# - FEEDBACK- One of the most powerful , yet varied tools in our experience !

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In science , possibly one of the most varied , yet most flexible tools . It's prominence in the current 'Electronic age ' gives us insight as well a mechanism to examine our surroundings .' " FEEDBACK "

However it finds its place , widely spread , in Nature, Industry , Management as well as Electronics.

Can we learn interesting points and insights , from the action of Feedback " ? There appear to be a range of differing effects , with different types and styles of feedback ( say , positive, negative, damped, loose, levels of, etc )

Are there uses for understanding these differing effects. Namely , in understanding scientific observations , in the universe at both the very large , and very small scales, and In between ?

Wikipedia link to Feedback -: https://en.m.wikipedia.org/wiki/Feedback

Also feedback types :- Listed under internal link to . Feedback(disambiguation).

.

.

Mike

Edited by Mike Smith Cosmos

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. Three examples of Feedback , which could be brought to the fore , as they are in common usage and relate easily to science are :-

(A) Electronic Circuits .,(B) Mechanical Machines . , © Climate on a world scale

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A) an electronic amplifier , could be a Valve, transistor , or other amplifying circuit . Here devises were/are called on to take a small signal and increase its level to a higher more useful value . Say a few milli volts to a few Volts , or a few milli amps to a fraction of an amp. The signals are usually A.c( alternating current ) . A factor of amplification can run from say times 5 ( x5 ) to times 2000( x2000) , all from a single device , say a valve or a transistor. When I first was taught this , I thought ' wow' this is amazing , almost something for nothing . Say 1 volt alternating signal to say 500 volts by one stage . This was caused by affecting the flow of electrons ( current) in a valve or transistor via an intermediate electrode ( grid or base) .

However there was a downside , it was not reliable , not stable .

By feeding a part of the output signal BACK into the input the reliability went up Astronomically, but the multiplying gain went down dramatically ( say to x 2 or x30 , no longer x500 ) . ( The feedback signal has to be subtractive to give stability, hence the expression ' Negative Feedback ' ) .( Positive feedback is another story ! )

So lesson number one Feedback can bring stability , reliability , control at the expense of GAIN .

It could be argued that similar principles apply across all feedback systems .

B) Machines in both the early engines had spinning wheels which regulated the speed of rotation , nowadays sensors and controllers or regulators .

C) It has become the centre of much discussion recently as to feedback systems being present in the worlds climate systems .

Mike

Edited by Mike Smith Cosmos

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The negative feedback signal ( in other words the message sent to the input ) has a characteristic shape , when plotted against time .

( see below) .

Whatever the subject under control ( by feedback ) , say the amplification of sound or music . Control of motor speed of rotation , balance of water temperature in a hot water system or a sea ocean . The feedback usually follows a response curve as below .

In other words , it takes a finite time for the feedback message to get through ( Rise time) , it often overshoots it's intended effect , ( over shoot ) it then settles down after a bit of action and reaction. ( ringing ) .

Measure this against some feedback you may give verbally to someone ( which you offer genuinely trying to help , but they consider as criticism ), they may react at first, you say , well I did not mean it like that , and with a little back and forth , the feedback settles down . ( hopefully , or you get a black eye ) .

( the maths for this feed back ( considered against a time backdrop) , is available , but is a bit daunting. )

Mike

Edited by Mike Smith Cosmos

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We could introduce the idea of simple but different feedback type. Say Positive feedback . This is where the output of a system is returned ,in part , to the input of the system . Not in a subtractive ( negative ) way , but in a additive ( positive ) way . Namely Positive feedback.

This has the opposite effect , to some extent , to ' negative feedback ' . If this was an audio amplifier, the amplifier would re- amplify the existing amplified signal. Phenomenal gain will be achieved , the signal will be deafening . In addition it is likely to be out of control , namely unstable. This you may have heard when a sound system microphone ,picks up its already amplified sound . A high level , screech , going from tone to tone . This is uncontrolled positive feedback . Controlled positive feedback can produce accelerated effects. Explosive in nature.

