Relativity without the aether: pseudoscience?

[clj4]

the issue is whether a one-way measurement of the speed of light can be carried out at all

One-way speed of light experiments have been carried out. Successfully.

http://math.ucr.edu/home/baez/physics/Relativity/SR/experiments.html#one-way tests

 

[ronterry]

"Ether and the Theory of Relativity"...Albert Einstein,an address made in 1920. See http://www.tuhh.de/rzt/rzt/it/Ether.html An interesting read.

 

[russ_watters]

Commonly cited and commonly misunderstood speech. He is pretty specific, though, in saying that his ether is not the classical ether that Michelson and Morley were looking for.

 

[ronterry]

Commonly cited and commonly misunderstood speech. He is pretty specific, though, in saying that his ether is not the classical ether that Michelson and Morley were looking for.

Probably,and probably. Einstein's ether was/is that property of space that facilitates the propagation of electromagnetic waves.

 

[ZapperZ]

Probably,and probably. Einstein's ether was/is that property of space that facilitates the propagation of electromagnetic waves.

Still, I often wonder why such a quote is being used as if it is a scientific evidence. It is not as if we are trying to do history of physics here. We would be arguing the physics of relativity and then suddenly, someone presents this speech as IF it is a valid scientific evidence.

Such a thing is irrelevant. Pay attention to the physics, not to the "embelishment". Einstein didn't live to see many advances and discoveries in physics. You do! So focus on what we know NOW, not on what he knew then.

Zz.

 

[Sojourner01]

The ether is really just a widget, isn't it? That is, it doesn't matter whether you consider it to be 'stuff' or 'nothing' as long as you ascribe to it the correct properties. Space doesn't care about how you rationalise its existence as long as your mathematics are correct. The original ether theory was disproved not because there is no ether, but because physicists made false assumptions about the nature of light due to the preconceived notion of a 'medium' being in place. There was nothing - technically - wrong with the idea of an ether itself, provided it was ascribed the correct properties. What is a quantum field, if not a massless, undetectable all-pervading 'stuff' that provides a medium in which physical processes proceed?

 

[RandallB]

What is a quantum field, if not a massless, undetectable all-pervading 'stuff' that provides a medium in which physical processes proceed?

But QM does not use a quantum field that way (an ether or Aether); the quantum field is a statistical part of the particle or photon. Not an all-pervading 'stuff' or medium.

What ether theories try to do is identify the “water” that the “waves” of the quantum field are created from or ride on.

Maybe you could refer to something like BM as having an ether in an extra set of dimensions to carry their invisible guide waves that affect microscopic particles in our real dimensions. But even that, although still non-local, would be a odd version of BM not IMO the one used by those that follow BM.

 

[ronterry]

If matter is "real",then whatever it is that gives rise to matter might also be "real", and not just an abstraction.

 

[gonegahgah]

Regarding the writer of the following quote:

Because relativity is testable, and it passes every test to which it is subjected.

As for the fact that there are other theories that are empirically equivalent to SR: this situation is not unique to SR. There are also the pilot waves of Bohmian mechanics, which is empirically equivalent to QM. Should QM be considered pseudoscience? Of course not, the question is ridiculous. And it's just as ridiculous for SR.

I don't think an aether exists either but you still have to love a person who uses two theories which themselves are theories of the same thing, yet will never be made to agree with each other (therefore one must be wrong), as examples of the correctness of current scientific process.

 

[Hurkyl]

yet will never be made to agree with each other

How can two theories that never agree with each other be empirically equivalent, which means that they agree on the result of any feasible experiment?

(p.s. I'm not entirely sure what your point is)

 

[gonegahgah]

Hurkyl,

They do not fit into each other. QM & SR can not be made to mesh and never will. They are not empirically equivalent. What is your point?

 

[selfAdjoint]

Hurkyl,

They do not fit into each other. QM & SR can not be made to mesh and never will. They are not empirically equivalent. What is your point?

Sez who? Ever looked at Dirac? Or QED? "Manifestly covariant" is how QED is commonly described. Dirac's theory is built out of representations of the Poincare group. So what is YOUR point?

 

[gonegahgah]

Dirac is famous as the creator of the complete theoretical formulation of quantum mechanics.

Q.E.D. is an abbreviation of the Latin phrase "quod erat demonstrandum" (literally, "which was to be demonstrated"). In simple terms, its use is to indicate that something has been definitively proven.

Einstein never accepted QM.
It is widely accepted that the two camps are opposed.
Have I fallen among a nest of religious fanatics here?

 

[Daverz]

Dirac is famous as the creator of the complete theoretical formulation of quantum mechanics.

