The reality of energy.
in [Relativity]
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From: Y.Porat on 28 Feb 2010 06:50 On Feb 27, 3:54 am, glird <gl...(a)aol.com> wrote: > On Feb 23, 4:48 pm, Occidental wrote: > > > > >< Discussion in physics refer to energy as if it were as fundamental a part of the universe as space, time and matter. In Newtonian mechanics, energy is a useful mathematical abstraction, but not a directly measurable part of any dynamical system. Presumably this is also true in Relativity, despite mass/energy equivalence. > > Before replying to this message I glanced through the previous nine > replies. As I expected, none of them defined "energy". Having long > ago noticed that unless a key word is defined nobody understands what > other people mean when they use it, I defined it thus: > "Energy" is the ability to do work, an ability that is possessed by > organized portions of matter. > > glird -------------------- so what is that thing that enables those 'portions of matter' to do work ?? TIA Y.Porat ----------------------
From: maxwell on 28 Feb 2010 15:05 On Feb 27, 7:38 pm, Bill Hobba <bho...(a)yahoo.com> wrote: > On 28/02/2010 12:05 PM, maxwell wrote: > > > > > > > On Feb 27, 1:13 pm, Bill Hobba<bho...(a)yahoo.com> wrote: > >> On 28/02/2010 5:22 AM, ben6993 wrote: > > >>>> "Energy" is the ability to do work, an ability that is possessed by > >>>> organized portions of matter. > > >>> I have noticed a definition in wiki which seems to imply that energy > >>> is more complicated than the definition above: > >>> "The thermodynamic entropy S, often simply called the entropy in the > >>> context of thermodynamics, can provide a measure of the amount of > >>> energy in a physical system that cannot be used to do work." (http:// > >>> en.wikipedia.org/wiki/Introduction_to_entropy) > > >>> If energy is the ability to do work, but at the same time entropy > >>> implies that some portion of energy is not available to do work, then > >>> how do we re-define that portion of the energy in a system not > >>> available to do work? Is there a more complex definition of energy? > > >> Indeed there is. The modern definition is based on one of the most > >> beautiful and useful theorems in all physics (and indeed in math IMHO - > >> but I am biased towards mathematical physics) - Noethers Theorem:http://en.wikipedia.org/wiki/Noether%27s_theoremhttp://www.mathpages.... > > >> Energy, by definition, is the quantity associated with the time symmetry > >> of a system. Under this definition it is automatically conserved. It > >> is also seen that energy conservation is basically a tautological > >> consequence of that time symmetry - in systems that don't have it (eg > >> accelerated systems) then it may not be conserved. It also sheds light > >> on one of the great issues of GR - you cant in general define energy in > >> it. It sheds light on it but issues still remain (you basically cant > >> define it completely and unambiguously in a way all physicists will accept):http://scope.joemirando.net/faqs/Relativity/GR/energy_gr.htmlhttp://a.... > > >> If you want to discuss a genuine problem with energy then its problems > >> in GR is certainly on the table. > > >> E=MC2 and all that sort of stuff follows quite beautifully from this > >> definition - in fact its almost pulled out of thin air from the only > >> reasonable Lagrangian you can cook up for a free particle. It is so > >> beautiful Zwiebach in his book on string theory devotes a whole chapter > >> to it (chapter 5) - and he is not the only one. But energy in GR is > >> still an issue. > > >> Thanks > >> Bill > > > Lagrangians lack physics. They are just 'cooked up' to give the > > resulting equations that were desired in the first place. This math - > > not physics. > > Not true. The Lagrangian formalism follows directly from the axioms of > QM. In that sense it is even more fundamental than the Newtonian > formulation. However it is a well known fact the two are logically > equivalent. See for example Chapter 2 - Zee - Quantum Field Theory in a > Nutshell and Chapter 6 Morin - Introduction to Classical Mechanics. > > Thanks > Bill No, Lagrange's reformulation of Newtonian mechanics was to eliminate dynamics involving time into one that only involved space - hence the concept of potential energy. This only worked classically as Newton only needed to view gravitation as acting instantaneously: in terms, of planetary motion this was more than 'good enough'. It does NOT apply to EM where there are always finite time delays for interactions between point particles (e.g. electrons) which exhibit a finite spatial separation. The whole mathematical apparatus of 'fields' (& therefore relativity) was introduced to bypass this embarrassing point that obsoleted all of CM's single-time math.
