Talk:Conservation law

Untitled

Someone more knowledgable could perhaps combine the information from Conservation laws into this topic and redirect from there. I'm linking here from conservation, which discusses the social ethic of conservation, as opposed to the physical laws (axioms?).BobCMU76 17:00 May 10, 2003 (UTC)

conservation links to a disambiguation --H2g2bob 14:51, 20 January 2006 (UTC)

The astonishing level of incompetence

The astonishing level of incompetence of the people involved is showed in the quality of the page and of the discussion below. Here is what I edited and being censored after one hour:

In physics, a conservation law, better called an invariance law, states that a particular measurable property or observable of a physical system does not change when a mathematical transformation is applied to other observables in the system.

A typical example can be the case of Temperature that does not change over time. In such a case the observable is the temperature and the transformation of the invariance law is a translation along the time coordinate.

Examples

I think this page could really benefit from a nice example that illustrates exactly why this is a good notion of conservation. It would also help clear up what

y_t + j_x (y)= 0

for example means. As j_x is now a function of time and the function y. It might also be helpful to write this explicitly without any notation.

What is the predication

For the one dimensional case is j a conserved quantity if that equation holds for all y? — Preceding unsigned comment added by 136.159.16.20 (talk) 23:43, 14 October 2015 (UTC)

— Preceding unsigned comment added by 136.159.16.14 (talk) 22:38, 14 October 2015 (UTC)

Importance

In modern physics the concept of invariance vs transformation plays a central role in all the theories after special relativity. In the context of special relativity the real invariant is the speed of light against all possible coordinate transformations and therefore the Lorentz transformations are derived. Most of the theories in the context of quantum field theory have a Lagrange formulation where the starting point to build the theory is the definition of the invariants. From the invariants a specific Lagrange function is chosen and from the last a set of equations are derived.

Invariance imply a mind shift to the end of the understanding of physics (and to the end of learning it). In the case of special relativity, also called by Albert Einstein the theory of invariants, the invariance of the speed of light is analyzed in depth and from that a set of unexpected phenomenons are derived such as the contraction of length and the dilatation of time for system of coordinates that moves with speeds comparable to the one of the light.

Invariance imply also a mind shift in the case of quantum field theory because in classical physics the equations usually stand first and the invariants observables are derived later, where in modern physics the invariants are usually defined first and the equations are derived later. The two formulations are also shown to be mathematically equivalent through the Noether's theorem, but the two formulations are not not necessarily practically usable in the same way for real computations.

Now what's wrong I don't know, and don't even want to discuss. The current quality of the page is so low that anything else would be better. The astonishing stubborness of crackpotters editing this page is curious. If the level of documentation and references is to be improved fine, please cross edit and add extra infos, if anything is to be corrected fine please go forward but just killing it is ridiculus and damage the image of the people involved in the editing.

This page is not to talk about pseudoscience such as what we see downwards or about discussing CPT, this page is about common established knowledge in the domain of physics that do not need any discussion. People are asked to document themselves first, on who is editing the page before even breathing and shouting that somebody has put crap in their page.

CPT symmetry

What about violations?

Information

Conservation of information: http://www.digitalphilosophy.org/digital_philosophy/11_conservation_of_information.htm

The page you linked to is about "Digital Philosophy", which freely admits to being in conflict with our current understanding of physics. It implies that a law of conservation of information is in conflict with quantum mechanics, which is universally accepted by physicists. Whether you happen to buy into "digital mechanics" or not, the fact remains that this is not mainstream physics, and putting it along side the other conservation laws could mislead someone into thinking otherwise. Also, there's a law of conservation of information proposed by William Dembski, of intelligent design fame, which has been criticized widely and is also not accepted by physicists (indeed, it is considered to contradict the second law of thermodynamics). In theory, there could be a section about "Proposed conservation laws" which includes things not generally accepted (yet?), but I don't see how this guy Ed Fredkin's views are especially noteworthy, or if they've garnered serious attention from anyone. There are plenty of homepages out there who plan to refute all of physics and establish their own new paradigms. Jagan 02:47, 27 February 2006 (UTC)

Jagan is right. I'll remove this from the article. Yevgeny Kats 17:47, 28 February 2006 (UTC)

First of all conservation of information should be mentioned in context of digital physics. And secondly "inteligent design" by Dembski is not (in any way) related to the digital physics by Fredkin.

