Talk:Energy

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Info Box Needs Removal

The info box next to http://en.wikipedia.org/wiki/Energy#Energy_and_the_laws_of_motion needs to be removed. It shows a picture of force being the derivative of momentum. These two quantities are completely different than energy, and referencing a completely different physics concept without explanation is misleading to someone trying to understand energy in classical mechanics.

I would remove it myself, but my lack of editing skills might result in some other part of the article being damaged.

I agree, I was just studying and noticed this error. Specifically I was looking for the difference between work, energy and momentum, this just confused everything! —Preceding unsigned comment added by 142.244.161.13 (talk) 18:31, 7 December 2008 (UTC)

Meteorological phenomenons and moon gravity...

Just a question that arose when reading about meteorological phenomena: what about ocean currents? For your reference:

(...)meteorological phenomena like wind, rain, hail, snow, lightning, tornadoes and hurricanes, are all a result of energy transformations brought about by solar energy on the planet Earth.

I realized that ocean currents are mainly caused by the gravity of the moon, as well as solar heating, and winds. The latter two of them are a result of solar energy, but moon gravity is not solar energy...

Ocean currents are not included in this article about energy, which is not directly the point here, but don't you think that many of those meteorological phenomena listed are caused by solar energy as well as gravity forces from the moon? Or is the moon not an energy source on earth like the sun is? The ocean currents caused by it can generate electricity as is done in the Norwegian fjords...

However, I can't see how this would work mechanically. I mean, the moon pulls on the water masses and causes the water to rise where the earth surface faces the moon, as well as on the opposite side, while the earth surfaces moves underneath the water mass. The resulting water currents would slow down the rotation of the earth, wouldn't they? And then

I found this page helpful about moon gravity: http://howthingswork.virginia.edu/print.php?title=The%20Sea%20and%20Surfing&startdate=0&enddate=99999999&topic=the%20sea%20and%20surfing

I hope this is not too much off-topic :-) --Lindenlion (talk) 08:23, 28 November 2007 (UTC)

I think you're right. Since tides are caused by the gravity of the moon, and, along with them, currents (am i correct so far?), then air "currents" aka wind, would also be caused by the gravity of the moon. Plus there is no citation for this - how do you put a "needs citation" thingy on the article? Also, one more question: does the force of gravity from the moon count as a "transformation of energy" when it acts on things like the tide? Is a force containing of energy? I found that force is mass by acceleration, but I could not find the mathematical definiton of energy, so that leads to another question, which is what is the mathematical definition of energy? BriEnBest (talk) 02:41, 22 January 2008 (UTC)

Page moves

A user has asked at an administrative noticeboard if this page belongs here or at the original location Energy. The content that it currently at the page called Energy should be merged into the page Energy (disambiguation); the final location of that page also needs to be discussed. What opinions do others have about the correct names for these pages? CMummert · talk 13:41, 1 May 2007 (UTC)

I am going to avoid being involved too much here. However, I can say that Energy (disambiguation) does not comply with MoS:DAB. It should be just a bulleted list of various articles on energy, with a short description of each item in the list. Energy complies with MoS:DAB, but it could use some short descriptions for each term. Dr. Submillimeter 14:27, 1 May 2007 (UTC)

I can see that such a big topic might need subpages like Energy (biology), but why can't there be a normal main article about energy instead of making Energy a disambiguation page? Surely energy in biology or geoscience has the same meaning as energy in physics. Can someone explain? Gnixon 15:23, 1 May 2007 (UTC)

I agree, for a time this article was a survey of the concept of Energy across all of the sciences and showed how they are all in fact aspects of the same thing. The new arrangement is decidedly nineteenth century in its fragmentation of a unifying concept. I propose something like this is recreated at the Energy article, they are all in fact aspects of the same thing and need a single article, not a list. Lumos3 18:30, 1 May 2007 (UTC)

Concur. Robert K S 19:38, 1 May 2007 (UTC)

I am in full agreement with the opinions expressed by Dr. Submillimeter. In response to the opinions of Robert K S, I can only say that he is not in tune with the modern technology. Long articles were in fashion when only print media was the mode of communication, with the advent of hyperlinking fragmentation cannot be really an issue, because a reader can judge what s/he may be interested in through the title and a brief peep on the page. All the content need not be together. In my opinion the best solution could be adding a line or two below each link summarizing the content of the article. As regards the opinions of Lumos, I was indeed very comfortable with a brief main article on energy across all sciences, but then there are problems, since energy is identified as a core physics topics all physicists feel that all possible information regarding the application of the concept in physics needs to be accommodated on the page and once that is done the article becomes too long. Obviously there is need for some compromise that is transparent to all the past, present and future editors of this article.Charlie 04:02, 2 May 2007 (UTC)

What if we went back to one normal "Energy" article, but worked on pushing most of the material in long sections like Biology to subpages like "Energy (biology)"? Gnixon 04:37, 2 May 2007 (UTC)

The forked subarticles are so short that one wonders what would distinguish them, keeping them from being merged into the main article. This is true for all save the "(physics)" branch (this article), which retains references to the general concept of energy. This is all the more true given that articles or sections of articles already exist for the energy concept specialized into its fields, e.g. biological thermodynamics for energy (biology) and Potential_energy#Chemical_potential_energy for energy (chemistry). I also note that the new forked articles are lacking proper lead and references sections. Robert K S 11:39, 2 May 2007 (UTC)

It's nice to note that you notice fine nuances like references too. Why don't you put in some effort to replace the references in these articles yourself than simply grudging about others efforts.Charlie 05:59, 3 May 2007 (UTC)

Because I disagree with the spirit and execution of these contentious, unilateral, undiscussed article splits and I refuse to put any effort into these new expansions of your "energy article domain", Charlie--I'm not going to throw good money after bad. Robert K S 06:10, 3 May 2007 (UTC)

That's very interesting indeed! You still find time to visit this page and posting messages (Uncalled for butting in). Indeed very good investment of time! Charlie 08:38, 3 May 2007 (UTC)

I agree with KSRoberts on the above aspects, but I feel once these articles are independent other editors would find it encouraging to work towards improving them, which does not happen while they are part of a very long article, with notifications informing editors to work towards shortening the article. I do believe that some time must be allowed to relapse to allow some serious thinking about Energy article about the questions, "Is energy a topic to be dominated by physicists alone? If no what should be the guidelines for its structure and growth? Evidently your laissez faire policy followed so far is not the most appropriate for a subject like Energy! Regarding the questions raised by CMummert in the beginning of this talk, I am of the opinion that the minimal change we can do is to merge the present Energy article with energy (disambiguation) page.[User:Hallenrm|Charlie]] 17:40, 2 May 2007 (UTC)

I also disagree with this article fragmentation. Energy (chemistry) is completely unnecessary; energy doesn't have a different meaning in chemistry and in physics. --Itub 11:26, 9 May 2007 (UTC)

The argument for the changes

Not many people have commented here, but of those who have, only Charlie (Hallenrm) seems to favor the new arrangement, which has separate pages for energy in physics, chemistry, biology, etc. Others have said there's only one concept of energy being discussed in those fields, that all the pages except Energy (physics) are just stubs, and that there are already pages which address the applications of energy that are relevant to each field (e.g., biological thermodynamics). Charlie has said he hopes pages like Energy (Chemistry) will grow now that they've been created. Gnixon 16:42, 9 May 2007 (UTC)

Charlie, since you seem to be in the minority, maybe you could take some space here to lay out your arguments for the changes in a clear, concise way. So far it looks like people prefer the old way, but maybe there's some point that hasn't been appreciated. Gnixon 16:42, 9 May 2007 (UTC)

Please continue discussion at: Talk:Energy. Thanks. Problem is being solved. --Sadi Carnot 01:06, 12 June 2007 (UTC)

Proposals for the Energy Article

I would like to propose that a section about Energy Problems, is created to discuss issues about Global Warming, oil depletion,etc. we can not go on pretending those issues do not exist.

I have sent the following text, to Hillary Clinton,and would like to know your opinion.

---

Proposal about Public Policies. THEME: Energy.

The world requires, under the leadership of the U.S.A. a reform in energy policies:

The world needs, new Energy policies, based in energies that do not pollute, and do not create increases in the prices of corn or sugar (bio-fuels) for the poor people of the world, considering that bio-fuels do contain Carbon and therefore still generate CO2.

The only energy that does not pollute is Hydrogen (produced by algae), or hydraulic plants (like Hoover Dam), solar, wind, sea waves, geothermic, etc.

Nuclear energy is dangerous,as seen in history.

It is necessary that the rich countries, promote the creation of Alternative Energy Research Institutes, to research and promote solutions.

Mexico, Aguascalientes, Dagoflores --189.166.5.98 (talk) 03:21, 3 April 2008 (UTC)

Energy articles proposal straw poll

OK I understand Sadi Carnot's proposal is something like this. Lumos3 09:18, 12 June 2007 (UTC)

1. Energy is the main article with a note at the head pointing to Energy (disambiguation) and is a general review of energy across all sciences.
2. Energy (physics) is a more detailed expansion (including mathematics) of the physics of Energy
3. Energy (biology ), Energy (chemistry), Energy (earth science), etc. These articles are mostly summaries and do not support separate articles. They become part of the Energy overview.
4. Articles on Specific named forms of energy retain their independent status as articles linked as appropriate from all the above.

Basically yes, except for point (3); we'll have to see that bridge when we cross it. --Sadi Carnot 09:40, 12 June 2007 (UTC)

I suggest that as many editors as possible agree to this by stating so below or give counter proposals. Lumos3 10:12, 12 June 2007 (UTC)

• Support Lumos3 10:12, 12 June 2007 (UTC)
• Support, and as Sadi Carnot says, let's treat the subject of the child subject articles (biology, chemistry, etc.) as a separate issue. Those articles can be merged, deleted, or individually expanded, but that issue is not entirely relevant to what happens at Energy. Robert K S 11:51, 12 June 2007 (UTC)
• Support as per my comment above about point (3). --Sadi Carnot 12:00, 12 June 2007 (UTC)
• Support As per my own comments above. SBHarris 18:36, 12 June 2007 (UTC)
• Opposefor the simple reason that the approach is oversimplistic. Energy in modern times is not a subject of science (physics, chemistry biology etc. etc. )alone. The word is used much more often in the society and has several different connotations. I do not see how Carnot proposes to deal with the technological aspect of energy e.g. embodied energy, or the way energy is used ion the society, more as substances rather than just a concept. If he promises to cover all aspects of energy as listed in the present list, in 32k of words and images, i would grant that he is a genius, but I will wait till he accomkplishes the task successfully, and applies himself to the task seriously rather than just giving warnings that have ni meaning, by the very nature of wikipedia. I would like to see him successfully banning me from wikipedia. I am contributing much more seriously than this two friends Robert And Harris whose only concern is to put me down, while they can hardly write a sensible lineHallenrm 18:26, 12 June 2007 (UTC)
• Support. --Itub 19:14, 12 June 2007 (UTC)
• Support. --Bduke 23:46, 12 June 2007 (UTC)
• Support. There are now links to this page (and this discussion, by association) at both WP:DPL and WP:ARCAID. Dekimasuよ! 00:21, 13 June 2007 (UTC)
• Support Iomesus 05:46, 13 June 2007 (UTC)

Banning

Hallen states:

i would grant that he is a genius, but I will wait till he accomkplishes the task successfully, and applies himself to the task seriously rather than just giving warnings that have ni meaning, by the very nature of wikipedia.

