No. The anthropic principle/branching universes theory explains nothing, and in fact is so utterly unfalsifiable it's kind of surprising intelligent people take it seriously.
Branching universes need not be falsifiable to be taken seriously, because that's not the theory. Rather it's a consequence of a theory (evolution of Schrödinger's equation sans collapse) and that theory is very falsifiable. In order for a theory to be falsifiable, you don't need all aspects of the theory to be falsifiable, just one. And branching universes is a prediction of a theory that has experimental support.
Let me take a non-quantum example to make the argument in a more intuitive setting. If we send out a spaceship at a high speed away from Earth, due to the ongoing expansion of the universe eventually the spaceship will be far enough away that the space between Earth and the spaceship will be expanding faster than the the speed of light, and hence the future light cones of the Earth and the spaceship will not intersect. There's no experiment we can do on Earth that could give us information about the spaceship once the spaceship hits this point of no return, but we still take seriously the proposition that the spaceship is still "real" and doing well because we have a broader theory (i.e. all of physics) that predicts it, even if we can't test this specific prediction.
(I view these two scenarios as being superficially dissimilar, but under the surface fairly similar. In each there is some element of "realness" that is predicted by theory but inaccessible to measurement. Only one is intuitive and the other is not.)
Putting aside a recent claim that the universe's expansion isn't really accelerating - and instead someone forgot to plug spacetime dilation into the cosmological equations - we're still left with the issue that once the space probe leaves our light-cone we can't know that it wasn't hit by an asteroid.
That's of course not the point of the thought experiment. Just the mass-energy and "realness" of the spaceship after it leaves causal contact with Earth is enough.
Consider the statement:
"Once any object gets far enough away from me that our future light cones do not intersect, it ceases to exist."
And compare with the statement:
"Once any configuration gets so far away from my configuration in configuration space that I can't experimentally detect it, it ceases to exist via waveform collapse."
The Copenhagen Interpretation is claiming something akin to the second statement, but that seems to me to be logically isomorphic to the first statement, of which our intuitions are much better at grasping the problems.
No. The anthropic principle/branching universes theory explains nothing, and in fact is so utterly unfalsifiable it's kind of surprising intelligent people take it seriously.
If you assume that the observer is described by quantum mechanics, then the Everett Interpretation is logically required to be true. If you want to argue for anything else, then you need to explain why you, the observer, are not described by our best scientific theory.
That's a pretty good reason to take the theory seriously.
> If you assume that the observer is described by quantum mechanics, then the Everett Interpretation is logically required to be true. If you want to argue for anything else, then you need to explain why you, the observer, are not described by our best scientific theory. That's a pretty good reason to take the theory seriously.
Arthur Conan Doyle notwithstanding, in science the truth is not arrived at by eliminating the alternatives. Science requires positive evidence -- absence of contrary evidence doesn't support a given outlook. Were this not true, Bigfoot and the Loch Ness monster would win acceptance through lack of contrary evidence.
> ... the Everett Interpretation is logically required to be true.
In science, nothing ever becomes true, but some things become false. Philosopher David Hume summarized this outlook by saying, "No amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion."
On that basis, and assuming we're still discussing physics, nothing is "logically required to be true." That's not science, it's philosophy.
> If you assume that the observer is described by quantum mechanics, then the Everett Interpretation is logically required to be true. If you want to argue for anything else, then you need to explain why you, the observer, are not described by our best scientific theory. That's a pretty good reason to take the theory seriously.
Arthur Conan Doyle notwithstanding, in science the truth is not arrived at by eliminating the alternatives. Science requires positive evidence -- absence of contrary evidence doesn't support a given outlook. Were this not true, Bigfoot and the Loch Ness monster would win acceptance through lack of contrary evidence.
How much science do you actually know? Because this sounds like philosophical twaddle that sounds good but makes no sense. If you seek positive proof of everything, then you can never generalize from experience at all. Every day is logically a new day, every object a new object and you have to rethink all of your assumptions at every step.
Science does not do this. Instead it tries to produce precise and general theories, tries to test them to destruction, and as they fail to be destroyed, assume them more and more broadly (while testing what we can in every detail that we can).
> ... the Everett Interpretation is logically required to be true.
In science, nothing ever becomes true, but some things become false. Philosopher David Hume summarized this outlook by saying, "No amount of observations of white swans can allow the inference that all swans are white, but the observation of a single black swan is sufficient to refute that conclusion."
Sorry, but you fail at basic logic. It is absolutely valid in science to ask, "What is the consequence if this theory applied to that system."
The consequence in quantum mechanics of a simple quantum mechanical experiment interacting with a complex quantum mechanical system is that the complex quantum mechanical system should be thrown into a superposition of quantum mechanical states that cannot meaningfully interact thanks to well-understood thermodynamic principles.
Whether this is an accurate description of the world is another question. However we've had several hundred years of spectacular success from assuming that the world is described by our best scientific theories, and then testing them as best we can - even though it means accepting things we cannot test at the moment. If we extend that principle to the present moment, we're forced to the Everett Interpretation. And if that turns out to be incorrect in some fundamental level, it is a basic fact that, to the extent that quantum mechanics does describe that system, the Everett Interpretation is true for it.
On that basis, and assuming we're still discussing physics, nothing is "logically required to be true." That's not science, it's philosophy.