Dear contributor, digital physics is a speculative hypothesis, which is not an established part of mainstream physics. Therefore its elements should not appear in a general article on physics, in a same list with principles like conservation of energy and momentum. You are encouraged, however, to describe the conservation of information in the article on digital physics if you are familiar with the subject. Yevgeny Kats 22:56, 9 March 2006 (UTC)

Conservation of information is not "Fredkin only" theory. All advanced physicists are claiming conservation of information should rule the universe. 't Hooft, Susskind, Witten, Hawking, to mention just top of the mountain. Go read something about black hole radiation.

The author of the last comment has a point. Ever heard of Hawking radiation? Whether or not information is conserved when matter is swallowed by a black hole is a topic of much debate of late.Kr5t 05:43, 8 March 2007 (UTC)

Susskind cites and uses information conservation all the time in his famous lectures. A particularly explicit, and fascinating, case of its use is the one of the calculation of a black hole temperature from its mass at http://academicearth.org/lectures/modern-physics-statistical-mechanics-5 I think it should be reintroduced as a legitimate physics subject with all the necessary care.Omblauman (talk) 16:06, 5 July 2011 (UTC)

Conservation of Center of Mass motion

Re reversion by Lambiam: the conservation of center of mass motion is not the same as conservation of linear momentum; the first is due to invariance under Lorentz boosts, the second due to invariance under space translations. The difference is important in general relativity, where a "center of mass" cannot be defined in the usual manner. —Preceding unsigned comment added by 81.210.248.125 (talk) 09:22, 14 May 2008 (UTC)

I've read the articles of conservation, regarding classical properties, and the previous discussion comment on mass motion conservation on this conservation law article. LoneRubberDragon (talk) 18:21, 17 September 2008 (UTC)

In the classical domain, the Wiki list of classical macroscopic conservation laws appears incomplete. LoneRubberDragon (talk) 05:51, 17 September 2008 (UTC)

Condensed, your list contains 2 out of 3 classical systems interactions conservation laws, that I recall: LoneRubberDragon (talk) 05:51, 17 September 2008 (UTC)

(1) Conservation of classical system energy / momenta: potential, linear kinetic, angular kinetic, thermal,,

(2) Conservation of classical system matter: charged, neutral, energy equivalent (low energies).

There's a third form of conservation on the classical domain, that is missing from the list: LoneRubberDragon (talk) 05:51, 17 September 2008 (UTC)

(3) Conservation of translation-macroscopic=configuration. LoneRubberDragon (talk) 05:51, 17 September 2008 (UTC)

One can see it in a one dimensional case. Take a stationary non-rotating sealed unit with a mass at one end, and two electromagnetic launchers / catchers at both ends. One end can launch the mass to the other end, that catches it. At this point the sealed unit is stationary in steady state, and translated a distance from its starting position. Then the other end can launch the mass back to the first end. At this point the sealed unit is stationary again, and returned back to the exact original starting position, and original macroscopic configuration equivalent (thermal agitation consuming energy influence is virtually negligible). LoneRubberDragon (talk) 17:58, 17 September 2008 (UTC)

A similar case can be seen in a sealed stationary angular momentum case. Spin accelerating a mass and stopping it, causes the sealed unit frame of reference to spin in the opposite direction. On stopping the spinning mass, the unit also stops spinning. Then reverse spinning the mass to return its frame of reference to the original spatial phase, will also return the sealed unit back to its original frame of angular phase reference, before being brought to a calculated stop. So original angular translation and macroscopic configuration equivalent is restored (thermal agitation consuming energy influence is virtually negligible). LoneRubberDragon (talk) 17:58, 17 September 2008 (UTC)

Another case can be seen in complex classical material motion cases. Take a stationary sealed unit with a fluid. One end launches the fluid to the other end into a catch. Once the fluid has stopped moving the unit is translated and stationary. The other end then launches the fluid back to the first end, into the catch it came from. Once the fluid has stopped moving, the unit is back to its original position, and same macroscopic configuration equivalent (thermal agitation consuming energy influence is virtually negligible). If it did not add back to exactly zero translation and rotation, such a unit could be used to move through an empty vacuum, or spin up an object to any speed, in a sealed unit, which is impossible, because returning back to original configurations, restores the original orientation, supporting the third classical law of conservation. LoneRubberDragon (talk) 17:58, 17 September 2008 (UTC)

