Talk:Galilean invariance

message: As an amateur, I'm not 100% positive, but special relatively pretty much avoids the subject of gravity, while general relativity extends special relativity to deal with gravity.  IMHO, that sentence should be revised to start: "In general relativity..."
Rhkramer (talk) 14:35, 2 March 2011 (UTC)
thread_title:  "In special relativity ... in a gravitational field." 

message: The lead paragraph reads very nicely until the last sentence:
The fact that the earth on which we stand orbits around the sun at approximately 18 km/s offers a somewhat more dramatic example [of an inertial frame].
The Earth has a gravitational field, is subject to earthquakes, and is orbited by a moon,
so it is not an example of an inertial frame.
Examples of nearly inertial frames in a gravitational field are the Vomit Comet and the International Space Station.  As the article notes later, microgravity is still present in those frames.
:--Jtir 18:58, 23 September 2006 (UTC)
replies: text: The Earth also rotates. The ship example is triply qualified by assuming the ship moves "... at constant speed, without rocking, on a smooth sea...".  Perhaps something similar could be done for the Earth example.--Jtir 17:36, 24 September 2006 (UTC)
replies: text: I'm not sure how relavent this is, since i'm having trouble understanding Newtonian Relativity, the earth does rotate around the sun, as does the International Space Station around the earth, meaning that they are accelerating, as acceleration is not only speed but the direction of motion as well.  So, take that into consideration, whoever understands this better than i.--The Sporadic Update 19:08, 28 September 2006 (UTC)

text: Indeed. The Earth also follows a (nearly) circular orbit.  It has a constant speed of 18 km/s, but is continuously accelerating to follow a curved path; it is an example of a decidedly non-inertial frame.  TenOfAllTrades(talk) 19:27, 3 October 2006 (UTC)
replies: text: I think that what may have been meant originally is that the orbital acceleration is effectively "cancelled" by the gravitational field of the Sun.  The same thing may be said about satellites in Earth orbit. The article needs to help sort this out. --Jtir 19:50, 3 October 2006 (UTC)
thread_title:  examples of inertial frames in the lead paragraph 

message: According to Evans and Starrs<Sup>*</sup>, Galilean invariance will not hold for certain configurations of matter.
— DIV (128.250.204.118 03:17, 18 June 2007 (UTC)
thread_title:  Torpid matter 

message: The section of the article called "Formulation" shows that acceleration (presumably) as a scalar is invariant under a Galilean change of coordinates.  If this proves Newton's laws hold, it would be useful to explain why.  If we express acceleration as vector and change coordinates, the scalars of the vector do change.  So is the invariance of acceleration as a vector (direction and magnitude) the significant fact?
Given any mathematical expression in scalar coordinates, one can create a new expression by doing a coordinate transformation.  Elementary physics texts often state what physical laws apply in some standard coordinate system and then assert that they remain valid under a change of coordinates. This approach is not using anything about "invariance" to establish physics.  Presumably, the point of Galilean invariance is select expressions that describe physical laws and reject others.  The article needs more explanation of what criteria are used.  For example, how does the invariance of 'a' select the law F = Ma and reject the law F = Ma^2 ?  Or is Galilean invariance inadequate to completely determine physical laws?
Tashiro (talk) 18:00, 16 August 2009 (UTC)
replies: text: All quantities in the formulation section are vectors, or, to be more precise, coordinate triplets. This is expressed by the phrase "A physical event in S will have position coordinates r = (x, y, z) and time t". DVdm (talk) 13:00, 17 August 2009 (UTC)

text: On this topic we have invariant (physics) which is more general. For physical science refer to Galilean equivalence; the current article here is more in the direction of invariant (mathematics) where there is a view of mathematical structures that express the intuition of Galileo's relativity. As for the "Formulation", I would prefer a phrasing admitting the title absolute space and time of the supporting article.Rgdboer (talk) 21:26, 18 August 2009 (UTC)
thread_title: What exactly is the section "Formulation" claiming to show ?

