What is action in human terms?

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What is "action" in human terms?

A friend, humanist by profession, asked what is "power"? Well, that was easy to explain in human terms. You do a certain amount of work, you use a certain amount of calories, you can do you work slowly, during one day, or you want to do it in one hour. Then you need more power.

But the next question was about "action". To say action is energy times time, or momentum times displacement does not fly. That is good in formulas, but it tells nothing to a humanist.
To say "Planck constant is the quantum of action" does not help either.

So, how to explain what is action so that it will be understood and "felt" by a humanist or engineer? How we can relate it to our daily experience and/or engineering?

What is action philosophically?

Any ideas?
 

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  • #2
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Everything in our world obeys the rule of least action.

Maybe you can explain it as usual need to spend least energy and time doing any human task. You want the job done for the shortest possible time and spend least possible resources.
 
  • #3
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Everything in our world obeys the rule of least action.

So, action seems to be an even more fundamental concept than time and/or energy? What mechanisms in us, human beings, are directly sensitive to action? Are there any? We are sensitive to time in an obvious way, through the rythms around us and in us. We are sensitive to energy we spend. Do we have sensors for action?
 
  • #4
Siv
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Action is how the organism interacts with its environment, in what it imagines to be free-will :smile:
 
  • #5
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So, action seems to be an even more fundamental concept than time and/or energy? What mechanisms in us, human beings, are directly sensitive to action? Are there any? We are sensitive to time in an obvious way, through the rythms around us and in us. We are sensitive to energy we spend. Do we have sensors for action?

http://en.wikipedia.org/wiki/Principle_of_least_action" [Broken] is fundamental, yes. However, I don't think we have "sensors" for action, just because everything follows the principle, and we can "see" only differences.

The principle translates in the human world indirectly, i.e. energy -> money (or resources in general). But since this translation is not fixed, we can disobey the translated principle and say we want more money for doing the job. The boss, however will tend to force the principle from the other side, sometimes until the workers decide to strike.
 
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  • #6
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Action is how the organism interacts with its environment, in what it imagines to be free-will :smile:

That's seems to me to be a rather cryptic statement ....
 
  • #7
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That's seems to me to be a rather cryptic statement ....

Maybe not. Maybe what we call free-will is just our inability to "see" the principle of least action directly.
 
  • #8
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However, I don't think we have "sensors" for action, just because everything follows the principle, and we can "see" only differences.

What about our brains, neurons firings, maybe DNA etc. Is the action hardwired there? I know, there is an "action potential", but is it related to action of the least action principle in some roundabout way?
 
  • #9
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Concernig the history of concepts I know very instructive books by Max Jammer about the concept of force, of mass. Did someone write about the history of the concept of action and about its philosophical meanings? After all there is no such thing as the "absolute quantum of energy", but there is quantum of action!
 
  • #10
Siv
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That's seems to me to be a rather cryptic statement ....
It probably was, what do you want elaboration on ?
 
  • #11
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What about our brains, neurons firings, maybe DNA etc. Is the action hardwired there? I know, there is an "action potential", but is it related to action of the least action principle in some roundabout way?
The principle of least action is hardwired in everything. Read the wikipedia article. The link is in my previous post.
 
  • #12
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The principle of least action is hardwired in everything. Read the wikipedia article. The link is in my previous post.

Wikipedia tells us nothing about where are our sensors of action. It seems we can choose arbitrarily what quantity we want to minimize or optimize. Is free will, as Siv have mentioned, exactly this: ability to disobey the principle of least action? If so, at which level do we have it? On molecular level? Higher? Lower?
 
  • #13
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Moreover, is the principle of least action an "objective principle"? Or is it just one of the many perspectives through which we, human beings, are trying to order our experienced reality?

In quantum theory we are told that the least action paths are only "the most probable paths", whatever it means. We are also told that "least" rarely the case, that what is important is being "extremal".

Is action an additional dimension? Curled or twisted? Or, perhaps, a discrete one? Fourier related to some circular dimension?
 