As I reckon, starting from a fixed known frame of reference, the path integrals of potential energy to kinetic energy-momenta into thermal energy exchanges, with a cyclic return to its original equivalent configuration, always integrate back to virtually 0, in the linear translation, angular translation, and positional configuration, for macro-meso-micro scale statistically conservative force systems from a starting frame of reference. So it is something more than just a conservation of center of mass, but a centroid of mass and configuration, as the angular and configuration are important, as much as translational parameters of a sealed unit, or a fully-accounted-for closed-system. The initial velocity and angular momentum, when non-zero, add onto the relative motions for that frame of reference. I cannot tell if they add linearly to the frame of reference of the proposed missing third law of conservation to a frame of reference of a configuration form, that I recall, or if the initial frame of reference has special nonlinear differential properties about the angular momentum calculations, to make the third proposed law, non-conservative to that moving initial frame of reference for that sealed unit. My guess is that the third classical conservation law holds for all nonrelativistic initial frames of reference, at the least, and all relativistic frames of reference, at the most, for a sealed unit of some initial configuration, that is returned back to that initial configuration, through closed work paths. LoneRubberDragon (talk) 18:22, 17 September 2008 (UTC)

Now is this actually a conservation law, would be interesting to know, or is it a product of conservation of energy in classical macroscopic materials? And what would be the difference, in the list of conservations, if any but semantics? If it is a product of the integration of macroscopic work paths, what name and subject does it go under? Somewhere around here, among other calculus formulae: LoneRubberDragon (talk) 08:46, 23 September 2008 (UTC)

http://en.wikipedia.org/wiki/Green%27s_theorem

http://en.wikipedia.org/wiki/Divergence_theorem

http://en.wikipedia.org/wiki/Gauss_theorem

http://en.wikipedia.org/wiki/Stokes_theorem

Conservation of mass

Conservation of mass holds at all speeds. Actually, Special Relativity tells us that it's implied by conservation of energy. (in a closed system, of course, but you can't talk about conservation laws in open systems anyway) I allowed myself to fix the article. 94.101.16.12 (talk) 15:44, 25 April 2010 (UTC)

What about the "Conservation of energy" article?

The article "Conservation of energy" did not make it into either of the lists. What list should it be at?George Rodney Maruri Game (talk) 20:43, 9 December 2010 (UTC)

Well, I guess that it is enough to list mass-energy conservation law... George Rodney Maruri Game (talk) 20:25, 24 March 2011 (UTC)

Move reverted.

I have reverted the move of the is article per WP:BRD and WP:TWODABS; having been a practicing attorney with at least a glancing familiarity with environmental law, my experience is that the use of the phrase "conservation law" to refer to the legal concept is exceedingly rare, and is adequately addressed in the hatnote. Cheers! bd2412 T 15:13, 22 April 2014 (UTC)

Use of the term "conservation law" to refer to the legal concept is not rare. Perhaps the hatnote is sufficient. Note that Encyclopedia Brittanca considers the distinction important and chooses their entry as "Conservation law (physics)". For example, here is a sampling of uses of term in the legal sense:

• Conservation Law Center (http://conservationlawcenter.org)
• Conservation Law Foundation (http://www.clf.org)
• Environmental Conservation Law (http://www.dec.ny.gov/regulations/40195.html)
• Conservation Law PC (http://www.conservationlaw.org)
• Conservation Law Clinic (http://law.indiana.edu/students/clinic/conservation.shtml)
• National Association of Conservation Law Chiefs (http://naclec.org)
• BS in Conservation Law Enforcement (http://www.unity.edu/academics/majors/conlaw)
• PA Department of Environmental Protection - Conservation Law :(http://www.portal.state.pa.us/portal/server.pt/community/conservation_law/21703)
• Conservation Law Enforcement (http://www.vinu.edu/content/conservation-law-enforcement)