COMMENT: People are banned all the time from article when they are insulting and nonconstructive. And I don't just mean sarcastically naming somebody a genius, as Hallen does, above. In the short time (since May 1) that this article has been in its present form, Hallen has left at least one insulting edit summary in the main article: [1] ("edits by sadi Carnot seem to lead nowhere except grunting in frustration") And not less than 3 insulting comments in the TALK section. [2] (Editors are lazy) [3] (Editors are paranoid) [4] (Two editors can hardly write sensible lines)

Nor is this odd behavior for him. There are a huge number of examples from Hallen's posts of this nature going back for more than a year, for he's insulted dozens of people, some many times. I'm quite capable of going back, collecting them all, and laying them before ArbCom. It surely will get Hallen banned in some way, because that is NOT how Wikipedia works. I hope I don't have to do this, as I don't want to do the work. And Hallen won't like the result if I do have to do it. But I will do it, if this behavior doesn't change. I hereby promise it. SBHarris 20:10, 12 June 2007 (UTC)

• Support --Sadi Carnot 22:15, 12 June 2007 (UTC)
• I suggest that banning is a bit premature and not up to us anyway. At some time we may have to think about a proposal to ArbCom, but I do not think we are there yet. Hallen, please reconsider your overall attitudes. You have been around for a long time, yet seem to have a poor idea of how Wikipedia works. You refuse to work with others to seek consensus and you are rude to people who do not agree with you. From this section, I think you should now realize that the consensus is against you and that everything you have done to this article, you have forced through against the wishes of others who are interested in it, even if, like myself, on the side lines. You should take a break from this and related articles. We should all thank Sadi for forcing this out into the open. --Bduke 23:46, 12 June 2007 (UTC)

This is not the proper place to decide whether to ban a user, that's what Wikipedia:Requests for arbitration and other similar channels are for. --Itub 07:49, 13 June 2007 (UTC)

Suggestions from User:Pjacobi

Energy should be an article about energy in the sciences. A summary mention of industrial energy conversion would be fine too. E.g. da:Energi and es:Energía look OK, de:Energie generally speaking also, but it has grown a bit messy. I assume they all derive from a rather old version of the English article. --Pjacobi 16:42, 12 June 2007 (UTC)

Yes, the Energy (German, w/Google translation) is interesting, especially the table. I hope we are one the same page now. If so, please cast your vote at the straw poll at Talk:Energy. --Sadi Carnot 18:16, 12 June 2007 (UTC)

no, the article on energy should not be limited only to the usage of the term in sciences. That is only one aspect of it. If it is an article on wikioedia, which is not an encyclopedia of science for scientists alone, it shold have much wider scope covering all types of usages of the termHallenrm 18:31, 12 June 2007 (UTC)

That's the purpose of disambiguation pages. No need to pollute the main energy article with completely unrelated meanings of the word. --Itub 19:14, 12 June 2007 (UTC)

Agreed. The principal meaning (i.e., energy in all the sciences) belongs at the principal location, then all additional, less common meanings belong on a disambig. We do this all the time in lots of fields, so I really don't see how this is about Wikipedia unduly favoring science. — Laura Scudder ☎ 23:23, 12 June 2007 (UTC)

This is Wikipedia policy—see here. --Old Moonraker 08:51, 13 June 2007 (UTC)

Yes, of course the principal meaning of "energy" is the science one. That's not to say others don't exist, just that science-based energy is the main use of the word and thus should be the main page, with other uses as the re-direct to disambiguation. The science energy is generally the number #1 definition in dictionaries. Had our lone-opinion editor realized this, we could have saved ourselves a boatload of trouble. What's the vote up to, now? SBHarris 13:06, 13 June 2007 (UTC)

Working sub-page

There seems to be momentum in the consensus (8-to-1); hence, for the moment, I’ll start a working subpage here: Talk:Energy/Energy (template). Although, it will still take me another week or two to really dig in. In any event, I welcome contributions on the working sub-page. As soon as I get a free day, I’ll pull the whole thing together nicely. Thanks for all the comments thus far. --Sadi Carnot 01:00, 13 June 2007 (UTC)

I disagree with the need for a subpage: this will only increase the mess. I have reverted the original move, which was in blatant breach of style guidelines (and common sense). "Die Energie der Welt ist constant, die Entropie (diesem Teil) der Welt strebt einer Maximum zu..." Physchim62 (talk) 14:43, 13 June 2007 (UTC)

Can't be created or destroyed

The first paragraph says energy 'is not an object or a substance, but it is quantifiable in a way such that it cannot be created or destroyed.', but energy can be created as in nuclear energy.--Jcvamp 02:51, 13 June 2007 (UTC)

Not sure that qualifies as a "creation" of energy, but anyway, this lead has all manner of problems. The "not an object or a substance" non-definition is superfluous and unhelpful, and the "quantifiable in a way such that it cannot be created or destroyed" is non sequitur, as quantifiabiliy as a property is independent of conservation. Please feel free to fix it up if you can. I offered some suggestions in an archived talk. Robert K S 03:31, 13 June 2007 (UTC)

Okay, I've tried to fix this so it's not completely wrong (defining energy early in its full relativistic energy sense). It's surprisingly difficult, inasmuch as the observer problem arises immediately. No getting around it. But even in Newtonian mechanics, a baseball which flies by you in space, has a different energy than if you chase after it and observe its energy in its own "rest frame", in which it isn't moving. Energy is not conserved between observers, and they don't even agree on how to quantitate it. All they can agree on, is that for any inertial observer, energy in systems doesn't change, so long as you don't let anything in or out. And that energy is connected to the system's gravitational field, which is sort of the universe's way of letting everything else know that there's "something" there. SBHarris 05:02, 13 June 2007 (UTC)

The article on nuclear energy says that matter is converted to energy, and as our only frame of reference for creation is of things being changed from one form to another (eg. when you make a table, you don't create it out of thin air), I assume that would constitute creation.

In regards to the intro, it's kind of heavy reading and in order to understand it, you'd need to know quite a bit about the subject in the first place.

I'm, by no means, an expert, but I got the impression that energy was, in layman's terms, the capacity to do work.--Jcvamp 05:40, 13 June 2007 (UTC)

I agree that the intro is heavy reading. It needs er, work. But the problem is that energy is sort of like the magnetic field-- it's a primary thing and it's hard to define it in terms of other stuff that we're all familiar with.

I've not really sure what article on nuclear energy you're talking about-- if it's the one I've linked in this line, then it really says mass is converted to energy. But that's not really true. As has been argued here long and hard, in a chemical or nuclear reaction, the mass does not change until you let some of it out of the system (non-closed system). So there is no "conversion," just a release, like soda out of a soda bottle. What does happen is that one kind of energy is converted to another--- in both chem and nuclear reactions, potential energy locked up in fields is converted to "heat", which means (among other things) into kinetic energy of particles, and electromagnetic energy (various kinds of "light"). But when a chem reaction happens or even a nuclear bomb goes off, if the system is closed (hard to do with a nuke) the total energy doesn't change, either.

Is energy the capacity to do work? No, not when the energy is in the form of heat, in which case some of it is unavailable. So that definition is tempting, but wrong. Also, conservation of baryon number (which holds for most circumstances, though maybe not in in the Big Bang or in black hole evaporation) means that the energy a lot of the ordinary matter we're used to, which is made of protons and neutrons, it not available to do work. It just sits there, and you can't get it out. But we know it's in there, because if you have antiprotons or antineutrons, you can turn it into work. You just can't get antiprotons or antineutrons without making them, and that takes...... more work. So it's a good demo, but it means in practice that the energy is unavailable except as a demo. See the point? Anyway, this is not an easy topic, for the reason we're now discussing. All the easy and fascile ways to discuss energy are technically wrong. The ways which at least are not wrong, start out almost immediately as being somewhat technical (inertial observer? What's that?). But you have to know what an inertial observer is, even to define the kinetic energy of a baseball. So it's important even for simple problems. Where is the kinetic energy of a moving bullet "stored"? Answer: nowhere. It's a system property. It's like going into the brain and asking where is the personality-- point to it. Or going to Washington, DC and asking to see the "government". Where is the government LOCATED? Well, that's hard to say. That's not to say it has no reality. SBHarris 06:08, 13 June 2007 (UTC)

That's why all sensible extraterrestrials say "take me to your leader" rather than "I want to see the government". :) --Itub 15:09, 13 June 2007 (UTC)

LOL. Of course. Very practical, these aliens. SBHarris 01:22, 14 June 2007 (UTC)

Sorry for not knowing too much on the subject, but I'm interested and I'd like to understand. So, you're basically saying that the energy is stored in the particles? Does that mean that, for example, in a fire, the thermal and light energy are being released from the particles of the fuel.

In modern thought both passive and active energy count the same and produce gravity. What we call "active" is light and motion (basically, heat) and passive is massive particles and static fields, like gravitational and nuclear fields. SBHarris 01:22, 14 June 2007 (UTC)

Also, if the energy is stored in the particles, what is it doing in the mean time? If it's inactive, does that put it on the same level as stuff like 'potential gravitational energy'? (oops forgot to sign)--Jcvamp 00:58, 14 June 2007 (UTC)

Energy is stored in the system in various ways. In fields, the fields themselves have mass and produce pressures which affect gravity. For motion, the energy is stored in the kinetic relationships of objects betweent themselves and the observer, and doesn't really have a good location in space. It's always there, but it moves around, according to whose's looking. Energy in passive objects and fields (made of "virtual particles") which produce forces (therefore also potentials) is roughly located where the particles and fields are. Although again the quantitative energies locked up in these depend on the observer. Different observers disagree as to how much there is, but each agrees that whatever the amount, it doesn't change, unless energy is "let out" or "let in" to the system. SBHarris 01:22, 14 June 2007 (UTC)

I follow you in fields being virtual particles but what do you mean when you say "the fields themselves have mass and produce pressures which affect gravity"? How does pressure affect gravity? JKBlock 19:15, 17 June 2007 (UTC)

According to general relativity, pressure, like energy, causes gravitational attraction. JRSpriggs 06:39, 18 June 2007 (UTC)

Remember that work is pressure*volume. Thus, pressure is energy/volume. In differential forms of the formulation of general relativity, the pressure acts as an energy/volume or volumetric energy density, at every point in space, to generate space-time curvature there. See stress-energy tensor also known as the energy-momentum tensor, for the various components of energy, momentum, and energy and momentum fluxes though any given point in space, which generate the differential curvature of space-time, at that point. If you want the energy in a given volume, you have to integrate all of this over a volume. If there are no energy or momentum flows, then that volume integral just ends up being the total rho*dV integral of the density which gives a rest mass, plus an integral of -PdV which integrates up all the PV work which the system did to put the mass in place, over that volume. SBHarris 08:45, 18 June 2007 (UTC)

I didn't think about the relation to energy, but now I see it. Thank you JKBlock 09:43, 18 June 2007 (UTC)

I'm only fifteen years old, but we just learned about energy at school, I thought the sun created energy by fusion, or does the sun get the energy it sends to the earth from somewhere else? —Preceding unsigned comment added by 84.48.17.134 (talk) 18:10, 26 September 2007 (UTC)

Yeah, the sun gets its energy from fusion, but it doesn't create it, it converts it from stored nuclear energy which it gets from four hydrogen nuclei (technically protons) when they join to make a helium nucleus. --Slartibartfast (1992) 20:07, 26 September 2007 (UTC)

Page history

The history of the Energy pseudo-disambiguation page was lost in the (correct, I believe) move of Energy (physics) to the plain title. However, the contents of that page were needed for a merge into Energy (disambiguation), and since it will be part of a merge, it will be necessary to keep the page history under the GFDL. I'll be working for the next little while to sort out and restore the histories, and for a little bit it will appear that I'm undoing the move. The contents of the physics page will be back here again soon, so don't worry about it. I'm going to move the history of the old pseudo-disambiguation page to Energy (Disambiguation) (sic) and adding a mergeto tag to funnel the necessary contents to Energy (disambiguation). Please help out by merging entries and finally redirecting the page if you have the time. Dekimasuよ! 23:45, 13 June 2007 (UTC)

Finished cleanup. Just need a merge to Energy (disambiguation) now. Dekimasuよ! 23:58, 13 June 2007 (UTC)

It is a very shabby job done by Dekimatsu in the name of cleanup. Let him brush up his basics in energy before he attempts such jobs. Secondly I do not see thyat he has moved the contents of the Olsd History of Energy to this page Hallenrm 03:53, 14 June 2007 (UTC)

Dekimatsu has done an admirable job in helping to clean up the mess which Hallenrm caused in the first place. The former history of this page can now be found at Energy (Disambiguation), where it can stay without causing any problems to anybody. Energy (Disambiguation) will eventually become a redirect to Energy (disambiguation). As for brushing up on the basics of energy, I would suggest that Hallenrm do exactly that, just as soon as he or she finishes the crash course in basic politeness which is so obviously necessary. Physchim62 (talk) 17:15, 14 June 2007 (UTC)

I am a new editor on wikipedia, I stumbled on this page because of my interest in energy. I did a bit of preliminary research before making any comment. On the basis of my readings I really cannot not concor with Physchim62, especially after I visted his talk page. He really cannot insult Hallenrm, because his personal record of politeness on wikipedia can hardly be called cleanArjun2007 18:41, 15 June 2007 (UTC)

Try doing the same research on Hallen's comments. He's an equal-opportunity insulter,and has insulted Sadi Carnot, Robert KS, and various others. I believe he's left a fresh one just today. SBHarris 10:32, 18 June 2007 (UTC)

Where is Sadi Carnot

I see that there has been a serious attempt by SBHarris ans KSRoberts to undo all my edits on this page. I saw some merit in the way Sadi wanted to acheive a reformatting, but it appaears Roberts and Harris can't just wait to acheive their sole ambition in lifeHallenrm 04:08, 14 June 2007 (UTC)

Which is to a decent energy article that is built from a consensus? Please stop your personal attacks. --Itub 05:06, 14 June 2007 (UTC)

Did somebody say sole ambition? Robert K S 20:28, 14 June 2007 (UTC)

Yep, pretty funny. Hallen has 1/6th of my total edits on Wikipedia, on about the same fraction of the 1000 pages I've worked on (1/6th). Yet his edits on energy are 2.5 times mine. Hey, Hallen, Kate's Tool doesn't lie about how people spend their time on Wikipedia. It would therefore be a VERY bad idea for you to go around accusing anybody else of monomania, given your own edit statistics, which are here for all to see.[5]SBHarris 22:06, 14 June 2007 (UTC)

In this respect I would only like to quote from the Wikipedia:Edit_count. It says "Some users partially base their Request for adminship votes on the edit counts of the candidates. Reasons for this may include protection against sock puppetry, and the fact that active admins are needed to help with admin backlogs.

