- Murshid Salam
- Gurgaon, Haryana, India
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Program Controller, Ericsson India Global Services Pvt. Ltd.
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In double slit experiment of Thomas Young, why do electrons (particles) behave like waves when we aren't observing them?
In double slit experiment of Thomas Young, electrons (particle) behaves like a particle when they are under observation. But how they suddenly behave like a wave when we do not observe them.
Topics:
quantum superposition
Marius Moe
Here is an article about some of the most recent findings during an experiment in which one got to see which slit the particle went through, without interfering with the wave-like properties of the particle.
Justen Robertson 50+
Much later, others discovered that even if you sent through only *one* photon (or electron) at a time, you'd still build up an interference pattern, meaning that during transmission even single particles were behaving as a wave, rather than the wave being a result of the aggregate of many particles interacting as with, say, molecules of water becoming waves in aggregate.
More interesting than that, if the experiment put particle detectors at the slits themselves, to see which slit the particle went through, it worked - that is, it was also proven that there was a discrete particle that traveled only through one slit or the other, not both. So it turns out they're both waves and particles, in some sense.
Basically, depending on how you set up the experiment, you can prove that photons (and other subatomic particles) are waves *or* particles, and that the two are not mutually exclusive, which is counter-intuitive in classical physics, but has nothing whatsoever to do with intelligent observers shaping the nature of the universe.
The conflation of the Heisenberg Uncertainty Principle (quantum mechanics), the Observer Effect (anthropology), and wave/particle duality, and how these things supposedly amount to "the nature of reality is dictated by perception" is a product of pseudoscientific mystics, not actual scientific evidence. Experiments purporting to support this notion have been repeatedly debunked. Don't let these people mislead you. The price of knowledge is eternal skepticism :)
paul Ashton
Justen Robertson 50+
Jen Doty
paul Ashton
Jen Doty
natasha nikulina 50+
You've just verbalised/materialised the picture i have in my mind :)
Thank you !
John Allyn
The fact is a photon alternates between being a wave and a particle so depending on how the experiment is designed it seems to be one or the other........."But an experiment performed in 1987[23] produced results that demonstrated that information could be obtained regarding which path a particle had taken, without destroying the interference altogether. This showed the effect of measurements that disturbed the particles in transit to a lesser degree and thereby influenced the interference pattern only to a comparable extent. And in 2012, researchers finally succeeded in correctly identifying the path each particle had taken without any adverse effects at all on the interference pattern generated by the particles."(WikipediA)
The only correction I would make to this is in the last word, 'particles". It should say the particles associated wave. Waves create interference patterns.
What is not understood is that the photon consists of two standing waves of force, one being the expansive electro force and the other being the contractive magnetic force. These waves of force cross each other at ninety degree angles. When they cross each other on the vertical axis, they merge and become an electromagnetic particle. The particle vanishes when the forces separate in their continuation as standing waves of force.
This leads me to state that physics because of its insistence that metaphysics are not to be considered, they had to make the force of gravity a by product of mass. The fact is gravity is a metaphysical force which creates mater by causing the most basic form of mater, the photon to stabilize as a particle. Such photon particles are the building blocks out of which all other particles are constructed.
William Humphrey
Marius Moe
natasha nikulina 50+
Marius Moe
The double-slit experiment have seemed that way for many who doesn't understand what the detectors do, and how they interfere with particles by detecting them.
To scale, it has been kind of like hitting a marble (1) with another marble (2) in a dark room to find the position of marble (1).
Earlier this year, with a more advanced detecting technique, it became possible to observe which slit the foton went through without interfering with the wave-like property of the particle itself, putting to rest filosophical musings as to whether or not light particles change their behavior "if they know they're being watched".
It's the mechanics of the experiment that hasn't been advanced enough, yet. Not a form of consciousness.
I have no aversion to philosophical musings or even fringe experiments that examines our reality and whether or not there are things that we operate under the impression of, that in reality are false, but blanket statements that goes directly against evidence is hard for me to swallow.
