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/sci/ - Science & Math

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[ERROR] No.3675358 [Reply] [Original]

Hey /sci/, I’m looking for different ways that quantum physics can question our reality such as the double slit experiment and the observer’s role in the collapse in the wave function. Any ideas?

>> No.3675369

>>3675358
You mean the different quantum interpretations. There are like fifty of them now. Popular ones being Many Worlds, Copenhagen, Dublex, and New-Copenhagen. Wikipedia has a list of them.

>> No.3675391

Copenhagen says that the wavefunction describes the observer's knowledge of the system, and collapsing it is just updating your knowledge.

Objective collapse theories say that the wavefunction is real, and there's some very rare process that causes collapse. But for a macroscopic system to collapse it only takes one collapse in trillions of trillions of atoms.

There's no evidence for the notion that consciousness causes collapse. It would be a sort of objective collapse theory, but very vague and human-centric. So it's not a very good theory.

>> No.3675422

>>3675391
I'm writing a paper on truth and reality, and merely using these theories as examples of ways this can be questioned. I am not arguing the validity of these theories but simply using the ideas that stem from these theories.

>> No.3675443

OP do you mean
>different ways that quantum physics can question our --accepted understanding-- of reality
?

Or do you mean ways that quantum mechanics conspires against our reality?

>> No.3675498

>>3675443
The way that quantum physics can question our accepted understanding of reality.
Apologies for any misunderstandings.

>> No.3675540

>>3675498

Didn't Heisenberg say all objects behave as waves and all waves behave as particles? Or was that merely an extrapolation from his equations of particle physics?

I tend to give physicists a break whenever they encounter such contradictions because in reality we have no clue how much of the Universe actually works. We've become exceedingly good at modeling theories that agree quite well observations, and maybe that's good enough for now.

>> No.3675552

Gravitons

>> No.3675591

>>3675540

There is nothing contradictory about wave-particle duality. It's just different from everyday experience.

>> No.3675611

>>3675391

This. There are competing interpretations of QM, and any one would be amazing if true. The stuff with consciousness, though, is just quackery from people who don't understand the actual facts of the experiment. "Observer" doesn't mean person.

>> No.3675613

>>3675591

Well, isn't that the barometer though? Is there anything else in our daily experience that contains such a duality? Waves and particles are on opposite ends of the spectrum, yet everything behaves as both a wave and a particle. It's strange.

>> No.3675628

>>3675613

But that's the thing. It's not really even a duality, except in how we relate it to our own experiences. It is one thing, that is in some aspects like one thing we're familiar with, and in other aspects like another thing we're familiar with.

>> No.3675647

>>3675628

Hmm. Perhaps you can expound on that. I'm thinking of the interference tests on electrons. Shoot a beam of electrons through a single slit and the electrons strike the screen one at a time like a particle. Shoot the same beam through a double-slit and the electrons constructively and destructively interfere on the screen like a wave.

How do the electrons know if there is only one slit or two? The same setup can be made more complex and still the electrons always seem to know when there are two slit rather than one.

I think it's just our way of reconciling a contradiction in our understanding to say it's an intrinsic characteristic of electrons to behave so oddly.

>> No.3675655

>>3675611
But there are legitimate debates about what an observer is; what CAN collapse probability waves?

>> No.3675665

>>3675647
Let me just make some comments:

A single slit also gives you an interference pattern, just a different one.

And in both experiments, the electrons are detected one at a time.

>> No.3675670

>>3675647

Hold a rock in your hand, and it remains in place. Take the hand away, and it accelerates downwards. How does the rock know whether your hand is there? Isn't the stay in place-accelerate downwards duality of rocks weird?

>> No.3675672

>>3675655
This question assumes
(1) the wavefunction is a real thing
(2) the wavefunction collapses
Even assuming these things, the answer is still that we don't know. But there are some ideas. Look up GRW theory for an example. There are other ideas, of course, that don't make the two assumptions above.

>> No.3675684

>>3675670

lolno

That was a pretty awful example to give. The rock is trying to accelerate down in both cases. In one your hand prevents it from falling by applying an equal and opposite force as gravity. In the other that force is eliminated.

That was pretty bad. Explain how an electron knows whether there is only one or two slits? Each one can only pass through one slit or the other, so how do they know?

I think you're reaching now to explain a concept you don't fully comprehend but want to excuse as simple.

>> No.3675690

>>3675655
>But there are legitimate debates about what an observer is

There isn't any legitimate debate about whether it has to be an actual person.

>> No.3675696

>>3675684
>wooshing noise

>> No.3675713
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[ERROR]

>>3675696

Cover your ears so you don't catch a draft.

Seriously, that analogy was atrocious.

