The Home Parallel Universe Test 754
Sam Sachdev writes "David Deutsch, a physcicist at Oxford, has designed a home test for parallel universes. Using a pin, a red laser pointer, a piece of paper, and a relatively dark room, he claims that the results from this experiment confirm the existence of parallel universes." Okay, so it may not really be proof of parallel universes, but it's a fun trick to try with a laser pointer nonetheless.
Isn't this just the double-slit experiment? (Score:5, Insightful)
Fabric of Reality?? (Score:5, Insightful)
Wavicles are fun (Score:2, Insightful)
http://www.cavendishscience.org/phys/tyoung/tyo
What's the photon/proton thing about (Score:5, Insightful)
Is this a joke article?
Summary (Score:2, Insightful)
Re:Wavicles are fun (Score:5, Insightful)
He is talking about the classical double slit experiment. The results of that experiment are correctly predicted by quantum physics because you need to treat photons as waves and not as particles here.
The author however wants to explain the results treating the photons as particles only. I must admit I have no idea why this leads him to the parallel universe theory.
In my opinion that theory is not needed here as we already have an excellent model (the quantum physics) that predicts those results extremely exactly. We must not forget that quantum theory (and its application in particle physics) is the most accurate theory / model in the world. No other theory other than quantum theory matches as exactly with the experimental results (up to 10 to the power of -9)!
Why this is suspicious: (Score:4, Insightful)
The moral of the story is... (Score:2, Insightful)
Is there any way to mod down the fool who wrote the article?
I RTFA and it SUCKs (Score:4, Insightful)
Time, I guess, to DTFE.
Re:Shadow Protons? (Score:2, Insightful)
There is nothing new here (Score:3, Insightful)
Even the idea that it is proof of parallel universes is not original. Michael Crichton made that claim in his book Timeline. It's an excellent book (despite the horrible movie loosely based on it), but it is fiction.
Jason
ProfQuotes [profquotes.com]
Re:I RTFA and it SUCKs (Score:3, Insightful)
The Author's Background (Score:3, Insightful)
Keyword- freelance
That noise is Karl Popper hitting 9,000 RPMs (Score:1, Insightful)
Its just a way of looking at things, not proof (Score:3, Insightful)
Deutch believes in multiple universes. He uses this belief to explain the results, but typically for Deutch he says the results prove his belief, which is nonsense. There are many other explanations and one of the strangest aspects of quantum mechanics is that there is probably no way to say which explanation is right. Some of the other explanations are equally weird: the Copenhagen interpretation says that particles only 'collapse' into definite positions when something looks at them. The Transactional interpretation (my favourite) explains the results by assuming that particles are continually interacting back and forth in time. Other ideas include the suggestion that quantum states collapse into what we see when things get large enough for gravity to be significant (to put it simply).
Of course, the most sensible interpretation is to take the scientifically humble attitude and say that we don't fully understand what is going on and can't explain it, rather than to arrogantly assume all results 'prove' your personal metaphysical beliefs.
Re:Fabric of Reality?? (Score:1, Insightful)
What you've described here is another valid interpretation. To be honest, I'm more prone to agree with the interpretation you've presented.
The problem is that you've presented this as an open-and-shut case, it is not.
Deutch's interpretation basically says this:
"Listen to yourself, you're talking about probability waves. In other words, you're talking about imaginary photons interfering with real ones. That's ludicrous! How on earth could something imaginary (like photons that could have been) interfere with something real? Answer: they can't; only real things can interfere with real things. Since we see the interference pattern here and there are no real things in our universe to explain it, the only rational solution is to posit the existence of real things in other universes."
Again, I disagree, but that'd Deutch's point, and it's a Pretty Good One.
Many Worlds is an attempt to answer the measurement problem. Another interpretation that solves the measurement problem and is imho rather elegant states that when we measure a system the measurement device becomes entangled with the system, so it enters a superposition of possible states as well. Naturally, since it's in a superposition of states it can't see all of the states, just whichever ones line up with it's particular wave function. This gives rise to the apparent collapse of the wave function.