message: I don't understand why this article about Galilean invariance is turning into a page more about relativity than anything else. I suggest we link to relativity as much as needed, and keep the article neat and clean.  —Preceding unsigned comment added by 95.34.181.62 (talk) 13:42, 15 May 2010 (UTC)
thread_title:  Why is this turning into an article about relativity? 

message: How does the invariance of acceleration under Galilean transformations (together with the invariance of mass) imply Galilean invariance? For this implication to be valid, you would need to show that the full law of motion (Newtons II law, F = ma) is invariant under Galilean transformations (at least for isolated systems). That a' = a is not a physical principle but an elementary mathematical fact, that will also hold in special relativity (under a formal Galilean transformation). The reason, why Galilean invariance is only an approximate symmetry of nature, is that F' != F when electromagnetic interactions (of moving charges) are considered. --Hardi27 (talk) 22:00, 2 September 2012 (UTC)
thread_title:  Invariance of acceleration and Galilean invariance 

message: One of these days, I'll stumble on a Wikipedia article written by someone who actually is proficient in English; one of these days."The fact that the Earth orbits around the sun at approximately 30 km/s offers a somewhat more dramatic example, and it is technically an inertial reference frame." The fact offers? Perhaps 'provides' would be better. The "fact" is not an inertial frame (the "it" here has changed the subject, sigh). At ANY one instant, the Earth is accelerating that is: |d²xi/dt²| is almost never zero (for i=1,2,3). It is in 'free fall', but free fall is not the same as non-accelerating.173.189.74.162 (talk) 22:15, 11 April 2015 (UTC)
replies: text: I've  the  which incorrectly asserted that the rotating reference frame was inertial.  I leave improvement of the English to you. -- ToE 12:17, 3 May 2015 (UTC)
thread_title:  Wrong 

message: The article says an essential difference between Newton's and Einstein's versions of Relativity is that, in Newton's version, relative motion is embedded in absolute space while in Einstein's version it is not. This only happened because Newton admitted the necessity for absolute space to explain centrifugal force in rotational motion - a problem totally ignored by Einstein in his Special Theory (although Poincare did not ignore it). Otherwise Newton's statement of the Principle of Relativity for mechanical motion in Principia (see Corollary V) is essentially the same as Einstein's. JFB80 (talk) 15:18, 11 April 2018 (UTC)
thread_title:  Newton's vs Einstein's Principal of Relativity 

message: I see here that in 1615 the moving ship idea is already used by Foscarini.  Making the 1632 reference late even if it has the right author.  "His final argument was a rebuttal of an analogy that Foscarini had made between a moving Earth and a ship on which the passengers perceive themselves as apparently stationary and the receding shore as apparently moving." (Galileo affair)  Elegast (talk) 08:06, 10 July 2019 (UTC)
thread_title:  Earlier references 

message: Hi,
Frequently a clause or sentence containing the pronoun it is easier to read without it.  Here are some examples.
> "compressing their joints, making it difficult to extend their limbs in any direction perpendicular to the gravity field of the star"
versus
compressing their joints, making extension of their limbs in any direction perpendicular to the gravity field of the star difficult"
> "It is not possible to have a consistent Galilean transformation that transforms both the magnetic and electric fields."
versus
No consistent Galilean transformation can transform both the magnetic and electric fields.
> "Due to Newton's law of reciprocal actions there is a reaction force; it does work depending on the inertial frame of reference in an opposite way."
versus
Due to Newton's law of reciprocal actions there is a reaction force which does work, depending on the inertial frame of reference in an opposite way.
Regards, ... PeterEasthope (talk) 21:41, 16 March 2023 (UTC)
replies: text: Go ahead, thus, as if it were, make it so.  That is, otherwisely, to say it differently, to boldly edit copy as required to succinctify the textual payload of the article as necessity, for all intents and purposes, absent the naysay of others, for erudite progress.  Cheers.  . Constant314 (talk) 22:28, 16 March 2023 (UTC)
thread_title:  it