Talk:2904: Physics vs. Magic - Revision history

172.71.30.193: /* Arguably, it is magic */ new section

2024-05-20T01:07:09Z

‎Arguably, it is magic: new section

172.68.144.147 at 12:20, 25 March 2024

2024-03-25T12:20:23Z

Cleonis: Addressing the question of how to implement a numerical statonary action solver

2024-03-17T10:04:58Z

Addressing the question of how to implement a numerical statonary action solver

172.71.242.29 at 21:58, 15 March 2024

2024-03-15T21:58:48Z

172.70.91.61: Plea for more layman's terms

2024-03-15T20:03:42Z

Plea for more layman's terms

172.70.86.189 at 17:50, 14 March 2024

2024-03-14T17:50:57Z

Cleonis: Added derivation for the case where the initial velocity is non-zero

2024-03-12T23:09:08Z

Added derivation for the case where the initial velocity is non-zero

Danger Kitty at 13:21, 12 March 2024

2024-03-12T13:21:47Z

Danger Kitty at 13:19, 12 March 2024

2024-03-12T13:19:43Z

172.71.242.219 at 13:51, 11 March 2024

2024-03-11T13:51:42Z

← Older revision		Revision as of 01:07, 20 May 2024
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	No comment on the "falls out of" terminology for the Lagrangian? It's been yonks since I learnt anything to do with Lagrangians, and I can't say I ever mastered them, but I remember the solution "falling out of" the equations being a feature. [[Special:Contributions/172.68.144.147\|172.68.144.147]] 12:20, 25 March 2024 (UTC)		No comment on the "falls out of" terminology for the Lagrangian? It's been yonks since I learnt anything to do with Lagrangians, and I can't say I ever mastered them, but I remember the solution "falling out of" the equations being a feature. [[Special:Contributions/172.68.144.147\|172.68.144.147]] 12:20, 25 March 2024 (UTC)
		+
		+	== Arguably, it is magic ==
		+
		+	I don't know if this has a place in the explainer body, but this piece https://arxiv.org/abs/1101.5056 nearly argues that it ''is'' magic (as well as providing a summary of historic attempts to violate it.)
		+
		+	“in the present paper we try to argue that we have not yet any truly cogent argument (known fundamental physical laws) to exclude its possible macroscopic violation. Even Landauer's information-theoretic principle seems to fall short of the initial expectations of being the fundamental `physical' reason of all Maxwell's demons failure.”
		+
		+	[[Special:Contributions/172.71.30.193\|172.71.30.193]] 01:07, 20 May 2024 (UTC)

← Older revision		Revision as of 12:20, 25 March 2024
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	I feel like this explanation needs a Simple English rewrite. The introduction is ok, but I came here with the simple question "What are Lagrangians?" and the sci-speak is so opaque it might as well be just "magic". [[Special:Contributions/172.70.91.61\|172.70.91.61]] 20:03, 15 March 2024 (UTC)		I feel like this explanation needs a Simple English rewrite. The introduction is ok, but I came here with the simple question "What are Lagrangians?" and the sci-speak is so opaque it might as well be just "magic". [[Special:Contributions/172.70.91.61\|172.70.91.61]] 20:03, 15 March 2024 (UTC)
	:Langrangian: [https://darthsanddroids.net/episodes/0003.html a kind of sofa with a double cup-holder...] ;) [[Special:Contributions/172.71.242.29\|172.71.242.29]] 21:58, 15 March 2024 (UTC)		:Langrangian: [https://darthsanddroids.net/episodes/0003.html a kind of sofa with a double cup-holder...] ;) [[Special:Contributions/172.71.242.29\|172.71.242.29]] 21:58, 15 March 2024 (UTC)
		+
		+	No comment on the "falls out of" terminology for the Lagrangian? It's been yonks since I learnt anything to do with Lagrangians, and I can't say I ever mastered them, but I remember the solution "falling out of" the equations being a feature. [[Special:Contributions/172.68.144.147\|172.68.144.147]] 12:20, 25 March 2024 (UTC)

