Talk:Conservation of energy/Archive 4

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Archive 4

Time crystals

@Sparkyscience:

Last week's edits on time crystals misstate the connection to the article topic. The sources cited (or at least Cowen, Powell, and Gibney which I can access) confirm that time crystals violate time translation symmetry. They also add that time crystals are a type of perpetual motion. But they do not add that time crystals violate the conservation of energy. In fact Cowen states that "This type of perpetual motion machine would not violate any known physical law because no energy could be extracted from the system without first adding energy.", and Gibney says "Time crystals are hypothetical structures that pulse without requiring any energy". The Time crystal article provides a more correct statement in its Thermodynamics section. I will attempt to revise the sentence in this article. Dirac66 (talk) 00:55, 20 May 2017 (UTC)

@Dirac66: Sorry but this is not correct: time translation symmetry defines conservation of energy, thus if a system violates time translation symmetry it violates conservation of energy by definition. When we talk about "laws of physics" what we really mean is the symmetries of equations. As wilzciek states coyly in his original paper " Fields or particles in the presence of a time crystal background will be subject to energy-changing processes, analogous to crystalline Umklapp processes. In either case the apparent non-conservation is in reality a transfer to the background." [1]. While the experiments performed thus far are driven by lasers, in principle a time crystal can be driven by the quantum vacuum at absolute zero i.e. empty space. In fact it is this is the same type of perpetual motion / broken symmetry as say that of the spin of an electron. The concept of energy doesn't really apply to these nonlinear systems for the same reason it doesn't really apply in general relativity.--Sparkyscience (talk) 15:07, 20 May 2017 (UTC)

@Dirac66:, @Sparkyscience: is right and the wilzciek quote makes this clear. The word "apparent" before "non-conservation" is to indicate that there is not really any non-conservation. The equations for the time crystal may not have time translation symmetry but this is only because the crystal is being treated as a fixed background. If the dynamics of the background are also included then the underlying equations have time-symmetry and energy conservation holds with energy being transferred to and from the background. Actually the situation in general relativity is exactly the same and energy is conserved there too. I don't think time-crystals should be discussed here at all and certainly not in the opening section. It would be better to clarify the status of energy conservation for time-crystals on their own page Weburbia (talk) 18:04, 20 May 2017 (UTC)

@Weburbia:, @Sparkyscience:I agree that the non-conservation is only apparent as per Wilczek's paper. But that is not what this Wikipedia article now says. The statement in the intro that "new states of matter violate ... the conservation of energy" can be taken by a naïve reader to mean that scientists have recently discovered how to "violate" the conservation of energy. So some change to the article is needed please, in order to explain that the effect is only apparent and is driven by the quantum vacuum. If my version is unsatisfactory, could one of you two please insert a better one?

I also agree that this topic should not be in the intro where it may confuse beginning readers just starting to learn about conservation of energy. But I do think it should have a section further down for more advanced readers who have heard the news about time crystals and want to see what this article says about them. As I said above, the Time crystal article already provides a more correct statement in its Thermodynamics section. Dirac66 (talk) 22:14, 20 May 2017 (UTC)

What's this about 'time crystals'? They may be a real concept, but not relevant here. Looks like a neologism trying to draw attention... just one of countless concepts that, in the end, obey energy conservation. Geroniminor (talk) 03:47, 21 May 2017 (UTC)

I have removed the section about time crystals because it is clearly not a violation of energy conservation as pointed out by @Dirac66:. I tend to agree with @Geroniminor: that this is a neolgism and too specific to be included here. This seems to be the result of a misleading headline mentioning perpetual motion. If someone thinks this merits a mention on this page I suggest they draft a short section for discussion here before including it in the main article. Weburbia (talk) 06:24, 21 May 2017 (UTC)

