Questions on the dual slit test that led to Many Worlds

Hello,

This concerns the test where you have a barrier with two slits cut out of it, set in front of a wall or blackboard (or something that will show hits upon it) and devices that will shoot sub-atomic particles.

My understanding is this: when particles are shot into the barrier with two slits, you get a wave-like pattern on the wall behind it. However, if you watch the barrier (or take measurements?) to see where the particles are going, the pattern on the wall behind it changes and you get two lines with no wave-like interference pattern.


I hope that I can find someone who knows the details of this test. I of course find it very hard to believe and want to find out just how deep the rabbit hole goes. I’d heard of this test and the implications long ago but somehow I missed the part about the sub-atomic particles changing their patterns from wave-like to particle-like when ‘watched’.

My first questions are the obvious ones:

Do I understand correctly that completely non-evasive and passive acts of ‘watching’ or ‘measuring’ really cause a change in how the particles acted?

Exactly how was the barrier ‘watched’ or ‘measured’?

Searches using ‘Many Worlds’ has not shed light on these questions… does the test have a name or, what search would get me to more information?

Any help will be greatly appreciated!

Regards,
Rusty

 

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Gerhard Paulus

link: http://physicsworld.com/cws/article/news/21623

 

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changes the recieving mass (elemental structure) and see if the electron pattern changes

change the color of the photon (wavelength) and see if the pattern changes

Point is, the recieving mass and the type of emitted 'x' changes the patterns

why?

seems the each structure and energy exchange has different thresholds

Hence why sending ONE (unit/particle/wave) at a time, or all at once shows the receiving mass is just as relevant and rather than rendering that each are a particle or wave, at the same time but that the exchanging mass/energy, is what is causing the pattern; each have their own thresholds.

does this make sense? (i am asking so i can understand what is inconsistent)

or better yet, who can run the experiments?

 

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I don't understand pretty much any of that post Bishadi.

As for the OP, lets begin with your questions:

"Do I understand correctly that completely non-evasive and passive acts of ‘watching’ or ‘measuring’ really cause a change in how the particles acted?"

The thing is, there is no such thing as a completely passive measurement. In order to gather information about what your photons (or electrons or whatever) are doing (i.e. about which slit they go through), you have a measuring device which interacts with them somehow. It is this interaction which screws up their nice quantum state and leaves them in a more classical particle state which you can then say went through one slit or another. The major point of the experiment is to emphasise the fact that by performing these measurements you are in fact changing the experiment, and therefore cause new results to be observed.

"Exactly how was the barrier ‘watched’ or ‘measured’?"

There are all sorts of ways to do this. One (rather contrived, but sort of useful to imagine) way is just to replace the usual screen with a sort of telescope apparatus hooked up to a photodetector, so you can count every time a photon hits the detector. Imagine the whole thing is in a super-dark room with no extra light and a source that spits out a photon only once every few seconds. You can point the telescope at one slit or the other, and if you get a blip in the detector you know the photon came through that slit. If you do this for a large number of points (i.e. to regenerate the absent screen) and for a long time (so you see lots of photons and get some good statistics) then you won't see an interference pattern, even though you have done nothing to the experiment anywhere near the slits. You can go many kilometers away if you like and have really awesome equipment (slightly impossible in practice)

A simpler method is to "tag" the photons as they go through the slits, so in principle you could check this tag to see which one they went through. For instance if you place a linear polarising filter over each slit, oriented 90 degrees to each other, then the light coming out of each slit will be oppositely polarised and you can tell which slit a photon went through from it's polarisation. The interference pattern will be wiped out, even if you don't bother to actually measure the polarisation of any of the photons.
This may be less satisifying though because it is more obvious that we did something to the photons. However, my first example was not totally unlike just blocking off the slits one at a time so you know that any photon you see came from the open slit, it was just disguised a bit by making this blockage far away from the slits, so maybe you don't like this either.