As edits can vary greatly in size and quality, it is important not to put too much weight into someone's edit count, and to avoid worrying too much about one's own edit count. Edit counts do not necessarily reflect the value of a user's contributions to the Wikipedia project. As the saying goes, "Quality, not quantity". Hallenrm 07:46, 17 June 2007 (UTC)

You missed the point. You referred to my effort on this article above as my "sole ambition in life". But the record shows that my edits to this article amount to 2.4% of my total Wikipedia activity. On the other hand, edits to this article amount to 35% of YOUR total edits. So who's closer to having edits on energy as their "sole ambition"? You're the one who spends a third of his Wikipedia time here, not me. I can't find another Wikipedia editor of this article who spends a larger fraction of their time here. You're the champ.

Furthermore, eight editors here disagree with your handing of this page (nine if you count Laura Scudder, who has made her opinion plain) and you can't get a single vote to support your point of view. Thus, it appears that in spite of the time you put in, the "quality" of your approach isn't apparent to any of the other people working here-- It's not just Robert and me who don't like what you did here. None of us do. SBHarris 07:51, 18 June 2007 (UTC)

Okay, the point's made. Let's remember, this talk page is for discussion about the article, and not about Wikipedians. I hope we can let this be and get back to improving the article. Much love, Robert K S 08:51, 18 June 2007 (UTC)

I’m sorry I’ve been away (still kind of tied up); in the mean time, however, I have been letting my sockpuppets Itub and Physchim62 do my biddings for me (that is, at least according to the Hallenrm Conspiracy Theory). Talk later: --Sadi Carnot 05:13, 30 June 2007 (UTC)

New changes to lead

Two quick things--(1) Was it not helpful to give the word's etymology right up front? Is there any reason it shouldn't be restored? (2) Is it helpful to include the qualifier "characteristic of the universe" in the definition of energy? Is there any non-theoretical-mathematical topic on Wikipedia that isn't "of the universe"? Does it impart useful information? Is there any reason "characteristic of the universe" shouldn't be deleted? Robert K S 19:32, 14 June 2007 (UTC)

I'd say it's pretty standard to present such an etymology within the first paragraph. I really can't tell what "characteristic of the universe" is even really supposed to mean here. Unless it is characteristic of the universe as opposed to some other place, it seems like a convoluted way of saying "exists". — Laura Scudder ☎ 22:20, 14 June 2007 (UTC)

I zapped the etymology partly because I was looking for a better one (athough thats no reason why the current one shouldn't stay, at least for the moment) and partly because I thought it would be better in the "History" section. "characteristic of the universe" was meant to be a reference to the conservation of energy at the scale of the universe, but if people don't understand it then it should definitely go. Physchim62 (talk) 14:46, 15 June 2007 (UTC)

Energy (chemistry) nominated for deletion

See Wikipedia:Articles for deletion/Energy (chemistry). --Itub 07:49, 20 June 2007 (UTC)

(I also nominated Energy (biology), Energy (cosmology), and Energy (earth science). --Itub 08:18, 20 June 2007 (UTC))

If their existence is an unbearable affront to your pride (since your permission was not obtained before creating them), you should propose that they be merged into this article rather than deleting them and destroying all that work. JRSpriggs 10:48, 20 June 2007 (UTC)

Energy, a measurable quantity with definite properties?

The sentence: "Yet, energy is not simply a mathematical concept or a philosophical principle: it is a measurable quantity with definite properties." contradicts with Richard Feynman's statement few paragraphs below: "...That is a most abstract idea, because it is a mathematical principle; ... It is not a description of a mechanism, or anything concrete; it is just a strange fact..." What is the property of energy anyway? Also, what's the conclusion to this statement: "It was argued for some years whether energy was a substance (the caloric) or merely a physical quantity, such as momentum." So, is energy a substance or a physical quantity?

It's nothing. Energy is just energy. Defined by "the ability to produce work". Undefinable by anything else. Slartibartfast1992 15:47, 22 June 2007 (UTC)

As has already been discussed, energy cannot be strictly defined as the ability to do work. Robert K S 18:01, 22 June 2007 (UTC)

Electromagnetic Energy

I really think that the section reading "electrical energy" should read "electromagnetic energy". Why? It includes magnetism and electromagnetic radiation inside it. We should just place the whole main part of the section "Electrical Energy", ehich is devoted to electricity, inside "electromagnetic energy", which would have subsections of "electrical energy", "magnetism", and "electromagnetic radiation" after an introuction listing the three subdivisions of this type of energy. Leaving it like this makes it look as though electricity is the phenomenon causing light and magetism, while, in fact, they are all just forms of Electromagnetic Energy. I really want some consensus before I make this change, so please state your opinions. Slartibartfast1992 15:44, 22 June 2007 (UTC)

Wow, I can't believe how many opinions I'm getting... Did somebody establish censorship? Slartibartfast1992 03:50, 14 July 2007 (UTC)

Definition of energy

Is not the work one system can do on another, for only a fraction of heat energy in a system can be used to perform work in another, yet 100% of heat is energy. Thus, some heat energy does not fit this definition. Hence the definition is incorrect. Hence, Robert and I and multiple others have deleted it. Find another one. SBHarris 21:13, 22 June 2007 (UTC)

You confuse heat and thermal energy. Heat is transfer of thermal energy. Everything is correct with textbook definition of energy as a work. Some textbooks define it as ability to do work, which is not very accurate (because "ability" does not have units, while work does).

You not a physicist, but a PHYSICIAN, right? These are two very DIFFERENT professions, right? Why do you then edit articles about physics? And even delete what you don't know? How ethical is that? Does this mean that I should edit your medical articles too (and just delete what I don't understand there)?

Sincerely, Enormousdude 21:02, 23 June 2007 (UTC)

This may be a matter of correct use of the English language, of which I am a native speaker. For your information, in English, "heat" and "thermal energy" are completely equivalent. There is no need for any idea of "transfer" to define "heat" in English. Would you like it if I went to articles in Russian and started editing them (and just delete what I don't understand there)? SBHarris 21:21, 23 June 2007 (UTC)

I am not talking about spelling or grammatic errors. You do plenty of them too as I have noticed browsing via your "corrections" list - despite that you claim that you are native (may be you are indeed - I do not claim that you are not). Of course, if you speak Russian you not only can edit Russian articles, but are more than welcome to contribute into Russian Wikipedia or other Russian publishing activities. And of course, if you know English much better that me you are welcome to correct my spelling, grammar or punctuation. But I am NOT talking about grammar, spelling or even semantics. I am talking about situation when non-specialist does job outside of his field. Say, in Russia we have a saying which can be translated as "It is a disaster if a cake maker tries to make shoes and a shoe maker tries to make a cake". I am talking about physics CONTENT of your corrections - it is often incorrect. We don't have to go far. Look what you have done with the "Energy" article. You deleted accepted by physicists (not by "editors" of Wikipedia by the way, but by specialists) definition of energy and replaced it with incoherent nonsense - from which practically no form of energy can be defined or derived (except may be kinetic energy of a single particle in straight motion - which you just simply postulated), a definition from which energy conservation law can not be derived, a definition from which relationship between work and energy can not be established, a definition from which mathematical propertied of energy can not be derived, and on and on. As more and more forms of energy needs to be defined, you then will have to come up with more and more definitions which you just postulate (and these postulates follow from nowhere) - like rotational kinetic energy, potential energies, etc. And all problems keep piling up just because you sweepingly rejected well known definition which I have previously put in the beginning of this article (and I gave accurate citation source to make sure that this is not proprietary definition, but accepted by physicists definition - McGraw Encyclopedia of physics, 1993, p. 384, ISBN # 0070514003).

As I see the problem with the mess you created is likely due to lack of professional education in the subject (physics), or may be lack of ethics. Say, I have some basic knowledge of medicine and biology. But because I did not graduate with the major in medicine or biology, and have no experience working in the fields of medicine, I consider quite unethical to edit medicine or biology articles - simply because someone like you with more education and experience in the subject knows it much better and thus will deliver much more credible information. Also, I can see that when a good article is edited by a non-specialist, the quality of the information he or she places is much lower than the quality of the information he or she deleted. May be that is why Wikipedia is so poor compared to textbooks and encyclopedias - just because some editors are not specialists in the subject they write about? What do you think?

My English by the way was well accepted by the Department of Defense (for which I was working a few years), by the Department of Energy (with which I had R/D contract and typed many reports as a part of it), by the National Science Foundation (where I worked some time in the panel to judge/distribute NSF awards), by academic journals, and for a teaching and research work in a few universities in the US. So physicists, various administrators, physics students, etc understand me quite well. So does general public, by the way. I have a hobby - investing in real estate, so I frequently deal with sellers, owners, landlords, tenants, banks, agents, brokers, etc. So far nobody said they don't understand what I say or what I expect from them. Well, not exactly so. Some tenants when fall behind in rent seem not always quite understand what I expect from them. But I do not think it is my English - they suddenly don't understand the printed by the Office Max boiler plate contract which they had in their kitchen drawer for 11 months (specifically the dates the rent is due, and the numbers following the $ sign seem to be confusing for them at that moment). Well, math is always a challenge for general public in US. Sheriffs seem to know that very well - they mention only one number: "I don't care what is written there, but you have three days to get out".

Last (but not least). Heat and thermal energy are not equivalent. Let me explain you the difference between them. Thermal energy is usually defined as the part of internal energy of a system which is associated with the motion of microscopic components of the system (in the reference frame of its center of mass). For example, if you have an ideal gas (say, monoatomic for simplicity) then its thermal energy is just total kinetic energy of motion of its atoms. If you have a solid, then its thermal energy is the sum of kinetic and potential energies of vibration of its constituent atoms (let's neglect quantum effects for now - they are not too difficult to account for). Heat is defined as a transfer of thermal energy, or a flow of thermal energy across some boundary. For example, a body at finite temperature in equilibrium with its surrounding being at the same temperature has thermal energy, but because this energy is not going anywhere there is no heat anywhere. Another example - when you gulp cold coke from your mug, do you gain thermal energy? Of course, you do - water molecules in the gulp wibrate with non-zero frequency and amplitude thus having non-zero thermal energy. But do you gain heat? Now we have to define the boundary across which a flow of thermal energy will be calculated, and if this boundary is between cold water in the gulp and the rest of your body then the heat your body gained is negative.