I wrote the majority of the time crystal article in its current form, including the thermodynamics section in this edit here [2]. The thermodynamics section is not ideal as it was written some time ago and treats the time crystal system as an equilibrium system (which have been proven to be impossible), the time crystals discovered most definitely partake in energy processes, but the current thermodynamics section is unfortuately one of the few sources in the literature that directly address the issue (ie. laws of thermodynamics) head on at this current time. In any normal sense, time crystals, as discovered, violate conservation of energy, and they are the first state of matter known to do so. They are therefore, obviously, an important discovery (possible Nobel prize next year? Things have been handed out for less...). Yes if you take the background into account symmetry is restored as in GR, but I agree with Sean Carrol here in his article titled "Energy is not conserved" [3] "I personally think it’s better to forget about the so-called “energy of the gravitational field” and just admit that energy is not conserved, for two reasons..." No average person includes empty space when considering conservation laws, nor will they understand the key point if we do include it. All nonconservations can be viewed as a transfer to the vacuum but we don't usually claim that "spontaneous symmetry breaking" isn't really symmetry breaking at all!...Time crystals "bend the cast-iron laws of thermodynamics" [4].

I don't know how you can treat research published by multiple groups in Nature [5] and reported in every major scientific outlet a negolism. [6] [7] [8] [9] [10] I can understand editors caution over systems that claim to break the laws of physics (by which we mean a symmetry), but this is the real deal.

What is most key is that readers of "conservation of energy" understand the domain of where this law of physics applies - namely closed linear systems that have time translational symmetry. Where this is not the case, in open nonlinear systems, like high energy plasmas [11], gravitating systems [12] and time crystals the conservation of energy does not apply. I would argue time crystals are probably the best example here, because in others there is the temptation to think energy is "borrowed" from somewhere else, which is not the case. The universe is not a zero-sum game.--Sparkyscience (talk) 08:46, 21 May 2017 (UTC)

You seem to be claiming that energy conservation is only for linear static systems. Energy conservation works for all systems, linear or non-linear, where the dynamical equations are time-translation invariant, including time crystals and general relativity. Anything that changes breaks translation symmetry dynamically. What is special about the time crystal is that it changes while in its ground state, i.e. time-translation is broken spontaneously. This does not mean that energy conservation is violated. It is the equations that need to be invariant, not the solution. Ordinary crystals spontaneously break translation symmetry but they don't violate momentum conservation. You can't use crystals to generate a reactionless engine and you can't use time crystals to generate energy, nor is energy conservation violated in any other way. To be able to say something in wikipedia you need a reliable source. None of the sources cited (reliable and otherwise) say that energy is not conserved.Weburbia (talk) 15:49, 21 May 2017 (UTC)

""crystalline systems are not invariant under arbitrary translations, therefore, strictly speaking, momentum is not conserved."Fundamentals of the Physics of Solids, p. 191, at Google Books

Crystals do not conserve momentum. This is basic textbook physics stuff. Thats why rather then talk about momentum in crystals we talk about Quasimomentum. And Umklapp scattering demonstrates quite clearly what momentum violations looks like. Without momentum violations key properties of crystals would not be present.

With time crystals the same principle applies (we use the term "quasienergy" instead of energy because technically energy is not conserved). When i talk about linear i mean the "linear equations", sorry for not making that clear, where you can separate variables, i'm not referring to the value of the equations. i.e. per what i wrote here:"Symmetries apply to the equations that govern the physical laws rather than the initial conditions, values or magnitudes of the equations themselves and state that the laws remain unchanged under a transformation. [13]. With nonlinear i am referring to equations where you cannot separate variables.--Sparkyscience (talk) 19:04, 21 May 2017 (UTC)

If you treat a crystal as a fundamental structure without continuous translation symmetry then the system will have only quasimomentum, but in the real world the crystal is made of atoms that are bound by forces governed by equations with continuous translational invariance, so when all processes are taken into account momentum must be conserved. Noether's Theorems are completely general and work for all physical systems derived from a Lagrangian principle. There are no extra assumptions such as that variables need to be separable. Weburbia (talk) 21:22, 21 May 2017 (UTC)