  • #14
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Wikipedia tells us nothing about where are our sensors of action. It seems we can choose arbitrarily what quantity we want to minimize or optimize. Is free will, as Siv have mentioned, exactly this: ability to disobey the principle of least action? If so, at which level do we have it? On molecular level? Higher? Lower?

I don't think we have sensors of action. Sure we can have abstract notion of it, but it is not based on everyday knowledge. This is the reason you cannot explain it easily to someone who do not have the required knowledge to build the abstraction.

My explanation was the closest thing I could imagine, but still it is not accurate enough, as the variables in our decisions are not just the time and the energy. So, no we cannot disobey the principle strictly speaking.
 
  • #15
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Ludwig von Mises wrote a book "Human Action" -- not physics but economics. Action is the effort to substitute a less satisfactory state of affairs with a better state of affairs. From this a priori truth, he constructs a whole economic theory of praxeology. It's the bible to the Austrian school of economics. Man is not a particle, he chooses what path to take that brings him satisfaction.
 
  • #16
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Let's leave our human affairs for a while, isn't it funny that action is energy multiplied by time or momentum multiplied by displacement while at the same time we have uncertainty relations between these quantities. Can action be strictly defined and measured even when we have uncertainties as regards its components? Can action be directly measured at all? How?
 
  • #17
ConradDJ
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To say action is energy times time, or momentum times displacement does not fly. That is good in formulas, but it tells nothing to a humanist.
To say "Planck constant is the quantum of action" does not help either.

In very rough terms, the physical "action" is "how much happens" in the course of an event. If the event is a particle traveling from A to B with a certain momentum, that's a certain amount of action. If we then consider the particle as going from A to B with twice the momentum -- or if it goes twice as far at the same momentum as before -- then those events have twice as much action.

You could put it the same way in terms of time and energy, as you point out. So there is maybe an intuitive way to explain what the formulas mean.

As to Planck's constant of action -- I think it's very interesting that each of the fundamental constants in physics has a different character. In this case, the quantum of action is a minimal unit... which seems to imply that there's a minimal "amount that can happen" in any physical event (interaction). In fact, I think Planck once referred to the quantum as "this atom of happening." He was being rhetorical, not making a serious proposal -- but it's an intriguing idea.

It could be that the world is in some sense "made of" atoms of happening or interaction. Certainly that makes sense if we think of the physical world that we (or any possible "observer") actually experiences. Physically, anything like "experience" or "measurement" consists in event-connections between things... and it seems that many of the peculiarities of quantum mechanics stem from the fact that interaction can not be made arbitrarily "delicate". There's always some minimum of action that takes place whenever things interact.

After 1900 it gradually became clear that "atoms" in the traditional sense don't exist -- i.e. tiny, simple units of matter. We can break atoms down into "elementary particles" but there are all kinds of ambiguities about that, because at a basic level a "particle" is some kind of superposition of all the things that can happen to it (all the ways it can interact). So the "quantum of action" may be the closest thing we have to a "simple, basic building-block".

Conrad
 
  • #18
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So the "quantum of action" may be the closest thing we have to a "simple, basic building-block".

Conrad

That may be the case. Yet is not "action" a kind of non-local thingy? First we have least action principle in classical physics. There it gets somehow translated into local Euler-Lagrange equations. But in quantum theory this translation fails. We have path integral and it does not really translates into anything local. Of course we can even procure action principle for Schrodinger's equation or quantum fields, but there it is rather a formal thingy, I think.

So, perhaps, the fundamental non-locality is somehow coded in the concept of action?

Just thinking .....
 
  • #19
apeiron
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Yet is not "action" a kind of non-local thingy?

Surely you cannot have a (local) action without a (global) context. An action is a change or a difference. And it has to happen against some fixed or unchanging backdrop to be detected, measurable and meaningful.

So the general definition is about a local change that is defined as such because there is ALSO global non-change.

Now a bunch of secondary concepts then follow. We have the idea of the smallest possible discernible action (which the planck scale/quantum mechanics and information theory would both have something to say about). We also have the path minimisation principle, the least mean action, which is a statistical and thermodynamic idea as well. So in various ways, physics tries to define "action" in terms of fundamental smallness - the most local possible, and therefore the "least" an action can be and still exist.

