Double Slit Experiment

[idav]

The experiment would have been pointless with an interfering detector. Those scientists I think would have seen such an obvious flaw and the fame of the experiment would never have gotten out of the starting block.

Yes scientists have noticed those obvious flaws which is why they have been striving for and succeeded in actually observing the phenomenon without messing with its state.

 

[GURSIKH]

In short: When scientists (instruments of course) watch a particle pass through two slits, the particle goes through one slit or the other. If a person doesn't watch it, it acts like a wave and can go through both slits simultaneously.

How is this explained by physicists?

(I did not see this subject through search, although I might have missed it.)

Atanu , can you provide link where it says particle (photon) became wave with respect to our observation .
as far i know double slit experiment is explained by fully "Quantum field theory " which consider photon as particle all the time (never wave ).photon either behave as particle in any experiment or it behaves as a wave in experiment ,its not like sometimes it behaves as particle and other times it behave s as wave in same experiment .

 

[George-ananda]

Yes scientists have noticed those obvious flaws

I have not heard that the double-slit experiment has been discredited by flaws.

 

[idav]

I have not heard that the double-slit experiment has been discredited by flaws.

No everytime we do the experiment we get the results we want. That isnt really a problem but there a million things to check and different ways of approaching the questions we have. Every experiment answers one thing or another and it is the intepretation, the how that differs. Also as we advance in technology we get passed barriers that plague us. How is a oarticle in more than one place, could be entanglement, multi world theory, maybe the photon just goes that fast, the speed of light. Other theories eliminate ideas like the spooky actions at a distance elimenates thr thought of its speed being the factor. So we solve more problems and the intepretation goes into sharper focus.

 

[George-ananda]

No everytime we do the experiment we get the results we want. That isnt really a problem but there a million things to check and different ways of approaching the questions we have. Every experiment answers one thing or another and it is the intepretation, the how that differs. Also as we advance in technology we get passed barriers that plague us. How is a oarticle in more than one place, could be entanglement, multi world theory, maybe the photon just goes that fast, the speed of light. Other theories eliminate ideas like the spooky actions at a distance elimenates thr thought of its speed being the factor. So we solve more problems and the intepretation goes into sharper focus.

That's all fine but it doesn't address my quote: the double-slit experiment has not been discredited for flaws (with detectors interacting).

 

[fantome profane]

Here's a short article describing the double-slit experiment:

-- Quantum Theory Demonstrated: Observation Affects Reality
- REHOVOT, Israel, February 26, 1998--One of the most bizarre premises of quantum theory, which has long fascinated philosophers and physicists alike, states that by the very act of watching, the observer affects the observed reality.
In a study reported in the February 26 issue of Nature (Vol. 391, pp. 871-874), researchers at the Weizmann Institute of Science have now conducted a highly controlled experiment demonstrating how a beam of electrons is affected by the act of being observed. The experiment revealed that the greater the amount of "watching," the greater the observer's influence on what actually takes place.

The research team headed by Prof. Mordehai Heiblum, included Ph.D. student Eyal Buks, Dr. Ralph Schuster, Dr. Diana Mahalu and Dr. Vladimir Umansky. The scientists, members of the Condensed Matter Physics Department, work at the Institute's Joseph H. and Belle R. Braun Center for Submicron Research.

When a quantum "observer" is watching Quantum mechanics states that particles can also behave as waves. This can be true for electrons at the submicron level, i.e., at distances measuring less than one micron, or one thousandth of a millimeter. When behaving as waves, they can simultaneously pass through several openings in a barrier and then meet again at the other side of the barrier. This "meeting" is known as interference.

Strange as it may sound, interference can only occur when no one is watching. Once an observer begins to watch the particles going through the openings, the picture changes dramatically: if a particle can be seen going through one opening, then it's clear it didn't go through another. In other words, when under observation, electrons are being "forced" to behave like particles and not like waves. Thus the mere act of observation affects the experimental findings.

To demonstrate this, Weizmann Institute researchers built a tiny device measuring less than one micron in size, which had a barrier with two openings. They then sent a current of electrons towards the barrier. The "observer" in this experiment wasn't human. Institute scientists used for this purpose a tiny but sophisticated electronic detector that can spot passing electrons. The quantum "observer's" capacity to detect electrons could be altered by changing its electrical conductivity, or the strength of the current passing through it.

Apart from "observing," or detecting, the electrons, the detector had no effect on the current. Yet the scientists found that the very presence of the detector-"observer" near one of the openings caused changes in the interference pattern of the electron waves passing through the openings of the barrier. In fact, this effect was dependent on the "amount" of the observation: when the "observer's" capacity to detect electrons increased, in other words, when the level of the observation went up, the interference weakened; in contrast, when its capacity to detect electrons was reduced, in other words, when the observation slackened, the interference increased.

Thus, by controlling the properties of the quantum observer the scientists managed to control the extent of its influence on the electrons' behavior. The theoretical basis for this phenomenon was developed several years ago by a number of physicists, including Dr. Adi Stern and Prof. Yoseph Imry of the Weizmann Institute of Science, together with Prof. Yakir Aharonov of Tel Aviv University. The new experimental work was initiated following discussions with Weizmann Institute's Prof. Shmuel Gurvitz, and its results have already attracted the interest of theoretical physicists around the world and are being studied, among others, by Prof. Yehoshua Levinson of the Weizmann Institute.