Q.E.D. is an abbreviation of the Latin phrase "quod erat demonstrandum"

It's quite clear that in this context QED is Quantum Electrodynamics.

Einstein never accepted QM.
It is widely accepted that the two camps are opposed.
Have I fallen among a nest of religious fanatics here?

Einstein died more than 50 years ago, and was not even very influential at the time of his death. There are no separate relativity and QM camps. QM and relativity are both cornerstones of modern physics, and have been since the late 1920s.

 

[RandallB]

QM & SR can not be made to mesh and never will.
...
Q.E.D. is an abbreviation of the Latin phrase "quod erat demonstrandum" (literally, "which was to be demonstrated").
...
Einstein never accepted QM.
It is widely accepted that the two camps are opposed.
Have I fallen among a nest of religious fanatics here?

No I find most on here are not fanatics certainly not the Mentors, except in a good way as they do work to keep out crack pot – fanatics and in helping those that are going a bit “gahgah” as they try to get their understanding of science straight.
Some of us like to think of QED as Quantum Electrodynamics, anyway that is the way I understand it.

I think what might have you a bit gahgah; is thinking QM & SR are at odds somehow, just how would that be?
SR is just too solid and I cannot think of any theory that could fail to incorporate the principles of SR and ever expect to be correct or complete. QM certainly is capable of using SR fully.
Problem is Einstein recognized before anyone else that SR could not be complete by itself. Then came his ten year struggle that produced GR.
It is QM its implications within Standard Model that even gravity should be the result of exchanging force particles that will be forever at odds with the extra dimensional curves and warping involved in GR General Relativity.
QM has no issue with SR;
It is QM and GR that are at odds with each other.
The fact that Einstein had other issues with QM that he could not prove doesn’t matter.

SR is not restrictive but rather generic, much like Maxwell’s EM equations, as both all reasonable theories. At least I’m not aware of any theory that has shown SR or Maxwell to be in error.

 

[JesseM]

Dirac is famous as the creator of the complete theoretical formulation of quantum mechanics.

Q.E.D. is an abbreviation of the Latin phrase "quod erat demonstrandum" (literally, "which was to be demonstrated"). In simple terms, its use is to indicate that something has been definitively proven.

Since you had to quote your answers from webpages on http://www-groups.dcs.st-andrews.ac.uk/~history/Mathematicians/Dirac.html and Q.E.D (not realizing that QED is also short for quantum electrodynamics, a successful unification of quantum mechanics and special relativity), presumably the answer to selfAdjoint's question is that you are not familiar with these ideas. No shame in that, but it's better to admit to holes in your knowledge rather than just take an adversarial stance to anyone who questions it.

Einstein never accepted QM.
It is widely accepted that the two camps are opposed.
Have I fallen among a nest of religious fanatics here?

Einstein's opposition mainly had to do with conceptual issues about whether quantum mechanics provided the most complete possible description of physical systems or whether there could be additional "hidden variables" determining the outcome of seemingly random events. The only part of his opposition to QM that was directly related to relativity, as far as I know, was the issue of "spooky action at a distance" in the proposed EPR paradox, a kind of correlation between the results of measurements on widely separated particles which if you believe in hidden variables would seem to require faster-than-light signalling...but later experiments after Einstein's death have shown that these correlations do in fact occur, so local hidden variables (ie the belief in both hidden variables and the idea that they cannot affect one another faster than light) have been ruled out. And even if you want to accept a nonlocal hidden-variables theory with FTL signalling, the FTL would remain at the "hidden" level, it would not be possible for us to exploit it to send signals FTL, and so there'd be no overt experimental conflict with relativity.

 

[gonegahgah]

Hi Daverz

Thanks for that correction on QED.

I'm still sure there is a bit of hocus pocus going on. The theory that a single photon can travel all paths at once is questionable to me. From what I understand the double slit experiment is kind of proof of this (though I can explain how it isn't).

 

[CarlB]

The theory that a single photon can travel all paths at once is questionable to me.

It's objectionable to a whole bunch of other people, but the fact is that Feynman's path integrals are the best theory known.

Carl

 

[gonegahgah]

Hi Carl

Absolutely correct but only in terms of probability. Hopefully one day it will be possible for us to understand the inner working of light where we can say exactly what it will do and why rather than just what degree of things it will probably do.

 

[CarlB]

gonegahgah,

What has bothered me about path integrals is not the probabilities, but the complex numbers. I'm busily attempting to geometrize them, in the hope of understanding their inner workings. My latest attempt is based on density matrices and is here:
http://www.brannenworks.com/dmaa.pdf

Probabilities don't bother me because statistical mechanics is a classical theory.

