studiot

Put simply The Correspondence Principle basically says that whenever a physical theory is displaced by new theory, the new theory must 'correspond' to the old theory. That is it must match the old theory in those realms of physics that have been tested (by experiment). Variations/ corollaries of this are RTFM (read the frigging manual) and the so called Domain of Application that every lecturer says at the outset of a series of elctures and everyone promptly forgets about. So what does this mean for the double slit ? Well what has been tested ie what actually happens? That is what do we actually observe and what does it depend on ? What was the old theory and where does meet and where does it fail the observations ? And what is the new theory - obviously in this case the quantum theory - and how does it meet both the conditions the old theory satisfies and those it fails ? Well I contend that too many modern explanations actually degrade the old theory in order to make it look bad. And of course you have to ask which old theory ? A wave theory ? Well there were several levels of wave theory and elementary texts match the simple wave theory of Huygens and Fresnel against quantum statistics. In fact there are several levels of wave theory, each more exact but more difficult The first theories due to Grimaldi and Marcus we not of wave interference but wave diffraction. Grimaldi actually coined the word diffraction. Undergraduate level Physics today makes a distinction between diffraction and interference. More advanced work does not. Instead the fully rigorous vector wave theory is based on Maxwell's equations and the boundary conditions associated with the obstacle (in this case the double slit). The boundary conditions are used to calculate a field scattered by the obstacle. The origins of this scattered field lie in currents induced in the obstacle by the incident field. The scattered field is vectorially combined with (allowed to interfere with) the incident field to produce the resultant diffracted field. This is a very difficult approach, the simplest solutions being the Kirchoff -Sommerfield Integrals. The normal undergraduate approximation theory is a scalar theory where the Huygens-Fresnel wavelets interfere to produce a new wavefront. Even this is difficult and produces the Huygens-Fresnel Integral. An alternative modern treatment involves solving the Helmholtz Equation to find the Gaussian Wave . This can be carried into laser territory. The problem is that all these methods introduce their own difficulties, for example the backward wave in the Huygens method, which is simply ignored as it is not observed. Bit it was necessary to move on from Grimaldis original (though a nobelworthy effort in 1665) to the nearly accurate version introuced by Young in 1801 The intensities and widths of Grimaldis laight and dark zones dod not correspond to observation, in particular the central one was too big.

Its not the actual words I care about but the enormous and significant differences in the meaning I outlined. So can you suggest alternative words for my terms coerce, force, and constrain. If these alternative can be shown to represent the different ideas better than I will happily adopt them.

I give no quarter to vthose who take a word they did not invent, create a special meaning for it, and then fail to make their special usage plain when they trot it out infront of others. To coercion implies a clash of at least two separate and distinct wills, possibly accompanied by threats before the event, but not necessarily involing itself in the event. Forcing implies a direct intervention in the event and its course, perhaps changing the circumstances (boundary conditions) and thereby changing the event. This can be and is given mathematical status.

Acceleration misconceptions. https://spark.iop.org/many-students-think-objects-acceleration-always-direction-which-object-moving

Yes I think so, sort of. Every action must be the result of free will, determinism, something else, or some combination thereof. Take the modern automatic half barrier level crossing. There is coercion in play. The law says that drivers must stop and wait for the barrier to lift. It is coercion because of the will of Parliament, combined with a threat. However it is not full forcing and we have recorded notable accidents over the years where a driver has chosen to act to the contrary and try to drive around the barriers. In the old fashioned legal philiosophy, yes although compulsion (coercion) still applied it was considered better to "Make it impossible for the driver to do anything else" So a man would come out and physically close off the entire road by shutting very solid heavy gates so no one could drive through until they were reopened. This is not probabilistic but where totally impartial circumstance forces or dictates or determines the course of action. What is your opinion ?

There is yet another aspect to this. Coercion has been mentions several times in these thread. A while back I said I preferred the much more general term forcing, of which coercion is a small subset with some additional characteristics. I'm glad to see you back up your input with examples. The case of the railway evel crossing forms an admirable example of the difference between forced and non coercive (or not coercive) activity. I also prefer non coercive to uncoercive, as an expression.

@Luc Turpin I think this is the time to bring in the correspondence principle and see how it bears (not koalas 😀) on Young's slits. Have you heard of the correspondence principle ?

I notice you carefully avoided the mathematics I picked out for you in @joigus' post.

For the same reason that early mediavel cathedrals fell down, until they discovered side thrust and put ties or buttresses into the architecture. The bottom member of a standard roof truss for a double pitched roof is just the same.

