Validity of Relativity

Farsight

Thanks for the link, setAI, I've printed out David Deutsche's paper and will study it carefully.

hurkyl, what you're saying sounds good to me. I think.

I'll get back here when I've read that paper tonight.

ttn

Huh? This makes it sound like you are quite clueless about Newtonian physics (which I doubt is the case). Do you really think Newton's first law says "all moving things will keep on moving no matter what"?

Anyway, there is a very clear sense in which MWI insists that we are deluded about basic apparent perceptual facts. This is in contrast to every other scientific theory that is or has been widely accepted. If this sense is not clear to you, maybe you should ask about it (or, say, read the clarifying sections of David Albert's "QM and Experience") rather than parodying it.


In other words, what you actually see matches (within the relevant uncertainties) with what the theory says is actually happening. This is in stark contrast to MWI. According to MWI, the real state of the world does *not* have a person walking across your room, so your perception to the contrary is a *delusion*.



Please. When I say that MWI requires us to accept that our perceptual experience is delusional, I'm not just saying "MWI is fairly wacky". I use language carefully and precisely. MWI is fairly wacky, yes, but that is not the point at issue here.


The whole point I am making is that your last sentence, taken literally, is quite false. "The way we thought it was" surely includes things like the needles on experimental apparati in Germany in the 1920's swinging in particular directions, yes? Well, according to MWI, that (and a gazillion other things like it, including, as I've said, pretty much all of our perceptual experience of the world) never actually happened. In other words, it is a delusion. So is MWI "one way to explain" all the perceptual/empirical evidence that led to quantum mechanics? Literally speaking, no. It doesn't explain that evidence; it explains it away (so to speak). According to it, that evidence was all wrong.

You have to admit, that's a very uncomfortable (because circular) position for a theory to be in.



No, it isn't. At least, not in anything like the normal scientific sense.



So, it's stupid to believe that when I see a table in front of me, there's really, in external physical reality, a hunk of table-shaped stuff out there? Or that when I see the needle go right, that's because, really, there is a needle and it moved to the right?

I would ask you to seriously consider what is left of science (including in particular the alleged empirical evidence for MWI) if you take this seriously.

Hurkyl

You take an empirically successful principle (unitary evolution), and you push it to its logical conclusion -- in the theoretical domain, how can you get more scientific than that?

To the best of my knowledge, MWI is a theory about unitary evolution. That's it. Unlike your "curative asbestos-and-uranium sandwiches" (hey, weren't you objecting to parodies? ), MWI doesn't postulate anything new: it simply studies what follows from unitary evolution. And at any point, you could reintroduce wavefunction collapse and be doing orthodox quantum mechanics. (But, you would no longer be doing MWI)


I had previously been thinking that you meant "deluded" simply to refer to the fact we think we see a classical state, when the universe is in a quantum state. But I have absolutely no idea where you get things like:

: According to MWI, the real state of the world does *not* have a person walking across your room
: Well, according to MWI, that ... never actually happened.
: According to it, that evidence was all wrong.

selfAdjoint

People disagree that it's logical. Unitarity is surely a useful property, but making it the be-all of everything, at the cost of either "parallel worlds" or the possibility that people I see on the street are in a different state as far as their furshlugginer consciousness is concerned, is not best described as "logical" IMHO. And it still doesn't answer the question, how can QM operate, as evidently it does, completely hidden from human consciousness, say inside the Sun?

Farsight

setAI, hurkyl: I read the David Deutsche paper and have to say I didn't understand it. So I read it again, and again, and I still couldn't follow its thrust or see anything that "proved" the MWI. If either of you could post a link to an alternative paper or article I'd be grateful.

selfAdjoint

There is nothing that proves MWI, it's something that those who believe in it try to persuade you of. In other words it's like philosophy or religion: "Go on and faith will come to you."

Farsight

Er, no thanks.

setAI: can you post another link that demonstrates why MWI sounds likely or plausible?

setAI

http://xxx.lanl.gov/pdf/quant-ph/0303050

http://www.citebase.org/cgi-bin/cita...:gr-qc/9404013

Farsight

Thanks, setAI. Look, I don't mean to be rude, but I'm afraid they come over as "magicked out of the hat" leaping logic lubricated by bigword babble and psuedo-mathematics. If I missed a trick somewhere, apologies. But I am mathematically literate and I am smart. And I am in no way convinced of MWI by these links.

I remain deeply interested QM matters. Such as the "Quantum Eraser":

http://www.bottomlayer.com/bottom/ki...scully-web.htm

http://en.wikipedia.org/wiki/Delayed...quantum_eraser

"In terms of the conventional way of viewing the physical universe, this result seems disturbing. One possible explanation is that the causality of the second observation travels back through time to affect the outcome of the first observation. In other words, this is time travel. Oddly enough, quantum mechanics does not seem to have much of a problem with time travel. Similarly bizarre results have been shown in other experiments where we have spooky action at a distance..."

Unless somebody can tell me something better about MWI, I fancy the time travel.

Hurkyl

The only thing I'm really convinced of is that it is not necessary to assume that wavefunction collapse is a physical process.

Entangled states, quantum erasers, counterfactual computation... IMO none of that seems weird at all, unless you're working in a mindset that collapse happens as a physical process.