You just failed at basic logic. I made a statement of the form, "If A, then B." This is a statement of math, not science, and as such can be true or false. (It is, in fact, true.)
The question of physics is whether the statement that quantum mechanics applies to both observer and observed is true. Nobody knows the answer to that. However the path that science has taken for centuries says that we should make that assumption as long as quantum mechanics remains our best theory, and we come up with no evidence against it applying to observers, and then find every way that we can to test it.
I think you need to address the topic, not the participants.
> If you seek positive proof of everything, then you can never generalize from experience at all.
No, you can generalize theories that have been supported by reliable evidence. You know, like in science?
> Sorry, but you fail at basic logic.
Are you now going to try to argue that scientific theories eventually become true? Are you aware of the history behind that falsehood?
> It is absolutely valid in science to ask, "What is the consequence if this theory applied to that system."
Yes, and that remark has no bearing on the present topic or conversation.
> ... even though it means accepting things we cannot test at the moment.
Not in science. This is science 101, and you need to learn it. Scientific theories must be vetted by empirical evidence. If this isn't possible, the ideas under discussion are hypotheses, not theories. Here's why:
The bottom line for scientific theories is falsifiability. This is non-negotiable.
Quote: "The strength of a scientific theory is related to the diversity of phenomena it can explain, which is measured by its ability to make falsifiable predictions with respect to those phenomena."
What is a "falsifiable prediction"? In order for a prediction to be falsifiable, it must be open to a practical, empirical test, a comparison with reality. No test, no science.
Many other ideas are interesting, some of them may eventually rise to the level of science, but until they can be tested and potentially falsified, they are not science.
A tempest in a teapot? Before you decide, try keeping religious fundamentalists from teaching Creationism in public school classrooms. They want exactly what you want -- a more relaxed idea of what constitutes science.
> However the path that science has taken for centuries says that we should make that assumption ...
Science makes no assumptions, it performs experiments. If no experiments or repeatable, objective observations are possible, it's not science, it's philosophy.
Why do you think it took so long for quantum theory to be accepted? How did Einstein justify arguing against it for so many years? The answer is that, in the early days, there were too few ways to test the theory. That's all changed, and the only reason quantum theory is a theory are the great number of empirical tests that have been made, and repeated.
Feel free to speculate about multiple universes and the many-worlds hypothesis, but without evidence, don't expect to be able to bully people into accepting it as science. And guess who will be least flexible on this issue? People called scientists.
You have, multiple times now, refused to notice that a statement of the form "If A, then B" is one that can be absolutely established to be true, outside of experiment. And that my initial statement about why intelligent people can find the Everett Interpretation compelling was based on a statement of this exact form.
You are also extremely free to with claims about what actual scientists think and believe. Claims that are completely at odds with my actual experiences with actual scientists. But for something better than anecdote, go to http://www.physics.wustl.edu/alford/many_worlds_FAQ.html and look at the first question, You'll find that among physicists who work in areas that would lead them to think about it, the Everett Interpretation is accepted by more than half. (That poll was taken a while ago, based on anecdote I would put support higher now.) Why? Because if you assume that quantum mechanics describes the observer as well as the observed, the Everett interpretation is the only possible mathematical conclusion that you can come to.
Therefore either Everett is true, or quantum mechanics is insufficient to describe the macro events involved in observation.
Next, you're obviously fond of Karl Popper's falsifiability criterion. While showing blithe unawareness of how poor a description it is of actual science through the ages. I highly recommend that you read Paul Feyerabend's, Against Reason to open your eyes, and also read Thomas Kuhn's book, The Structure of Scientific Revolutions for a better description.
If you understand the last, then you'll understand that Einstein's rejection of QM (which was much more qualified than most people understand) needs no more explanation than Fred Hoyle's rejection of the Big Bang theory. Which is to say none, it was an entirely expected type of event.
> You have, multiple times now, refused to notice that a statement of the form "If A, then B" is one that can be absolutely established to be true, outside of experiment.
I have done nothing of the kind. "If A then B" is not science, and science -- physics -- is the topic of conversation.
Let's recap, since you can't be stopped from wandering off the topic. You said this:
>> If you assume that the observer is described by quantum mechanics, then the Everett Interpretation is logically required to be true.
To the above pseudoscientific claim, I replied, saying:
> Arthur Conan Doyle notwithstanding, in science the truth is not arrived at by eliminating the alternatives. Science requires positive evidence -- absence of contrary evidence doesn't support a given outlook. Were this not true, Bigfoot and the Loch Ness monster would win acceptance through lack of contrary evidence.
Now if you want to discuss this issue, then stop wandering away from the topic into pointless philosophical tangents. Mathematics is not science, only science is science.
> Next, you're obviously fond of Karl Popper's falsifiability criterion.
Karl Popper didn't invent fasifiability, he discovered it. Science is not defined by Popper, it is defined by falsifiability. Falsifiability is science 101, and it's not a debate topic.
> While showing blithe unawareness of how poor a description it is of actual science through the ages.