Sincerely, Enormousdude 23:35, 27 June 2007 (UTC)

Sorry, but it's just not that simple, even in thermodynamics, which has a concept called "heat content" (also known as enthalpy, but still symbolized with an H) which would be self-contradictory if heat were forever to be defined ONLY as a flow across a boundary. If you accepted that, once heat flowed into an object, it would no longer be heat once it got inside and stopped flowing, and thus "heat content" would not be a thermodynamic concept, nor any kind of concept. But since it is, you're just going to have to recognize that these definitions are not all universally accepted by all. Heat content or enthalpy, by the way, is pretty close to the effective amount of work you can get out of the internal energy in an object. If energy really WAS the work a system could do on another, the system's ethalpy or heat content would be that energy. But none of those energies (either U or H) include rest energies of the particles the object is made of, or their binding energies, as has been noted. Yet these, too, are forms of energy. So it doesn't work as a definition. SBHarris 01:57, 29 June 2007 (UTC)

Let's try to keep this to a discussion of the article and the concepts defined therein. If need be, please review official policy at WP:OWN. Remember, the objective is to build consensus, not to lay claim to a particular set of topics and exercise power over them as one's "dominion" by dint of having a certain degree or profession. Good ways of building consensus include reasoned discussion and submission of verifiable references. In point of fact, Enormousdude has met the inclusion threshold by providing a source. What elements can be sourced in Sbharris's position? Robert K S 22:26, 23 June 2007 (UTC)

I hate to disagree, but at least in physical chemistry, all the books I've seen do define heat as "transfer of energy", and actually put some emphasis on this point. It has to do with heat not being a state function: not having an exact differential and depending on the trajectory of a process. In its glossary, IUPAC defines heat as "Energy transferred from a hotter to a cooler body due to a temperature gradient" [6]. --Itub 12:27, 24 June 2007 (UTC)

Yes, unlike the case with colloquial English (see your dictionary definition for heat), I will admit that the thermodynamics guys do make a distinction between object total heat content Q (the integral form) and the differential heat dQ which is heat transfered. But then they sometimes define heat dQ as Cdt, which makes heat content an exact differential (since it includes any work that may be done if C is Cp or whatever), although it's still not a state function. The reason for not being a state function is that heat is not conserved, so a hot object could have gotten that way purely by being heated from absolute zero by a certain amount of heat: integral(0,T) Cdt, or else by any combination of heating plus beating on it with a hammer or squeezing it or something in the nature of work. But heat content would and could be a a state function if you merely forbade doing outside work, and it IS the amount of heat you get out of an object if you merely connect it to a reservoir which is at absolute zero. After all, the heat content is basically the thermodynamic energy content U, which certainly is a state function, minus the bond energies at absolute zero, which are the same no matter how the object got made, so are state fuctions also for any given object. And only the binding energy goes into the mc^2 relativistic rest energy, at absolute zero.

You'll note that none of this helps E-dude's proposed definition, since his definitional work is not a state function either (since it too, is not conserved) and the total energy in a object is obviously far more than the work it can do on other systems, unless you have a perfect heat-->work conversion machine, and also have a way to convert all the rest mass of an object at absolute zero, into work, too. You could maybe do that with a black hole, but then you have to get it into the other system as some kind of heat, and then you have the heat->work problem again.

I actually like Physchim62 (talk)'s proposal that we just define the energy of a system as the sum of all other other energies that go into it, that we can think of: rest energy of components, minus their bonding energy, plus the heat (and/or work) necessary to get it up to its temperature T and its volume V at its pressure P, and so on. That all turns out to be something like: enthalpy plus component rest energies minus component binding energies. Unless I've forgotten something. SBHarris 21:03, 24 June 2007 (UTC)

Heat can have many meanings in colloquial English (including "spiciness of a pepper"), but I thought we wanted to be rigorous here. In modern thermodynamics language, there is no such thing as "heat content", and heat is never a state function. The state functions related to heat are the internal energy and the enthalpy, because under some conditions the change in the state function equals the heat transferred. I really see no reason to subtract the bonding energy from the total energy. In thermodynamics, usually one only cares about energy changes, which means that one can set the zero anywhere. The one you propose is as arbitrary as any other. (Sometimes one wants to neglect the energy of chemical bonds, sometimes not. Same for the nuclear binding energy.) --Itub 07:42, 25 June 2007 (UTC)

• [outdent] But thermodynamics has a luxury that we don't have. We really DO care about more than changes in energy only. We'd like a definition of energy, and thus the total energy an object possesses, because that's the way our proposed "definition" purports to define it: the amount of work one system can do on another. Work isn't a statefunction, either, so that's out. I'm looking for other suggestions for energy in a system. The invariant mass/c^2. The gravitational field (in flat space and CM frame) and invariant mass of an object is going to be given by something like the total rest energies of the object's components, minus their binding energies (provided that binding heat has been allowed to escape), PLUS (if the object is at any temperature) something very like U, the internal energy content from our thermo definition. Which in turn is the amount of heat you could get out of the object, if you had to cool it to 0 K, at 0 pressure. Or the enthalpy of the thing if you had to cool it at the constant P of STP. Both U and H should be good enough for you. SBHarris 18:42, 25 June 2007 (UTC)

I really don't see a problem with defining energy as ability to do work. You can add the qualifications later about how heat engines in the real world are not perfect, or say that in the case of thermal energy it can only be transformed into macroscopic work if you have an infinite heat reservoir at absolute zero. Such a reservoir may sound unrealistic, but this is neither the first nor the last definition in physics that is based on an ideal system. For example, the zero of potential energy between interacting particles is commonly defined at infinite separation. OMG! We can never get all the energy out of them either! The Ampere is defined using "two straight parallel conductors of infinite length, of negligible circular cross section, and placed 1 meter apart in vacuum" OMG! That's impossible too! --Itub 17:56, 23 June 2007 (UTC)

I agreed to the definition as applied, provided the qualification about the reservoir or system needing to be at absolute zero, is added. But somebody reverted that. Put it back in, and I'm okay with it.

BTW, it seems to me that there are two kinds of differences between "real" and "theoretical" models. Some involve "infinitely long wires" or "perfectly strong spheres" or "infinitely long-lived astronauts". These gedanken changes tend to be OK because they can be approached as limits in the real world, and in theory all of them could be approached as closely as you like. It's quite a different thing, however, to simply toss out a major law of physics, and a relevant one, like the second law when talking about the first. Which is what we're talking about here. That's sort of like a gedanken in relativity, in which "we assume for the sake of this problem that the speed of light is infinite...." SBHarris 20:31, 23 June 2007 (UTC)

Enormousdude defines "energy' as "a work one system does (or can do) on another system". The issue of heat energy does not bother me so much here. However, I fail to see how Enormousdude is going to persuade protons to convert the energy of their rest-mass into work, given that baryon number is conserved. JRSpriggs 08:39, 24 June 2007 (UTC)

What you actually fail to see is that it has been done on accelerators many times over (and on a daily basis). Take a proton and an antiproton and let them annihilate. You don't even need to accelerate them - being oppositely charged they attract each other and will happily annihilate on their own. After annihilation and decay of intermediate products you will get a bunch of photons and neutrinos with very little (if not none) of rest mass. So, all or almost all rest mass is converted into energy and can then be converted into work (with finite efficiency which is dictated by thermodynamics (which is basicly statistics of a bunch of fermions and bosons)). So you don't need to persuade a proton - vice versa, it is impossible for you to PREVENT a proton from converting its REST MASS into WORK.

Am I the only "physics major" around to explain others how stuff actually works? Can someone else take care of educating non-specialists who abuse wikipedia by misediting it? (Don't people read textbooks nowadays? I understand that is is a little more hard than playing video games, but video games won't give you knowledge of physics - you've got to read textbooks and to do a lot of problems to understand physics.)

Sincerely, Enormousdude 19:21, 26 June 2007 (UTC)

Now be nice, E-dude. You don't know enough more physics than I do to be that snide. Of course, you've hidden several problems in your palm with the annihiliation trick. As has been pointed out, the first one is that matter apparently greatly out-masses matter in this universe. All the antiprotons created in the Big Bang are already gone NOW (what you see NOW is what we had left AFTER that), so where are you going to get enough to do your anihilation, so you can get your rest-mass work out of those protons?

Even if protons evaporate, they evaporate into positrons and neutrinos, so after the positrons annihiliate with the electrons, you're still stuck with the neutinos, which do have some rest mass (when you say "all, or almost all," you know full well that it's "almost all"). And even when you annihiliate protons with antiprotons, the products are usually pi-mesons, which eventually decay back down to neutrinos and antineutrinos and photons. If there were enough antiparticles to let the leptons anihilate, you'd still get a universe full of photons and neutrinos. Thus, still one where you have neutrino rest mass that you can't get at. Can't convert your mu-neutrinos into e-neutrinos without neutrino oscillation, and you can't have that without neutrino rest mass. Can't have this both ways. Can't turn that last rest mass into work.

Of course you will have read Dyson's cosmology about what happens eventually, in that kind of universe (we're ignoring dark energy for now). Even black holes don't actually let you turn neutrinos into useful work. When a black hole evaporates, it evaporates into "heat" (a mix of paricles with higher entropy, by a small factor like 4/3rds, than the black hole of the same mass had-- see Beckenstein for details). First out comes gravity waves, then black body photons, then the first neutrinos, then (as it gets hotter) finally leptons and then hadrons and finally a flash where you get whole atoms and finally even old TV sets emitted. But that energy expands, dissipates, all the hadrons decay, and finally you're back down to photons and neutrinos at constant "temperature." Same energy, no way for life to get any useful work out of it, even if it did get a bit out of that last flash (and maybe watched a little TV).

As temperature falls and the universe expands, life will be faced with lower and lower black body radiation, and fewer and fewer pockets of space to dump it into, after making black holes for local fires. So life will have to slow down and slow down even more, in metabolism, to keep up the thinking processes. Add dark energy and the future isn't even that nice: the universe expands ever faster as it gets bigger. Finally you only have one last black hole for company. When it's gone, every neutrino sees the horizon expand, until all the photons are gone, and all other particles are outside its light-cone. So finally, each neutrino is all alone in the dark, without even a single photon for company.

What are you going to name that lone neutrino in your rest frame, E-dude? If it won't do any work for you, are you going to send it a pink slip? SBHarris 09:38, 27 June 2007 (UTC)

Not only with neutrinoes, but in many other processes we have a change of rest mass. Sometimes to zero (electron -antielectron annihilation, for instance), sometimes to non-zero mass of reaction products (say, decay of neutron into proton electron and antineutrion; or fusion of 4 protons into alpha-particle, etc). And EVERY time change in mass corresponds to EQUIVALENT change in energy (to be exactly mc^2). That exactly is my point. Reactions involving neutrionos are not exeption - vice versa, they just add more prove to mass-energy equivalence. Enormousdude 20:20, 5 July 2007 (UTC)

Gunna drop em down black holes, whence, after evaporation, baryon number is obviously NOT conserved. Black holes are odd. If Hawking is right, lepton number isn't conserved, either, in the final theory. You can get a black hole started, and then feed it with nothing but (say) antineutrinos. But that black hole looks just like one fed with neutrinos only, and decays to the same products. So not only don't black holes have hair, but also no flavor. They suck so much, it's all gone. SBHarris 17:09, 24 June 2007 (UTC)

I'm not sure why we have to be obsessed with black holes in this article. They're neither the most common nor the most important possible flaws in the conservation of energy: that doen't stop energy being locally conserved in any case which our readers would be interested in if they were looking at an article entitled "Energy" (rather than "Black hole" or "Toroidal space-time"). As for the definition, make it recursive. That works for prime numbers. "Energy includes kinetic energy, various forms of potential energy and anything which can be converted into any of these" will do for a first attempt. Physchim62 (talk) 18:04, 24 June 2007 (UTC)

If we were free to pick our own definition (rather than finding one in a reference), I would go back to the history of energy for guidance. If I understand it correctly, energy was first recognized as a non-directional quantitative attribute of motion (i.e. classical kinetic energy) which tends to remain the same. From there it was expanded to include more and more forms of energy which were needed to maintain the conservation of energy. So I would define energy as the conserved quantity which includes classical kinetic energy ${\frac {mv^{2}}{2}}$. Right? JRSpriggs 06:17, 25 June 2007 (UTC)

Let's accept this definition ("non-directional quantitative attribute of motion") for a moment. What units does this definition give? What recepie to calculate, say, kinetic energy does it give? How to find potential energy (say, gravitational or electric potential energy) from this "definition"? Rest mass energy?Enormousdude 19:43, 26 June 2007 (UTC)

Right. So I've taken a shot at it, and defined it as the quantity which is associated with a system's rest mass (invariant mass) PLUS any overall kinetic energy which results from any observer seeing the center of mass of the system NOT at rest (i.e., system total energy or relativistic energy, or whatever you want to call it). That pretty much gets them all, does it not? Rest mass counts up all kinds of energy in a resting system, and the only way you can increase the system energy while it's closed, is to fly by it faster, so it's not at rest (system kinetic energy). SBHarris 19:42, 25 June 2007 (UTC)

Let's assume this "definition" for a moment (energy ="the quantity which is associated with a system's rest mass (invariant mass) PLUS any overall kinetic energy which results from any observer seeing the center of mass of the system NOT at rest"). Same questions to you as to JRSprings above. 1. How do you derive UNITS of energy from your proprietory "definition"? 2. How do you DERIVE rest mass energy? 3. How do you DERIVE kinetic energy? 4. How do you derive POTENTIAL energies of various kinds? 5. Where is in your definition ROTATIONAL kinetic energy (when center of mass IS at rest)?Enormousdude 19:43, 26 June 2007 (UTC)

• I don't claim my definition of mass/energy is proprietary. It's more or less suggested by Taylor and Wheeler in their SR text. Rest mass is a good index of all the kinds of rest energies that exist in a system: that's how nature keeps track of rest energy. Absent odd GR effects with very high gravitational fields or waves, all that's left is the kinetic energy you gain from having such a system move in linear translation, and that's just kinetic energy of the system center of mass, 1/2 M v² (or (γ-1)*M, if you prefer for relativistic linear speeds).

