Rasher Null Posted October 7, 2016 Author Share Posted October 7, 2016 (edited) But there would seem to be no information "about" motion, only the existence of motion itself. This is at the root of my thinking there is a problem. Mind you - suppose in the future it proved possible to deduce information "about" motion by some means of microscopic examination of matter or space. Does such a supposition invalidate what we know already? (Yeah I know I could say suppose we discover little green men sitting on every atom ... but the former supposition (I daren't call it "my" ) is not quite as wild as that.... Note made re phase space.. thankyou. Edited October 7, 2016 by Rasher Null Link to comment Share on other sites More sharing options...
Strange Posted October 7, 2016 Share Posted October 7, 2016 When I say "freeze" them I mean take an instantaneous snapshot, so they are still moving. (It is a thought experiment remember!) No I'm not actually thinking about Zeno so far - that paradox is merely a mathematical one. It sounds exactly like a version of Zeno's paradox ("if we look at them at an instant of time then they won't be moving" IS a statement of Zeno's paradox). 1 Link to comment Share on other sites More sharing options...
Rasher Null Posted October 7, 2016 Author Share Posted October 7, 2016 (edited) I'm not saying they won't be moving in an instant of time! The problem is they are but where is the proof/information etc.... Also I though Zeno was all about repeatedly chopping his step length in half... Edited October 7, 2016 by Rasher Null Link to comment Share on other sites More sharing options...
studiot Posted October 7, 2016 Share Posted October 7, 2016 It sounds exactly like a version of Zeno's paradox ("if we look at them at an instant of time then they won't be moving" IS a statement of Zeno's paradox). Exactly. +1 Rasher Null I gave you a specific answer to your specific question and amplified it with a practical example from real life. The only answer from you was to accuse me of being dismissive. Link to comment Share on other sites More sharing options...
Rasher Null Posted October 7, 2016 Author Share Posted October 7, 2016 Calculus is ....errrrrm classical. Link to comment Share on other sites More sharing options...
uncool Posted October 7, 2016 Share Posted October 7, 2016 Calculus is ....errrrrm classical. What are you addressing here? Link to comment Share on other sites More sharing options...
Rasher Null Posted October 7, 2016 Author Share Posted October 7, 2016 Zeno I guess... Link to comment Share on other sites More sharing options...
Strange Posted October 7, 2016 Share Posted October 7, 2016 I'm not saying they won't be moving in an instant of time! The problem is they are but where is the proof/information etc.... That is why you need to look at calculus and the theory of limits (and why it resolves Zeno's paradox). Also I though Zeno was all about repeatedly chopping his step length in half... "In the arrow paradox (also known as the fletcher's paradox), Zeno states that for motion to occur, an object must change the position which it occupies. He gives an example of an arrow in flight. He states that in any one (duration-less) instant of time, the arrow is neither moving to where it is, nor to where it is not.[13] It cannot move to where it is not, because no time elapses for it to move there; it cannot move to where it is, because it is already there. In other words, at every instant of time there is no motion occurring. If everything is motionless at every instant, and time is entirely composed of instants, then motion is impossible." https://en.wikipedia.org/wiki/Zeno%27s_paradoxes#Arrow_paradox Link to comment Share on other sites More sharing options...
Rasher Null Posted October 7, 2016 Author Share Posted October 7, 2016 (edited) I do know about calculus and limits, honest! The thing for calculus to work is that you DO have the information about motion - in equation form. Objects don't carry equations around with them though, do they? Edited October 7, 2016 by Rasher Null Link to comment Share on other sites More sharing options...
Strange Posted October 7, 2016 Share Posted October 7, 2016 The thing for calculus is to work is that you DO have the information about motion - in equation form. Objects don't carry equations around with them though, do they? The equation is our description of motion. Why would an object need an equation? Link to comment Share on other sites More sharing options...
Tim88 Posted October 7, 2016 Share Posted October 7, 2016 (edited) How is that "unsatisfactory from an information theory point of view"? Would you mind explaining the link to information theory you are claiming? No, you pretend that there is a link to information theory. I told you about Newton's explanation which apparently went over your head, and added the (incomplete) electromagnetic insight that mass -and thus also inertia- relates to field energies, which you also didn't register. Do you know about experiments that demonstrate that space cannot be just nothingness, such as Newton's bucket? How do you explain it, what is acting on the water? (Or, figuratively speaking: what is it that the water "feels", or where does the water "get the information from")? Edited October 7, 2016 by Tim88 Link to comment Share on other sites More sharing options...
Rasher Null Posted October 8, 2016 Author Share Posted October 8, 2016 (edited) I have already posted that I was probably misguided linking to "information theory" simply because I am using the word "information". I've accepted my mistake and moved on! Your quoting of Newton was just a restatement of N1L . Your statements about inertia were not focused on helping me in any way, I felt. And now you won't accept my admission of a mistake in good faith.... But I assume you are still interested in the topic as you are introducing Newton's bucket - which I will look at soon. Thankyou. Edited October 8, 2016 by Rasher Null Link to comment Share on other sites More sharing options...
