Quantum Weirdness – Part 2 Double Slit Weirdness

Quantum Weirdness

A Matter of Relativity? 


Copyright 2006/2007 James A. Tabb 

Part 2 – Double Slit Weirdness

When a proper light source (coherent – light from a single source all at the same frequency) is placed in front of a screen with a narrow slit, the light is diffracted (spread out) as it goes through the slit and appears as a shaded band centered on a screen or photographic film. The light is scattered and/or bent by the edges of the slit as shown in Figure 3.

Single Slit Diffraction
Figure 3. Single Slit Diffraction

 If we add two more slits located side by side between the first slit and the screen, the light passing through each of the new slits is diffracted again such that the photons from each slit are bent across each path and combine to reinforce or cancel each other where they strike the screen.

 Double Slit Diffraction

Figure 4. Double Slit Interference

The result is an interference pattern (light and dark bands) on the screen as shown in Figure 4. If you block either of the two middle slits, the interference pattern disappears. If a photographic film replaces the screen and the intensity is reduced so that only a few hundred photons are sent through the double slits before the film is developed, the interference pattern will be made up of individual dots organized in a pattern that duplicates the interference pattern. Keep the film in place long enough and the patterns become more complete. Put a cover over one of the slits and the film still shows dots, but no interference pattern, only a diffraction band. Put a detector in one of the slits and the interference pattern also disappears.

Now if the light source is reduced in intensity enough to send only one photon at a time, a weird result can be seen if the photographic film is left long enough (days or even months in a very dark box) where both slits are left open. The interference pattern continues to develop on the film, even though there is no possibility of interference (or even photon bumping) unless the individual photons go through both slits somehow.

Part of the current explanation is that the photon goes both ways, but any measurement (putting a detector in the path) always disturbs the measurement. In fact a whole class of quantum theory has developed around the inability to make precise measurements due to the measurement disturbance problem. How do we explain this quantum weirdness?

A Matter of Relativity

There are two processes going here. One process is the real time that our experimenter sees, about 1 nanosecond per foot of photon travel. The photon is traveling through the experiment with real and measurable delays from the emitter to the first slit and from there to the double slits and from there to the film. The other process is that the photon’s relativistic path is zero so it is in contact with the film and the emitter at once and all of its paths in between are of zero length and require zero time. All paths that can lead to the same path are conjoined. Time of flight and distances for the photon expand only as it passes through the setup. The photon and the observer see simultaneous events differently. All the events are simultaneous to the photon, but none are to the experimenter.

All the elements of our experiment have no depth and seem to be congruent as if they were paper cutouts that have been bonded together with the emitting source. As observers, we can’t see it. As the photon leaves one element of our experiment, such as the first screen with one slit, the double slits are squeezed down to a point and plastered across its nose. The photon easily fits across both slits of the second screen as the distances to them are zero and thus the distance between them is also zero. Indeed it fits across the entire second screen, but the edges are less distorted. Since the photon is also plastered across the slits, everything behind the slits is also plastered there – the entire path is available at one instant as in Figure 5 a. The photon is able to take all paths (even simultaneously) that lead to a common point because they are all in front of it as it enters our experiment, and zero distance separates all the paths. No amount of fiddling with flipping mirrors or detectors will fool the photon into disclosing its path because the mirrors and detectors are also plastered to the photon’s nose throughout its (instantaneous) flight. The mirrors and detectors are in place when the photon makes its decision or they are not. The result is path shut or open.

As the photon moves from the first screen to the second, the second screen moves with it (attached to its nose) until it reaches its normal (real world as we see it) dimension and then expands as the photon moves into the slits as in Figure 5 b. Portions perpendicular to the path of the photon become normal size and atoms from the edges again buffet the photon.  Everything behind the photon is of no consequence, gone – vanished.

Relativistic Double Slit

Figure 5. – Relativistic Double Slit

 From the relativistic point of view, the photon has a number of crisis points such as within the first slit. As it passes through the first slit, the atoms at the edge of the slit buffet it and the photon’s path is randomly diffracted from the original path.   The slit has grown to normal size (perpendicular to the photon’s travel) but now the photon is virtually attached to the entire screen containing the double slits in the background that represent the next crisis point or wakeup call. If neither slit is blocked, it has an opportunity to go through both.

Photon Recombining

Figure 6. Photon Recombining

I see the photon as being a packet of energy that obeys the laws of conservation of energy. It flows around the barrier between the two slits only if it can recombine on the other side without ever completely breaking into two separate pieces. It behaves almost like a perfect fluid and leaks through where it can, but unlike a perfect fluid, it cannot separate into multiple “drops”.