TheProfessor (talk) 12:39, 23 April 2014 (UTC)

As I said, it is rare in my experience, which has included some exposure to this area. Environmental law is by far the preferred term. In this situation, a hatnote should indeed suffice. bd2412 T 12:41, 23 April 2014 (UTC)

Thanks bd2412. People who work in the field of Conservation (Conservation Biology in particular) often use the term "conservation law" to distinguish environmental laws that address conservation issues (from my experience and published sources). Why do you think Encyclopedia Brittanica editors thought the disambiguation was important? Indeed the hatnote may be sufficient, though I am not convinced. TheProfessor (talk) 12:55, 23 April 2014 (UTC)

Lead serves as summary and introduction

The introduction to this article is a perfect example of what's wrong with Wikipedia technical articles. The intro is supposed to be understandable to general readers. Considering that most of the rest of the article is going to be incomprehensible to the vast majority of readers, who have not studied partial differential equations, they deserved an introduction written in plain English. But no. The introduction has to start with cryptic equations. The conservation equations could easily have been explained in English for general readers, but again, no. What's the fun of that when we can show off the cool buzzwords like quasilinear hyperbolic equation that we copied off the whiteboard last semester in Math 221? --Chetvorno^TALK 21:00, 17 February 2015 (UTC)

Well, the introduction used to be more comprehensible, see the version at 2014-12-17T12:10:33. – Tobias Bergemann (talk) 08:13, 18 February 2015 (UTC)

I went ahead and reworked the lede so it is more comprehensible to a lay person, and moved all the mathematics to one section at the end. That section needs reworking - eliminating the initial redundancy and as appropriate adding a simple description of each equation that is not so dependent upon jargon. Ideally there would be section up front that describes the history and significance of conservation laws. Most of us have some knowledge of conservation laws like conservation of energy and conservation of momentum, but this is not easily recognizable in the article as written, except perhaps those with advanced physics or mathematics degrees. TheProfessor (talk) 16:16, 19 February 2015 (UTC)

That looks a lot better to me. The added overview section, Conservation laws as fundamental laws of nature is also great. However I think the last sentence in the introduction could be expanded to explain what a continuity equation is. --Chetvorno^TALK 19:20, 1 March 2015 (UTC)

I removed the following text from the lede to rework and maybe add in the mathematics section because it is overly technical, not easily understood without advanced education in physics or mathematics:

For example, the conservation of electric charge is expressed by the continuity equation

${\partial \rho \over \partial t}=-\nabla \cdot \mathbf {j} \;$

where $\scriptstyle \rho (\mathbf {x} )\;$ is the density of charge at a point and $\scriptstyle \mathbf {j} (\mathbf {x} )$ is the current density at a point. It says that the rate of increase in the amount of charge at any point is equal to the current of charge flowing into that point minus the current flowing out of the point.

TheProfessor (talk) 15:16, 13 March 2015 (UTC)

Opening section

I have sketched in an opening section, tentatively titled "Conservation laws as fundamental laws of nature". This section needs to be clearly written and comprehensive, based on solid sources, and then summarized in the lead. Here are a couple of online sources that may be useful:

Infoplease:

http://www.infoplease.com/encyclopedia/science/conservation-laws.html

Georgia State University:

http://hyperphysics.phy-astr.gsu.edu/hbase/conser.html

TheProfessor (talk) 16:51, 19 February 2015 (UTC)

Conservation of Mass

In the opening paragraph, it's called an exact law and then immediately after it's called approximate. Which is it? AmazinglyLifelike (talk) 20:44, 13 January 2022 (UTC)

Thanks for noticing that. Since mass can be converted to energy and vice versa, conservation of mass is approximate; the exact conservation law is conservation of ‘mass/energy’ the sum of mass and energy. That is what the “conservation of mass and energy” means in the intro. This is explained in the section on it in the article. Not everything can be fully explained in the introduction --Chetvorno^TALK 21:28, 13 January 2022 (UTC)

Conservation of mechanical energy

I think that in the section titled "Approximate Conservation Laws", the law of mechanical energy should not be listed in the bulleted list of approximate conservation laws. The reason is that it is now known that all of four fundamental forces of nature (gravity, electromagnetism, the strong force, and the weak force) are conservative, i.e. conserve mechanical energy (the sum of kinetic energy and potential energy). Non-fundamental forces like friction only appear to not conserve mechanical energy because microscopic details are neglected. When everything is considered, conservation of mechanical energy is a complete exact conservation law, and is in fact equivalent to the full conservation of energy (which is listed in the section titled "Exact Conservation Laws").