In any case you can be as clever as you like but the effect remains. One interesting note is that if you only gain partial information about which slit a photon went through then you only partially wipe out the interference pattern.

Oh, as for the many-worlds thing, that is just a way of trying to understand what is happening. We can get to that if you are ok with the rest of what I said

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sorry to read that.

can you explain why?

for clarification;

emitter= what the particle/photons/electrons come from (source)

recieving mass= the background 'x' the photons/electrons.... are ending up upon that are offering the pattern visibility

use the standard double slit (interference plate) you have at the lab.

To assist with the reasoning; it seems that when white light hits mass, a method to observe the different thresholds based on the enchange, is by the 'colors' we see (what is released back out)

does that help?

 

Bishadi: ok, i'll try, but a lot of it had to do with the fact that either the subject of some of your sentences is missing or you are using some unconventional terminology which means more or less nothing to me. If you could use more usual words it would help a lot. Admittedly learning terminology is one of the hardest parts of physics, but it will only be worse if you make up new jargon than no-one else knows.

"changes the recieving mass (elemental structure) and see if the electron pattern changes "
What changes the receiving mass, and what do you mean by receiving mass? The parentheses (elemental structure) doesn't help me understand.

"change the color of the photon (wavelength) and see if the pattern changes"
Ok this one is ok, and sure if you change the wavelength then you change the interference pattern (the spacing of the interference fringes changes)

"Point is, the recieving mass and the type of emitted 'x' changes the patterns"
Again since I don't know what you mean by receiving mass I don't know what this sentence is about. Also I don't understand what "type of emitted 'x'" refers to.

"seems the each structure and energy exchange has different thresholds"
Structure of what? Energy exchange of what?

"Hence why sending ONE (unit/particle/wave) at a time, or all at once shows the receiving mass is just as relevant and rather than rendering that each are a particle or wave, at the same time but that the exchanging mass/energy, is what is causing the pattern; each have their own thresholds."
"Receiving mass" problem again. Also what is "the exchanging mass/energy"?

Second post:
"emitter= what the particle/photons/electrons come from (source)"
Ok no problem.

"recieving mass= the background 'x' the photons/electrons.... are ending up upon that are offering the pattern visibility"
Ok thanks for defining that, you just means a screen or some other kind of detector right? If so you should just say screen, it would be less confusing.

"use the standard double slit (interference plate) you have at the lab."
Ok

"To assist with the reasoning; it seems that when white light hits mass, a method to observe the different thresholds based on the enchange, is by the 'colors' we see (what is released back out)"
You'll have to clarify what you mean by "thresholds" and "exchange".


Overall, while I understand some of your post here and there, I have pretty much zero overall comprehension of what you were suggesting. Sorry.

 

imagine what happened when someone said the earth was round, when the world of knowledge practically 'proved' that it was flat (at the time)

if i use a piece of paper as the 'mass' to show the 'pattern' and changing it to a plate of francium, would there be a difference?

so the f of the emittin photon is relevant; good start

emitters are what is used to generate a beam, (photon, electrons (cathode))

the 'x'... is you chosing which style of DSE you wish

in either approach, the frequency and receiving mass are important, would you agree?

mass; the elements of the receiving plate (piece of paper or what ever you wish to use)

exchange? You funny.. what do you think the double slit exp is doing, but sending energy thru a double slit?

that was cute

does mass (anything that has elements on the periodic chart) have a threshold of reaction (photoelectric effect)?

what are colors coming off of any structure? is there a mass/energy exchange?

what is the dbe using, light, even electrons and always mass?


ie... why you like the word screen?

hey, what do you think i say, when i read half the crap on dark junk, curving space, utter dimensions and funny quack or is it quarks (i forgot the stupid stuff)

please remove the condescending approach (it stinks)

 

Hi!

kurros, thanks for replying! It cleared a lot up for me.

Bishadi, you make no sense to me but thanks for trying.

