"I know that when I was in my late teens and early twenties the world was just a Roman candle - rockets all the time ... You lose that sort of thing as time goes on ... physics is an otherworld thing. It requires a taste for things unseen, even unheard of - a high degree of abstraction ... These faculties die off somehow when you grow up ... profound curiosity happens when children are young. I think physicists are the Peter Pans of the human race ... Once you are sophisticated, you know too much - far too much. Pauli once said to me 'I know a great deal. I know too much. I am a quantum ancient.'" - Isidor Rabi
Quantum Reality
Part 5 of "An Introduction to Quantum Reality"
The previous pages of this "Introduction to Quantum Reality" have presented the groundwork for the following discussion. We are now in a position to review what we have discovered, and hopefully reveal a more accurate picture of "reality" at the quantum scale.
Hopefully by this stage you will have read the previous four pages:
1) Quantum Mechanics: An Introduction
A Review of Previous Pages
In Quantum Mechanics: An Introduction we were introduced to the double-slit experiment which reveals the strange duality between particles and waves. Even though single electrons were shot at the double-slits, an interference pattern was produced. This result shows that until it is observed, a particle has a wave-like nature which is extended in space.
In The Quantum Casino it was revealed how nature - at its most basic level - is fundamentally random. The process of measuring a particle's property value was compared to a ball racing around a roulette wheel: the final state is randomly selected, and only certain values are allowed (the slots on the roulette wheel). Before observation, the particle's property value must be considered as being in a superposition of all possible states (equivalent to the ball racing around the roulette wheel).
In Quantum Entanglement it was revealed that when two particles interact they form a single "entangled" state. You can no longer talk of the wavefunction for just a single, localised particle, you have to talk of one single wavefunction for the entire system. The discussion on Bell's Inequality showed that particles are not localised in space, and do not possess fixed characteristics ("hidden variables"). There is a strange connection between particles which instantaneously informs an entangled particle of any type of measurement performed on its partner particle (this may be counter-intuitive, but it is not as surprising as it might seem as we have already shown that duality between a particle and a spatially-extended wavefunction).
In Quantum Decoherence a solution was presented for the apparent "collapse" of the wavefunction to a single eigenstate. If the components of a superposition state are to produce interference effects (as seen in the double-slit experiment) they must be in phase (must be coherent). What happens to a quantum particle in the real-world - a particle which is no longer isolated in space as it is in the double-slit experiment - is that each of its component states gets entangled with different aspects of its environment. As seen in the page on Quantum Entanglement, when particles become entangled you have to consider them as one single, entangled state. The phases of these states will be altered. This destroys the coherent phase relationships between the components. The components are said to decohere and the interference effects no longer appear.
The Copenhagen Interpretation
Now we have a good picture of behaviour at the quantum scale, we can start to ask more philosophical questions about the nature of quantum reality ("ontology").
Because the theory of quantum mechanics is only concerned with the accurate prediction of the results of experiments, it says nothing about any underlying mechanism which produces those results, i.e., it says nothing about the deeper quantum reality. This has left the door open for several competing "interpretations" of what those results say about the underlying reality. But one thing all the different interpretations must have in common is that they all predict exactly the same observable phenomena.
The most common interpretation of the results of quantum mechanics is the Copenhagen Interpretation. It was developed around 1927 by Niels Bohr, Werner Heisenberg and other collaborators, and named after the city where they often met. According to this interpretation, when a particle is not being observed all we have is a mathematical formula (the wavefunction) representing the knowledge we have of the probability of finding the particle after we take our observation. When we observe the particle, the wavefunction "collapses" and we perceive a localised particle. But the crucial thing is that this interpretation says nothing about what the particle is doing when we are not observing it. Indeed, such a question would be considered "unscientific", and the responsibility of philosophy. (For an hilarious - but surprisingly accurate - comparison of the Copenhagen Interpretation and Deal Or No Deal, see here).
The authors of the Copenhagen Interpretation were heavily influenced by the philosophy of positivism which was highly fashionable in Europe at that time. According to positivism, "the true laws of nature should involve only such quantities that can be observed". One should not waste one's time seeking the answers to unanswerable, deeper questions. Results such as the Heisenberg Uncertainty Principle seemed to suggest fundamental, insurmountable limitations on what we could ever determine about underlying quantum reality (see the roulette wheel analogy in The Quantum Casino for more about limitations on our knowledge about deeper mechanisms), so we should not ask the questions about reality if there was no way we could ever find the answer.
In taking this approach the Copenhagen Interpretation neatly sidesteps any philosophical questions such as "Does the electron exist before we observe it?". But there is a price to be paid for this apparently very neat tying together of the loose ends. In fact, there are a couple of nasty implications of this interpretation:
- Firstly, it requires this peculiar "collapse of the wavefunction" which apparently relies on observation. This might be taken to be a real physical process, or an "increase in our knowledge", but these precise details were left unexplained.
- Secondly, the interpretation effectively denies the existence of an deeper, objective reality that exists in the absence of observation.
This should all have been highly contentious. Nick Herbert considers the objections in his book "Quantum Reality": "From the results of experiments carried out in the twenties, how could Bohr conclude that no future technology would ever reveal a deeper truth?". However, it could be said that the advocates of the interpretation did such a good sales job that the Copenhagen Interpretation went largely unchallenged for many years, reprinted in text books as science fact, and is still the most widely-accepted interpretation among physicists. But still not everyone was satisfied. The mathematician James R. Newman said: "In this century the professional philosophers have let the physicists get away with murder. It is a safe bet that no other group of scientists could have passed off and gained acceptance for such an extraordinary principle." And Murray Gell-Mann said: "Niels Bohr brainwashed a whole generation of physicists into believing that the problem had been solved".
So let's dig a bit deeper ...
