Understanding the Speed of Light in Ether: A Historical Perspective

In summary, according to the classical ether theory, the speed of light was always the same in the rest frame of the ether, but this was inconsistent with the negative result of Michelson-Morley experiments. Maxwell proposed that the speed of light was the same in every frame of reference, even in the absence of matter, which is what we understand today.
  • #1
Luis Babboni
10
1
Hi people!

May be this could be an historical question.
Before Einstein, it is suppoused that speed of light in ether is always the same, I´m right?
I mean, if observer O is at rest respect ether and observer O´ is moving respect ether and O´ send a photon to O, the speed at which that photon arrives O (measured by O) is c cause, as I said, O is at rest respect ether? That is that the speed of O´, the source of the photon, must not be added to c.

Thanks for comment.
 
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  • #2
If you're going to talk about what physicist believed before 1905 you will have to pretend that you never heard the word 'photon"... but you can substitute the more appropriate phrases "flash of light" or "light signal" and your question still works.

And with that correction the answer is "yes". However, this answer is inconsistent with the negative result of Michelson-Morley experiments, and that's how we ended up where we are.
 
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  • #3
Thanks Nugatory! :-)
 
  • #4
Luis Babboni said:
Before Einstein, it is suppoused that speed of light in ether is always the same, I´m right?

According to the classical ether theory the speed of light was always the same in the rest frame of the ether (in absence of matter).
According to Maxwell the speed of light was the same in every frame of reference (again in absence of matter).
 
  • #5
"According to Maxwell the speed of light was the same in every frame of reference (again in absence of matter)."
Good point!
Thanks DrStupid!
 
  • #6
Mentor's note: Several off-topic posts about the Lorentz ether theory have been removed from this thread. Despite sharing the word "ether", this is a substantially different theory (not falsified by Michelson-Morley experiments) than historical ether theory that the original poster was asking about.

Even if it were on topic in this thread, we generally do not allow discussion of the LET: https://www.physicsforums.com/insights/pfs-policy-on-lorentz-ether-theory-and-block-universe/
 
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  • #7
DrStupid said:
According to Maxwell the speed of light was the same in every frame of reference (again in absence of matter).
Does that mean everything is at rest with respect to a flash of light or light signal?
 
  • #8
David Lewis said:
Does that mean everything is at rest with respect to a flash of light or light signal?
No. It turns out to mean (coupled with the principle of relativity) that there is no such thing as "with respect to light". You can't define a frame where light is at rest.
 
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  • #9
Nugatory said:
Mentor's note: Several off-topic posts about the Lorentz ether theory have been removed from this thread. Despite sharing the word "ether", this is a substantially different theory (not falsified by Michelson-Morley experiments) than historical ether theory that the original poster was asking about.

Even if it were on topic in this thread, we generally do not allow discussion of the LET: https://www.physicsforums.com/insights/pfs-policy-on-lorentz-ether-theory-and-block-universe/

The reason I asked about it is cause in our class we have a first practice that ask we what previous to Einstein physics thought about some things and then in following practices we must found what after Einstein physics thinks about the same things.
 
  • #10
Luis Babboni said:
The reason I asked about it is cause in our class we have a first practice that ask we what previous to Einstein physics thought about some things and then in following practices we must found what after Einstein physics thinks about the same things.
There is some discussion on the history leading up to Special Relativity in this chapter of this book.
 
  • #11
Thanks!
 

1. What is the concept of ether in relation to the speed of light?

The concept of ether was a popular idea in the 19th century, which proposed that there was a medium called ether that permeated through all space and provided a medium for light to travel through. It was believed that the speed of light was constant in this medium and acted as a reference frame for measuring the speed of objects.

2. How did scientists in the past understand the speed of light in ether?

Scientists in the past used various experiments, such as the Michelson-Morley experiment, to try and measure the speed of light in ether. However, these experiments yielded inconclusive results, leading to the eventual rejection of the concept of ether.

3. What was the significance of the speed of light in ether?

The speed of light in ether was significant because it was believed to be a constant and acted as a reference frame for measuring the speed of objects. It also played a role in the development of the theory of relativity, which ultimately replaced the concept of ether.

4. Why was the concept of ether eventually rejected?

The concept of ether was eventually rejected due to the lack of evidence supporting its existence. The Michelson-Morley experiment and other experiments showed that the speed of light was constant regardless of the reference frame, leading to the development of the theory of relativity.

5. How does the understanding of the speed of light in ether impact our current understanding of light and physics?

The understanding of the speed of light in ether has greatly impacted our current understanding of light and physics. It led to the development of the theory of relativity, which revolutionized our understanding of space and time. It also showed that the speed of light is a constant, regardless of the reference frame, and has played a crucial role in many modern technologies such as GPS and telecommunications.

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