Quantum Physics simplified

Could a physicist (PhD) please explain in layman's terms what exactly "observer" means in the video? What kind of device is used to "see" which slit is used? Does it matter if the device is just measuring, or does it alter the result if the device is measuring and making the information available to a human observer?

I have heard too many confusing statements and when you look at the comments on youtube, well ... you get the point.

Here is the video. My question relates to the last part of the video. Everything before that I seem to understand (I think) LOL.

www.youtube.com...

A big thank you in advance!



[edit on 21-2-2010 by Nichiren]

I doubt you're going to find many PHDs here. You'd be better off asking someplace which is dedicated to science and physics. Or you may want to read books by prominent quantum physicists. Murray Gell-Mann has a decent one called The Quark and the Jaguar. An exert;

In any case the universe presumably couldn't care less whether human beings have evolved on some obscure planet to study its history; it goes on obeying the quantum-mechanical laws of physics irrespective of observation by physicists. p.137

I'm no physics major, but from my understanding it doesn't have anything to do with conscious observation, and doesn't rely on perception. It merely means that anything used to measure a phenomena will have some effect on the phenomena being observed by it's interaction with it. This may be direct or indirect.

For instance, a thermometer is not going to measure the exact temperature of a pot of hot water - because the thermometer itself is colder than the water it's submerged in - thus creating a heat differential that will cool down the water very slightly. Indirectly, observing the stars through a telescope will not interact directly to change the stars behavior - but the photons from the stars interact with the mirror and other capture/recording instruments.

So it doesn't matter whether or not something is consciously observing a phenomena, because a phenomena is always being "observed"/interacted with by it's immediate environment. Reality does not phase out into superposition when you're not looking.

This is evident since this effect on the quantum scale is not directly observable. Our eyes simply don't have the sensitivity necessary to detect individual photons, nor can we detect the vast majority of photon wavelengths. For an example, we can't see the UV light spectrum - but we can feel the heat from UV light on our skin.

[edit on 21-2-2010 by Lasheic]

reply to post by Lasheic


Thank you!

reply to post by Nichiren


It comes down to the fact that we cannot measure "an energy's location." By definition, energy doesn't occupy space, now how do you measure the location of something that doesn't occupy space? You can't. By default, it has to collapse into a particle(in other words, it has to occupy space) for us to measure its location. Otherwise, we measure nothing(in terms of its location), other than its energy.

[edit on 21-2-2010 by np6888]

For the past hour or so, I've been watching stuff on Quantum Psychics.

I actually forgot what possessed me to watch YouTube video after YT video and forgot this ATS page was open in another tab! This topic was what started it all! Thanks!

Edit: I'm watching this really interesting lecture at the moment, if anyone's interested:
www.youtube.com...

[edit on 21-2-2010 by LiQuiD_FuSioN]

reply to post by Nichiren

Quantum Physics is such an interesting topic.
I have a book by Nick Herbert called "Quantum Reality" in which he presents the case for Quantum Theory in layman's terms.

According to those with Phd's, Quantum Theory explains all the observable facts about our world. To me, it doesn't satisfactorily explain the strangeness of the quantum world when observed under certain conditions.

The double-slit experiment is such a case-in-point. It shows that when observed, be it by a human's eye or any other measuring device (sensor, etc) photons of light behave like a bunch of individual particles, unconnected to each other by any means.
If you had a device producing photons which fired them through a plate with a double-slit in it, and you had a photographic plate (film) behind that, the film would be exposed where the photons come through one slit or the other, revealing two "stripes" where the photons hit. This is what one would expect.
The photons are produced one by one and fired with a time-delay between each firing. They can only be considered to be particles.

But if you were to perform the same experiment described above, and left the room for a day leaving the experiment completely unobserved in any way, you would return to find an interference pattern on the photographic film, not two stripes like in the first experiment. This then shows that when unobserved, photons behave like a wave.
If you had shone a flashlight through the slits, you would be sending a light-wave consisting of billions of photons all interacting with each other and the environment, and the result would be an interference pattern. This is to be expected.

So how do photons in the second experiment know where on the photographic plate they should land? This is the strangeness of the Quantum world.
The photon apparently checks to see if it is observed. If yes, it behaves like a particle and goes through one slit.
If no, it goes through both slits simultaneously, interferes with itself, and after enough photons have done this, leaves an interference pattern on the plate.

The explanations given by Quantum Physicists to explain this strange behavior of photons boggles the mind and borders on the fantastic.
But they say it fits the facts.

So did the Lumineferous Ether...

Regards







[edit on 22-2-2010 by V1g0r0u5]

the "observer" is anything outside a specific system that effects the system. An instrument used to measure the system is generaly the observer as we as humans can't see individual photons because of the neural filters in our brain.

The conundrum in physics is eliminating the oberservers effect. The ideal observer would something that causes no perturbations of the system. The problem is that it seems that any act of "observation" causes a change in the system.

Originally posted by V1g0r0u5
reply to post by Nichiren

 

The double-slit experiment is such a case-in-point. It shows that when observed, be it by a human's eye or any other measuring device (sensor, etc) photons of light behave like a bunch of individual particles, unconnected to each other by any means.
If you had a device producing photons which fired them through a plate with a double-slit in it, and you had a photographic plate (film) behind that, the film would be exposed where the photons come through one slit or the other, revealing two "stripes" where the photons hit. This is what one would expect.
The photons are produced one by one and fired with a time-delay between each firing. They can only be considered to be particles.