But what physics then lacks - because it is always focusing on the fundamentally small, the most atomistic - is a balancing model of the global contexts which allow changes or localised actions to exist.

This is why QM creates intellectual problems. An "observer" - a globally decohering context - is needed to complete any picture based on local actions. And some aspects of any action are found to be irreducibly global/contextual (or non-local).

So the whole notion of action arises out of atomism and the desire to model reality solely in terms of the fundamentally small. But implicit in the very idea of "smallest local flux" must be its antithesis of "largest unchanging context".
 
  • #20
Siv
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Wikipedia tells us nothing about where are our sensors of action. It seems we can choose arbitrarily what quantity we want to minimize or optimize. Is free will, as Siv have mentioned, exactly this: ability to disobey the principle of least action? If so, at which level do we have it? On molecular level? Higher? Lower?
We dont have free-will in the concept of a central homunculus looking at all the CCTV cameras (our sense organs, memory etc) and deciding what to do.

On the other hand, the concept of determinism is not entirely true either. As in you cant predict with 100% accuracy what will happen the next hour, if you were a super-being. Its all probability curves.
 
  • #21
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We dont have free-will in the concept of a central homunculus looking at all the CCTV cameras (our sense organs, memory etc) and deciding what to do.

Of course I can't tell what other people can do or can't do, but I feel like I have a free will to choose between different options of behaving, for instance ethically or non-ethically. Sometimes it is almost automatic, but sometimes it is rather difficult and evidently against the "least action" principle. Of course moral choices are far from physics, but philosophy is also dealing with such choices - or so it seems to me.

You may say that free will is an illusion, but then everything can be said to be an illusion. That we do not have free will can be an illusion as well.

But back to action: do we ever meet in physics Fourier transformed action? In path integral formulation of quantum theory? Is action the Fourier transform of quantum phase? Is that why it is quantized?
 
  • #22
Pythagorean
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I always thought of Force as action. I can't think of any action that isn't accompanied with force.
 
  • #23
Siv
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Of course I can't tell what other people can do or can't do, but I feel like I have a free will to choose between different options of behaving, for instance ethically or non-ethically. Sometimes it is almost automatic, but sometimes it is rather difficult and evidently against the "least action" principle. Of course moral choices are far from physics, but philosophy is also dealing with such choices - or so it seems to me.

You may say that free will is an illusion, but then everything can be said to be an illusion. That we do not have free will can be an illusion as well.
Well, what we feel like may be important to us, but is really no indication of the truth.
Evidence suggests that our brains are shaping our decisions long before we become consciously aware of them. You must know about the 1983 Libet study. Libet measured the activity of people's supplementary motor area, a part of the brain involved in planning movements. Astonishingly, he found that this area became active a few seconds before the person felt a conscious desire to do a particular action (in his study, the action was to press a button at a time of their choice, and to remember the position of the second hand of a wristwatch when they first felt the urge to move).

The same concept was more elaborately studied in 2008 at the Max Planck Institute and confirmed the earlier results.
 
  • #24
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You must know about the 1983 Libet study. Libet measured the activity of people's supplementary motor area, a part of the brain involved in planning movements.

I know about this stuff. It is certainly interesting, but it does not prove anything about free will since we do not know how our free will acts. Thinking that our free will has something to do with what we are conscious about is and that is mechanical is a real stretch. Moreover the interpretation of Libet's experiment depends on the free will of the interpreter - see e.g. http://www.newscientist.com/article/dn17835-free-will-is-not-an-illusion-after-all.html" ;)
 
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  • #25
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I know about this stuff. It is certainly interesting, but it does not prove anything about free will since we do not know how our free will acts. Thinking that our free will has something to do with what we are conscious about is and that is mechanical is a real stretch. Moreover the interpretation of Libet's experiment depends on the free will of the interpreter - see e.g. http://www.newscientist.com/article/dn17835-free-will-is-not-an-illusion-after-all.html" ;)

There was no decision in these experiments. It was reaction. Also every computer can be programmed to "disobey" the least action. Do they have free will (whatever it is)?
 
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