Tim88 Posted October 8, 2016 Share Posted October 8, 2016 I have already posted that I was probably misguided linking to "information theory" simply because I am using the word "information". I've accepted my mistake and moved on! Your quoting of Newton was just a restatement of N1L . Your statements about inertia were not focused on helping me in any way, I felt. And now you won't accept my admission of a mistake in good faith.... But I assume you are still interested in the topic as you are introducing Newton's bucket - which I will look at soon. Thankyou. I did not exactly quote Newton but explained what he meant with N1L; your question suggested to me that you were not aware of it. My statements about inertia were meant to create more familiarity with the territory, for better understanding. And I simply replied to your comment to me, I had not yet seen your later insight! I think that your question is pertinent and that most textbooks brush over it without sufficient attention. IMO, Newton's bucket belongs in chapter 1 of mechanics text books - but I did not hear about it until after my studies. Link to comment Share on other sites More sharing options...
swansont Posted October 8, 2016 Share Posted October 8, 2016 It's the issue of motion that I am trying to draw attention to. I'm not an information theory specialist - just a layperson. Perhaps my association of "information about motion" with "information theory" is misguided .. but certainly I am puzzled by motion in terms of how it is "coded for", as it were. It seems that the state of motion of an object can only be deduced through observation of that motion, but psychologically at least, this is bizarre and unsettling, I suggest. What is it about the state of matter and or space that "codes" velocity? The details of motion, as observed in any given frame, is dictated by the history of forces acting on an object. Has anyone ever considered what motion is at the quantum level? The notion of defined trajectories loses meaning at the quantum level. Link to comment Share on other sites More sharing options...
Rasher Null Posted October 8, 2016 Author Share Posted October 8, 2016 1) The details of motion, as observed in any given frame, is dictated by the history of forces acting on an object. 2) The notion of defined trajectories loses meaning at the quantum level. Sorry for not being able to get the multiquote to work for me properly yet, so I have numbered your comments for ease of reference. 1) Yes, velocity is a sort of history of forces acting. But how much detail is there in the history I wonder? Classically speaking, there is only one piece of historic information - the velocity of the (rigid) body. In practice of course, objects aren't rigid; also reference frames are not inertial. One imagines that in practice a moving object is subject to all sorts of microscopic wobbles, waves, pushes and pulls etc as it moves at an approximately constant speed in nearly inertial reference frame. N1L is not true in any real sense, because objects aren't rigid and refrence frames aren't inertial. 2) Any theory of everything and all that must surely explain how macro velocity and quantum scales are related ....?? Link to comment Share on other sites More sharing options...
swansont Posted October 8, 2016 Share Posted October 8, 2016 1) Yes, velocity is a sort of history of forces acting. But how much detail is there in the history I wonder? Classically speaking, there is only one piece of historic information - the velocity of the (rigid) body. In practice of course, objects aren't rigid; also reference frames are not inertial. One imagines that in practice a moving object is subject to all sorts of microscopic wobbles, waves, pushes and pulls etc as it moves at an approximately constant speed in nearly inertial reference frame. N1L is not true in any real sense, because objects aren't rigid and refrence frames aren't inertial. Physics deals with what we can approximate well. If you can't model it, you can't model it. 2) Any theory of everything and all that must surely explain how macro velocity and quantum scales are related ....?? Let me know when we have a theory of everything. QM isn't "built" to explain what happens on a macro scale. We already have models for that. Any extrapolation of QM to those situations will look like the classical model. Link to comment Share on other sites More sharing options...
Rasher Null Posted October 8, 2016 Author Share Posted October 8, 2016 Such defeatism! -2 Link to comment Share on other sites More sharing options...
Strange Posted October 8, 2016 Share Posted October 8, 2016 Such defeatism! What are you talking about? You ask a fairly meaningless question, get some replies that are far better than it deserves, and then dismiss everyone's comments. Such pointlessness. Link to comment Share on other sites More sharing options...
studiot Posted October 8, 2016 Share Posted October 8, 2016 What are you talking about? You ask a fairly meaningless question, get some replies that are far better than it deserves, and then dismiss everyone's comments. Such pointlessness. Really, Strange, why waste a good troll? Link to comment Share on other sites More sharing options...
Rasher Null Posted October 8, 2016 Author Share Posted October 8, 2016 "Fairly meaningless" ??!! Link to comment Share on other sites More sharing options...
Mordred Posted October 8, 2016 Share Posted October 8, 2016 But have you studied Hamilton-Lagrangian mechanics and the principle of least action and the calculus of variations? That is what you need to you to obtain an answer. +1 this is the best answer thus far Link to comment Share on other sites More sharing options...
Rasher Null Posted October 8, 2016 Author Share Posted October 8, 2016 (edited) hmmm well I studied the calculus of variations many moons ago, and so I will give Studiot's advice a go in the interest of restoring some good faith into this thread. Might take a while for me to swot up ... Meanwhile Studiot thinks I will obtain an answer .... does that mean he knows what it will be ... I ask because if he told me - or dropped hints to a beginner at it - that might be useful.... Edited October 8, 2016 by Rasher Null Link to comment Share on other sites More sharing options...
Mordred Posted October 8, 2016 Share Posted October 8, 2016 I'll get the formula for you. Link to comment Share on other sites More sharing options...
studiot Posted October 8, 2016 Share Posted October 8, 2016 ........................................................... I am only a novice student of theoretical physics. hmmm well I studied the calculus of variations many moons ago, and so I will give Studiot's advice a go in the interest of restoring some good faith into this thread. Might take a while for me to swot up ... Meanwhile Studiot thinks I will obtain an answer .... does that mean he knows what it will be ... I ask because if he told me - or dropped hints to a beginner at it - that might be useful.... Was that before or after you became a novice at theoretical physics? A good example of 'the troll theorem', if you ask me. Link to comment Share on other sites More sharing options...
Mordred Posted October 8, 2016 Share Posted October 8, 2016 here is the classical version of the principle of least action. In simplistic form the principle of least action can be expressed as. [latex]Action=S=\int_{t_0}^{t_1}[\frac{1}{2}m (\frac{dx}{dt})^2+-mgx]dt [/latex] Between events t_0 and T_1 there is millions of possible paths. Starting and ending at those points. The correct path is the one where the sum of kinetic energy (LHS of the + sign) and potential energy (rhs of the + sign) is lowest. the lowest action path between potential energy and the objects kinetic energy determines the path Link to comment Share on other sites More sharing options...
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