Joigus has answered you Interaction is the correct word. Luc is one of the few percentage of new arriivals who come here with an open mind and a willingness to listen and learn, rather than the "big I am and know it all" attitude so many arrive with. As such I am trying to show him the respect he deserves, particularly observing the rules about (mainly) mainstream answers. And also to acknowledge things we genuinely don't know. +1 for a model answer from joigus, even thjough I don't quite agree with all of it. The question of 'what inteferes with what?' if there is only a single wave function is still open. In a quantum system there are many wavefunctions so how do we construct the system wave function ? As noted for Luc's sake please preserve the difference between a wave function (appropriate here) and a wave. Aldo the discussion about what is a wave function might be relevant for Luc as it is such strange beast.

Well this human minds very much and finds it insulting to blind folks. You have come full circle to the twaddle you started with, despite having acknowledged you were wrong and others had a point or three, along the way. I'm out of here.

I think you need to peer a little more deeply into the mathematics.

6.4C above incoming ? SJ was looking for 14C That copes incoming air 7.6C or above. Currently the air outside has risen from 0C first thing this morning to 7C now. Perhaps that explains why what most estate agents in the UK would call a good sized double bedroom that tend to have 2.5kw wet radiators these days. Yes you could get preheated air from somwhere else and then you might get away with a smaller heater, but of course you would need another heater to preheat it.

What's spooky about it anyway ? It's spookyness certainly fails my ground pepper test.

You have a good memory +1

Humans love to classify thing into 'pigeonholes', but Nature rarely plays ball with our efforts. It is easy to think that abstract things can be fact or fiction. However one test of 'reality' is the question can it influence our real world ? The problem comes when I note that Harry Potter (fiction) has definitely influenced the world more than I have. It is said that the writings of Swift (a factual character) about Gulliver ( a fictional character) was all about the perceptions in our minds. And who is the more famous, Swift or Gulliver ?

Chapter 15 of the second book I recommended by Prof Mills is all about this. Ch15 treats the data, the observer, the observation, the 'watcher', the role of consciousness, superposition, what is included in the wave function and more. The maths is not as difficult as Joigus' although he still makes makes use of some specialist quantum notation - the bra and ket notation, identified by the < and > symbols.

I am skeptical about this. 600w is a very low powered heater and it depends upon the construction of the room and what you mean by warm. [aside] One thing I noticed about heat pumps is the impression that a source- to air pump (ie one which drive a non electric fan heater) generates an impression of warmth much more quickly than source -to-water pumps. This also applies to electric fan heaters and fan assisted radiators. They only heat the air and the effect dissipates very rapidly when the heat is turned off.

@iNow is correct, of course animals can see and moreover distinguish colours. Since there is a huge range of animals it would not be suprising to find there is a range of capability in this respect. You know that a dog will chase a thrown bone or stick but can distinguish between bones and sticks. Here is some scientific testing to show that they can distinguish some colours as well. Ok so you cup is red. Now that you have recorded this fact online that fact (and the cup) will still be there if the ground suddenly opened up and swallowed you.

Did you understand this ?

That is not a definition, that is one example that would satisfy (i expect) most definitions. But obviously there would be many examples that would satisfy one definition whilst not satisfying another.

Personally I think slit experiments are about the worst experiments for the study of quantum v non quantum effects. There are just so many factors to consider. There is the number of slits, the size of the slits, the spacing of the slits, the distance from the source to the barrier and from the barrier to the detector, there is the positioning of the detector, there is the thickness of the barrier, there is the 'sharpness' of the edges of the slits. What happens when there is no detector ? You can find the answer to this out with water waves, but not with light waves.

I am not a fan of Ryle. His cricket match example, for instance, suggests to me that neither Ryle nor the author of his Wikipedia article has ever played cricket in their lives. As regards you runner, yes I would contend that the runner did 'do' two things, which are different. It may not have been necessary to break to world record in order to win. Equally 8 seconds may not have been a winning time as another may have run faster. As regards the exam, the candidate can obviously decide (free will) to fail the exam. Conversely the candidate can decide not to fail the exam (but to try hard) Connected to this, and just like the runner, is another event. Pass or fail. I do agree that limiting causes to neurological impulses microseconds before an action is a very sever restriction of what constitutes free will. What about my comments on coercion and external constraints ?

Nice to have an engineer casting his MK 1 eyeball over the figures. +1

So, OP, what is your definition because I couldn't find one in your opening post. So somewhere along the line I did agree that it would be a good idea to understand it.