Historical perspective

Perhaps some historical perspective is needed in deciding to how to discuss time crystals here. In the past, the definition of total energy has gradually been expanded. In the 17th century, what was supposed to be conserved was just macroscopic kinetic energy plus potential energy, as for a simple pendulum or an orbiting planet. Gradually it was realized that one had to include heat, electrical and magnetic energy, relativistic mass energy etc. etc. Each time the eventual consensus was not that energy conservation is “violated”, but rather that the complete calculation of energy requires new terms to be added. I think that many physicists (though perhaps not all) share the same viewpoint for quantum effects such as the Casimir effect and time crystals. Energy conservation should not be described as “violated”, but the calculation of energy must include the energy stored in the quantum field of the vacuum in order to obtain a conserved quantity.

As for the inclusion of time crystals in the article, I agree with Weburbia that this subject is too complex for the intro. Instead I propose that we move Sparkyscience’s 2 sentences “For equations of motion … were discovered.” to the section on Noether’s theorem, which seems to be the theoretical basis of the time crystal controversy. Then we could add that the violation is only apparent, and can be resolved by modifying the definition of total energy by including …

It might also be appropriate to add 1-2 sentences to the intro to say in general terms that the definition of the conserved quantity total energy has been extended many times over the centuries as new phenomena have been discovered. The examples are of course found in the history that follows, all the way from Rumford 1798 to Wilczek 2017. Dirac66 (talk) 23:42, 21 May 2017 (UTC)

The inserted sentences were wrong and have no place in Wikipedia. I have removed them again. I have no objection to the inclusion of a section on time crystals lower down if someone wants to write it but it should be brief with a link to the time crystals article to avoid repetition. The statement that time crystals are a new state of matter that violate energy conservation is simply not true. Before you know it people will be tricked into investing money in research to extract energy from time crystals. The mention of non-linearity is also not relevant.

Adding something on the historical context is a good idea.

I find that a lot of people are confused about how Noether's theorem works and this leads to an incorrect belief that energy is really not conserved in some situations such as GR. People get confused between the invariance of the dynamical equations and the dynamical solution. Sometimes a partial solution (e.g. in the form of an energy potential) can be treated as a fixed background so that it becomes part of the equations for a dynamical system. This can lead to a description of a system where the conservation law does not hold, but only because that system is then an approximate and incomplete model of nature. This really needs to be spelt out somewhere, e.g. in the article on Noether's Theorem. Weburbia (talk) —Preceding undated comment added 08:20, 22 May 2017 (UTC)

I hope we are talking past each other here: with respect to your earlier comment on linear/nonlinear: the separation of variables is intimately tied to the existence of symmetries or lack thereof. Seperation of variables, in general, can only be done for sets of linear equations. For example see Symmetries in Physics, p. 21, at Google Books and references contained herein:

• Miller, W. (1977). Symmetry and Separation of Variables (1984 ed.). Cambridge: Cambridge University Press. ISBN 0-521-30224-2. LCCN 85121093. OCLC 12050586. {{cite book}}: Invalid |ref=harv (help)
• Stephani, H. (1989). Differential Equations: Their Solution Using Symmetries. Cambridge: Cambridge University Press. ISBN 0-521-35531-1. LCCN 88036744. OCLC 758075610. {{cite book}}: Invalid |ref=harv (help)
• Oliver, P. J. (1993). Applications of Lie Groups to Differential Equations (2nd ed.). New York: Springer-Verlag. ISBN 0-387-94007-3. LCCN 92044573. OCLC 872604978. {{cite book}}: Invalid |ref=harv (help)

As the Witten paper makes absolutely clear,[14] Minkowski space, which can be manipulated using linear algebra, conserves energy. This is not true for other spacetime geometries. Most energy and mass in the universe appears "out of nowhere" due to the geometry and topology of the manifold (See Quantum chromodynamics binding energy). Or, in respect to momentum, these articles: [15] [16].

