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Testing Einstein's 'Spooky Action at a Distance'
smooth wombat writes "Travelling to a time in the past is, as far as we know, not possible. However, Einstein postulated a faster-than-light effect known as 'spooky action at a distance'. The problem is, how do you test for such an effect? That test may now be here. If all goes well, hopefully by September 15th, John Cramer will have experimented with a beam of laser light which has been split in two to test Einstein's idea. While he is only testing the quantum entanglement portion, changing one light beam and having the same change made in the other beam, his experiment might show that a change made in one beam shows up in the other beam before he actually makes the change."
Didn't the Aspect Experiment back in the '80s demonstrate this effect?
General Relativity: Space-time tells matter where to go; Matter tells space-time what shape to be.
Does this mean that once the effect shows up in the one light beam, before he does it in the other light beam, he is somehow locked in to his future actions? If not, what happens if he just turns off the device?
But we've already done it: Elitzur-Vaidman bomb-testing problem
At the bottom, it says that the equivalent experiment has already been performed, and TFA sounds like it is nearly the same experiment.
Look, posting this article made this other article from June 12 with exactly the same content get posted!
The theory works!
How we know is more important than what we know.
Spooky Action at a Distance describes my sex life exactly.
John Cramer, the designer of the experiment, is really quite a colorful guy. He last got the attention of the press by simulating the sound of the big bang using Mathematica. Useless research of course, but who wouldn't laugh hearing that the big bang sounded like "large jet plane 100 feet off the ground flying over your house in the middle of the night?" At heart this guy is a physics hacker (in the true sense of the word hacker).
He also writes science fiction, so you can tell he completely enjoys science. Betcha anything he's doing this experiment, not because he thinks it will work, but just 'cause he wants to see what will happen. I can totally agree with that. It's the right reason to do research.
--
Looking for a C/C++ job in Silicon Valley?
Qxe4
Well.... he would be successful with his "spooky action", if not for those meddlesome kids!
Don't be ridiculous! We are all practicing time travel into the future right now... it's just taking longer than anticipated, at any moment I will be in the future, reading this post.
Sgt. Doom, Galactic Temporal Patrol
I, myself, am a time traveler from the past. I've been journeying into the future at a rate of sixty seconds per minute.
As others have pointed out, we are in fact time travelling all of the time. However, to time travel as I'm sure you mean, significantly faster than our surroundings, Einsteins time dilation does the trick nicely, its just a matter of propulsion technology.
Note that also, too, we can observe the past due to the finite speed of light. Thus, given our current knowledge it is always possible to travel to the future and observe the past, but never the other way around (except maybe at quantum scales as discussed in TFA).
This, according to my random ponderings makes me think that if its possible to travel to the past, it will also be possible to observe the future, and in fact in some respects, they could be two aspects of the same thing.
Just for the record, I'm not a physicist, so beyond the first couple of facts this is all random amateur speculation.
"...his experiment might show that a change made in one beam shows up in the other beam before he actually makes the change...."
What happens when he notices the change, before he makes the change, and changes his mind and doesn't make the change?
-CF
Suppose an astronaut travels away from the earth at 99.9% of the speed of light. According to relativity, if he ever returns then everyone on earth will have aged considerably more than he has. But he has to turn around at some point in order for this to happen, hence he has to accelerate. And it doesn't take any reference points to judge that acceleration, so you can in effect say that he has travelled into (Earth's) future, and that the entire Earth has not travelled into the past.
There is a whole school of thought that "time" is just our perception, much like we perceive motion by flipping a flip-book of images. The images are already there and we see the progression. (Similarly, humans perceive temperature differences, pressure differences, etc, and not the temperature or pressure itself?) It is a kind of scary concept in that it seems to mean that free will is an illusion. There was a great article on different proposals on the nature of time in Scientific American about 5 years back.
so I've just sat down and made myself a nice cup of instant tea. The list of ingredients on the teabag's packet say it contains 'Thiotimoline, resublimated, product of China.'
so, let's say Beam A and B are split from one beam.. you change beam A, B changes before you changed A so then B's change should change A before you changed it and it would recur ...
so how would you be able to measure a change that would effectively be happening in an infinitely small amount of time?
Einstein formulated the theory with 2 colleagues, Podolsky and Rosen.
