Aether

[jajrussel]

Aether, I know it doesn’t exist. My question is about why we know it doesn’t exist. The Michelson-Morley experiment. Which actually as I read about it doesn’t really make sense to me because if c is c invariant what exactly were they looking for? But, Einstein’s c invariant was after M&M, okay that lines up. Hmm, but what other proofs were being looked for? 
 

why was Aether assumed stationary?

 If they expected it to be stationary, why were they assuming a variation of c would be found? I would assume that a stationary system would have to be non-reactive.

the reason I ask is because I was watching a video about dark matter, and dark energy and the reasons they are believed to exist and the reasons why they are called dark. So, we can see the reasons we think they do exist. Then I’m wondering, why did they think Aether existed, originally?  What were they looking for to prove Aether existed?

What would be the difference between an Aether that doesn’t  react with light and matter, accept gravitationally, and dark matter?

 Was the M&M experiment based solely on an expected variable c?

Thank you. 

[jajrussel]

Apparently I’ve misunderstood what they meant by stationary, but still as I read about it, it is still confusing. It says ( the ether has to be remaining stationary with respect to the star as the earth moved through it. ) looking at their picture I can only assume this means what? I don’t know, because all my guesses say why would they think they could recreate a situation that seems implied by that statement?

Edited February 7, 2021 by jajrussel

[swansont]

2 hours ago, jajrussel said:

why was Aether assumed stationary?

Stellar aberration’s basic explanation was known since ~1725, which precludes us being at rest with respect to the aether. We had to be moving, but the M-M experiment showed that to be wrong.

https://en.wikipedia.org/wiki/Aberration_(astronomy)

[Janus]

4 hours ago, jajrussel said:

Aether, I know it doesn’t exist. My question is about why we know it doesn’t exist. The Michelson-Morley experiment. Which actually as I read about it doesn’t really make sense to me because if c is c invariant what exactly were they looking for? But, Einstein’s c invariant was after M&M, okay that lines up. Hmm, but what other proofs were being looked for? 
 

why was Aether assumed stationary?

 If they expected it to be stationary, why were they assuming a variation of c would be found? I would assume that a stationary system would have to be non-reactive.

the reason I ask is because I was watching a video about dark matter, and dark energy and the reasons they are believed to exist and the reasons why they are called dark. So, we can see the reasons we think they do exist. Then I’m wondering, why did they think Aether existed, originally?  What were they looking for to prove Aether existed?

What would be the difference between an Aether that doesn’t  react with light and matter, accept gravitationally, and dark matter?

 Was the M&M experiment based solely on an expected variable c?

Thank you. 

The M&M experiment assumed that light's speed was fixed at c relative to the aether.   It was an attempt to measure the Earth's motion with respect to the aether. (the aether would be the standard by which "stationary" would be defined.

Now it was possible that, due to other various motions, the Earth, at a given moment, could be stationary with respect to the aether.  However, that could only happen at one particular point of Earth's orbit.  Do the experiment again 6 mo. later, and the Earth's motion with respect to the aether would have to be in the order of 60 km/sec.

If there was an aether that light traveled at c with respect to, the experiment should have have been able to measure some motion of the Earth with respect to it simply by doing the experiment at different times of the year.

[MigL]

All previously encountered wave motion was dependent on a medium, so the assumption was, light being a wave, it needed a medium.
This 'medium', the aether, would have had to have very inconsistent properties; such as extreme 'stiffness' to account for the fast speed of light, yet offering no resistance to objects moving through it ( MM proved it doesn't impede the Earth's motion at all ).
Einsteinian relativity did not need a 'medium' for light, his theory is self-consistent and holds up to experiment extremely well.
So the aether was discarded as unnecessary.

It wasn't so much disproven, but if it did exist, it would have such incredible properties as to be undetectable.

[Markus Hanke]

14 hours ago, jajrussel said:

My question is about why we know it doesn’t exist. The Michelson-Morley experiment.

The MM experiment is only an isolated example of a very long history of extensive searches for an “aether”, and it has long since been superseded by far more sensitive experiments. No trace of any kind of aether has ever been found, even after 300+ years and many hundreds of experiment ranging from mechanical table-top setups right up to ultra-sensitive and complicated optical measurements of various kinds.

On the other hand, local Lorentz invariance (the symmetry underlying Special Relativity) has been experimentally established to such a high degree that its validity is no longer in any kind of reasonable doubt.

If you combine these, then the absence of any evidence for aether, as well as the simultaneous experimental verification of Lorentz invariance, make it - for all intents and purposes - a near certainty that there is no such thing as an aether. And why should there be? It isn’t needed in any way, shape or form to explain anything.