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Although terminology like "mass-energy equivalence" and "interconversion of mass and energy" is common, it is nevertheless incorrect.
Mass is an extensive property of matter. It is also an extensive property of energy. If you take a small isolated system containing matter, and weigh it, and if the matter inside the isolated system then gets converted to energy, and you weigh that isolated system again, there will be no change in its weight. If the matter within the isolated system had a mass of N grams, the mass of the resulting energy is also N grams.
So mass cannot be converted into energy. Really, it's matter that can be converted into energy. The mass of the resulting energy is equal to the mass of the matter that we began with.
Even physics researchers sometimes use sloppy language, figuring that everybody understands that it's not mass, but matter, that can be converted into energy. But they misjudge their audience, and the result is confusion everywhere. The result is an entire Wikipedia article that uses confusing language.
Rahul ( talk) 01:08, 2 March 2017 (UTC)
BEGIN CITATION
Energy has Mass: A common misunderstanding is re-examined.
Hermann Bondi and C B Spurgin.
Physics Bulletin, Volume 38, Number 2, 1987.
http://iopscience.iop.org/article/10.1088/0031-9112/38/2/024/pdf
BEGIN EXCERPTS
The incorrect notion that mass can be converted to energy probably owes its origin to simplified popular accounts of nuclear fission processes, where emphasis is laid on the fact that the particulate fission products of uranium have a total rest mass somewhat less than that of the uranium atom and initiating neutron, while a very considerable amount of energy seems to have appeared from nowhere (as kinetic energy of products, energy of photons etc). But this energy has mass equal to the mass that seems to have disappeared. The energy has not come from nowhere; it was formerly present as potential energy of the arrangement of protons and neutrons prior to the fission â potential energy which has been diminished by the rearrangement into more stable fission products. It is the loss of this potential energy which gives rise to the apparent reduction in mass which is observed if one ignores the mass of the energy released. Potential energy has diminished and kinetic energy has increased. Mass of potential energy has diminished and mass of kinetic energy has increased. Energy has been conserved and mass has been conserved, each separately.
...
The best way to appreciate Einstein's conclusion is to realise that energy has mass. The best way to express it is to say that the mass of energy E is m, given by m = E/c².
Students should be taught that:
(i) energy has mass;
(ii) energy is always conserved;
(iii) mass is always conserved.
They should be warned against believing erroneous statements that mass and energy are interconvertible, and they should be urged to avoid such terminology as 'the equivalence of mass and energy'.
END EXCERPT
END CITATION
OK peeps. This talk page is for discussing improvements to the article. Not a general discussion as to the meaning of "mass", "matter", "Energy" and whatever, see WP:NOTAFORUM. The article is supported by reliable sources and we do not do our own original research here. You could discuss on Wikipedia:Reference desk/Science if you are struggling to find references and welcome to continue here if there are changes that you feel are needed to the article that are supported by sources. Best wishes Polyamorph ( talk) 10:00, 3 March 2017 (UTC)
I'm closing this discussion. If you want to talk more on this please take to Wikipedia:Reference desk/Science. Thanks. Polyamorph ( talk) 20:39, 3 March 2017 (UTC)
Mass and energy works alternative due to force. Force generate by formula 0=-0/-0 to create universe. 0= null sign. Its also involved in dark matter. Its nothing but some parts of null inside in something. Prashant Nanda 14:52, 14 March 2017 (UTC) â Preceding unsigned comment added by Twisindia ( talk ⢠contribs)
User RiverStyx23 seems to have a grammar-related problem with the phrase Already in his relativity paper "On the electrodynamics of moving bodies", Einstein derived..." and wants to replace it with In his relativity paper "On the electrodynamics of moving bodies", Einstein had already derived...":
We briefly discussed this on their talk page in the (now removed section) Grammar. I argue that
Thoughts? - DVdm ( talk) 07:08, 2 May 2017 (UTC)
e = mc^2 does not assert equivalence. How could mass and energy possibly be the same thing when there's blatantly a c-squared involved. They are interchangeable not equivalent. CMJAWHM3 ( talk) 14:18, 18 April 2017 (UTC)CMJAWHM
Equivalence as a term for mass/energy is perfectly fine; as they are both relativistic variables - whereas the speed of light is not. Therefore they are interchangeable. â Preceding unsigned comment added by 110.23.6.200 ( talk) 09:56, 12 May 2017 (UTC)
To expand on my above comment.
