Is light a wave or a particle? 16


Thanks to Marden Seavey for posting this item from YouTube, Is light a wave or a particle?


Let me be clear, I am in full support of what Sabine Hossenfelder says in this video. My comments below are only intended to amplify what she is saying. These comments are only intended as an additional way to look at the problem of thinking that there is a paradox here, and seeing how physicists are now avoiding creating such paradoxes in the minds of future students and non-physicists.

It seems to me that physicists started naming things like quarks and leptons to get away from the mistaken idea that likening these quantum mechanics thingies to Newtonian mechanics thingies would provide insight into what they were. That original comparison to familiar concepts left us with the non-answerable question of whether light is a wave or a particle. As Bill Belichick would say, “It is what it is.” As this narrator says, light displays some particle like properties and it displays some wave like properties, but it isn’t either of those two things. Particles and waves are abstract and simplified concepts that describe some properties of certain thingies. These thingies are what they are. You can only talk about the properties that they exhibit.

Put another way, particles and waves are models of reality. They simplify reality so we can write down and solve equations to predict what will happen in reality. Since the concept of particle or wave is a simplification of reality, we can not expect reality to behave only as the simplified model does. Reality is more complex than the model. If it weren’t, we wouldn’t need to simplify it to get some understanding. A simplified model only works in the situations where it is applicable. In other situations the model does not give you correct results at all. In the situation where light can be modeled as a wave, then the wave model is a good explanation of what light does. In situations where light acts as a particle, then the particle model gives a good description of what light does. Outside the domain of applicability, the model does not give a correct description of what light does. If we find a domain in which neither model is good, then we won’t be able to predict what light will do at all. In such a domain, we would have to see what light does, and then try to come up with an explanation of what rules light is following in that circumstance. Rather than calling that third model by a name of something that we have some insight into, we might just give it a wacky name to make sure nobody thinks that light is actually that other thing to which its behavior is similar.

I leave it to my friends who are more expert in physics than I am to tell me where I went astray and said something above that was full of crap.


Leave a comment

This site uses Akismet to reduce spam. Learn how your comment data is processed.

16 thoughts on “Is light a wave or a particle?

  • Marden Seavey

    Aw, don’t worry, Steve, I won’t think you’d be presumptuous. You at least have the courage to take on difficult (impossible?) tasks whereas I’m too afraid I’ll be wrong. So, I don’t offer anything, I just criticize. There must be an aphorism that describes this. He who never tries never succeeds? Or something like that.

  • Marden Seavey

    Sarcastic comment about quantum gravity? Hey, why don’t you read what Bee says about it?

    http://backreaction.blogspot.com/search/label/Quantum%20Gravity

    I see there are 70 comments so far on her answer to someone asking about the multiverse. So, this is really about multiverses but quantum gravity plays a large part. Give you a chance to argue with knowledgeable people, not half-baked physicists like myself. Go Steve Go!

  • SteveG Post author

    I think I was still right with my sarcastic comments about Quantum Gravity. Here is a snippet from the Wikipedia article.

    One of the difficulties of quantum gravity is that quantum gravitational effects are only expected to become apparent near the Planck scale, a scale far smaller in distance (equivalently, far larger in energy) than what is currently accessible at high energy particle accelerators. As a result, quantum gravity is a mainly theoretical enterprise, although there are speculations about how quantum gravity effects might be observed in existing experiments.

  • SteveG Post author

    Pardon me for my mention of Quantum electrodynamics. Yes, I was trying to be a wiseacre by implying that this was an unsolved problem in Quantum Mechanics. I thought that when I learned about Quantum Mechanics it was unsolved. WikiPedia says I am wrong.

    Based on Bethe’s intuition and fundamental papers on the subject by Sin-Itiro Tomonaga, Julian Schwinger, Richard Feynman and Freeman Dyson, it was finally possible to get fully covariant formulations that were finite at any order in a perturbation series of quantum electrodynamics. Sin-Itiro Tomonaga, Julian Schwinger and Richard Feynman were jointly awarded with a Nobel prize in physics in 1965 for their work in this area.

    The theory, for which the award was given in 1965, was developed long before 1965.

  • SteveG Post author

    “It’s not a simplification of classical or any other model.”

    Of course it is not a simplification of a model. It is a simplification of reality.

    Take a chill pill, please.

  • Marden Seavey

    I like the way you take on the physicists of the world, explaining to them what they are doing. Take this sentence of yours for example: “Oh, and by the way, quantum mechanics is also a model that simplifies.” No, it’s not a model that simplifies; it’s a model that explains things that can’t be explained any other way. It’s not a simplification of classical or any other model. It’s a new model entirely.

  • SteveG Post author

    Maybe the problem is that you think what I wrote is an attempt to disagree with the video. It is not anything of the sort. I am supporting what is in the video, and trying to explain it in other words. I think there is value added by what I am trying to say. If you think there is no value, then I am hoping it is because I stated my point poorly. The other possibility is that there really is no value in what I am saying, and I just don’t see your point.