Beyond Copenhagen
We're now considerably wiser about the first problem with the Copenhagen Interpretation: as explained in detail in the page on Quantum Decoherence, different components of the quantum superposition form entanglements with the environment. Components which are out-of-phase coherence just dissipate into the wider environment. That seems a reasonable explanation for the apparent "collapse of the wavefunction". So let's concentrate on the second nasty implication of the Copenhagen Interpretation. Especially as this website is designed to consider questions about the nature of reality, let's concentrate on this principle of the Copenhagen Interpretation which denies the existence of an objective independent reality that exists in the absence of observation (or measurement).
Firstly, we've got to define what we mean by "observation". Do we limit this to mean "conscious human observation"? Surely not. For example, a radioactive uranium nucleus buried in rock on a distant planet will decay to emit an alpha particle. It does not matter if a human observer looks at the rock or not. As Carver Mead agrees in this excellent American Spectator article: "That is probably the biggest misconception that has come out of the Copenhagen view. The idea that the (human) observation of some event makes it somehow more 'real' became entrenched in the philosophy of quantum mechanics. Even the slightest reflection will show how silly it is. An observer is an assembly of atoms. What is different about the observer's atoms from those of any other object? What if the data are taken by computer? Do the events not happen until the scientist gets home from vacation and looks at the printout? It is ludicrous!".
"I like to think that the moon is there even when I am not looking at it."
- Albert Einstein
Clearly, "measurements" must somehow be taking place all the time and do not require conscious observers. Instead, let us describe a "measurement" or "observation" as the process which produces a single property value from a state which was previously in quantum superposition, i.e., we now define a measurement to be the process of quantum decoherence which reduces the superposition state. In this case, any connection with the environment could produce a measurement. However, for all interference terms to disappear, i.e., for decoherence to be complete with the object no longer in a superposition state, the particle must make some macroscopic effect. This is described in the book Quantum Enigma: "Whenever any property of a microscopic object affects a macroscopic object, that property is 'observed' and becomes a physical reality". For example, if we use a macroscopic photon detector to detect the photon in the double slit experiment then that will destroy the interference pattern. So as long as there is a macroscopic effect from a quantum entity, that object can be considered to be "observed" or "measured" - no need for a conscious human observer.
OK, so now we're getting somewhere, digging a bit deeper than the Copenhagen Interpretation. We've got a better understanding of the "collapse of the wavefunction", we've defined what constitutes an "observation", so all we now have left to consider is what we can say about the state of the system before observation; specifically, do we have an independent reality that exists in the absence of observation? And, if so, what form would that reality take?
Here's what Nick Herbert says on this subject in his book "Quantum Reality": "Little has been said about the character of the unmeasured state. Since most of reality most of the time dwells in this unmeasured condition, which quantum theory represents by an uncollapsed superposition of possibilities, the lack of such a description leaves the majority of the universe (everything that's not currently being measured) shrouded in mystery".
We've got a few clues as to whether reality exists before observation. For a start, not all particle properties are in superpositions, subject to the quantum formulation. For example, an electron's mass and electric charge (so-called static attributes) have well-defined properties - they are not in a quantum superposition. Here, then, is objective reality without observation. The particle is there, and its properties have values. It's only the properties which can alter (the so-called dynamic attributes) such as position and momentum do not behave in the same manner - all dynamic attributes are subject to the quantum formulation. These quantities are in a superposition state before measurement.
So if there is any reality before observation, it would have to embrace the possibility of multi-valued properties. We now are beginning to get hard experimental evidence of this real multi-valued nature of reality. A team from the State University of New York and the Technical University of Delft have delayed quantum decoherence by isolating a quantum system from the environment and, as a result, they created a mesoscopic (in-between microscopic and macroscopic) electric current flowing through a superconducting ring in opposite directions at the same time (see this article by Tony Leggett).
So now we're saying that quantum superposition might, in fact, be a superposition of many real particle properties. In which case maybe there's more to this wavefunction thing (which describes the superposition) that meets the eye ...
In the Copenhagen Interpretation, the wavefunction is treated as nothing more than a useful mathematical measuring tool, used for calculating the probabilities of finding a particle. The wavefunction is not considered to have any reality, i.e., it does not exist in this universe in the same way that a light wave, say, exists. It is purely a mathematical entity. But maybe the wavefunction is more than that. On the basis of this discussion so far, maybe we should now understand the form of the wavefunction as describing "reality before observation". Certainly, it would appear that the wavefunction is more just a simple probability wave giving the probability of finding a particle in a particular position. The wavefunction can introduce interference effects (seen in the double-slit experiment) but probabilities can never be negative (and so can never produce interference). Refer back to the form of the wavefunction derived in the page on The Quantum Casino:
It can be seen from this result that the wavefunction has the form of a wave in complex space, and it has a phase value in the complex plane. It is this phase value which introduces the interference effects. The wavefunction appears to have a structure - it's certainly more than a simple probability. So now we're considering the wavefunction as describing "reality before observation". This is the conclusion of H. Dieter Zeh in his paper The Wave Function: It or Bit?: "Bell's inequality has allowed experimentalists to demonstrate that reality is non-local. So why not simply accept the reality of the wave function?" This makes a lot of sense: if the wavefunction is a mathematical model then it must be a mathematical model of an underlying mechanism. You do not have a functional model without an underlying mechanism. Surely a mathematical model does not exist on its own - it models something real. Even if we do not understand that mechanism, the wavefunction can provide us with a good understanding of its structure.
It's interesting to compare the wavefunction to television signals for many channels, which are permeating our everyday environment. Just because we can't see the multitude of signals does not mean they are not there, are not real. When we tune-in our televisions we can display just one of the channels, "bringing it into our physical reality" (the equivalent of selecting a single quantum measurement from a superposition). But the key thing is that the television signals were always real.
So now we have an answer to the last nasty implication of the Copenhagen Interpretation: there could, indeed, be an objective reality which exists in the absence of observation, and that reality would be described by the wavefunction. Which leaves only one problem: if the wavefunction is the true description of reality, then that reality is described in complex space. Clearly what we're dealing with here is a conception of reality which is very far removed from our everyday conception of what constitutes reality. This idea of there being a discrepancy between our human conception of reality and what, in fact, appears to be the true picture of reality is a recurring theme (see this New Scientist article).