Equivalence as a term for mass/energy is perfectly fine; as mass and energy are both relativistic variables - whereas the speed of light is not. Therefore mass and energy are interchangeable, and also directly proportional to; each other, kinetic energy, and momentum. Perhaps the confusion about whether or not "equivalence" is the right term comes from the fact that mass has an inversely proportional relationship to the speed of light (as mass = E/C^2), whereas energy does not. The equivalence and interchangeability of mass and energy is also reasonably well substantiated by the practical examples section of the article. Dr. Jim Stanley. â Preceding unsigned comment added by 110.23.6.200 ( talk) 10:11, 12 May 2017 (UTC)
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It's very hard to find a simple answer to this, and the article doesn't help. One physicist told me it's related to the square in the formula for momentum (mass times velocity squared). Another told me it's ultimately derived from formula for calculating the relationship between the lengths of the sides of an equilateral triangle. Tony (talk) 13:48, 17 December 2017 (UTC)
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Article states that 9.0 Ă 10E16 Joules per kilogram is equivelent to 25,000 GWH/kg.
My repeated calculations give 25 GWH/kg.
But I am a lousy mathematician.
But this is an important error - if it is an error.
Can someone cleverer than I please check my result and reverse my correction if necessary (and tell me where I was wrong:- james@jbryant.eu).
JMBryant ( talk) 11:43, 8 December 2018 (UTC)
Unless I'm mistaken, c is not the speed of light. It is the universal speed limit, or universal constant. It happens to also be the speed at which light travels in a vacuum because light has no mass. But the speed of light varies with the medium, whereas c does not vary. -- 82.21.97.70 ( talk) 22:37, 6 March 2020 (UTC)
Do mass and energy refer to the same physical quantity? If it does, then speed of light would be dimensionless according to the famous formula. Therefore, the formula itself implies ironically that mass and energy cannot be the same. So, I think the first sentence of the section "conservation of mass and energy" should be edited. Somebody400 ( talk) 20:02, 15 January 2020 (UTC)
Hi all, I think this section should be completely rewritten or deleted. It contradicts the rest of the article, especially Conservation of mass and energy section, and it's contents are not echoed in the binding energy article or the mass defect section therein. Furthermore, there are no references I could use to determine what the authors meant in context. It is strange to claim that mass cannot be converted to energy, what about antimatter? The whole argument revolves around nuclear reactions, while in this case it's true that the binding energy exhibits mass and that is all that's being released, this ignores other phenomena. Massless photons do not have mass, neither do collections of them, that does not make any sense at all. Any thoughts? Footlessmouse ( talk) 06:12, 24 August 2020 (UTC)
bound system is typically at a lower energy level than its unbound constituents. "When a dispersed system [...] combines, [...] the total energy of the system must decrease by an amount , the binding energy [...]. The decrease in the total energy of the system must, according to relativity theory, be accompanied by a decrease in its mass, where ."-- --Jules (Mrjulesd) 06:56, 24 August 2020 (UTC)
The important point is that, when you consider moving bodies, is that only strictly works for stationary bodies. When considering moving bodies you need to use the Energyâmomentum relation: . Now the important point of this equation is that energy is not merely a function of the mass; it is also a fucntion of the momentum (p). Thus for moving bodies there is not a straight mass-energy relationship, as you must also consider changes in momentum if you want to calculate things correctly. Thus, although the photon is mass-less, it carries away momentum, and therefore, if the energy of the system is maintained (E), if there is an increase in the momentum (p), there must also be a corresponding drop in mass (m). This explains why a body emitting photons loses mass; the photons don't have mass, but do have momentum. Therefore the body emitting the photons loses mass. Now a very simple explanation is that "mass is converted into energy", but this ignores that fact that the familiar only strictly works for stationary bodies; the best way to consider it is as a special case of the Energyâmomentum relation when p=0. Then things should hopefully become clearer. There's a very good video on youtube which explains this, which I shall link to: [5] -- --Jules (Mrjulesd) 07:58, 24 August 2020 (UTC)
E always equals m*c^2, I can't agree with that at all. If a body has momentum the correct euation is , the momentum of the body must be taken into account, unless the mass we are talking about is relativistic mass; but since relativistic mass is usually not taken to be a physical quantity, is only a special case when p=0. And Electronâpositron annihilation makes perfect sense if you use the correct equations, mass is lost by the election-positron pair, but the resulting photons have momentum, and the Energyâmomentum relation is not violated. -- --Jules (Mrjulesd) 08:29, 24 August 2020 (UTC)
I will look for better sources, but the first one I looked through I found this:
A well established, university used textbook for introductory physics for scientists and engineers. This source alone puts the burden of proof on the article. Footlessmouse ( talk) 09:40, 24 August 2020 (UTC)
Also, here's good olld Griffith's from Introduction to Elementary Particles, page 101:
Please note, the italics were transcribed exactly as in the book. This is a HIGHLY reliable source. You will have a very hard time doing better unless graduate-level texts in relativity point to caveats not mentioned. This is solid proof of the sections misdirection. Footlessmouse ( talk) 09:59, 24 August 2020 (UTC)