It's called the EPR Paradox in the scientific community.
Einstein was no fan of it, and he believed it was a way to point out how silly the idea of Quantum Mechanics was, but he was very much the discoverer of it.
This is as important to understanding Einstein as "God does not play at dice", his basic objection to the probability implications of QM and EPR.
Well, the damage could in fact be limited to our own local galaxy. On the other hand, he could simply go into shock and pass out before Marty and Doc find him.
kurzweil_freak
5th Kyu Genbukan Ninpo/KJJR student
Be the darkness that allows the light to shine.
Relatively speaking, of course.
The images are already there and we see the progression. It is a kind of scary concept in that it seems to mean that free will is an illusion.
Only if you assume that their is only one set of ordered images. If every possible image is in the 'book' and every page is 'adjacently linked' to every other page that differed 'only a little', then free will may determine which adjacent page you (individually or perhaps your entire universes shared consciousness) go to at each step.
"Observations on entangled states naively appear to conflict with the property of relativity that information cannot be transferred faster than the speed of light. Although two entangled systems appear to interact across large spatial separations, no useful information can be transmitted in this way, so causality cannot be violated through entanglement. This is the statement of no communication theorem."
-- Wikipedia article on Spooky Action
I'd guess we could never create such a paradox even if the effect is real.
Classical relativity imposes one set of constraints, and quantum mechanics another. Einstein was bothered because it seemed like the classical limits (think "light cone") would be inapplicable here. Quantum physics requires us to consider the actual mechanisms by which we measure and communicate as PART of the experiment.
Even if it works out that information at point B shows up "before" (in the same reference frame) an action at point A causes that message to be sent... it's possible that there's no practical way to detect this fact and use it in any way that would make for a "paradox." It may be that the best we can do is *record* the fact that such a backward transmission happened.
Example: Your instrument records a signal at B "before" the timestamp of the interference of the beam at A. This shows that entanglement is real, and gets you out of the "light cone" limits of classical relativity, which is what bothered Einstein. But if you go further and try to create a logical paradox, by using this information at A to stop the sending of the signal, then you will likely run into other, quantum mechanical limits... E.g. the actual means by which you detect the signal at B and send that information back to A will likely overwhelm or destroy whatever time differences we're talking about, bringing them back within classical limits...
This would be similar to things like the particle/wave experiments, where the experimental apparatus itself affects the outcome of the experiment.
So while something like "instantaneous" or even slightly "backward in time" messages may seem spooky in some ways may be possible, I'd bet that the time differences we're talking about wouldn't be large enough to make for any of the paradoxes people imagine using sci-fi based "time travel" notions.
When sending any signal, they need to consider that the signal grows weaker the further it travels. This is obvious with 3-dimensional travel but when adding that 4th dimension, it degragates exponentially. They also need to consider the displacement that occurs as well. Obviously, the Earth is not in the same exact place a few seconds ago as it is now. As such, they would need to conpensate for that as well. They should also consider that there is bound to be interference by all of the signals bouncing around these days and should use an untouched frequency. And finally, they should have the reciever up and running way BEFORE they ever attempt to send that signal.
As for avoiding paradoxes, I would suggest creating the message/recording/whatever and sending it to a point before it was sent but AFTER it was created. Also, they would need to have the device set up to send the signal no matter what, where transmission cannot be interupted after reception. Otherwise, the paradox will stop the reception from ever happening. I like to think of paradoxes as time's way of fixing itself by fizzling out/destroying such events from ever occuring. I would best describe one as a trick knot in a string (time) where each time the loop reoccurs (from happening to not happening to happening, etc) the string tightens and the loop shrinks until it 'pops' out of existance and the experiment fails. If scientists can avoid causing a paradox, their experiment will be a success otherwise time itself will adjust to keep it from happening at all.
DEAD DEAD DEAD DELETE ME
Relativistic physics imply a sort of eternalism, whereby nothing is really "moving" through time at all - spacetime is a four-dimensional construct which is itself timeless, inasmuch as the four-dimensional spacetime does not change across some fifth "hypertime" dimension, so nothing in 4D spacetime really "moves"; there are just changes across the time dimension of spacetime (as a cone "narrows" in the vertical dimension even when it's not "changing" when considered as a 3D object in time, things "change" across the time dimension of spacetime even though spacetime itself never change when considered as a 4D object). So in a sense, yes, if the relativistic model is completely correct, we cannot travel to the past OR to the future, because nothing's really moving at all, four-dimensionally. Things are just different in the four-dimensional construct of spacetime at different points in time.