I at first decided to edit this section by removing this conservation law from this section entirely, briefly explaining in the edit summary the reason for this change. However, after I found the change reverted by a User who apparently did not understand nor buy my explanation, I decided to add an additional paragraph to the end of the section clarifying this point about mechanical energy for readers. I have further added a citation at the end of this paragraph to the Feynman Lectures on Physics, where this precise point about the modern view on mechanical energy is explained in detail.

Given this paragraph, I feel it is unnecessary to continue to list "law of mechanical energy" in the above bulleted list. A point has been made by the aforementioned User that this Wikipedia article should address all reasonable viewpoints on this issue of mechanical energy, not single out just one viewpoint from one source (the Feynman Lectures on Physics). However, the "viewpoint" I am mentioning here (namely that there are actually no nonconservative forces, and that mechanical energy is actually fully conserved) is not just "one of several" equally-reasonable viewpoints. Almost all modern physicists are in agreement with this (and there are many more modern texts besides the Feynman Lectures which make this exact same point about mechanical energy), so it should be considered as a fact.

For the above reasons, I am planning to remove the law of mechanical energy" from the bulleted list (I will of course keep the last paragraph about mechanical energy). If any of you still feel like this shouldn't be done, please respond to this, explaining clearly your counterargument. Logic314 (talk) 02:39, 14 November 2022 (UTC)

Logic314 Thanks for raising this matter for discussion. You are proposing some fundamental changes here at Conservation law - changes you have described and explained immediately above. In order for Wikipedia’s information on this subject to remain consistent it will be necessary for the same changes to be incorporated into Mechanical energy and potentially a number of other articles such as:

Conservation of energy

Conservative force

Internal energy

If these changes are to go ahead they will impact a number of articles so it is important that you bring the Physics community along with you. It won’t be sufficient to simply raise these matters here at “Talk:Conservation law”. The appropriate place for such a project is at Wikipedia talk:WikiProject Physics.

Wikipedia consistently defines the mechanical energy of a body to be the sum of the kinetic and potential energies of the body, both measurable quantities. Your description of Feynman’s approach suggests that Feynman is defining it as the sum of these two energies of the body plus some or all of the internal energy of the body and perhaps of a colliding body as well. For example, if a ball with known mechanical energy is released to roll along the ground until friction brings it to a halt, it seems Feynman would say the initial mechanical energy of the ball ultimately becomes an increase in internal energy of the atoms in the vicinity of a great circle on the ball’s surface, and some of the atoms along the ball’s track across the ground. I understand that; but you must agree that these increases in internal energy of certain atoms are not measurable. What Feynman describes as conservation of mechanical energy is what Wikipedia describes as conservation of total energy - the change you are proposing regarding mechanical energy is a change to the terminology but it doesn’t represent a significant change to the knowledge provided in these articles.

The Feynman lectures and the written records of those lectures are aimed at a particular target audience - namely students of Physics at the college level. Wikipedia is aimed at a much broader audience. We must assume that some of those who read our articles on mechanical energy and conservation laws have never taken a formal class in Physics; while others are graduates of college courses in Physics. Our articles must cater for this broad spectrum of readers. Wikipedia:Make technical articles understandable is relevant. Dolphin (t) 06:25, 14 November 2022 (UTC)

This matter is presently open for discussion at Wikipedia talk:WikiProject Physics#Inconsistencies related to mechanical energy. Dolphin (t) 00:53, 1 December 2022 (UTC)

The matter has now been open for discussion at WikiProject Physics for 5 weeks. The consensus is that the paragraph in question should be removed. I will do so. Dolphin (t) 08:35, 27 December 2022 (UTC)

The discussion has now been archived at Wikipedia talk:WikiProject Physics/Archive December 2022#Inconsistencies related to mechanical energy. Dolphin (t) 11:40, 27 January 2023 (UTC)