To make my claim official: I propose this section is deleted in its entirety until such time as it can be rewritten in accord with current scientific understanding and consensus. The only references on the topic thus far directly contradict the section. I therefore contend that the section is in violation of Wikipedia's no original research policy and does not represent current widely accepted scientific views on the subject. Footlessmouse ( talk) 10:16, 24 August 2020 (UTC)
Hey, @ (Mrjulesd), I apologize if I came off as rude in any of this. I did not mean to bite. One of the biggest problems I had with article, though, was saying that mass is conserved in situations like matter-antimatter annihilations. You must pick or choose which picture to follow: either the matter-antimatter system is in a superposition with the 2-photons and are all ill-defined as they are trapped in an isolated box we cannot interact with (in this case, mass is conserved), or the annihilation results in two photons traveling in different directions and mass has been converted to kinetic energy in order to conserve momentum and energy. It is very confusing and unhelpful, in my mind, to talk about the mass being conserved by means of the two photons, and that view is not upheld in modern textbooks. The other main thing is, for statements of "relocating matter", the outgoing radiation doesn't have to interact with any matter, what if a single photon makes it all the way outside of the observable universe? Could you call mass conserved then? I think this is philosophy and is why modern jargon has evolved. Footlessmouse ( talk) 07:51, 25 August 2020 (UTC)
Massâenergy is not hyphenated with a dash - but with a other character: â. side by side: -â. this is not a character on the standard keyboard 201.229.12.77 ( talk) 21:41, 9 October 2020 (UTC)
In compounds when the connection might otherwise be expressed with to, versus, and, or between, and in this context I think the word would be "and". Hyphens indicate compound modifiers in this context, but I feel this is less relevant here. Jules (Mrjulesd) 22:03, 9 October 2020 (UTC)
From the section "mass in special relativity", the first sentence is accurate, but the second is confusing and should be omitted: "The rest mass of an object is the total energy of all the parts, including kinetic energy, as observed from the center of momentum frame, and potential energy. The masses add up only if the constituents are at rest (as observed from the center of momentum frame) and do not attract or repel, so that they do not have any extra kinetic or potential energy.[note 1]" I'm not confident about editing directly, but i think "centre of momentum frame" says it all, and while this applies it is not necessary to place constraints on the motion. Feydun ( talk) 07:03, 11 February 2021 (UTC)
Hi all, I have spent quite a bit of time going through and trying to organize and consolidate the article. (I apologize if I have blown up your watch feed) I also fixed all the decade old reference errors that prevented this article from being promoted to GA status. I removed a lot of duplicate material and quite a bit of material that read either like a textbook or an essay rather than an encyclopedia that also lacked citation was not easily findable. I rewrote many other parts for clarity, excluding unnecessary detail. If you believe I have made a mistake, please either correct it or let me know. Now that the material is consolidated, I hope it will be easier to work on each section to bring it up to standards. I need a break from editing this article for now as you reach a point of diminishing returns, but I would like to nominate this article for GA status in the coming weeks or months. I think it would be a great GA once everything is tidied up a bit and a few more references are added in. If anyone has thoughts, please let me know. Footlessmouse ( talk) 05:32, 15 October 2020 (UTC)
Nomenclature In Does the inertia of a body depend upon its energy-content? Einstein used V to mean the speed of light in a vacuum and L to mean the energy lost by a body in the form of radiation. Consequently, the equation E = mc2 was not originally written as a formula but as a sentence in German that meant if a body gives off the energy L in the form of radiation, its mass diminishes by L/V2. A remark placed above it informed that the equation was approximate because the conclusion was only justified if one neglected "magnitudes of fourth and higher orders" of a series expansion. In 1907, the einsteinian mass-energy relationship was written as M0 = E0/c2 by Max Planck and, subsequently, was given a quantum interpretation by Johannes Stark, who assumed its validity and correctness (GĹŤltigkeit). In 1925, Louis de Broglie assumed the correctness of the relationship "ĂŠnergie=masse c2" in his Research on the Theory of the Quanta. However, Einstein, even after the World War Two, wrote E = mc2 in the title of his article intended as an explanation for a "popular reader". Now, after your editions, Wikipedia again denies (?!) the readers their law to knowledge and simply contributes to cheating readers and the production of fools who one day may become angry. Why? Because equations like that one have their cultural and philosophical impact. People use them in songs and poems! And the famous E=mc2 is not there - why?
"... Solar eclipse of May 29, 1919.[15][16] During the solar eclipse, the English astronomer and physicist Arthur Eddington observed that the light from stars passing close to the Sun was bent. The effect is due to the gravitational attraction of light by the Sun. " - Light is bent by gravity in Newtonian gravity already, only is it 50% of the ovserved angle. But the last quoted sentence implies that this is qualitatively new with the theory of relativity. -- Felix Tritschler ( talk) 10:14, 16 May 2021 (UTC)
GA toolbox |
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Reviewing |
Reviewer: AhmadLX ( talk ¡ contribs) 17:10, 7 April 2021 (UTC)
Earwigs' shows a couple matches, but they are to be disregarded (see below). So copyvio is okay.
Broadness Okay.
All fine. A couple points added below for the record.