Re:Fabric of Reality?? (Score:2, Insightful)
Re:Isn't this just the double-slit experiment? (Score:5, Insightful)
Apparently we don't detect 'parallel universes' until we do the four-slit experiment. Read the article - this is what the author states. Now IAARP* , but I can't understand why, unless the intensities or pattern spacings do not agree with the standard 4-point interference pattern, that there is any new physics here. If we see a result from two slits, we've already shown the wave nature of light.
One of the most glaring problems with the article is where the author states
"What should happen, or is expected to happen, is that the same pattern as with the two holes appears. Light beams, according to "Fabric of Reality", normally pass through each other unaffected. So, the same pattern as the two holes, should be repeated, only brighter and slightly blurred."
If we have a pattern, we already have light beams interfering. If light beams don't interfere, we should see no pattern. This is not, and never has been, the case! The four-source pattern is a consequence of the same physics as the two-source pattern.
I'd do a nice derivation, but maths in HTML never really works.
I think that author is just deeply confused as to what is going on here. He probably hasn't read David's book; if he has, he hasn't understtod it. Now I haven't read David's book either, but I have read his papers (he and I are in the same field) and I'm sure there's nothing in the literature about the four-source pattern having any new physics not observable in the two-source pattern.
In fact, we set students multiple-source interference problems in optics in the first and second years, and no-one's noticed anything radically new happening there!
* (I am a research physicist)
It's all about models (Score:5, Insightful)
So when a bunch of photons show up as an interference pattern, they think of it as waves and the model produces accurate and useful results. When people knock electrons off atoms with gamma rays, they think of the photons as particles and the model produces accurate and useful results. When the two models come together, people have the hardest time understanding it because they forgot the most elementary rule of models:
ALL MODELS ARE WRONG.
As I understand it, under the standard model, we figure out if a photon interacts with another particle by integrating over the set of all possible paths the photon can take in the meantime, producing a probability. That seems like a pretty sound model to me. Does this model require more than one photon to explain diffraction? Nope. Does it talk about waves and interference? Nope. It doesn't mention parallel universes either. This is the model that scientists started using when they realized that both the particle and the wave models were not only wrong, but they didn't always produce useful results.
The problem I have with the claim that this is proof of parallel universes is that parallel universes doesn't add anything to the existing theory. Now, if the parallel universe theory were to predict something disagreeing with the standard model, anything at all whatsoever, it would be useful. However, as it stands, I see the theory as just a more complicated explanation of the standard model. It may be true, but it doesn't seem useful, and usefulness is the only desirable trait in a model.
No scientist understands the laws of the universe, scientists don't even agree on the laws. They don't agree on string theory, on the existance of black holes, on the fate of the universe, on the presense of dark matter, or interpretation of quantum mechanics. If anyone were to ask me about any of those, I would give a resounding maybe. Heck, there are scientists proposing revisions of Newton's law F = m*a to explain discrepancies in galactic rotation.
I just get sick of scientists peddling useless but imaginative models to the public like this. That's what philosophers / fiction writers are for.
Re:Since I can't see air it must be another univer (Score:4, Insightful)
Re:Since I can't see air it must be another univer (Score:5, Insightful)
Of course, in daily physics speak, one talks about 'the electrons that hit the surface' etc. because there is a underlying theory which describes most of the experiments with sufficient precision. Daily physics is simply more like engineering than thinking about the world itself.
But electron's are only human-invented concepts. Very successfull concepts, indeed. But only concepts. Maybe they're 'really resonances of some weird field' yet to be discovered. But what are resonances and 'this weird field'? They're also invented concepts. Concepts to aid 'understanding'.
Many of my fellows (I'm studying physics) just believe they're electrons which properties and formulas to describe them. I don't. I take them as always incomplete, yet successful and helpful models of reality. Maybe this is just an arrogant statement and my 'open-mindedness' now brands me a crackpot to be modded down.
But I am no crackpot. I don't believe in UFOs and stuff.
