Re: GR ?


"Bill Hobba" <bhobba@xxxxxxxxxxxxxx> wrote in message
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| > snip
| >
| > Bill Hobba wrote :-
| > | Lagrangeians as a concept are independent of geometry. It is like
| asking
| > is
| > | wave function collapse dependant on Euclidian geometry or indeed is
red
| > | dependant on Pythagoras's theorem - the concepts do not overlap.
| >
| > From your link it seemed to be describing a langrange as a tool for
| > describing the of the operation of a pendulem or similair, this seems to
| > contradict the statement that you just made. For example how would a
| > langrange be applied to a pendulem as part of an object that had been
| > length contracted to a disc by velocity assuming that its contraction
was
| a
| > real effect and not just observational distortions as Tom seems to be
| > claiming at the moment.?
|
| First you are misreading what Tom said. Length contraction is simply a
| result of space-time geometry similar to rotating a rod and its projection
| onto the x axis changes - such is the effect of geometry - not
observational
| distortion.

Observations that obscure the real measurement of an object by incorrectly
compensating for geometric perspective deserve to be stuck in the bin of
obscurity and not brought out by supposedly intelligent beings to try and
prove some personal fantasy.

| Now insofar as I can make sense of your question you seem to be
| asking how a lagrangeian would be applied to a pendulum attached to a
| rotating disk

No the disc that I was referring to was a disc presented by some accelerator
group that purported to be the view of a spherical object under near c
velocity and was offered as proof of length contraction.

| when considering the problem relativistically. The answer is
| the same way as any other problem - the PLA guarantees a lagrangeian must
| exist for the system; although in this case it looks rather difficult to
| figure out what it is.
|
| >
| > |
| > | >
| > | > | I have given you a link to what lagrangains are the PLA is about.
| The
| > | > | key physical fact that allows the modern definition of energy to
be
| > | > | applicable is that all our current theories can be formulated as
| > | > | lagrangains. That is what allows us to use the modern definition.
| As
| > | to
| > | > | why this is and why it is so important see
| > | > | http://www.eftaylor.com/leastaction.html.
| > | >
| > | > I am looking at this link and hopefully it will explain your
position
| > and
| > | > confidence in lagrangains' Yes it does seem so to a degree but it
| seems
| > to
| > | > fail to address energy as a function of curvature which was the
point
| of
| > | my
| > | > original post.
| > |
| > | Where do you get the idea from what I or Tom has said that energy is a
| > | function of curvature?
| >
| > You may not have but that was the implied query in the original post,
are
| > you saying that you don't agree that energy is a function of curvature ?
|
| You are obviously not reading carefully enough. Many times in this post
it
| has been said that it is not possible to come up with a meaningful
| definition of energy in GR ie when space-time curvature is present.

Well perhaps somebody needs to try harder.

| The
| implication is obvious but to spell it out we can not in general say if
| space-time curvature has energy or not hence we can not say if energy is a
| function of curvature or not.
|
| > As I remember it you have said curvature is a function of energy ?
|
| Then you remember incorrectly - I did not say that.

I sit corrected then {:-)

|
| >
| > |
| > | > It seems more concerned with conserving energy by a
| > | > description of the path a particle will take than defining the
energy
| of
| > | the
| > | > particle which again was the point of my original post which you
| perhaps
| > | > missed?
| > |
| > | It is a brief introduction to the importance of lagrangeians. It
| examines
| > | lagrangeians from a number of different perspectives. But as a matter
| of
| > | principle lagrangeians exist because of QM - and the article makes
this
| > | abundantly clear. Think about the Feynman sum over histories
approach.
| > | Consider the little arrow as a phasor A*e^i*s*t. For all phasors
except
| > one
| > | case it will be cancelled by the phasor of a nearby path - that one
case
| > is
| > | where the s over that path does not differ from the S over the other
| path.
| > | A rather simple argument implies that in the classical limit S must
obey
| > the
| > | principle of least action.
| >
| > I have not been able to trace that section but your
description\definition
| > of energy has now become so imbedded and dependent on the near totality
of
| > established physics that its virtually impossible to debate in any
single
| > life time so for the time being I must give your complexity the medal of
| > being not readily understandable by me and the winner on that score {:-)
|
| Most people when they discover Noethers theorem are impressed by its
beauty
| and far reaching consequences. The reason you have the above reaction is
| you probably do no understand it. Indeed the misconceptions posted above
| makes that almost a dead certainty.


