1) In later years Einstein admitted that aether was not superfluous as he originally contended and also admitted that Mach’s ideas had an undue influence on his thinking.
2) Special Relativity is constrained to two frames in the Principle of Relativity, yet all tests of this principle involve a third frame used to calibrate what happens in the other two frames. When you introduce a calibration frame (three clocks, one traveling east, one traveling west, and a calibration clock at some fixed position which fixed position is equivalent to finding an absolute frame) then the theory becomes absurd.
3) In explaining the null results of the Michelson-Morley experiment, two analogies were used by Einstein. One is the swimmer analogy and the other is the airplane analogy. When analyzed these seem logical, but a flaw was found in his logic.
For simplicity an analogy of the experiment, called the swimmer analogy, is given to explain the key elements. The critical points are now represented as the corners of a square and the paths are given as channels rigidly fixed to the banks of a river. The channels are fixed by straight boards and two swimmers represent the beams of light that are split by the interferometer with one swimmer swimming parallel to the river (ether stream) and the other swimming perpendicular to the river. The ether which was at rest is now a moving river. This would be a preferred frame of reference. The earth and the interferometer are now at rest with respect to the river and are represented by the river banks and our straight boards. All points of motion are now inverted, and the preferred frame is now in relative motion.
In accordance with this analogy and the results of the actual M-M experiment, the results are negative, a negligible amount of interference occurred, and no variation is found in the speed of the swimmers or the speed of light in moving from one point to another and back again. We could conclude from this that the speed of light is constant and the ether doesn’t affect it’s speed or just doesn’t exist!
However, the swimmer analogy contains a fatal flaw or two.
When inverting stationary positions for moving positions and vice versa, the movement of the light beams themselves are not inverted. In other words, the swimmers would not be swimming!
A correct analogy would show the wooden frame traveling across a still lake and the swimmers would be swimming, one parallel to the motion of the wooden frame, and one normal to its motion. If we were to now measure the distance each swimmer traverses with respect to the water in the lake, the path lengths of the triangle from position (A) to position (B’) and back to position (D) would not equal the path length of the swimmer going from position (A) to position (C’) and back to (A’). If two swimmers traverse unequal path lengths in equal times, then the velocities of the two swimmers are not equal.
/sin(A-B) A-B) is the path length for swimmer 1.
S2 = (A-C’) + (C’-A’) is the path length for swimmer2.
S2 > S1 S1v S2v
If there is one universal coordinate system, the ether of space, we could visualize these models, but we could not affix a measuring device to the ether itself. We would have to assume that the velocity of light is changing when it is emitted from an object moving through a motionless ether. But, are we to assume the ether is motionless? Is there any other experiment we could perform to determine if the velocity of light is invariant in all reference frames, or whether it varies by composition with kinematic sources?
Professor Laro Schatzer has made this cogent statement regarding an ether frame: There have been a variety of theories to describe electromagnetic waves (light) as excitations of some medium, quite in analogy to sonic waves which propagate in the medium air. This hypothetical medium was called the ether and it was supposed to be in rest in the absolute space-time frame. That is why this frame is also called ether frame sometimes. Since the establishment of the theory of special relativity it has become extremely unpopular among scientists to speak about an “ether”. However, we know today that electromagnetic waves are indeed excitations of some “medium”. However, this medium is not a solid or a liquid in the classical sense, but it is governed by the laws of quantum mechanics. Quantum field theorists found the name vacuum for it. Some people interpret the vacuum as space-time itself, but this does not cover the fact that its true nature still remains a mystery. Anyhow, the term quantum ether might be used to indicate a possible modern synthesis of both concepts.
A. Brillet and J.L. Hall conducted a modern ether drift experiment in 1979. Brillet and Hall put a laser on a rotating platform and split the beam. One part of the beam went into a Fabry-Perot interferometer, the other was directed via mirrors off the platform to be compared with a reference beam from a stationary laser. The frequency of the rotating laser was compared with that of the reference laser; the difference was Fourier analyzed.
Any anisotropy of the speed of light would show up as a frequency shift which varied dependent on the direction of the interferometer. If the old pre-Lorentz ether theory were true (static ether), they would have found a frequency shift dependent on sidereal direction of the interferometer and found no such effect.
They also found a frequency shift of 17 Hz at twice the table rotation rate, which they could not explain on direction of interferometer with respect to the lab. It is this effect which is predicted by an entrained ether theory.
An entrained ether theory favors a dynamic ether, an ether that can be entrained in motion by a rotating object, such as earth, embedded within the dynamic ether.
Einstein did not examine this logic, but he did realize that space curvature could not apply to a space without physical properties. It is those properties that are still unknown as we discover more about its nature.
There are those who take issue with some of the math as well, however most of the math in Relativity was worked out by Poincare and Lorentz prior to Einstein and Lorentz based this math on the existence of an ether!