I'm accustomed to having discussions with people who can't be bothered to examine their own ideas. So, even though you are probably never going to get this, let's perform a thought experiment in which falsifiability is not required for science, see where it takes us (I originally wrote this to counter the myth that psychology is a science):
Let's say I'm a doctor and I've created a revolutionary cure for the common cold. My cure is to shake a dried gourd over the cold sufferer until he gets better. The cure might take a week, but it always works. My method is repeatable and perfectly reliable, and I've published my cure in a refereed scientific journal (there are now any number of phony refereed scientific journals). And, because (in this thought experiment) science can get along without defining theories, I'm under no obligation to try to explain my cure, or consider alternative explanations for my breakthrough — I only have to describe it, just like a psychologist.
Because I've cured the common cold, and because I've met all the requirements that psychology recognizes for science, I deserve a Nobel Prize. Yes or no?
Ask yourself what's wrong with this picture, and notice that the same thing is wrong with psychology — all description, no explanation, no established principles on which different psychologists agree, no effort to build consensus, and no unifying theories.
> If you understand the last, then you'll understand that Einstein's rejection of QM ...
You are, as usual, missing the point that Einstein objected until direct observational evidence became overwhelming in favor of quantum theories. He gave way before falsifiable evidence that, refutable in principle, was not refuted. The reason? Unlike you, he was a scientist, not a philosopher.
> ... needs no more explanation than Fred Hoyle's rejection of the Big Bang theory ...
Guess what happened to Fred Hoyle's rejection of Big Bang theory? It gave way before falsifiable evidence, evidence that remains in principle falsifiable to this day.
The people over at the Discovery Institute (the source for Creationism and "Intelligent Design") will be delighted by your position on pseudoscience -- it's exactly the same as theirs. As far as they are concerned, you can call anything science. If you keep crashing into goal posts like falsifiability on your way to your personal objective, no problem -- move the goal posts.
Quote: "Science must be falsifiable. The scientific method can not be implemented without the theoretical possibilities of both disproof and verification."
Circle the word you didn't understand and raise your hand.
>Because I've cured the common cold, and because I've met all the requirements that psychology recognizes for science, I deserve a Nobel Prize. Yes or no?
I take a different tack on this. The primary failing in the "science" of your thought experiment is that you had no control group to measure the effect of your cure against. If, on the other hand, your cure was statistically-significantly better than control in double-blinded randomized tests, then I think you would deserve the Nobel Prize, even if you couldn't proffer a theory for why it worked. Every theory humans have ever invented had at the bottom level something akin to "Well, those are just the rules and this is the way they work.". Lacking an elaborate, fleshed out framework to understand underlying mechanisms for your cure shouldn't even really be a serious problem, so long as your cure hypothesis is falsifiable.
This conversation is done. Feel free to reply to this in any way you like, I'm not going to bother replying again. I am confident that anyone passing can make their own mind up about our discussion.
For review, here are the basic facts.
You have repeatedly failed to acknowledge that you can get definitive yes/no answers from questions of the type, "What does this theory predict for this situation?" You have repeatedly failed to acknowledge that this type of reasoning is part of the process of doing physics.
You have repeatedly sidetracked to lectures on falsification where you ascribe all sorts of random beliefs to me that I do not, in fact, possess. There is a certain irony to you lecturing on falsification and the behavior of scientists, while refusing the acknowledge that the example of Fred Hoyle never accepting the Big Bang throws a wrench in your description. No, it is worse. You claimed that Fred Hoyle "gave way before falsifiable evidence" when, in fact, few knew that evidence better than he, and he never "gave way". (Instead he continued to adhere to steady state models which had tunable parameters that could continue to explain the evidence. A good Popperian would say that such tunable models cannot be part of science. At which point any historian of science should give a big belly laugh because they are.)
Now you say that, I'm accustomed to having discussions with people who can't be bothered to examine their own ideas. Is that because they can't be bothered to examine their own ideas, or because you fail to recognize that they have?
I will leave you with some interesting examples to ponder.
See http://en.wikipedia.org/wiki/Pioneer_anomaly for a well-known experiment which appeared to falsify basic theories of physics for over a decade before the source of experimental error was definitively tracked down. When experiments can be reconciled indefinitely with theory by assuming experimental error, what experiment can conclusively falsify theory?
Does this actually happen? I give you the example of Barbara McClintock. From the 1930s until the 1970s she carried on a line of research that falsified the developing genetic theory. As a result she was marginalized and her work generally ignored until, as a result of other developments, it became apparent in the 1970s that she was right. Then she was awarded the Nobel in Medicine for some of her discoveries from the 1950s. (See http://www.nobelprize.org/nobel_prizes/medicine/laureates/19... for the press release. The final paragraph is an acknowledgement of her situation.)
If scientists actually worked through falsification, then they should have been all over her reproducible experiments decades earlier. That they didn't, stands as falsification of the theory that scientists proceed through falsification!
But anyways, we're done. Hopefully at some point you reconsider your overly simplistic view of actual science. But I have reached my tolerance for continuing this discussion.
When a construction crane falls and kills a worker, superstitious and uneducated people are known to say, "It was the will of God and his time to die."
When a laser pointer misfires and blinds an audience member at a presentation, Everett Branchers are known to say, "It was the Everett Branch we wound up in." ;-)
Since both of them attribute actual events to an extraphysical process that somehow chooses between alternative histories without any causal arrow running from the past to the future of the resulting coherent reality, I would call them equivalently good explanations, ie: very bad ones.
Well usually in macro-scale events there's enough normal, real causal flow to establish actual reasons something happened rather than "because of Everett Branching."