If the packet can meld behind the slit spacer as in figure 6, it does so before it separates in front of the spacer. The melding process takes place an integral number of wavelengths from the slits and results in a change in path that leads to an impact in the interference pattern, a pattern that can be calculated using the methods of QED.  As soon as the melding takes place, the photon separates in front of the slit spacer and begins joining the rest of the body already melded together, so that the photon is always a full packet of energy

If melding does not take place because of a blocking detector or some other shield, then the photon pulls itself into whichever slit passed the bigger portion of its packet and slips through that slit whole.  If it is the blocked slit, it is destroyed there.  If it is the unblocked slit, it comes though whole but does not interfere with itself because it did not meld around the slit due to the blockage in the other slit.  It may also be destroyed by the slit itself.   The photon is destroyed in the blocked slit or on the film behind the open one, never both. It makes no choice. In the case of a blocked slit, there is no recombination. The side with the larger energy pulls the photon through an opening if there is one and if that opening has a detector or blockage, it dies there.

The answer to the weirdness of photons seeming to interefere with itself is that it is due to the forshortening of the experiment due to the effects of relativity.

Next:  Polarized Light Weirdness Explained


17 responses to “Quantum Weirdness – Part 2 Double Slit Weirdness

  1. You’re a brave soul, James A. Tabb to tackle a paradox as infamous as the double-slit experiment. I’ve pondered it for decades and keep an open mind on it. I’m delighted to have encountered your web-site which I view as a real source of enlightenment, while I I frown upon those who opt to accept the “quantum weirdness” as a soft-option explanation to side-step their “responsibility” to seek out a better theory or understanding of what is actually happening in our physical world. I look forward to spending many hours reading through your material. While I have no formal qualifications in Physics, I do have a single-minded determination that allows me to investigate and research specialist areas – such as this topic – and derive tremendous satisfaction from doing so. I personally believe these issues are absolutely “core” and deserve hugely more attention from the scientific community that they actually get. I get upset when I think of the huge numbers of brilliant minds of modern science focusing on soft-options and the relative few that are willing – or able – to tackling head-on the core-issues such as the true nature of light, gravity and perhaps a unified theory.

    I should stop this waffling-on and again take this opportunity to congratulate you on providing an excellent alternative insight into the mysteries of light.

    In closing, I have a question that you may be able to answer for me.

    Do you know if any experimentation based on either the double-slit experiment or partial-reflection of glass surfaces have ever been carried out in near-vacuum conditions?

    Keep up the good work!


    Tom O’Flynn
    IKON Systems

  2. Thanks Tom for the encouragement. I’ve spent a couple of years engrossed in “thinking” about it, mostly thought experiments. You have no idea how many wrong turns I took before settling on this theory.

    To answer your question, I believe that all double slit experiments with electrons and other massive particles have been done inside evacuated cathode tubes.

    I don’t know of any light photon experiments off hand that have been done inside a vacuum, except that some of the weird behavior of photons around galaxy lenses are in space for the vast majority of the trip. You will find that I mention that effect at the end of part 5 as being compatable with my theory, though it is not exactly a double slit. I’ll look around in my notes anyway.

    It is quite likely that some of the tests carried out in the Hubble telescope and some of our space probes depend on diffreaction in a vacuum.

    I think that this theory, in a way, makes quantum mechanics compatible with Einstein’s Relativity. The weird behavior is certainly explainable by relativitistic effects.


  3. Pingback: Virtual Particles - A new look at double slit weirdness « Quantum Weirdness

  4. Hi,
    I’ve been kicking around your ideas on my home forums (above). A number of problems arise.
    Perhaps the most serious is that this theory would not work for electrons and other ‘massive’ particles which we know ‘interfere with each other’. Clearly electrons do not travel at c so we cannot talk about a zero path or a zero time – the electron takes a finite time to complete it’s journey (from its own F.O.R.). Your explanation would, therefore, appear to break-down for massive particles – even though we can still observe interference (as per the 1961 Claus Jönsson experiment – the basic Young’s double slit experiment with single electrons).

  5. Oldtimer,

    I absolutely love this web site? Do you have a book out yet? If so, just send me the Amazon link and I will buy it ASAP. I have a camping trip coming up soon and need some good reading material.

    OK, now for the question….

    In the double slit experiment, has anyone tried to use only one detector? What I mean is, set the detector for one slit only (let’s say the left one). Then fire photons one by one. If the photon is not detected. It either missed both slits, or went through the “other slit”.

    However if a photon only interferes with itself, then the photon should alway be detected by the left slit.

    Oldtimer, I hope your up for it, because this really keeps me up a night. 🙂 I have a lot more questions.