  1. How do I derive units of energy? As (total mass)/c^2. See Einstein or SR article for derivation of E = mc^2.

You can not do that because mc^2 is derived using work to accelerate a mass from one speed to another (or as Einstein did out of conservation of energy seen in different reference frames - which is basicly the same). So, you have to justify that mc^2 is energy WITHOUT reference to work (or to work-energy theorem, or to work-kinetic energy theorem , etc).

2. How do I derive rest mass energy? Otherwise known as rest energy? Rest energy and rest mass are primary quantities in many cases, and thus, are not derivable. You can no more DERIVE the rest energy of an electron than you can its charge (at least at our present state of knowledge in physics): both quantities must be measured.

Rest MASS is fundamental property, but not rest ENERGY. Just calculate a work needed to accelerate given mass (of electron) to relativistic velocities using Lorentz transformations, - and you find that it consists of two non-vanishing at zero velocity terms. The term mc^2 appears to be the energy of any non-zero mass at rest. And it was experimentally verified many times that whenever mass of a system changes, equivalent amount of energy is released or absorbed.

(How to measure? Put something in orbit around it and measure the period. Look up equations relating one to the other).

Like what? What to put in orbit around electron and how to measure the period? And then how to derive from what have been measured the mass of the electron?

And as long as you're going measure rest mass for elementary particles, you might as well do it for systems composed of them, too. What, after all, is your counter-proposal: that we measure whatever rest energies (masses) we're forced to, and calculate the rest, using some force-distance integral?? LOL!

It seems that you are not familiar well with the way physicists work. Once we figured out mathematically the work needed to accelerate given mass to relativistic velocities and found mc^2 term in this work which indicates that even resting mass has energy, we can experimentally test this result. Those tests have been done many times over - with pions, with annihilating electrons, annihilating protons, in nuclear reactions, in various transformations of fundamental particles on accelerators, etc - indeed every times change in mass corresponded to equivalent change in energy. It has been done so many times over and over that nobody in physics doubts the existence of rest mass energy anymore for half century or so.

Well, then, how do you define FORCE? Without using mass or energy in your definition?

No, to define a force you have to use mass: F =dp/dt=d(mv)/dt. Because mass (but not rest mass energy) is still considered a fundamental property, then there is no contradiction here.

Ah, now you want momentum to be a primary quantity?

Momentum (as well as energy) is not a fundamental, but derived quantity: p=mv=m(dr/dt).

Well, if you can have momentum, why can I not have mass/energy as my primary quantity?

Of course, you can. You can have any definition of anything (say, of energy, momentum, force, mass, etc) in any way you want. You are completely free to derive any equation with any combination of any defined by you quantities you want and in any way which pleases you. Nobody argues with that. But this is not the reason to switch from accepted by physicists definitions from textbooks and encyclopedias and use your definitions instead.

You're stuck with it in many cases anyway, so why not just live with it, for all of them?

3. How do I derive kinetic energy? When I need to, system overall kinetic energy is (again) KE = (γ-1) * M where M is system rest mass, and the v in γ is the system center-of-mass velocity.

Hold on, this kinetic energy is the energy which was calculated EXACTLY as I said many times - as a WORK to accelerate a given mass m from zero velocity to some non-zero velocity v. So, we have closed circle now - you have just acknowledged that you could not justify your definition any better than just use the calculated WORK. So, as I said - kinetic energy is the WORK to accelerate given mass.

The internal kinetic energy of the system (that which shows up in its rest mass) is obviously already included in the rest mass M. Just as the kinetic energy of quarks is included in the rest mass of the proton. Why worry about it? All you can do is measure the ensemble total energy of a proton, anyway. (Hint: it is proton's (rest mass)/c^2). Again, how do YOU propose to measure the various rest energies (including internal kinetic energies) that go into making the rest energy of a proton?

4. How do I derive potential energies of various kinds? Same answer. Use of force (as a primary concept) gets you no where.

Can you please elaborate on this. Say, define potential energy of compressed spring. In textbooks it is wery straightforward: U=work against elastic force to compress a spring (or work of elastc force F = -kx taken with minus sighn)=-integral(-kx)dx =kx^2/2. Care to define a potential energy of compressed spring WITHOUT calculating work of elastic force (or work against elastic force - which is the same with minus sign)?

And there are many cases where you can't use forces anyway, because they become infinite.

Why not? Of course, you can. Even infinite force can do finite work. Say, work of the force F~1/x^0.5 is finite from zero x to any finite x despite that the force is infinite at zero.

What are the potential energies which contribute to the rest energy of a proton? You can't derive them-- you can only measure them as part of a whole, by measuring the rest energy.

5. What is my definition of rotational kinetic energy? In Newtonian terms, its the usual 1/2 I * ω².

Hold on here. Care to elaborate, where did you get this equation? The reason being that this equation (similar to K = mv^2/2 equation for translational kinetic energy) is DERIVED as a work of torque to accelerate a rigid solid body of given mass from one angular velocity (say, zero) to another (say,ω). Care to show why your definition should be so suspiciousely work-looking WITHOUT actually calculating work which went to accelerate rotating body?

There's a more complicated SR equation which is hardly ever used because few things have the strength to rotate at relativistic velocities. Same for GR. But in all these cases, the contribution of rotational kinetic energy to the rest mass of a rotating (compound) object, is automatically taken care of, when you measure its total rest energy. No, I have to admit that this term isn't taken care of if you're going to use enthalpy. But it is taken care of, if you use (rest energy)/c^2 and measure rest energy in flat space by simply looking at the period of a (distant) object in orbit about the thing. Again, if your counterproposals involve interactive forces which you can't measure, such as those within the proton, or within a black hole or even too close to an electron (where you'll find the mass departing farther and farther from the nice dressed-mass), I suggest you reconsider. Your program is bound to failure.

On the contrary, forces are very easy to measure - just measure changing with time momentum of a body, and F=dp/dt. On the other hand, your orbiting periods are in fact bound to fail. Explain please how to measure period of anything orbiting electron, or proton, or neutron?

Step well away from the system, take a deep breath, and try something new. Some things in this universe (like mass and energy) are meant to be measured only at a suitable distance. If you get too close, you just get infinities. SBHarris 23:12, 26 June 2007 (UTC)

Scientists do not need new definition when they already have well working old one. If you personally need new definition - nobody objects to that. Create as many definitions and as many equations for each kind of energy as you want. Any passerby does have such right. Just keep your definitions away from textbooks or encyclopedias where existing (accepted by physicists by the way, not by passerbies) definition of energy (via work) is.

Sincerely, Enormousdude 01:37, 4 July 2007 (UTC)

To Enormousdude: You said "... it is impossible for you to PREVENT a proton from converting its REST MASS into WORK.". Obviously, most protons are not converting their rest mass into work. They can do it only when combined with anti-baryons (or in a black-hole which is even less likely around here). So someone might argue that the energy is really all in the anti-baryons, not in the protons at all. If you argue back that the anti-baryons do not have that much energy because it exceeds their rest-energy by a factor of two (or so), you are begging the question of what energy is.

Notice that I did not define energy as a "non-directional quantitative attribute of motion ... which tends to remain the same". I was describing in a general way what was noticed that led to the definition of classical kinetic energy and thence to energy in general. My actual proposed definition was "the conserved quantity which includes classical kinetic energy ${\frac {mv^{2}}{2}}$". I realize that this leaves a great deal as an exercise for the reader. I was not trying to give the kind of axiomatic definition which is used in math and which you (and many others) seek to give here. I do not think that that kind of definition is possible for a concept like energy. My definition is intended just to identify what is most important about energy and which distinguishes it from other concepts. That does not include the ability to deduce all its properties without further experimentation.

Also as Sbharris argues, defining energy in terms of work just pushes the problem back one level. What is work? And why should we care about work anyway? JRSpriggs 07:58, 27 June 2007 (UTC)

I'd much rather have a definition starting from ${\frac {mv^{2}}{2}}$ than trying to cram relativity, cosmology, and particle physics in the first sentence of this article. Let's start from kinetic energy and relate that to potential energy and work before getting into modern physics. --Itub 10:09, 27 June 2007 (UTC)

How do you derive other forms of energy from the definition E = mv^2/2, especially potential energies? Say, gravitational potential energy? Enormousdude 19:01, 29 June 2007 (UTC)

Simple, let the object drop and measure the kinetic energy at the end. ;-) (In an ideal case, of course.) More seriously, once you have kinetic energy you can use it to define work by integrating the force used to accelerate an object and noticing that the result also equals mv^2/2. And once you have work, you can also use it to measure potential energy of springs, gravitational potentials, etc. That's an approach that I've seen in some books. --Itub 11:22, 4 July 2007 (UTC)

I agree that we really shouldn't be trying to define energy in terms of Mass–energy equivalence: putting the cart before the horses will severely reduce the amount of useful work that the system (cart+horses) can perform, however you decide to define work. We shouldn't forget that this is a top-level article in the general hierarchy of energy articles: there's plenty of space elsewhere to discuss the approximations and exceptions. Energy is introduced to French school-kids at about age 13–14 (I know, 'cos I've taught it): why should we be writing the introduction of this article so that only a physics graduate can understand it? Physchim62 (talk) 17:25, 27 June 2007 (UTC)

Work or heat

(added additional header above because this discussion is getting very long) Physchim62 (talk) 13:26, 28 June 2007 (UTC)

We should be writing the Energy intro so that it is generally true and has broad consensus. If that means eliminating some or other textbook definition because it does not apply in all cases, then that's what it takes: Wikipedia guidelines for leads (WP:LEAD) state that significant controversies should be addressed in leads for a long article. Is definition of energy as the ability to do work a real and sourcable controversy? That's the important question that hassn't being addressed in this dicussion yet. Robert K S 23:49, 27 June 2007 (UTC)

There is NO controversy among physicists. Let's open "Encyclopedia of physics", (which was written not by a bunch of passerbies like us but by specialists), 1993, ICBN # 070514003, the article "Energy" at the page 384. The very first sentence reads: "The ability of one system to do work on another system". Clear and concise. Let's open any good physics textbook (which are also written by professional physicists). They all first define WORK (usually as a path integral of force) and then DERIVE various kinds of energy (kinetic, potential, gravitational, vibrational, elastic, electrostatic, magnetostatic, rest mass energy, etc) by directly calculating a concrete WORK of certain force. Later they define more advanced forms of energy (say, thermal energy, heat, electromagnetic energy, chemical energy, energy of radiation, etc) via previously defined forms (like kinetic, potential, vibrational, etc). Many kinds of energy are even still named after the force they were derived from: gravitational, electric, magnetic, elastic. So there is no need to invent a proprietary and very square wheel. It only results in embarrassment of "editors" which have to invent more and more unexplainable and untraceable "definitions" as more and more types of energy must be defined, in contradictions and in eventually in confusion of Wikipedia readers.Enormousdude 21:39, 28 June 2007 (UTC)