Things are getting weird ...
Hidden Variables Theories
As discussed in detail on the page on Quantum Entanglement, Albert Einstein was one of the physicists who rejected the Copenhagen Interpretation and its insistence that there was no deeper quantum reality. Einstein considered quantum entanglement of unmeasured pairs of particles separated by a large distance. As soon as one particle was measured, quantum theory required an instantaneous transmission of particle property values to the other entangled particle (Einstein called it "spooky action-at-a-distance"). Such faster-than-light (superluminal) communication violated Special Relativity. Einstein considered this to be unacceptable, and argued that the particles must have possessed the property values already, albeit hidden from our view in some deeper level of reality. These property values (referred-to as hidden variables) only emerged into physical reality when a measurement was taken.
However, this would mean the particles possessing more information than quantum theory said they should have. If particles had hidden variables then quantum theory was wrong.
In 1932, John von Neumann published his definitive analysis of quantum theory, Mathematical Foundations of Quantum Theory. In that influential book, von Neumann showed that if electrons are ordinary objects with inherent properties (which would include any hidden variables) then the behaviour of those objects must contradict the predictions of quantum theory. At the time, Von Neumann was considered the greatest mathematician in the world and his result effectively killed-off hidden variables research for two decades.
However, in 1952 David Bohm showed that hidden variables theories were plausible if the restriction of locality was relaxed - essentially allowing faster-than-light communication (see here for a technical explanation of Bohm's findings).
Bohm illustrated his theory with the example of an undetectable, non-localised pilot wave which could explain the double-slit experiment. The pilot wave guides a single, real electron (i.e., the electron is never in a quantum superposition, it is always an "ordinary object"). The pilot wave guides the electron through just one of the two slits in the double slit experiment (see here) - none of this "going through both slits at once".
The guidance of the pilot wave is the cause of the interference effect when the electron reaches the screen. This is achievable because the pilot wave which is a special entity - it is in touch with every other particle in the universe (hence it is completely non-local). While this is peculiar, it does mean the electron is never in a quantum superposition state - it is always a real, ordinary object. The pilot wave is also a "real" wave (i.e., more than just a mathematical tool like the wavefunction, it is as real as a light wave - albeit undetectable!).
So both the pilot wave and the electron are real objects which together can describe quantum behaviour with no need for quantum superpositions.
Bohm generalised this pilot wave example to propose an holistic hidden variables theory. Bohm suggested the universe was a form of "hologram" called the Implicate Order, each point in the Implicate Order containing all the information about the universe (just as in a hologram - see here).
Veiled Reality
For the final part of our discussion of quantum mechanics, let's consider what would be involved in constructing a generalised hidden variables theory to examine the principles involved.
We've just discussed how the wavefunction could be considered to represent "reality before observation", with particles having multi-valued properties. If that is the case, why do we not see this multi-valued properties in our physical reality? When we perform a measurement of a particle property we only obtain a single value. Therefore, a hidden variables theory would appear to require some sort of mechanism or structural feature for hiding this multi-valued nature of reality from our eyes. How can this be so? Well, it might be due to the way in which we define our reality.
Bernard d'Espagnat has described a "veiled reality" - a deeper layer of reality - whose form is quite different from our human notion of reality (which he refers to as "empirical reality"). Our empirical reality could be thought of as a "World of Particles" (my term - see the diagram below). Because our measurement apparatus are themselves composed of point-particles (particle accelerators are themselves composed of particles and used to detect particles), this would explain why the multi-valued nature of reality is hidden from our view. We can only detect particles. The problem is the "measurement equipment" of our reality (including our own eyes - everything in our reality is defined as being composed of particles).
This imposes a structural limitation on what we can know about the veiled reality layer. In fact, we cannot interact with the veiled reality directly, we can only infer some clues as to its structure (I have denoted the structure of the veiled reality on the diagram below as some form of black network - don't think I know the real structure!). If we inhabit a "World of Particles" then the deeper veiled reality could be thought of as the "World of Wavefunctions". We can only infer the general structure of the veiled reality (wavefunction) - we are fundamentally incapable of interacting with it directly or knowing its details.
(Note on the diagram I have defined a barrier I have named the Firewall (based on the computing "firewall"). Like the computing firewall, it is not a physical barrier, rather it designed to fundamentally restrict the flow of knowledge in one direction. It is an inevitable consequence of the veiled reality layer.)
The particles seem real and tangible to us because of the rather vague way we define physical reality: we define real objects in terms of other objects which we already consider to be real. For example: "I know the apple is real because I can hold it in my hand" - the apple is considered to be real because of the assumed reality of the hand. That's the best definition of physical reality we can ever possess, a rather circular definition. Similarly, in our world of particles we can perform experiments on particles with equipment made of particles, but they will be limited to telling us only information about particles. We will never be able to generate information about any reality beyond our physical reality using these methods. Here's what Austrian physicist Anton Zeilinger has to say about this circular definition of quantum reality, and the resultant "firewall" effect: "This world is not directly ascertainable or describable. Because every description must be done in terms of the information, and so you inevitably get into circular reasoning. There's a limit we can't cross. And even a civilisation on Alpha Centauri can't cross it. For me that's something almost mystical." (See here).
We do not really understand the real nature of wave/particle duality. However, even if we do not yet have a full understanding, we at least know what particles are not: they are not localised point particles in space. So why does the "observed particle" approach dominate physics? Clearly, it's because the scientific method places such importance on the outcome of experiment and, while we can detect particles with ease, we are unable to detect the flip-side (wavefunctions) directly.
So maybe we should turn our attention to the type of experiments we are performing. We do seem to place a great deal of emphasis (and money) on particle accelerators. Machines to detect particles. Machine which are themselves made of particles. Is that wise? Or is it just the easy way out. Isn't it easier to spend millions of dollars on creating ever larger accelerators than to admit that we're not dealing with localised particles after all but - as Bell's Inequality proved - we're dealing with spatially extended wavefunctions which we don't understand and cannot directly perceive. (In the book Quantum Reality it is considered if other creatures might be able to "see" wavefunctions: "Is it conceivable that other beings could experience reality differently? Could they possibly directly experience the superposition states whose existence we can only infer?").