Neither you or Tom have been able to clearly explain why you believe that
langrange which Noether is based on applies to fields. In fact Tom seems to
have categorically denied that they have anything to do with fields. Which
rather leaves your definition of " energy is the conserved Noether charge
related to time symmetry of the lagrangian " without support and is probably
the decaying (rubbish) word salad it sounded like.{:-)

|
| Bill
|
| > Thanks for your view and I will study it over the next few thousand
years
| > {:-) and may return with a comment then but I don't think your
definition
| of
| > energy will catch on amongst the interested thinking masses, perhaps
being
| > rather elite's and specialist IMHO{:-). I have made comment below that
you
| > might like to reply to as I would be interested in your views.
| >
| > |
| > | > An interesting link to your position Bill thanks and I may explore
| > | > it more thoroughly if needed.
| > | >
| > | > |
| > | > | > If you can show me that lagrangeians are applicable to GR
geometry
| > | then
| > | > I
| > | > | > will be very interested.
| > | > | >
| > | > |
| > | > | See chapter 4 of the following - in particular the section
starting
| at
| > | > | equation 4.54 where the EFE's are derived using the PLA and the
| > | existence
| > | > of
| > | > | a lagrangian:
| > | > | http://nedwww.ipac.caltech.edu/level5/March01/Carroll3/frames.html
| > | > |
| > | >
| > | > I expect this may be the difference in our views, you think that
| energy
| > | > creates curvature, which I don't disagree with.
| > | > But I also think that curvature creates energy which I don't think
you
| > | agree
| > | > with ?
| > |
| > | That is the problem. It is generally not possible to find an
expression
| > for
| > | energy in GR that is covariant - the best that can be done is what is
| > called
| > | a pseudo tensor
| > | http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html
| >
| > I think that this was the direction my original post was about but that
| link
| > does not seem a solution that I would be happy with at the moment.
| >
| > |
| > | > My view is not formalised yet. The question then might be did
| > | > curvature come before energy or did energy come before curvature ?
| > |
| > | GR says stress energy tensor over here - curvature over there -
nothing
| > | about what causes what.
| >
| > Would you agree with this expansion to that statement. Energy as
particals
| > over here described by stress energy tensor, curvature over there
| described
| > by GR. ?
| > Perhaps GR missed out the bit that said, enough curvature here -
particle
| > here. ?
| >
| > |
| > | > In other words the particles that lagrangeians use
| > |
| > | You have a misconception right here - lagrangeians apply not just to
| > | particles but to fields as well.
| >
| > Do I ?, T = kinetic energy. How do you define the kinetic energy of a
| field
| > as a property of that field?
| >
| > |
| > | Bill
| > snip
| > --
| > Significant Zero E-field = Electric field, M-field =Magnetic field,
two
| > unbound field effects
| > http://home.freeuk.com/paulps/
| > Maybe updates. (1-(1/(1/3))^2)/(1 + (1/(1/3))^2) = - 0.08 = FTL ? -p<+p
| or
| > (m*-v)<(m*+v) or (m*-c^2)<(m*+c^2) =g?
| >
| >
| >
|
|


.

Relevant Pages

  • Re: GR ?
    ... > | modern definition of energy as the conserved Noether charge related to ... > fail to address energy as a function of curvature which was the point of ... It is a brief introduction to the importance of lagrangeians. ... > | the definitions standard in physics. ...
    (sci.physics.relativity)
  • Re: GR ?
    ... >> length contracted to a disc by velocity assuming that its contraction was ... frame are linked to the pendulum, ... >> you saying that you don't agree that energy is a function of curvature? ...
    (sci.physics.relativity)
  • Re: GR ?
    ... > Bill Hobba wrote:- ... > |> fail to address energy as a function of curvature which was the point ... > | It is a brief introduction to the importance of lagrangeians. ...
    (sci.physics.relativity)
  • Re: GR ?
    ... |> | key physical fact that allows the modern definition of energy to be ... | function of curvature? ... |> particle which again was the point of my original post which you perhaps ... | It is a brief introduction to the importance of lagrangeians. ...
    (sci.physics.relativity)
  • Re: the quantization of gravity
    ... | again then the curvature of space-time will decrease. ...
    (sci.physics.relativity)
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