I first realized this during a (brief) introduction to quantum computing in one of my math courses: we were introduced to the CNOT gate whose action on a pair of qubits in basis states is given by:

In particular, if our second qubit is in the |0> state, then this is:

and the whole thing acts as if we had actually measured the first qubit and stored the result in the second qubit... except that a collapse didn't happen. e.g. on a superposition of |0> and |1>, we'd get have:

(a|0> + b|1>) |0>

on the left hand side, and:

a |0>|0> + b |1>|1>

on the right hand side.

If you try to imagine behaviors that measurements have... such as consistency, you'll find that these CNOT gates have that property. e.g.

if we make two different "measurements" of the firstqubit, the results are the same. Of course, I'm cheating by simply saying they're the same: I really should add another gate to this circuit to "measure" if they are the same... and if we did, we would find that the result of that measurement is always "yes", even if the original input is in a superposition of |0> and |1>.

Farsight

There's something very weird about the interference pattern appears at both detectors, hurkyl.

http://www.joot.com/dave/writings/ar...ookiness.shtml

Ah, I am but a blind man searching a thunderstorm for the lightning particle.

Farsight

Hurkyl:

I made a post on the "Electron Energy" thread and it's disappeared. It was nothing contentious, just a link to something I found when looking up infinite energy. This sort of thing has happened a few times. Is there some kind of priesthood god damn thought-police on this forum expunging any concepts that challenge dogma? And is this Physics, or the Catholic Church circa 1450?

selfAdjoint

If you read the guidelines, and every new poster has to sign that he or she read them, then you wouldn't have to ask. If you have a theory that challenges current science then it belongs on our independent research forum, and there are strict guidelines for appearing there, mainly to make sure the theories that are present there are serious and not just random garbage.

And linking to an obvious crank site (obvious to us even if not to you) is a no-no, and if you keep doing it you will be warned, and if you still don't stop, you'll be banned. Them's the rules at PF, and if you don't like them take your creative imagination elsewhere.

Farsight

All points noted, selfAdjoint. Sorry to interrupt the thread everybody.

UglyDuckling

Sorry I haven't replied earlier I don't get much chance to spend time on the forum.

The idea that there is backward in time causation seems to have crept into the interpretation of the proposed Bell Local Theory on its own accord. The theory itself does not contain this element. Therefore it should not be used as an argument for refuting the idea that electromagnetism is mediated by zero proper interval paths.

If we take two spatially separated quantum systems and place an observer in the vicinity of each then each observer will experience time progressing “normally” from the past to the future. For any given experimental set up and initial conditions the temporal evolution (relative to the subjective time of each observer) of the states quantum systems will be completely deterministic. The resulting state functions will provide the probabilities of measurable outcomes.

If we now consider an interaction between spatially separated systems! Let the donor emit energy of excitation at an event E1 and the acceptor receive the energy at an event E2. We know if we calculate the proper interval of separation between these two events then this has zero magnitude. In space-time these events are contiguous (Touching) and according to our proposed Bell local theory can interact directly with each other with out the need of a carrier particle., Thus in space-time events E1 and E2 can be regarded as a single event but appear separated because they are viewed by observers placed at different positions and time in the universe.

The ability for the two systems to interact depended on their states immediately before interaction (relative to the subjective times of the observers). These states were dependent on the local temporal evolution of the quantum systems. There was no backwards in time causal influence necessary to trigger the interaction. There is just a single event involving the direct transfer of energy between spatially separated but properly local systems and no backward in time causation.





You are correct I did make up the expression “Lorentz super-positioning", originally I called this idea “proper interval locality”, however I thought the word super-positioning might appeal more to specialist in quantum mechanics. I’m willing to accept it’s a “crazy phrase” and can cause confusion with the super-positioning of quantum states. Thanks for the advice.

However I’ll try and give a definition of the concept using the origin name..

Proper Interval Locality occurs when the proper interval of separation between events on the world-lines of quantum systems has zero magnitude. This occurs when, relative to a given inertial reference frame, the square of the temporal component of the proper interval is equal to minus the square of the spatial component of the spatial component of the proper interval. Under conditions of proper interval locality it is proposed that quantum systems can interact directly without requiring an intermediating particle/wave. Using this principle a method of electrodynamics can be developed which is free from the contradictions recognised in current theory.

UglyDuckling

Hi Hans

Your second expression is Euclidian and is not applicable to a universe characterised by the constancy of the speed of light relative to all inertial frames of reference. The interval between a pair of events in space-time must be calculated (for flat space-time) using the Minkowski Metric.


Your reasoning is correct any two events in space-time can be joined by zero interval paths. I suspect your instincts are telling you this is absurd every thing must happen at once!! However it can be the basis of a Bell local theory and leads directly to the development of the wave-function, interference and the violation of Bell’s inequality for light correlation experiments.

The idea of universal linkage between all events takes a little getting use to but can eventually lead to a simple elegant and beautiful theory of electromagnetism? I believe it to be worth investing a little intellectual capital to get your mind round it.

Cheers

Farsight

UglyDuckling: this sounds interesting. Are you basically saying: a photon travels at the "speed of light" so no time passes for a photon. Therefore it "instantly" connects A and C such that trying to locate it somewhere between A and C means you locate it at B, and it therefore connected A and B? So trying to locate it is like trying to locate a rod somewhere along its length? Is a rod the right analagy? Or should I try to think about a property with no length? Like, is determining the position of a photon as much use as trying to measure the length of a gallon?

Or, and utmost apologies, are we straying into "crank" territory here?

Anybody?