@@ Line 128: / Line 128: @@
 Probably not the clearest way to put that I suppose, but while the Euler-Lagrange equations might not take initial and final states as inputs, the least action principle from which they are derived is formalised that way, at least insofar as it takes the generalized coordinates at each end of an interval and gives a rule for the evolution between them. The fact that in practice you usually grind the Lagrangian into ELEs in order to solve it doesn't mean that there's anything stopping you doing it directly by, say, discretizing the interval to turn the action integral into a form you can minimize directly. I still think that the least-action principle from classical mechanics makes much more sense as the root for this joke than their use specifically in particle physics. [[Special:Contributions/172.70.86.189|172.70.86.189]] 17:50, 14 March 2024 (UTC)
 I feel like this explanation needs a Simple English rewrite. The introduction is ok, but I came here with the simple question "What are Lagrangians?" and the sci-speak is so opaque it might as well be just "magic". [[Special:Contributions/172.70.91.61|172.70.91.61]] 20:03, 15 March 2024 (UTC)
 :Langrangian: [https://darthsanddroids.net/episodes/0003.html a kind of sofa with a double cup-holder...] ;) [[Special:Contributions/172.71.242.29|172.71.242.29]] 21:58, 15 March 2024 (UTC)

← Older revision		Revision as of 21:58, 15 March 2024
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	I feel like this explanation needs a Simple English rewrite. The introduction is ok, but I came here with the simple question "What are Lagrangians?" and the sci-speak is so opaque it might as well be just "magic". [[Special:Contributions/172.70.91.61\|172.70.91.61]] 20:03, 15 March 2024 (UTC)		I feel like this explanation needs a Simple English rewrite. The introduction is ok, but I came here with the simple question "What are Lagrangians?" and the sci-speak is so opaque it might as well be just "magic". [[Special:Contributions/172.70.91.61\|172.70.91.61]] 20:03, 15 March 2024 (UTC)
		+	:Langrangian: [https://darthsanddroids.net/episodes/0003.html a kind of sofa with a double cup-holder...] ;) [[Special:Contributions/172.71.242.29\|172.71.242.29]] 21:58, 15 March 2024 (UTC)

← Older revision		Revision as of 20:03, 15 March 2024
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	Probably not the clearest way to put that I suppose, but while the Euler-Lagrange equations might not take initial and final states as inputs, the least action principle from which they are derived is formalised that way, at least insofar as it takes the generalized coordinates at each end of an interval and gives a rule for the evolution between them. The fact that in practice you usually grind the Lagrangian into ELEs in order to solve it doesn't mean that there's anything stopping you doing it directly by, say, discretizing the interval to turn the action integral into a form you can minimize directly. I still think that the least-action principle from classical mechanics makes much more sense as the root for this joke than their use specifically in particle physics. [[Special:Contributions/172.70.86.189\|172.70.86.189]] 17:50, 14 March 2024 (UTC)		Probably not the clearest way to put that I suppose, but while the Euler-Lagrange equations might not take initial and final states as inputs, the least action principle from which they are derived is formalised that way, at least insofar as it takes the generalized coordinates at each end of an interval and gives a rule for the evolution between them. The fact that in practice you usually grind the Lagrangian into ELEs in order to solve it doesn't mean that there's anything stopping you doing it directly by, say, discretizing the interval to turn the action integral into a form you can minimize directly. I still think that the least-action principle from classical mechanics makes much more sense as the root for this joke than their use specifically in particle physics. [[Special:Contributions/172.70.86.189\|172.70.86.189]] 17:50, 14 March 2024 (UTC)
		+
		+	I feel like this explanation needs a Simple English rewrite. The introduction is ok, but I came here with the simple question "What are Lagrangians?" and the sci-speak is so opaque it might as well be just "magic". [[Special:Contributions/172.70.91.61\|172.70.91.61]] 20:03, 15 March 2024 (UTC)

← Older revision		Revision as of 17:50, 14 March 2024
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	Conservation laws and Lagrangian refer to their role in particle physics. For example, conservation of electrical charge is simply postulated as something that your theory should satisfy, but physics does not tell us why it is there in the first place (hence: magic). Similarly, Lagrangians are usually formulated in a way that the outcomes are compatible with experimental observations and not starting out based on fundamental principles. The statement "Lagrangian mechanics instead takes the initial and final states of a system as inputs" is wrong by the way. The Euler-Lagrange equation yields a differential equation that is usually solved as an initial value problem, as it is done in Newtonian mechanics. {{unsigned ip\|172.70.110.144\|07:38, 11 March 2024}}		Conservation laws and Lagrangian refer to their role in particle physics. For example, conservation of electrical charge is simply postulated as something that your theory should satisfy, but physics does not tell us why it is there in the first place (hence: magic). Similarly, Lagrangians are usually formulated in a way that the outcomes are compatible with experimental observations and not starting out based on fundamental principles. The statement "Lagrangian mechanics instead takes the initial and final states of a system as inputs" is wrong by the way. The Euler-Lagrange equation yields a differential equation that is usually solved as an initial value problem, as it is done in Newtonian mechanics. {{unsigned ip\|172.70.110.144\|07:38, 11 March 2024}}
		+
		+	Probably not the clearest way to put that I suppose, but while the Euler-Lagrange equations might not take initial and final states as inputs, the least action principle from which they are derived is formalised that way, at least insofar as it takes the generalized coordinates at each end of an interval and gives a rule for the evolution between them. The fact that in practice you usually grind the Lagrangian into ELEs in order to solve it doesn't mean that there's anything stopping you doing it directly by, say, discretizing the interval to turn the action integral into a form you can minimize directly. I still think that the least-action principle from classical mechanics makes much more sense as the root for this joke than their use specifically in particle physics. [[Special:Contributions/172.70.86.189\|172.70.86.189]] 17:50, 14 March 2024 (UTC)

