Life changing "Two Slit Experiment" .help please

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A couple of days ago i stumble across the two slit vid on youtube and entanglement.

before this day i thought quantum physics was just some kind time travel mumbo jumbo ..... Im sure you get my level of noobieness from this :)

ok questions if you would be so kind :)
( don't forget the noobieness ).

1: does the proton wave collapse through subconscious observation or mechanic photon detectors?

2: does the quantum entanglement of the photon being in 2 places at the same time mean that the photon can be in all places .... All the time ?

3:does the two slit experiment mean we know light is a wave but when observed it isn't ? And is this called duality ( two realitys ) ?


thank you :)



Ps........ I struggled answering the e=mc² question when i signed up for this site lol........that's how noobie i am :)
 

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  • #2
DrChinese
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1: does the proton wave collapse through subconscious observation or mechanic photon detectors?

2: does the quantum entanglement of the photon being in 2 places at the same time mean that the photon can be in all places .... All the time ?

3:does the two slit experiment mean we know light is a wave but when observed it isn't ? And is this called duality ( two realitys ) ?
Welcome to PhysicsForums, mainliner!

1. I know you mean photon rather than proton. Wave collapse is independent of consciousness as far as anyone knows. It occurs upon irreversible measurement or observation. So in the case you describe, when the photon detector "clicks".

2. Quantum particles are not in 2 places at the same time. But they have a chance of being in 2 different places. This is quite different.

3. The 2 slit experiment demonstrates several important quantum issues, including what I said in 2 above. No only can a particle have a chance of being in different places, it has a chance of taking different paths. The effect of these different paths causes interference between them, and that can be seen in the 2 slit experiment.

I don't think the wave vs particle analogy is all that great. But in the extreme cases, you could say that a photon sometimes acts as a wave, sometimes as a particle.

And it doesn't have anything to do with it being observed so much as its path being known.
 
  • #3
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Hello there

this is all new to me , it just interests me :)

now i understand the observation bit , how does the other wave collapse when they do that entanglement test 100 miles apart Through just electronic detectors ?


Ps.... Photon proton bad spelling lol
 
  • #4
DrChinese
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this is all new to me , it just interests me :)

now i understand the observation bit , how does the other wave collapse when they do that entanglement test 100 miles apart Through just electronic detectors ?
The principle is a function of the formalism (which is mathematical in nature) of Quantum Mechanics. But no one exactly knows the underlying mechanism. So what I can say comes down to this: a) distance does not matter; b) the order of the measurements (i.e. which one is first) does not matter. And when I say "does not matter", I mean there is no evidence that it does based on the statistical predictions of QM.
 
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So in reality the photons have two realitys .....one quantum and one classical laws of physics?
 
  • #6
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The principle is a function of the formalism (which is mathematical in nature) of Quantum Mechanics. But no one exactly knows the underlying mechanism. So what I can say comes down to this: a) distance does not matter; b) the order of the measurements (i.e. which one is first) does not matter. And when I say "does not matter", I mean there is no evidence that it does based on the statistical predictions of QM.
i looked your home page :)

the cartoons are an easy way for explanations lol
that's my level of QM :)
 
  • #7
DrChinese
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So in reality the photons have two realitys .....one quantum and one classical laws of physics?
There is a lot of debate about that. A lot depends on definitions. The word "reality" can a great many things in quantum physics. Most physicists think there is only a quantum world, but that it appears to behave classically in many situations.
 
  • #8
DrChinese
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i looked your home page :)

the cartoons are an easy way for explanations lol
that's my level of QM :)
Glad they were of use! :-)
 
  • #9
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There is a lot of debate about that. A lot depends on definitions. The word "reality" can a great many things in quantum physics. Most physicists think there is only a quantum world, but that it appears to behave classically in many situations.
can we only observe one at a time? ..... That's if there is two :)
 
  • #10
phinds
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can we only observe one at a time? ..... That's if there is two :)
It's not a matter of their being one or two, there are both simultaneously but what you observe depends on what you measure. The two-slit experiment at the macro level examines, and shows evidence of, both particle behavior and wave behavior. At the micro level it shows evidence of them one at at time (waves through the slit, particles on hitting the screen).
 
  • #11
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What exactly is it all about ?..... Quantum tunnling, entanglement, all this light phenomena etc etc and electromagnetic energy......why are the classic laws of physics all different and ....erm...well ..... Spooky.

being some one who believes in god and lucid dreams ....... This all seems to make sense in my non classically mind :).......why is this?
 
  • #12
phinds
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What exactly is it all about ?
It is about reality. Physics is the process of discovering and describing the characteristics of reality.
 
  • #13
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It is about reality. Physics is the process of discovering and describing the characteristics of reality.
is the characteristics of reality not how i know it , or the same but also different?
....after watching the two slit experiment
 
  • #14
phinds
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is the characteristics of reality not how i know it , or the same but also different?
....after watching the two slit experiment
I have no idea what you mean by "how I know it" since I am not you. How you "know" it is subjective and not likely to be helpful.

Things in cosmology (the very large) and Quantum Mechanics (the very small) are WAY outside of human's evolutionary experience and not anything that there was any survival value in knowing (because it was all unknowable for all but the tiniest portion of human evolution) so "common sense" and "intuition" are often not only not helpful in those arenas, they are downright counter-productive.
 
