The Most Beautiful Experiment

Quantum physics informs us that a system exists in superposition — that is, in all possible states — until we observe that it is only in one specific state.

According to a 2002 poll of Physics World readers, the “most beautiful experiment” in physics is one that simply and elegantly demonstrates how observation affects quantum systems: The double slit experiment. The double slit sets aside causality, determinism, and the notion that reality is “out there” as it blurs the line between the observer and the system being observed.

In the double slit experiment, a series of single photons (light particles) are fired at a solid plate that has two slits. On the other side of the solid plate, a photographic plate is set up to record what comes through those slits.


The question: What will we see on the photographic plate?

The answer: If one neglects to observe which slit a photon passes through, it appears to interfere with itself, suggesting that it behaves as a wave by traveling through both slits at once. But, if one chooses to observe the slits, the interference pattern disappears, and each photon travels through only one of the slits.

The formation of the interference pattern requires the existence of two slits… But how can a single photon pass through two slits simultaneously? At that point, we are forced to consider each photon as a wave that travels through both slits… Or we have to think of the photon as splitting and going through each slit separately — and wondering how the photon “knows” a pair of slits is coming.

The only solution is to abandon the idea of a photon — or any other quantum system — as having a location in spacetime until it is observed.


97 Responses to “The Most Beautiful Experiment”

  1. I am trying to figure out the truth about the current understanding of quantum physics. From my understanding nothing can be measured without at some level interfering with what is being measured. Do you know the details of how they measured which slit the photon goes through and how it may interfere with the behavior of the photon? Thanks.

    • Re: Details: There have been numerous double-slit experiments carried out since the early nineteenth century — using light, neutrons, atoms, electrons, and even molecules as large as carbon-60 and carbon-70. Some were measured by human observers, and some recorded by detectors which were then observed by human observers — who, I might add, also conceived and built the detectors specifically for the purpose of later observation. So, while a real-time human observer is not needed for the experiment itself, it nevertheless holds that a detector’s results are observed, at some point, by a human. And so the effect occurs.

      In QT circles, this phenomenon is known as the “measurement problem.” It’s also an ontological dilemma for many people. To my thinking, it seems a simple enough fact that everything we know about anything in this universe is a direct result of observation, for how could we “know” anything otherwise? From that perspective, it also makes sense that an observer (like, for instance, a human) will have an effect on any observable with which it interacts (like, for instance, a photon).

      To quote one of my favorite physicists, Erwin Schrodinger, “Subject and object are only one. The barrier between them cannot be said to have broken down as a result of recent experience in the physical sciences, for this barrier does not exist.”

  2. If you’d like to conduct the original experiment yourself, check out

  3. what about the reductionist approach? suppose I eliminate one intelligent being after another…when I finally eliminate myself, will the universe ‘as we know it’ still exist? will the bullet which blew my brain, continue to follow a newtonian trajectory? I think yes.

  4. You’re using reductionism to argue in favor of pluralism — neither of which can be reconciled with quantum theory. Although the conclusions you have drawn from your model are (superficially) intuitive, it is through deeper analysis that principles such as entanglement and complementarity have been uncovered — and, thus, the case for emergence/synergy successfully established.

    Even macro-cosmically speaking (in this case, bullets and brain spatter), reductionism does not work within the ontological framework of QT, as uncertainties at the micro level are increased.

    To quote Ernest Gellner, “Reductionism is rooted not in the nature of things, but in our ideal of explanation.”

  5. I had trouble understanding this experiment at first, but on YouTube there is a cartoon like video from Fred A Wolf (Dr Quantum) than explained it perfectly. It was the understanding of this experiment and how consciousness plays such an active role in our realities that has me so turned on to QP. Love the site!

  6. Thanks for your comment. If you are interested, I have a YouTube channel dedicated to exploring the Observer Effect, featuring over 230 videos at the present time (and I am always adding more!).

    You can visit my channel at

  7. Has anyone that you know of conducted the experiment to alter the observed effect with intent, rather than observing, actually manipulating the outcome by thought?

    I was a chiropractor for horses, and on the journey of life figured out how to adjust, or heal by thought.

    I realized that some of the misalignments of certain joints, particularly the Jaw, were being caused by my own observations, which eventually turned into a very common malady.

    When I realized that I had created this outcome, I then changed my thought about this particular mis-alignment, afterwards, it has been a rare ocourence.

    I guess now I would be considered a non observer to this particular joint.

    We are given such a gift, so simple, that it seems phenomenally difficult.

    My little story here is what prompts my question about the experiment.