  6. Thanks Craig

    No book. What you see here is what you get.

    What you suggest has been tried with all sorts of ingenuous devices. A single detector on either side foils the effect. There have been detectors that can be switched in and out of the system fast enough that the detector is out of the setup when the photon is emitted, then switched in before it reaches the slits. The photon only goes one way or the other. You never get a situation where every photon registers on the detector. Nor one where every photon goes through the other slit.

    You never get a hit on the detector and a spot on the screen from the same photon. You never get two spots on the screen from a single photon if both slits are open. One at most, but the interference pattern suggest that two were present even though only one photon was fired and only one spot resulted.

    Nor one where an interference pattern develops when one slit has a detector monitoring it.

    One problem with a single detector is that you never know whether the photon that did not register on the detector actually went through the other slit unless you have a film strip (also considered a detector). It could have hit the walls of the apparatus and been absorbed or reflected back somewhere unexpected, or not actually fired – misfire?.

    If you have a double slit with a film strip in the back and fire photons one at a time at the slits (with no detectors other than the film strip), an interference pattern develops from those that get through.

    If you put a detector in front of either slit, then the interference pattern disappears. You get hits on the detector and a pattern on the film from the ones that go through the other slit.

    However, it forms a normal diffraction pattern (which is normal for a single slit) but not an interference pattern unless both slits are open and no detectors are used at the slits.

    There are always missing photons that never make it through the slit due to hitting the spacer between the slits and being absorbed there, so depending on one detector and speculating that the other MUST have gone through the other side is not a valid assumption, I’m afraid.

    Also, in most apparatus you can’t be sure that a photon has actually been generated unless it is detected somewhere. Most of these generators are emitters that are “turned down” to very low levels so that the photons register in very low numbers that you can see appearing an a detector one at a time, but they are not predictable as to exactly “when” they were emitted. They come out at random times in spits and spurts or occasionally. Some are pretty regular but still you can’t depend on one going at a particular instant. So a detector that does not register a photon is no guarantee that one was emitted.

    So having a film strip, or some sort of multiple detector arrangment is essential to the setup.

    It is a fun subject.

  7. Oldtimer,

    My thought was to use a film strip in back, but also use a film strip upfront and put slits in it.

    That way, the photon is fired, if it misses the slit, then then it should register on the film strip up front.

    fire the photon
    if it detects in back, did the left detector see it?
    if not, it had to take the right path

    if it is not detected on the back screen, did it hit the front screen? Did it get detected on the left?


    I would love to get my hands on a apparatus to do this my self. 🙂

  8. Bikerman makes an excellent point. I read somewhere that the double-slit experiment has been performed with buckminster fullerenes and yields the same results. C60– that’s massive!

    • I’ve seen that too. It is not the size, but the velocity. What are the massive particles made of? I’m talking about the interanl components of the atoms, down to the quark level. The atoms and larger molecules are moving fast but not nearly at c. However they have components moving that fast or nearly so. If internal components are moving at or near c, would that not necessarily give relativistic qualities to the massive particles they that contain them? There may be a bit of a tug of war going on inside because some components are moving at times in the same direction as the buckminster fullerene and some the other way, making the whole approach and retreat from c at some very high rate and giving it some qualities of relativistic particles.

  9. Thanks, James. I’m an engineer with minimal physics background but have read well over a dozen books on quantum weirdness. Your approach is so very satisfying in that the zero relativistic distance eliminates all the “how does the particle know” type questions.

    Now for my question. My latest intrigue is with Wheeler’s astronomical scale delayed choice experiment based on Mach-Zehnder interferometry. Does your approach really hold up when the time scale is thousands of years and the distance scale is thousands of light years? From a photon’s view that is all of zero size?

    Also, it would be great if the great Dr Quantum double slit animation on youtube had a followup animating your relativistic explanation! I think that’s big bucks, though.

  10. Mitch, this question is probably on the minds of a lot of other visitors so I have decided to include it here. Thanks for asking.

    The photon is launched in a specific direction and arrives there in zero time. A distant (for it) arrival point is just that, a point. The point of arrival is defined the instant it is launched. However, the point of arrival may involve a number of different paths, all of which are contracted to a zero distance apart at the time of launch. They may be perpendicuar to the path locally, but not from a distance. Two street lights a mile away look much closer from wherever you are.

    There are some real times for the photons travel from our point of view. It may take millions of years for it to reach our lens, even though the photon takes zero time from a space contraction standpoint.