@@ Line 72: / Line 72: @@
 The relation (5) is known as Torricelli's formula. <br>
-In case the initial position coordinate and the initial velocity are non-zero:
+In case the initial position coordinate and the initial velocity are non-zero the derivation works out as follows: <br>
-a(s-s&#8320;)&nbsp;=&nbsp;&frac12;v&sup2;&nbsp;-&nbsp;&frac12;(v&#8320;)&sup2;&nbsp;&nbsp;&nbsp;&nbsp;(6)
+Next we go to the more general case of allowing non-uniform acceleration. Interestingly, the result of the integration is identical to (12).
-Interestingly, in the case of a non-uniform acceleration the result of the integration is identical to  (6)
+&int;&nbsp;a&nbsp;ds&nbsp;=&nbsp;&frac12;v&sup2;&nbsp;-&nbsp;&frac12;(v&#8320;)&sup2;&nbsp;&nbsp;&nbsp;&nbsp;(13)
-&int;&nbsp;a&nbsp;ds&nbsp;=&nbsp;&frac12;v&sup2;&nbsp;-&nbsp;&frac12;(v&#8320;)&sup2;&nbsp;&nbsp;&nbsp;&nbsp;(7)
+(To understand (13): we have that integration is summation of infinitesimal strips. The integration consists of concatenating instances of (12), in the limit of infinitesimal increments. All of the in-between terms drop away against each other, resulting in (13))
 <br>
@@ Line 86: / Line 92: @@
 The work-energy theorem is obtained as follows: start with ''F''=''ma'', and integrate both sides with respect to the position coordinate.
-&int;&nbsp;F&nbsp;ds&nbsp;=&nbsp;&int;&nbsp;ma&nbsp;ds&nbsp;&nbsp;&nbsp;&nbsp;(8)
+&int;&nbsp;F&nbsp;ds&nbsp;=&nbsp;&int;&nbsp;ma&nbsp;ds&nbsp;&nbsp;&nbsp;&nbsp;(14)
-Use (7) to process the right hand side:
+Use (13) to process the right hand side:
-&int;&nbsp;F&nbsp;ds&nbsp;=&nbsp;&frac12;mv&sup2;&nbsp;-&nbsp;&frac12;m(v&#8320;)&sup2;&nbsp;&nbsp;&nbsp;&nbsp;(9)
+&int;&nbsp;F&nbsp;ds&nbsp;=&nbsp;&frac12;mv&sup2;&nbsp;-&nbsp;&frac12;m(v&#8320;)&sup2;&nbsp;&nbsp;&nbsp;&nbsp;(15)
-(9) is the work-energy theorem
+(15) is the work-energy theorem
 The work-energy theorem is the reason that it is useful to formulate the concepts of potential energy and kinetic energy. If we formulate potential energy and kinetic energy in accordance with the work-energy theorem then we have that the sum of potential energy and kinetic energy is a conserved quantity.
-The work-energy theorem consists of two elements: ''F''=''ma'', and (7).
+The work-energy theorem consists of two elements: ''F''=''ma'', and (13).
-Here (7) was stated in terms of the familiar quantities of mechanics: position, velocity, acceleration. (7) generalizes to any set of three quantites that features that cascading relation: state, first time derivative, second time derivative.
+Here (13) was stated in terms of the familiar quantities of mechanics: position, velocity, acceleration. (13) generalizes to any set of three quantites that features that cascading relation: state, first time derivative, second time derivative.
 Example: electric current and electromotive force in an LC circuit<br>

← Older revision		Revision as of 13:21, 12 March 2024
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	This is why statistics is magical [[User:Phlaxyr\|Phlaxyr]] ([[User talk:Phlaxyr\|talk]]) 23:33, 8 March 2024 (UTC)		This is why statistics is magical [[User:Phlaxyr\|Phlaxyr]] ([[User talk:Phlaxyr\|talk]]) 23:33, 8 March 2024 (UTC)

