# B Why Special Relativity have overcome Ether Theory?

1. Jan 21, 2017

### Bartolomeo

My question is very simple.

As far as I know, once upon a time there was the Lorentz Ether Theory. This theory admitted existence of so-called Ether as a certain preferred frame, which was undetectable because of physical contraction of moving material bodies in direction of their motion.

In very simple words – this theory explained null result of Michelson – Morley experiment (and null result of all other Ether drift experiments) by physical contraction of length of interferometer in direction of its motion.

Albert Einstein admitted: “Concerning the experiment of Michelson and Morley, H. A. Lorentz showed that the result obtained at least does not contradict the theory of an ether at rest.”

http://www.relativitybook.com/resources/Einstein_space.html

In Lorentz theory due to interaction with Ether moving measuring rod with proper length L0 was gamma times shorter, than a measuring rod with the same proper length which is “at rest” in the Ether. Thus, a rod “at rest” was gamma times longer than moving rod.

Though this theory could also explain null – results of Ether Drift experiments, Ether theory was finally rejected and SR was accepted.

In Lorentz theory velocity of light in the Ether was c, hence velocity of light in different directions was different for moving and observer and one at rest. Hence, frame of reference “at rest” had a specific feature – velocity of light in all direction in this frame was c (hmm… just like in the rest frame in SR).

Article in Wikipedia claims: A defining feature of special relativity is the replacement of the Galilean transformations of Newtonian mechanics with the Lorentz transformations.

But, to my knowledge, Lorentz theory employed the same transformations.

As I understood, relativity of simultaneity is inseparable feature of the SR which is a consequence of equivalence of inertial reference frames. Exactly relativity of simultaneity causes reciprocity of observations, like length contraction by every observer.

In Lorentz theory, relatively moving frames are not equivalent.

Thus, it is exactly Special Relativity predicts some astonishing effect like hotly - debated on pages of this wonderful forum “Embankment and Train paradox” a.k.a. “barn and ladder paradox” a.k.a. “train and tunnel paradox”. This effect cannot take place in Lorentz Theory due to lack of symmetry. This is significant difference in description of properties of space – time.

Also in Special Relativity Maxwell equations take invariant and independent of chosen reference frame form.

This is what makes Special Relativity preferable, am I right?

2. Jan 21, 2017

### PeroK

That and 100 years of experimental evidence.

3. Jan 21, 2017

### Staff: Mentor

There is also the assumption of the existence of a medium for which there is no evidence.

4. Jan 21, 2017

### Ibix

As I understand it, Lorentz ether theory is simply SR with an undetectable preferred frame. Which frame is the preferred one? There's no way to tell. So most people shrug their shoulders and remain agnostic - which is the Einstein/Minkowski picture.

You could write a simulation program that records x(t), y(t) and z(t) for all particles in some frame whose time coordinate is t. Here you would be simulating a Lorentz ether. Alternatively you could set up and solve the geodesic equations in flat space. Here you would be simulating a 4d universe. Simulated entities in the simulated universe wouldn't be able to tell the difference unless there was some kind of Lorentz-invariance violating rounding error or something that might give them a clue.

5. Jan 21, 2017

### Staff: Mentor

In all measurable aspects relatively moving frames are equivalent. It is a derived result in LET rather than a postulate, but the equivalence is present in all LET experimental results also.

6. Jan 21, 2017

### Bartolomeo

Not too much to make a conscious choice. Yet it is not clear in which direction.

It is not possible to distinguish between LET and SR by experiment

Einstein synchronization is a convention too.

I wonder what would have happened if everyone had his own Greenwich Meridian? Relativity of simultaneity!

It means that in LET train and embankment paradox is simply a consequence of “improper” clock synchronization by moving observer. He can't detect his own motion and synchronizes clock by Einstein signalling method, which leads to artificial reciprocity of observations.

@Ibix, I still think that reciprocity is artificial.

So it seems that theories are fully compatible and empirically equivalent and it is just a matter of taste what philosophical views stick.

But, these effects – Jim is shorter than Tony, Tony is shorter than Jim, Jim is slower than Tony and Tony is slower than Jim regarded as an objective reality. These effects sometimes cause such fierce resistance that the opposition researchers even deny the very existence of relativistic effects.

In the one hand they are empirically equivalent, but on the other hand they have certain differences.

There is no doubt that slow aging of a non - inertial twin is a physical fact. How these theories explain it?

In LET it is rather effect, than paradox. If twin A is at rest, twin B flies away and return, he will obviously be younger. If twin A and twin B fly alongside, A stops for a while and catches up his brother B, A will be younger again. It is elementary school mathematics.

7. Jan 21, 2017

### Jeronimus

The simulated entities however could themselves think of writing such a simulation and take the perspective of someone who is outside the 4d universe, looking at how the entities move through a static 4d universe, like a DVD laser read head moving through a DVD.

The writer of the simulation, observing those entities moving through the 4d universe would be faced with a problem. Would he allow those entities to move freely through the 4d universe in the sense that when two of their worldlines cross, the entities(laser read heads) would not necessarily meet, or would he create a universe where the entities(laser read heads) DO meet when worldlines cross.

In the prior case, you would end up with something that is closely resembling solipsism, philosophically speaking.

When physicists speak of the possibility that our universe could be a static 4d spacetime hypercube (or a construct with more dimensions), they neglect part of this analogy, which in my opinion is simply wrong.

What we experience as now, the present, is not included in this analogy.
It is a static 4d spacetime hypercube + the laser read head either moving through the hypercube, or the hypercube moving relative to the fixed laser. And this laser read head amounts to just ONE entity.
What about the other entities, supposed we assume that we are not the only ones, while the rest is just a figment of our imagination? Hence, more laser read heads. For each entity one, sub the pZombies(philosophical zombies which just act as if they are conscious).

The writer of the simulation, looking at the simulation from outside would face a serious problem when trying to achieve the goal of having those laser read head/entities meet when the worldlines cross, if he was to base his simulation on relativity.
He would at any point in time(metatime outside the simulation) be able to pinpoint each entity to a given location x,y,z,t within his simulation, and maintain the above rules of entities meeting when worldlines cross, which as far as my limited knowledge allows me to see, is impossible without running into irrationality issues.

Last edited: Jan 21, 2017
8. Jan 21, 2017

### Staff: Mentor

You can call it "artificial" if you wish, but the fact is that both LET and SR predict reciprocity in all measurable results.

Correct.

Therefore the entire discussion is purely philosophy and semantics. Thread closed.