>> No.3675732

I've noticed that a lot of /sci/ likes to spew so called facts to prove that they are smart.
congrats to thinkers
>>3675628
>>3675670
>>3675672

>> No.3675744

>>3675684

I'm not commenting on whether it's "simple." In fact, how the rock "knows" to accelerate in one case and not the other is actually very interesting and complex. Saying the hand "prevents it" is not an explanation at all - it's just restating what happens. But we tend to accept it, because the situation is so familiar.

>> No.3675753

>>3675732

If it contradicts scientific consensus, it's free thinking.

If it repudiates sound logic, it's open-minded.

kk.

>> No.3675770

>>3675753

None of those posts contradict scientific consensus or repudiate sound logic.

>> No.3675790

>>3675744

Fine. Let's reset the discussion so we're both on the same heading.

Particles exhibit characteristics of waves.
Waves exhibit characteristics of particles.
(Both are extrapolations of Heisenberg's equation).

A single electron is shot through a single-slit experiment and behaves as it should: striking a screen in a single spot.

A beam of electrons is shot through a double-slit experiment and the electrons as a unit behave as a wave (interference patters).

Single electrons behaving both as waves and particles depending on the experiment. Duality.

Now, I recognize analogies aren't 1-to-1 agreements between two different arguments, but the rock one just doesn't seem to fit at all. The rock isn't doing anything different in either case. The change in its behavior is attributed to the presence or absence of the hand.

Your move.

>> No.3675827

>>3675790
your right but my point had to do with ORIGINAL thought
my only other post ITT btw
>>3675732

>> No.3675865
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[ERROR]

>>3675790

The rock does fit. It's clearly doing something different in each case (accelerating or not), depending on the physical arrangement of the experiment (the presence or absence of a hand).

>Particles exhibit characteristics of waves.
>Waves exhibit characteristics of particles.

More like, classical particles and classical waves are both limited analogies for reality.

>> No.3675881

>>3675827

I see. My only problem with the concept of original thought is that it's so unbounded. But that's probably why it's so powerful a tool of discovery.

I still wish someone could shed some light on the duality question, but if my physics professors were baffled by it, then there's very little chance of a concrete explanation being posted on /sci/.

>> No.3675885

>>3675790
You've made two changes to the experiment; why would you expect to get the same result? Is it because of
>>3675684
>Each one can only pass through one slit or the other, so how do they know?
?

I would say that the assumption that only one slit has things passing through it is wrong. In any interpretation consistent with the facts, something (not necessarily the electron) passes through both slits.

>> No.3675901

>>3675865
>More like, classical particles and classical waves are both limited analogies for reality.

Heh. That's actually what I said in my first post in this thread (not OP). My example of the behavior of electrons was designed to support that claim.

Love that pic, btw. Saved (even if it's meant to ridicule me in that post).

>> No.3675915

>>3675885

That's exactly what I mean, actually. It's not that a change in the experiment shouldn't result in a different outcome, it's the (seeming) contradiction is the outcomes.

One electron behaves as a particle. A beam of electrons as a system behave as a wave. Shoot a single electron, and then another single electron, and then another, and ... until a sufficient number of electrons have been shot and what do you get?

An interference pattern on the screen.

Explain why.

>> No.3675959

>>3675915
Why the electron shows up at a single point at a detector but can seem to be in multiple places at once when nothing is looking at it?

There are lots of ideas, but nobody knows what the right one is. I can describe some of them to you if you're going to stick around a bit. Or you can just look up "interpretations of quantum mechanics."

>> No.3675966

although the mathematics of the dual slit experiment work out,there's something about the wave/particle theory that just doesn't "feel" right.

is it just me?

>> No.3675967

>>3675915
>Explain why.

I'd say there's some interference.

>> No.3675973

>>3675959

Exactly what I'm looking for, actually. Post some if you don't mind.

>> No.3675978

>>3675966

Nope, that makes two of us.

>>3675967

Yes, but why is the question. Why does it behave in that way.

inb4 it just does

>> No.3675991

Somebody just watched What the Bleep Do We Know and now thinks that an "observer" means that someone is literally observing what's going on.

>> No.3676008

>>3675915
I'm not as familiar with the 2 slit xperment as I'd like to be though I've recently tried it at home.

if it was 1 photon at a time would there be more than 2 light stripes?
according to the interference theory, no. amirite?

sorry if I'm behind, I'm drunk

>> No.3676013

>>3675978
>Yes, but why is the question. Why does it behave in that way.

Just saying "why" is easy, but I think actually thinking about what the question means how it should be formulated is a better use of time. What sort of explanation would be satisfying?

>> No.3676030

>>3676008

I'm not sure. A single photon behaves as a point-particle and as a wave, right? So it would behave as a leading edge on the OP's picture and interfere with the portions of the wave that go through the two slits.

Maybe this guy can answer if better >>3675959.

>> No.3676036

>>3676013
>What sort of explanation would be satisfying?