The problem being that if you accept the Everett Interpretation, then yes it really did happen that way.
There is no problem. If you accept the Everett Interpretation, it really did happen that way, but the odds of you experiencing that are so miniscule that we can ignore it.
If you accept QM with any other interpretation, it really could happen that way, but the odds of it turning out that ways are so miniscule that we can ignore it.
Yes, there is a difference in principle. But in practical effect they are the same - astonishing events are both possible and so overwhelmingly unlikely that we can usually discount the possibility for all practical purposes.
Just because a theory is unfalsifiable does not mean that it's not true. It just means that science and logic are insufficient to refute or confirm the theory. Where science and logic are not capable of shining a light on reality, we can only rely on non-logical and non-scientific beliefs and philosophy.
For example, scientists tend to hold the belief that the laws of the physical universe are constant. But in fact, there is no __logical__ reason to believe that. It is merely an inductive belief that could be violated tomorrow. The theory of constance transcends scientific experimentation and logical proof; it is simply held as an axiom (which could plausibly be wrong).
Beyond logic and science, the multiverse theory is just as plausible as the universe theory. Your intuition tells you that simplicity implies a universe, where others see that simplicity implies a multiverse, where still others find no reason to believe that reality is rooted in simplicity at all.
Quantum mechanics with the "many worlds" interpretation explains lots of things: it explains all the same things as quantum mechanics with some other interpretation. But QM (many worlds) has all the same observable consequences as, say, QM (Copenhagen), so "many worlds" as opposed to Copenhagen doesn't explain anything[1].
But how does that mean that intelligent people shouldn't take the "many worlds" interpretation seriously?
Consider two "interpretations" of Newtonian mechanics. One says that the world mechanically obeys Newton's laws. Another says that the world is controlled by incorporeal angels who are very fond of Newton's laws and always freely choose to push the universe around in such a way that those laws are obeyed. These two interpretations have the same observable consequences (namely, a universe in which Newton's laws always hold), but that doesn't make it surprising if intelligent people take the "mechanical" version of it seriously.
Nor, actually, does it make it surprising if intelligent people take the "angels" version seriously. What (at least for me) makes that option hard to take seriously is its gratuitous complexity: it has the same observable consequences as the "mechanical" system but, at least in my view, is vastly more complicated -- if you wanted to describe such a universe completely you'd need to do all the same work as for the "mechanical" version and then go on to set down everything about the angels' nature, personalities, etc.
In much the same way, you might choose to prefer "many worlds" or Copenhagen or some other specific interpretation of QM on the grounds of simplicity. "Many worlds is simplest because it avoids notions of 'measurement' and 'collapse' that do no real work, and just says that everything obeys Schroedinger's equation all the time." Or: "Many worlds is horribly complex because it involves all those extra worlds we never observe."
So if you mean: "The many-worlds interpretation of QM explains nothing more than any other interpretation of QM does, and therefore it's surprising that intelligent people take the many-worlds interpretation seriously", I think that's wrong. But perhaps what you're surprised that people take seriously is some other thing like, e.g., some particular application of the anthropic principle that appeals to "many worlds"?
[1] Actually, that's maybe slightly debatable; it depends on fine details of what you understand by "explain". For instance: any theorem in pure mathematics is logically necessary[2] and therefore has no observable consequences that you couldn't derive without it -- but it still seems reasonable to say, e.g., that a proof that even-length palindromes have to be multiples of 11 "explains" why I've never seen a palindromic prime number with 4, 6, 8, ... digits. So the fact that QM (many worlds) has no extra observable consequences beyond "uninterpreted" QM might not be enough to guarantee that it doesn't explain anything.
While there are Occam's razor and complexity arguments concerning the relative merits of the Many Worlds Interpretation and the Copenhagen Interpretation, I think this is at best a weak argument. Because, who knows? We could actually be living in a world with very complicated physics.
However, there's a different flaw that I believe completely torpedoes the Copenhagen Interpretation: the Copenhagen Interpretation is not a fully specified theory because it never actually gets around to defining when a measurement is performed. What algorithm can an experimenter run to tell when a measurement takes place? There is none. When a system is considered to be "measured" is always determined with the help of human judgement ex post facto, and alway in such a way as to fit the experimental outcome. If proponents of the Copenhagen Interpretation ever proffered such algorithm to determine when a measurement takes place, then at least we'd have something testable, even if the test were outlandish. But as it is now, the lack of such concrete specification makes the Copenhagen Interpretation unfalsifiable with respect to the Many Worlds interpretation.
Besides that, there are a couple other weaker reasons to be very suspicious of the Copenhagen Interpretation. It doesn't seem to address in any way the fact that experimenters and detectors are a part of physics themselves. If you believe that consciousness arises from physical processes happening inside of the universe, it's very hard to imagine how the Copenhagen Interpretation would compute and explain (even in theory) the physics of what's happening inside of the brain. [1] And if waveform collapse actually occurred, it would be the only known law of physics that's non-local, inherently random, has a preferred reference frame (breaking relativity), destroys information, and violates CPT symmetry. This rule is not like the other rules.
[1] - There actually is a serious school of thought that conscious beings brings the universe into existence, rather than the other way around. I don't know of any experimental evidence for or against this theory, but I'm personally not a big fan of it because the Kolmogorov complexity required to fully specify the theory is fantastically large, because it would need to fully specify how consciousness operates. Without a corresponding amount of evidence in its favor, there's no reason to elevate this hypothesis among all the others with the same or less complexity.
