Perhaps I missed it, but I didn’t see any indication from your link that photons can be fired one at a time. They clearly say that individual photons can be observed (these are the lonely dots outside the banding due to random deflections from the edge of the slits). They also say:
But I believe that is a hypothetical and is based on observations of the electron two slit genre.
Punoqllads:
I believe that this is incorrect, to some degree. Please refer to my earlier link where they describe the experimental results with the presence of active field sensors. The interference pattern is only destroyed if you observe the sensor triggers. If the triggers are allowed to fire, but the results are not observed, the interference pattern remains, unimpeded by the field sensors.
Sorry Karl, but I think your original question from the OP still remains unanswered…
It was my understanding that the photons were fired in succession that is one at a time. The significance of course is that it rules out the interaction of electrons as a factor causing interference.
I’m not saying you’re wrong, just that I’m not aware of any photon producing device capable of isolating a single photon. Certainly they performed experiments with very weak photon emitters that showed the distribution effect more clearly, but they never indicate that they did, in fact, shoot photons one-at-a-time through the slits. The point, however is that this is a moot argument, since the effect would be the same.
You lost me there…
BTW, Roger Penrose, in his book “The Emporer’s New Mind”, noted that the wave-particle duality has been observed even with things as big as atoms. (I think this is based on experiments conducted by Louis DeBroglie) He went on to suggest that perhaps even cricket balls would exhibit the same behavior, given the right kind of environment and the right kind of measurement technique. The point is that the behavior is evidently not limited to the electromagnetic spectrum.
JoeyBlades, I’m skeptical of your link to The Reality Program. When he describes the modified electron slit experiments, he doesn’t give much detail on some of the key points. For example, in one experiment, they “mix the data from the slits with additional, irrelevant garbage data, and record the combined (and incomprehensible) data” and “leave it up to a visiting politician which way we actually analyze the data from the slits.” What is this “garbage data”? How is it “mixed” with the slit data? No details are given. Also, the mixed data would have to be isolated from any interaction with the rest of the world until the “visiting politician” comes by. I don’t think we have the technology to do this.
I suspect the author, Ross Rhodes, has slipped gracefully and seamlessly from real experiments and outcomes to hypothetical experiments and their expected outcomes.
Lastly, I will note wihout comment that the homepage linked to at the bottom states
I read the link, and it seems quite factual up until it starts talking about the link between consciousness and quantum mechanics. However, when it did start talking about conscious observation, it made assertions that I have never heard before, and gave no references. In addition, I can construct a Gedanken experiment that requires time travel for his assertions to be correct.
Suppose you have active field sensors, sending their data to be recorded on some nonconscious medium. Following the experiment, a random value is calculated, determining whether or not all the data generated by the sensors is erased or not. But the observer has already seen whether or not an interference pattern has emerged, and, if Rhodes’ assertion is correct, can predict, before the random value is generated or not, whether the data will be erased.
Now, if the field sensors at the slits are inactive, then, yes, the interference pattern will build up. But if the sensors are active, regardless of whether or not the detection of the electron is ever seen by a conscious being, the interference pattern will not be generated. This has been the conclusion of every experiment that I ever heard of.
Unfortunately, Rhodes does not give references to the experimental evidence backing up his claims. Of course, neither do I, but until someone can point out the flaw in my Gedanken experiment or show me a reference to an actual experiment, I will chose to disbelieve in time travel, and thus disbelieve Rhodes’ consciousness claims.
Successive firing of photons results in the recording of individual points on the backdrop behind the double slits. Over time the dots merge to form the interference pattern. Prior to my knowledge of this particular experiment, I assumed that the wave phenomenon was a result of a wave of photons, thereby creating their own medium which of course is usually a prerequisite for wave phenomenon.You know of course that if you block one of the slits, all you get is a single bar showing up on the backdrop.