Good Article review progress box
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Hi, I hope to have time to work on this in the next week or so, I have not been on here in a while and am behind. So I agree with a lot of your points, the main deal is that I was a relatively new editor to the page and it didn't seem appropriate for me to gut everything, so I had to pick and choose which things I really needed fixed and I left the other stuff for others to deal with. Also, I am sure there are several references that need to be added in, especially when it comes to things like the history section, but overall, please see
WP:Scientific citation guidelines which states that statements such as "A frustrated spin glass may have a large ground state degeneracy." require no citation because they are "widely known among people familiar with a discipline". Most of the stuff you mention needs citations is known to all physicists and therefore does not need a citation; it can in fact be referenced to any introductory physics book, but there is no need for Wikipedia editors to suggest which of these introductory textbooks is best for the reader, that is a job for reddit. As I said, I will read everything over and try to work on it soon, it has been months though, so it may take a bit.
Footlessmouse (
talk)
05:07, 11 April 2021 (UTC)
Good Article review progress box
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Prose:
Reliable sources
I don't have a background in physics but I feel like this should be included as a section in this article.
Under the link below there is a relevant paper: https://aip.scitation.org/doi/pdf/10.1063/1.5123794
5.226.81.106 ( talk) 15:53, 28 October 2021 (UTC)
Yes, mass is still conserved in special relativity! Not if you let it out of your system, of course (as heat or light) but nothing is conserved (not momentum, either) if you do that. Alas, Einstein's 1905 thought experiment does that, and even he thought mass is conserved to energy sometimes, not realizing that the photons have mass (as a system).
I believe that Lev Okun goes into the history of early relativistic kinematics and it was Richard C. Tolman who gave us the energy-momentum relation in final form, about 1912. Unfortunately, it was also Tolman who suggested that we modify "mass" to "relativistic mass" m_rel = (E_rel)/c^2)" which would make E = mc^2 correct all of the time and disregard the momentum terms. This is not very helpful as you end with two kinds of masses (see Mass in special relativity) and since relativistic mass goes up and down with energy in a system in various frames it looks like mass is "converted" to energy. High velocity particles in this view become more "massive" instead of the modern view that they stay the same mass but pick up momentum as v(gamma) and not just v. They don't get "fatter." Or even more massive. Just harder to stop (more momentum). Most important, since rest mass and system invariant mass are invariant, they are useful, but relativistic mass is not invariant, so it's less useful.
Poor Einstein didn't like "relativistic mass" and said so. But he was also a victim of the idea that mass is "converted" to energy (and said so at the end of his life when "explaining" the bomb), when what is really happening is that particles are converted to energy (and vice versa), so "matter" may be converted to various types of energy but rest-mass cannot (instead the energy keeps the rest mass as invariant mass). Also (as in the A-bomb) potential energy can be converted to heat and light (exothermic chemical and nuclear reactions) but the mass does not change until the heat and light are removed, along with THEIR mass (but then it's not a closed system so no conservation law applies anyway). That's true of a chemical reaction in a sealed system on a scale (but you can't measure masses that small) and an atom bomb after you cool the products down (but that's too difficult). Einstein always thought in terms of his initial 1905 thought experiment where an object gives off two photons in opposite directions (so we maintain p = 0) and loses mass. But Einstein might not have known that although one photon has no mass, two photons in opposite directions and energies have p = 0 and thus DO have an invariant mass. That's the mass the object is missing! So mass conservation is a product of special relativity also, so long as you use rest-mass and system invariant mass. Einstein's object loses mass only because he ignores the mass of the photons after they are emitted, assuming that if each is zero mass, both will be zero mass also! Wrong! Einstein's experiment actually happens with neutral pions which decay to two photons with the same (invariant) mass. But we see one reason that a massive pion can't ever decay to ONE photon!
The fallacy that mass is lost (unless you lose it by letting it out of your system!) or converted to mass-less energy, has crept into the mass-energy equivalence article, although our two articles mass in special relativity and energy-momentum relation are still okay. Read the end of the first one for insight. The relevant paragraph of THIS article (Mass-energy equivalence) has to be fixed, but I wanted to introduce the problem here before doing it. The idea that mass is converted to energy in physics (a misreading of E=mc^2) is one of more persistent myths in physics-- still taught in some intro college classes. But not in SR relativity texts like Taylor and Wheeler. Anyway, discuss here before you-all jump on me for fixing this, in this article. S B H arris 04:27, 22 March 2022 (UTC)
I think that everyone that wants to edit should read this paper first: On the Abuse and Use of Relativistic Mass by Gary Oas. Basically, he affirms the whole "relativistic mass" thing is wrong (and yes, he affirms that if a body has energy E and mass m (invariant mass, rest mass, the only mass there should be), then the equation E = mc² is just wrong). And he shows that there are almost no textbooks (not even introductory ones) today that use that concept. Edelacroixx ( talk) 06:06, 11 July 2022 (UTC)
![]() | This is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
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The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.