Rusty

 

seems you like the old literature and retaining the old methodology

how about ask any with experimental capabilities to entertain using the ideas of observing the mass and find out what happens?

can't hurt a writer who is really trying to write something that is good or could it? (explain)

 

I am expecting a very neat twist from our understanding of the universe.

What I, an ordinary person who knows about the laws of physics just enough to live in them, understand from this experiment is that the material world gives us a version of its use which we can observe, measure and sense.

It is like being in a room full of people speaking various languages at the same time, you only understand one of them, and therefore your whole experience of the room is defined by the one conversation you heard or had. Or, you understand the every language but you are able to attend one conversation at a time.

Or maybe it is like a poem without an embedded meaning. We can all read the same words, but its meaning is never guaranteed. Its existence depends on our interpretation. Just like a physical reality, the sky, being something to imagine about and a challenge for humans, but the physical environment itself for the birds. For whales, sky almost doesn't exist, unless of course they are coming from the sky as in The Hitchhiker's Guide to the Galaxy.

Are we surrounded by nothing but information to decode and interpret?

If this experiment was conducted by multiple observers observing the same photons but different slits, would they get different results? Is such an experiment even possible, or meaningful?

 

Hi.

Correct.

Belief plays no role. It is what it is regardless of what anyone believes.

The particles are not changing their patterns (more on that below).

That understanding is incorrect. When any small particle (photon, electron, carbon ball, etc.) are shot towards the slits, they exist in a state called a superposition. This means they exist in different possible outcomes at the same time. If you could see those outcomes it would look like a wave spreading out from the shooting point (that wave is called a shrodinger wave).

An observer in physics is any object that can receive information. It might be a camera or it might be a slice of cheese. Different observers can receive different kinds of information. An observer that receives location information has a specific effect on superpositions. Specifically it causes the shrodinger wave to collapse into the highest probabile outcome. An observer that doesn't receive location information (like the photo sensitive tape in the back of the double slit experiment when photons are used) won't cause the shrodinger wave to collapse.

 

Hey CC, that last part is purdy

the mass (observer; receiving 'screen') is relevant

ie.... it is not so much the particle that is making a choice (between slits) but the receptor (recieving mass) is quite important to what energy is captured/exchanged (exposed at the 'time')

 

The double-slit experiment, often called "Young's experiment," is one of the most misunderstood, misquoted, and overhypothesized high school physics experiments, probably because it's one of the few quantum-effects experiments available to high school students.

The entire key to the experiment working at all is that it requires a coherent light source, whether laser or a single slit origination. It doesn't work with amorphus light. Also, it's a widespread misconception that a detector kills the interference pattern. That's patently false. Our eyes are detectors and they don't modify the interference pattern in the least.

More can be read about how and why this works, here.

 

That's a really goofy way of saying it, but yes that is correct.

 

misunderstood, misquoted and overhypothesized; yep!

light as being both particle/wave, is incorrect

and i knew that before any college, too

any medium of mass imposed must be accounted for (as a detector.......See S&G)

but what is the light hitting between your eyes and the emitter? A screen, filter, double slit? All are detectors, if that is the word you like. The instruments and all mass affected is a (per se) detector if that is the twist you are spinning up.

the point is the 'mass' imposed can affect the pattern or purely, send that one (per se) photon at a time, same pattern as with the whole barage, but if in between the beginning and ending, you change the receiving mass, watch the pattern change


that is my point; the mass being imposed too is relevant (what is color?)

another way to see this is put a divider on the reverse side of the double slit perpendicular to the double slit, note the difference in a vacuum.

i have no problem with sharing ways of observing and the experiments to do so.

the Young Exp or Double slit or how ever you wish to call it, has been a curse or blinder to physics for a long long time

look up the terms dichroism and dispersion, then go thru snell's law

the mass is relevant (ie.... how did you think colors work?)

 

not many more goofy than an i be

 

It isn't the detection of the interference pattern that is at stake, it is the detection of the photons/electrons before the interference pattern is made, the interference pattern itself is weird if you send only one electron/photon at a time. What does it have to interfer with?