    When a photon is launched from a distant star, its landing point does not change due to the motion of objects in between or the time (as we measure it) involved to get there. You might think that some of them that were headed for the earth may be intercepted by the moon or a intervening galaxy of stars. Actually such intervening point was defined at launch and the photon is destined to hit it, no matter how much of our time we measure.

    A distant galaxy may act as a lens because some of the paths that have been contracted to zero include the paths around the galaxy and some of those paths point to our lens. Very few photons have paths around such a galaxy and very few have paths that are close enough in length to cause interference, but then the number emitted in our direction is very high and some of them fit the circumstances for interference. In that case the paths may interfere with each other as the paths collapse to zero or in other words, shrink to a zero path width. Their shrinking to zero path width does not mean that the path length from our time standpoint is also exactly zero.

    In the case of a double slit, the idea is the same. There are multiple paths the photon can take during its travel to the landing point, but they are all contracted to zero width at the time of launch. Again from the standpoint of the photon, it all is done in zero time over a zero path and all paths are combined to reach the destination. The length of the various paths do nothing but slightly delay the photon in one or more other paths as we measure them. The result when they reach that predefined point is they have experienced some interference with themselves. Photons launched in a direct line to the ending point do not interfere because the great preponderance of the paths are all the same. Yet there is some dither, I would imagine, leading to a band of some non-zero width.

    The slits are contracted to zero distance apart from the standpoint of the photon at time of launch and the time to reach the destination is instantaneous within the lifetime of the photon as it is always instantaneous. Go/splat! We see it differently, of course because we can measure all these distances and times with great precision. We just have not embraced the concept of zero flight time and zero distance for the photon and not understood the concept of zero path separtion due to distance and relativity effects.

  11. I’m confused. Is this a scientific explanation? If so where are the references and observational data?

  12. James, I only just found your writing, and it rings very similar to what I have been thinking. I am having one of those “I am not alone” moments! I love physics and have been bothered by this relativistic explanation for a few years now.
    I am a total classicist, and think alternate universes (and other extreme explanations) are unnecessary when you consider that from a photon’s perspective, it’s entire journey is instantaneous. So of course it seems it can predict the future (its detection) – when detected, it’s journey is suddenly two discrete journeys and thus the interference is lost. I need to read all the comments a few more times to see if we are talking about the same thing 🙂 If we take relativity seriously, we could even say that, to the photon, the universe shrinks during it’s journey, and that the start and end point (and all the paths) are in the same ‘place’. This explanation fits with the proposition that waves are the artifacts of cross-sectioning energy (or mass) in motion. I have long dwelt upon how circles (or rotation) in the complex plane can take on the appearance of spirals and then waves (see for example The Road to Reality by Roger Penrose in which examines the structure of space).
    On the down side, I have not yet formulated a way to deal with more massive particles. Anyway, there is too much to this subject to do it justice in a blog comment, so I will stop now!

  13. Hello,
    One question came to mind: if from the photon’s point of view everything is squeezed into one point, how can interference happen? From an outside observer (relatively at rest), we ‘think/perceive’ it as waves interfering. Yet the photon has no space to recombine (in its frame of reference).

    • We know that the photon contains energy and is moving at the speed of light. It needs to be infinitesimally thin (front to back) but it can be wide, like a pancake. Radio waves act like particles at times and they would be very wide. Even very high speed particles can have rotational spin in either direction, and can spin at speed that relate to frequency, and even kind of slosh back and forth. It can also be spread like a stick instead of a pancake and slosh back and forth from one end to the other, the stick flying along the path like a propeller that is stuck or even rotating. It can’t be tumbling front to back or a part of it would exceed or be less than the speed of light, but the stick can be rotating at almost any speed. The sloshing can be tuned to the frequency of the particle and still have phase attributes due to the orientation of the stick. There is thus space for waves interfering when two pass either thorough or incredibly close to the same point(s) in space. They are electromagnetic in flight and so I think there they can interfere without recombining.

  14. This sounds far-fetched and speculative in the extreme.

    If one is to speculate, I would prefer to speculate on more likely scenarios.
    Lewis Little’s Theory of Elemenary Waves makes the most sense to me, that is, there are guide waves coming from the detector which interfere with each other, regardless of whether there is one photon or many.

    If you tried the same experiment with water, instead of light–if you moved the detector back, the interference pattern would change–and yet, if you do that in the double slit eperiment with light–the interference pattern remains the same.

    Using Occam’s Razor, I see an interference pattern similar to other media, then that is what it is. Since these patterns are common with waves in various media, then we are seeing the action of ‘some’ wave. Since the interference pattern on the detector does not change when the detector is moved, then the interference occurs BEFORE the slits.

    The reverse photon guide wave neatly explains all the weirdness of the double-slit experiement.

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