    Thank you, Love your work here and look forward to watching your youtube videos

  8. What could be the possible implication of this in ‘real life’ i.e in all practicality?

  9. It is hard for me to understand the implication of observation affecting reality. How is it that observation is defined? Is it to be able to perceive the outcome through our senses? What about when the subject in question (the photon) cannot be detected by our fundamental senses? Well, we can put a camera by the slit and record and data to extend our perception. But what if we put the camera there, but delete the data without looking at it? Have we still observed it?
    If we were to do the same experiment with small marbles, why wouldn’t we get the interference pattern? You could say that we are observing the marbles as we see each of them go through a slit. Well, what if we all turn our backs to it, and cover our ears, so there is no way to know what path the marble took?
    How do you define observation really?

    • The question you ask – “How do you define observation?” – is argued to this day among physicists and philosophers. It’s part of what makes this experiment so compelling. 😉

    • Observation: the basic idea is that to observe something light is then shining on it…which decohers the system…collapses the probability waves or in the case of sum over paths selects one of the many paths… So observation is by eye (even a cat’s eye) the idea being that photons are pinging of the object/particle – buckyball – or observation could even be a colliding airmolcule, electron coupling, thermal bath… etc…

      It’s a wonder if not that superposition it difficult to grasp…Why is a particle in a superposition…I think the surest way to think of it is within the grasps of Feynman’s sum of paths approach (exactly as accurate as Bohr’s p.waves). But in the case of p.waves I’d like to think that the p.waves continuses on and that in either case we are selecting the particles history from the top down. Check it out if you want…


  10. I have been watching and thinking about many of the theories, The String Theory, M Theory, The Measurement Problem, etc. I like the idea about multi Universes and the Big Bang could strongly have come from two different universes membrains crossed paths or collided to create a new membrain/universe. This to me still makes me think that we’re part of something else even bigger.Outside the multiverses there is what I call a megaverse etc. This is what is very close to, what seems to me, that cells do. Is it speculated that when these two membrains collide, is it borrowing energy from each? kind like when a sperm meets an egg? or is it creating it’s own?

    • A few physicists believe that our universe was created by a “collision” type of event between two previously existent universes’ membranes, which disintegrated in the collision. They get a lot of press, because M-theory is sexy and new.

      M-theory itself, however, is currently untestable and in physics, a theory is defined by its testability. And so many physicists consider M-theory to be more of a philosophical perspective than a workable physical theory.

  11. What would happen if you cut the photographic plate in two, and moved one half closer to the slit directly in front of it? Wouldn’t that also constitute an observation (to see if the photon went through the corresponding slit) and ‘collapse the wavefunction’?

  12. I am following you so far but I would like to take it a little further.

    Question: Are they watching the screen as they perform this test, if so would that not be considered an observation and thus collapsing the wave function at that point in time rather that just at the detectors?

    Question: The Delayed Choice experiment reveals that it can be observed and still provide an interference pattern, it is only when the data is know to the tester that the wave function collapses. So it would seem that it is not mere observation that alters the state but rather it is from our knowledge of it that reduces it from a wave to a particle. This does not deflate the experiment because it is by our observation that we come to know which slit it go through but it certainly complicates the issue and demands that we take it further as to just how we create our reality, is it just by our observation or is it through some deeper conscious act such as knowing? And if so, what does that mean?

    Thanks in advance


  13. Howard,

    The double slit experiment is over 200 years old when Thomas Young first performed it in 1801 since then and in more recent times the experiment has been revised to your liking look up double slit delayed choice, it answers just exactly what you were talking about.

  14. Interesting. It appears that small subatomic particles move in synchronicity with one another due to their wave vibrations matching as a function of their nature. Our own subatomic particles must vibrate at a rate close to the emission source in order to be detected by us allowing for thought waves to form and resonate at the same rate. Such an event would cause a synchronicity between ourselves and the particles. This is the first evidence for the reality of thought waves in physical space. It appears that particles this small are subject to connection with us. Larger objects tend to follow the law of relativity. The missing link is how gravity and larger object tie back into the smaller world of quantum mechanics. One possible explanation is that space can only hold so much “matter” in any one point in time. If the density of matter exceeds the carrying capacity at any one point in time, no matter how tiny, we get a temporal and thus dimensional shift, of equally tiny magnitude but of enormous scope. It is possible that concentrated thought waves could create a super miniature black hole and shift time and space for those around it into a new dimension very much like the one they left. It is also evident that vibrational levels determine the nature of the shift. Apparently like vibrations are attracted to like vibrations. We can create miniature worm holes that move us through time and space. If enough people have concentrated thoughts about the same thing over time, the worm hole can become quite large, perhaps becoming large enough to actually see at some point. All conjecture on my part, but interesting.