...and your particles then reverse their temporal direction, travel haphazardly back in time, safely within the backward-moving containment field, until such a point as they collide with an identical bunch of antiparticles (or, viewed in forward time, regular matter), annihilating with them, or as viewed in 4D time, turning around and becoming them, and then being reassembled by some helpful scienti
So when you talk about backward time travel, really all you're talking about is backward causation: can I, now, make it the case that something happened in the past, the way I seem to make it the case that things will happen in the future? This, interestingly enough, happens all the time, for antimatter is nothing but time-reversed matter. An electron and a positron being created and then annihilating with each other looks, in the four-dimensional model of spacetime, as a causal loop; the electron moves forward in time, then releases a ton of energy and turns around to go back in time - or, when you play things the other direction, a ton of energy converges on the electron to make it turn around. this electron (now with various properties reversed when viewed "forward", appearing to us as a positron) then travels back in time until it turns around, releasing a ton of energy - or, viewed the other way around in "forward" time, when a ton of energy converges upon it, turning it around. Of course, as this particle doesn't exist in times before or after its turn-around points, it doesn't look to us like we shoved a bunch of energy in with a positron and turned it into an electron; it looks to us like we shoved a bunch of energy together and a positron and an electron were created.
So, if you were to successfully travel back in time, there would have to be a backward-moving anti-you around somewhere, with whom you would have to annihilate, perfectly; from your perspective the world would then seem as antimatter, moving backward in time, and you'd somehow have to avoid annihilating yourself by touching anything, get back to the past that you want to go to, and then find another perfect anti-you to annihilate with to turn around. In forward time, this would mean that somehow, a copy of you with your future memories, and his antimatter clone, would have to be created somehow in the past; the antimatter clone would then have to be slowly changed and preserved in a precise way such that its evolution is the reverse of the normal processes that a person witnessing an antimatter universe moving backward around him would undergo, until it reaches such a state that it is a precise antimatter clone of future-you at the moment that future-you collides with it. Of course, since experiencing the trip backwards in time really isn't all that important, then the people in the past could just create a bunch of matter and antimatter, arrange the matter into a perfect clone of what you'll be like in the future when you decide to travel back in time, and then just leave the vat of antimatter in containment until that time comes that you want to travel back in time, whereupon you jump into the vat of antimatter and are annihilated...
-Forrest Cameranesi, Geek of all Trades
"I am Sam. Sam I am. I do not like trolls, flames, or spam."
Beam A does some stuff. Beam B does some corresponding stuff. Sounds like cause and effect to me.
...or equally, we can say that invisibly small pixies used time machines to do all this tweaking of beams...
Now either we can throw Copenhagen away, and state that B must have anticipated what A was going to do, and change B's own state 'in advance,' which appears to be what all the hullabaloo is about here...
But to some dude tweaking A and watching AND IN ALL CIRCUMSTANCES -WAITING- to see what happens to B... it doesn't matter what the mechanism is. Decoherence, Bell, pixies, or whatever, there is no way to surface the mechanism and use it to influence the chain of events, with time's arrow or against it.
If you are watching B there is no way to confirm B's behaviour relates to A, unless you also know what A did and you sit down and correlate it. In other words you cannot infer anything from B until you have looked at what A was doing anyhow...
Everyone is very free with the word 'before' in this discussion... before with regard to whom, what cones, and what worldlines?
"... and more and more now there are all kinds of electronic goodies available" -- Pink Floyd 1972
In quantum entanglement you have to objects with an entangled quantum state. That is, one of their properties is always the same (or always the opposite, depending on the kind of entanglement). On the other hand, this property is not already fixed when the objects get separated. Only when you measure the state of one particle you actually stipulate its state, and due to entanglement the state of the other partcle as well. As this happens instantaneous an the objects might be separated by a great distance, you get this 'spooky action at a distance'.
But, as been shown before, since you have no influence on the outcome of the measurement, there is no data tranmission involved (and also no reverse causality).