In Thomas Kuhn's landmark 1962 book The Structure of Scientific Revolutions, it was argued that scientific thinking goes through revolutions, instead of gradual theory development through testing and experimentation. Maybe the current fixation with particles is merely fashion? Kuhn also questioned whether scientific experimentation is truly unbiased and neutral since the experimenter had previous theories and preconceptions - influenced by his fellow scientists - which could affect what experiments are chosen and the way in which the results are interpreted: "The existence of the paradigm sets the problem to be solved; often the paradigm theory is implicated directly in the design of apparatus able to solve the problem". Surely by using a particle detectors we are biasing our investigation towards a localised view of particles, and away from other approaches? Christoph Schiller agrees: "Observers have to be made of matter; an observer cannot be made of radiation. Our description of nature is thus severely biased: we describe it from the standpoint of matter." (see page 834 of Motion Mountain).
What other clues do we have about the true nature of reality? Well, we know that there is an apparent spooky connection between entangled particles separated by some distance. This "non-locality" can be explained by communication in the veiled reality layer. Remember, this deeper veiled reality layer could be thought of as being outside the jurisdiction of our human laws of physics which only apply to our "World of Particles". There's no problem achieving non-locality (faster-than-light communication) in the veiled reality layer as it the layer below that in which light exists (light (photons) being a constituent of the "World of Particles"). Indeed, Brian Whitworth in his paper The Physical World as a Virtual Reality makes the point that if we are living in a virtual reality generated by a computer (as if we were simulated beings in the computer game The Sims) then non-locality could be easily explained: "The processing that creates a virtual world is not limited by the space of that world, e.g., a CPU drawing a screen is no 'further' from any one part of the screen than any other. All screen points are equidistant with respect to the CPU, so virtual reality processor effects can ignore screen distance, i.e., be non-local. If our universe is a three-dimensional screen its processing is equidistant to all points in the universe, so the non-local collapse of the quantum wave function could be such an effect."
The "hidden variables" mechanism in the veiled reality layer transmit the characteristics between the particles instantaneously. However, we are always fundamentally incapable of accessing those hidden variables in that veiled reality. As Gordon McCabe says in his paper Universe Creation on a Computer: "The computer hardware is inaccessible to the people represented in the computer program".
At the end of this New Scientist article, David Deutsch considers our experimental limitations in exploring deeper reality: "All Deutsch will say about a theory of everything is that it is likely to come from uniting quantum theory and relativity at a more fundamental level than current entanglement experiments allow" (this refers to entanglement experiments such as Bell's Inequality and Leggett's Inequality - see back to the page on Quantum Entanglement). The interviewer then goes on to consider if we should be searching for deeper, hidden reality or just continuing with particle-centred experiments: "Maybe it is time to revisit Einstein's lost quest, if we are serious about uncovering the basic laws of the universe; the money spent on particle smashers such as the Large Hadron Collider certainly suggests we are. Perhaps we need to move quantum entanglement and the nature of reality to the centre of the quest to find a theory of everything. What was once a quirky sideshow may yet prove to be the main event."
There is no such thing as "empty space"
You might imagine that if you pump all the air out of a sealed box so that it contains no particles, you could form a perfect vacuum. However, the equations of quantum mechanics tell us that particles can appear in a vacuum, out of apparently empty space. According to the Heisenberg uncertainty principle, there can be enough uncertainty about the energy at a point,
, to allow the creation of a "virtual" particle, but only for a very short time,
:
This is surely the best possible example of how our particle-oriented conception of physical reality is flawed. The apparently empty space is still capable of producing particles; it is a system which is still described by a quantum state (actually, it is the quantum state with the lowest possible energy: zero-point energy). There is an underlying "veiled reality" layer present determining the quantum state of the system even when we have removed all particles from our "World of Particles". However, that layer is completely undetectable to our eyes and measuring apparatus - all of which are made of particles.
This shows that there is, in fact, no such thing as our intuitive concept of "empty space" in nature. The concept of "empty space" is purely a human invention.
Finally, a return to determinism?
Now we have defined the concept of a "veiled reality" we might even be able to cast some (extremely speculative) light on the probabilistic nature of the wavefunction. It has been suggested that at the very small Planck Scale (10-35m), quantum fluctuations become powerful enough to twist and turn the geometry of the Universe. Space and time break down into random "foam":
Maybe the random selection of a quantum state during wavefunction collapse is a result of this apparently random structure. Or maybe the selection process occurs in the veiled reality, hidden from us. What appears fundamentally random to us might actually be pseudo-random (i.e., deterministic!) at the Planck Scale or in the veiled reality "processing" (as suggested by Gerard 't Hooft - see this Nature article or this New Scientist article). Either way, the process would be completely hidden from our eyes. According to Jim Al-Khalili in his book "Quantum": "The uncertainty principle becomes now just a statement about our inescapable ignorance."
"God does not play dice", said Einstein, believing that quantum physics was incomplete, some deeper theory being able to predict outcomes with certainty. Maybe one day Einstein will be proved right.
Comments
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In the movie, at one point Neo knows and understands the veiled reality, visualized by seeing everything in 'matrix code' (a visualization of 'understanding the quantum foam'), which gives him 'superpowers' (the fast 'downloading' of knowledge portrayed in the movie is more or less a metaphor to the 'faster than light' communication that you attribute to the veiled reality.) - Ivo Jansch, 5th January 2007
I think David Bohm's "Implicate Order" is also very similar to the Veiled Reality/Matrix. Bohm's "Implicate Order/Explicate Order" would correspond to the "World of Wavefunctions/World of Particles" described in my article. - Andrew Thomas, 5th January 2007
On the subject of the double-slit experiment, John Wheeler's Delayed Choice Experiment - see http://en.wikipedia.org/wiki/Wheeler's_delayed_choice_experiment is a useful modification to the double slit experiment because it introduces so many different aspects of quantum behaviour.