Regarding the 'multiverses': IMHO, one very important question remains: How you as yourself evolve in this multiverse. What decides which part you take in the multiverse? Why is it that you only see one universe, that you only exist in one universe? What decices where you/your conscience goes? Maybe this is the free will? I don't know but this bothers me.
Re:Isn't this just the double-slit experiment? (Score:2, Insightful)
The article describes what happens if you only send single photons (technically possible, but normally not in your basement!). They also interfere!
That's a basic phenomenon (the old 'particle-wave-duality') mathematically well described (and already exploited) but IMHO not yet really 'understood' in quantum mechanics.
Re:Since I can't see air it must be another univer (Score:5, Insightful)
Quantum Physics is the single most successful theory in the history of science.
The interpretation of Quantum Physics is the single least scientific endeavour known to man.
It was fine for great physicists to propose these interpretations, but for anyone to accept them as "real", or to say one interpretation is more "correct" than another, is wrong-headed. What gets me is the people who then springboard off their favourite interpretation to make wild sweeping extrapolations with no scientific backing whatsoever.
Like, "this defines consciousness".
Worst Writer EVER! (Score:3, Insightful)
Re:Since I can't see air it must be another univer (Score:4, Insightful)
Now, for electrons, it's the same: In all experiments so far they behave as if they were exactly what the theory describes. And therefore they are real, in the same sense as the computer in front of you is real.
Re:Actually it was on Star Trek: TNG (Score:4, Insightful)
It should be added that most physicists disagree with Deutsch's conclusion that what is detected in this experiment is another universe. For brevity's sake, the argument against can be summarized as, there is something interfering with the light in this experiment, why does it have to be a parallel universe? Why can't it be just be left to something that we don't yet understand?
Re:Since I can't see air it must be another univer (Score:4, Insightful)
Re:Utter tripe (Score:2, Insightful)
Re:Isn't this just the double-slit experiment? (Score:3, Insightful)
The author of the article doesn't seem to understand the experiment himself. Probably he's misunderstanding Deutsch, whom he's apparently just paraphrasing. The whole experiment he's describing is simply a classical diffraction experiment, and can be explained using only the plain old classical wave theory of light. There's nothing quantum mechanical about it, so it doesn't have anything to do with the many-worlds interpretation of quantum mechanics. The part about changing from two pinholes to four is just nonsense. The case with two pinholes is classical physics that's been understood for almost 200 years. The case with four pinholes is also classical physics that's been understood for almost 200 years. Maybe Deutsch had an interesting point to make about the comparison, but if so, then the author of the article doesn't seem to have understood it.
The experiment described in chapter 2 of this book [lightandmatter.com] is the simplest I know of if you actually want to see the quantum stuff going on. Basically you just need to modify a digital camera. I haven't done it myself; the figures in my book are from a profesor at Princeton who built it as a classroom demonstration.
Even if you do the version of the experiment that does prove that light is simultaneously a particle and a wave, that doesn't constitute a proof of the many-worlds interpretation of quantum mechanics. There are various interpretations of quantum mechanics, all of which make identical predictions about experiments. Most people think and talk about it using either the Copenhagen interpretation or the many-worlds interpretation. Neither is right or wrong, because neither one makes a prediction that contradicts the other.
Re:Jeez (Score:2, Insightful)
As I read this he's calling the light that passes through the holes "shadows" that disappear by going dark.
Re:Since I can't see air it must be another univer (Score:5, Insightful)
The parent post is right: quantum mechanics is one of the most successful theories in the history of science. By successful, I mean that it (a) accurately predicted measurements that were not explainable by previous theories, (b) has not predicted any results that are demonstrably incorrect, and (c) did all of this with a fairly simple (minimal) formulation.