Now if we fire single protons at a double slit, why do we get an interference pattern over time? This question caused me to postulate my previous theory that the free sub atomic particle is not geometrically bound to a single point. As such it can be described as a medium in transit and the various strike locations are merely the result of where the advancing wave makes its first contact after transiting** both slits simultaneously**. Upon contact the photon impodes allowing a point strike to be recorded. Where the successive individual photon waves makes contact is a function of probability, and you will note that the strike intensity decreases towards the outer limits.
Hmm, I haven’t heard that single atoms exhibit wave particle duality. Did you get that off the net? Care to provide a link?
Researchers over at Colorado did so with a positively-charged beryllium atom a while ago. It was picked up by much of the major media. Do a web-search for “Schroedinger’s cation” to find some links to it.
Well, frankly, that link was just one of several that supported what I had already read. If you want better references then you should read what Stephen Hawking had to say about it in “A Brief History of Time” or the aforementioned book by Roger Penrose, “The Emporer’s New Mind”. Both of these authors make the same claim - that it is the observation that collapses the wave function. If you observe the photon/electron/particle at the slit, the wave function collapses at the slit and you don’t get the interference pattern. I’ve seen and heard this claim in many other places, so I’m inclined to believe it must be fact.
Punoqllads:
As I’ve stated, there are many accepted experimental results supporting the link between the collapse of the wave function and observation of the particle. I, too, question the link to consciousness and this is the only place that I’ve seen this requisite, so I’m not going to go out of my way to defend that claim…
grienspace:
BTW, your theory is formally known as the Copenhagen Interpretation. However, I think this thesis falls apart when we consider the behavior of atomic particles.
Well, I’ve read it in many different places, but a quick search turned up the following link:
There is another quote from this link that I think you’ll particularly like:
Sound familiar? It’s the essence of the Copenhagen Interpretation. Unfortunately, it ignores the point I made earlier that atoms flying through space cannot be “imagined” to be merely probability waves, yet they exhibit the same wave-like interference phenomenon. It also ignores a few other problems like quantum non locality (EPR Paradox) and the universal speed limit (i.e. the Copenhagen interpretation allows that a signal must travel faster than c to collapse the wave function).
Thankyou JoeyBlades. I cranked up the search engine and enough info to keep me busy for quite awhile. Two years ago this idea popped into my head, and I’ve discussed it many times, but no one has ever made the connection between my theory and the Copenhagen Interpretation. I guess I can’t call it my theory anymore. Wow, you really know this stuff!
“The photon has no specific location until we observe it,” and “when we observe [a particle] the wave function collapses,” do these mean that bouncing something off it to go to an eye or other register is what locates it and/or collapses it? I think some people think that observing something is a pure possibility, ie., they don’t understand that the observation causes the effect they see in the sense above, ie., that the observation literally means sending a particle, wave, or electromagnetic thingamy that hits it and then may come back to the observer, so what we see is the creation of the thing because of the sending of the beam or wave energizing it and then coming back to us in the laboratory.
This is a much stronger statement than the first one, and this is where I think the author of your link is beginning to move from real experiments to hypothetical ones. I suspect that the sensor triggers interacting with the electrons will destroy the interference pattern, even if the experimenter (or the politician) doesn’t observe the triggers.
I’ve read “A Brief History of Time”, and don’t recall a statement like the second quote, although it was a while ago. I haven’t read the penrose book.
I read the link that was initially posted in reply to the thread and while I admit I know relatively very little about this subject I have to ask: The link states that the difference is whether we know, not if it is recorded. Is this correct? Does anyone have any other sources that back this up?
I have also read A Brief History of Time and don’t recall any information of that nature (“If the triggers are allowed to fire, but the results are not observed, the interference pattern remains, unimpeded by the field sensors.”).
I also have another question that I have been wondering about since I saw the link to the “Reality Program”, what happens if a sensor is put directly infront of the electron gun (or in between the two slits) with the results recorded? Also, if a laser is used with a light sensor in between the two slits, (I should note that I am once again using that link for reference) and a single pulse of light is fired in between the two slits (according to the reference it ends up right behind where it was fired), what is the time from it hitting the slit to the boundary behind it?
