/sci/ - Science & Math

>How does the fucking wavefucktion know it's fucking being observed by some fucking observer?
The act of observing changes it. Think about how you view something. Light must bounce off the object into your eyes. For every day items, photon energy makes a negligible impact on object motion. But for very small things, photon energy becomes significant and alters the motion.

Because to observe something, you have to interact with it. It doesn't "know" anything. The observer is anything that interacts with...anything.

Observing means bouncing a fucking photon off of it.

>>2485596
Don't beat yourself up, even Einstein struggled

>Check air pressure in tires
>You let some air out as you put the gauge in
>Congratulations, you have changed the the air pressure by measuring/observing it

>>2485596
Simple, in order to observe something on the quantum scale one must fire photons at it so that there are photons reflected to detect. The photons affect the experiment.

http://en.wikipedia.org/wiki/Quantum_mind%E2%80%93body_problem#.22Consciousness_causes_collapse.22

How come serious physicists come up with something this level insane?

>>2485632

Don't know. Why physicists have to go and complicate things, when QM and QFT is hard enough to study.
Now that I think about it, it's more likely that philosophers have taken the discoveries of quantum superposition and wavefunction collapse, etc, as a sign that consciousness plays a part in the external world.

Relevant to my interests. Proceed.

>>2485630
>>2485612
>>2485607

So if you put a device which fires photons at the particles and DONT use it to detect the particle, the wavefunction collapses? Or am I the first one to think about this GODDAMN SIMPLE experiment?

>>2485620
requires physical interaction with the thing being measured. While that method of observation would change the medium, if let's say you have a digital tire pressure gauge built into the tire that reports to a display on the dash by rf, then the act of looking at the display on the dash won't change the amount of air in the tire.

So if you don't observe, it isn't there? So if you close your eyes, close your ears, and close your skin (that way you don't observe anything, duh) things don't exsist anymore?

>>2485678
That is just stupid. If you aren't there to observe something, then it might as well not be there, BUT you are not the only thing in the universe. Plenty of observers to go around (living or not).

>>2485678
Does existence disappear when you go to sleep?

You just can't tell what they're doing, that's all.

This is like general relativity, the twin that accelerates ages slower because acceleration causes time dilation as well as velocity, there's no way to elaborate on this further without getting your equations on, if you want the technical details do the math.

Schrödinger's cat though experiment is just a though experiment so we can visualize how different interpretations of QM work.

As long as there`s no interaction with a particle that never did interact with an intellegent observer, the cat would technically still be in a closed system.

Although a lot of interactions take place, The cat would still be in superposition as long as it`s not obseved (by an intelligen being) AND doesn`t interact with a particle that deterministicly traces back to an intelligent observer.

Note the last requirement is impossible to accomplish in practice, but not in theorie. That`s where a lot of people here go wrong.

>>2485674
The digital pressure gauge is doing the observation, not you. Since it is placed in the tire, it does affect the air pressure. If it magically disappeared, the pressure in the tire would change. You looking at a display does not mean you are the observer.

>>2485686
Or, you could just say that you aren't observing the tire pressure. You are observing the tire pressure measuring thingy.

>>2485684
Fuck off tautologic. No one likes you and your stupid shit. Oprotten tering kneus.

>>2485686
>The digital pressure gauge is doing the observation, not you
Get this guy a nobel prize...

His knowledge is way past all other sceintific knowledge.

>>2485684
I can't tell how many times I've seen this picture of this female Ronald McDonald together with that same text every single time quantum mechanics comes up on this board.

Every. Single. Time.

>>2485692
>He still thinks the observer has to be a conscious being

>>2485684
That's not very helpful. Let me ask this simply. Do quantum mechanics imply that the human mind has an effect on physical reality even in cases where there is no physical interaction? Ei a special lens is set up that would allow a human eye to perceive a quantum wave, while diverting all reflections off at a 45 degree angel so nothing of the preceptor reaches the target it is observing, would the wave still collapse?

>>2485699
Yes, the collapse of particles in it`s wave form is ultimately caused by an intelligent observer.

The idea a wave pattern is collapsed by a so called scientific "observalbe"(which could be any material) is a common misconception.

>>2485703
This is what quantum theorists actually believe

>>2485703
I fucking knew it. Get the fuck off this board. Why even go here? It's obvious you know shit about QM or any other field of science for that matter. All you do is post shit threads and comments.

>>2485703
I'm wondering if people actually find doing this funny.
This is why we can't have nice things!