So far I have backed up everything I have said with reliable sources, you seem to be making basic errors in mathematical understanding and have not cited any reliable sources. Please do not remove content from the article which is factually correct and referenced. There is a wider discussion about best placing for the lede or not which I think is worth entertaining.--Sparkyscience (talk) 09:48, 22 May 2017 (UTC)

@Dirac66: I do think the main source of debate here is differences in definitions. Per Sean Carroll's example [17] I am wary of setting a standard that includes "empty space" to restore symmetry, namely because we lack a complete theory that accounts for the behaviour of the vacuum. Are there any reliable sources to back this view up?--Sparkyscience (talk) 10:06, 22 May 2017 (UTC)

@Sparkyscience: The sources you have given do not support what you are claiming. The quote you took from Wilczek says the opposite about energy conservation because it calls non-conservation "apparent", i.e. not really there. As you admit yourself separability of variables only applies to linear systems whereas energy conservation and Noether's theorem are completely general for non-linear systems, so your point is irrelevant no matter how many sources you can find about separability of variables and symmetry. Weburbia (talk) 12:08, 22 May 2017 (UTC)

@Dirac66: @Sparkyscience: The apparent missing energy is not in "empty space". For time crystals it is in the electromagnetic field. For general relativity it is in the gravitational field. I have requested dispute resolution to avoid an escalating edit war.Weburbia (talk) 12:30, 22 May 2017 (UTC)

"energy conservation and Noether's theorem are completely general for non-linear systems"? think can see why you're struggling. Let me try to help. Time translation implies the form of the equation is the same at $t$ and $t+\tau$ for any value of $t$ and $\tau$. For simplicity, this generally means I can separate $t$ on one side of the expression and set it equal to something not containing $t$ on another side of the expression. If I cannot do this then the equation, in general, is nonlinear. An example of this might be where $t+\tau$ depends on some previous value of $t$ such that the form of the expression changes. Nonlinear expressions are absolutely not covered by Noether's theorem. Do you have the same definition that i do?

A handy way of thinking about it is that linear equations are where a continous isolated variable can be set equal to something. A nonlinear equation is where the isolated variable cannot be set to equal something. there is no expression, that is there is no equality to equate something for something else. like a Lorenz system. Nonlinear systems, can be thought of as not equations to be solved but processes to be followed, for example the mandlebrot set is a shape not defined by the solution to an equation but defined by a process. In general relativity the same principle applies we cannot always solve for a centre of mass - it may dynamically change at any given time for non-stationary fields. See Mass in general relativity for details on nonlinear issues.

Back to the time crystal example - I cannot exchange $t$ and $t+\tau$ at discrete intervals - i.e. it is not a continuous function that can be defined - therefore this is a technical violation of the conservation of energy - as with the cited crystal momentum example above.

Any apparent non-conservation in nature - be it energy, momentum, parity, charge, relative phase etc... can always no be accounted for as a transfer to or from the vacuum state. But this is changing the common sense definition that I think everybody, scientists included, accepts. I think the argument set out by Sean M. Carroll [18] is the one we should reflect in this article:

back when you thought energy was conserved, there was a reason why you thought that, namely time-translation invariance. A fancy way of saying “the background on which particles and forces evolve, as well as the dynamical rules governing their motions, are fixed, not changing with time.” But in general relativity that’s simply no longer true. Einstein tells us that space and time are dynamical, and in particular that they can evolve with time. When the space through which particles move is chIanging, the total energy of those particles is not conserved.

--Sparkyscience (talk) 12:59, 22 May 2017 (UTC).

I note that this latest source by Carroll does say explicitly that energy is not conserved, at least in general relativity. For both GR and time crystals, there may not be a clear consensus among physicists, but there are probably enough sources for a comment in the introduction provided we are not too unequivocal. Perhaps something like There are still questions about the general validity of conservation of energy, for example in general relativity, and in the recently discovered time crystals. Detailed discussions should be further down in the article or in other articles. Dirac66 (talk) 15:48, 22 May 2017 (UTC)

Yeah I agree, perhaps the proper thing to do is to avoid the incendiary terminology "violations" of conservation of energy and merely talk about domains of validity: i.e. energy conservation can only be defined on spacetimes which exhibit continous time translational symmetry. Most prominently Euclidean or Minkowski spacetimes that pretty much account for nearly all of our everyday experience.

