[alancalverd]

Good choice. AFAIK Honda were always built to Euro specs with laminated windows but toughened glass (cheaper, clearer, didn't go yellow in sunlight) persisted in the UK for quite a while.

[Eternal Student]

Hi.

Quick question concerning the nature of energy: work can definitely be described as a boundary phenomenon, can energy also be categorised as such?

   I don't know, that's something I had to look up.  Thanks for expanding my knowledge of stuff.  To be honest I'm still not sure what a WAG is  (internet says: a wife or girlfriend of a football player).
    Anyway, it seems like @alancalverd's answer is reasonable based on what I could find.
    In the theory stuff we do often want to talk about an "energy density" which is an amount of energy in some space or in some material.  No boundary between any two things is necessary.  By contrast we don't talk about a "work density",  work is definitely always done on something (on some boundary between two things etc.) rather than just being spread out over a region of space etc.
     I know we've had other discussions in other threads about energy.   Basically "work" and especially mechanical work is quite easily defined while "energy" is much more nebulous. 

I worked for a short time in the video industry and all the lens assemblies we used had continually variable irises.

  ...And also relating to @alancalverd 's comments about photography and polarising filters earlier...

       I did mention in that post that I hadn't done a lot of editing or polishing.  I found a reference to the use of polarising filters as a method of controlling brightness and went with it.  It fitted the theory and tied up with everything in the post nicely, linking the theory to some practice.   So it's not "wrong" in that at least some photographers did use it - but a bit of poetic licence was applied.   When I said "Photographers used to like using a pair of polarising filters...".  I really didn't care if they liked it or how commonly it was done,  it was needed for the post.

Best Wishes.

[paul cotter]

WAG= wild ass guess, a term introduced on another thread by Kryptid, as far as I remember. I must apologise, yet again, for using acronyms that may not be understood.

[varsigma (OP)]

I haven't brought this up yet, but here goes.

What do you think of the use of modern day information science in theoretical physics?

If particles in the Standard Model are fundamental, does that mean they are a form of information; are particles like a Shannon message?

Do you think there is a better understanding of information these days, at least classical information?
Given that we know how to compress images and so, erase 'redundant' information while keeping enough so, you know, it's still recognisable? Just a for instance.

[alancalverd]

I think you need to distinguish between mapping (where you lose dimensionality that can be inferred), minimisation (losing genuinely redundant information) and lossless compression (coding recognised sequences into shorter sequences that fully identify the original). Not sure how any of that can apply to a fundamental particle which by definition does not contain or represent anything redundant or synthesisable from data known to the "recipient".

[Eternal Student]

Hi.

I haven't brought this up yet, but here goes.

    Actually, it wasn't hard to guess that you were going to talk about "information" in some profound sense:
post #65:

...in terms of the quantum information...

post # 22:

...Copying information classically never gives you identical copies...

- - - - - - -

What do you think of the use of modern day information science in theoretical physics?

      In principle, there's no need to draw boundary lines separating "physics" from "computer science" or "geology" or any other science.   If something is useful, then it's useful.

Do you think there is a better understanding of information these days,

    Yes, most fields of knowledge do develop over time,  Information science isn't any different from other areas of human knowledge or endeavour.

If particles in the Standard Model are fundamental, does that mean they are a form of information...

    As I expect you already know there are some recent theories that tie some concepts in physics to some concepts in information science.   
Examples:  
   1.   The possibility that Black holes store information on their boundary along with further developments that what we perceive as 3-Dimensional reality could be a holographic projection of information just stored on a 2-D surface.
   2.   Thermodynamic entropy being linked with Shannon entropy. 

   Information science is useful when it explains something or allows something to be modelled, it's almost irrelevant if everything in reality is just information or not.  Philosophy might be concerned about what the universe really is, physics is just concerned with how things behave irrespective of any terminology you might apply to describe those things.

Best Wishes.