>>2485684
Everyone but this guy ITT is a fucking retard.

Everything is wave functions. If the wave function interacts with something, then it interacts with another wave function. A wave function interacts with another wave function by interfering and combining. Everything should be describable by a complex superposition of wave functions, including the instruments we use in observations. However, by the time it comes to our consciousness, we only observe it as a single value, the likelihood of which is determined by the magnitude of that superposition of wave functions. So somewhere for it got to our consciousness, it had to "collapse".

Either that, or you follow the many worlds or many minds interpretation, and we have infinite consciousnesses, and each one observes a different value according to the probability distribution, and there never is a collapse.

The lens doesn't have to be a real thing, consider it like maxwell's demon.

>>2485702

Prove this, and you prove that consciousness is something separate from the network of neurons in our brains.

>>2485670
>So if you put a device which fires photons at the particles and DONT use it to detect the particle, the wavefunction collapses?
Yes. Don't think of an observer as a person, it's just anything interacting with the item of interest.

<span class="math">\underline{\bf I~THINK~IT~IS~CLEAR~THIS~THREAD~TURNED~INTO~A~TROLL~TREAD.}[/spoiler]

<span class="math">\underline{\bf LETS~NOT~NURSE~IT~ANY~LONGER.}[/spoiler]

>>2485724
Wait? What? When? God damn it I want answers.

>>2485730
The point Tautoulogic entered the thread. Ignore anyone saying intelligence or consciousness has anything to do with the observer effect.

>>2485734
No damn it, that's not an answer either. To say a wave collapses any time it interacts with anything is to say that it is impossible for a wave to exist at all. Except for hypothetical situations nothing exists in a closed system, everything is constantly interacting with everything around it. What specifically causes wave collapse?

Is there an interpretation of QM which is generally accepted to be most likely to be right?

>>2485596

>>2485745
http://en.wikipedia.org/wiki/Wave_function_collapse

>>2485748
no

If you observe the wave indirectly, such as observing the effects of the wave on an object, did the wave function collapse?

>>2485717
>implying any interaction will cause a collapse

>>2485734
Consciousness is the only thing that tells us that a collapse happens. It is very tightly connected with the idea of collapse.

>>2485766
The only way to observe it is indirectly, so yes.

>>2485775
Fuck.
Off.

Sage for quantum mechanics. Take this shit to /x/.

>>2485748
yes, consciousness causes collapse is considered the most likely interpretation of qm and this view is accepted by prominent phiscists all over the world, period

Exept here in /sci/, where you`ll only find the arrogant ones that rule out anything that sounds a bit miraculous.

it`s like saying
"There is no evidence red roses are red, just because we percieve it`s leaves as being in the color red doesn`t mean color`s actually exist."
Pathetic people they are.

>>2485791
No.
U.

>>2485684
Why did I immediately know this poster was the idiot named Tautologic.

>>2485797
No it's not. Many worlds/Many minds is the most popular interpretation by scientists currently.

>>2485748
yes, consciousness causes collapse is considered the most likely interpretation of qm and this view is accepted by prominent quantum physicists all over the world, period

Exept here in /sci/, where you`ll only find the arrogant ones that rule out anything that sounds a bit miraculous.

it`s like saying
"There is no evidence red roses are red, just because we percieve it`s leaves as being in the color red doesn`t mean color`s actually exist."
Pathetic people they are in here.

>>2485801

no, you`re an idiot

>>2485773
>claim that continuousness isn't necessary for observation
>that anything that would reflect back the condition of the wave would count as an observation whether or not a mind would be there to perceive
>every action has an equal and opposite reaction, anything that interacts with the wave could be used to measure the wave by the disturbance caused by the reaction of the two colliding.
>the only difference between an interaction and an observation is whether there is a mind there to measure it.
>claim that continuousness isn't necessary for observation
It's fine. I come from /x/, I'm used to crazy.

>>2485775
backs up the roses part @ >>2485803

>>2485803
I preffer many worlds because it doesn't sound like sorcery. But if "consciousness causes colapse" interpretation is proven to be correct, I will get over it eventually.

I hate this "intelligent observer" shit being brought up everytime. If this shit were true, how the fuck would the universe even exist and function prior to the existence of intelligent beings like humans?

>>2485808
I may or may not be an idiot. However, Many Minds and Many Words account for the quantum interpretations subscribed to by the majority of physicists, my alleged idiocy notwithstanding.

