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Extrasolar
2012-Mar-07, 04:51 PM
This is a question from ignorance on science history, but what was the motivation for including an aether into classical mechanics? Was it's inclusion the result of observation or philosophy? Ultimately, I am wondering if the exclusion of an aether might have resulted in an accelerated progression of special relativity.

Edit: Or rather theories on light and time in general.

quantropy
2012-Mar-07, 05:18 PM
Thomas Young's argument that light is a wave was accepted in the early 1800's and after that it was thought that if there was a wave there ought to be something that was waving - the aether. There then arose quite a few ideas about it, for instance the existence of 'aether atoms' and the possibility that nebulae seen in the night sky were condensations of aether.

Even if people hadn't felt that an aether was required, I doubt whether special relativity would have been thought up any earlier. It may well have been the other way round - without the surprise of the Michelson-Morley experiment, there might have been less motivation to believe in the counterintuitive ideas of special relativity.

trinitree88
2012-Mar-07, 09:49 PM
This is a question from ignorance on science history, but what was the motivation for including an aether into classical mechanics? Was it's inclusion the result of observation or philosophy? Ultimately, I am wondering if the exclusion of an aether might have resulted in an accelerated progression of special relativity.

Edit: Or rather theories on light and time in general.

Extrasolar. To be accurate, the Michelson-Morley experiment never proved that the ether did not exist...only that it could not be detected using his interferometer in a two-way light path. The assumption that the ether does not exist is pretty mainstream, but remains unproven. Neither has anyone proven that it does exist, only that it's nonexistence simplifies some assumptions. This is not a spiel of my own, rather the viewpoint of Isaac Asimov in his text "On Physics". There are four independent physically valid conclusions from the experiment. pete

Extrasolar
2012-Mar-07, 10:14 PM
Extrasolar. To be accurate, the Michelson-Morley experiment never proved that the ether did not exist...only that it could not be detected using his interferometer in a two-way light path. The assumption that the ether does not exist is pretty mainstream, but remains unproven. Neither has anyone proven that it does exist, only that it's nonexistence simplifies some assumptions. This is not a spiel of my own, rather the viewpoint of Isaac Asimov in his text "On Physics". There are four independent physically valid conclusions from the experiment. pete

Right, but no one has proven Unicorns exist or don't exist as well. Why would one even look for one in the first place? If an idea has no physical basis in reality, then an experiment to prove or disprove its existence will inevitably end in the same result, its non-existence. Why was such an idea given so much credit to begin with is what I wonder. It seems more philosophical than theoretical. It's fascinating that the idea was so accepted up until the early 20th century. Just trying to understand why exactly.

Jens
2012-Mar-08, 02:18 AM
It's fascinating that the idea was so accepted up until the early 20th century. Just trying to understand why exactly.

You mean that the aether exists? It seems perfectly logical to me to accept it. After all, we know that light acts like a way, and generally speaking, waves require a medium to travel in. Consequently, light should have a medium to travel in, and the aether is what it would be called.

billslugg
2012-Mar-08, 02:23 AM
Each particle with mass has a gravitational field that reaches throughout the entire universe. Similarly, each charged particle has an electric field and magnetic field that extends similarly. When charged particles are accelerated, such as when producing an electromagnetic wave, it is those already existing fields that carry the wave. The already existing fields, in a sense, are the aether. Right?

Shaula
2012-Mar-08, 06:18 AM
The already existing fields, in a sense, are the aether. Right?
No. Classically the aether was the medium which propagated those waves. In your case if there was no charge anywhere to start with then if you magically produced a charged particle it could have no field, since there was no background field before and therefore nothing for this new field to propagate through.

billslugg
2012-Mar-08, 02:32 PM
I understand that this explanation is different from the classical, but is it not the pre existing fields of particles that carry the wave? Also, charge is conserved thus cannot be created or destroyed, correct?

Shaula
2012-Mar-08, 05:47 PM
I understand that this explanation is different from the classical, but is it not the pre existing fields of particles that carry the wave?
Photons and so on are quantisations of a quantum field - this is not an aether, it is a quantum field. Why reuse old terminology to refer to something that already has a name and behaves totally differently to the old thing?


Also, charge is conserved thus cannot be created or destroyed, correct?
Charges can be created or destroyed provided the sum of charges before and after remains the same. So you cannot change the overall charge of a system but you can create charges within it quite easily.

jfribrg
2012-Mar-08, 07:25 PM
Even if people hadn't felt that an aether was required, I doubt whether special relativity would have been thought up any earlier. It may well have been the other way round - without the surprise of the Michelson-Morley experiment, there might have been less motivation to believe in the counterintuitive ideas of special relativity.

I don't think that would have changed much because once SR was published it wouldn't be long before someone would test it using an experiment similar to MM. Also, the MM experiment might not have had too much influence on Einstein's development of SR. There is some debate on whether Einstein even knew about the MM experiment in 1905. He probably did, but it probably wasn't a motivating factor for his developement of the theory.

DoggerDan
2012-Mar-10, 08:41 AM
This is a question from ignorance on science history, but what was the motivation for including an aether into classical mechanics?

There was a rather in-depth article about it in this month's Discover. Most of it was beyond my understanding, but they had some very good explanations for the layman.