−	~~I think this page is complete, I'm going to remove the incomplete tag.[[User:Danger Kitty\|Danger Kitty]] ([[User talk:Danger Kitty\|talk]])~~

	Both thermodynamics and conservation laws make predictions without telling us anything about what exactly is happening in the intermediate steps. In that sense they're no different from the curse in the comic. An example for thermodynamics could be: your coffee cup will get cold if left on your desk (zeroth law). And an example from conservation laws could be: it doesn't matter what method you're going to use to stop a moving car, in all cases the car has lost the same amount of energy (1/2mv^2). [[Special:Contributions/141.101.99.110\|141.101.99.110]] 00:33, 9 March 2024 (UTC)		Both thermodynamics and conservation laws make predictions without telling us anything about what exactly is happening in the intermediate steps. In that sense they're no different from the curse in the comic. An example for thermodynamics could be: your coffee cup will get cold if left on your desk (zeroth law). And an example from conservation laws could be: it doesn't matter what method you're going to use to stop a moving car, in all cases the car has lost the same amount of energy (1/2mv^2). [[Special:Contributions/141.101.99.110\|141.101.99.110]] 00:33, 9 March 2024 (UTC)

← Older revision		Revision as of 13:19, 12 March 2024
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	This is why statistics is magical [[User:Phlaxyr\|Phlaxyr]] ([[User talk:Phlaxyr\|talk]]) 23:33, 8 March 2024 (UTC)		This is why statistics is magical [[User:Phlaxyr\|Phlaxyr]] ([[User talk:Phlaxyr\|talk]]) 23:33, 8 March 2024 (UTC)

		+	I think this page is complete, I'm going to remove the incomplete tag.[[User:Danger Kitty\|Danger Kitty]] ([[User talk:Danger Kitty\|talk]])

	Both thermodynamics and conservation laws make predictions without telling us anything about what exactly is happening in the intermediate steps. In that sense they're no different from the curse in the comic. An example for thermodynamics could be: your coffee cup will get cold if left on your desk (zeroth law). And an example from conservation laws could be: it doesn't matter what method you're going to use to stop a moving car, in all cases the car has lost the same amount of energy (1/2mv^2). [[Special:Contributions/141.101.99.110\|141.101.99.110]] 00:33, 9 March 2024 (UTC)		Both thermodynamics and conservation laws make predictions without telling us anything about what exactly is happening in the intermediate steps. In that sense they're no different from the curse in the comic. An example for thermodynamics could be: your coffee cup will get cold if left on your desk (zeroth law). And an example from conservation laws could be: it doesn't matter what method you're going to use to stop a moving car, in all cases the car has lost the same amount of energy (1/2mv^2). [[Special:Contributions/141.101.99.110\|141.101.99.110]] 00:33, 9 March 2024 (UTC)

← Older revision		Revision as of 13:51, 11 March 2024
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	We haven't seen anything about daylight savings time yet... maybe we'll see one tomorrow... why am i eepy during the middle of the day... -- megan <sup>she</sup>/<sub>her</sub> <sup>[[user talk:megan\|talk]]</sup>/<sub>[[special:contribs/megan\|contribs]]</sub> 23:01, 10 March 2024 (UTC)		We haven't seen anything about daylight savings time yet... maybe we'll see one tomorrow... why am i eepy during the middle of the day... -- megan <sup>she</sup>/<sub>her</sub> <sup>[[user talk:megan\|talk]]</sup>/<sub>[[special:contribs/megan\|contribs]]</sub> 23:01, 10 March 2024 (UTC)

−	Conservation laws and Lagrangian refer to their role in particle physics. For example, conservation of electrical charge is simply postulated as something that your theory should satisfy, but physics does not tell us why it is there in the first place (hence: magic). Similarly, Lagrangians are usually formulated in a way that the outcomes are compatible with experimental observations and not starting out based on fundamental principles. The statement "Lagrangian mechanics instead takes the initial and final states of a system as inputs" is wrong by the way. The Euler-Lagrange equation yields a differential equation that is usually solved as an initial value problem, as it is done in Newtonian mechanics.	+	Conservation laws and Lagrangian refer to their role in particle physics. For example, conservation of electrical charge is simply postulated as something that your theory should satisfy, but physics does not tell us why it is there in the first place (hence: magic). Similarly, Lagrangians are usually formulated in a way that the outcomes are compatible with experimental observations and not starting out based on fundamental principles. The statement "Lagrangian mechanics instead takes the initial and final states of a system as inputs" is wrong by the way. The Euler-Lagrange equation yields a differential equation that is usually solved as an initial value problem, as it is done in Newtonian mechanics. {{unsigned ip\|172.70.110.144\|07:38, 11 March 2024}}