[varsigma (OP)]

I think you need to distinguish between mapping (where you lose dimensionality that can be inferred), minimisation (losing genuinely redundant information) and lossless compression (coding recognised sequences into shorter sequences that fully identify the original).

Ok well, I think the concept most people have of classical information is related to our sense of vision, primarily.
It might be why double-slit experiments are given as examples a lot.

So I think about it like this: dots appear that can be seen--the dots are classical. Up close, real close they look completely different. "it looks like a dot" is a far field effect. So far, one dot, one particle and one bit of information.

But lots more dots make up a pattern. So now the idea is compression of this information such that the pattern is conserved.
How many dots are needed to see the interference pattern from a distance? Is it the same number for any kind of particle?
And so on. We know that up close, each particle that leaves a dot actually leaves a lot more than a pointlike mark, but we ignore it. Because we ignore it, that means we see an approximation--an already compressed image--and its a choice we make.

I think its important, with quantum information, to keep track of this thing we do without really thinking about it. It is pretty hardwired.

[evan_au]

beware of LCD displays on all GPS systems.

Some years ago I had a car with a small driver information panel. It used LCD technology, with a linear polariser.
- Unfortunately, they had oriented the linear polariser so that if you wore polarized driving glasses, you couldn't read the information display.
- I sometimes have the same problem if I wear my polarising glasses onto the train station - the LCD panels displaying the route of the next train appear black.

This has been resolved on smartphones and newer cars by using circularly-polarised LCD screens. You can still read them with linearly-polarised sunglasses (but you lose a bit of contrast).

[alancalverd]

How many dots are needed to see the interference pattern from a distance? Is it the same number for any kind of particle?
And so on. We know that up close, each particle that leaves a dot actually leaves a lot more than a pointlike mark, but we ignore it.

Er, no. If you are thinking about single-photon two-slit experiments, we know that each receiver event involves a single photon with the same energy as the one that left the transmitter: the photon clearly doesn't split and interfere with itself because that would give you two red dots from each blue photon, but what we observe is a pattern of blue dots.

So how many events constitute a pattern? That is pretty much the same question as how long is a piece of string. The more you know about the cause, the less you need to know about the effect to calculate the entire pattern - a case of fully encoded lossless compression. If I know you have a blue light source and two slits with a defined geometric relation, I can tell you what the interference pattern of an infinity of photons will look like as soon as I have detected just one.

If I know nothing about the slit geometry I will need enough receiver events to indicate where I might find maxima and minima, and the more information (events) I have,  the more confident I can be in describing the slit geometry. But some of the events will be redundant repeats, not contributing any more data to my calculation, so it looks as though the error bounds decrease as 1/√N.

[varsigma (OP)]

Er, no. If you are thinking about single-photon two-slit experiments, we know that each receiver event involves a single photon with the same energy as the one that left the transmitter: the photon clearly doesn't split and interfere with itself because that would give you two red dots from each blue photon, but what we observe is a pattern of blue dots.

I'm not sure that you got the gist of the question: how many dots are needed so a pattern is recognisable?
If you use a pattern-recognition algorithm and single-particle events, when does an interference pattern exist?

What would the algorithm need to decide this?

[varsigma (OP)]

So how many events constitute a pattern? That is pretty much the same question as how long is a piece of string. The more you know about the cause, the less you need to know about the effect to calculate the entire pattern - a case of fully encoded lossless compression. If I know you have a blue light source and two slits with a defined geometric relation, I can tell you what the interference pattern of an infinity of photons will look like as soon as I have detected just one.

I'm talking about doing the experiment. In that case you wouldn't expect to see the same pattern twice, especially any time before the pattern emerges.

The problem here is recognising the interference pattern, so how many particles will do that? That is, given any pattern of dots from any double-slit experiment, how many can be erased so there is still a pattern?

[alancalverd]

If the laws of physics are constant (which seems to be the case) you would always expect to see the same pattern because the probability distribution will be the same each time. The question is how many dots are required to recognise that a sampled distribution is consistent with your theoretical continuous distribution. 