  15. I’ve been reading about this for only a very short time, but it is probably the most interesting and beautiful thing I’ve ever come across. I been experiencing an appreciation for physics that I havn’t felt since before my teachers tried their very hardest to completely ruin it in school. I’ve been looking to do something more fulfilling, perhaps a physics degree wouldn’t be such a bad thing. This website is great, thankyou.

  16. […] all of life is connected by a common "frequency" that allows for a form of telepathy? The Most Beautiful Experiment the observer effect […]

  17. This relationship can only be described in a parable of the master and the slave.Every time the master looks away the slave goofs offs and does as he pleases,but when the master is looking the slave quickly realizes and becomes diligent again.This is great writing.nice pages:)

  18. […] on to the double slit experiment (worthy of a repeat here, and here) observing something materially affects it’s effect on the world.  I repeat, […]

  19. I think that QM doesn’t say that a system exists in all possible states. I think that it says it can exist in any possible state. that is, according to the original 1930s statements that seem to be terribly misinterpreted.

    then theres these baseless assumptions:
    #photons are a single particle – despite the fact that they behave as if they were a tiny electromagnetic dipole.
    #the photon must pass through both slits for interference to be generated – despite physicists having no idea how it happens.

    • This is an ontological question that has been debated since the 1930s, the answer to which entirely depends upon which QT interpretation you favor. The Copenhagen interpretation arose as a collection of varying and contradictory opinions among the top physicists at that time. Nevertheless, one opinion prevailed. Copenhagen holds that that any unobserved system exists in all possible states simultaneously – and is thereby existentially indeterminate.

      Should “all possible states” apply only to those possible states that are distinguishable by observables? Bohr didn’t think so. I don’t think so.

  20. Could one extrapolate from this that matter only exists when we are looking at it? Do we actually live in The Matrix? I actually get a little queasy thinking about this experiment and another one where a series of particles’ rotation rates are measured (after it has been proven that they slow down when observed but are the same normally) before a few are chosen for random observation in the second part of the experiment, the particles that WERE TO BE OBSERVED in the LATER STAGE of the experiment had ALREADY SLOWED DOWN before the first measurement! WHY?

  21. Good day, Fascinating site. If that which creates reality, being the atoms change from being waves the being particles depending on whether or not we are observing them. The question I wonder is if the observer is different is the atom different? I do work with the use of psychedelic drugs and reality. On a powerful psychedelic a person often “leaves” where they are and find themselves in a totally different place/environment, interacting with different beings. Reality changes. One could say that the psychedelic action on the brain changes what the atoms become thus creating an entirely new reality. So just like the electrons, photons are a many places at the same time, we could say so are we. Our bodies are here in this world when we sleep, but in a dream we are still with our bodies and when we are on psychedelics we are still with out bodies.

    • If I understand what you’re asking, the question presumes that the self or the body (that which serves as the point of observation) is somehow more real (objective) or static (fixed) than the phenomenon observed, and is separate from the phenomenon observed.

      Ultimately, all reality is ever-changing (the atoms in your body right now, for instance, were not there two years ago); reality (and what we perceive as its aspects) are ultimately part of a self-organizing interrelational information system; we are not apart from it, but a part of it. If we can get to the place where we understand that all of it – including the “self” as observer – is first and foremost information in constant flux within an interrelational context, the questions begin to answer themselves. 😉

  22. Matter exist in two condition.
    1)Manifest condition
    2)Un-manifest condition

    Manifest———Universe is created.
    Un-manifest—–Universe is annihilated.

    Matter tendency is to increase disorder without a conscious being.
    Conscious being activates matter by injecting consciousness into it.

    Right after the big-bang occurred,universe expanded from a point to infinity.(In no time )
    Physics says that nothing is faster than speed of light i.e 300 km/sec.
    So,it is consciousness which creates universe.

  23. […] thực nghiệm “thông điệp từ nước”, hay các thí nghiệm về lưỡng tính sóng hạt cùng sự ảnh hưởng của những người tham gia lên photon, cũng như hàng loạt những thực chứng […]

  24. i am impressed with the theory of the double slit..the observer theory is potent and carries weight ,on a philosphical note…”we are but the weight of our own thoughts’…weight here emphasises our “existence”… we exist as an affect of higher concious thought…since our existence is the affect…what about the cause…?

    • In everyday life and in classical physics, events appear to be ordered in time, resulting in our model of cause-and-effect; the laws of quantum mechanics, on the other hand, are non-deterministic and time symmetric – that is, causal order does not appear to be a mandatory property of nature at the most fundamental level of reality, and so cause and effect do not necessarily apply.