When someone makes a statement about fundamental forces in the universe, it would be nice if they themselves could attempt to back it up with evidence, instead of me finding ways to do their experiments for them.
natasha nikulina 50+
It's catch 22 . : ) If the experiment is not observed, we have no results of of the experiment .
Thanks for responding !
walter crockett
Henk Mulder 10+
What we call particles or waves are our images of these things. They are what we think they are because we "see" them in our (conscious) brain.
It is not hard to understand that what we see when we look at these particle/waves is not the same as when we don't look at them and they are somewhere in this information-energy ether out there.
What is surprising is that we have not managed to create a common conscious image of this particle-wave thing that is coherent between what it is and what we make of it.
metin okucu
Barry Palmer 50+
And that is all it is.
Dejay Davison
I was once walking home questioning the same thing, but I thought...
"What IF someone completely believed they could alter how these 'particles' acted simply by thinking?"
Would, or could that change how they acted?
I found it strange that when we observed, they acted like we expected them to, BUT is that because we 'expected' them to? And our consciousness had some effect on how they acted?
Who is to say humans brainwaves don't have unknown 'powers', it's a controversial subject I know, but the evidence behind a 'sixth sense' is overwhelming in many fields of study.
Just a thought.
paul Ashton
Dejay Davison
paul Ashton
Some mind blowing stuff for you viewing and reading pleasure:
BBC 4 - Dangerous knowledge (on YouTube)
The Atom
M- theory
PBS Nova (on you tube)
-Hunting the Hidden Dimension (fractles)
-The Elegant Universe (series of 3 or four shows related to the bbc material but older-optional but simply explanitory)
(all of the below available on YouTube)
(hokey but thought provoking)
Holographic Universe (Part 1)
Introduction and Illustration on the Holographic Principle
-explains the role of black holes and potential information storage
Quantum Consciousness, Quantum Mind STUART HAMEROFF (P.1)
(also check out his website by the same title for a little light reading)
Check out on Ted.com -
Lucianne Walkowicz: Finding planets around other stars
Aaron O'Connell: Making sense of a visible quantum object
Andrea Ghez: The hunt for a supermassive black hole
Sean Carroll: Distant time and the hint of a multiverse
http://feeds.gawker.com/~r/io9/vip/~3/peGfJikxy74/the-human-mind-may-secretly-follow-the-laws-of-quantum-mechanics
http://www.popsci.com/technology/article/2011-09/two-key-computing-advances-bring-quantum-computers-closer-reality
Dejay Davison
Barry Palmer 50+
http://noosphere.princeton.edu/
Michael McLoughlin
That is to say, no matter how many people are thinking or how hard they think, physics goes on, entirely undisturbed.
They idea that anyone's thoughts effect the outcome of the double slit experiment (or any other experiment or physical event) is an unfortunate misunderstanding that results from the use of the word 'observer'.
When physicists say that they 'observe' a particle in the double slit experiment they do not literally mean that someone actually looked at it, or thought about its location during experiment. In fact, there is no 'observer' at all in the sense of the term where observer means conscious agent (like a scientist, for example). Instead, the 'observer' is actually a detector that is part of the experimental apparatus. In order to make an observation though, the detector must interact with the particle as it travels along. Imagine being blind; the only way to 'observe' the location of, say, the remote control would be to touch it to discover its location. The touching, crucially, is the observation without which nothing could be definitively known. In the same way, any detector must 'touch' the particle to find out something about it: like how fast it's moving or where it is or what slit it went through. Crucially, however, by doing this, by 'touching' or 'observing' the particle, the particle's state is irrevocably changed (like leaving fingerprints on the remote) thereby altering the outcome of the experiment.
While admittedly bizarre, the way in which these experiments play out, both observed and otherwise, is completely and thoroughly explained by quantum mechanics.