>>2485803

[citation needed]

>>2485835
Maybe something else was fucking with the universe long before we got here.

>>2485835
I don't think anyone suggests you need to be a human, or have intellectual complexity. But if you needed humans -- which no one is saying -- it doesn't pose a problem. The universe would exist as a state of superimposed waves, until the first observation collapsed it into one of its potential states.

>matter acting differently when unobserved

problem, scientists?

>>2485856
So you are saying that the big bang happened the first time a continuousness formed in the fuzzy patterns of superimposed waves?

>>2485856
Observed by what? The needed observer is part of the thing to be observed.

I think it's pretty obvious God was the observer who caused Big Bang.

>>2485919
Oh fuck this shit board.

>>2485909
fuck you guys are so close minded i bet that one chases Zorak back go to /x/ only to never return.

>>2485904
No, the big bang happened, and the universe evolved for 13 billion years, but as superimposed waves, which is the way that subscribers to Many Worlds and Many Minds say it still is. Then when there were observers, it collapsed into particular configurations of those waves.

I'm not saying I believe that's how it happened, but it works.

>>2485909
Maybe; maybe not. All we know is that we can observe, and when we observe things they tend to be in definite configurations, and not all spread out. And we also know that how things interact is all spread out as wave functions. So somewhere between where they interact, and where we observe them, some funky shit has to be going on.

>>2485803
"Consciousness causes collapse" is simply NOT what most physicists believe. And for a simple reason. It answers nothing. All it does is push back the problem a bit farther. What, then, about consciousness causes the wave to collapse? Physicists don't like answers that don't explain anything.

9/10, almost raged.

>>2485596

It doesn't. It just a way of explaining shit.

The system is on such a small scale that photons, and any other outside particles and fields will effect it noticeably.

/sci/ is really depleting in quality debates and conversations. Fucking trolls.

>>2485856
You have it slightly backwards. I'm going to try to explain this as simply as possible.

The laws of quantum physics are entirely deterministic. However, they apply to the Hilbert space, not "our" universe. The Hilbert space contains many different possible universes. The Hilbert space is also practically of infinite dimensions. (You could say it has perhaps 10^79 dimensions, but for our purposes that's infinite.)

You don't observe something and then cause the wave function to collapse. The wave function evolves completely deterministically in Hilbert space, or equivalently over all universes. This assigns different probabilities to different outcomes. An observation correlates the outcome of a certain event with your perception of it; anything else would be physically inconsistent. Just the same way that you could drop a ball and it started going up, which is technically allowed by quantum physics, it doesn't correlate consistently within physics.

The wave function never collapsed. However, you have been projected into a state of the Hilbert space where the observable now has a definite (eigen) value, instead of still being a superposition.

tl;dr Wavefunction doesn't collapse. Wavefunction doesn't exist in space, but in Hilbert space. We exist in space, so we can only observe part of the wavefunction corresponding to our own consistently correlated reality.

>>2486017
First person in the entire thread to make sense. Could you explain Hilbert space in a bit more detail? Does it have physical dimensions or is it sort of a hypothetical space used to determine probability?

>>2486028
hilbert space is a mathematical construct, not even close to "space" most non-mathematicians are used to.
the way i like to see it in, it is a (near-)infinite dimensional space where every position (as in vector from an arbitrarily defined location) represents a wavefunction.

>>2486017
Sure, that's the spin of the many worlds interpretation, where there is no collapse, and you imagine the hilbert space as a real thing as opposed to a mathematical tool that gets you to a statistical prediction.

>>2486028
You are willing to learn, so please take no offense. You can tell those who know quantum physics and who know ABOUT quantum physics by this question. If you've actually studied any quantum physics, you know what the Hilbert space is. So when people spout crap about quantum physics, if you ask them what the Hilbert space is and they can't answer, you can disregard anything they say.

Anyways, the Hilbert space...
I'm a physicist, not a mathematician, so I'll probably get a lot of the details wrong, but I can explain how they apply to quantum mechanics. If you do the Stern-Gerlach experiment (again, something anybody who knows anything about quantum physics will know about) you have a single electron in one of two states: spin up or spin down. The Hilbert space is the range of values the spin can take: |psi> = cos t |up> + sin t * e^(i pi r) |down>
More visually, it's a sphere on which the electron "lives." it has only two eigenstates, up and down, but two continuous and bounded variables r and t. If you have two electrons you have now t1, t2, r1, and r2, which already becomes too much to visualize in 3D space. But mathematically, it's the space of configurations, each one distinct, that the system can take. May have different energies and such, but that's what you worry about when you actually solve the Schrodinger equation.