> While there are Occam's razor and complexity arguments concerning the relative merits of the Many Worlds Interpretation and the Copenhagen Interpretation.
Exactly, we don't know anything, but Occam's razor is all we have, and I believe many smart people take many-worlds seriously because it is simpler.
the simplest is statistical aggregate interpretation.
An interpretation of QM experiments depends on your interpretation of QM :) When one sees the world through Copenhagen interpretation (i.e. superposition of states, simultaneously dead/alive cat) one sees miracles like entanglement, and starts wondering about many worlds, etc... On the other side one can look at Hitachi's electron double-slit experiment :
It doesn't refute superposition, it just allows to interpret/explain things without it. Of course with superposition gone, quantum computers are gone, and no miracles like entanglement, and many worlds while still may exist lose a potent argument in their favor :)
(note: the experiment clearly shows 2 separate things:
1. the main point of QM that, for example, position of a particle is described by wave-function/quantized
2. superposition of many positions is visible as a characteristic of the whole set of particles
Bringing in additional superposition at the level of one particle doesn't add anything for explanation, it only brings "miracles" that Copenhagen interpretation is filled with )
While, you're right, it is minimalistic, Einstein's Statistical Ensemble Interpretation is an incomplete theory. It doesn't tell you which possible future you'll end up in. And if you try to patch the theory by saying there's some deeper element of reality that we just haven't found yet that's deciding the outcome of experiments, then the violation of the Bell Inequalities renders that whole line of thinking moot. If, instead, you try to patch it the other way and say that everything in the ensemble is real, then you've just reinvented Many Worlds by a different name.
I'm unclear why you're bringing up Hitach's experiment and what you think it shows. Maybe you could elaborate? My understanding is that the raison d'être of the experiment is to show that multiple particles are not necessary for quantum interference to occur, and that a single particle is perfectly capable of destructively interfering with itself. This is pretty direct evidence for superposition, because you're getting measurable effects from the superposition. And if anything, it's evidence against the Ensemble Interpretation.
Also, quantum computers are real and here today. Any successful theory of physics must explain how 15 was factored using Shor's Algorithm. (http://arxiv.org/abs/quant-ph/0112176)
>Einstein's Statistical Ensemble Interpretation is an incomplete theory. It doesn't tell you which possible future you'll end up in.
not sure that we're talking about the same. My understanding here is that one calculates probabilities the same way. It is the interpretation different. In Copenhagen the particle is supposed to carry all probabilities which magically "collapse" on the measurement, while in statistical a given particle is in "collapsed" state to start with (there is a distribution of the states over the ensemble), and the probabilistic model describes the evolution of these states and distribution of final states - there is no collapse on measurement, we just measure specific state.
>I'm unclear why you're bringing up Hitach's experiment and what you think it shows. Maybe you could elaborate? My understanding is that the raison d'être of the experiment is to show that multiple particles are not necessary for quantum interference to occur, and that a single particle is perfectly capable of destructively interfering with itself.
in Hitachi experiment it is shown explicitly clear that quantum interference is emerging only for multiple particles. It is basically a visualization of underlying probability distribution, like it happens in any statistical experiment when enough samples are taken. During the Hitachi experiment nothing happened that looks like or requires an explanation by a single particle supposedly interferencing with itself.
If you don't see this in Hitachi experiment, lets run the following experiment. Imagine 2 doors in a wall, and imagine another, parallel, wall at several meters distance from the doors. Imagine that frogs jump out, one at a time, from either door pretty randomly. The frogs jump in general direction of the wall opposite the doors. The precise direction of each frog is varying a bit. It takes a frog several jumps to reach the wall. The probability density of the places where the frog's legs touch the ground is square of cos(pi*x/A) (correctly scaled to be a probability density) where x is the distance from the door the frog jumped out, and A is the avg. frog jump length. A frog only exist (i.e. can interact with anything else) when it touches the ground, and doesn't exist when it is flying during the jump. Whenever a frog lands near the wall, say not farther than a body distance from the wall, it touches the wall and leaves a wet spot.
It is easy to see that after a big enough bunch of frogs, there would be an "interference pattern" of dry and really wet areas on the wall - i.e. some places have low probability of a frog landing near it while some have high, and that probability distribution looks like an "interference pattern". No superposition, no destructive interference of a frog with itself is necessary to observe the effect. This is what Hitachi experiment shows.
>This is pretty direct evidence for superposition,
yes, an interference of a particle with itself would be such evidence. I'm yet to learn about an experiment which can only be explained by such interference.