Non-intuitive and difficult to understand? Yes. Sixth sense? Not so much.
This is rather interesting if you're interested: http://en.wikipedia.org/wiki/Double-slit_experiment
Read it carefully.
Dejay Davison
But, in my defense:
I, nor anyone alive fully understands the nature of consciousness, and it's spectrum of capabilities.
Michael McLoughlin
And yeah! Definitely.
Consciousness is rather bizarre and no one's figured it out completely. Yet!
But when it's all said and done, I'd place my bets on consciousness being an entirely physical phenomenon. I feel that a lot of people may find that idea rather disenchanting but I think it's lovely, imagining everything that I identify as 'me' as just a curious consequence of the very universe I'm a part of.
paul Ashton
Etienne Lamy
Take photons, and their polarity property, for example. Photons can have vertical, and horizontal polarity. When measuring it, the result can only be positive or negative, although the initial state is a combination of both. Indeed, measuring a result changes the behaviour of a particle. But when you take photons with vertical polarity fixed, the horizontal polarity becomes undefined.
According to Heinsenberg's uncertainty principle, you can't know as precisely as you want, the position and the quantity of movement of a particle. This means that when you "observe" the position of a particle, you change its probability field, and increase the uncertainty on its speed.
Therefore, you cannot keep the wave properties of matter while "observing" it.
Barry Palmer 50+
David Hamilton 50+
Marius Moe
As an analogy, imagine trying to find the position of a marble in a dark room, by hitting it with another marble. It's kind of hard to do without interfering with the marble that you hit.
Earlier this year, researchers managed to do the experiment using more advanced technology and tools, so they could observe which slit it went through without interfering with the wave-like properties of the particle. Nothing about our eyes, just a huge refinement of the detection system in the test itself.
Here's an article that talks a little about it:
http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/
Erik Dahlberg
Carl Shaw
I think we are looking at two problems: 1/light is neither wave nor particle. 2/ There is also a significant/pivotal part played by consciousness in all this.
Barry Palmer 50+
All that being said, I could be wrong, and consciousness could be playing a role. But that cannot be considered a fact until we understand how consciousness is involved. Until then, it is just one possibility. Considering the history of science, I think it is very improbable. The universe does not need observers to function. Subatomic particles don't care about us.
I admit that I have only a layman's understanding of quantum mechanics. My strong opinions stem from a good grasp of logic and knowledge of the history of science. Many scientists have made the same kinds of mistakes that I see being made again and again. I recently saw a documentary in which a few rogue physicists are also looking for alternative explanations.
Carl Shaw
Physics adopts the philosophical approach that all comes from the material. This is a severe, unnecessary and arbitrary restriction in the search for knowledge. Adopting this it finds the answer it wants (i.e. all stems from a big-bang) even if to do this it needs to invent vast quantities of imaginary dark matter and energy to support this idea.
If science was free to discover our origins without any philosophical assumptions restricting the answer, it might find a different origin. Perhaps consciousness is our origin?
If a hammer is the tool available then every problem is a nail.
Marius Moe
http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/
Carl Shaw
The article you reference raised my attention. I found c copy of the original paper at http://www.pnas.org/content/early/2012/05/23/1201271109 .
It appears the article isn't strictly representative of the experiment that was carried out. The experiment is an amalgamation of TWO experiments. The particle which interferes is a particle from experiment 1, whereas the particle which is detected as going through a particular slit is from a second experiment 2.
In conclusion the authors write:
"However, the EPR discussion (3) or the delayed-choice experiment (22) have taught
us that quantum objects do not have a reality independent of a
measurement as summarized (29) by the phrase “one cannot consider
quantum properties as being ’real,’ in the sense of ’objective
reality.’”
John A. Wheeler (3), paraphrasing Bohr, expressed this fact
most vividly by saying “No elementary quantum phenomenon is
a phenomenon until it is a recorded phenomenon brought to a
close by an irreversible act of amplification.”
