Ponder Stibbons

@Galen Indeed, an important point. If one is cool with this assumption, then no problem - but it should be stated. From a pragmatic point of view, I would support the use of the assumption. If we don't assume it it becomes very difficult to come to any conclusions as our thought process is entangled with the observation. But, from the pure mathematical point of view - the idea of determining the prior probability measure over all possible universes is fraught with ambiguity.

@BillAlsept All I was saying is that there is no requirement for the fields to be made of anything, and that in any theory there will be fundamental elements that are not made of anything. Within the confines of QFT, the electron field is such a field. Whether this will be replaced by a later theory in which the electron is a composite field is unknown and not really something we can usefully speculate on here. I am not demanding that the electron field is fundamental just saying in QFT it is.

I did ask you to back up your claim that a photon is associated with an irreversible process.

@FlatterMann What on earth do you think I am claiming? Your response about perpetual motion make no sense at all. All I am talking about is the wave-only interpretation of quantum theory, and even there I am not making any claims, just asking about evidence.

@BillAlsept and energy is a property of the field, not what it is made from. Eg, in Schroedinger theory, essentially the temporal partial derivative.

@BillAlsept Unless you want to invoke particle democracy.

@BillAlsept to be more precise - if we say that some things are built out of other things then at some point we have to stop or we have an infinite descent. Fundamental fields are called that because they are fundamental. That is - not made of anything. They just are. If you came up with a new theory where the current fundamental fields (photon, electron, etc) were fields in an effective field theory, then you would just create a new set of fundamental fields that are not made from anything.

@FlatterMann I strongly suspect that a lot of this comes down to differences in the linguistic aspects of the terms. Having spoken to plenty of people on this topic over the years, I feel that people take a lot of it in different ways from each other and often in arguments pick up on some element of the usage of the word which was not fundamental to the intention.

@FlatterMann not quite sure why you mentioned most of what you just addressed to me - as I never said anything in contradiction to it. But, I would disagree about what a photon is. That is - I know what a photon field is, but I think that photon is just an adjective. And I expect you are incorrect about requiring a photon to be associated with an irreversible process. Non linear, perhaps, but irreversible. Not sure why you went that way.

@BillAlsept okay, I know you seem to be talking to Flattermann and not noticing me, but I just wanted to say that for me the field is the field. It is otherwise undefined it is made of itself. So, I agree with you that it is not made of field energy. It may have associated energy (as does an electric field) but that does not mean it is made of energy. However, I would also feel that we do not know that it is made of individual photons. A photon is a certain pattern in the field, the field does not have to be described as a collection of photons.

@FlatterMann while my views appear to be mostly aligned with yours here, I feel that the argument is incorrect or at least incomplete. Solar panels get hot and radiate photons. So, one could say they are self draining. Also, the total number of photons does not have to be conserved even if we assume they exist as lumpish particles - as we have the principle that they can be created and destroyed. Having said that - I am currently engaged in several arguments in which I am supporting the idea that photons are nothing but fields.

@ACuriousMind I have added what I hope will clarify. I am using the word observe and exist informally. And I am not even slightly saying "particles don't exist change my mind". I am asking for experiments that people think have to be interpreted in terms of hard lumpish particles. Maybe this should be moved to a chat session. If you are interested. But, my question is not really philosophical.

@FlatterMann more or less my position. But, do we have some kind of reference that would clearly state this as an orthodox position. My motivation is to be able to respond compactly in discussions on the matter.

@JohnRennie I added "fundamental" to the title. My question relates to the issue that many people seem to feel that the electron field somehow describes another entity that is a small hard lump. This is the focus of the question. And in that sense, an atom is not a particle.

@hft thanks, I will organize the references.

@hft I read Dirac's paper introducing the Dirac equation as stating that no particles other than spin 1/2 particles can have a position operator. Could you comment on that? Or should this be another question?

@hft yes, I acknowledge that I have seen both definitions. But, I entirely meant "jargon" here to mean specialized language. The implication not being derogatory, only that it was not applied to particle in the classical sense. I have met several people recently who claim to be not followers of Bohm, and yet also claim with strong commitment that there is somehow a small lumpish particle in the field somewhere.

@hft Different people have a very different idea about what a particle is. While your density of N point particles is definitely what I would agree is a density of N point particles - that is not what most people seem to be meaning by the term "particle". In the article I was referring to, a field was said to be for a point particle if the Lagrangian density was a function of the fields at each given point. That use definitely feels like a jargon term. And it is different from the one that you present.

@RyderRude comment is appreciated, and I think that this is something like the attitude a number of people I have met have. I would feel that these cannot be observed directly and are more clearly a computational tool.

I read that. It seems to support my view - that "point particle" is a jargon term and does not refer to any kind of physical point or physical particle - other than that I could say that if I integrate density I am adding up an infinite number of point particles. But, that is just a way of phrasing the Steiltjes sum - not a physical concept of something that can be observed.

FYI - I have a doctorate in mathematics and have studied and particularly like quantum field theory. I know what "observe a particle" can be interpreted to mean. But "point-like", it seems this phrase is being used in a jargon sense. A position that seems to be supported by your references, following up on that I got that a "point particle" means the lagrangian is a function of the fields at a single point.

We are hitting close to the mark. How is a particle in QFT point-like? I have heard this claim several times today, but cannot see it in the mathematics, which is a field theory.

@craq that would be John Searle's approach.

I read the generation ship article linked in the post, and feel most strongly that the article is an argument from incredulity - the author cannot understand how the problems can be solved and thus declares them to be impossible to solve. And also a side effect of the view I have seen more frequently recently that some how it is inappropriate to think of going to another planet. That we must accept that we never will and should not. Neither of these points of view can I empathise with.