(there's more)

>>2486053
It gets even more confusing when you can have a range of eigenstates like |x> and |p>. For such particles, each |x> is a DIFFERENT eigenvalue. So you have that many different dimension in Hilbert space. (For reasons I won't go into, we can place a bound on the number of different states, so it's not necessarily infinite, but almost so.) |x=1 m> is different from |x=1.1m> in that they are different axes in a Hilbert space. Most people, EVEN PHYSICISTS, think that these are different values along a single axis. That's not true.

Anywho, go google the Stern Gerlach experiment and go from there. Google Hilbert space, too. You may not learn all that much quantum mechanics, but you'll have an idea of how it works. (Instead of reading stuff on Wikipedia and thinking it's taught you any real quantum mechanics.)

>>2486049
And you would suppose a single 3+1D world is more real.... why?

>>2486049
Yes and no. Many worlds presumes that there are identical copies of the universe split off. I make no such assumption. Generally, people understand many worlds to mean many separate worlds. I would guess that they are still just as connected. We are not contained by being in one world versus another, but by being limited to physically consistent measurements.

>>2486043
>>2486053
>>2486060
Much appreciated. Now because this thread got very metaphysical there is something else I'd like have cleared up if you'll humor me. Quantum physics don't describe the way in which these particles behave, but rather is the model we use to predict how they will behave?

>>2486092
Well, yes. All scientific theories are "just" predictions. But they are also explanations. The thing about quantum mechanics that is hard is that it lives in a world we just don't have any real intuition for. You can't imagine an atom as a nuclear sun with electron planets orbiting it. It just doesn't work. It only works by understanding how these things behave in the world of quantum mechanics: the Hilbert space. But take solice: quantum mechanics is just like Newtonian mechanics in one way: if you know the rules and the boundary conditions, the values of all functions can be calculated (at least in principle) for all times. What's hard is solving the equations and then understanding what they mean for us, in our little three-dimensional slice of all of existence.

>>2486053

>if you ask them what the Hilbert space is and they can't answer, you can disregard anything they say.

Just repeating what prominent sceintists you have trust in(trust based on recognition by other reliable people) doesn`t require any knowledge of the subject. And it`s probebly more accurate then spewing your own thoughs on it after reading one or two books about the subject. That`s what you silly people need to learn.

You are using certain knowledge as a social password here. it`s a sign of elite cultivation.

please, /sci/ is not for agreeing any consensus in the field of qm. and this board is not the "avant garde" of sceince either.

>>2486157

>>2486061
Because in science real=observable.

>>2486060
There's no such thing as "almost infinite". There's unimaginably large, but that is no closer to infinite than unimaginably small.

>>2486119
Do you know of any books, websites, or online lectures that could teach, in a simple yet accurate way, the basic math underpinning QM (i.e., Hilbert spaces, eigenvalues, Hamiltonian)?

I find QM interesting but never studied it in college, and whenever I try to learn more about it I find explanations that are too dumbed down and seem like hand-waving, or too advanced and filled with assumed knowledge of unfamiliar mathematical concepts.

Is there any (relatively) quick and easy way to at least learn the basic concepts? Or is the only option to have taken these courses in college?

>>2486199
Well, in physics, we tend to count this way:

0, 1, 2, nearly infinite, infinite.

>>2486157
I don't care how many tables you've studied and bought. You don't know as much about actually building a table compared to the guy who's actually built a table before. Even if it was a crappy table, he still built something, and knows more than you about the process of actually building a table.

Also, understanding quantum mechanics does not mean trusting what you've read in a few books. You have to actually DO quantum mechanics to understand it correctly and fully. You may be very knowledgeable about what quantum mechanics says or means; that's not the point. The point is that all your knowledge is second-hand. With tables, you may be able to explain the grandiose history of a table and all the ornamentation on it and so forth. But you still wouldn't know anything about how it was actually built.

If you go up to somebody with a PhD in physics and tell them you know more about the subject than they do, and then can't even talk about the most basic and fundamental concepts of the subject matter, then no, it's not really worth anybody's time to listen.