Already from this simplistic approach to feedback we may be able to see why certain things happen , some in nature , clearly under control. Other things happen where explosive expansion is required.

The world wide climate system probably has a taste of both sorts of feedback ( 'negative feedback ', stable ,controlled , 'positive feedback ' powerful, storm like , uncontrolled ).

Similarly , I am sure these will crop up in the universe as a whole , both very large and very small and many-things in between. What also becomes clear ,is that simple ' cause and effect ' is likely to be tempered with various feedback systems , giving different predictions and results , rather than linear ' cause and effect' . Of course , this may end up in compounded loops , one within the other , and of different type. It is evident that the whole system can get very complex , and the maths complicated .

Mike

Edited by Mike Smith Cosmos

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Is that positive or negative feedback?

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I was raising the question , " Could it be that some things we find hard to understand , as regards their operation, may have a feedback system involved. " . As explained in previous posts of this thread that :- ' feedback can bring into effect , counter intuitive outcomes, which are not always obvious , and could be different to calculate , because of complexity of nesting feedback loops. '

Armed with this quest , it could be that research into a difficult subject, ' like Climate ' and other difficult to understand subjects , that are not in an immediate " Cause and effect linear connection " ( Eg I do this , and that happens ) .

Mike

Is that positive or negative feedback?

Neither ! Neutral . ( at this stage ,anyway , things could go either way )

Mike

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I was raising the question , " Could it be that some things we find hard to understand , as regards their operation, may have a feedback system involved. " .

I would venture to guess that virtually real systems have feedback of some sort. It's only when we idealize some models (e.g. "assume no friction") that we ignore it.

I would also venture to guess that virtually all scientists are aware of this. Especially those doing climate research.

Armed with this quest , it could be that research into a difficult subject, ' like Climate ' and other difficult to understand subjects , that are not in an immediate " Cause and effect linear connection " ( Eg I do this , and that happens ) .

This sentence seems to be incomplete. that are not in an immediate " Cause and effect linear connection" ... what?

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I would venture to guess that virtually real systems have feedback of some sort. ( A) It's only when we idealize some models (e.g. "assume no friction") that we ignore it.

(B) I would also venture to guess that virtually all scientists are aware of this. Especially those doing climate research.

© This sentence seems to be incomplete. that are not in an immediate " Cause and effect linear connection" ... what?

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(A) I am not sure , reaction forces , can be included in the context of " Feedback " , although I agree it may have a similar result. I was thinking more in terms of a 'signal or active force ' that can be taken hold of , processed in some way or other , and returned as an active input to the system under consideration, of a similar nature . So really applying to active systems .

(B) Again , I am not sure all scientists see the climate as a total feedback system . It took James Lovelock a lifetime to convince the world , his ' Gia ' hypothesis as climate being part of a total system .

( C) I agree this sentence is clumsy and awkward . I thought that after I wrote it .

I am not sure , I know what a phrase is , that describes a mathematical sequence WITHOUT any feedback.

I am trying to describe a forward moving sequence . Eg a. ( the cause ) originates b processes may be c. d and e are further processes and f, is the consequence, resultant (effect, ) or whatever happens as a result of a, originating. ( with no portion of f feeding back to a, )

Contrarily a feedback system does feedback a portion of f to a .

I am not so sure that scientists and non scientists , will naturally think about ( negative and positive feedback ) as a solution or ingredient. The reason I suggest this , is because it is slightly counter intuitive .

The intuitive is " more in makes more happen " . Whereas feedback works in a round about way .

Mike

Edited by Mike Smith Cosmos

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(A) I am not sure , reaction forces , can be included in the context of " Feedback " , although I agree it may have a similar result. I was thinking more in terms of a 'signal or active force ' that can be taken hold of , processed in some way or other , and returned as an active input to the system under consideration, of a similar nature . So really applying to active systems .

I was absolutely not talking about reaction forces, since they are not examples of feedback, and have no desire to delve into that morass again.

(B) Again , I am not sure all scientists see the climate as a total feedback system . It took James Lovelock a lifetime to convince the world , his ' Gia ' hypothesis as climate being part of a total system .

