Basic Double Slit Experiment Question

[Strange]

 

If the electron really were a wave, then part of the wave will always be inside the interior of the barrier, where the electron / wave would not be able to proceed, and it would become trapped inside the barrier.

 

Electrons (and photons) are quanta or fundamental. Part of the electron or photon cannot be left behind.

 

When you consider light classically, then clearly some will get through the slits, some will be absorbed and some reflected. But any individual photon (or electron) can only follow one of those routes ... with a probability that reproduces the classical distribution.

[JoeLight]

"When an electron is fired"? If it was a definable object, then it simply couldn't go through two slits, be everywhere at the same time or any other weirdness we care to ascribe. Saying it 'travels' is an assumption. All we can say is there's an event at the source followed by an event at the destination. What happens in between is anybody's guess.

 

When we attempt to detect the thing (I'm calling it a 'thing' for convenience) at one of the slits, we've in effect created a destination, which then becomes a second source - and so on. In other words a completely different situation or experiment as evidence by the different result (no interference pattern). What happens to this thing whilst what we would refer to as actually being 'in flight' is an assumption - and I suggest there's no place in science for assumptions. I further suggest we have no evidence whatsoever that there is a thing (electron, photon or whatever) actually flying from place to place.

 

And what's more, if it were an actual 'thing', then the thought of it passing through two slits at the same time (or more if there are more than two), then that's something from Alice in wonderland and has no place in science.

 

In other words it can't travel through two slits. And if it's deemed to have actually passed through two slits (as evidenced by the two slit experiment), then it cannot be an identifiable object.

 

What is it then? My conclusion is that there's an event at the source followed by an event at the destination. What happens in between is probably some sort of maelstrom of interactions and interchanges. A thing that we might call an electron or photon never travels from A to B. Which begs the question whether or not such things actually exist - but doubtless my imagination is now running into the heights of hyperbola!

This is good stuff, I used the word "fired" for lack of a better term. I totally agree with you. I don't think the electron really travels at all. I'm wondering if maybe the potential for the electrons existence at any point in space time traveling from point A to B. Even in an atom an electron doesn't have a definite location relative to the nucleus. The electron just exists anywhere and everywhere in its orbital. We can interact with that electron and when we do it briefly has a definite location in space.

 

What if this potential for the electron to exist as a particle behaves like a wave. As that potential passes the detector the detector interacts with the electron giving it a definite location in either slit 1 or 2. Meaning there is now only a potential for existence at whatever slit the electron is currently at. With only one wave at one slit there cant be an interference pattern.

 

However, when you take the detector away the electron is no longer interacted with at the slits and it has no definite location in space, so the potential now has 2 waves, a wave at slit 1 and a wave at slit 2. If the potential does behave like a wave you would then get the interference pattern where your detecting the electron at point B.

 

To me this would explain why an electron behaves like a particle when your looking at it and a wave when your not which is why the probability equation always accurately predicts the electrons location. The interaction with the electron at the slits is the only thing changing in the experiment. We all know this.

 

I'm proposing interaction with the electron is what makes it behave particle.

 

I don't have the means to perform any sort of experiments for this idea. I'm just throwing it out there for someone else who can.

Edited July 31, 2014 by JoeLight

[robinpike]

 

Electrons (and photons) are quanta or fundamental. Part of the electron or photon cannot be left behind.

 

When you consider light classically, then clearly some will get through the slits, some will be absorbed and some reflected. But any individual photon (or electron) can only follow one of those routes ... with a probability that reproduces the classical distribution.

 

If the electron / photon only follows one route - how does the interference occur?

 

And yet that's precisely how they behave, which has been known for >75 years.

 

But they don't behave as waves!

 

We know that they don't behave like waves by the example of waves in a water tank...

 

A water wave never passes through the wall - only through the gap. When the part of the wave meets the wall, that part is reflected back.

 

Electrons and photons are never partially reflected back - they are either completely absorbed by the wall / completely reflected by the wall, or they are completely able to pass through the slit and appear on the other side.