• "Time translation symmetry is guarenteed only in spacetimes where the metric is static: that is, where there is a coordinate system in the metric coeffients contain no time variable. Many GR systems are not static in any frame of reference so no conserved energy can be defined" Einstein's Genie: Spacetime out of the Bottle, p. 159, at Google Books
• "Notice that a general gravitational field will not be stationary in any frame, so no conserved energy can be defined." A First Course in General Relativity, p. 180, at Google Books--Sparkyscience (talk) 16:07, 22 May 2017 (UTC)

Time Crystal edit in introductory section is still not correct

The added sentences in the introductory section are still wrong and will only add confusion for people trying to understand conservation of energy. The references given do not support that statements claimed. It is a pity that the article is being edited immediately before the discussion here has been completed and agreed.

In the case of time crystals, none of the references cited nor any other sources have questioned or said that conservation of energy cannot be defined. In fact time crystals are governed by the underlying laws of quantum electrodynamics for which energy conservation is well understood. What is interesting about time crystals in the context of energy conservation is that they provide a form of perpetual motion because time translation symmetry is spontaneously broken in the ground state. This means they are in a constant state of oscillatory change, but the energy is well defined and constant and no energy can be extracted from a ground state. A perpetual motion machine of the first kind would require that an unlimited amount of energy can be extracted. The spontaneous breaking of time translation symmetry does not effect the law of energy conservation as derived from Noether's theorem because the theorem only requires that the equations of motion be invariant, which they are. Spontaneous symmetry breaking only means that the solution of those equations is not invariant.

The statement about energy conservation in general relativity is also misleading. The reference cited by Witten actually analyses the case of an isolated system in which everything can vary with time. Energy conservation is well formulated and understood for this case. Witten's paper shows that unlimited energy cannot be extracted from such a system given reasonable physical assumptions. He questions the status of the law of conservation of energy in more general cases but not in relation to time translation symmetry, so the reference does not support the sentence to which it is attached. The status of energy conservation in general relativity is best described as disputed. Some of the statements about energy conservation in Wikipedia articles are incorrect and should also be fixed, but I suggest we concentrate on resolving the time crystal dispute before tackling the more complex case of general relativity.

I think this subject is too subtle for a cursory statement in the introductory section where it is likely to generate misunderstanding. A section on energy in time crystals further down would be more suitable. Weburbia (talk) 08:17, 23 May 2017 (UTC)

You can tell you're a physicist and not a mathematician! I'll try and make things simple because I can tell this is an area you are not familiar with at all:

• "time crystals are governed by the underlying laws of quantum electrodynamics for which energy conservation is well understood". Time crystals are not governed by the standard formulation of QED at all. They are what is know as topological states: In the standard mathematical formulation of QED every point in space is modelled as a quantum harmonic oscillator, where each point is a Hamiltonian which strictly obeys time translational symmetry. The domain of QED is an abelian Minkowski spacetime which is topologically trivial (flat). The electromagnetic field can be generalized to other spacetime topologies via Yang-Mills and results in a non-abelian group that does not fit into the normal QED model. Yang-Mills describes situations where the potential fields are not trivial. Last year the 2016 Nobel prize in physics was awarded for the discovery of topological order where long-range quantum entanglements (i.e. nonlocal, global topological functions) lead to many amazing emergent phenomena, such as fractional electric charges, magnetic monopoles [19], Majorana fermions [20], negative mass (the breaking of galilean covarience [21]) and....time crystals. These quantum many-bodied correlations can even lead to causality - locating things in time and space - completely breaking down [22]. Can QED characterize any of this ? No. It contains no notion of topology. Quantum field theory has been extended by Witten and others to to topological quantum field theories. It is the properties of space and time which give rise to the laws of physics - our best physicists (Maldacena, Witten, Wilczek etc) see spacetime itself and thus all the laws of physics as emergent of something more fundamental. Topology can also be used to explain nonlocal, global effects in the Aharonov–Bohm effect and Berry phase where QED does okay as an approximation...but cannot describe the effects fully. Topology leads to things being path dependant...and thus quantities (like energy, charge, spin whatever...may not be preserved). We used to think all laws of physics could be characterized by symmetries and the symmetries they break, i.e. geometry...but these states are characterized not by geometry but by topology. The relationship between conserved Noether charges and topological charges is the current cutting edge of physics. It is not well understood AT ALL.