I'm sure ES has a better grasp of formal statistics than I, but the χ² "goodness of fit" test is rattling about in the recesses of my memory. Essentially, you partition your expected distribution E into "cells", calculate the fraction of the total area in each  cell, and count the fraction of actual events A in each cell. Then the sum of the squares
∑_x (E_x/E - A_x/A)²
tells you how close your actual distribution is to the hypothetical continuum.

The point at which you announce the result is up to you! My favorite story concerns the Indian Queens Bypass on the A30 through Cornwall. Not sure how accurate it is but this is my recollection from the local School of Mines about 20 years ago: The engineers had asked for 1000 trial boreholes along the proposed route, to determine the subsoil structure. The first two tests struck granite at a couple of meters below the surface, in the middle of the route. Politicians and accountants announced that  the subsoil was granite and no more tests were required so land was purchased and construction commenced immediately on that basis. It turned out that these were the only two granite boulders in 30 miles of peat bog. The project ran umpteen years late and God knows how many times over budget.

[varsigma (OP)]

If the laws of physics are constant (which seems to be the case) you would always expect to see the same pattern because the probability distribution will be the same each time.

The only issue I have with the phrase "the same pattern" is if, say you have a single-particle beam and stop after say 20 particles. Now replace the screen and repeat, the next pattern of 20 dots will be different from the first.

The question is how many dots are required to recognise that a sampled distribution is consistent with your theoretical continuous distribution.

Yes, and because it is a sample of a statistical distribution you expect different samples to be statistically different.
Even though two interference patterns are in the same class of objects, say. But more generally, two or more interference patterns contain the same information independently of how large the sample. That is, they convey the same "message" with equal expectation.

[alancalverd]

I think you have answered your own question quite elegantly.

Einstein said that repeating an action and hoping for a different result is madness, but two random samples of the same thing is not a repeat - definition of randomness!  So the question is what level of confidence you require to assert that they are samples of the same distribution.

The power of the χ² test is it can tell you not only the extent to which your samples may be said to be representative, but also if the fit is "too good" - evidence of a failure of the mechanism, such as a bit of the primary beam getting through your supposed filter.

[Eternal Student]

Hi.

I'm sure ES has a better grasp of formal statistics than I, but the χ² "goodness of fit" test is rattling about in the recesses of my memory....

    I don't think exactly which test you use is going to be important for answering the OP, the important point is only that it's all about rejecting some hypothesis with some probabilities.   You may need an infinite amount of data from an infinite number of repetitions of the experiment before you can conclude with certainty, that the data does conform to the distribution predicted by the model.
   Just for completion we need to mention at least one situation where you wouldn't need an infinite amount of data:  There may only be a finite number of photons in the universe and time may be discrete and finite.  In that situation it's much easier.  Just sample it all.  Once your "sample" is the entire population then you're done, you have a complete description of the distribution.   (I didn't say it was practical).

Best Wishes.

[alancalverd]

New readers:

Note the difference between physicists ("consider a spherical cow in a vacuum.......") and mathematicians ("an instantaneous sample of all the photons in the universe......").

Or as others have put it, "Rocket science is two equations. Rocket engineering is a lot more complicated."

[varsigma (OP)]

Just to round things out, I'd like to touch on some philosophical implications.

One is, that philosophy has a problem it seems, with being able to deal with modern physics. One argument I've seen about why this is has to do with philosophy being largely anthropocentric, objects are distinct (you can see their boundaries, you can pick them up etc), they have properties which again are things we experience in the far field, or at much greater than atomic dimensions.

The anthropocentric frame, if you will, is where we observe particle or wave behaviour. But this is when quantum interactions occur which we can't see; except we get the notion that at those atomic dimensions, the physical world must be quite different. Quantum logic isn't like any other kind of logic, and philosophy needs logic.

So why no consistent quantum philosophy? I think there possibly will never be such a thing, and one thing that explains is why you get so many (apparently) different answers from physicists when you ask them "what is a photon?".