 

The failing of the many paths route / wave explanation, is that for all the possible paths that put the electron / photon at some point inside the wall - that will stop the progress of the electron / photon completely.

[swansont]

 

If the electron / photon only follows one route - how does the interference occur?

 

But they don't behave as waves!

 

We know that they don't behave like waves by the example of waves in a water tank...

 

A water wave never passes through the wall - only through the gap. When the part of the wave meets the wall, that part is reflected back.

 

Electrons and photons are never partially reflected back - they are either completely absorbed by the wall / completely reflected by the wall, or they are completely able to pass through the slit and appear on the other side.

 

The failing of the many paths route / wave explanation, is that for all the possible paths that put the electron / photon at some point inside the wall - that will stop the progress of the electron / photon completely.

 

Saying that there is no partial reflection of the individual quanta is a different argument. No, there is not, because there are quantized properties that you can't split up. Just as individual water molecules can't be partially reflected, and yet water waves exist.

 

Electrons and photons can be reflected and more importantly can diffract and interfere, which are wave properties.

[Strange]

 

If the electron / photon only follows one route - how does the interference occur?

 

Choose your interpretation: many worlds, Copenhagen, pilot wave, etc. etc. These are all fairy tales to answer people who ask "how" so you can choose whichever appeals. Or make up your own. It makes no difference to the theory or what happens.

 

We don't actually know what the photon does between the source and the detector. And if you change the experiment to find out, then you no longer have an experiment that can produce an interference pattern. But we do know that you either see a whole photon or no photon (ditto electrons).

 

 

But they don't behave as waves!

 

Yes they do.

 

 

We know that they don't behave like waves by the example of waves in a water tank...

 

Well, not surprisingly, they don't behave like that because they are not waves in water tank. They don't behave like elephants riding motorbikes, either.

Just as individual water molecules can't be partially reflected, and yet water waves exist.

 

That is a good analogy

[Delbert]

 

A water wave never passes through the wall - only through the gap. When the part of the wave meets the wall, that part is reflected back.

I suppose it depends how long the wall is. If the length of the wall is shorter than the wavelength of the water wave the situation will be different.

 

Just saying a wall without defining it's length is not good enough, the wall has to be longer than the water wave.

 

 

The failing of the many paths route / wave explanation, is that for all the possible paths that put the electron / photon at some point inside the wall - that will stop the progress of the electron / photon completely.

It seems you're viewing the electron or photon as a little billiard ball. It cannot be a definable object as we perhaps understand a definable object - if for no other reason than the consequence of two slit experiment.

 

If it were a definable object it would have the properties of such - like volume, surface area and so on. The billiard model is the Rutherford model - just a way for us simple humans to deal with the things. Doesn't mean that's what they are like, or anything like.

[hoola]

I see that consciousness affects the particles but only indirectly, as certain mechanical interactions result in selective information extraction of a particle, reducing/masking overall or partial descriptive content of the particle, limiting expression to one property aspect only (default minimum). Is there a test that would allow for wave only results, and isn't that the "weak measurement" test I heard about? Label me and I am less...spinoza What about a weak label? Now, what about a test that is run that normally would provide a particle only result, the setup is complete, the test performed, by no one looks at the results on the test display screen, only the screen that the particles impact? Does the equipment act as our proxy by observing for us, although those machines that run the test are an unnatural intrusion caused by human consciousness, so therefore, still casually responsible?

[swansont]

I see that consciousness affects the particles

 

No, it doesn't.

[Delbert]

I see that consciousness affects the particles...

Consciousness has nothing to do with it. I suggest consciousness is a debatable concept in any case.

 

If anything, it is a collective name for the complex chemical processes that take place in that lump of sponge in our heads, and nothing to do with things like two slit experiments.

 

Perhaps you've taken the phrase in the above video about looking at the slits too literately. If there is a connection, it is only the detection (in our eye) of photons associated with the photon or electron we're trying to observe that then affects the photon or electron we're trying to observe. Or something like that!!!