Although terminology like "mass-energy equivalence" and "interconversion of mass and energy" is common, it is nevertheless incorrect.
Mass is an extensive property of matter. It is also an extensive property of energy. If you take a small isolated system containing matter, and weigh it, and if the matter inside the isolated system then gets converted to energy, and you weigh that isolated system again, there will be no change in its weight. If the matter within the isolated system had a mass of N grams, the mass of the resulting energy is also N grams.
So mass cannot be converted into energy. Really, it's matter that can be converted into energy. The mass of the resulting energy is equal to the mass of the matter that we began with.
Even physics researchers sometimes use sloppy language, figuring that everybody understands that it's not mass, but matter, that can be converted into energy. But they misjudge their audience, and the result is confusion everywhere. The result is an entire Wikipedia article that uses confusing language.
Rahul ( talk) 01:08, 2 March 2017 (UTC)
BEGIN CITATION
Energy has Mass: A common misunderstanding is re-examined.
Hermann Bondi and C B Spurgin.
Physics Bulletin, Volume 38, Number 2, 1987.
http://iopscience.iop.org/article/10.1088/0031-9112/38/2/024/pdf
BEGIN EXCERPTS
The incorrect notion that mass can be converted to energy probably owes its origin to simplified popular accounts of nuclear fission processes, where emphasis is laid on the fact that the particulate fission products of uranium have a total rest mass somewhat less than that of the uranium atom and initiating neutron, while a very considerable amount of energy seems to have appeared from nowhere (as kinetic energy of products, energy of photons etc). But this energy has mass equal to the mass that seems to have disappeared. The energy has not come from nowhere; it was formerly present as potential energy of the arrangement of protons and neutrons prior to the fission â potential energy which has been diminished by the rearrangement into more stable fission products. It is the loss of this potential energy which gives rise to the apparent reduction in mass which is observed if one ignores the mass of the energy released. Potential energy has diminished and kinetic energy has increased. Mass of potential energy has diminished and mass of kinetic energy has increased. Energy has been conserved and mass has been conserved, each separately.
...
The best way to appreciate Einstein's conclusion is to realise that energy has mass. The best way to express it is to say that the mass of energy E is m, given by m = E/c².
Students should be taught that:
(i) energy has mass;
(ii) energy is always conserved;
(iii) mass is always conserved.
They should be warned against believing erroneous statements that mass and energy are interconvertible, and they should be urged to avoid such terminology as 'the equivalence of mass and energy'.
END EXCERPT
END CITATION
OK peeps. This talk page is for discussing improvements to the article. Not a general discussion as to the meaning of "mass", "matter", "Energy" and whatever, see WP:NOTAFORUM. The article is supported by reliable sources and we do not do our own original research here. You could discuss on Wikipedia:Reference desk/Science if you are struggling to find references and welcome to continue here if there are changes that you feel are needed to the article that are supported by sources. Best wishes Polyamorph ( talk) 10:00, 3 March 2017 (UTC)
I'm closing this discussion. If you want to talk more on this please take to Wikipedia:Reference desk/Science. Thanks. Polyamorph ( talk) 20:39, 3 March 2017 (UTC)
Mass and energy works alternative due to force. Force generate by formula 0=-0/-0 to create universe. 0= null sign. Its also involved in dark matter. Its nothing but some parts of null inside in something. Prashant Nanda 14:52, 14 March 2017 (UTC) â Preceding unsigned comment added by Twisindia ( talk ⢠contribs)
User RiverStyx23 seems to have a grammar-related problem with the phrase Already in his relativity paper "On the electrodynamics of moving bodies", Einstein derived..." and wants to replace it with In his relativity paper "On the electrodynamics of moving bodies", Einstein had already derived...":
We briefly discussed this on their talk page in the (now removed section) Grammar. I argue that
Thoughts? - DVdm ( talk) 07:08, 2 May 2017 (UTC)
e = mc^2 does not assert equivalence. How could mass and energy possibly be the same thing when there's blatantly a c-squared involved. They are interchangeable not equivalent. CMJAWHM3 ( talk) 14:18, 18 April 2017 (UTC)CMJAWHM
Equivalence as a term for mass/energy is perfectly fine; as they are both relativistic variables - whereas the speed of light is not. Therefore they are interchangeable. â Preceding unsigned comment added by 110.23.6.200 ( talk) 09:56, 12 May 2017 (UTC)
To expand on my above comment.