> Any successful theory of physics must explain how 15 was factored using Shor's Algorithm.
agree. While 15 seems too small a number to exclusively lock a superposition explanation, i don't have another ready. I'd like to have quantum computers and other quantum miracles too :) I just want them to be a bona fide miracles, not figments of our interpretation :)
The way you're describing the theory sure seems like the Ensemble Interpretation to me, but to be honest, I have never heard of the "Statistical Aggregate Interpretation". Just to be sure I know what we're discussing, could you provide a reference to the Statistical Aggregate Interpretation? What you're suggesting -- that the information is there, but we just don't know which one -- sounds a lot like a hidden variables theory. Unfortunately, all theories with local realism (which includes hidden variables theories) are ruled out experimentally by Bell's theorem. [1]
I like your classical frog example because it's a thought experiment that illustrates how classical particles behave, and we can compare the distribution of the classical frogs to the distribution of whatever we're measuring (like electrons), and if the distributions we get are different, then we'll learn that whatever we're measuring is behaving non-classically. However, the probability density you gave for the frogs in the classical case, cos^2(pi*X/A), is incorrect. The probability distribution for the classical case the way you set it up will, in fact, be almost Gaussian (but not precisely for reasons that aren't relevant or worth discussing here)[2]. The combined probability distributions for frogs coming from the two doors will be the sum of two individual Gaussians, so it will be a "two-humped" distribution. As a point of fact, if you run your frog experiment, there will be two wet spots. It will not look like an interference pattern precisely because there is no superposition and no destructive interference. The fact that electrons in Hitachi's experiment display a "many-humped" distribution is good evidence that the electrons are not following the same rules as the frogs, and hence that the electrons are behaving non-classically.
> in Hitachi experiment it is shown explicitly clear that quantum interference is emerging only for multiple particles.
This is the exact opposite of what the Hitachi experiment shows. The experiment is interesting and surprising precisely because particles are sent one at a time but still show an interference pattern. The experiment shows a single particle interfering with itself.
>The way you're describing the theory sure seems like the Ensemble Interpretation to me, but to be honest, I have never heard of the "Statistical Aggregate Interpretation".
yes, my mistype, it is basically Ensemble Interpretation.
> However, the probability density you gave for the frogs in the classical case, cos^2(pi*X/A), is incorrect.
it isn't resulting probability distribution on the wall. It is probability distribution of the frog legs touching the ground on a radial line from door to the wall, i.e. peaks at 0, A, 2A, 3A,.... It is about the same as position operator for electron would produce on a radial line from slit to the screen.
Also note that the frog doesn't interact with the wall if the frog is "airborne" (i.e. one can imagine that it just goes through the wall without leaving a wet spot or even better - the wall is too low, say 0.1m , so airborne, mid-flight, frogs would fly over it).
the red concentric lines is where a frog most probably touches the ground and the greenish-yellow - where a frog is most probably mid-jump airborne (flying at the height enough to fly over the wall). Where 2 yellow-greenish lines intersect right near the wall - it is the place with minimal probability of a frog landing near the wall, ie. dry place. While intersection of 2 reds - correspondingly a very wet place.
>The fact that electrons in Hitachi's experiment display a "many-humped" distribution is good evidence that the electrons are not following the same rules as the frogs, and hence that the electrons are behaving non-classically.
this non-classical behavior is the quantization of position, ie. position probability density looks like concentric waves starting at a slit. I.e. cut along the radial line, the profile of that density is a correctly scaled cos(x), with x - distance from the slit. The superposition isn't necessary for the observed effect.
>> in Hitachi experiment it is shown explicitly clear that quantum interference is emerging only for multiple particles.
>This is the exact opposite of what the Hitachi experiment shows. The experiment is interesting and surprising precisely because particles are sent one at a time but still show an interference pattern. The experiment shows a single particle interfering with itself.
i'm trying to understand where do you see the interference of a particle with itself. Lets say the experiment was run only until there is only 1 (i.e. 2 sec into the clip), or say 3 particles hit the screen (4 seconds into the clip). What would be an indication of the interference in such a case?
Ah, I see. Yes, I did misunderstand the mechanics of your frog thought experiment. However the math for the classical case still doesn't work out the way you need it to. Setting up the mechanics the way you did, you will not get the probability distribution you mentioned on the frog's radial distance from the wall. Nor will you get many alternating wet and dry spots on the wall, even allowing for frogs to jump through the wall. I encourage you to try the math yourself or to set up a Monte-Carlo simulation to estimate the classical consequences of your jumping rules.
If you're not convinced yet, consider the following:
What happens if Hitachi's experimental setup had only one path for the electron to follow rather than two? You're claiming that the frogs are a good model for Hitachi's setup, so it should be the same result that you claim for the frog model with one door. You're claiming that the frog model with one door produces a pattern of alternating wet and dry. What happens in the lab when you try it with electrons? Electrons following a single path don't produce an alternating pattern; they produce a pattern very close to a Gaussian.
Moreover, here's the really wild part of the experiment. If you let electrons go through either just one path or just the other path, you'll get nice smooth Gaussians from both (translated a bit from each other). But open both paths up, you'll see the distribution dim at places. That's very unexpected! Somehow letting more electrons through has decreased the electrons hitting certain parts of the screen. And if you carefully observe your experiment, you'll see that some other areas of the wall more than double in intensity when you open up both paths. It's pretty clear that you'll never be able to invent mechanical rules for classical frogs that can mirror these experimental results.
> i'm trying to understand where do you see the interference of a particle with itself.
This is a slightly subtly distinction, and it's easy to miss what's going on. You "see" the effect of a particle destructively interfering with itself when there's only a single electron on the screen. You "see" the effect in the probability distribution for where that electron appears, but you can't say with high confidence that this is a real effect until you've seen a statistically significant number of particles. But the effect had to have been there the whole time because destructive interference happens independently and individually on each electron. If you still think there's some effect being transmitted between different electrons, then realize that the fact that all the electrons are showing up on the same screen is just a convenience for the experimenter. You would get exactly the same effects by setting up a statistically significant number of screens all spatially separated from each other and running the experiments without signals being able to be communicated between screens and then overlaying the resultant observed positions.