 

I suppose one might then ask what happens to the photon if our eye isn't in the way? Maybe it zooms off into space and doesn't react with something for a few million years! If so, presumably at the local level events will unfold to fit the physics of it's non appearance or reaction. Perhaps my imagination is wandering into heights of hyperbole once again.

 

I'll agree that in the apparent common sense world that millions of years of evolution have engrained into our minds and thought processes, the subatomic world might appear weird.

[barfbag]

The idea of consciousness affecting reality is not true. It is the same leap mankind has made thousands of times in the past contributing consciousness or religion to something we cannot yet explain.

 

This is my current belief of the mechanism behind it.

 

The view that an electron can go through both slits simultaneous and interfere with itself is not possible. Once the physical structure of the election is solved, then the supposed weirdness is dispatched. For example, the electron double slit interference pattern is due to the changing electric field of the incident traveling electron inducing currents in the conducting slits and the induced corresponding E&M fields of the currents cause a change in the angular momentum in the electron. The change in angular momentum in turn results in a transverse displacement in the electron position in the far field. The pattern of many electrons at a detector in the far field is that of the high and low intensity fringes of the so-called interference pattern; albeit, the physical mechanism does not involve interference.

 

 

The movement of an electron itself creates a magnetic field that has not always been considered.

 

I must say again though that there are various interpretations of The Copenhagen Interpretation.

 

NOTE: The Double Slit experiment is still confusing and confounding to many. There is no one accepted Theory that explains its mysteries.

 

I am sad ( If you are familiar with some of beliefs you would realize I'd like the Dr. Quantum view to be accurate) to say that consciousness is not involved, but it is not.

Edited August 1, 2014 by barfbag

[swansont]

 

When the electrons are fired with the apparatus having NO slits present, the electrons never get through the barrier, they never appear on the other side.

 

No, not true. Particles can tunnel, and appear on the far side of barriers.

 

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

 

This is my current belief of the mechanism behind it.

 

Is your belief backed up by any evidence? e.g. what happens when electrons pass through slits in a non-conductive material? Shouldn't the pattern depend on the conductivity of the target?

[Strange]

This is my current belief of the mechanism behind it.

Hmmm....

 

 

The movement of an electron itself creates a magnetic field that has not always been considered.

 

Not considered by whom?

 

 

I must say again though that there are various interpretations of The Copenhagen Interpretation.

 

An interpretation of an interpretation? I'm not even sure what that means...

 

 

There is no one accepted Theory that explains its mysteries.

 

There is one theory that explains it fully. With no mysteries.

[barfbag]

There is one theory that explains it fully. With no mysteries.

 

 

I had said, "Fully accepted". This includes Bohr and Dr. Quantum/Fred Alan Wolf. Thus Interpretations of interpretations.

 

From Wikipedia on topic of Copenhagen Interpretation

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

According to John G. Cramer, "Despite an extensive literature which refers to, discusses, and criticizes the Copenhagen interpretation of quantum mechanics, nowhere does there seem to be any concise statement which defines the full Copenhagen interpretation."

 

The term 'Copenhagen interpretation' suggests something more than just a spirit, such as some definite set of rules for interpreting the mathematical formalism of quantum mechanics, presumably dating back to the 1920s. However, no such text exists, apart from some informal popular lectures by Bohr and Heisenberg, which contradict each other on several important issues

 

 

I think saying Interpretations of interpretation should be clear to anyone reading the above two quotes.

 

The people introducing the topic were not even in agreement on some issues.

 

Anybody who does not realize The Copenhagen Interpretation has been used to support theories here and elsewhere that consciousness causes collapse surely must be very unfamiliar with the topic. Yet others will say that is not what it is saying at all.

 

@ Strange,

So when you say...

An interpretation of an interpretation? I'm not even sure what that means...

 

 

I must answer, "How could you not"?

 

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

 

Consistent histories is one interpretation of The Copenhagen Interpretation.

 

Objective Collapse Theory is another

 

Yet there are many other ways Interpretations of the Copenhagen Interpretation have been abused and twisted to support all kinds of nonsense.