  25. Amazing!

  26. In the first condition an observer is present “behind” the experiment or after it is over (on the film) if preferred. Yet the result is a wave. In the second condition the observer (he /she/ it) is between the the gun and the record.

    Does it not follow that it is a positional (mechanical) effect? The observer is present in both conditions.

    Apparently the observer / measurement need not be conscious and could be completely removed from the situation by never looking at the results or observed / measurement. If the same results are obtained with no observer then here too it must be mechanical not a result of measuring or observing.

    These things seem so obvious to me that someone must have addressed them. Thanks for correcting my lack of knowledge.

  27. I need to correct my statement. In the second condition the mechanical observer could be present and recording but no one would review the results of this recording. The only thing to be seen would be the results as in condition one. In this way the “observer” is removed from the study. If the traditional results are obtained it is not due to an observer. It may be the act of “measuring” but not the act of “observing.”

    Something must be wrong with my thinking because I can find no reference to this type of study

    • And who is observing that it is a positional (mechanical) effect? It’s impossible to exclude consciousness even here, if only because any hypothesis or proposed explanation for an observable phenomenon is, again, based on our conscious observation of that phenomenon. At the end of the day, we are observing whatever-it-is in order to form the hypothesis, even if that hypothesis purports to remove us as observers from the equation.

      This, of course, doesn’t necessarily disprove objective existence, but it does point to the fact that we can know nothing objectively, but only subjectively.

  28. Apparently the study I suggested has been conducted as presented by Carl Shaw on TED conversations July 30, 2012 part 2. Here is the URL

    “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.”

    A conscious observer is required…… Hmmm

  29. Let’s see, will this device work? “The someonelookedomatic”.

    The double slit device is setup so that whenever a particle is detected going through one of the slits a light bulb inside a large vault flashes. Another sensor detects weather or not the resulting particle is “out of bounds” on the target. When an out of bounds particle is not detected in 2 seconds then an alarm goes off. For arguments sake the particles are fired at a rate off about 3 per second. The safe door is then closed and the device is activated.

    – Is it correct to expect that the alarm will not often sound when the safe door is closed because it is likely that at least 1 particle in 6 will be out of bounds every two seconds since there is no permanent record or observation of the led light ocuring.

    – Is it correct to assume that once a robber opens the door and looks inside accidentally noticing the flashing light that the alarm will sound?

    – Does the robber have to know that the led light is connected in some way to the experiment or alarm for the function to collapse?

    – If the flashing led light is green versus red. Will the robbers assumption of what the light signifies cause the alarm to sound or not sound even though he does not know that a double slit experiment is involved?

    Can a regular person off the street easily test the observation phenomenon? I really want to play with such a device.

  30. is it possible that the observer’s mass is affecting the electron (via a gravity pull that all objects possess)? or perhaps if it’s a metal camera, could it be the material interfering?

    • Gravity does not apparently play a role in the double-slit experiment. It is not a fundamental force. (Then again, we don’t yet have a working theory of gravity in QT.)

      Regarding the possible interference of a metal object, keep in mind that the experiment has been performed with not only electrons, but photons (the very first double-slit experiment used photons, in fact), and, more recently, large aggregate molecules (including one with a mass of 1,298 AMU).

  31. So, it is possible the cows do stand up after the car goes by. Just a joke. But there are infinite possibilities of outcomes and realities being influenced by one person.

  32. Ok, so when the observer is not present we get an interference pattern, but when we have an observer the results are as expected.

    Does this mean that if the observer expects an interference pattern, perhaps because of different education, that it would have those results instead?

    In other words, is my understanding correct that the reason the particles behave this way is because that is how logical scientists think the particles should act?

    • Not sure where you get the idea that an observer’s “expectations” are inherent to the results of the double slit experiment; perhaps this is a semantics issue. As Bertrand Russell wrote, science can only explain one thing in terms of another thing. That is because we live in a relational universe, where the boundary between an objective, “out there” reality and our own experience of that reality (that which defined classical physics) all but disappears where quantum mechanics is concerned.

      In this case, the experiment’s results point to the inextricable relationship between the observer and the observed.

  33. Hi there, i am currently interested in the observer effect and i have some questions. First of all i would like to mention that my field has nothing to do with physics so excuse me if i make any ”dummie ” question. Yet i am in the beginning of my small research for quantum physics and it would be great if you could give me some answers. So as i was watching the observer experiment i was confused about the probabilities. If probabilities are all over the place why photons go to a specific direction (lines)? I understand that photons behave like waves but why don’t they go all over the place on the photographic plate?