Thank you.

Not sure I can follow. The video I linked to says otherwise. A Single Photon, or multiple, shot through double slits still creates an interference pattern. You only get two stripes when you determine which slit was used. If you're in the room and just watch the screen behind the slits, the interference pattern will emerge.

Best,

N

reply to post by constantwonder


But then the change should be permanent, regardless of whether we read the data or not. This shows that the device has nothing to do with the change, only our intent of reading the data or not does.

What I don't get with this is ... isn't the photographic plate also an 'observer' ? As at some point we look at it and get the results ?

Originally posted by V1g0r0u5
reply to post by Nichiren

 

you would return to find an interference pattern on the photographic film, not two stripes like in the first experiment. This then shows that when unobserved, photons behave like a wave.

I do appreciate all your posts! I just would like to caution you to use language as precisely as possible. Some posts are already ambiguous in terms of "change" and "observer".

Again, is there a PhD-level physicist who can explain the quantum double-slit experiment in layman's terms?

Thank you!

Originally posted by ppk55
What I don't get with this is ... isn't the photographic plate also an 'observer' ? As at some point we look at it and get the results ?

Originally posted by V1g0r0u5
reply to post by Nichiren

 

you would return to find an interference pattern on the photographic film, not two stripes like in the first experiment. This then shows that when unobserved, photons behave like a wave.

Hmmm...
you know, I'm not sure...
I am constantly trying to get my head around this stuff, and just as I think I'm making headway, a question like yours pops up and I have to take two steps back.

From what I understand (and I've only read a book half a dozen times) the plate in the experiment by it's nature records the impact of a photon. If it is an observer, it is a passive one... IDK...

What I got from Nick Herbert's double-slit experiment was the sense of how strangely the Quantum world behaves when unobserved.
If you were to note which slit the photon went through, two stripes.
If you left the room (you couldn't use your eyes or some sensor to note which slit the photon slipped through), interference pattern.

I think I'll dig out that book again...

Regards

reply to post by V1g0r0u5


Thank you.

What I got from Nick Herbert's double-slit experiment was the sense of how strangely the Quantum world behaves when unobserved.

This is an oxymoron. When "unobserved" a quantum particle doesn't behave in any way at all. We wouldn't know anything about it at all. As soon as we are recording information about the "cause and effect" of said element, we run into problems

reply to post by ppk55


Yes, the photosensitive plate is an "observer", but only after the particle has past the slits. The plate doesn't "care" if the particle went through the slit as a wave or particle.

It is important to know that i.e. the photon, when observed!, can only display characteristics of a wave or particle, but not both.

Quantum dynamics explains the electron shells of atoms.
The double slit results has no quantum attached.

Ether theory explains the wave properties.
I doubt the counting observations unless you use
Plank's constant with Heisenberg Uncertainty Principle
in not knowing momentum or position at the same time.
You have a quantum of error h/2pi < position x momentum
or something like that.

You pre determined the particle and thus the results are
a particle.

You tap the ether for momentum and position is somewhere
else.
ED: The referenced move which they do not explain the principles:



[edit on 2/22/2010 by TeslaandLyne]

reply to post by TeslaandLyne


I do mean this in no derogatory terms, but are you a PhD-level physicist? I have heard so many "good" opinions from laymen, but at the end they all make no sense.

Please define the term "observer" re the video.

Thank you!

Originally posted by Nichiren
reply to post by TeslaandLyne

 

I do mean this in no derogatory terms, but are you a PhD-level physicist? I have heard so many "good" opinions from laymen, but at the end they all make no sense.

Please define the term "observer" re the video.

Thank you!

Yeah they do not explain much.
If they did they might not be confused.
The only thing I recall is that if the position is known then the momentum
is unknown.
Basically they are propelling what they observe, or tell us, to be an electron
with a voltage like in old TV screens.
That might mean they know the momentum.
However voltage imparts force which sends the electron accelerating
to a screen.

Seemingly all they are doing is changing the variables.
So I don't know exactly, the observer might be voltage or some other
factor and not what they are showing.


ED:






Looking now at whatever is there.

ED2: I don't deal much with quantum stuff as I end with Tesla
who did different things with voltage. As far as the double slit the
whole particle or wave might be just an increase in voltage and
they would never tell you. But Tesla would.


[edit on 2/22/2010 by TeslaandLyne]

[edit on 2/22/2010 by TeslaandLyne]

reply to post by TeslaandLyne


Thank you TeslaandLyne.

My quest has taken my to those sites:

www.physicsforums.com...

physicsworld.com...

Best,

N

Originally posted by Nichiren
My quest has taken my to those sites:

www.physicsforums.com...

physicsworld.com...

Best,

N

You know the whole thing is reversed here.
They thought the electron was a particle and when wave results
came out that was too much like an ether explanation.

So called science must not talk about the ether and Tesla was the
only ether scientist.

I don't think they can prove the non wave results.
Sounds made up.

ED: So far Nichiren you are right in you questions.
What apparently is going on here is according to quantum theory
there should be a result with an observer, but has that happened.


[edit on 2/22/2010 by TeslaandLyne]