You may overestimate the level of convincing that has taken place. I think Gaia is rejected scientifically because the single organism part of it is nonsense, not because of the notion of feedback.

( C) I agree this sentence is clumsy and awkward . I thought that after I wrote it .

I am not sure , I know what a phrase is , that describes a mathematical sequence WITHOUT any feedback.

I am trying to describe a forward moving sequence . Eg a. ( the cause ) originates b processes may be c. d and e are further processes and f, is the consequence, resultant (effect, ) or whatever happens as a result of a, originating. ( with no portion of f feeding back to a, )

Contrarily a feedback system does feedback a portion of f to a .

I am not so sure that scientists and non scientists , will naturally think about ( negative and positive feedback ) as a solution or ingredient. The reason I suggest this , is because it is slightly counter intuitive .

The intuitive is " more in makes more happen " . Whereas feedback works in a round about way .

Mike

I would be hard pressed to name a scientist I've met whom I thought didn't understand feedback. Mostly because experimental atomic physicists tend to servo-lock their lasers somehow, which is a feedback system. We all understand basic electronics, and have built feedback circuits. I can't imagine electrical engineers not knowing it.

Lay people may not know it by name, but I'll bet a lot of them know in general terms how a thermostat tied into the heat or AC works, or how to drive at roughly constant speed in a car. Feedback is widespread.

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I was absolutely not talking about reaction forces, since they are not examples of feedback, and have no desire to delve into that morass again.You may overestimate the level of convincing that has taken place. I think Gaia is rejected scientifically because the single organism part of it is nonsense, not because of the notion of feedback.I would be hard pressed to name a scientist I've met whom I thought didn't understand feedback. Mostly because experimental atomic physicists tend to servo-lock their lasers somehow, which is a feedback system. We all understand basic electronics, and have built feedback circuits. I can't imagine electrical engineers not knowing it.Lay people may not know it by name, but I'll bet a lot of them know in general terms how a thermostat tied into the heat or AC works, or how to drive at roughly constant speed in a car. Feedback is widespread.

Well I was meaning the feedback aspect of Lovelocks hypothesis , which did make a lot think .

Yes you are right about scientists knowing what feedback IS . And particularly engineers , as you say , with electronics . I agree . What I am suggesting is :- it is not the first thing in people's minds , or scientists for that matter , or anybody else to think :- " I wonder how FEEDBACK is making " this or that work " . Anybodies First thought is " What causes that to happen ? " cause and effect , it's fairly natural . Not " I wonder what sort of convoluted feedback nests make ' such and such '. happen . We all go for the easy option. " what caused that to happen ? That's what I was trying to get at with my previous ' gibberish '

Eg I put the water in the soil and it makes things grow big and tall. Not . If I put water in the soil , it will penetrate to a level of soil which will dissolve minerals so as to make the liquid in the soil be so concentrated as to cause reverse osmosis to suck the moisture of the plant and it wilts and does not thrive ! ...then there are no plants dying any more , so no concentrated solution builds up, so there is no longer any reverse osmosis , so plants thrive again and so a feedback system has reset the environment ( or something similar to that effect........ Hope that is not more gibberish .. What I am trying to say , we normally take the easy thinking option. .. Namely ... ( this causes that ) .

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Thus :-

It may be already seen in this discussion , that feedback is generally accepted as a scientific principle , by the scientific community and is fairly well widespread . And therefor useful as a possible tool in research ?

(1) That , negative feedback brings control and stability : thus with things to do with life and the environment , where stability and control is a ' must ' , we could look for feedback loops of a negative feedback variety in the environment , and in life itself . ?

(2) That positive feedback brings colossal gain , and accelerated explosions : thus we could look for applications of positive feedback in applications of a need for power, explosions , massive gain. Possibly areas incorporating positive feedback , are astronomic in type .

Possibly:- Big Bang, supernova, black holes, expanding universe , star birth , the sun , Jupiter, space travel, ..... May be areas where positive feedback can possibly be found ?