In this sense our experiment can also be interpreted as another
confirmation of the nonobjectifiability of quantum mechanics or,
as stated by Torny Segerstedt, “Reality is theory.” "
A similar recent experiment (http://arxiv.org/abs/quant-ph/9903047) uses similar materials but a different experimental arrangement such that THE SAME PHOTON can be measured in 1 single experiment. Availability of the results of the experiment (conscious observer) DID still seem to have significance.
Kevin Jacobson
Gail . 50+
The experiement suggests that particles ARE waves as well as particles. Each particle exists wtih its own waves of probability. I prefer to think of the "interference pattern" as something more personally meaningful. I see the bars of the interference pattern as being bars of probability - with the brightest bar being the strongest possibility given the circumstances, and the lighter bars being less and less probable. In other words, each bar represents a probable future, each of which is fulfilled in its own dimension - like in the Schroedinger's cat experiment, but not as vague. (Split Universe Theory - which I agree with)
There are many possible actions that you can take NOW. The strongest probability is that you will continue reading this. That makes your intent the thing that collapsed the wave form. - thus you create your reality. Perhaps the least probability is that you will now throw your computer across the room & smash it. But that potential reality exists in its own right - in its own dimension.
Bottom line: Reality is not 1-dimensional. Thoughts are electromagnetic energy and very powerful. They extend beyond the body & form relationships with the energies of other beings - of which we are a part and which we create. (multidimensional) Taking this to the farthest point, it suggests that we are God(s) because thru thought, we choose our futures using mind.
David Hamilton 50+
Physicists are rallying around this idea for 2 reason in my mind. Quantum physics is in such poorly understood infancy, that people will rally behind just about any new idea now... and, ever since the big bang theory, physicists and buddhists are hoping that science is going to explain purpose to human life... I think that's a fools errand. I love foolishness though... So there's the rub.
Justen Robertson 50+
One can ask many questions and make many assertions about the nature of reality, or of consciousness and intelligence. Finding the true answers, and proving the assertions, is much more difficult and complicated.
Johnathan Quenichet
Ever play Doom and do the cheat where you walk through walls?
You walk through a wall and a monster is waiting there, dormant, but springs to life when you move through the wall.
Now, was that monster there before you walked through the wall? Yes, stored as data, waiting for your approach to become visible and spring to life, but certainly not observable in any sense. Something to think about, maybe not very hard, but definitely something to noodle.
s greco
There's the "observation makes the wave function collapse" camp and the "the detector causes interference that alters the outcome" camp. The truth is, there's no solid evidence either way. Its one of the most curious and perplexing puzzles in physics.
Given what we know about electrons and their penchant for being in multiple places at the same time, I personally find the "the detector causes interference that alters the outcome" to be too closed minded.
Who knows? Maybe when we do find the answer it will trump any of its predecessors.
peter lindsay 30+
s greco
'Steinberg stresses that his group's work does not challenge the uncertainty principle, pointing out that the results could, in principle, be predicted with standard quantum mechanics. But, he says, "it is not necessary to interpret the uncertainty principle as rigidly as we are often taught to do", arguing that other interpretations of quantum mechanics, such as the pilot-wave theory, might "help us to think in new ways".
David Deutsch of the University of Oxford, UK, is not convinced that the experiment has told us anything new about how the universe works. He says that although "it's quite cool to see strange predictions verified", the results could have been obtained simply by "calculating them using a computer and the equations of quantum mechanics".
Carl Shaw
In around the year 2000 several physicists put together a Young's slit experiment called a “Delayed Choice Quantum Eraser” which positively excludes any other possibility than it being the actual observation by a conscious observer which causes “wave function collapse”. The experiment was conducted by Y.H. Shiti, Ho Kim, Ri Yu, S.P. Kulick, Marlan O-Scully, details may be looked up on the internet.
