
Do you see where this is going?
 
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No.
 
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x-vision said:
Do you see where this is going?
Given the number of experiments with light in a vacuum (edit: and Fizeau's experiments which measure the "drag" effect of a medium) of which you are apparently ignorant, towards a thread lock I suspect.
 
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edit: and Fizeau's experiments which measure the "drag" effect of a medium
Aha. Have you considered that the Fizeau and the Michelson-Morley experiments are actually equivalent?
Both measured the speed of light in a moving optical medium but did it differently:
  • Fizeau measured the speed of light as light passes through the moving medium (water)
  • Michelson-Morley measured the speed of light inside the moving medium (the atmosphere)
Fizeau measured a partial "drag" effect, whereas Michelson-Morley measured a full "drag".
The accuracy of the Michelson-Morley was vastly superior (1200+ times better).

The point is, you can't really conclude that the speed of light is constant for all observers if you are aware that the MM experiment measured the speed of light inside the atmosphere.

Not looking to pick a fight here. Just pointing out the obvious.
Best regards
 
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x-vision said:
If we assume that:
  • the Earth has an atmosphere
  • the Michelson-Morley experiment measured an isotropic speed of light inside the atmosphere
We can conclude that the speed of light inside the atmosphere remains isotropic while the Earth is moving through space.

But if we assume that:
  • the Earth does not have an atmosphere
  • the Michelson-Morley experiment measured an isotropic speed of light in space (from the surface of the earth)
We can conclude that the speed of light is constant/isotropic for all observers, irrespective of their motion.

The fact of the matter is, the Earth does have an atmosphere.
Do you see where this is going?
You can do the experiment in a vacuum chamber.
 
  • #6
x-vision said:
Just pointing out the obvious.
Meta-question: if it's obvious to you, do you really think it would have been missed by the entire physics community for more than a century? You are talking about an ether-dragging model, effectively. Between stellar aberration experiments, Michelson-Morley and Fizeau (not to mention interferometry done in a vacuum), all such models (partial and complete dragging) were ruled out decades ago.
x-vision said:
Fizeau measured a partial "drag" effect, whereas Michelson-Morley measured a full "drag".
Evidence for this claim...?
 
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Meta-question: if it's obvious to you, do you really think it would have been missed by the entire physics community for more than a century?
Yup. That's exactly what I'm thinking ;).
 
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x-vision said:
Yup. That's exactly what I'm thinking ;).
And that you wish to continue to think this is why you don't acknowledge the point about people repeating the experiment in vacuum, and why you offer no evidence for your partial/full dragging claim about the Fizeau experiment.
 
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  • #9
IBTL

Ibix said:
people repeating the experiment in vacuum

Georg Joos, in the 1920's.
 
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x-vision said:
Yup. That's exactly what I'm thinking ;).
Suffice to say, that's an unreasonable thing to think. There's ample documentation of light speed experiments (MM and other) conducted in a vacuum if you choose to look at them.

The question is adequately answered, thread locked.
 
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FAQ: Speed of Light: Michelson-Morley Experiment Revisited

1. What is the Michelson-Morley experiment?

The Michelson-Morley experiment was a scientific experiment conducted in the late 19th century by Albert Michelson and Edward Morley to measure the speed of light. It involved using a device called an interferometer to compare the speed of light in different directions, in order to detect any differences caused by the Earth's motion through the hypothetical "ether" medium.

2. What were the results of the Michelson-Morley experiment?

The results of the Michelson-Morley experiment were surprising and unexpected. They found that the speed of light was the same in all directions, regardless of the Earth's motion. This contradicted the prevailing theory at the time, which stated that the speed of light should be affected by the Earth's motion through the ether. This result was a major breakthrough in the understanding of light and paved the way for Einstein's theory of relativity.

3. How did the Michelson-Morley experiment impact our understanding of the speed of light?

The Michelson-Morley experiment revolutionized our understanding of the speed of light. It showed that the speed of light is constant, regardless of the observer's frame of reference. This led to the development of Einstein's theory of relativity, which states that the laws of physics are the same for all observers in all inertial frames of reference.

4. Why is the Michelson-Morley experiment considered a crucial experiment in the history of science?

The Michelson-Morley experiment is considered a crucial experiment in the history of science because it challenged the prevailing theories of the time and led to a major shift in our understanding of the nature of light and the laws of physics. It also paved the way for further groundbreaking discoveries and advancements in physics.

5. How does the Michelson-Morley experiment continue to impact scientific research today?

The Michelson-Morley experiment continues to have a significant impact on scientific research today. It has been replicated and refined numerous times, leading to even more precise measurements of the speed of light and further confirmation of the principles of relativity. It also serves as a reminder of the importance of questioning and challenging established theories in order to advance our understanding of the world.

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