Firstly, the experiment shows that idea of particles as isolated points in space is inaccurate: as explained in the main article above, "reality before observation" is described by a wavefunction. Wavefunctions, unlike particles, are extended in space and so can pass through both slits at once.
When an observation is made, the wavefunctions of the particle and the observing equipment become entangled (i.e., form an entangled state - see http://www.ipod.org.uk/reality/reality_entangled.asp ). The behaviour and appearance of the particle (is this a particle or a wave?) is determined by this entangled state (i.e., the wave/particle behaviour of the particle is not independent of the observing equipment, rather the type of observing equpiment determines behaviour). For example, if a screen is used to detect particles, the wavefunction of the screen (which is, in itself, an entangled state of all the particles which comprise the screen) allows the interference pattern to appear. But if a single particle detector is used, the wavefunction of the detector only allows the registering of single particles. In that case, the interference superposition effects do not appear. Instead they dissipate into the environment through decoherence - see http://www.ipod.org.uk/reality/reality_decoherence.asp
Some have suggested that the Delayed Choice experiment implies some sort of backwards causality in time (see http://www.ipod.org.uk/reality/reality_backwards_causality.asp ): if the particle is detected by the screen or a single detector then some sort of signal has to travel backwards in time to tell the particle to act as a particle or wave when it travels through the double slits. But I believe the process I have just described shows no backwards causality is required. - Andrew Thomas, 7th January 2007
My eternal gratitude! - DJ Fadereu, 22nd March 2008
even if we believed that the wavefunction is a model of that veiled reality, all models by its very nature are false. the same way that the reflected image in the mirror is not the source of the image itself.
the eye can see everything escept itself. it has to look in the mirror to see waht it looked like. but then again, what the eye see is not itself but its reflected image.
my two cents.
nice work though. never read anything explained quantum stuff so clearly.
- hybrid, 23rd July 2008
If we all would vibrate in one direction, reality whould unfold as we wish.
No idea about Math. But I do live in Amsterdam. Einstein theory of relativity and me are good pals
:) - Caveman, 10th November 2008
This paper on quantum mechanics by John Boccio ends with a similar analogy: "Until then, like ancient cave dwellers, we can only stare at the shadows of quanta flickering on the walls of our cave, and wonder what they mean." http://www.ipod.org.uk/reality/reality_boccio3.pdf - Andrew Thomas, 24th November 2008
On a "bias" towards particle-oriented physics:
Even though the idea of localized particles has been empirically verified to be an incomplete view, they are nonetheless observable. Just as Newtonian physics is still carried out and produces useful results, a complete picture of the (very real) particles in the universe (even if it is only our "Sims" universe), is surely the the next important part of the picture. QM doesn't preclude deeper understanding of the origins of our (Sims) universe, nor does it preclude answering the question as to the end fate of the universe.
There *might* in the future be results which further limit the utility of particle physics to answer these questions, but I don't get how you have reached the position that this boundary may have been reached. Imagine what the Sims could do if they knew how the Sims world worked! Sure, they couldn't build PCs in our world, but they might come up with kitchens that don't catch fire all the time(The analogy is unravelling here :D ).
Seems to me they are right to continue the search to complete The Standard Model.
Besides, physics isn't metaphysics quite yet: what can you do with something you can't do anything with? Particle physics is modern physics because the empirical results dictate that we can observe characteristics of particles. All theories are incomplete...
I don't mean to overly criticize an excellent resource, but because it IS an excellent resource (that I think more and more people will visit), perhaps you could consider modifying those opinions in the article, as I believe it is opposite to your intention to give the impression that scientists are wasting their time. Particle physics, as all good science, needs public support. - Dave H , London, 10th January 2009
I certainly don't want to discourage any scientific research. Do you think this page is opinionated? It might sound that way but I just think it's just factually accurate. There's plenty of positive coverage in the media about the search in particle physics for a "Theory of Everything", and that is how it is presented to the public. And that coverage inevitably helps projects like the LHC continue to get huge funding. So I think there should definitely be room for one site like this one which points out that a theory which describes just particles and the basic forces is by no means a "Theory of Everything".
So particle physics gets plenty of positive coverage on websites. However, I feel the presentation on this website considers particle physics in a wider context. There's only one thing for sure about what to expect from the experiments at the LHC, and that is that it cannot find a "Theory of Everything"!
Thanks again, Dave. - Andrew Thomas, 12th January 2009
GPS would cost who knows what (if it were feasible at all) without automatic adjustment for relativistic effects, Antimatter gave us PET scans, QM applications are already being explored (more powerful computing for one)... All publically viewed as "esoteric" science, but actually having fairly ubiquitous, everyday applications.
Truth is, no-one knows yet what will come from completing the Standard Model - but it will probably pay the human race back plenty.
The impression that could be taken from this article is that "since LHC can't give us ToE [which it can't as you rightly say], why are we spending the money?" Perhaps the ToE aspect is oversold in the media - it sounds sexy. ToE is of course only what physicists dream of however, it isn't the sole purpose of science.
Not so much opinionated, as seeming to imply that high-energy physics can't lead to any *practical* applications. I think that omission is all I really take issue with. - Dave H, London., 12th January 2009
But there has to come a limit, both in money and physical resources. I would expect the LHC to be the last of its kind - we can't go on building bigger forever. A bit more ingenuity and imagination must now come into play. Something like this: http://physicsworld.com/cws/article/news/3215 using gamma ray bursts to provide insights into quantum gravity at energies "far beyond existing accelerator technology". - Andrew Thomas, 13th January 2009
"Einstein, do not tell God what to do!" said Niels Bohr
Interesting discussion, to which I would add my own two cents:
"OK fine, but if YOU were God, HOW would YOU construct a Universe?" asks Me.
It's an important question, perhaps the most important question of them all.