• "This can lead to a description of a system where the conservation law does not hold, but only because that system is then an approximate and incomplete model of nature" This is a major major misunderstanding of the nature of nonlinear systems. It is a feature of the system not a fault in our understanding of the system that conservation rules may not hold. It is conservation rules (whatever they may be) that lead to the power of prediction (i.e I can plug in any value of $n$ into the equation and calculate exactly what the state will look like at time in the future or past) In nonlinear systems this cannot be done, we must expend energy and iterate each value of $n$ to know the end state... and even then the reality may look completely different to our model because of the sensitivity on initial conditions. We may in certain circumstances be able to take the limit of an iteration, but in general this cannot be done. Another example of a nonlinear system is the three body problem (or n-body problem -which actually is a great analogy to the many body localization problem found in condensed matter physics in the above!) What makes it so difficult? Because given a set of initial conditions it is practically impossible to determine what the state ahead of time is going to be. Predictive power breaks down because the system may never settle down into equilibrium, that is there is no equality where we may isolate a variable and say what a state is going to be ahead of time. Thermodynamics are all about systems that settle into thermal equilibrium - for both gravitating many bodied systems in GR or many bodied localization problems in condensed matter physics - this may never happen. The limit of a nonlinear system can be characterized as a probability distribution (nonlocal pilot wave theories in quantum mechanics take advantage of this fact [23]). The reason general relativity was way ahead of its time is because it is a nonlinear theory. The whole success of western science for centuries has been based on a linear, reductive way of thinking. We are still barely at the cusp of understanding nonlinear science (chaos, emergence, self organization etc...) and what it means for our way of thinking about the universe. It is clear (to me at least) that it is just as profound as relativity or quantum mechanics (namely because both can be viewed in the frame of nonlinear systems!). I would strongly recommend watching these links [24] [25] and reading this book for a general overview [26]. Do not fall into the trap of thinking that just because there is no expression that can define an isolated variable, it is somehow an unphysical manifestation that does not fit into our reality. Nonlinear systems are just as real in the world as linear systems, but we barely understand them.--Sparkyscience (talk) 12:29, 23 May 2017 (UTC)

Since you are resorting to ever stronger insults I will make this my last comment. I assure you that my level in both mathematics and physics is well above anything you have said. Time crystals are ultimately governed by the underlying principles of the standard model and are almost entirely determined by QED because no nuclear physics is expected to be involved in a significant way. Energy conservation is a basic principle of the underlying physics and even if there are aspects of emergence that are not fully understood, we still know that the energy conservation law must hold because it is proven for the standard model in general terms. The phenomena that are emergent in condensed matter theory are very interesting but there is no reason to think that they are not emergent from QED alone. Indeed, nobody other than you is questioning the validity of the law of energy conservation for time crystals in any way.Weburbia (talk) 17:03, 23 May 2017 (UTC)

Personally I wouldn't find it insulting to admit that something is outside of my area of expertise. Topological effects are universal can be present at all energy scales and are not confined to nuclear physics. Topological charges are solitons. Solitions are standing wave solutions to nonlinear field equations which cannot be found by the perturbation of linear field theories. QED is a linear field theory. QED views electromagnetism as an abelian U(1) gauge theory. Quasiparticles found in condensed matter like the Majorana fermions require electromagnetism to be an non-abelian SU(2) gauge. The standard model does not take into account topological charges because the duality between "fundamental" noether particles and their topological counterparts is merely conjectured. That doesn't mean these conjectures that are beyond the standard model are not of practice use in laboratories today or have not lead to Nobel prizes being handed out last year... Time crystals can, in theory, can be made from Majorana fermions (which are not part of the standard model). To suggest that a linear theory of QED can give rise to emergent effects is oxymoronic: A requirement for any emergence or complexity is nonlinearity. Read the papers: The way they know time translation symmetry has been broken is a many bodied system (i.e system that never reaches thermal equilbrium) spontaneous doubles of the time period of a Hamiltonian at discrete intervals. That is the Hamiltonian is time dependant and total energy is not conserved if we do not take into account the effect of the vacuum. In equilibrium systems the Hamiltonian is time-invarianient at all points.--Sparkyscience (talk) 10:44, 24 May 2017 (UTC)