[edit]I just realized that I've gotten way off topic here. This was originally something about aether. I hadn't been following the posts as I figured they were unlikely to go anywhere enlightening. Talking about QED probably belongs over in the quantum forum.[/edit]

 

[RandallB]

The theory that a single photon can travel all paths at once is questionable to me.
From what I understand the double slit experiment is kind of proof of this

(though I can explain how it isn't).

The double slit experiment with photon sent through one at a time provides evidence that even as it goes though one slit, it must also follow “multiple paths” enough so that it can “see” the other slit well enough to build a pattern on the other side as if it were a wave, not a particle.
Or as you put it “is kind of proof of this”

BUT you say “I can explain how it isn't”
?
DO you have a reference for why this experiment is not a satisfactory proof of this duality?
Or is it a simple straight forward explanation as to how so many scientists are misinterpreting the meaning of this experiment?
OR are you still just a little GahGah here?

 

[pess5]

It would have been very interesting to see Einstein's reaction to the Bell Inequality tests. I venture that Einstein would have assumed spacetime tunneling, or particle interaction via dimensions other than 4d spacetime. Then his locality would be unaffected, because it would apply to only our percievable 4-space, which is what it was modeled from anyways. It seems reasonable that entangled particles might interact instantly (or almost) via the curled up dimensions of string theory?

 

[JesseM]

It would have been very interesting to see Einstein's reaction to the Bell Inequality tests. I venture that Einstein would have assumed spacetime tunneling, or particle interaction via dimensions other than 4d spacetime. Then his locality would be unaffected, because it would apply to only our percievable 4-space, which is what it was modeled from anyways. It seems reasonable that entangled particles might interact instantly (or almost) via the curled up dimensions of string theory?

Einstein wasn't around to see the many-worlds interpretation of QM, it upholds both locality and determinism so maybe it would have made QM more acceptable to him. I don't think there's any basis in string theory for the idea of "shortcuts" through the extra dimensions which would allow entangled particles to communicate...doesn't the idea of higher-dimensional shortcuts require our existing 3D space to be folded in weird ways in a large extra dimension, like a sheet of paper folded over on itself in 3D space? After all, without such distortions of the lower-dimensional space, a trip through a higher dimension would normally make your trip longer, not shorter (the shortest route between two points on a plane stays within the plane, for example, it doesn't go off into the third dimension). I suppose you could imagine that particles are connected by wormholes or something similar, but this wouldn't even require any extra dimensions, and you'd have to find some non ad hoc justification for the idea that entanglement would reliably create these wormholes.

 

[pess5]

...doesn't the idea of higher-dimensional shortcuts require our existing 3D space to be folded in weird ways in a large extra dimension, like a sheet of paper folded over on itself in 3D space? After all, without such distortions of the lower-dimensional space, a trip through a higher dimension would normally make your trip longer, not shorter (the shortest route between two points on a plane stays within the plane, for example, it doesn't go off into the third dimension.

A curvature of spacetime is required to cheat time, as in the case of GR. A folding of spacetime back onto itself is required for wormhole effects. However, the hidden dimensions may be something altogether different. They may provide a path between entangled particles at the quantum level completely separate of our 4-space.

Clearly, Bell's test shows non-locality exists. Yet, relativity theory is rock solid. We don't measure light at any speed other than c, and we do not measure particles at speed c or greater, even in the supercollider. It seems rather compelling that a connection exists between entanged particles independent of 4d spacetime, and string theory does has 7 hidden spatial dimensions to allow space for string oscillations/vibrations. Maybe an interaction takes time over a hidden dimension, but is not percpetable from our 4d spacetime perspective?

 

[gonegahgah]

Hi Randall

I'm always a little gahgah here and everywhere. I was thinking that the double slit experiment related to this idea of multiple paths.

Sorry, you are accurate, I don't have any articles to draw upon that disagree with the double slit experiment, so anything I say can be ignored. I have only been able to piece together some statements from the likes of http://nanotechweb.org/articles/news/4/6/4/1#qdot and http://en.wikipedia.org/wiki/Spontaneous_parametric_down_conversion.

I am sceptical of two things: our ability to produce a single isolated photon; our ability to detect a single photon.

Here is an excerpt from something I wrote elsewhere:

<start of exerpt>

"In terms of suppressing multiple photon generation, we’ve achieved an order of magnitude below what you get from a laser," said Martin Ward, a member of the research team from Toshiba Research Europe.

This "order of magnitude" concerns me. How many orders of magnitude further do they really need to get before they actually get single photons.