However, the Mach–Zehnder Interferometer is, I believe, an better physical model to witness a single photon interfering with itself. Young's double-slit experiment was invented first, so for really that reason alone, it's taught first, but because of its continuous nature, it's easier to get bogged down in certain irrelevancies. The Mach–Zehnder Interferometer is really much more plainly impossible in a classical universe, or an ensemble interpretation universe for that matter.
> Nor will you get many alternating wet and dry spots on the wall, even allowing for frogs to jump through the wall.
...
>What happens if Hitachi's experimental setup had only one path for the electron to follow rather than two? You're claiming that the frogs are a good model for Hitachi's setup, so it should be the same result that you claim for the frog model with one door. You're claiming that the frog model with one door produces a pattern of alternating wet and dry. What happens in the lab when you try it with electrons? Electrons following a single path don't produce an alternating pattern; they produce a pattern very close to a Gaussian.
The electrons, photons, and frogs (jumping over the wall when probability below some threshold) would produce an alternating pattern like this one:
Because it is result of the same geometry as on the image that i posted before : where 2 greens touch the wall simultaneously - deep trough, zero intensity, and where 2 reds - peak. The meaning of the green/red isn't important - be it probability of a frog's legs touching ground or the probability density of position of electron - the resulting pattern is the same. The image can be interpreted as either while it is just an image of concentric circles originating from 2 points. Gaussian outline comes to play only because it describes the normal deviation of a frog/electron from the preferred direction they jump/fired along.
> If you let electrons go through either just one path or just the other path, you'll get nice smooth Gaussians from both (translated a bit from each other).
this is true only in classical mechanics where position of electron or a bullet isn't quantized - you'll get a smooth Gaussian. In QM, i.e. real electrons, photons (or jumping frogs having the property of going through/over the wall where ground touch probability is close to 0) single slit produces dim/light pattern like on the image above. Like the double-slit pattern, this single-slit pattern is also result of position quantization.
> But open both paths up, you'll see the distribution dim at places. That's very unexpected! Somehow letting more electrons through has decreased the electrons hitting certain parts of the screen.
This - double slit is more frequent than single-slit or dimming at some places - happens only for stream of photons as photons interfere with one another and the photon's wavelength is the same as its position quantization period (note - for electron DeBroglie and positional quantization are different wavelengths), so the photon_A-photon_B interference is visible on the scale of the pattern produced as a result of positional quantization. In case of Hitachi, we have single electrons, so no electron_A-to-electron_B interference, so the double-slit pattern is less frequent than single-slit, ie. where was light on single slit - there will continue to be the same or brighter light on double-slit, it is just some (not all) troughs/dims will disappear.
> You "see" the effect in the probability distribution for where that electron appears
The quantized position probability distribution already explains the pattern. I don't see how adding the interference or superposition changes it.
>If you still think there's some effect being transmitted between different electrons
no, the many particles, i.e. many samples is just results in better visualization of underlying probability distribution. I think here we agree.
> You would get exactly the same effects by setting up a statistically significant number of screens all spatially separated from each other and running the experiments without signals being able to be communicated between screens and then overlaying the resultant observed positions.
the same here. We agree about independent events and their cumulative statistics. Let frogs jump in separate setups, and mark their results on a separate screen - the pattern will emerge as if they all jumped in the same yard.
>However, the Mach–Zehnder Interferometer is, I believe, an better physical model to witness a single photon interfering with itself.
Will definitely spend a time on it.
> Young's double-slit experiment was invented first, so for really that reason alone, it's taught first, but because of its continuous nature, it's easier to get bogged down in certain irrelevancies.
it only looks somewhat "continuous" with light. That is the beauty of the Hitachi experiment as it took away a lot of "continuity" effect as well as "photon A interfering with photon B" effect.
We can also ponder about the true existence of reality. Do we really exist, or are well all non real and in someone or somebody's head. Neither of which will ever be provable, but we obviously default to "yes we do exist" because it's simpler.
Many Worlds is falsifiable. It's making testable claims about how amplitude flows between configurations and recombines constructively and destructively. If we ever find an experiment in which amplitude is flowing by some rule other than Schrödinger's equation, we'll have falsified Many Worlds, and we can throw out the theory. Not all consequences of the theory are testable, but that's true of a lot of theories.
[1] - There actually is a serious school of thought that conscious beings brings the universe into existence, rather than the other way around. I don't know of any experimental evidence for or against this theory, but I'm personally not a big fan of it because the Kolmogorov complexity required to fully specify the theory is fantastically large, because it would need to fully specify how consciousness operates. Without a corresponding amount of evidence in its favor, there's no reason to elevate this hypothesis among all the others with the same or less complexity.
That actually depends on what consciousness is. You might not necessarily need a fully operating human or humanoid brain to be conscious enough for a "psychic universe" to care.
So if you mean: "The many-worlds interpretation of QM explains nothing more than any other interpretation of QM does, and therefore it's surprising that intelligent people take the many-worlds interpretation seriously", I think that's wrong. But perhaps what you're surprised that people take seriously is some other thing like, e.g., some particular application of the anthropic principle that appeals to "many worlds"?