No, work is not a state function and mechanical energy on it's own is not locally conserved. This has been known since the early nineteenth century, an can be found in any thermodynamics textbook (whther said text book was written by physicists, chemists or biologists). The word energy came from the Greek ἔργον (ergos), which does roughly mean "work". However the modern concept of energy arose, IMHO, when people realised that caloric wasn't a chemical element but rather something which was equivalent to work; in such a way that the two could be interconverted (within certain limits, generally known as the second law of thermodynamics). Local conservation and the possibility of (limited) interconversion between forms are, for me, quintessential characteristics of energy. I don't think I alone on that one! Physchim62 (talk) 13:26, 28 June 2007 (UTC)

I couldn't find in your response an answer to the question. I'll rephrase. E-dude thinks it's OK to define energy for the purposes of this article as the ability to do work. SBHarris thinks it isn't. E-dude can provide a citation for this defintion, meeting the threshold for inclusion according to WP:V. Can SBHarris's position--that the definition from work is incorrect or controversial--be sourced? Answering this question will help resolve the conflict. Robert K S 14:20, 28 June 2007 (UTC)

As I actually mentioned in my comment, you can find the proof (that the definition from work is unacceptible) in any thermodynamics textbook. The original version is accessible at Gallica here. For those who can't be bothered to follow links, it refers to Clausius' work Memoirs on the Mechanical Theory of Heat, and was published (in various parts) between 1850 and 1865. Citing Clausius is not controversial when talking about energy: contradicting him, on the other hand... Physchim62 (talk) 15:43, 28 June 2007 (UTC)

Okay, but what we really need is some textbook or author who says "Energy can't really be defined in terms of work" or "There is disagreement about whether energy can be defined in terms of work"... (Just playing devil's advocate. But still, it's a valid and important concern! Explicit, and not implicit, sourcing is crucial, because implicit sourcing always carries the onus of being denigrated as original research.) Robert K S 12:10, 29 June 2007 (UTC)

Thinking about thermodynamics IMO just makes the basic definition of energy unnecessarily complicated because you are looking at complex macroscopic systems with a macroscopic definition of work. If you look at a more fundamental level, heat really gets converted 100% into (microscopic) work by increasing the kinetic and potential energy of the particles in the system. I think Feynman's quote (included in the article, and pasted below) sums it up pretty well. --Itub 15:52, 28 June 2007 (UTC)

These notions of potential and kinetic energy depend on a notion of length scale. For example, one can speak of macroscopic potential and kinetic energy, which do not include thermal potential and kinetic energy. Also what is called chemical potential energy (below) is a macroscopic notion, and closer examination shows that it is really the sum of the potential and kinetic energy on the atomic and subatomic scale. Similar remarks apply to nuclear "potential" energy and most other forms of energy. This dependence on length scale is non-problematic if the various length scales are decoupled, as is often the case ... but confusion can arise when different length scales are coupled, for instance when friction converts macroscopic work into microscopic thermal energy.

You'll notice that Feyman does use the word "most." And there's not question that "heat" (if you define it as thermal energy on the move) doesn't get converted 100% into work. The problem is that heat can't always be moved, and some energy (the rest energy of an electron, and most of the hydrogen in the usniverse, for example) isn't ever going to be heat, and isn't ever going to move anywhere. But it's still energy. It sits there and has a gravitational field to show that it is energy, but that's it. Most of its energy is NOT heat, nor even "heat content" (aka enthalpy). SBHarris 01:49, 29 June 2007 (UTC)

I repeat my suggestion that trying to cram general relativity and such in the first sentence of the article is not productive. Every single general physics, even thermodynamics, textbook and encyclopedia I remember starts by defining energy in terms of its relation to work. The complications get added later. Trying to propose a "better", all-encompassing definition of energy that is different from that used in the textbooks and encyclopedia risks violating the no original research policy. Obviously the latter parts of the article can and should discuss the second law of thermodynamics and the energy-mass equivalence, but here we are talking about the lead definition. --Itub 08:22, 29 June 2007 (UTC)

Weren't you the guy who chided me for not using the most modern possible definition of "heat" (one which leaves out "heat content" as a concept), giving me many examples of how definitions in physics have changed during the 20th century. And yet, here you are, wanting a definition of energy in the LEAD, which is pre-1905. Hmmmm. SBHarris 01:04, 30 June 2007 (UTC)

That's a good point, but I still think there is a difference. Any recent textbook and encyclopedia on physics/thermodynamics/physical chemistry will say that heat is a transfer of energy. I don't think it is true that you'll find energy commonly defined in terms of mass and relativity. However, after perusing a few physics books that I had lying around, I've found that sometimes they don't really try to give an all-encompasing definition of "energy"! ;-) (They do define kinetic energy and potential energy, however.) My only concern is that the definition we give should be attributed to an authoritative source. If only IUPAP had the equivalent of IUPAC's "Gold book"... BTW, the latter does have an entry for energy, [7] which actually gives four different definitions (one each for mechanics, thermodynamics, photons, and relativistic physics). Perhaps we could do something like that? --Itub 10:40, 30 June 2007 (UTC)

That would be fine with me, though most of the usable stuff there is in the relativistic definition. Yes, let's let the physicists define energy for us. We can't do anything with the thermo definition because it's not absolute (only involves changes), and the photon definition isn't broad enough. The mechanics definition is okay, except that potential energy is hard to define and measure, except as pain old mass, so again we're back to E=mc^2. Which I'm FINE with, except that if we use it, we're stuck with the mass-wars which took a lot of time in the mass articles (do we define mass as relativistic mass, or as invariant mass?). Either way's okay with me, so long as we are explicit. If we use invariant mass, we have to include an extra term for systems which have system kinetic energy (the system center of mass is in motion). Everything else (kinetic and potential and all kinds of energies) all shows up as total system mass, which is easy enough to measure by simply weighing it, or putting an object in orbit around it, or whatever. The point is that energy always betrays itself as mass, and you can always measure mass easily enough, even if the energies are hard to keep track of. For example, a proton has all kinds of energies of massless gluons, glueballs, whatever-- as well as rest and kinetic energies of quarks and virtual quarks--- we still don't know what all these are. But the total energy is easy enough to define-- it's the invariant mass of the proton * c^2. For moving protons, it's the total relativistic energy of the proton, gamma*mc^2. This can be applied to any system--- they are usually complicated ones where you don't know what all the energies are, and have no way to measure them separately. Enormousdude wants to define energy of a system as the work it can do on other systems. I'm against this for reasons I've stated. But if you change it a bit and define it system energy as the work it takes to CREATE the system, then that's the same as defining it as mass, and I'm fine with it. We know you can make any system from work, but you can't necessarily turn any system INTO work. It's a small quibble, but if it's so small, let's just turn it around and then everybody should be happy. Better yet, include both definitions. SBHarris 00:54, 1 July 2007 (UTC)

I think I'm finally understanding your point of view, although I still don't agree with it. ;-) You seem to have an insatiable need for an "absolute" definition. Me, I have no problem living with relative definitions such as those used in thermodynamics and mechanics (also used in most of physics, and nearly all of the rest of science and technology). As for "you can always measure mass easily enough", I hope that was just a figure of speech! Maybe it's easier to measure the mass of a proton than to measure the components of its energy, but try to measure the kinetic energy of a car using a balance... --Itub 08:12, 2 July 2007 (UTC)

I have always thought of energy as a 'concept that is used to describe change'. I do not see what is wrong with this simple explanation. Just to cite one textbook that uses this definition Lofts, G (2004). Jacaranda Physics 1. ISBN 0 7016 3777 3. {{cite book}}: Unknown parameter |coauthors= ignored (|author= suggested) (help). The change article needs a bit of work though. Thanks, Monkeyblue 10:57, 29 June 2007 (UTC)

The problem with that definition is that "change" is not a well-defined concept in physics physical quantity. --Itub 11:59, 29 June 2007 (UTC)

Nor is the word "concept" very helpful. Robert K S 12:03, 29 June 2007 (UTC)

Thermodynamics can NOT be used to help define (or to doubt the definition of) energy. First, thermodynamics is not a fundamental part of physics, but just a consequence of classic statistics of motion of a large number of identical particles (atoms, molecules, etc). (And classic statistics results from quantum statistics of motion of identical fermions or identical bosons for which wave functions do not overlap, so quantum effects can be safely neglected - but this is not very important for now). Ilatively, classic thermodynamics just uses the definition of energy of classical mechanics. Second, thermal energy is just the sum of kinetic and potential energies of random motion of atoms and molecules (specificly - of translational, rotational and vibrational motions only). All these constituents of thermal energy are defined in classical mechanics via work anyway. Third, the fact that not all energy of random motion but only (T2-T1)/T2 portion can be converted into work (and the rest just still stays in the system as even more randomised motion) follows mathematically from classical mechanical behavior of mechanical energy of ensemble of identical particles (which is first equilibrated with hot reservoir, then with cold and then again with hot). Is it unusual that it is possibly to convert all energy of coherent motion into energy of random motion but not vice versa? I do not see any concern or any contradiction to definition of thermal energy here. Thermal energy is still the energy of translational, rotational and vibrational motion - which all are defined via work anyway. Enormousdude 22:19, 29 June 2007 (UTC)

The thermodynamic problem is only part of the problem. The other is that rest energy is not covered in the work definition. If you want to qualify your LEAD, I'm okay with that. So that you say "in classical mechanics" energy is so and so theoretical maximal work one system can do on another. In special relativity, the concept of energy is extended to include other kinds of rest mass." The last is one sentence, and anybody who wants to ignore it, can. But energy has been known to be more than maximal work content, for more than a century. It's unfair to give the 21st century reader a 19th century definition of energy. Take a look at gravity which redirects to gravitation. Relativity is mentioned in paragraphs 2 and 3 of the article's LEAD. What's wrong with that? SBHarris 01:22, 30 June 2007 (UTC)

Thermodynamics is NOT a problem - it uses classical mechanical definition. And as I said many times over, rest mass energy is NOT exception either - it follows mathematically as a by-product of calculation of relativistic work to accelerate given mass from one speed to another. Why be so mulish in attempts to replace a well known round wheel (=commonly accepted all-around definition of energy) with many square ones (one for kinetic, another for rest mass, yet another for heat, yet another for potential energy, etc)? I also may come up with some proprietary (=non-conventional) definition of energy - say, "energy is what bends space", but so what? It is correct one and covers all forms of energy, but is neither conventional one, nor specific enough to be practical. Enormousdude 17:10, 30 June 2007 (UTC)

You write: And as I said many times over, rest mass energy is NOT exception either - it follows mathematically as a by-product of calculation of relativistic work to accelerate given mass from one speed to another. COMMENT: You can say it as many times as you like, but that does not make it true. The concept of "rest energy" is not a mathematical byproduct of any work questions in relativity. All work and acceleration equations give you is the equation that E_k (kinetic energy) = [γ -1]mc^2---- but that does not identify either of the terms mc^2 or γmc^2, and without those definitions, you're stuck at that point. Now, if you (rather unfairly and unhistorically) go on and add or start with the pre-conceived definition that the term "γmc^2" is the total energy of a body, which is to say, that it is (rest energy + kinetic energy), THEN it's easy to show that the rest energy, when v = 0, is given by mc^2. But at the time, where was no reason to identify γmc^2 with the sum of rest and kinetic energy. Historically, it took Einstein another paper [8] to show that a system or body emitting light with energy L loses mass in the amount of L/c^2 (according to the mass term in its kinetic energy 1/2mv^2-- yes, Einstein actually uses the Newtonian approximation for simplicity), and thus perhaps one might be justified in generalizing the idea that the entire (rest) mass of a body is to be identified with an energy content/c^2. But no work and acceleration arguments are used to generate this conclusion that E(rest) = mc^2 -- rather Einstein looked at equations for the kinetic energy of bodies before and after light emission in differing coordinate systems, as you'll see, if you read the paper. Once rest energy has been identified as mc^2, THEN one can see "rest energy" as the second term in Ek = [γ -1]mc^2, which in turn means that the first term γmc^2 is = (rest energy) + (kinetic energy), which THEN means γmc^2 is finally defined, and seen to be a sort of relativistic total energy. But that conclusion historically comes LAST. Historically it was done in that order: finally coming up with a definition for γmc^2 out of mc^2 and [γ -1]mc^2, NOT by first defining or deriving γmc^2 as a sum of rest and kinetic energy, then working backwards to see what the correct relativistic formula for "rest energy" was, when v = 0.