In QED The coupling between the electromagnetic field and Dirac fermions in non-linear. All of chemistry and condensed matter physics reduces to QED. Weburbia (talk) 14:23, 24 May 2017 (UTC)

For renormalization or pertibation theory I can take the limit of a function and isolate the variable i.e it converges to a linear equation. In general this may not be done for solitons, quasiparticles, QCD etc--Sparkyscience (talk) 08:36, 25 May 2017 (UTC)

I agree with Weburbia; many RSs state that time crystals do not violate conservation of energy.[27], [28], [29] @Sparkyscience: your voluminous comments are irrelevant. As Weburbia said, unlike other moving objects, energy cannot be extracted from a time crystal because it is in its quantum ground state. This is also the reason that it can continue moving for a long time (not necessarily perpetually, since it is not in a state of maximum entropy [30] but much longer than other moving objects). For this reason, the motion of a time crystal doesn't represent kinetic energy, it's energy is zero - it has "motion without energy". [31], [32] --Chetvorno^TALK 22:00, 22 November 2017 (UTC)

Annihilation

Sorry, but NOPE! to this law. Annihilation (both electron and positron have mass and they transform it to energy - electromagnetic stuff in time and space). No word "statistic", no to law.

37.48.8.177 (talk) 18:36, 10 July 2019 (UTC)mooph

IP, didn’t your college teacher explain the rest energy? Incnis Mrsi (talk) 18:40, 10 July 2019 (UTC)

at this level I don't believe in speed without acceleration... pls see conservation of mass discussion.. .thanx 37.48.8.177 (talk) 19:13, 10 July 2019 (UTC)mooph

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pure energy

"Theoretically, this implies that any object with mass can itself be converted to pure energy"

Please define "pure energy". Darsie42 (talk) 18:08, 27 April 2020 (UTC)

This sentence is intended to say that theoretically the mass of an object can be converted completely to energy so that the object no longer exists and in its place there is only energy. Dolphin (t) 21:01, 27 April 2020 (UTC)

Does that mean it wasn't energy before and then it turned into energy? Does that violate the conservation of energy? Or was it impure/diluted/dirty energy before? Hmm, or was the energy there at all times, but it was stripped from mass/matter? Then again photons have mass, too. A theoretical way to create a small black hole is to send many photons to one point. And even increasing potential energy, e.g. a spacecraft with a light sail being raised with external lasers, increases the mass of the solar system. Darsie42 (talk) 07:47, 26 May 2020 (UTC)

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Isn't nuclear fission and fusion extremely common?

From the first paragraphs: "Theoretically, this implies that any object with mass can itself be converted to pure energy, and vice versa, though this is believed to be possible only under the most extreme of physical conditions, such as likely existed in the universe very shortly after the Big Bang or when black holes emit Hawking radiation. "

It seems amiss to not mention these phenomena. — Preceding unsigned comment added by 76.69.219.39 (talk) 09:06, 31 October 2020 (UTC)

I believe it refers to total conversion of mass into energy, which that we know of only happens in annihilation reactions, whereas nuclear and chemical reactions only result in partial conversion. And calling it "partial" is quite generous, since even in hydrogen fusion merely 0.7 % of the mass is converted. In chemical processes like methane combustion, the fraction is less than a billionth. —Julen Artano (talk) 17:30, 16 July 2024 (UTC)