What is Ether theory? (I think the book I had read is giving wrong explanation of Ether) I was reading about Ether, Maxwell and Young-double-slit experiment. I got a question about Ether law. Let me say what I read about Ether Law.

Suppose, a boat is traveling with Adverse of Water flow. Suppose, that boat is traveling $1 \ km/m$. So if the boat travels with favorable than if I push the boat with same "speed" than it will travel more faster than earlier cause the water flow is pushing it also. 
They didn't finish the text here. So I am not going to say that it is Ether law.

They also said; If we think a train and that is traveling $200 \ km/h$ through west and another train is traveling through east with $100 \ km/h$. Then observer from second train will see that the first train is traveling backward with $100 \ km/h$ but if an observer (who isn't traveling) will see that the first train is traveling with $200 \ km/h$ through west. That's what I had read in Relativity but I had read it in Ether theorem also. That's why I was confused too much.
If we think of two bus. And both bus are traveling. Suppose, first is coming from west and another bus is coming from east. So, at initial point the if someone shout from first bus then they will hear that sound "lately". The closer the bus gets the faster the sound will be. So it's like "speed" of sound is increasing.I am saying that it doesn't make sense to me. Cause we had came closer to that sound the sound's velocity didn't increase or decrease at any time.
The author wrote that just like speed of sound is increasing so speed of light should increase also (They wrote it after the next line). They said,"earth is revolving the sun. It isn't moving circularly but just like oval. So if we think that the earth is too far away from sun at point A and it's closer to sun at point B". So the light from sun should reach to the earth more faster at point B rather than point A. Which proves that the speed of light is increasing. I said earlier that it doesn't make sense to me.

I had asked one of my teacher today that, "What's the difference between Relativity and Ether?" He replied,"Ether is a part of Relativity". I had read in that Maxwell said Ether isn't true. Light travels at constant speed. I believe Maxwell's theory is true. But I am not saying that Ether is false. I am saying that the explanation of Ether is false. If Ether is false than Relativity is also. But I believe in Relativity.

At Maxwell's time average physicists had believed that Ether is true but Maxwell said it isn't. After Maxwell died, Michelson (Did I spell it wrong?) had proved that Ether is false but he didn't say what's happening with light (wave) (by his experiment).

Did Maxwell really said that Ether is false?
I was reading the Wiki (Aether) after writing the whole text. What I understood from the Wiki that is Ether actually says light (everything) needs medium to travel (or Ether provides such a medium). But Michelson had proved that light can travel in vacuum. What actually Ether is? It's like Ether doesn't have anything to do with Relativity. I had found another Wiki (Luminiferous aether).

it (Ether) required the existence of an invisible and infinite material with no interaction with physical objects.


After reading these Wiki, I think Ether is something like "medium" or "space" which have no interactions between any physical materials. I can't understand the Ether further.
 A: Ether is not "part" of relativity (relativity works without it), though introductory courses in relativity usually make mention of it, especially in the context of the Michelson-Morley experiment, which showed there is no such thing.
Maxwell never abandoned the idea of the possibility of an ether. In the link you provided:
"Maxwell noted in the late 1870s that detecting motion relative to this aether should be easy enough—light travelling along with the motion of the Earth would have a different speed than light travelling backward, as they would both be moving against the unmoving aether."
But he also knew that light could propagate through vacuum. And his theory of electromagnetism has never   needed an ether, and works perfectly without it.
The ether was not believed to be a physical medium, but something that was present everywhere in the universe, that interacted with nothing, that allowed for the propagation of electromagnetic waves. That is, since every other wave in nature needed a medium, and light also being a wave, the incorrect conclusion was made that light needed a medium - the ether.
But it's important to note that the Michelson-Morley, and subsequent experiments, ruled out the existence of such a medium.
Also note that the Einstein Aether theory is unfortunately named, since there is an implication that Einstein himself supported the idea of motion relative to this aether. Einstein rejected this idea, and although there are some models of relativity and gravitation that incorporate an aether, none of these theories can be Lorentz invariant and are hence not considered to be valid theories in the context of mainstream physics.