From: BURT on 28 Feb 2010 15:08 On Feb 27, 11:59 pm, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > On Feb 28, 7:07 am, BURT <macromi...(a)yahoo.com> wrote: > > > > > > > On Feb 27, 12:21 pm, "Y.Porat" <y.y.po...(a)gmail.com> wrote: > > > > On Feb 27, 3:54 am, glird <gl...(a)aol.com> wrote: > > > > > On Feb 23, 4:48 pm, Occidental wrote: > > > > > >< Discussion in physics refer to energy as if it were as fundamental a part of the universe as space, time and matter. In Newtonian mechanics, energy is a useful mathematical abstraction, but not a directly measurable part of any dynamical system. Presumably this is also true in Relativity, despite mass/energy equivalence. > > > > > Before replying to this message I glanced through the previous nine > > > > replies. As I expected, none of them defined "energy". Having long > > > > ago noticed that unless a key word is defined nobody understands what > > > > other people mean when they use it, I defined it thus: > > > > "Energy" is the ability to do work, an ability that is possessed by > > > > organized portions of matter. > > > > > glird > > > > --------------------- > > > just mass in motion!! > > > no need for big philosophy ! > > > > E = mc^2 > > > that s all the story !! > > > > what is unbelievable is > > > that so few people understand it: > > > > it started with that block of understanding that > > > energy has mass > > > started with the idiotic notion that > > > no mass can reach c > > > but all those dumbo s (mathematicians )that consider themselves > > > physicists - > > > could not think about the possibility > > > that there is an exception to that 'rule' > > > ie > > > the photon CAN move at c !!! > > > actually you could see it based on the > > > **trend** of experimental data > > > ie > > > as mass is smaller and smaller > > > it can reach closer and closer to c !!! > > > what can be simpler than that ??!! > > > > not to mention that > > > hf ie h contains mass !!! > > > not relativistic and not shmelativistc mass just the one kind that > > > exits !!! > > > no need to invent each Sunday and Monday > > > i new kind of mass !!! > > > > ATB > > > Y.Porat > > > ------------ > > > Kinetic energy is mass. Light has no kinetic energy because C is a > > constant. > > > Mitch Raemsch > > -------------------- > 1 > in macrocosm > energy is mass in motion > no sane physicist denies it Gamma for motion-flow of energy. > 2 > there is no principal difference about > energy > if it i s done by constant or variable velocity > iow > constant or not constant velocity is not relevant !! to that issue > Y.P > ----------------------- Hide quoted text - > > - Show quoted text -
From: maxwell on 28 Feb 2010 15:18 On Feb 24, 5:45 pm, Jenny <yuan...(a)gmail.com> wrote: > On Feb 24, 10:27 am, maxwell <s...(a)shaw.ca> wrote: > > > On Feb 23, 7:54 pm, Jenny <yuan...(a)gmail.com> wrote: > > > "Particle" and "wave" are just placeholders to help us picture where > > > forces are and how forces move. > > > "PARTICLES" and "WAVES" are not actual "things" > > > In this way of looking at things, forces are the fundamental elements > > > occupying spacetime. "Particles", "waves" and "energy" are merely > > > convenient illusions. > > Our conceptual views of reality, exchanged between members of the same > > community, are described in natural language (not math - a sub- > > language). As such, we have determined from experience that our > > language scheme should be based on nouns (things) and verbs (actions & > > relationships). > > I think science is about more than "experience" it's about looking > beneath surface appearaces. > > > Thus, the dual bases of physics (another sub- > > language) are fundamental things (e.g. electrons) that exist and > > interactions between these things (defining their properties & effects > > on these things). > > It's quite debatable wherher electrons are "fundamental things" or > even "exist" at all outside of our imaginations. > You seem quite prepared to view 'forces' as more fundamental than electrons. In which case, explain how the EM 'force' is defined (or better yet, measured) if we don't have 'things' like electrons to not only experience EM 'forces' but be the source of such forces. It is this false attempt to