Both of these, actually.
I see no reason that reality has to be neatly explainable to our tiny little human minds. Why should I consider unfalsifiable metaphysics to be in the domain of science at all, rather than the domain of religious speculation?
[1] Actually, that's maybe slightly debatable; it depends on fine details of what you understand by "explain". For instance: any theorem in pure mathematics is logically necessary[2] and therefore has no observable consequences that you couldn't derive without it -- but it still seems reasonable to say, e.g., that a proof that even-length palindromes have to be multiples of 11 "explains" why I've never seen a palindromic prime number with 4, 6, 8, ... digits. So the fact that QM (many worlds) has no extra observable consequences beyond "uninterpreted" QM might not be enough to guarantee that it doesn't explain anything.
That's the issue of falsifiability. That theorem falsifies all predictions of a palindromic prime number with 2*n for n > 1 digits.
Why should I consider unfalsifiable metaphysics to be in the domain of science at all, rather than the domain of religious speculation?
Today's 'unfalsifiable metaphysics' is tomorrow's Physics.
Neil deGrass Tyson makes a compelling point[0] that:
"But a careful reading of older texts, particularly those concerned with the universe itself, shows that the authors invoke divinity only when they reach the boundaries of their understanding. They appeal to a higher power only when staring into the ocean of their own ignorance".
He then goes on to show examples where Greats such as Newton proclaim some aspect of their work as only knowable by God, but then those same issues are tackled later by people who are unsatisfied by God as an explanation.
>I see no reason that reality has to be neatly explainable to our tiny little human minds.
It doesn't. But using the best approximations that our human minds have come up with has produced good results so far, I don't see a reason to give up and say that we will never understand it.
Regarding the many worlds interpretation. For me, it arose naturally out of the equations we use to describe quantum mechanics (actually quantum computers, but the physics is the same). Assume that a particle is in an even superposition of 2 states. This can be represented by: (|a> + |b>)/sqrt(2), meaning that their is a 50% chance of observing a, and a 50% chance of observing b. When it interacts with another particle, they are said to become entangled. Assume the interaction is such that both particles would be in the same state. The state of the two particle system is now (|aa> + |bb>)/sqrt(2).
Note that the state of the second particle is a superposition of the two states. However, consider this from the perspective of the first particle, when it is in the 'a' state. The second particle is in the 'a' state as well. Similarly, when the first particle is in the 'b' state, the second is as well. However, neither particle can observe that the other one (or itself) is in a superposition. As these particles continue to interact, more particles become entangled. Eventually the researcher and equipment become entangled as well. At this point, the equipment can no longer detect that the particles are in a superposition anymore. However, from the perspective of a particle not entangled, it is clear that their is a superposition.
The many worlds interpenetration comes from the fact that when you use this model to describe the interaction of all of the particles, the superposition never dissapears. Rather, you are left with a superposition of many different states of the world (Universe), which, if measured, would randomly collapse to one of them (or entangle observer).
You seem to be suggesting that you have to pick some interpretation. Am I misreading? Why do you have to take any interpretation seriously if it does not imply any observable consequences?
Even if multiverse exists, I doubt it would ever influence your day-to-day life, much less history.
It's too low level. It's all about quantum states, and we're like ten levels above them.
Low level processes tend to either go unnoticed by high level ones (think radio waves) or be harmful to them (think radiation) by messing with their high-level organization.
So please forget about hiding a knife in a parallel universe.
You do realise that this high-level / low-level distinction is all in our minds, right? It's just an intellectual tool we use to understand nature. If Quantum Mechanics is correct, _everything_ is made of quantum states, not just radio waves and radiation. Also, Chaos Theory.
True, but under our current understanding of QM, it is literally impossible for you to interact with parallel worlds. Someone 'outside' the universe may observe[0] that we are in a superposition, but it is theoraticly impossible for our state to be influenced by any of the other states.
Correct. It's only things that are random at a quantum level that might have multiverses.
Most [probably all actually] actions people take are not random at a quantum level.
In fact it's quite hard for something random at that level to have any noticeable [to a human] effect at all. So basically all the multiverses are identical.
> In fact it's quite hard for something random at that level to have any noticeable [to a human] effect at all. So basically all the multiverses are identical.
If and what particular type of tissue damage and/or cancer(s) is caused in someone by exposure to radiation damaging their cells in repairable or unrepairable ways (which depends on the particular times at which particular radioactive atoms decay and the paths of the resulting particles and their interactions with with the small-scale constituents of the person's biology). I would think that whether a person recovers from some radiation exposure or the exposure went just beyond what their cells could handle and thus causes a fatal cancer, that is noticeable to a human. Finding that wasn't altogether hard.
Given a sufficiently long time horizon (some physicists at UC Davies got some press arguing it could be on the scale of months), future weather conditions at individual moments are currently in the realm of quantum uncertainty/randomness. The people who have/don't-have car accidents due to the rain&sleet or not on some winter day a few years hence will easily notice which of the multiple worlds they ended up in.
Also, should anyone so choose, they could easily make world-history-scale decisions based on Geiger counter readings or some other implementation of a quantum-coin-flip. Imagine an assassin setup and ready to take out a large nation's leader(s), and taking the shot or not based on such a random quantum outcome. Scale is no barrier to such things.
http://www.galactanet.com/oneoff/theegg.html