The article claims, that one can actually set the state of one object at will, thereby forcing the other object to have the same predetermined state. The problem is, that while you can actually force a light beam to behave like a particle (when you look at it how it behaves as a particle) or to behave like a wave (when you look at it how it behaves as a wave), and this actually has an effect on the entangled beam, it is not possible to measure if a light beam behaves like a particle or a wave!
Let's say you make the two slit experiment and observe which slit the beam will choose (thereby forcing the beam to behave like a particle). If you make the same experiment on the entangled beam, you will observe, that it will go through the same slit. (This is an ordinary EPR experiment without faster than light communication and reverse causality). If, on the other hand, you choose to look at the entangled beam as it behaves as a wave, it will behave as a wave. It still has both, the particle and the wave nature!
Unlike the spin, that could be either up or down, the particle or wave nature of a quantum object are two properties that coexists!
I apologize for the colorful title, but I can not describe my feelings towards the so called theorem of 'no communication faster than light' in any other way. There are no time paradoxes if FTL communication exists, for the simple reason that when an event happens, it happens for all the universe. The fact that photons would not have arrived to the FTL communication target when the FTL signal reaches that target is totally irrelevant. And there is no way to perceive an event before it happens and change the outcome, for the single reason that effect always follows cause. So even if FTL communication is real, there would not be possible to avoid doing events that already have happened, for the simple reason that the events have already happened.
A big criticism of quantum mechanics (still) is that nobody is exactly sure the minimum you have to do to one entangled particle to "measure" it, which determines what the person with the other entangled particle will he when he "measures" his particle. Schrodinger's cat paradox has never beeon completely satisfactorily answered. The existance of quantum entanglement is well established, though.
Nobody has ever found a way to use entangled particles to send FTL messages. In principle it is impossible. I have never even heard anybody else but this guy musing about ways it might be possible.
Where do you get a laser that produces entangled pairs with the ability to separate the pairs into 2 coherent beams?
Then from TFA we have this:
This guy doesn't think that the detector for B will "fiddle" with the photons at A before they reach their fiddler?He also seems to be getting money from people who believe his BS. Not to mention publicity.
If someone honestly believed they could send information back in time, the logical thing to do is fund the experiment any way you can while keeping it secret. You recover the funds by playing the stock market using future data (minutes to hours is the required time frame here). You keep it secret so "they" don't come after you - for whatever "they" you may be concerned about.
Also, for the record, while Einstein used the expression "spooky action at a distance", he did not "postulate faster than light" action. In fact, Einstein was intent on disproving the validity of quantum mechanics and dismissed many theories associated with QM, thus the use of the 'scientific' term 'spooky'.
Why would FTL have implications for conservation of energy?
As a serious question, I still don't understand why light speed is the limit - my understanding of relativity goes that it starts with the assumption that light is the fastest thing and then moves from there. This is them backed up by all the observations we have, so it is so far an excellent theory.
So the thought experiment I like is, suppose there was an intelligent fish that was blind and used sound to communicate. This fish was intelligent enough to develop a theory of relativity based upon sound. All the experiments and observations he could perform would support his assumption that sound was the fastest thing possible.
So why would the fish discovering electricity violate the conservation of energy?
Why cannot there be signals in nature that do travel faster than light, they just don't occur in any phenomenon that we currently observe.
Now if we can't observe them or any repercussion of them then that's as good as not existing (for the moment). My understanding goes that if entanglement shows some FTL behaviour then that doesn't invalidate relativity, it just shows that relativity isn't a complete description of the entire universe. But we knew that already.
"The weirdest thing about a mind, is that every answer that you find, is the basis of a brand new cliche" -
The wrong points are so many, I will name just a few.
The idea that photons (and electrons) are both waves and particles have nothing to do with quantum entanglement.
The "being a particle or a wave" property is not a physically observable one. It's not like spin, position or momentum.
All photons are waves. period. They can be counted due to indetermination principle, which provides that the electromagnetic field moves around orbits in the configuration space that are quantized. This has nothing to do with slits.
Moreover every "particle" is just a field which evolves like a wave. The particle-like behaviour comes in some particular conditions, under which the field has a compact spike in one position and is quite absent in any other position. This provides that it can be seen as a single point moving.