Equivalence as a term for mass/energy is perfectly fine; as mass and energy are both relativistic variables - whereas the speed of light is not. Therefore mass and energy are interchangeable, and also directly proportional to; each other, kinetic energy, and momentum. Perhaps the confusion about whether or not "equivalence" is the right term comes from the fact that mass has an inversely proportional relationship to the speed of light (as mass = E/C^2), whereas energy does not. The equivalence and interchangeability of mass and energy is also reasonably well substantiated by the practical examples section of the article. Dr. Jim Stanley. â Preceding unsigned comment added by 110.23.6.200 ( talk) 10:11, 12 May 2017 (UTC)
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It's very hard to find a simple answer to this, and the article doesn't help. One physicist told me it's related to the square in the formula for momentum (mass times velocity squared). Another told me it's ultimately derived from formula for calculating the relationship between the lengths of the sides of an equilateral triangle. Tony (talk) 13:48, 17 December 2017 (UTC)
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Article states that 9.0 Ă 10E16 Joules per kilogram is equivelent to 25,000 GWH/kg.
My repeated calculations give 25 GWH/kg.
But I am a lousy mathematician.
But this is an important error - if it is an error.
Can someone cleverer than I please check my result and reverse my correction if necessary (and tell me where I was wrong:- james@jbryant.eu).
JMBryant ( talk) 11:43, 8 December 2018 (UTC)
Unless I'm mistaken, c is not the speed of light. It is the universal speed limit, or universal constant. It happens to also be the speed at which light travels in a vacuum because light has no mass. But the speed of light varies with the medium, whereas c does not vary. -- 82.21.97.70 ( talk) 22:37, 6 March 2020 (UTC)
Do mass and energy refer to the same physical quantity? If it does, then speed of light would be dimensionless according to the famous formula. Therefore, the formula itself implies ironically that mass and energy cannot be the same. So, I think the first sentence of the section "conservation of mass and energy" should be edited. Somebody400 ( talk) 20:02, 15 January 2020 (UTC)
Hi all, I think this section should be completely rewritten or deleted. It contradicts the rest of the article, especially Conservation of mass and energy section, and it's contents are not echoed in the binding energy article or the mass defect section therein. Furthermore, there are no references I could use to determine what the authors meant in context. It is strange to claim that mass cannot be converted to energy, what about antimatter? The whole argument revolves around nuclear reactions, while in this case it's true that the binding energy exhibits mass and that is all that's being released, this ignores other phenomena. Massless photons do not have mass, neither do collections of them, that does not make any sense at all. Any thoughts? Footlessmouse ( talk) 06:12, 24 August 2020 (UTC)
bound system is typically at a lower energy level than its unbound constituents. "When a dispersed system [...] combines, [...] the total energy of the system must decrease by an amount , the binding energy [...]. The decrease in the total energy of the system must, according to relativity theory, be accompanied by a decrease in its mass, where ."-- --Jules (Mrjulesd) 06:56, 24 August 2020 (UTC)
The important point is that, when you consider moving bodies, is that only strictly works for stationary bodies. When considering moving bodies you need to use the Energyâmomentum relation: . Now the important point of this equation is that energy is not merely a function of the mass; it is also a fucntion of the momentum (p). Thus for moving bodies there is not a straight mass-energy relationship, as you must also consider changes in momentum if you want to calculate things correctly. Thus, although the photon is mass-less, it carries away momentum, and therefore, if the energy of the system is maintained (E), if there is an increase in the momentum (p), there must also be a corresponding drop in mass (m). This explains why a body emitting photons loses mass; the photons don't have mass, but do have momentum. Therefore the body emitting the photons loses mass. Now a very simple explanation is that "mass is converted into energy", but this ignores that fact that the familiar only strictly works for stationary bodies; the best way to consider it is as a special case of the Energyâmomentum relation when p=0. Then things should hopefully become clearer. There's a very good video on youtube which explains this, which I shall link to: [5] -- --Jules (Mrjulesd) 07:58, 24 August 2020 (UTC)
E always equals m*c^2, I can't agree with that at all. If a body has momentum the correct euation is , the momentum of the body must be taken into account, unless the mass we are talking about is relativistic mass; but since relativistic mass is usually not taken to be a physical quantity, is only a special case when p=0. And Electronâpositron annihilation makes perfect sense if you use the correct equations, mass is lost by the election-positron pair, but the resulting photons have momentum, and the Energyâmomentum relation is not violated. -- --Jules (Mrjulesd) 08:29, 24 August 2020 (UTC)
I will look for better sources, but the first one I looked through I found this:
A well established, university used textbook for introductory physics for scientists and engineers. This source alone puts the burden of proof on the article. Footlessmouse ( talk) 09:40, 24 August 2020 (UTC)
Also, here's good olld Griffith's from Introduction to Elementary Particles, page 101:
Please note, the italics were transcribed exactly as in the book. This is a HIGHLY reliable source. You will have a very hard time doing better unless graduate-level texts in relativity point to caveats not mentioned. This is solid proof of the sections misdirection. Footlessmouse ( talk) 09:59, 24 August 2020 (UTC)