  • Marden Seavey

    Yes, put in a smiley, what the hell. Hey, I don’t want to argue with you. Have it your way, what the hell. What I’m interested is the mystery of it. When quantum mechanics was discovered it drove people crazy. It made no sense. Einstein didn’t want to accept it but in the end he perhaps begrudgingly had to. No “hidden variables” were ever found. etc. etc. And this business of light being neither particle or wave is another paradox of modern physics. Not to mention “entanglements” and Bell’s theorem, etc. etc. None of this stuff is reducible to common sense.
    I apologize for comparing you to a Republican. That was uncalled for on my part. I know you and I both hate modern day Republicans!

  • SteveG Post author

    You and I know what a wave function is and what the Greek letter stands for. Sharon hasn’t the foggiest idea what that woman was talking about in the video. She did understand my explanation. My explanation didn’t say anything that was untrue, unlike what the Republicans say about what they are not scientists about.

    What I said in the post may sound to you like what the Republicans say, but if you look at the details with an open mind, it is nothing like what the Republicans say.

    My explanation has been user tested on one non-scientist. What about your explanation, or the one that is in the video? Is there anything wrong with applying the maxim (tautology) that it is what it is? I can’t see how it couldn’t be what it is, unless you are speaking Bill Clintonese. In his case he argues that it depends on the meaning of what “is” is.

    Does it help if I put in a smiley 🙂 ?

    Oh, and by the way, quantum mechanics is also a model that simplifies. There are paradoxes in quantum mechanics that the experts are still hashing out. This is why I talk about the limitations of models. Each new and more sophisticated model settles some paradoxes, but other more subtle ones about the new theory can be expected to arise. Physicists who expect there to be a final answer that has no paradox in it just don’t understand the inherent limitations in simplifying models.

    Do you have a theory of quantum electro-dynamics that includes gravity yet?

  • Marden Seavey

    You remind me of Republicans who say, “I’m not a scientist, but…”. And they give you a “common sense” explanation of why there’s no global warming. What you seem to be doing, Steve, is using Bill Bellichick’s “common sense” to explain the problem of light being a particle or a wave or both or neither. It’s not a matter of words. It’s a matter of physics, of the reality. It has been found that quantum mechanics provides a wave function which describes physical experiments, in this case involving light. That’s it, period. Why not just stick to the physics? That’s what we’re talking about really.

  • SteveG Post author

    In circuit simulator terms with which we both have experience, most of the models we made for diodes did not include reverse breakdown. If you tried to simulate the diode with our model, and you reverse biased it beyond the breakdown voltage, the model would not come anywhere close to showing you what would happen. Since our engineering customers did not usually have situations where this behavior would happen, they were perfectly happy for us to leave it out of the model. We assumed, and were usually right, that the engineers using our simulator and models were smart enough to only operate the devices in the regions where our models were accurate. Of course, sometimes there were surprises when the device was operated in a region that we didn’t think we needed to worry about.

    A good circuit design engineer just like a good software engineer would have to track down any discrepancy between what the software predicted and what happened in the real world. Until you could explain the reason for the difference, you didn’t know if it was an error in the software, a problem with the model, or an error in the observation of the real world.

  • SteveG Post author

    “A simplified model only works in the situations where it is applicable.”

    The “situation” means what you are trying to observe in the real world, the conditions you place on the sample you are trying to measure, in other words “the experiment”.

    The particle model is applicable under the circumstance where particle behavior is exhibited – the photoelectric effect.

    The wave model is applicable under the circumstance where wave behavior is exhibited – the two slit interference experiment.

    Light is not either model. Each model describes a subset of what light is. A thing is not a subset of what it is. It is the whole thing. Referring to that great philosopher, Bill Bellichick, “It is what it is.” If you can find some other behavior of light other than what these two models show, then light has the behavior of that other model as well. It is a little like the way wines are described when people talk about it tasting like other things that are not wine. If you could actually describe the taste of those other things without referring to wine, then you could describe the taste of wine without referring to those other things. We just have not found the words that adequately describe something in its entirety except for the word we use to name the thing that has all the properties the thing has.

  • Marden Seavey

    Sorry, Steve, yes, I misinterpreted what you said. If you meant that, yes, light is what it is by what experiment is done on it. I think that was the point of her post. Although maybe I’ll watch it again later.

  • SteveG Post author

    Mardy, How did you interpret what I said to be any different from “The point is that it’s the configuration of the experiment that determines whether a wave or a particle is observed, in fact, whether light is a particle or a wave.?”

  • Marden Seavey

    Did you really listen to Sabine’s post? What she’s saying is a lot simpler than what you’re saying. The point is that it’s the configuration of the experiment that determines whether a wave or a particle is observed, in fact, whether light is a particle or a wave. Notice that in her closing she writes down the symbol for the wave function. It’s the use of this function applied to the experiment that determines whether light is seen as a particle or as a wave. The experiment is the important thing.

    Incidentally, Sabine is a top-notch and highly respected theoretical physicist who’s written a large number of papers and is also highly respected for her blog. Try reading that sometime! Before I would make a comment I’d replay her video and pay close attention. I’m planning on that myself.