Those three statements can be made about any solid theory, but QM has one unique characteristic. Unlike (say) Mendellian genetics, which challenges us with the difficult (but tractable) problem of "How did a biochemical mechanism for inheritence of traits ever come to be?", QM challenges us with "Why does the universe behave in a way which is contrary to our fundamental sense of reality?" This is not a knock against the theory, though. It just raises the deeper question: "Why should we assume that *our* fundamental sense of reality f-ing matters?" Despite almost a century of incomplete attempts to understand what quantum mechanics "means", the theory itself keeps on keepin' on - unfailingly accurate in its predictions, blithely indifferent to its metaphysical ramifications.
A different post in this thread makes the key point for grasping the various interpretations of QM: they are just *interpretations*. They have no bearing on what is "real" or "not real". All that is real (AFAWCT) is that the predictions of QM are accurate. Whether that means phantom universes, wave-particle duality, or little green men, is really of no importance until one of those interpretations leads to novel, verifiable predictions.
The article was not only an atrocious and pompous bit of writing, it was bad reporting. To represent this scientist's thesis as "novel" or even "scientific" just shows that the author doesn't know beans about the history of quantum physics.
Disclaimer: IWOAPUTDCB (I was only a physicist until the Dot-com boom).
-1 redundant, but this guy needs an answer (Score:4, Insightful)
'Fraid not, chief. Water waves are vast assemblages. Individual photons are ... well ... individual photons. The double slit experiment works when the photons are fired through the slits one at a time. This, if you properly grok it, is FUCKING WEIRD.
Re:Since I can't see air it must be another univer (Score:3, Insightful)
The poster to whom you are replying phrased his comment flippantly, but his criticism is correct. Deutsch's argument is, "I can't explain this, therefore it is inexplicable without introducing parallel universes". The conclusion simply does not follow from the premise.
Compare, "I can't think of any way in which you could build a ship out of materials that are heavier than water, therefore ships made of iron are impossible". An argument that was taken seriously once. Or Kant's argument that space and time were both (separately) absolute, because he couldn't imagine otherwise.
My problem with Schrödingers cat (Score:3, Insightful)
Re:Since I can't see air it must be another univer (Score:3, Insightful)
Ah, but what if no one was looking at the detectors? Could they exist in a superposition? That's the paradox of Schrodinger's Cat.
And what exactly is a "macroscopic" system? Is it not composed of quantum particles?
Collapsing the wave function when it interacts with a "macroscopic" observer is no more of an explanation than interaction with a "conscious" observer: neither "macroscopic" nor "conscious" are properties that are defined within quantum theory.
Bringing consciousness back into it at least brings us back to an oft-forgotten principle: all physical law is simply a means of grouping and prediciting observations that we (conscious observers) make about the objective universe. Any interpretation past that point is dancing on thin ice.
Re:Since I can't see air it must be another univer (Score:1, Insightful)
quite sound. As well Feynman came up with the Feynman diagrams and eventually the calculations to ground them in but the idea of antiparticles as particles moving backwards in time comes from Dirac. Feynman simply took it to a "logical" conclusion and using his different "tool box" developed a completely different(but equivalent) way of looking at quantum mechanics.
Re: Isn't this just the double-slit experiment? (Score:3, Insightful)
Well, yes and no. If you measure the location of the single photon, you'll basically find it only in a single place. You would get the standard wave diffraction pattern if you measured many instances of 'single photons' and formed their expectation value that way. What exists before you measure it is the quantum wave-function. It's collapsed into a single eigenstate upon measurement.
I believe the explanation for the double-slit experiment in the many-worlds interpretation of QM boils down to the photon interfering with all the corresponding photons in all the other universes...
Regarding the many-universe theory, I think of it in terms of the variety of possible values. Ie, in universe A the photon is measured as being at position 1. In univese B the same photon is measured as being at position 2. The 'expectation value' integrated over these universes as a function of position would then coincide with the expectation value of the position measurement of the wavefunction.
At least that's how I understood it. I could be wrong, I haven't thought about many universe theory since writing a paper for it for my undergraduate quantum class back in 1996 (the professor didn't like the 'pseudeoscience' of it and gave me a bad grade on the paper). Anyway, I'm a grad student in physics now, but I haven't given much thought to this philosophizing of the quantum wavefunction lately.