In all these experiments there is the common ground of probability waves and wave-function collapse. This interpretation of reality is not necessary, another interpretation will emerge which will explain all experiments to date without the need of recourse to statistics. This is the subject of my theory yet to be published.
Nevertheless the significance of consciousness remains. There is a definite and proven connection between quantum experiments and conscious observation of them.
Barry Palmer 50+
http://arxiv.org/pdf/quant-ph/9903047v1.pdf
The word "conscious" does not appear in the paper.
The experiment uses detectors which gather data and store that data. That stored data would be the same whether a conscious being looked at it or not. Your conclusions are NOT supported by this experiment.
----------------------
Addition: Carl, since your reply has no reply button, I reply here.
I stand by my original assertion, it is still just an arrangement of detectors and there is absolutely no 'proof' that consciousness is involved. That is an interpretation, not an observation. And that is why the conclusion of the paper does not make that conclusion.
Carl Shaw
You are right that the word “conscious” does not appear in the paper. There is a history to the Young's slit experiment which I understand as follows:
1. Young conducts the classical light wave projecting through two slits onto a screen experiment. The screen displays an interference pattern and hence proves that light is a wave.
2. Through the photoelectric effect Einstein discovers that light has a discrete property and therefore must be a particle.
3. Discrete photons are then projected through the slits to discover which slit they went through. Yet it is still discovered that the individual photons interfere with themselves and produce a diffraction pattern on the screen.
4. In an attempt to find out which slit each photon goes through, detectors are placed AT THE SLITS. The results on the detector screen show a discrete pattern thus indicating a particulate nature of light which appears when 'which slit' information is detected.
Thus it seemed that the act of detection had 'forced' the photon to decide which particular slit it was going to pass through. This experiment was the juncture at which Schrodinger had his famous “Schrodinger's cat” thought experiment. It seemed like the observation of the results of the experiment had collapsed the probability wave function and made the light particulate.
Since this experiment there have been many who have thought that it was not CONSCIOUS observation of the photons at the slits which brought about wave-function collapse but it was mechanical or energetic contact with the wave at the slits which brought it about.
It has been impossible to definitively prove whether it was mechanical or conscious observation until this elegant experiment was devised and conducted.
The question to be answered by this experiment is as follows:
Does the availability of 'which slit' information to the observer of the results of the experiment cause the light to become particulate?
Carl Shaw
In order to conduct the experiment no detection is made at the slits. Photons are split into entangled pairs AFTER the slits. One of these pairs is sent to detector 0. Detector 0 therefore provides positive detection for every photon through both slits, but it provides NO information about which slit it passed through.
Through the use of 50% transmission/reflection mirrors, length of transmission paths, subsequent detectors and coincidence of detection circuitry, the paths of the other entangled halves of the photons is traced into one of four possibilities:
1. A photon is detected having gone through through either slit A or B.
2. A photon is detected having gone through slit A and not through B
3. A photon is detected having gone through B and not through A
4. A photon is detected having gone through either A or B, but the equipment set-up erased the information subsequent to obtaining it. Thus although having been made energetically this information is NOT AVAILABLE to the observer of the experiment.
It is the logical detection path 4 which is crucial to the experiment. The set-up is devised such that 1 of two types of information can be retrieved from the experiment: 1. A photon passed through slit A or B and was detected as having passed through, or a photon passed through, was detected as having passed through, but information as to the specific slit it passed through was erased.
The results clearly show that WHEN the 'which-slit' information is available to the experimental conductor - the (fig 5) photons exhibit particle like behaviour. When the information is collected BUT SUBSEQUENTLY destroyed (randomly by the clever use of 50% mirrors) (figs 3 & 4) then the photons exhibit wave-like interference patterns.
Therefore I think that the experiment clearly shows that it is ONLY WHEN information is made available to a CONSCIOUS OBSERVER that the light becomes a particle.