I believe on the smallest scale, that yes Einstein is right and the Universe is deterministic. HOW that works exactly, I do not know, yet I take very small comfort that neither does anyone else.
There is no shortage of theories however, in particular that General Relativity rules down to the smallest scale, which is completely wrong.
I have my own pet theory, which I will not reveal at the present time until I work out the math, but yes it does consider Quantum Physics and Relativity as well.
I read Nick Herbert's book btw, and was a bit unimpressed. There is much speculation in it, and a bit too much philosophy. It is however a good starting point to understand this page and the pages that follow.
- Gregory Sivco, 6th March 2009
The good news is reality exists. The bad is it's even stranger than people thought
http://www.economist.com/science/displayStory.cfm?story_id=13226725
Another link:
http://www.sciencedaily.com/releases/2009/03/090304091231.htm
So is there an objective reality, if no measurement is made?
- wang, 14th May 2009
http://www.ipod.org.uk/reality/reality_hardys_paradox.asp
That multi-valued nature of reality is described in the main text of this page.
Thanks a lot, Wang. - Andrew Thomas, 17th May 2009
For instance:
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Christoph Schiller agrees: "Observers have to be made of matter . . . . Our description of nature is thus severely biased: we describe it from the standpoint of matter." (see page 834 of Motion Mountain).
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No. That (surely) is what we think we're doing. But, of course -- as old man Descartes pointed out -- we do no such thing, because we can't; the world we 'observe' is, very precisely, the immaterial world of qualia, of sense-impressions, of experiences: of thought.
Let us try considering not two worlds, one which we think we see but which is actually an (incorrect) abstraction from the 'real world'; instead, let's point out that the world we perceive with our minds has just as much 'right' to be proposed as 'real' as the one we try to examine via Large Hadron Colliders.
Let's ask whether, in all the time we've been looking for (and trying to avoid) the Ghost in the Machine, we've really been looking for the Machine in the Ghost, and that neither has any right to be thought of as supreme, or real, or anything else.
I am not being to the slightest degree mystical, or 'pan-psychical', nor anything else of that nature.
I think -- having read you thus far -- that observation by the mind is quite separate from, though closely linked with, observation via macro-machinery; that waveform collapse does occur, and I'd like to know when and in what exact circumstances (I suspect it's at the interface between the material and the mental world, though at which side of that interface I'm unsure); that there's no such paradox as action-at-a-distance and that Schrodinger's pussy-cat is never in any kind of superposition of being alive or dead; and most particularly that we can use the methods of experimental physics (particularly as they're being used now, according to the references you have given us) to get a long way towards giving us a picture of Reality, just as long as we ask the right questions of our experiments. - Martin Woodhouse, 22nd May 2009
To me, what I just said was both true and uncomplicated, but transferring my thoughts into words, using semantics, took much greater effort. Niels Bohr complained all the time about semantics being a road-block to understanding. He should know, he muddied the waters quite a bit with his "Complementarity" principle, which John Stewart Bell mockingly called "Contrariness."
So, let's dip into the semantics pool, and see how wet we get, shall we? As so:
"Measurement" need not be destructive. Often it is though. If I ask the double-slit experiment to please locate an electron or photon on a screen it will do so, whether or not I am in the room to "observe" it or not. Whenever any 2 particles interact, for example a positron and electron meeting and annihilating each other (converting matter to energy) a "measurement" is made, from the standpoint of the positron and the electron, as well as from the standpoint the photons created by their destruction. Whether or not a human observes this annihilation/creation is moot, the measurement still occurs. I find it comforting to think of humans as third-party "observers".
"I would like to think the moon is still there when I'm not looking at it" ... Albert Einstein. - Steven Colyer, 22nd May 2009
we really can't assume that measurements create reality because it is possible to erase the effects of a measurement and start again."
I try to get a glimpse of the truth of the "Universe". I am confused, does reality exists, does weak measurement states, "reality is not created by measurement", as most QM scientists think. - Wang, 24th May 2009
When we measure a particle's position, say, then we find a single value for its position. So that particle's position only becomes real (i.e., fixed value) after observation. But the particle is undoubtedly real (i.e., it has mass, charge) at ANY time. We just can't say where it is. - Andrew Thomas, 25th May 2009
I'm very interested in these pages, I'm currently studying QM as a hobby. I wanted to know everything there is to know and got "lost" in wikipedia and friends. I've read this brilliant article by John G Cramer, http://mist.npl.washington.edu/npl/int_rep/tiqm/TI_toc.html which should be familiar to you. I would really like to see a page about TIQM here :-)
As an aside, I'm planning on teaching interested friends/family about QM and your pages are a very nice popularisation of current knowledge. I'll bookmark and remember this place, thanks for your efforts! - Merijn Vogel, 25th May 2009
I'll just quote Michael Lockwood from his book "The Labyrinth of Time": "This approach may seem promising. But detailed analysis has revealed that the requisite pattern of cancelling and reinforcement could not occur within any of the cosmological models that are consistent with our current knowledge. Indeed, for some of the models that, given the available astronomical data, remain in the field, the absorber theory predicts a net preponderance of advanced instead of retarded radiation. Though neither Wheeler nor Feynman appears ever to have acknowledged the fact, their absorber theory, ingenious as it is, has become a dead duck."
Thanks again. - Andrew Thomas, 26th May 2009
One or two questions: on several occasions (e.g., Hidden Variables Theories box above) you mention that a particle would have more information than QM says it can.
What does it mean to say a particle has information? What limits the information a particle can have?
Thanks again.
- John Hidley, 27th May 2009
By the way, I'm sure you know who Carver mead is (feel free to Wiki him up if you don't). The link below is a 15-min or so (to read) excellent interview with him. I strongly recommend reading it. He obvious dislikes Bohr and the whole Copenhagen school. Here's a sample:
What's the problem with [point particles]?
Because point particles are assumed to occupy no space, they have to be accompanied by infinite charge density, infinite mass density, infinite energy density. Then these infinities get removed once more by something called “renormalization.” It's all completely crazy. But our physics community has been hammering away at it for decades. Einstein called it Ptolemaic epicycles all over again.