In contrast, Toshiba’s quantum-dot emitter reliably generates single photons on demand when excited by short optical pulses.

The "excited by short optical pulses" concerns me. The trigger is certainly not a single pulse. What guarantee is there that the multiple photon trigger is ever going to be able to trigger the emission of one photon.

To date, single photon sources are notoriously difficult to build and rely on either heavily attenuating a laser or exciting single atoms. The drawback is that these schemes are often complex and it can be hard to prevent multiple photons being emitted.

If at all in my opinion. Probably the greatest source we have for separated photons (note I avoid the word single) is the cosmos where it takes time to build up enough photon collection to create a photographic detection. There is no way to take an instant snapshot of far distant objects in the universe. To my mind this alone is enough to question our ability to generate and detect single photons.

"There are other ways of generating single photons, like down-conversion...

Spontaneous parametric down-conversion is an important process in quantum optics. A nonlinear crystal splits incoming photons into pairs of photons of lower energy whose combined energy and momentum is equal to the energy and momentum of the original photon.

Okay the old way aparently until the quantum dots. So a 'single' photon can be split into 'two' half intensity photons can it? Are 'single' photons infinitely divisible according to current science? I guess so if they are a 'wave'.

None of the above gives me confidence about our ability to separate light into single photons nor that a detector could be made to detect single photons which to my mind are individually just too small.

<end of exerpt>

I have also noticed that with the 'single photon' results that the pattern that is produced is a lot less perfect than the pattern produced by a continuous light source. The 'single photons' appear even where they wouldn't in the continuous light source results even sometimes at the mid way points and the coverage is greater overall than for the continuous source. This seems to describe less than perfect wave interference.

I'm in agreeance that we can obviously reduce the number of photons that are present by an order of magnitude but I'm doubtful that we are achieving single photons and I'm doubtful we can even detect a single photon. Even if we had a single photon it could do a lot of things other than what we want it to do. It could miss both slits entirelly, it could reflect, deflect, miss, it could react in a completely useless and undetectable way.

I'm more of the opinion that the so called detected 'single photons' are the gradual build up of a detectable 'dot' on the photographic material. By reducing the number of photons you can reduce the amount of scattered build up so that dots appear occasionally (and sometimes two or more at once). With enough random co-incident strikes over time in a similar region a detectable dot will eventuate.

I just think that a photon is too small and fast for us to harness. So instead I'm suggesting that multiple but fewer photons pass through the slits and interfere with each other and gradually build up to produce dots on the photographic material - just like space telescopes gradually build up a picture of distant galaxies.

In the same way that we can't take instant photos of very distant galaxies I also don't think that we can take instant photos of single photons.

I am purely extrapolating from what I have read and from my concept of how tiny and fast a photon really is in the scheme of things. In this respect you certainly don't have to give any credence to my scepticism of the double slit experiment. However if you think I make interesting points then give me that at least even if you don't agree.

 

[RandallB]

I am sceptical of two things:
our ability to produce a single isolated photon;
our ability to detect a single photon.

Don't be

A lab problem -- that I think they have more than demonstrated the ability to DIM the energy in a light beam evenly to the point where the Q Packets of energy must be separated by a measurably significant amount of time and distance in order to account for the fixed amount of energy in each photon “Q Packet”.

Same deal with measuring.
Plus the fact they have been able to duplicate the same results with a discrete “real particle” an electron, to get the same kind of results for both Bell & Two Slit tests. I think this is more than enough to show the labs know what they are doing on this point, and that they are measuring individual photons ok.

 

[CarlB]

I think this is more than enough to show the labs know what they are doing on this point, and that they are measuring individual photons ok.

Yes. And physics is very tightly woven together. If one denies this effect, the consequences are that huge other parts of physics have to be changed as well.

 

[gonegahgah]

Hi Carl

Yes I agree. But that is not for discussion here.

Hi Randall

It certainly would be a challenging work. Good luck to them if that is what they have achieved. Be interesting to see where it all ends up.

 

[JesseM]

A folding of spacetime back onto itself is required for wormhole effects.