    • First of all, there are no “dummie” questions here.

      And what we are seeing, at that point, is what were waves of light behaving instead like particles of light. It bears noting that matter also has this dual (wave/particle) nature, as interference of atoms has also been observed. The deeper “why” – interpretation of the phenomenon – is a subject still debated among physicists.

      • Is this has anything to do with Niels Bohr light theory? Also thank you very much for your answer.

      • If you are referring to the principle of complementarity that he conceived, yes.

  34. hi, can someone kindly answer my questions: in this experiment the photon acts like a wave without any observation, and a particle whilst observed, does this mean the primary behaviour of a photon as it leaves its source is a wave? and will this be true to all quantum matter?

    • What it means, according to the Copenhagen interpretation of QT, is that it exists as a wave function unless observed, as you stated. Period. Theoretically, were we to set up an apparatus that could detect the photon at its source, the wave function would similarly collapse. The collapse of the wave function by observation is the transition from possibility to actuality.

      And yes, this seems to be true of all matter.

  35. Yes, the implication then, is that an “0bserver” is responsible for all matter created from the Big Bang, the Bang itself, and the subsequent matter we are NOT directly observing in the universe today. Basically a universal consciousness; Rubbing up against theology in that case. Another school of thought holds that matter is naturally always in its wave state and only collapses into form/matter when a conscious entity looks at it. Meaning the universe disappears when we aren’t paying attention to it. This presupposes that matter in its wave form functions the same as in material form, I.e., a planet or star continues doing it’s thing regardless if it is being observed or not. Messy concept. KEY point to keep in mind: “wave” in this case doesn’t mean strictly like waves in water, but in frequency of vibration and possibility of position at any given moment.

  36. Time and space are intertwined. A probability wave occurs when matter goes unrecorded or unmonitored. Could the future be a probability wave? In the double slit experiment, when unmonitored, the particles hit the sheet at every possible location they potentially could. Their waves of potential showed both their ideal paths and the paths if they ran into trouble. If they bounced off of something. If something went wrong. But when monitored, the paths they took were always the paths of last resistance. The paths they SHOULD have taken if there was nothing to interfere with their trajectory. If our future is a probability wave, then our PRESENT is the effects of a monitored moment in time. We are all our own recording devices of each moment in time. So each of our realities that we experience are paths of least resistance. In my reality I’ve never been seriously injured. I’ve never even broken a bone. Tomorrow I could hear that you’ve been diagnosed with terminal cancer. That you’re going to die. That’s OK because my reality, my path of least resistance allows me to keep on going and experiencing or creating the next moment. However in your reality you never get that diagnosis. Because, where that potential existed in your future probability wave, your own recording device on your moment in the present is always taking the path of least resistance. So even if you responded to this very message and told me that I was wrong and that you had indeed been diagnosed with cancer and it was terminal it would not matter because it is still my reality and not yours.

  37. Does a conscious observer actually have to sit there and watch the experiment for this effect to be produced? Or does an unconscious observer effect the same result?

    • There is no way to know for certain, as a conscious observer is ultimately required to observe the unconscious observer in order to find out. 😉