introduce 'sourceless' forces that leads to all kinds of philosophical problems & paradoxes in physics. I was not denying the need to "go below the surface" to produce explanations: I am not a positivist. But I would not advise standing in a high-energy electron beam & repeating the mantra "it's only our imagination" as a form of protection. > > > Thus, FORCE is a derived concept (assuming > > continuous interactions between things) and is NOT fundamental. > > My point was though force is a derived concept, it might be more > fundamental than it first appeared. > > The concept of a "soul" is a derived concept, but if souls do exist, > then they might quite reasonably be considered fundamental. > > Chance order of discovery does not dictate relative importance. > I cannot see how a "derived" concept can be logically superior to the things it is derived from & physically needs prior existence. Obviously, I am not following the historical order of discovery. The electron was not 'discovered' until the 1890s but has proved to be fundamental since then: stable, universal & lacking all components and structure - what else would you expect from something 'fundamental'? > ...
From: BURT on 28 Feb 2010 17:17
On Feb 28, 12:18 pm, maxwell <s...(a)shaw.ca> wrote: > On Feb 24, 5:45 pm, Jenny <yuan...(a)gmail.com> wrote: > > > > > On Feb 24, 10:27 am, maxwell <s...(a)shaw.ca> wrote: > > > > On Feb 23, 7:54 pm, Jenny <yuan...(a)gmail.com> wrote: > > > > "Particle" and "wave" are just placeholders to help us picture where > > > > forces are and how forces move. > > > > "PARTICLES" and "WAVES" are not actual "things" > > > > In this way of looking at things, forces are the fundamental elements > > > > occupying spacetime. "Particles", "waves" and "energy" are merely > > > > convenient illusions. > > > Our conceptual views of reality, exchanged between members of the same > > > community, are described in natural language (not math - a sub- > > > language). As such, we have determined from experience that our > > > language scheme should be based on nouns (things) and verbs (actions & > > > relationships). > > > I think science is about more than "experience" it's about looking > > beneath surface appearaces. > > > > Thus, the dual bases of physics (another sub- > > > language) are fundamental things (e.g. electrons) that exist and > > > interactions between these things (defining their properties & effects > > > on these things). > > > It's quite debatable wherher electrons are "fundamental things" or > > even "exist" at all outside of our imaginations. > > You seem quite prepared to view 'forces' as more fundamental than > electrons. In which case, explain how the EM 'force' is defined (or > better yet, measured) if we don't have 'things' like electrons to not > only experience EM 'forces' but be the source of such forces. It is > this false attempt to introduce 'sourceless' forces that leads to all > kinds of philosophical problems & paradoxes in physics. I was not > denying the need to "go below the surface" to produce explanations: I > am not a positivist. But I would not advise standing in a high-energy > electron beam & repeating the mantra "it's only our imagination" as a > form of protection. > > > > Thus, FORCE is a derived concept (assuming > > > continuous interactions between things) and is NOT fundamental. > > > My point was though force is a derived concept, it might be more > > fundamental than it first appeared. > > > The concept of a "soul" is a derived concept, but if souls do exist, > > then they might quite reasonably be considered fundamental. > > > Chance order of discovery does not dictate relative importance. > > I cannot see how a "derived" concept can be logically superior to the > things it is derived from & physically needs prior existence. > Obviously, I am not following the historical order of discovery. The > electron was not 'discovered' until the 1890s but has proved to be > fundamental since then: stable, universal & lacking all components and > structure - what else would you expect from something 'fundamental'? > > > > > ...- Hide quoted text - > > - Show quoted text -- Hide quoted text - > > - Show quoted text - No flow is mass at rest in the space frame. Mitch Raemsch |