It seems fairly dubious to base all of my questions on that link, so does anyone have any more reputable ones?
I guess I need to retract an earlier statement. I took a brief glance at Hawking’s ABHOT this morning and could not find a reference to the observation collapsing the wave function. In fact, Hawking barely touches the subject (at least in the section that I found rather quickly). It may be elsewhere in the book, however I couldn’t verify that, so I feel it only proper to retract this claim. However, in “The Emperor’s New Mind”, Penrose spends quite a lot of time on the issue and its implications. He discusses several of the attempts to isolate and detect the particle without impeding it’s progress. He concludes with this statement:
[quote]
In order for the interference to take place, there must apparently be a ‘lack of knowledge’ as to which slit the particle ‘actually’ went through.
[quote]
I’ve read this in other places, as well. In fact, I’ve seen a couple of statements that claim that it is THIS phenomenon that makes the two slit experiment a demonstration of quantum mechanics and not merely one of wave mechanics.
Pay particular attention to “[1.C.8] The eighth and final execution of the quantum-2-slit-experiment”.
It’s important to note that in this last reference, the interference pattern is being disrupted not by the detection, but rather by the “undetection” and inference of which slit the particle went through.
I’m sure I can dig up more supporting evidence…
So far, I’ve found nothing seriously wrong with the information at “The Reality Program” link. Zen seems to take issue with the statement “our world is, in fact, a computer simulation”, however I suggest that Rhodes is merely waxing whimsically metaphoric.
What I take issue with about that site is that I believe that some of what the author presents as actual experiments and their outcomes are not all experiments that have actually been performed.
I may be wrong in this, and if I am, I’d like to know more details about how the experiment is run. The geocities site has much better explanations of what is going on in the experiments.
This would seem to contradict the Reality Program link, which says (again, italics mine)
Admittedly, they are not describing the same experiment, but I think they are claiming to examine the same question: Is the act of a person observing which path the particle takes is necessary to destroy the interference pattern.
Experiment [1.C.8] from the Geocities link seems to be consistant with the American Scientist link, and not the Reality Program link. (If you never checked whether a particle was detected, and just lumped the results together, you’d just get the super-position of the two distributions, not a fringe pattern.)
Thanks for the NCSU link, JoeyBlades. It was well done and it brought me up to speed, sort of, on the two-slit experiment.
By far the most interesting question on the page was this:
If I had an answer to this would, I would be very happy.
It was interesting to note that the results are the same with photons, electrons, and atoms. It used to annoy me that photons and electrons behaved the same way, since my own intuition would really much rather they didn’t. So I found it somehow comforting that whole atoms are supposed to to do the same thing.
Has anybody read “The Fabric of Reality: The Science of Parallel Universes and Its Implications” (New York: Pengiun,1997) by David Deutsch? And if anybody has read it, what do they think? I’m not familar with David Deutsch.
I bring this up because Michael Crichton describes a photon interference experiment in his novel “Timeline” and lists this book as the source for his info. In the book a character claims that what is interferring with a single photon “are photons from parallel universes”. This then is extrapolated off into the ‘science’ that makes the plot possible.
I know better than to get my science from popular novels, but Crichton did take known molecular biology techniques and experiments such as DNA cloning and the reviving of ancient bacteria to do a similar extrapolation into recreating dinosaurs in “Jurassic Park”.
I don’t buy the infinite parallel universes theory myself, but I know it’s a hypothesis that been around in physics for awhile.
I’ve been lucky enough to hear Roger Penrose and Kip Thorne speak in person although physics isn’t my area (I just work next to the Physics Dept and these guys are worth catching even if I’m in over my head). So what’s the skinny on David Deutsch?
From ‘Timeline’:
“Anybody who is not shocked by quantum theory does not understand it.” Niels Bohr, 1927
“Nobody understands quantum theory.” Richard Feynman, 1967