[alancalverd]

You will never get consistency from philosophers: their job is to tell you (including other philosophers) that you don't know what you are talking about.

On the other hand I'm embarrassed on behalf of my colleagues if they give you different answers to "what is a photon". It is a quantum of electromagnetic energy, modelled as a particle with zero mass. Anything else would have a different name.

[Eternal Student]

Hi.

So why no consistent quantum philosophy?

     A few philosophers are throwing out papers and discussions involving Quantum theory.   See, for example,  https://plato.stanford.edu/entries/qt-issues/     The online Stanford Encyclopedia of Philosophy,   which has a lengthy discussion and cites many other modern articles.   It's still a bit too early to know if there will be a consistent quantum philosophy  (in my opinion).   

    However, a lot of philosophy is human centred and human beings don't typically observe quantum effects or build models in their mind of how things work that are remotely like quantum mechanical models.  So there is no reason why quantum mechanics should be important for all of philosophy.
     An explanation of the nature of morality that involves pages of complicated mathematical equations would be of no use or benefit to most people.  It doesn't help them understand their own nature or the nature of things around them.

Let's back this up with some analysis and opinions taken from  the paper  "The Influence of Quantum Physics on Philosophy",  F.A. Muller,  first published 2021,   an on-line version is available here:  https://link.springer.com/article/10.1007/s10699-020-09725-6  .

      Concerning Analytic Philosophy, we can take heed of the results of the Philosophical Papers Survey, conducted by David Chalmers and David Bourget (2014; an update and extension is in the making). They asked opinions about 30 controversial issues in philosophy and obtained 3226 responses:
     (a list of 30 issues follows including:)
   17.  Moral judgment: cognitivism or non-cognitivism?
   18.  Moral motivation: internalism or externalism?

Quantum physics had no discernible influence on any of these debates, full stop. Should it have influenced these debates? For most issues, I don't see what it could have contributed or how it should contribute.

  Muller discusses the burgeoning field of "philosophy of physics" and makes it clear that quantum physics has had considerable impact on this.   However, with respect to the wider fields of philosophy the conclusion is as follows:
    9.  Recapitulation:
Although quantum physics has influenced philosophy in the sense that it has grown a new flourishing and blossoming branch of the tree of philosophy, apart from some recent contact between philosophy of physics and metaphysics, quantum physics has had hardly any influence on philosophy at all, and at best some influence on metaphysics, mostly in recent times. With regard to prominent issues intensely thought about by philosophers, such as those on the Chalmers-Bouget list, we dare conclude that it is difficult to see how quantum physics could bear on those issues. If it cannot, it ought not, for ought implies can.

Best Wishes.

[varsigma (OP)]

On the other hand I'm embarrassed on behalf of my colleagues if they give you different answers to "what is a photon". It is a quantum of electromagnetic energy, modelled as a particle with zero mass. Anything else would have a different name.

Ok. I agree that most sources will say that a photon is a discrete particle or quantum of the electromagnetic field.
However, if you go to physorg or stackexchange, things are a bit less clear. It depends, apparently to a large extent, on how close you are to a photon as it were. Again with the near-field/far-field distinction, as to what a thing might appear to be.

And generally we represent photons and other particles in a diagrammatic way, and what the diagram looks like depends on the context. In electronics the electric field of some signal propagates at the speed of light; electronic circuits emit radiation in all directions. Photons don't really make sense at radio frequencies, even if radio signals are a whole lot of photons with long wavelengths.

Add to that, physics is by far a done deal, I guarantee there are quantum photon effects we haven't discovered yet, and we've discovered a lot that weren't predicted by any theory. So I think that's one way to gauge our understanding of quantum particles--how many discoveries have there been which were a "complete" surprise?

Given that such "new" quantum effects have appeared unexpectedly, what does that do to any quantum philosophy?
The philosophical problem might be connected to how the theories we have, don't tell us all that much in terms of what to expect. Unlike Newtonian mechanics which generally does.