Oh, I don't know, maybe one that reflects reality in the best way we can comprehend it? I'm not looking for fairy tales. I'm asking for a deeper understanding of the mechanics of particle-wave duality. Why does it behave the way it behaves.

That's what science is, right?

>> No.3676042

>>3675973
It could be that there's a rare process that collapses the wavefunction -- reduces it from a spread out wave to a localized wave packet. When the electron reaches the detector, the wavefunction of the electron + all the other particles becomes entangled. "Entangled" is a technical term that means I have to use a single wavefunction that describes all the particles; one function for each particle doesn't work anymore. If the rare collapse process happens to any of the entangled particles, the wavefunction is collapsed, affecting all of the particles, including the electron. And this causes the electron to end up as a localized wave packet.
(This would be objective collapse theories such as GRW.)

It could be that there is both a wave and a particle. The wave guides the motion of the particle. The wave passes through both slits, but the particle will only be detected at one location. This is the deBroglie-Bohm pilot-wave interpretation.

It could be that the electron is still spread out. But when you look at it, you get spread out into multiple copies: one copy for each point you could have seen the electron at. This is the many-worlds interpretation.

Or it could be that there are two wave functions that determine the electron's behavior -- one propagating forward in time from the past and one propagating backward in time from the future. The wave function coming from the past is spread out when it hits the detector, but the wave function coming from the future is localized in space due to the measurement process. And it's the region where the wavefunctions overlap that matters. This is the idea of time symmetric interpretations.

>> No.3676046

>>3676036
>Oh, I don't know, maybe one that reflects reality in the best way we can comprehend it?

Meaning what?

>That's what science is, right?

Science is a method for improving our predictions about the world.

>> No.3676048

>>3676030
so if a photon is a wave, a single one will create interference.
if it is a particle it won't

which leads me to my next question.
is the technology available to fire a single proton?

>> No.3676064

>>3676008
Single photons at a time through two slits one at a time still exhibit wave interference.

As well, single electrons, short through slits exhibit wave-like interference as well.

WHY you ask?

http://en.wikipedia.org/wiki/Uncertainty_principle

In terms you can understand, wavelengths of objects are how you can measure how something behaves in an area.

Wavelengths are based on really small numbers... so only very small things are affected by them significantly.

Photons are infinitesimal. Since there is literally empty space between individual photons and other things, since they are so small, there's nothing "stopping" it from being spread out like a wave. That is... until something interferes with it so it will be there where it was interfered with at that point in time, nothing is stopping it from being at a specific concrete place in space and time.

That's "why". A deeper explanation requires you to be aware of what "nothing" means and what the word "intrinsic" means and to know what "quantum" means.

>> No.3676071

>>3676042
>this poster has read one too many sci fi shows and has literally no knowledge of physics at all

>> No.3676072

>>3676046

And those predictions are based on understanding how things work. We eat to live but why does eating sustain life? It's not some method of prediction, it's understanding the steps that make up digestion.

I don't know what kind of new-age stuff you're on about. I just want to know how duality works. If I want to know how the Sun works, I read up on nuclear fusion. What do I read up on to understand duality.

This looks like a start >>3676042.

>> No.3676078

>>3676042
I'm confused
why are you guys saying electron instead of photon?

forgive my drunk ass. Very interested though

>> No.3676085

>>3676046
>>3676036
>>3676013
>>3675978

Feynman talks about "why" questions, with regards to magnetism:

http://www.youtube.com/watch?v=wMFPe-DwULM

>> No.3676090

>>3676048

As I understand it, both electrons and protons behave the same way.

>> No.3676095

>>3676078

Because that's how we're meshing waves and particles. Electrons are particles that exhibit wave-like behavior. Photons are waves that exhibit particle-like behavior.

You can actually perform the test using electrons and protons. Then compare it to a test using photons. Same outcome.

>> No.3676097

>>3676085
Feynman gives a really dumbass explanation there.

He should have just said something like "Some things are the way they are, just because they are that way" instead of going on some long-winded explanation.

People don't understand that everything isn't infinitely reducible.

>> No.3676105

>>3676097

Just curious, but what made you so jaded?

>> No.3676111

>>3676072
>And those predictions are based on understanding how things work. We eat to live but why does eating sustain life? It's not some method of prediction, it's understanding the steps that make up digestion.

But it IS just prediction, specifically predicting how certain chemicals will react with each other, and what they will do when you put them in a living thing.

"Understanding" here seems to just mean comfort, and comfort seems based primarily on familiarity.

>> No.3676118

>>3676097
>He should have just said something like "Some things are the way they are, just because they are that way" instead of going on some long-winded explanation.

The long-winded explanation is an attempt to show what "some things are the way they are" means, and that it isn't really an evasion even though it superficially seems like one. It's an attempt to make us think about what "why" means, which is more valuable than any brief response would be.