  38. What if an unconscious observer learns the answer but then deletes the information before it is observed?

  39. Everything does root back to the mind eventually.
    The Future’s Lost Memories
    Just because something is incomprehensible or different does not mean that it is not necessarily right. In fact, it is the one who determines it incomprehensive that makes its existence sound in the first place. In other words, there is no problem if no one sees it as a problem, and there is no solution if there is no problem. Furthermore, the ones who claim it incomprehensible are incomprehensive towards the incomprehensible. If there is a 10% chance that one believes something is impossible, then they make up 90% of the reason why it can’t be done. Everything is visible, it is just the individual’s choice whether to see or not. Everything only exists because we interpret it as such, and reality is whatever we observe to be reality. It is safe to say that without interpretation, nothing exists.
    Just because there are laws doesn’t mean that there are exact boundaries. In other words, laws were made to expose boundaries we cannot go beyond, thus proving that there is something on the other side that created the boundary being exposed. The boundary is also there before the law… always. The only reason that laws form is to prevent something that causes whatever’s outside to differ.
    Various boundaries including the one boundary that has not yet to be ruled or lawed over. The boundary of death. “What exactly happens when we die?” one might ask. The questions really are: When do we die? Why do we die? Who is the killer? But the main question is “Do we even die?”. People see death as the extermination of a being, but died is not the RIGHT word. Probably transferred. Well not that it matters, but this is a boundary that extends beyond physical evolution. There is no observer to come back and tell what EXACTLY happens after death… and even if there was, it would be hard to understand. In other words… stop worrying about it. One should live life to just because they have a life to live. The reason why one should live is to find the reason why they haven’t died yet. If people believe that we were born to die, then I guess I’m the only one who would die twice just to live again. One should want to forget about the dreadfulness of the past and ignore the anxiety of the future. The present is what holds reality together, and it is the Gift that brought reality in the first place.
    Everything depends on interpretation. Interpretation is its own measurement in itself with no exact or definite measurement system. It can measure the thoughts of others, the color of the sky, the words from a book, and even the reason why things happen the way they do. Interpretation is one of the strongest concepts of reasoning and reality, but there is one thing that it cannot measure. The feelings of others. Though the thoughts of a person can be easily figured out, it is physically impossible to find out exactly what one is feeling. In fact, there is no EXACTNESS to feelings at all, just as there is no such thing as an exact measurement. Feelings are things that can only be interpreted by the one wielding them. For it is the feelings of someone that gives them an actual will, the most powerful force of all. When someone starts to interpret their own feelings and put them into effective action, they break through the first boundary…into something genuine. This tranquility is what every person, or philosopher rather, is in search of. It doesn’t have to be an object, place, or person. It might as well just be a state of mind in which reality is so peaceful, that the waters in the oceans mirror the starry night sky without fault or refraction. This is known as the Essence of The Alchemist, where all possibilities are open, and time stands so still that even infinity repeats.

  40. If a computer randomly generated a series of double slit experiments choosing each time whether to observe the slit or not and no human observer was around at the time and did not look at the information generated until say several years later how would the observer effect happen?

  41. Where can a person observe the double slit experiment being exectuted (including the observation of the photon/electron being observed) either on line or in person?

  42. I wonder if the observer effect is actually the observers beliefs of what will happen hold true and happen. Thusly has anyone done an experiment with someone who actually believes that the photon will behave like a wave? This would make every observation subject to trusting that the observer actually observed what they say they observed (if someone who believed differently observed same then their act of observation would contaminate the experiment) and then also whether they believe or do not believe what they claim they believe. In essense it makes any observed fact subject to trust in the observer, which is obviously true to sceptics but for entirely different, motive free reasons. Basically the implications are that nothing in the physical universe is ever truly known definitively or beyond debate.

    • I am very happy. With no knowledge of QT I have, from my early teens, believed this theory to be a true reflection of reality.
      I think the simplest way to think about it is to think that ‘energy’ can only become information when it is received by something or someone. For example, sound does not exist until it is heard. Distance does not exist until it is measured. That is why any universe cannot be considered infinite, as true vacuumous emptiness is not able to be measured. You can only measure the measurable and until it is measured it cannot be said to exist

  43. Doesn’t this experiment call into question the materialist basis of our entire scientific method?

    If observation fundamentally alters reality in this basic experiment it clearly leaves open the possibility of any number of philosophical models of “reality”.

    What is the mechanism by which this seemingly magical effect occurs?

    Pairing this with quantum entanglement leaves nearly everything open to question.

    I’m fascinated that these effects are seemingly internalized by mainstream science without really exploring the fundamental questions it raises about the very nature of “knowing”.

    In short these effects leave open the possibility that we have very very little idea about the nature of reality.

    And, to get crazy, the possibility that dark energy could be consciousness.

    The prevailing view of consciousness as simply an objective product of understood physical process could be absolutely wrong.

  44. Your comment is well taken, joining a growing sense in the West that Consciousness is the only reality; the Prime Mover. Eastern thought variously describes matter and existence as a dream state (of Consciousness) or that we are the creator’s method of experiencing itself, etc. You get the drift. It’s no joke that the fellows at Cern are looking into the meditative abilities of Monks, as a tool for exploring consciousness’ effect on the material world. The two disciplines are seeing the same thing.
    That said, Dark Energy exhibits a force, tending to expand the universe, pushing the galaxies and clusters, farther and farther apart, even as Dark Matter tends to help them form and stay in clumps. Once the star era of the universe is over– it has a very, very, very long “time” to exists until it runs out of matter energy. What will Consciousness need of that?

  45. Hi Kelly,

    Some very interesting discussions on here. I remember first hearing of the Quantum double slit experiment when I was a student and thinking it was pretty strange, but not for long because I always understood energy, matter and consciousness were basically the same stuff. The difficulty it talking to scientists about consciousness without them thinking you’re “On a trip”. Here’s my attempt to do just that! Any comments folks?