  • #15
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I have no idea what you mean by "how I know it" since I am not you. How you "know" it is subjective and not likely to be helpful.

.
"how i know it" ..... In a schoolboy physics class like for example , gravity and solids etc.

completely the opposite of "QUANTUM ENTANGLEMENT" thingy .

its all different....why?
 
  • #16
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And keep your post simple :) trust my first post ....... IM a noooooobie beyond belief :)

thank u
 
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  • #19
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I do constant reading and watching youtube videos on the internet :)
i just thought id get my info from the horses mouth as we say in England .

its just a puzzle to me im not quite sure what to make of it , the fact that i know about quantum entanglement is enough.

so light is a particle and a wave ..... And that's the true reality of physics?....
 
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It's neither, nor both - it quantum stuff - see our FAQ:
https://www.physicsforums.com/threads/is-light-a-wave-or-a-particle.511178/
thank you I'll read the link :) just one last q if you would ........ What do you mean " its neither, nor both , its quantum stuff" ?

please could you dumd it down for me ,if you'd be so kind :)

and keep it short if you want :)

its diffecult to get info like this in simple words rather than getting posted links to other threads when i could do that on google :)..... But whatever thanks .

iv just been trying to get an understanding of what exactly light is .
 
  • #22
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Hi Mat

May I suggest some layman books on Quantum theory for you to read:
- 'Sneaking a Look at God's Cards' by GianCarlo Ghirardi
- 'Quantum Enigma' by Bruce Rosenblum and Fred K.
- 'The Quantum Universe' by Brian Cox and Jeff Forshaw
- 'The New Quantum Age' by Andrew Whitaker
- 'Dance of the Photons' by Anton Zeilinger
- 'Quantum Mechanics and Experience' by David Albert
- 'Do We Really Understand Quantum Mechanics?' by Franck Laloe

.... just to name 'a few', in addition to a recommedation bhobba might (also has?) made - 'Quantum Mechanics: The Theoretical Minimum' by Leonard Susskind
 
  • #23
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its neither, nor both , its quantum stuff" ?
It's not a wave, its not a particle, its not a wave and a particle - its none of those things - its simply quantum stuff.

Thanks
Bill
 
  • #24
phinds
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thank you I'll read the link :) just one last q if you would ........ What do you mean " its neither, nor both , its quantum stuff" ?
What it means is exactly what it says. Light is NOT a particle, light is NOT a wave, light is a quantum object. Your problem is that you are trying to follow 80 year old physics and insist that the terms "wave" and "particle" are some kind of description of light. They are NOT. They are characteristics that are exhibited by quantum objects but that does not mean that a quantum object IS a wave or IS a particle. It's like insisting that a banana and a pineapple are the same thing because they are both yellow and they are both fruit. A banana is not a pineapple, but it DOES share the characteristic of being yellow. A photon is NOT a wave but it shares some of the characteristics of waves and it is not a particle but it shares some of the characteristics of particles. Light is a quantum object (so are electrons). Get used to it and move on.
 
  • #25
vanhees71
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Another hint from Einstein: "Don't listen to their [theoretical physicists'] words but look at their deeds." I mean, I don't recommend to read more socalled popular-science literature when it comes to quantum theory. I've not seen one book of this kind which gets it right. The reason is that you cannot get it right with some maths. A very good book out of this dilemma is the quantum volume of Suskind's "The Theoretical Mininmum". You cannot understand quantum mechanics with less math than you get explained in this nice book.

The reason for this minimum needed abstraction is that we have no intuition for things at the quantum level. There's only one thing in our everyday experience which is truely quantum: The stability of matter and the solidness of the stuff around us! Given the observation by the chemists of the 19th century and finally Rutherford with his famous gold-foil experiment that matter consists of discrete lumps of matter, now called atomic nuclei and atoms, which are charged quanta (note I say quanta, not particles or waves, which I reserve for the classical notions, where they make sense), the everyday experience of the stability and solidness of the stuff around us can (so far) only understood by quantum theory: There are bound states of electrons (negatively charged) with atomic nuclei (positively charged) which are static and don't radiate electromagnetic waves (or photons to keep it quantum) if in the ground state (i.e., there is a stable ground state at all). Further electrons are fermions, i.e., indistinguishable quanta for which the Pauli principle holds, and thus you can not simply move through a wall, because that needs tremendous energy to push the electrons in the wall "away" to make room for the electrons in your body.

Another example of everyday-experience that can only be understood from quantum theory are permanent magnets resulting from the spontaneous breaking of rotational symmetry due to the ordering of the electron's magnetic moments because of the quantum mechanical exchange forces (Heisenberg model of ferro-magnetism).

Nevertheless, when ignoring the microscopic structure of matter all this behavior can be described within classical physics, i.e., you look only at macroscopic observables like location and momentum of macroscopic bodies and the classical electromagnetic field as well as gravitational interaction of the bodies like the planets and the Sun in our planetary system. This classical behavior can, however, be derived from the underlying microscopic quantum theory via appropriate coarse-graining procedures (quantum-statistical physics), i.e., the classical behavior we are used to is due to a reduction of our perception to macroscopic observables which are sufficient for everyday life (and even more; the entire space program by NASA and ESA can be planned and manged with classical physics; the accuracy of the GPS involves relativity but also only on the classical non-quantum level, and so on). The classical behavior of macroscopic media is thus an emergent phenomenon from the underlying quantum dynamics.
 

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