It's often represented that way in embedding diagrams like http://en.wikipedia.org/wiki/Image:Worm3.jpg of mine from a little while back for some references. Conceptually, I think the idea is that if I make a measurement on one member of an entangled pair over here, and you make a measurement on the other member over there, each of us splits into multiple versions who observe different outcomes, and the universe doesn't have to decide which versions of me are part of the same "world" as which versions of you until there has been time for a signal moving at the speed of light or slower to pass between us. Here's a little toy example I came up with a while ago to illustrate this idea:

say Bob and Alice are each receiving one of an entangled pair of photons, and their decisions about which spin axis to measure are totally deterministic, so the only "splitting" necessary is in the different possible results of their measurements. Label the three spin axes a, b, and c. If they always find opposite spins when they both measure their photons along the same axis, a local hidden-variables theory would say that if they choose different axes, the probability they get opposite spins must be at least 1/3 (a hidden variables theory would say that if the three axes of one photon were in preexisting hidden spin states a+, b+, c+, the three axes of the other photon must be in states a-, b-, c-, giving a 100% chance the experimenters find opposite spins when they measure different axes; on the other hand, if one photon is in a heterogeneous state like a+, b-, c-, the other photon must be in the opposite state a-, b+, c+, and if you randomly pick two different axes from the two photons in this case, there is a 1/3 probability you'll get opposite spins and a 2/3 probability you'll get identical spins). The actual Bell-inequality-violating probability predicted by QM will depend on the details of what the three axes are, but all that's important is that it's less than 1/3, so for the sake of the argument let's say it's 1/4.

So suppose Bob's decision will be to measure along axis a, and Alice's decision will be to measure along axis c. When they do this, suppose each splits into 8 parallel versions, 4 measuring spin + and 4 measuring spin -. Label the 8 Bobs like this:

Bob 1: a+
Bob 2: a+
Bob 3: a+
Bob 4: a+
Bob 5: a-
Bob 6: a-
Bob 7: a-
Bob 8: a-

Similarly, label the 6 Alices like this:

Alice 1: c+
Alice 2: c+
Alice 3: c+
Alice 4: c+
Alice 5: c-
Alice 6: c-
Alice 7: c-
Alice 8: c-

Note that the decision of how they split is based only on the assumption that each has a 50% chance of getting + and a 50% chance of getting - on whatever axis they choose, no knowledge about what the other one was doing was needed. And again, only when a signal traveling at the speed of light or slower passes from one to the other does the universe need to decide which Alice shares the same world with which Bob...when that happens, they can be matched up like this:

Alice 1 (c+) <--> Bob 1 (a+)
Alice 2 (c+) <--> Bob 2 (a+)
Alice 3 (c+) <--> Bob 3 (a+)
Alice 4 (c+) <--> Bob 5 (a-)
Alice 5 (c-) <--> Bob 4 (a+)
Alice 6 (c-) <--> Bob 6 (a-)
Alice 7 (c-) <--> Bob 7 (a-)
Alice 8 (c-) <--> Bob 8 (a-)

This insures that each one has a 3/4 chance of finding out the other got the same spin, and a 1/4 chance that the other got the opposite spin. If Bob and Alice were two A.I.'s running on classical computers in realtime, you could simulate Bob on one computer and Alice on another, make copies of each according to purely local rules whenever each measured a quantum particle, and then use this type of matching rule to decide which of the signals from the various copies of Alice will be passed on to which copy of Bob, and you wouldn't have to make that decision until the information from the computer simulating Alice was actually transmitted to the computer simulating Bob. So using purely local rules you could insure that, after many trials like this, a randomly-selected copy of A.I. Bob or A.I. Alice would record the same type of statistics that's seen in the Aspect experiment, including the violation of Bell's inequality.

Note that you wouldn't have to simulate any hidden variables in this case--you only have to decide what the spin was along the axes each one measured, you never have to decide what the spin along the other 2 unmeasured axes of each photon was.

It seems rather compelling that a connection exists between entanged particles independent of 4d spacetime, and string theory does has 7 hidden spatial dimensions to allow space for string oscillations/vibrations.

Yes, but these are assumed to be small curled-up dimensions, and it seems to me that if you're thinking in terms of embedding 3D space in a higher dimension, you need large dimensions to curve the space around and create a link between distant points on the surface as in the embedding diagram I linked to earlier. There are "braneworld" scenarios that suggest a single large dimension, but there are ways space can be connected by wormholes that probably couldn't be explained in terms of embedding it in a single higher dimension, like if you had a large collection of wormholes that each had one of their mouths in a common area next to the mouths of all the other wormholes, but the other mouths of each wormhole opened up in all sorts of different locations far from one another. In general, it was mentioned on this thread that you need a gigantic 90-dimensional embedding spacetime consisting of 87 spacelike dimensions and 3 timelike dimensions in order to embed an arbitrarily curved 4D spacetime of the kind allowed by GR into a flat embedding spacetime without curvature of its own.

 

[pess5]

The Many Worlds Interpretation assumes multiple time-lines, does it not? That there are an infinite number of choices you might make in some instant, and you make all them, but each of your subsequent selves have no knowledge of the other timelines which resulted. Is this true?

pess