  46. Very interesting to entertain the idea of consciousness as a minutely fundamental building block. You posit that an electron in its wave/particle existence would have enough of it to “sense” the other slit (which would mean it had a “sense” of self in order to notice) and it reacts with a wobble, which creates the wave pattern. Would this consciousness building block be quantifiable in the way we quantify energy? Or should it be a “field” ala the Higgs Field, and be a medium on which it is aggregated as material forms become very complex, such as the human mind?

  47. When we observe change of position of something, there are (at least) 2 equally valid alternative interpretations: i/. that the thing has moved along the distance between A and B, ii/. that the thing has disappeared from A and been replicated in discrete consecutive steps along the distance A to B. Both interpretations have the same mathematical consequences and have always been consistent with our observations of reality.
    I’m sure none of this is particularly new or controversial.

    My point is this.
    That of these possible interpretations, we have always assumed without serious question that interpretation i/. is true. Our intuition is that we, ourselves, move and that we remain the same as we do so, and consequently we naturally reject interpretation ii/. Moreover, interpretation ii/. raises the seemingly absurd notion that matter can be created out of nothing.

    Today, however, we have further observations never previously available. Observations of quantum uncertainty, the consequent creation of particles, wave-particle duality and non-locality are surely telling us that our historical acceptance of interpretation i/.has always been wrong. Had we known what we know now, the more intuitive interpretation would have always been interpretation ii/.

    There would then be no need to talk mysteriously of particles seeming to be in 2 places at once, for instance. The 2 slit-experiment (at least in accounts of it written for non-specialists) is said to shock because the logical expectation is that a particle must go through one or other of the slits. But that logic only applies if we assume it is the same original particle that arrives at the screen. If what we see as change of position of the same thing actually involves the serial disappearance and replication of particles, it is surely far easier to accept that there can be more than one point at which any given replication might take place. As at present, these can be calculated in terms of probability.

    If this is true, we may be forced to answer the question, ‘what happens to a disappearing particle and where does the replica come from’ with the proposition that matter and space (or space-time) are mutually convertible forms of the same thing.

    Then, rather than treating the application of a force to a particle as accelerating the particle, we can say that the application of a force to a quantum of matter changes it into a quantum of space and changes the next quantum of space into matter, and so on in proportion to the size of the initial force.
    And from this, other observed phenomena could still be explained coherently. The finite speed of light, for example, might be explained simply as the maximum rate at which quanta can convert between space and matter states. The distortion of space-time around bodies may be because quanta stretch or compress when converting from one state to the other, causing similar stretching or compression to surrounding space quanta (or even the other way around – that it is stretching or compression of quanta that causes the change in state).

  48. I haven’t read all the above replies, just skimmed them, so I apologize if someone has already presented my thoughts that follow.

    One interpretation of the mechanism by which single photons or electrons, one by one, form the interference pattern, no matter how infrequently they are fired at the double slit apparatus, is that each particle passing through a slit interacts with the quantum state of the slit, changing it. That altered quantum state subsequently affects the next particle in a different way than the previous one. The quantum state of the adjacent slit is also altered.

    The time-accumulated pattern of interference is due to the fact that each subsequent particle is passing through a “different slit” with regard to the quantum state of the slit. If we accept that the quantum state of an interaction that results in a change in state (momentum) of one actor (particle), then it follows that the other actor (slit) has also undergone a change in state. There is no reason to believe that the state of the slit will instantaneously bounce back to precisely the state prior to the interaction.

    So not only does the particle history evolve into the interference pattern, so too does the slit quantum state history evolve. We simply fail to evaluate it.
    In this interpretation, the particles remain particles, no collapsing wave, no underlying mysterious reality, no observer effect that collapses one universe from among an infinite number of probable ones, etc., etc.

    It seems to me that the basis of current QT understanding of the double-slit experiment rests on an incomplete evaluation of the entire system.
    I would very much like to see another experiment as outlined below. Perhaps this has been done, and if so, I’d certainly like to read about it!

    Set up the experiment so that in the plane of the interference pattern there is a second particle gun which fires at the double slit at 180 degrees to the original particle gun. In this manner particles passing through the slits from the second gun will (according to the interpretation presented) alter the quantum state of the slits away from the quantum state created by particles passing from the first gun. If the original interference pattern is simply created by an accumulation of the history of the interaction with the slits, then the second gun’s effect would be to alter that history, thereby disrupting the pattern from the first gun, i.e. no interference pattern, at least not the one we observe in the classical experiment. If the wave-particle nature is a correct interpretation of reality, the second gun’s effect will be null, and the classical pattern will emerge.