Mike

Edited by Mike Smith Cosmos

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What I am suggesting is :- it is not the first thing in people's minds , or scientists for that matter , or anybody else to think :- " I wonder how FEEDBACK is making " this or that work " . Anybodies First thought is " What causes that to happen ? " cause and effect , it's fairly natural . Not " I wonder what sort of convoluted feedback nests make ' such and such '. happen .

I think you are wrong. No one takes such a simplistic view of things.

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!

Moderator Note

Mike, do you have a specific point here? This thread, like many of your other ones, is so broad and vague as to make real discussion almost impossible. Requests to define and refine what you are talking about only seems to result in more tangents and less sense. This is a problem of yours that needs to be resolved. If you don't want to have all of your threads shut down, then you need to make a better effort at detailing exactly what they are about in as precise and scientific a manner as possible.

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I think you are wrong. No one takes such a simplistic view of things.

!

Moderator Note

...make a better effort at detailing exactly what they are about in as precise and scientific a manner as possible.

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I am sorry . I thought that is what I just did in post # 11. I will try and make it more succinct and scientific.

Main point -:

" Feedback ( negative and positive ) has been proven extremely scientifically , beyond doubt, by its widespread use in Electronics, which is fully explained by mathematics. ( Electronics has been my life's occupation , so I know what I have just said about feedback in Electronics , as fact). Thus , I would have thought that, it behoves all sciences to look for such feedback mechanisms in other scientific disciplines as it is 'likely ' to be fundamental there also . Such as Astronomy, Biology, Earth Science , Engineering, and other disciplines. "

Footnote to main point :-

" They may already be doing this . Great . Keep going . We are talking about :-

Control and stability ,on the one hand ( negative feedback ) .

Immense dispersion and power on the other hand . ( positive feedback ) . Not terribly controlled or stable! "

This is my point . I am sorry if I have not made that clear as that being the main thrust of this thread .

Mike

Edited by Mike Smith Cosmos

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Main point -:

" Feedback ( negative and positive ) has been proven extremely scientifically , beyond doubt, by its widespread use in Electronics, which is fully explained by mathematics. ( Electronics has been my life's occupation , so I know what I have just said about feedback in Electronics , as fact). Thus , I would have thought that, it behoves all sciences to look for such feedback mechanisms in other scientific disciplines as it is 'likely ' to be fundamental there also . Such as Astronomy, Biology, Earth Science , Engineering, and other disciplines. "

And we do this, so what's your point?

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Possibly areas incorporating positive feedback , are astronomic in type .

Possibly:- ... black holes

So this is one example where negative feedback is known to be important. There is thought to be a maximum rate at which black holes can grow. If a very large amount of matter starts falling towards the black hole then it will be heated (by friction) and generate huge electric and magnetic fields. The heat will blast away some of the material, the spinning electric and magnetic fields will create massive jets of material at the poles. At some point this stabilizes and the black hole accretes at a fairly steady rate.

Is that the sort of thing you are thinking of?

There are, I am sure, many other examples. So is the purpose of this thread to gather and understand such examples?

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So this is one example where negative feedback is known to be important. There is thought to be a maximum rate at which black holes can grow. If a very large amount of matter starts falling towards the black hole then it will be heated (by friction) and generate huge electric and magnetic fields. The heat will blast away some of the material, the spinning electric and magnetic fields will create massive jets of material at the poles. At some point this stabilizes and the black hole accretes at a fairly steady rate.

Is that the sort of thing you are thinking of?

?

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I love your description. Is this picture , what you are describing ? I would like to tease out in descriptive terms , how the feedback comes into play? I can hear an echo of it there in your description . Do you have any ,other possible comments , how the control and stability ( negative fb) or the explosive and powerful nature ( positive fb) , come in to play . It sounds to me , that one of the periods of negative feedback are with the stable time of accretion ? Perhaps the collapse toward a black hole has an element of positive feedback ?

Quote

There are, I am sure, many other examples. So is the purpose of this thread to gather and understand such examples unquote

Yes , I would love to hear of other examples ( of feedback ) in astronomy/cosmology . And indeed in other disciplines.