Still its equations are those of a wave.
Saying "a superposition of it being a particle or a wave" is just like saying that we can choose whether it will follow Galilei's or Einstein's relativity. It will follow Einstein's. In some cases it will seem it is following Galilei's, it is still following Einstein's.
This is nothing but a sign of how badly the experiment is explained. Yet it gives some suspects.
To confirm that this is not science I could point out that even if he will use spin (a much simpler and precise measure, and it is even a proper observable) he will demonstrate nothing.
Or that no energy transport will happen, so it's not really violation of causality.
Or that the two photons start together so that they interacted while causality violation require they did not.
Or that he will not be able to choose which result to get from signal A after signal B will be measured, so no paradox is involved (RTFA for definitions).
Or that he failed to provide calculations of how this thing works. Physics is not done with buzzwords. That's interpretation. You can't do physics by reading divulgative works nor understand how it really works. A good divulgative work explains nothing but the thing it speaks of and cannot be used as a source for experiments. Nothing can be logically deduced from buzzwords. E.g. the "ball over cloth" explaination of general relativity does not suggest that you can "cut the cloth". This guy is doing this kind of things.
Instead I will just point out one of the first lines in the article: "thanks in part to tens of thousands of dollars in contributions sent in by his fans".
People, please...
I've been reading up on and following this experiment for a while now. Personally, I don't think it will "work" in the sense that back-time signaling will be demonstrated. However, the experiment is still well worth doing, because we learn as much from how it "fails" as from success. Plus, it's just so interesting.
The proposed experiment is based on another experiment by B. Dopfer that has already been done and the results published. The original experiment shone a UV laser into a special crystal that split each incoming photon into two entangled photon going in different directions (you need a laser to get the right frequency of light into the crystal.) One photon (B) went through a double-slit and then to a, well, camera. You expect to see one of two patterns on the detector: if the photon is acting like a particle, then there's a 'hump'. If it's acting like a wave, there will be a diffraction pattern.
Now the other photon (A), goes through a lens and onto another detector. With the lens in the right position, you can observe A and tell which slit photon B went through. Move the lens and you can't tell anymore. What's interesting is that the pattern detected for B depends on where the lens is at detector A. This is exactly the 'spooky action at a distance' that Einstein pointed out.
Now, the original experiment filtered out all the noise by using a 'coincidence detector'. This also, in effect, re-synchronized the two signals via classical communications, eliminating any exciting possibilities like FTL communication. Unfortunately, the Dopfer paper doesn't say what happens without the coincidence detector.
Cramer is proposing two modifications to the Dopfer experiment.
First is to remove the coincidence detector. This will degrade the pattern that shows up at detector B, but (according to the QM math), not enough to make it go away. That means that a change in the setup at detector A will 'instantly' effect the pattern seen at detector B. Simply by looking at what pattern is seen at B, you can tell what the physical setup is at A.
Even if this is as far as the experiment goes, it will be extraordinary. Theoretically (yes, I know) A and B can be as far apart as you want, far enough to demonstrate that FTL communication is taking place.
The second modification that Cramer is proposing is even more radical. If you look closely at the original experiment, you can see something really unusual: the distance that photon B travels to it's detector is SHORTER than the distance photon A travels to it's detector. So what? So it looks like a change in how A is measured effects the measurement of B, even if B is measured before changing A. This is quite a bit like the 'delayed choice' experiment, except with much more measurable results.
Now the difference in path lengths between A and B in the original Dopfer experiment was on the order of centimeters, too short to measure directly. Cramer wants to route the A photons through a fiber optic cable, introducing enough delay between the A and B detectors that it can be measured. This is where the 'retrocausality' (I hate that term) comes in.
I doubt (and I'm pretty sure Cramer is skeptical too) that back-time signaling can be demonstrated. But you can work the experiment just via the math, using standard QM equations, to see what the predicted outcome is. And there's nothing in the math (so far) that prevents the experiment from working. QM predicts that it will work. If the experiment doesn't work, then we learn more about Quantum Mechanics. If it only partially works, then we get FTL communication. If it goes all the way, we've invented time travel (for information, anyway).
THAT'S why the experiment is so fascinating.
Now wait for it....
was 'Time Cop'
The Kruger Dunning explains most post on