The detector was a passive device if you note.

Can you show me where it says the detector was a passive device?

More to the point, could you explain how a passive device works?

I still maintain that passive observation is absolutely impossible.

 

[George-ananda]

Can you show me where it says the detector was a passive device?

More to the point, could you explain how a passive device works?

I still maintain that passive observation is absolutely impossible.

First sentence of paragraph 6 reads:

Apart from "observing," or detecting, the electrons, the detector had no effect on the current.

 

[George-ananda]

More to the point, could you explain how a passive device works?

Just like the human eye. We don't use echo-location or sonar like bats

 

[idav]

Just like the human eye. We don't use echo-location or sonar like bats

The steps we know about in seeing an object involve physical interactions like a camera or mic picking up on various frequencies.

 

[George-ananda]

The steps we know about in seeing an object involve physical interactions like a camera or mic picking up on various frequencies.

EXACTLY.....they only are for 'picking up' things in the environment. Surely you must understand.

When we look at the moon, our eyes are affected by the moon, but our eyes do not affect the moon.

 

[atanu]

I still maintain that passive observation is absolutely impossible.

I think that is an important statement.

 

[atanu]

Well, that is a bit different. Usually you have this stroboscopic illusion when you watch a movie of a car moving. It is due to the discretization of the image in different photograms. You see one photogram and the next is when the wheel has performed almost, but not quite, a full round. You would have the impression that the movement is reversed.

The Everett interprtation of quantum mechanics is quite popular amongs scientists. The idea is that when we make an observation, we do not affect the physics whatsoever. That would introduce absurdities like consciousness affecting reality and, even worse, an asymmetry in the laws of nature.

The idea is: when we don't observe, the photon is in a superposition of states (slit1 and slit2). When we observe, it is us that go in a superposition of states (slit1 observed, slit2 observed).

So, if I observe the photon going through slit1, there will be another viole who observed it going through slit2. The wavelike character of the photon has been inherited by viole, who is also a wave now.

Viole and the observed photon become entangled, so to speak, and they all run in parallel in a superposition of states, one for each possible entanglement. That happens also in an interaction particle/particle (and particles do not have consciousness, I assume): when they interact they may become entangled. The same happens in an interaction particle/observer.

Nothing weird, lol.

Ciao

- viole

I am bringing it back for Idav and others who hold that there is nothing weird going on.


One can explain away the observer effect by considering the observer as part of the system, yet the outcome is not simple. Just check deeply.

 

[atanu]

Atanu , can you provide link where it says particle (photon) became wave with respect to our observation .
as far i know double slit experiment is explained by fully "Quantum field theory " which consider photon as particle all the time (never wave ).photon either behave as particle in any experiment or it behaves as a wave in experiment ,its not like sometimes it behaves as particle and other times it behave s as wave in same experiment .

Hello Gursikh

There are, in the begininning of this thread, a few links to videos that explain the explain the experiment.

 

[fantome profane]

EXACTLY.....they only are for 'picking up' things in the environment. Surely you must understand.

When we look at the moon, our eyes are affected by the moon, but our eyes do not affect the moon.

The microphone that picks up sound waves actually disrupts those sound waves. And the photons that hit the moon actually have an impact on the moon. In the macro world we live in these effects are very tiny. In the world of sub-atomic particles the effect is immense.

There is no such thing as passive observation.

 

[George-ananda]

And the photons that hit the moon actually have an impact on the moon.

Of course BUT those photons have the same impact on the moon whether or not I observe from earth. The observer changes nothing.

 

[idav]

Of course BUT those photons have the same impact on the moon whether or not I observe from earth. The observer changes nothing.

Right my contention is that human consciosness creates reality. The moon is stuck in the same entanglement we are in.

 

[GURSIKH]

Hello Gursikh

There are, in the begininning of this thread, a few links to videos that explain the explain the experiment.

kindly , be bit more precise

 

[atanu]

kindly , be bit more precise

There are two video links in the following post:

http://www.religiousforums.com/forum/3713503-post12.html

I hope that the videos will help to clarify.

 

[atanu]

Right my contention is that human consciosness creates reality. The moon is stuck in the same entanglement we are in.

I say that 'created' is not the reality. Reality is that which creates.

 

[atanu]

Well, there are opinions on opinions.

For a start, how is the existence of the other universes to be tested? To be sure, all cosmologists accept that there are some regions of the universe that lie beyond the reach of our telescopes, but somewhere on the slippery slope between that and the idea that there are an infinite number of universes, credibility reaches a limit. As one slips down that slope, more and more must be accepted on faith, and less and less is open to scientific verification. Extreme multiverse explanations are therefore reminiscent of theological discussions. Indeed, invoking an infinity of unseen universes to explain the unusual features of the one we do see is just as ad hoc as invoking an unseen Creator. The multiverse theory may be dressed up in scientific language, but in essence it requires the same leap of faith.

Paul Davies, A Brief History of the Multiverse