Mike

Edited by Mike Smith Cosmos

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There are, I am sure, many other examples. So is the purpose of this thread to gather and understand such examples unquote

Yes , I would love to hear of other examples ( of feedback ) in astronomy/cosmology . And indeed in other disciplines.

Mike

This is Going to be a hideously convoluted thread if more than a couple of example are being discussed. Might I suggest discussing biology in a biology thread, astronomy in an astronomy thread, and physics in a physics thread, etc?

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.I am not so sure that scientists and non scientists , will naturally think about ( negative and positive feedback ) as a solution or ingredient. The reason I suggest this , is because it is slightly counter intuitive .

The intuitive is " more in makes more happen " . Whereas feedback works in a round about way .

I realise the discussion has moved on, but I believe this needs addressing. You repeatedly make posts in which you question the wisdom of how you think the rest of the world, or subsets of the rest of the world, think. In most instances you are wholly wrong about how those subsets think.

If I didn't think about feedback loops in my work, both from the technical and the social aspects, I would be barely competent. I don't believe I am exceptional.

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This is Going to be a hideously convoluted thread if more than a couple of example are being discussed. Might I suggest discussing biology in a biology thread, astronomy in an astronomy thread, and physics in a physics thread, etc?

Sure, if the response is such that it is necessary . However , it might well be that only a couple of responses happen per discipline . In which case , I would think it more meaningful , in the mean time, rather than fragment the subject , to continue in this thread .

Strange has kindly introduced an example where , feedback seems to stabilise a black hole in a certain accretion of matter . I would presume, ( negative feedback ) . Also plumes ascending from the poles , being so immense could have an element of ( positive feedback ) so as to generate that sort of energy / explosion. However , my knowledge of this cosmic activity is insufficient to be in any way sure?

There are plenty of other evidences of stability and explosive forces , however , that does not necessary mean that feedback is responsible .

The sort of feedback I am used to in electronics is one of mid range energies . Namely signals that enter a device . Power or signal levels are amplified. A proportion of the amplified signal is ' Returned ' to the input having some form of process enacted on it . This returned signal if it has the effect of reducing amplification is considered Negative and will act as a control and stability . Should the signal return be additive it is considered Positive and will have the effect of a run away explosion of amplification .

With this electronic model . At a first pass it becomes clear why settlement and control is evidence of Negative Feedback

And explosive amounts of signal or energy points to Positive feedback .

HOWEVER when the return path is itself a complicated or complex function , things are NOT so ,cut and dried. In fact , there is available , every variation imaginable, using further electronics in the return path, . ( hence my comment of a very comprehensive tool. ), however, this is where the maths goes into orbit, loopy or A.W.O.L.

But keeping it simple it would be interesting to see any examples , others have come across , in differing disciplines . The simple ones are likely to have survived in the main , I would have thought. The difficult or complicated examples probably fall into the category of mutation.

I am grateful for the black hole example by Strange .

Maybe. - Ophiolite - has an example ,

Although geology examples may be harder to pin down . However there are examples of explosive Volcanic erupting . As well as millions of years of stabilised time periods where one type of species dominated ( eg Devonian, Cretaceous, dinosaurs in the Jurassic period ) whether these just happen or they stabilise , to be dominated by one species , I am not sure ?

I realise the discussion has moved on, but I believe this needs addressing. You repeatedly make posts in which you question the wisdom of how you think the rest of the world, or subsets of the rest of the world, think. In most instances you are wholly wrong about how those subsets think.

.

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I do not , for a moment mean to pass disrespectful , aspersions as regards professionals who know far more of their subject than I ever will. I am in fact asking such experts or professionals for possible examples of where it is possibly feedback showing itself . As all have expressed . It is all over the place . That is fine , I , we and everybody , is saying a similar story .

My point is NOT whether it exists but , how is it showing itself . And because it is harder to spot than plain " cause and effect" , have the professionals any examples , that may be enlightening, if only to me and maybe others. I remember the first time I heard ' El Nineo ' explained with its effect on world wide weather , I found it intriguing. I think that is an example of feedback ( I think ) .

