Michelson-Morley Exp: Surprise of Result

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Discussion Overview

The discussion revolves around the surprising results of the Michelson-Morley experiment, particularly focusing on the implications of the experiment's null result and the concept of ether as a medium for light. Participants explore analogies with sound experiments and the effects of motion on wave propagation, examining the differences between classical ether theories and modern understandings.

Discussion Character

  • Debate/contested
  • Conceptual clarification
  • Technical explanation

Main Points Raised

  • Some participants suggest that if the mirrors were on Earth, the system behaves like a Galilean system, implying that the result should be the same regardless of Earth's motion.
  • Others argue that the analogy of sound experiments, particularly in a supersonic jet, illustrates why the null result was surprising, as they expected the motion through the ether to affect the results.
  • A participant questions the validity of the sound analogy, suggesting that if sound originates inside the jet, its behavior would not depend on the jet's motion.
  • Another participant clarifies that the classical ether was thought to permeate the universe and that the Earth moves through it, which should affect light speed measurements.
  • Some participants discuss the aether drag hypothesis, noting that if ether were dragged along with the Earth, it would lead to observable refractive effects that have not been detected.
  • There is a mention of Fizeau's experiments, which indicated that ether would not be affected by walls and must penetrate matter, complicating the ether hypothesis.
  • One participant concludes that the ether hypothesis does not hold up against astronomical observations, suggesting a need to abandon Newtonian concepts.

Areas of Agreement / Disagreement

Participants express differing views on the implications of the Michelson-Morley experiment and the nature of ether. There is no consensus on the validity of the ether hypothesis or the analogies used to explain the experiment's results.

Contextual Notes

Participants reference the aether drag hypothesis and its implications, as well as the differences between sound and light propagation in various media. The discussion highlights unresolved assumptions about the nature of ether and its effects on light.

Paulo Figueiredo
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Hello!
Why the surprise in the result of the Michelson-Morley experiment?
If the mirrors were in earth, i think that the system is a galileu system. If the Earth is moving or if the Earth was not moving the result, in my opinion, were the same.
 
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Think of doing the experiment using sound. Do it on the platform. Then do it on the roof of a train. Would you be surprised if the wind had no effect on the sound? In an extreme case you could do the experiment on the back of a supersonic jet - travel faster than sound and the sound could never even reach the front mirror, let alone reflect off it.

That's why Michelson and Morley were surprised by the null result. They expected the different motion of the Earth through the ether to have an effect on their experiment. But it didn't.
 
Hello Ibix. Thanks for your answer. I understand what you have said, but are you sure that in the experiment of the supersonic jet, if the sound came of the interior of the supersonic jet, the sound never reach the front mirror? I think that the result will be that if the sound came out of the jet.
What i want to mean is that if the sound came in the interior of the jet it will be indiferent if the jet were moving (with a uniform velocity) or not.
I think that the system is a "closed" , is a galileu system...
Am i wrong?
 
Paulo Figueiredo said:
Hello Ibix. Thanks for your answer. I understand what you have said, but are you sure that in the experiment of the supersonic jet, if the sound came of the interior of the supersonic jet, the sound never reach the front mirror? I think that the result will be that if the sound came out of the jet.
What i want to mean is that if the sound came in the interior of the jet it will be indiferent if the jet were moving (with a uniform velocity) or not.
I think that the system is a "closed" , is a galileu system...
Am i wrong?

In a supersonic jet, the "medium", which is the air, travels WITH the jet. So the air inside the jet is considered to be at rest with the interior of the jet.

This is NOT the hypothesis of the classical ether, which was thought to be the medium that light travels in. It was thought that the ether pervades the universe, and that the Earth and everything else move through the ether medium. So how fast and in what direction the Earth travels through the ether should make a difference in the speed of light that is being measured even on earth.

So the two scenarios are completely different.

Zz.
 
Paulo Figueiredo said:
I understand what you have said, but are you sure that in the experiment of the supersonic jet, if the sound came of the interior of the supersonic jet, the sound never reach the front mirror? I think that the result will be that if the sound came out of the jet.
What i want to mean is that if the sound came in the interior of the jet it will be indiferent if the jet were moving (with a uniform velocity) or not.
I think that the system is a "closed" , is a galileu system...
Am i wrong?
I think you are referring to the aether drag hypothesis, the possibility that aether could be dragged along with the Earth's surface so that the speed of the aether "wind" would be zero at ground level. But if that were true, it would cause refractive effects, when viewing the stars, that have not been detected. See the blue link above for more details.
 
The Michelson Morley experiment wasn't expected to be analogous to being inside the aircraft. Ether (if it existed) clearly wasn't bothered by walls - radio waves could penetrate. And Fizeau's experiments with light in flowing water weren't consistent with ordinary matter being the medium for light. Ether had to penetrate matter.

In fact, the first thought people had to explain the null result was that ether was "entrained" by matter. That is, it was dragged along with matter somehow. So then, yes, the Michelson-Morley experiment would be analogous to working inside the jet. But that's inconsistent with astronomical observations - starlight would be aberrated by parts of the ether being dragged and other parts not being.

So, no. Ether doesn't work and Newton has to be abandoned.

Edit: Beaten to it by Zz and DrGreg, I see.
 
ZapperZ said:
In a supersonic jet, the "medium", which is the air, travels WITH the jet. So the air inside the jet is considered to be at rest with the interior of the jet.

This is NOT the hypothesis of the classical ether, which was thought to be the medium that light travels in. It was thought that the ether pervades the universe, and that the Earth and everything else move through the ether medium. So how fast and in what direction the Earth travels through the ether should make a difference in the speed of light that is being measured even on earth.

So the two scenarios are completely different.

Zz.
Thanks for your answer. I think that i understand the difference.
 
DrGreg said:
I think you are referring to the aether drag hypothesis, the possibility that aether could be dragged along with the Earth's surface so that the speed of the aether "wind" would be zero at ground level. But if that were true, it would cause refractive effects, when viewing the stars, that have not been detected. See the blue link above for more details.
Thanks. I think i had understand the difference.
 
Ibix said:
The Michelson Morley experiment wasn't expected to be analogous to being inside the aircraft. Ether (if it existed) clearly wasn't bothered by walls - radio waves could penetrate. And Fizeau's experiments with light in flowing water weren't consistent with ordinary matter being the medium for light. Ether had to penetrate matter.

In fact, the first thought people had to explain the null result was that ether was "entrained" by matter. That is, it was dragged along with matter somehow. So then, yes, the Michelson-Morley experiment would be analogous to working inside the jet. But that's inconsistent with astronomical observations - starlight would be aberrated by parts of the ether being dragged and other parts not being.

So, no. Ether doesn't work and Newton has to be abandoned.

Edit: Beaten to it by Zz and DrGreg, I see.
Thanks Ibix. I think that now i understand the difference.
 

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