Yes, I know the last way is the way it's often done in popular explanations, and indeed is the way it's done in the Wikipedia article on the subject also. But don't mistake easy derivation for historical physics. Again, if you think that E = mc^2 for rest energy comes out of a "by-product of calculation of relativistic work to accelerate given mass from one speed to another," you're sadly mistaken, and you must learn some real physcis history, not "nice-story" history. SBHarris 23:23, 30 June 2007 (UTC)

We do NOT discuss here history of physics. We discuss accepted by specialists definition of energy (to be just a work) which is cited in all good textbooks and encyclopedias of physics, versus proposed by you or others (apparently non-specialists) proprietory (and often non-specific) definitions of energy. Rest mass energy mathematically follows from calculation of work to accelerate given mass. In such work the term mc^2 persist to exist even at zero velocity - see for instance any good relativity textbook, or just any good calculus based physics textbook (like Landau, Feynmann, Sevey, Young, Tipler, etc). It was experimentally verified many times over that indeed, when a mass changes by the amount Δm, the exactly EQUIVALENT amount of energy equal to E=Δmc^2 is released (or absorbed). Let me cite "Relativistic energy and work" paragraph from Young & Freedmann "Univerity physics" text (11th edition, 2004, p. 1430). After calculating the amount of work needed to accelerate a mass, authors say that the total energy E seem to consist of the kinetic energy K and the energy mc^2 which body has even when being at rest. Then they say: "There is in fact direct experimental evidence that rest energy really does exist. The simplest example is the decay of a neutral pion... If a neutral pion has no kinetic energy before its decay, the total energy of the radiation after its decay is found to equal exactly mc^2. In many other fundamental particle transformations the sum of the rest masses of the particles changes. In every case is a corresponding energy change, consistent with the assumption of a rest energy mc^2 associated with a rest mass m." I can cite a few more textbooks which basicly say the same.

If to use your "historic derivation" approach then we have to change many articles removing logical (=mathematical) derivations and instead place historically first derivation. For example, instead of deriving energy levels of H atom from Shroedinger equation as all good textbooks do we must state that they come from planetarian Bohr model. Yes, historically Bohr was first to derive accurate energies of H atom which matched measured energies to 4-5 digits accuracy. But his classic planetary model never went beyond H atom - it could not give energies of even He or Li atoms. No credible textbook will insist that H atom energies come from planetary model. Same can be said about many other quantities of formulae which first were either guessed or derived from wrong assumptions and happened accidentally to be correct. Say, Plank's formula of black body radiation was first derived from Plank's assumption that the energy of oscillating atoms emitting radiation in a cavity is quantized with quanta equal to E=hf. It turns out later that this is incorrect, it was energy of e/m radiation itself which was quantized, not the energy of oscillations of radiating atoms.

So historicity can not be used as an argument to change acceped definitions.

Enormousdude 00:13, 4 July 2007 (UTC)

Current lead first sentence for context of this discussion

As the article stands now, the lead reads In physics and other sciences, energy (from the Greek ενεργός, energos, "active, working")[1] is a scalar physical quantity used to describe a conserved property of objects and systems of objects, which is associated with the rest mass of the object or system, as well as any overall velocity which the object or system may have. Energy may come in many different forms... Robert K S 12:06, 29 June 2007 (UTC)

This obviousely is NOT the accepted by us, scientists, definition of energy (the one which I placed many times: "energy is defined as a work..." - and which many editors ignorantly removed). This is just uneducated opinion of someone (apparently - of many "editors") who is not familiar with physics - moreover, of someone who does not even want to look up a textbook. This laughable "definition" does not even give units of energy, nor allows to derive from this "definition" any concrete form of energy (potential, gravitaional, kinetic, rest mass, etc) Enormousdude 19:34, 6 July 2007 (UTC)

ED's definition is consistent with both Brittanica:

in physics, the capacity for doing work.

and Marrion-Webster:

3 : a fundamental entity of nature that is transferred between parts of a system in the production of physical change within the system and usually regarded as the capacity for doing work

The current lead is not wrong, but (a) it's not the usual way to define energy, (b) the phrasing "scalar physical quantity" seems unnecessarily abstract and vague, and (c) there's no need to mention E=mc^2 here. I suspect this discussion could have been resolved long ago if everyone stayed calm and polite and relied on references (and nothing else), as suggested by Robert. Make sure any edits have correct grammar and spelling. Gnixon 22:50, 6 July 2007 (UTC)

Wow, this is a long page, and I do not claim to have read it all.

ANYWAYS... I feel that the article is SEVERELY lacking in a mathematical definition of energy, and...

If SBHarris, et. all. deleted it, I feel (personally), that they shouldn't have done that, because they didn't replace it with a new one. I feel that the article NEEDS a mathematical definition of Energy, if one CAN be obtained (besides the rather esoteric E=mc^2 (IS THAT THE oNLY ONE???) and besides "the potential to do work")). Plus, it seems there was some sort of mass misunderstanding on the part of SBHarris (sorry i like you Mr. Harris, but misunderstandings happen to everyone..) and the quoted "Roberts and multiple others" between "HEAT" and "Thermal Energy."

It *SEEMS* to me that they just misunderstood... and I WOULD LIKE TO KNOW!!!!

WHAT WAS THE "DEFINITION" THAT THEY DELETED????

and i'll just add that... i think it should be put back.

- BriEnBest (talk) 03:06, 22 January 2008 (UTC)

The definition I deleted has been re-added, which is the one that says that energy is the capacity for one system to do work on another. I tried to point out that if you believe in the heat death of the universe, after which no system will have the capacity to do work on ANY other, that means that if you accept this definition of energy, the energy of the universe will go to ZERO over time. I don't think that's what we want to say. The proffered definition re-added is actually the definition of FREE energy, not simple energy (which is what this article is about). But I've not yet been able to convince anybody of this, or make the argument in a way that everybody undertands. So, I've left it alone. I left a note that there's a raging contradiction on this point at the end of the "heat death" paragraph, for those still interested and willing to put their thinking caps on. I'm not a bad guy just for pointing out that some of the standard "definitions" of energy out there don't work, without some giant qualifiers. SBHarris 03:50, 22 January 2008 (UTC)

well, ok - i agree with you. and i'm sorry about my tone before, bro. i guess i don't know what the difference between "free" and "simple" energy are...i still need to finish reading the physics for dummies book i bought. but anyways, if you could explain that, then it would help me. I've been reading about mass - one thing that struck me was that mass can't really be measure without either gravity, or without measuring the change in it's inertia after a certain amout of (i think work) is applied to it. and yet that doesn't mean that mass "wouldn't exist" if there was no gravity or if there was not capacity for work to be done on it - just that it cannot be measured. so i guess it is the same, or similar with energy - energy and matter are indeed very similar, are they not? also, doesn't anyone think the equation, "E=mc^2" should be in the article somewhere? i would like to hear what enormousdude thinks about that... :-\ is he still around? BriEnBest (talk) 07:17, 1 February 2008 (UTC)

Introduction

I have revamped the introduction (diff):

• I have tweaked the definition to reads as a more general idea.
• I have moved the types of energy into a list.
• Moved around/merged/separated paragraphs.
• Removed work from the introduction as this point should be made latter in the article.
• Linked some terms.
• Reworded parts/quite a lot.
• I took this to be a BB edit.

Thanks, Monkeyblue 11:50, 25 June 2007 (UTC)

MB, I moved the types of energy (back) into the prose before I saw your comment here. I think a bulleted list would be more appropriate for the body of the article, where it could be made more complete. Just giving a few in-line examples in the lead should suffice to give people an idea of what the article covers without disrupting its flow. Gnixon 22:55, 6 July 2007 (UTC)

No merge of thermal energy, internal energy, and heat

There seems to have been some kind of edit war brewing over the last weeks at the heat and thermal energy articles between several editors, primarily User:The Way, that caused User: ScienceApologist to quit Wikipedia. In any event, the situation still continues; please review Talk:Heat (disambiguation) and Talk:Heat and give your opinion or vote: here . --Sadi Carnot 04:08, 2 July 2007 (UTC)

Quick Help I need an Expert

Is energy material??? -PatPeter 16:49, 2 July 2007 (UTC)

See the article or ask on WP:VP. Miranda 16:51, 2 July 2007 (UTC)

Thanks I didn't know where to ask. -PatPeter 17:09, 2 July 2007 (UTC)

I was trying to respond to PatPeter's confusion which is undoubtedly shared by many readers. I added "Energy is not a substance; it is a quantitative attribute of matter and radiation. In other words, energy is not a thing, but each thing has such-and-such an amount of energy." to the end of the lead. But I was immediately reverted by Robert K S (talk · contribs) who said "rv unencyclopedicly worded, unsourced "clarification"". In my second sentence, I was trying to use simple language to make sure that the message got across to less educated readers. Is that being unencyclopedic? As for a source, this is common knowledge among people conversant with physics. Why is a source necessary for common knowledge? JRSpriggs 02:32, 3 July 2007 (UTC)

I think "such-and-such" is a little too informal. I'd suggest keeping everything in the lead should be stated as concisely as possible, saving both technical and informal clarifications for later in the article. Gnixon 14:26, 3 July 2007 (UTC)

I also find the sentence in the lead, which says "The different forms are all equivalent (in some cases overlapping)[3] and may be converted into the other forms of energy, transferred to other matter or stored.[4] ", very confusing. If energy "is a scalar physical quantity" How can it be stored. Only a substance or material can be stored, according to my understanding of the colloquial usage of the word stored.Hallenrm 08:41, 3 July 2007 (UTC)

Good point. I simplified the paragraph by just cutting that sentence. The fact that energy can be converted from one form to another is mentioned in the next sentence and can be elaborated upon later in the article. Gnixon 14:26, 3 July 2007 (UTC)

Neither this page nor the Village Pump are the place to ask knowledge questions. This page is only for discussing changes to the article, and the Village Pump is for discussing changes to Wikipedia. If people have questions about the content of the article, the best thing would be to look through the talk page and article history for someone who appears to be knowledgeable, then ask them a question on their user talk page. I've tried answering PP's question on his talk page. Cheers. Gnixon 14:50, 3 July 2007 (UTC)

Yeah this discussion is also going on here on YouTube, because this guy says that if energy is not material it is meta-physical. -PatPeter 19:06, 3 July 2007 (UTC)

Controversy over definition

I'm a little hesitant to add this comment but less hesitant not to. Question: Is this controversy a matter of encyclopedia content or one of physics? If the former, let's just defer to the standard texts and physicists noting important discrepancies where they occur. If the latter (that is if there really is controversy and confusion over the very definition of energy in the physics community), then this in itself is significant and should be included in the entry. I am not convinced there is such a controversy in the physics community; however, all of this lengthy and involved discussion here by many seemingly informed people and the fact that some pretty basic issues (one on transfer, another having to do with work capacity, and still others) remain unresolved has left me in doubt.

Is there really no basic consensus among physicists? If so, then this is just the kind of thing I would expect to learn from a good encyclopedia entry. --Jcblackmon 06:22, 25 July 2007 (UTC)

Some aspects of the definition of energy are unambigous. One is that there is a single minimum amount of adiabatic work requred to transition from any one well defined state of a closed system to any other well defined state of that system. The minimum amount of adiabatic work determines the difference in energy between the first state and the second state. See thermodynamic state.

Different processes that induce different types of changes in state can be compared in terms of energy and all fall on the same energy scale. The minimum amount of adiabatic work require to get from one state to another is always the same no matter which processes are used or which path of intermediate states is followed.