>>2486265
http://www.youtube.com/watch?v=2h1E3YJMKfA

This is the "modern physics" approach to quantum mechanics. It's not the same kind of QM "real" physicists do, but this is a very good starting point. It's important to understand these concepts and ideas and the way the math is done first before jumping off the deep end into things like Hilbert spaces and second quantization.

Come on, guys, the troll line was 30 or so replies into this thread
>>2485724
>>2485724
>>2485724
>>2485724

Why is this thread still alive?

>>2486348
Thanks, I'll check it out.

>>2485803
>yes, consciousness causes collapse is considered the most likely interpretation of qm and this view is accepted by prominent quantum physicists all over the world, period
You've repeated this many times, but I've never seen you put forward any evidence to substantiate this claim. If you were to ask actual physicists their opinion on the interpretation of quantum mechanics, common responses are:

- something vague about decoherence [he doesn't understand it]
- shut up and calculate (decoherence will make sure you get the right answer whichever way you do it)
- it's a mystery (and decoherence makes it hard to solve) [the best answer]
- prefers many worlds / many minds
- a few prefer consciousness-causes-collapse
- their own favorite interpretation [there are many]

So if you watch the news, you alter events?

>>2486362
you never met atheists, have you?

What environmental decoherence tells us about Schrodinger's cat:

The cat's state of
<div class="math">{1 \over \sqrt{2}} |alive\rangle + {1 \over \sqrt{2}} |dead\rangle</div>
quickly becomes, through interactions with the environment,
<div class="math">{1 \over \sqrt{2}} |alive\rangle \otimes |env_1\rangle + {1 \over \sqrt{2}} |dead\rangle \otimes |env_2\rangle</div>
where the states of the environment <span class="math">|env_1\rangle[/spoiler] and <span class="math">|env_2\rangle[/spoiler] are nearly orthogonal.

But the environment is too complex to measure. Since we're only measuring the cat (or more realistically, a piece of the cat), the result of our measurement depends only on the reduced density matrix of the cat, which is
<div class="math">{1 \over 2} |alive\rangle\langle alive| + {1 \over 2} |dead\rangle\langle dead|</div>
the same as what it would be if you prepared the cat randomly in either the alive or dead state.

Note that this is not the same as saying the cat *is* randomly in either the alive or dead state. All it says is that whatever measurements you perform will have the same outcome as they would have *if* the cat had been randomly in an alive or dead state before you looked.

So whatever our interpretation of what was going on, the measurable results will always be the same. That's why these interpretations of quantum mechanics (except for objective collapse theories) are not scientific theories, but rather different metaphysical interpretations of the same scientific theory (a theory being defined by what testable predictions it makes).

>>2486703
This ignores that theories are not just means of calculating results, but explaining the results. Science is not done just by crunching numbers.

Assume first that observation collapses the wavefunction, and that the cat becomes either dead or alive when we check. This is a very reasonable proposition because it confirms with existing theory.

I postulate another possibility which ALSO confirms existing theory. Both cat AND environment are in a superposition state. The wave function does not collapse when we check. There are worlds in which |alive> is measured, and worlds in which |dead> is measured. However, the wave function is still around, and could potentially interfere with other wave functions.

The results are the same FOR THIS EXPERIMENT. However, we cannot say which picture (if either) is correct until we have a way of testing it. Just because this experiment doesn't discern between different explanations of the measurements doesn't mean others can't.

>>2486795
The problem of not being able to measure interference between different branches of the wavefunction is a very general one. It's not just something that's only true in one experiment; it affects every experiment. What we may be facing here is a fundamental limitation of science; ultimately empiricism fails to distinguish between two possible explanations. The best we can hope for is that quantum mechanics is only an approximation, and that eventually we will discover the more accurate theory in which some of these questions will be answerable. But then we will likely run into new questions we can't answer.

http://ebookee.org/Quantum-Enigma-Physics-Encounters-Consciousness_377143.html

>>2486839
And yet, the double slit experiment measures just this. Hard? Maybe. Impossible? Obviously not.

>>2487320
The double-slit experiment measures interference between branches of the wavefunction of a system that hasn't yet interacted with the environment. It's only after interaction with the environment that it becomes for all practical purposes impossible to see interference.

>>2487401
Good point. Instead, I submit to you superfluid helium. It certainly interacts with the environment, but doesn't collapse.

It's a photon that hits all the bullshit, how difficult is this to grasp? btw don't listen whart the others on sci tell you, they are jsut 12

>>2488480
You're confusing an effective field that happens to be complex-valued with the wavefunction (or state vector) of the system.