>> No.3676125

>>3676118
My point was just that his explanation was stupid unless you already knew what he was talking about or already understood what he was trying to say.

>> No.3676130

>>3676095
ahh thanks
food for thought

so, light is actually traveling electrons that exhibit wave like properties that cant be explained by a simple particle?

>> No.3676133

>>3676130
No, particles of light are photons. Electrons are a different type of particle/wave.

>> No.3676148

>>3676133
that's what I thought, but this confused me
>>3676095

>> No.3676166

ive always hated the analogy of waves to being like rippless spreading out in water, or the one of it being like sound compression waves in air.
with all my understanding of physics, it makes me RAGE that you cant explain what the medium that is waving. in water its crests and dips from gravity, in sound its high and low pressure of the air, what the hell is light waving through?

>> No.3676173

Question for the theorists.
Is there any way could sound be defined as a particle?

>> No.3676185

>>3676166
The thing that's waving (and by waving I mean oscillating in value, not necessarily position) is the electric and magnetic fields. They're properties of space that can be described by vectors. This is the classical physics answer, at least. (Of course, one may have different interpretations of classical physics as well, treating the field as an abstraction and invoking action at a distance. But this doesn't work well with the modern quantum theory.)

>>3676173
http://en.wikipedia.org/wiki/Phonon

>> No.3676220

>>3676185
electromagnetic fields is a property of space, which is nothing. I cant seem to get my head around that, space is oscillating in value? i just nod my head and crunch the numbers and they work, but i hate not understanding the photon.

>> No.3676232

>>3676148

Their behavior in certain experiments is similar. Electrons and protons make up atoms. Photons are energy-packets that primarily behave as waves (self-propagating electromagnetic waves).

Comparing how they behave in the double-slit experiment is intended to reveal intrinsic properties of waves and particles.

Electrons and protons can be focused into a beam though.

>> No.3676248

>>3676220

Want to get really confused? Look up the photoelectric effect. Photons hitting a piece of metal and being instantaneously absorbed and their energy being expelled as free-orbit electrons.

>> No.3676266

>>3676220
Who says space is nothing?

>> No.3676271

been an electronics hobbyist for 20 years so I understand electrons,shells,valence,ect
>Their behavior in certain experiments is similar
what experiments? I am intrigued

>> No.3676279

>>3676271
For example:
http://www.youtube.com/watch?v=ZJ-0PBRuthc

>> No.3676299

thanks. I'll look at this again in the morning when I'm sober.
I doubt I'll be any less WTF though

>> No.3676310

>>3676248
Actually that seems pretty intuitive to me. i get chromodynamics. the electron just absorbed the photon and got more powerful. patricles are in my comfort zone, and them absorbing or transmuting into each other is amazing, but understandable. empty space oscillating boggles my mind.
are photons like ripples in the fabric of reality? it makes me as uncomfortable as imagining existence in 4d

>> No.3676315
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[ERROR]

>>3676310
>are photons like ripples in the fabric of reality?

Sounds good to me. Let's run with it.

>> No.3676318

>>3676315

And by "run with it" I mean publish our discovery in a prestigious scientific journal for peer review and infamy--er, fame.

>> No.3676326

>>3675358
Double slit has nothing on Bell's Inequalities. I want counterfactual definiteness, and I want locality. The evidence says I have to give at least one of those up, though.

http://www.stat.physik.uni-potsdam.de/~pikovsky/teaching/stud_seminar/Bell_EPR-1.pdf

>> No.3676330

>>3676310
its a very personal point for me, every one has a limit to their understanding where things aren't easy or intuitive anymore and you have to just run with what other people assure you is true. Hitting that wall makes me hate the concept because it becomes a definition of my limitations, unless i can crack it. i'm just not satisfied with the unknown, especially if there are others who do 'get it'

>> No.3676338

>>3676330

Take comfort in knowing everyone has those walls, including Einstein and his contemporaries. The difference is when they didn't "get it" no-one else did.

>> No.3676360

>>3676338
Its a point of pride to be able to grasp a concept. i can work with it as if i believed it was true, but it just seems like such nonsense.

If photons are popping in and out of existence and the wave is the possible area for it to "pop", how does wavelength determine energy levels of said photon? And furthermore how does placement in said vectors make frequency have an inverse relationship to wavelength?

>> No.3676672

>>3676360
no expert in light but...
frequency = cycles per second
wavelength = time for 1 cycle
F=1/W
W=1/F

captcha:Ana nomyUSA
>nomyUSA
huh?

>> No.3676711

>>3676672
i know the formulas, but why is does that measurement pertain to the areas light particles pop in and out of existence? what makes a shorter wavelength, therefore area of possibility, give it higher energy? There are huge holes in cause and effect that make it difficult to sound rational.