To make my claim official: I propose this section is deleted in its entirety until such time as it can be rewritten in accord with current scientific understanding and consensus. The only references on the topic thus far directly contradict the section. I therefore contend that the section is in violation of Wikipedia's no original research policy and does not represent current widely accepted scientific views on the subject. Footlessmouse ( talk) 10:16, 24 August 2020 (UTC)
Hey, @ (Mrjulesd), I apologize if I came off as rude in any of this. I did not mean to bite. One of the biggest problems I had with article, though, was saying that mass is conserved in situations like matter-antimatter annihilations. You must pick or choose which picture to follow: either the matter-antimatter system is in a superposition with the 2-photons and are all ill-defined as they are trapped in an isolated box we cannot interact with (in this case, mass is conserved), or the annihilation results in two photons traveling in different directions and mass has been converted to kinetic energy in order to conserve momentum and energy. It is very confusing and unhelpful, in my mind, to talk about the mass being conserved by means of the two photons, and that view is not upheld in modern textbooks. The other main thing is, for statements of "relocating matter", the outgoing radiation doesn't have to interact with any matter, what if a single photon makes it all the way outside of the observable universe? Could you call mass conserved then? I think this is philosophy and is why modern jargon has evolved. Footlessmouse ( talk) 07:51, 25 August 2020 (UTC)
Massâenergy is not hyphenated with a dash - but with a other character: â. side by side: -â. this is not a character on the standard keyboard 201.229.12.77 ( talk) 21:41, 9 October 2020 (UTC)
In compounds when the connection might otherwise be expressed with to, versus, and, or between, and in this context I think the word would be "and". Hyphens indicate compound modifiers in this context, but I feel this is less relevant here. Jules (Mrjulesd) 22:03, 9 October 2020 (UTC)
From the section "mass in special relativity", the first sentence is accurate, but the second is confusing and should be omitted: "The rest mass of an object is the total energy of all the parts, including kinetic energy, as observed from the center of momentum frame, and potential energy. The masses add up only if the constituents are at rest (as observed from the center of momentum frame) and do not attract or repel, so that they do not have any extra kinetic or potential energy.[note 1]" I'm not confident about editing directly, but i think "centre of momentum frame" says it all, and while this applies it is not necessary to place constraints on the motion. Feydun ( talk) 07:03, 11 February 2021 (UTC)
Hi all, I have spent quite a bit of time going through and trying to organize and consolidate the article. (I apologize if I have blown up your watch feed) I also fixed all the decade old reference errors that prevented this article from being promoted to GA status. I removed a lot of duplicate material and quite a bit of material that read either like a textbook or an essay rather than an encyclopedia that also lacked citation was not easily findable. I rewrote many other parts for clarity, excluding unnecessary detail. If you believe I have made a mistake, please either correct it or let me know. Now that the material is consolidated, I hope it will be easier to work on each section to bring it up to standards. I need a break from editing this article for now as you reach a point of diminishing returns, but I would like to nominate this article for GA status in the coming weeks or months. I think it would be a great GA once everything is tidied up a bit and a few more references are added in. If anyone has thoughts, please let me know. Footlessmouse ( talk) 05:32, 15 October 2020 (UTC)
Nomenclature In Does the inertia of a body depend upon its energy-content? Einstein used V to mean the speed of light in a vacuum and L to mean the energy lost by a body in the form of radiation. Consequently, the equation E = mc2 was not originally written as a formula but as a sentence in German that meant if a body gives off the energy L in the form of radiation, its mass diminishes by L/V2. A remark placed above it informed that the equation was approximate because the conclusion was only justified if one neglected "magnitudes of fourth and higher orders" of a series expansion. In 1907, the einsteinian mass-energy relationship was written as M0 = E0/c2 by Max Planck and, subsequently, was given a quantum interpretation by Johannes Stark, who assumed its validity and correctness (GĹŤltigkeit). In 1925, Louis de Broglie assumed the correctness of the relationship "ĂŠnergie=masse c2" in his Research on the Theory of the Quanta. However, Einstein, even after the World War Two, wrote E = mc2 in the title of his article intended as an explanation for a "popular reader". Now, after your editions, Wikipedia again denies (?!) the readers their law to knowledge and simply contributes to cheating readers and the production of fools who one day may become angry. Why? Because equations like that one have their cultural and philosophical impact. People use them in songs and poems! And the famous E=mc2 is not there - why?
"... Solar eclipse of May 29, 1919.[15][16] During the solar eclipse, the English astronomer and physicist Arthur Eddington observed that the light from stars passing close to the Sun was bent. The effect is due to the gravitational attraction of light by the Sun. " - Light is bent by gravity in Newtonian gravity already, only is it 50% of the ovserved angle. But the last quoted sentence implies that this is qualitatively new with the theory of relativity. -- Felix Tritschler ( talk) 10:14, 16 May 2021 (UTC)
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Reviewer: AhmadLX ( talk ¡ contribs) 17:10, 7 April 2021 (UTC)
Earwigs' shows a couple matches, but they are to be disregarded (see below). So copyvio is okay.
Broadness Okay.
All fine. A couple points added below for the record.