With a fixed frame of reference, rest mass can be used to put energy on an absolute scale. Total energy equals mc2. This means that when the system does work and gives up energy it gets lighter. The mass is indifferent to the form the energy takes or the ways in which the energy is or is not available to do work. The mass does not indicate what forms of energy are present. Different forms of energy are defined ad hoc in relation to identified characteristics of system states and, in a related manner, ways in which systems can be gotten to do work. The interesting part is that as new forces and ways of doing work are found, the forces are invariably related to measureable changes in system states, sometimes requiring new state variables to be defined. The newly characterized states have always fallen into the old energy scale and obeyed the conservation law.Pvkeller (talk) 19:25, 11 November 2008 (UTC)

There is no definition of energy, as Richard Feynman pointed out; no-one knows what it is, at least not in the mainstream science sense. The so-called definitions of energy do not define its nature, they only describe what it is perceived to do. RichardKingCEng (talk) 23:04, 11 November 2008 (UTC)

Not knowing what something is and not having a definition are two very different things. The intro of this article includes several very reasonable definitions. Very few definitions define "natures", in fact I don't imagine anything can have its nature defined as you suggest. In this situation what we don't "know" about energy is ambiguous on the level that a child could follow any answer with successive whys. In this light we don't know what matter, space, time, gravity, magnetism, or any of the other forces "are", yet each is readily measured and manipulated. The belief and desire for teleological meanings is a pursuit of questionable value.--OMCV (talk) 04:06, 12 November 2008 (UTC)

I didn't mean to start a philosophical debate here; my question is now dated. I was responding to the intense debate between editors way back then. The article now addresses my concerns. I like.--Jcblackmon (talk) 18:22, 27 November 2008 (UTC)

External links: revision by Vig vimarsh

I invite other editors to decide for themselves whether any of the links reinserted by Vig vimarsh enhance the article. Cripes, the first one isn't what it claims to be at all, i.e. it is not a discussion among physicsts, rather it's just a general forum discussion and clearly not a reliable source. A poorly chosen or unnecessarily large selection of external links greatly detracts from the value of an article. My consideration for picking links to be removed was based on these guidelines. Tim Shuba 09:13, 25 July 2007 (UTC)

I cleaned some per request. --Sadi Carnot 09:54, 25 July 2007 (UTC)

Thank you, that looks like a big improvement. Obviously, choosing a set of external links that do enhance a broad topic such as this is somewhat subjective, and reasonable editors will disagree about the specifics. Tim Shuba 17:26, 25 July 2007 (UTC)

I think that Tim Shuba should have talked before deleting the links and clearly stated his reasons for doing so rather than just a cryptic WP:ELHallenrm 17:43, 25 July 2007 (UTC)

Oxygen does not balance

You have the following equation in the page

  C6H12O6 + 3O2 → 6CO2 + 6H2O

The amount of oxygen on the two sides do not balance. Shouldnt it be

  C6H12O6 + 6O2 → 6CO2 + 6H2O

Cs1kh —Preceding comment was added at 15:37, 3 December 2007 (UTC)

Energy(history).

At the beginning of the third paragraph of the section History, I can hardly identify who was represented by the pronoun "He".

In the same paragraph: "He amalgamated all of these laws...", the laws involved are not previously listed.

Chiloa (talk) 20:06, 6 December 2007 (UTC)

energyu

[[]]--209.158.139.250 (talk) 19:30, 10 December 2007 (UTC)

latin word for energy?

is there a latin word that is equivalent to energy? if so, what is it? and is there something like "energology," the study of energy? thanks. BriEnBest (talk) 02:25, 22 January 2008 (UTC)

would it be physics? or physikas? (or whatever the latin word is)??? BriEnBest (talk) 06:56, 1 February 2008 (UTC)

This site says "navitas". I have no idea whether that is correct. You could try looking for a Latin-English dictionary, or ask on the Reference desk. Googling for navitas finds some energy-related links so that's probably a good bet. You can also search Wikipedia for: navitas and find some energy-related links. There's even a Navitas Energy company, which sounds redundant. --Teratornis (talk) 07:06, 9 April 2008 (UTC)

Some edits

I see that there's a bit of tendency to see energy as stored in chemical bonds: it isn't. You only get energy stored as rearrangment of bonds from weak to strong. Thus energy in food is not IN the food, but only in the combo of food+oxygen. Similarly, the bonds in ATP don't store energy-- it's stored in the reaction of ATP + water --> AMP plus hydrated PP. ATP breakdown in vacuum would require energy (as the breakage of all chemical bonds does).

I've added a little vingette emphasizing that all energy releases are releases of various potentials stored since the Big Bang. Give me any spontaneous process and in a couple of steps I can show you how that energy was stored as usuable potential, from conditions after the Big Bang. That's the whole point of heat death. I've also added a point from an argument I had here earlier, which is that if you insist on energy being defined as work one system does to another, then heat death demands energy in the universe goes to zero, over time. Say what? We thought energy was conserved! The work one system can do on another is the FREE energy, not the simple energy. SBHarris 03:42, 22 January 2008 (UTC)

Wind power articles organization?

I've posted a long question at Talk:Wind power#Lopsided coverage? asking how best to fit the concepts of "Electricty generation from Wind" and "Wind energy" together. In brief I would like suggestions on which should be the parent and which the sub-articles. I can work with either but have a preference for an organization that matches the way Portal:Energy structures solar and hydro power. Thanks. -Wikianon (talk) 22:25, 27 January 2008 (UTC)

Help please

Can somebody plz send me a list of what energy/electricity can travel along? thanksSylvan wu (talk) 22:45, 11 February 2008 (UTC)

You might want to try asking on the Reference desk. Electric current travels along any conductor, and across electric arcs and corona discharges. Sufficiently high voltages can cause dielectric breakdown. Moving a conductor through a magnetic field causes induced current. Electrical charges can travel on water droplets, see lightning. There is also ball lightning and Saint Elmo's fire. For the more general concept of energy, there are lots of ways to cart it around or beam it: electron beams, electromagnetic radiation, heat pipes, kinetic energy of moving objects or fluids, hydraulic power, compressed air, oil tankers, gas pipelines, any vehicle with a fuel tank or battery, belt drives, sound, etc. --Teratornis (talk) 07:19, 9 April 2008 (UTC)

Can the equivalence of mass and energy to be derived from Special Relativity?

Some people discourage the use of the term 'relativistic mass'. If we use the term 'invariant mass' as the sole definition of mass, we can derive a formula that relates mass, speed and kinetic energy. In order to conserve momentum in special relativity, we discover the definition of momentum which is different from classical mechanics.

${\vec {p}}=\gamma m{\vec {v}}$

$\gamma ={\frac {1}{\sqrt {1-v^{2}/c^{2}}}}$

Where m denotes mass, ${\vec {v}}$ denotes velocity, v denotes speed and c denotes the speed of light in vacuum.

Kinetic energy of a object with mass possesses is equal to the amount of work to be done on it to accelerate it from rest to its current speed.

$\gamma ={\frac {1}{\sqrt {1-v^{2}/c^{2}}}}$

$E=\int {\vec {F}}\cdot d{\vec {s}}$

$\gamma ^{2}c^{2}-\gamma ^{2}v^{2}=c^{2}$

$2\gamma c^{2}-2\gamma v^{2}-2\gamma ^{2}{\vec {v}}\cdot ({\frac {d{\vec {v}}}{d\gamma }})=0$

$\gamma {\vec {v}}\cdot d{\vec {v}}=(c^{2}-v^{2})d\gamma$

${\vec {F}}={\frac {d{\vec {p}}}{dt}}={\frac {d}{dt}}(\gamma m{\vec {v}})=m(\gamma {\frac {d{\vec {v}}}{dt}}+{\vec {v}}{\frac {d\gamma }{dt}})$

$E=m\int (\gamma {\frac {d{\vec {v}}}{dt}}+{\vec {v}}{\frac {d\gamma }{dt}})\cdot d{\vec {s}}=m\int \gamma {\frac {d{\vec {v}}}{dt}}\cdot d{\vec {s}}+m\int {\vec {v}}{\frac {d\gamma }{dt}}\cdot d{\vec {s}}=m\int \gamma {\vec {v}}\cdot d{\vec {v}}+m\int v^{2}d\gamma =m\int c^{2}d\gamma =\gamma mc^{2}+C_{0}$

Where E denotes kinetic energy, m denotes mass, ${\vec {s}}$ denotes displacement ,c denotes the speed of light, ${\vec {v}}$ denotes velocity, v denotes speed and $C_{0}$ denotes a constant to be determined. Since an object has zero kinetic energy when its speed is zero, so we deduce that

$E=\gamma mc^{2}-mc^{2}=(\gamma -1)mc^{2}$

From the above derivations, besides getting the equation of kinetic energy, we cannot conclude that mass is a form of energy or see any hint on it. However, if we use the notion of 'relativistic mass', we can see a suggestion on the equivalence of mass and energy. The reason is as the following. We define momentum is a product of relativistic mass and velocity. (This is actually the original definition of inertial mass, see inertia) As such, we get the relationship between relativistic mass and the rest mass.

$m={\frac {m_{0}}{\sqrt {1-v^{2}/c^{2}}}}$

$E_{k}=(m-m_{0})c^{2}$

$dE_{k}=c^{2}dm$

Where m denotes relativistic mass, $m_{0}$ denotes rest mass, $E_{k}$ denotes kinetic energy and v denotes speed. We can conclude that the change of kinetic energy is equal to the change of relativistic mass, or simply mass. This implies that rest mass may be just a form of energy. We can further analyze if mass is really identical to energy.

As shown above, Special Relativity allows the possibility of the equivalence of the mass and energy. It suggests that way. However, the relationship cannot be derived directly from Special Relativity. It does not give a strict proof on the equivalence of mass and energy. We only see the suggestion when we use 'relativistic mass'.

After getting the relationship between momentum of a photon, its frequency and its energy, the equivalence of mass and energy can be proven. (This relationship is proven by Compton Scattering Experiment and photoelectric effect)

$|{\vec {p}}|={\frac {h}{\lambda }}={\frac {h\nu }{c}}={\frac {E}{c}}=mc$

$E=mc^{2}$

Where E denotes energy, m denotes (relativistic) mass, ${\vec {p}}$ denotes momentum, h denotes plank constant and c denotes the speed of light in vacuum. We consider a thought experiment to see if mass is really equivalent to energy. In COM frame, an object is said to be at rest. It emits two photons in opposite direction with the same magnitude of momentum. As required in conservation of momentum, the object will remain at rest after the emission of two photons in COM frame. If an observer moves in the same direction as one of the photon in COM frame, he will see these photons carry different magnitude of momentum. The magnitude of momentum observed b the observer can be computed by using relativistic Doppler effect. According to the observer, the object does not change its speed after the emission, the only way to reduce momentum is to reduce mass.

In conclusion, the equivalence of mass and energy can be seen as a suggestion of special relativity. We can't really derive it from special relativity directly. We get a very clear hint however. See also mass-energy equivalence Thljcl (talk) 03:49, 20 May 2008 (UTC)

Primary meaning

There has been much debate over whether the 'physical quantity' meaning of the word "energy" is truly the primary meaning; alternatives might be one of the others on Energy (disambiguation) or perhaps there is no primary meaning, simply several relatively equal-weight meanings. This debate is ongoing and is quite heated. It seems to me that this talk page is the correct place for this debate rather than the dab talk page or the various other talk pages onto which it has spilled. If you decide there is no real primary meaning then this page should be moved to Energy (physics), or similar, and Energy used as the disambiguation page. I have no axe to grind here but I would appreciate it if editors familar with the topic could comment here. Thanks. Abtract (talk) 12:06, 27 May 2008 (UTC)

remind only i cannot be so happy energy is transformed to another,the total energy remains the same.... —Preceding unsigned comment added by 125.60.241.190 (talk) 02:05, 27 August 2008 (UTC)

On the source about Poincare

The source at http://www.serve.com/herrmann/einpdf.pdf does not seem peer-reviewed and print-published, but it is well researched and it is not polemic. I quote it in the article for the convenience of not searching the web for other sources. I somebody else finds a better source, he/she may replace that source, or simply add an extra source. Tgeorgescu (talk) 21:41, 9 October 2008 (UTC)

"External links" once again

Some of these relate to power generation, or even tourism in sunny climates, rather than the subject of this article and are to a greater or lesser degree WP:SPAM. I'm suggesting that it's time for another modest clearout. --Old Moonraker (talk) 11:43, 23 January 2009 (UTC)

I agree, the idea of links is to offer the reader more information on the subject. Not to advertise companies loosely related to energy. FFMG (talk) 12:14, 23 January 2009 (UTC)

There was a lot of junk there. I went in and deleted every link that wasn't obviously and clearly relevant and useful. --TS 13:40, 23 January 2009 (UTC)

Thanks. --Old Moonraker (talk) 14:31, 23 January 2009 (UTC)

Why is there a link to the article for "Americans for Balanced Energy Choices"

This article is about energy as a physical phenomenon. Americans for Balanced Energy Choices is an interest group for the coal industry. While it is true that they advocate the conversion of chemical energy into mechanical energy, their organization and mission is completely irrelevant to someone who would like to learn more about what energy is and how it works. Just to be absolutely clear, I am not removing the link because of the substance of their mission, but simply because their mission is irrelevant to the substance of the Energy article. --70.108.40.152 (talk) 19:46, 16 February 2009 (UTC)