 

http://physics.about.com/od/quantuminterpretations/fl/What-Is-the-Copenhagen-Interpretation-of-Quantum-Mechanics.htm

 

There is no 'official' Copenhagen interpretation. But every version grabs the bull by the horns and asserts that an observation produces the property observed. The tricky word here is 'observation.'...

 

 

Every VERSION... That means this author also thinks there are various versions of The Copenhagen Interpretation. Is that not the same as saying Interpretations of The Copenhagen Interpretation.?

 

I see it.

 

(same citation as last quote)

the exact nature of the Copenhagen interpretation has always been a bit nebulous.

 

neb·u·lous[neb-yuh-luhs] Show IPA

adjective

1.

hazy, vague, indistinct, or confused: a nebulous recollection of the meeting; a nebulous distinction between pride and conceit.

How could you not?

 

I think any of us could cite a dozen other sources that say the exact same things about it.

 

so... I will reiterate... and stand by my statement...

 

I must say again though that there are various interpretations of The Copenhagen Interpretation.

 

 

although I should now say again and again.

Edited August 2, 2014 by barfbag

[Strange]

 

I think saying Interpretations of interpretation should be clear to anyone reading the above two quotes.

 

OK. Fair enough. I have never paid much attention to interpretations of quantum theory, Copenhagen or other. They all seem pretty irrelevant. It is hardly surprising that informal descriptions will have variations; I had never heard it described that way before.

 

 

I had said, "Fully accepted". This includes Bohr and Dr. Quantum/Fred Alan Wolf.

 

Are you saying that they did not accept quantum theory? I am not aware of Bohr having any reservations (unlike Einstein, say). And I have no idea who Fred Alan Wolf is.

[barfbag]

Are you saying that they did not accept quantum theory?

 

 

No. If you look at how they view The Copenhagen Interpretation you will see that was merely an example. Fred Alan Wolf (Aka Dr. Quantum) is somewhat famous but uses TCI to give religious connotations where they do not exist. Bohr helped create TCI, and he did not agree with many either on this topic. That is why I used them as examples.

[Strange]

OK. But arguments about, or the use/misue of one or more interpretations (or interpretations of interpretations), doesn't seem relevant to the statement that "There is no one accepted Theory that explains its mysteries".

 

There is one theory. It is fully accepted (*). And it explains all "mysteries" (i.e. counter-intuitive behaviour).

 

(*) OK. I'm sure there are a few people who question some aspects of it. That is a good thing. Einstein's continual questioning of QM, for example, helped make it a stronger theory.

Edited August 2, 2014 by Strange

[Delbert]

 

Particles can tunnel, and appear on the far side of barriers.

Correct. I understand semiconductors have been using this phenomenon for a long time, to the extent they wouldn't work without it.

[Strange]

Correct. I understand semiconductors have been using this phenomenon for a long time, to the extent they wouldn't work without it.

 

It is both a good and a bad thing. It is an increasing proportion of leakage current as devices get smaller but, on the other hand, it is essential for devices such as flash memory.

[robinpike]

 

Saying that there is no partial reflection of the individual quanta is a different argument. No, there is not, because there are quantized properties that you can't split up. Just as individual water molecules can't be partially reflected, and yet water waves exist.

 

Electrons and photons can be reflected and more importantly can diffract and interfere, which are wave properties.

 

Analogies have to be used with care ...

 

True, the path of a single water molecule is never partially reflected, but on the other hand, a single water molecule is also unable to interfere with its own path.

 

So when the experiment is done with discrete photons / electrons over time, what is the explanation for how the photon / electron interferes with itself?

 

Both the wave explanation and the multiple path explanation, have difficulties.

[Delta1212]

 

Analogies have to be used with care ...

 

True, the path of a single water molecule is never partially reflected, but on the other hand, a single water molecule is also unable to interfere with its own path.

 

So when the experiment is done with discrete photons / electrons over time, what is the explanation for how the photon / electron interferes with itself?

 

Both the wave explanation and the multiple path explanation, have difficulties.