Is that the sort of thing you are thinking of?

There are, I am sure, many other examples. ?

.

One or two more like that one , would be great !

------------------------------------------ -------------------------------------------- ----------------------

Mike

Ps

Animals Do it.

Edited by Mike Smith Cosmos

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This thread made me think of back-reaction, which I guess is a kind of feedback.

In field theory, say classical electrodynamics or general relativity, one uses test particles. That is particles that we assume have an infinitesimally small effect on the background field. This is a reasonable assumption for many systems, and allows us to make progress. However, for the full theory one would need to take into account the field generated by the test particles and how this effects the system. The motion of the particle influences the background field which influences the particle's motion and so on...

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Animals Do it.

I was searching for some pictures from a lecture I once saw about hypothetical and random "genetic" systems, built from just 7-10 "simple robust chaotic" operators, which produced a stable complexity of outputs, in a surprisingly high proportion of trials (considering they were random), but I couldn't find any. I did stumble across Chua's circuit, which you might find interesting.

===

And of course there are always the climate type of feedback examples.

...or maybe you could also look at how the Krebs Cycle is regulated by intermediate metabolites.

~

p.s. ...and don't forget to look up pictures of the real "chaos attractors," which these lines below represent.

Edited by Essay

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I am in fact asking such experts or professionals for possible examples of where it is possibly feedback showing itself . ...

Phototropism

Phototropism is the growth of organisms in response to a light stimulus. It is most often observed in plants, but can also occur in other organisms such as fungi. The cells on the plant that are farthest from the light have a chemical called auxin that reacts when phototropism occurs. This causes the plant to have elongated cells on the farthest side from the light. Phototropism is one of the many plant tropisms or movements which respond to external stimuli. Growth towards a light source is called positive phototropism, while growth away from light is called negative phototropism. ...

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They make educational equipment to the demonstrate feedback control in magnetic levitation.

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If one was to take Phototropism as an example . And see how the electronic model of control theory feedback works in nature :-

Diagram of feedback control system

Light input to the system , causes growth output in the plant . The control system is based around ' Auxin '

This works by :-

Auxin distribution controls phototropism. . Sunlight strikes the plant at an angle. Auxin is concentrated on one side, that side is opposite to the side the sun is on , encouraging growth at an angle from the original stem.

With Essay's Climate Diagram , one can see the complications in the diagram , but none the less the similar structure to the simplified Feedback diagram .

-- ( Ed Earl' s ) -- Testing feedback instrument , illustrates how there is a wide range of differing feedback effects , which in turn produce different results in the Output of a control feedback system . This well illustrates that the output can be very different from what one might expect at the output , if the feedback was not there . Thus one could conclude under certain conditions the character of the feedback may provide more of an influence on the output than the main ( Process ) of the system itself .

Similarly ,

-- ( Ajb' ) -- comment shows that there could be a feedback style effect , that could be an additional issue in field theory coming not from the main theory ' process ' but from the ' feeding back ' loop.

I know in electronics , that often the main ' process ' can be a simple Amplification easily read from a component characteristic list , whereas the feedback loop calculations can come from some serious , complicated mathematical analysis of this feedback loop having possible solutions from 0 to infinity , applicable in a similar infinity number of possible configurations . Obviously in design , one wants to achieve a sought after response ( unless one was producing the chaos figures of Mandelbrot sets , as per -- ( Essay's ) -- illustrations of attractors and chaotic behaviour of systems , ) I which case ' the sky is the limit '

However , these comments do illustrate , the seat of influence can be found in :-

BOTH the main PROCESS system AND the FEEDBACK loops .

If not , on occasions , more , in the control arm of the system ( the feedback arms ) . This does offer a region of investigation for answers away from the main obvious processing route .

For example in the CO 2 issue in climate change there are many feedback loops for carbon dioxide . Ranging from plants , to coral reefs , to limestone rock , to endless areas of our Eco system, so I am lead to believe . ( again as illustrated by Essay's , Diagram )

Mike

Edited by Mike Smith Cosmos

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