Hold on...epicycles?
Ptolemaic astronomers assumed that the earth was at the center. But then it became more and more complex to calculate the orbits of visible planets. When you assume the earth is the center, you have to add epicycles to the existing orbits to adjust them. In the same way, when you assume photons are point particles, and all you can calculate is probability, you have to add epicycles of conceptual nonsense to “explain” even the simplest experiment.
So when results don't fit theory. . .
The theory has to be adjusted, with band-aids stuck on top of one another. This happens all the time with science, but especially with the statistical quantum theory. It takes enormous work to take that theory and work it into a form that is useful for anything except those questions that it was initially devised for. And the band-aid epicycles are then announced as a triumph for the theory. It's amazing how long they have gotten away with it. - Steven Colyer, 27th May 2009
http://laputan.blogspot.com/2003_09_21_laputan_archive.html - Steven Colyer, 27th May 2009
I think this may seriously re-write the quantum mechanics. There does have something more fundamental than "measurement cause sth from multiple eigenstates to one eigenstate."
It implies the world does function objectively if no measurement is made. (it is beyond just charge, mass, the world is running someway in step by step). The quantum uncollapse weak measurement can also reverse the measurement. it is also a time machine to me!
Andrew or other, please comment, this totally challenges the common quantum mechanics theories. thanks - Wang, 31st May 2009
My initial feeling is that there is nothing prohibiting some form of reversal of the wavefunction collapse - at least in theory. As discussed on my Quantum Decoherence page, decoherence (wavefunction collapse) can be considered from an "increase of entropy" viewpoint: things tend to get more disordered, and this is effectively irreversible (e.g., considering entropy increase, the molecules of a gas trapped in a container will more than likely spread around a room when released, but it is highly unlikely that they will all spontaneously return to the container). But there is NOTHING FUNDAMENTALLY prohibiting the molecules of the gas returning to the container - it is just highly unlikely. Same with wavefunction collapse: there is nothing fundamentally prohibiting the process from reversing itself - it would not break any laws of physics - but it would be highly unlikely. So if someone has experimentally found a way to reverse the collapse I'm not totally surprised.
As I said on that Quantum Decoherence page: "We therefore only see the collapse of the wavefunction operating the forward time direction (for the same reason we don't see broken eggs mending themselves)." But, theoretically, a broken egg COULD mend itself - it is just a highly unlikely occurence.
And, as Nadav Katz says in that Science Daily link you posted, being able to reverse the collapse "tells us that we really can't assume that measurements create reality because it is possible to erase the effects of a measurement and start again."
Thanks a lot, Wang. Your comments are excellent and helpful. - Andrew Thomas, 31st May 2009
How can we surmise that an electron's mass and charge have an objective reality without observation if we have to observe their mass and charge in order to deduce that it remains static? If we weren't 'observing' these properties how would we know that they don't alter and furthermore how can't we consider that these properties may have been in a quantum state that collapses upon observation? - Hion, 26th June 2009
But, yes, I suppose that philosophically speaking we have no knowledge of anything between observations. But we also have no evidence that a particle's mass ever varies. So **for all practical purposes**, we can treat a particle's mass as fixed. Whereas we have to use the quantum formulation for other practical purposes. I think that's the key thing: does it have a practical impact.
But, yes, philosophically you are correct. - Andrew Thomas, 26th June 2009
I have to be honest - I think "consciousness" is just an emergent property when those billions of neurons in our brain start working together. I don't think it's anything magical. People with degenerative brain diseases slowly lose their awareness as they lose neurons. It's a progressive, emergent thing - at least that's how it seems to me. I don't subscribe to the idea that the observer has a special role in quantum physics either, that the observer is essential to "collapse the wavefunction". As I say in the main text of this article: "For example, a radioactive uranium nucleus buried in rock on a distant planet will decay to emit an alpha particle. It does not matter if a human observer looks at the rock or not."
However, that doesn't necessarily mean that human intelligence does not play a very special role in the universe, as you will see on my "Intelligent Universe" page. - Andrew Thomas, 26th June 2009
I think if science is to proceed at all, then we have to make some basic assumptions which seem to be very safe assumptions. Of course, those assumptions **might** be flawed, but it seems incredibly unlikely. So we can say that it is **extremely** likely that the uranium nucleus will decay even though no one is watching it. And that is good enough for me.
Ask yourself, do you have any evidence that my assumption that a human observer is not required is wrong? I have plenty of evidence that it is correct. - Andrew Thomas, 28th June 2009
For the tree falling in the woods, again, I would suggest it behaves in exactly the same way whether or not a human is observing it. You might define the emission of "sound" as requiring a human observer, but in this case all we are interested in is the behaviour of the tree, so I would say it is enough if the tree emits a sound wave through the air - even if no one is listening. And from our knowledge of physics there is nothing to suggest that the tree does not always emit that wave through the air when it falls. To suggest otherwise would be to suggest that the compression of air behaves differently when there is no human standing nearby - that seems bizarre.
I think if you take a very philosophical approach (as you are) of saying that there is simply no reality at all without human observation then that is a very different, more profound approach. I deal with that later on this site (for example, the "Brain In A Vat" scenario considered on the "Living In The Matrix" page). For the time being we are only considering basic physical behaviour: quantum behaviour, and trees falling, and I would definitely suggest that these things behave in exactly the same way whether or not a human is in the room. - Andrew Thomas, 30th June 2009
Also proven wrong since the 1st half of the 20th century:
- Schrodinger's Cat - The kitty is either alive or dead, not both at the same time.
- Quantum Leaps - Electrons do make smooth transitions from one orbital state to another, although granted they do it very, very fast. Rutherford's lab in Edinburgh simply didn't have the technology in 1913 to show that, so Niels Bohr assumed instantaneous leaping which works fine mathematically and seemed to be backed up but the experimental results of the day. His famous 1913 paper is still more right than wrong even if it was a bit ad hoc - it pushed Physics forward considerably.