And yet, it still happens. Look, photons are not treated as waves. Nor are they treated as (classical) particles. They do, however, have both wave-like and particle-like behaviors. Like a wave, they can interfere with themselves. Like a particle, they don't get partially reflected.

[Strange]

 

True, the path of a single water molecule is never partially reflected, but on the other hand, a single water molecule is also unable to interfere with its own path.

 

Actually, it can do, under the right circumstances. The double-slit interference experiment has been done with large molecules, such as C60 ("buckyballs).

 

 

So when the experiment is done with discrete photons / electrons over time, what is the explanation for how the photon / electron interferes with itself?

 

The "explanation" is: that is how quantum phenomena work.

 

 

Both the wave explanation and the multiple path explanation, have difficulties.

 

All such "interpretations" have problems, because they are just analogies. In the end, at the quantum scale things are not localized (in time or space) and so the behaviour of particles is affected by everything around them (the presence of a second slit; the presence of detectors that can detect which slit the particle went through, even if indirectly; measurements made after the interference could take place; etc. ...)

Edited August 4, 2014 by Strange

[JoeLight]

I would never go as far as to say consciousness has any impact on reality. But our own consciousness does limit what we are able to observe. The human body has limitations. For instance a microscope only enhances the ability of the human eye to see something very small. Who knows how much is out there that we don't know about, that we have never and will never see. Dark matter for instance is something that mathematically makes since but we as humans have never found a way to observe or interact with it. Nobody really knows what it is or even if it is. Human evolution has only given us a limited set of senses that allow us to observe the universe. There are even things our subconscious mind does that we are never aware of without the help of technology. But technology can only do so much. In that sense our consciousness limits our knowledge of reality. Not that it alters reality in anyway but our snapshot is skewed. Unfortunately because of this human limitation we may never fully understand the universe. Its a sad tale

[Strange]

Dark matter for instance is something that mathematically makes since but we as humans have never found a way to observe or interact with it.

 

Well, we can observe it; that is why you can find papers describing the distribution of dark matter in the universe, for example.

 

But if there are things that we can never observe (i.e. they have zero effect on anything around us) how is that different from those things just not existing?

[Delbert]

Who knows how much is out there that we don't know about, that we have never and will never see. Dark matter for instance is something that mathematically makes since but we as humans have never found a way to observe or interact with it.

Currently, I understand 95% of the universe is consists of dark matter and dark energy - which I believe are unknown (I think an American politician summed it up by saying "known unknowns").

 

I can recall once in my youth (I won't say how long ago!) and fiddling about with electronic bits and pieces, I looked at a wobbulator trace on an oscilloscope. The beat from a 5MHz marker was a double hump - as we all know. The point being that at the centre point where the wobbulator frequency was the same as the marker frequency there was no output! In other words there were two signals but they were effectively invisible. The usual explanation was that they cancel out each other (zero beat), but perhaps an alternative explanation is that at that point the two signals were in a state of superposition, as they were both there and not there at the same time.

 

As someone once said to me: there could be all sorts of stuff flying about that because it doesn't react with anything we know about, is completely undetectable and invisible.

 

Perhaps this 95% of the universe being unknown is only the start. It's probably 99.99999%!

[swansont]

Analogies have to be used with care ...

 

True, the path of a single water molecule is never partially reflected, but on the other hand, a single water molecule is also unable to interfere with its own path.

Unable? No. While water, specifically may not have been observed, atoms and molecules have been. My graduate work was in this field. I work next door to a guy who observed sodium atoms and dimers interfere. It's been observed in C-60 (buckyballs) and that was 15 years ago!

http://physicsworld.com/cws/article/news/1999/oct/15/wave-particle-duality-seen-in-carbon-60-molecules

 

To paraphrase Josh Billings, there is a problem here with the things you know that just ain't so.

 

So when the experiment is done with discrete photons / electrons over time, what is the explanation for how the photon / electron interferes with itself?

 

Both the wave explanation and the multiple path explanation, have difficulties.

 

It's the wave explanation. The wave goes through both slits.