Carl Shaw
Barry Palmer 50+
The experiment you reference gathers and deletes "information". Perhaps what the paper refers to as "information" is more than just something that we perceive. Perhaps this "information" has physical effects; can anyone definitively rule this out?. In science there is no agreed upon definition of "information" and no one can explain to me the basic nature and structure of information. So I can conclude that when this paper refers to "information" they do not completely understand "information" and what effects it might or might not have.
Stephen Hawking once proposed a scenario where black holes could destroy information, and apparently there is a law of science which says this is impossible. Apparently physicists have equations dealing with information. I have no idea if the word "information" as used in the experiment is the same kind of "information" that they have in their equations.
There is no logical or other explicit or implicit connection that permits the conclusion that physical effects caused by gathering or deleting information involves consciousness. Many physicists refer to these results as a mystery, because that is exactly what they are.
Marius Moe
The method was refined earlier this year, and photons could be detected without interfering with their wave-like properties. Refinement of tools, no consciousness involved.
http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/
Carl Shaw
The article you refer to is interesting, but it doesn't seem to accurately reflect the experiment as conducted. I found the original document on which the article was based here:
http://www.pnas.org/content/early/2012/05/23/1201271109.full.pdf+html
Their experiment is actually two experiments (lets call them exp A and B). In experiment A the particle is tested and detected as a particle. In experiment B it is passed through the slits, interferes, and performs as a wave. Since it is two different particles they are looking at, they do not even attempt to address the issue of "observation of the results affecting the outcome of the experiment". They understand this and in conclusion in their paper they state:
" However, the EPR
discussion (3) or the delayed-choice experiment (22) have taught us that quantum objects do not have a reality independent of a measurement as summarized (29) by the phrase “one cannot consider quantum properties as being ’real,’ in the sense of ’objective
reality.’”
John A. Wheeler (3), paraphrasing Bohr, expressed this fact most vividly by saying “No elementary quantum phenomenon is a phenomenon until it is a recorded phenomenon brought to a close by an irreversible act of amplification.” In this sense our experiment can also be interpreted as another confirmation of the nonobjectifiability of quantum mechanics or, as stated by Torny Segerstedt, “Reality is theory.” "
There is another recently conducted test using the same/similar materials in the detection process (http://arxiv.org/abs/quant-ph/9903047). The arrangement and protocol of this one is such that ONLY the same particle is tested. The results confirm & reinforce the currently held understanding that availability of the results of the experiment affect its outcome.
peter lindsay 30+
http://arstechnica.com/science/2012/05/disentangling-the-wave-particle-duality-in-the-double-slit-experiment/
Justen Robertson 50+
Edit: clarification: you want to type in this: "λ" (obviously without the quotes)
peter lindsay 30+
Justen Robertson 50+
http://www.w3schools.com/html/html_entities.asp
http://www.w3schools.com/tags/ref_entities.asp
http://www.w3schools.com/tags/ref_symbols.asp
peter lindsay 30+
Justen Robertson 50+
Stewart Gault 30+
And the reason why the pattern changes when we observe it is subtle. All videos I've seen make it sound like just looking at an electron makes it change course, but it's not entirely true. As Hawking outlined in his book (to my relief) it's what's required to "see" something that changes the electron's course. To see things photons need to be reflected by an object. And when scientists bounce photons off the electrons it changes their energy, momentum and position and somehow ruins their superposition. They then form a different pattern. Hawking's example, I think, was when a football rolls along the ground imagine throwing balls at it from the side, you're going to change how the football behaves.
So electron left by itself= self interferes and forms a wave pattern because of superposition
When observed= photons ruin superposition in a sense and determines which path the electron takes.
Christopher Leveck
Stewart Gault 30+
I remember being totally perplexed by the idea of a self aware electron and then Hawking's book The Grand Design cleared that up for me.
Fritzie Reisner 100+
Murshid Salam
In this video experiment is done with electrons. that is why raised this question.
Please see this video.
Fritzie Reisner 100+
Stewart Gault 30+
Gail . 50+