- The book: "The Tao of Physics" - The science is 100% speculative and 100% wrong, but it still sells well. Please avoid this one with a ten foot pole. - Steven Colyer, 4th July 2009
http://laputan.blogspot.com/2003_09_21_laputan_archive.html
"That is probably the biggest misconception that has come out of the Copenhagen view. The idea that the (human) observation of some event makes it somehow more 'real' became entrenched in the philosophy of quantum mechanics. Even the slightest reflection will show how silly it is. An observer is an assembly of atoms. What is different about the observer's atoms from those of any other object? What if the data are taken by computer? Do the events not happen until the scientist gets home from vacation and looks at the printout? It is ludicrous!"- Andrew Thomas, 4th July 2009
I've a comment about your assumption. You write "Clearly, "measurements" must somehow be taking place all the time and do not require conscious observers."
How can you make that assumption? We don't know what happens if a conscious observer is 'not' observing. What we know is that - using your example - a radioactive uranium nucleus will decay to emit an alpha particle. We know that because we can observe (measure) it. However, we don't know whether the same process would take place if there wasn't a conscious observer. We cannot not observe!
- Kai, 12th November 2009
first of all thanks for the very interesting articles on QM. I read it with pleasure. I read through the various comments and it is interesting to see how vivid this topic is.
I read the communnication between you, Kai and Hion. I like to share my view:
If you open the box after a week, you know nothing about any decay until you measure/observe. You will only be able to measure decay by KNOWING (requires measuring) the state before closing the box and after opening it again. So you need to measure. If an independent person, who knows nothing about the state it was in before you closed the box, opens the box, what will he measure without having any reference ? He can't proof any decay unless he would be aware of the state before the box was closed? right ? Putting a counter in the box would not help either as long as he can not reference to anything. And at the moment he would have a reference, then it implies immediately that he has knowledge about the state before closing the box, which could only be retreived by measuring.
To get evidence, measurement is a requirement. Measurement requires human interaction and human interpretation.
I am interesting to learn about your evidence that a human observer is not required. To my opinion, reality exist, because I exist. So what is the sense behind reality if I would not exist, if there would not be an observer ? Things I can not see/sense, obviously do not 'matter(ialize)' to me and are as such not part of my reality. (like what Einstein said about the moon) Yes I know this goes deep, but so does QM.I think a different level of thinking is required to catch were QM is all about.
Looking forward to discuss.. - Harold Stevens, 16th December 2009
Thanks for your comment. Yes, absolutely we have to measure the item in the box, and that does indeed require human intervention. However, that is not really the question here. The question has been asked if anything happens at all without human observation, or does absolutely nothing happen unless it is observed by a human. I just think it is a nonsense to say that nothing happens at all unless it is being observed by a human, and Einstein agreed when he said "I like to think the moon exists even when I am not looking at it".
If have some uranium, we could measure its radioactivity before putting it into the box. Then a few weeks later we could take the uranium out of the box and measure it again, at which point we would find that some of it had decayed. From this, the most obvious deduction would be that the uranium decayed in the box over the period of a few weeks even when we were not looking at it.
The later part of your question - asking if perhaps nothing at all exists, if you are living in a dream - is the idea behind solipsism and goes beyond the scope of this page. That is a philosophical question which really goes beyond the normal question about human observation in quantum mechanics. I consider ideas like that on the "Living In The Matrix" page (see the menu at the top of this page). - Andrew Thomas, 16th December 2009
After opening the box and measuring the decay, you say you have the proof that the nucleus decayed ?without observation'. This is of course true, if you consider time as something that exists without observation, without measuring as well.
But we are talking QM here. This ?period of time' where the nucleus was decaying ?while we were not watching', only becomes reality, at the moment we decide to turn back to the box, open the box and measure the decay of the nucleus. Unless we do not decide to open the box, to observe and to measure the decay, this ?period of time' (the few weeks we were not observing/measuring) does not exist yet. This ?time' is ?on hold' or collapsed until the moment of measurement (interaction/observation etc).
The ?time', or ?reality' that is required for the decay process, will only unfold when you interact, when you measure.
Time is the trap here. We introduce time and create reality at the moment we measure. Our body is stuffed with senses which are in fact measurement devices. We experience the world, the reality through our senses. We create time and reality as long as we sense (live). If we would not be able to sense/measure, time nor reality would exist. We would not exist.
If you shut down most of your senses like we do during our sleep, under narcosis or in coma, you experience no time, or at least time passes ultra fast..
What would you think if I would say that the decay already has taken place at the same time you put the nucleus in the box ? If you take the time out of the equation, this is the truth? you could imagine it as like time unfolds backwards once a measurement takes place. Or.. history is only then created when measurement has taken place.
Looking forward to your comments on this.
- Harold Stevens, 17th December 2009
Thanks, Harold. - Andrew Thomas, 17th December 2009
Ever studied the double slit Quantum eraser experiment ?
http://grad.physics.sunysb.edu/~amarch/
The outcome of this experiment shows that the measurement result depends on an event that still has to take place, so AFTER the measurement already has been performed?
It shows that the whole experiment has already happened at the moment we start measuring. Once we measure, the whole event unfolds backwards in time.
An analogy: There's a hole in the wall from the bullet, but the bullet has not left the gun yet.
If you like we continue the discussion outside this forum: harold@kpnplanet.nl - Harold Stevens, 18th December 2009
The "delayed choice" experiment is perhaps a clearer example than the example you presented:
http://www.bottomlayer.com/bottom/basic_delayed_choice.htm
I consider this idea briefly in the section "Quantum Mechanics in a Simulation" on my "Living In The Matrix" page. That also includes the link to a New Scientist article:
http://www.ipod.org.uk/reality/reality_backwards_causality.asp
and a link to a recent paper by Stephen Hawking on this subject. I might expand on the idea myself at some point, as this seems to be saying something profound about how quantum mechanics shapes the universe. Thanks. - Andrew Thomas, 19th December 2009