Good Article review progress box
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Hi, I hope to have time to work on this in the next week or so, I have not been on here in a while and am behind. So I agree with a lot of your points, the main deal is that I was a relatively new editor to the page and it didn't seem appropriate for me to gut everything, so I had to pick and choose which things I really needed fixed and I left the other stuff for others to deal with. Also, I am sure there are several references that need to be added in, especially when it comes to things like the history section, but overall, please see
WP:Scientific citation guidelines which states that statements such as "A frustrated spin glass may have a large ground state degeneracy." require no citation because they are "widely known among people familiar with a discipline". Most of the stuff you mention needs citations is known to all physicists and therefore does not need a citation; it can in fact be referenced to any introductory physics book, but there is no need for Wikipedia editors to suggest which of these introductory textbooks is best for the reader, that is a job for reddit. As I said, I will read everything over and try to work on it soon, it has been months though, so it may take a bit.
Footlessmouse (
talk)
05:07, 11 April 2021 (UTC)
Good Article review progress box
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Prose:
Reliable sources
I don't have a background in physics but I feel like this should be included as a section in this article.
Under the link below there is a relevant paper: https://aip.scitation.org/doi/pdf/10.1063/1.5123794
5.226.81.106 ( talk) 15:53, 28 October 2021 (UTC)
Yes, mass is still conserved in special relativity! Not if you let it out of your system, of course (as heat or light) but nothing is conserved (not momentum, either) if you do that. Alas, Einstein's 1905 thought experiment does that, and even he thought mass is conserved to energy sometimes, not realizing that the photons have mass (as a system).
I believe that Lev Okun goes into the history of early relativistic kinematics and it was Richard C. Tolman who gave us the energy-momentum relation in final form, about 1912. Unfortunately, it was also Tolman who suggested that we modify "mass" to "relativistic mass" m_rel = (E_rel)/c^2)" which would make E = mc^2 correct all of the time and disregard the momentum terms. This is not very helpful as you end with two kinds of masses (see Mass in special relativity) and since relativistic mass goes up and down with energy in a system in various frames it looks like mass is "converted" to energy. High velocity particles in this view become more "massive" instead of the modern view that they stay the same mass but pick up momentum as v(gamma) and not just v. They don't get "fatter." Or even more massive. Just harder to stop (more momentum). Most important, since rest mass and system invariant mass are invariant, they are useful, but relativistic mass is not invariant, so it's less useful.
Poor Einstein didn't like "relativistic mass" and said so. But he was also a victim of the idea that mass is "converted" to energy (and said so at the end of his life when "explaining" the bomb), when what is really happening is that particles are converted to energy (and vice versa), so "matter" may be converted to various types of energy but rest-mass cannot (instead the energy keeps the rest mass as invariant mass). Also (as in the A-bomb) potential energy can be converted to heat and light (exothermic chemical and nuclear reactions) but the mass does not change until the heat and light are removed, along with THEIR mass (but then it's not a closed system so no conservation law applies anyway). That's true of a chemical reaction in a sealed system on a scale (but you can't measure masses that small) and an atom bomb after you cool the products down (but that's too difficult). Einstein always thought in terms of his initial 1905 thought experiment where an object gives off two photons in opposite directions (so we maintain p = 0) and loses mass. But Einstein might not have known that although one photon has no mass, two photons in opposite directions and energies have p = 0 and thus DO have an invariant mass. That's the mass the object is missing! So mass conservation is a product of special relativity also, so long as you use rest-mass and system invariant mass. Einstein's object loses mass only because he ignores the mass of the photons after they are emitted, assuming that if each is zero mass, both will be zero mass also! Wrong! Einstein's experiment actually happens with neutral pions which decay to two photons with the same (invariant) mass. But we see one reason that a massive pion can't ever decay to ONE photon!
The fallacy that mass is lost (unless you lose it by letting it out of your system!) or converted to mass-less energy, has crept into the mass-energy equivalence article, although our two articles mass in special relativity and energy-momentum relation are still okay. Read the end of the first one for insight. The relevant paragraph of THIS article (Mass-energy equivalence) has to be fixed, but I wanted to introduce the problem here before doing it. The idea that mass is converted to energy in physics (a misreading of E=mc^2) is one of more persistent myths in physics-- still taught in some intro college classes. But not in SR relativity texts like Taylor and Wheeler. Anyway, discuss here before you-all jump on me for fixing this, in this article. S B H arris 04:27, 22 March 2022 (UTC)
I think that everyone that wants to edit should read this paper first: On the Abuse and Use of Relativistic Mass by Gary Oas. Basically, he affirms the whole "relativistic mass" thing is wrong (and yes, he affirms that if a body has energy E and mass m (invariant mass, rest mass, the only mass there should be), then the equation E = mc² is just wrong). And he shows that there are almost no textbooks (not even introductory ones) today that use that concept. Edelacroixx ( talk) 06:06, 11 July 2022 (UTC)