    Variations on this theme present other opportunities to study the quantum state evolution of the slit, which has, I believe, been fairly ignored to date. For example, the second gun can fire at different angles to the first gun, say 150 degrees, 120 degrees, etc.

    Current theory may offer a prediction for this experiment, but I’d like to see it actually carried out so we can see what reality presents to us.

  49. guys …… de broglie is just a hypothesis
    it was only made to explain this phenomenon
    o..m..g…what will happen if De Broglie hypothesis is nothing.
    then what is causing this to happen?
    [[de broglie states that a moving particles constitutes a wave i.e. proportional to its momentum.]]

  50. A single stone dropped in a pond generates a single wave that will wrap around a boulder and split in two and each will split again as each wave encounters more objects. The multitude of waves will dissipate in the medium proportional to its resistance. The pond will become still again.

    That same single wave will split as it encounters multiple openings in a breakwater.

    But limit your observation to just one spot blocking out the rest and you see just one wave. Does your limited observation show a proportionally weaker wave after splitting? Yes it will, proving the observation method was at fault.

    That single stone, now a photon of light fired in a vacuum generates nothing except a gravity wave distortion. Gravity is always present as a constant in either case.

    Test this in a vacuum please where the force of gravity can be controlled and look for different gravity wave distortions proportional to the change in gravity.

    A photon fired a anything generates a wave in motion through a medium of air, water, gas and gravity.

    I think even Einstein would agree that the effect of ‘Gravitational Lensing’ will alter the observation proportional to the change in the strength of gravity of a objects distorting it.

    Test by switching out one black hole with a stronger black hole as a 2nd lens to observe the altered galaxy behind.

    My Optometrist will be happy to help.

  51. Consciousness conceives, the brain receives and our mind perceives…I heard that somewhere…it’s cool to read through all of the comments and queries…helps me to perceive it better.

  52. Why does the barrier with two slits exist if we are not observing it? Shouldn’t the barrier (mass) be in a super position as well?

    • Of course. Everything is. You who asks and me who answers is. There’s a funny t-shirt that reads “When you’re not looking, I’m just a waveform,” which pretty much sums it up.

  53. I want that shirt!

  54. I want that shirt too. May have to have one made. 😜

  55. “The only solution is to abandon the idea of a photon — or any other quantum system — as having a location in spacetime until it is observed.”

    There are two solutions, the other one leads to the multiversal ideas (except they don’t actually “split”). It’s the only completely natural assumption as far as I know. Superdeterministic on the whole, but random and changeable from our perspective.

    The observer effect then becomes the question: which part of the multiverse do you see when you see a wave and which part of it do you see when you see a particle. And why are we observers in the first place, what is an observer and what isn’t.

  56. Has anyone observed the double slit experiment through a mirror? At different angles through the mirror etc?

  57. imagine the 2-slit experiment with detectors at the slits, but the detectors are, by chance, defective. the detector “tells” the observer that the photon went thru slit one when in fact no photon was detected. if the observing human believes this false information, does the wave function still collapse?

    • fascinating proposition. It would seem “believes” is the key word as it relates to the acting agent of change in the Conscious observer effect. If it is, then we open a Pandora’s box of Pandora’s boxes. The very nature of Consciousness becomes an issue. And everything becomes irrelevant as all realities are equal and indistinguishable.

  58. As observed. Pun. A camera was placed at a point just before the….photo sensitive paper as soon as the remote camera started to record/photo – the particles or was it waves…. anyway – the photons changed from waveform to
    particles as if they had stopped, gone back in time and re*emerged as particles. Another possibility would be the speed of change – in that it is so fast that we could not possibly perceive it – if our synapses cannot keep up with the change then it would not register in our memories. Alternately, there could be a neuro-biological reason that causes the light to change its condition. In nature animals and indeed humans are sensitive to being observed, even when the observer is out of sight. This being true then the same signals which are being transmitted by the observer, to a human may perhaps be the same signals transmitted to the light in the slit experiment.

    Not hard to take on board when one considers moving amoebae around on the slide by willing them to move across the slide of your microscope.

    Or, perhaps we are approaching the basic building blocks of creation, genesis in every sense and that, the higher powers that be wont let us near for fear we might treat the universe the same way as we treated our own planet.

  59. I request permission to use your image and, If I could quote: “If one neglects to observe which slit a photon passes through, it appears to interfere with itself, suggesting that it behaves as a wave by traveling through both slits at once. But, if one chooses to observe the slits, the interference pattern disappears, and each photon travels through only one of the slits.” For my book. Conscious Evolution. Thanks

    • With attribution, of course… and, if you would, please send me a copy of your book when published? Wishing you the best on your endeavor!

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