From: PD on
On Aug 7, 12:04 pm, GSS <gurcharn_san...(a)yahoo.com> wrote:
> On Aug 6, 8:52 pm, Darwin123 <drosen0...(a)yahoo.com> wrote:
>
> > On Jul 10, 12:57 pm, GSS <gurcharn_san...(a)yahoo.com> wrote:
>
> >>  "According to special theory of relativity, all motion is relative
> >> and existence of any privileged or absolute inertial frame of
> >> reference, which could be practically distinguished from all other
> >> inertial frames, is ruled out. However, we may define an absolute or
> >> universal reference frame as the one which is at rest with respect to
> >> the center of mass of the universe and assume the speed c of
> >> propagation of light to be an isotropic universal constant in that
> >> frame.
>
> >  There is not one unique center of mass for the entire universe. GR
> > indicates that the center of mass of the universe doesn't have to be
> > unique even in a finite universe.
>
> GR considers the universe as embedded in 4-D spacetime, which is a
> sort of 4-D 'block' view of the universe. In my opinion, this faulty
> view of the universe has been created by wrongly treating the
> 'spacetime' as a physical entity, instead of recognizing it as a
> mathematical model used for simulating trajectories of particles.
> Basically our dynamic universe is embedded in a 3-D Euclidean space
> and its dynamic behavior or characteristic changes can be represented
> with the use of an independent time coordinate. The notion of center
> of mass can be associated with practically any spatial distribution of
> mass in a 3-D space.
>
>


Actually, GR does quite a bit more than this. The point of GR is that
there IS NO fixed 4D metric, and that in fact, the metric is a
*dynamical* property. Folks in quantum gravity call this feature of GR
"background-free". The geometry is not an independent background upon
which the laws of nature play. The geometry is *governed by* the laws
of physics, which play out on a more fundamental basis.

As for your claim that a center of mass can be associated with
practically any spatial distribution of mass, this is true only if a)
the distribution of mass is finite or b) is asymptotically zero
density.

PD


From: Autymn D. C. on
a minimum
From: GSS on
On Aug 9, 1:22 pm, "Autymn D. C." <lysde...(a)sbcglobal.net> wrote:
> a minimum

Thanks
From: PD on
On Aug 8, 9:12 am, GSS <gurcharn_san...(a)yahoo.com> wrote:
> On Aug 8, 12:36 am, PD <thedraperfam...(a)gmail.com> wrote:
>
>
>
> > On Aug 7, 12:04 pm, GSS <gurcharn_san...(a)yahoo.com> wrote:
>
> >> On Aug 6, 8:52 pm, Darwin123 <drosen0...(a)yahoo.com> wrote:
>
> >>> On Jul 10, 12:57 pm, GSS <gurcharn_san...(a)yahoo.com> wrote:
>
> >>>>  "According to special theory of relativity, all motion is relative
> >>>> and existence of any privileged or absolute inertial frame of
> >>>> reference, which could be practically distinguished from all other
> >>>> inertial frames, is ruled out. However, we may define an absolute or
> >>>> universal reference frame as the one which is at rest with respect to
> >>>> the center of mass of the universe and assume the speed c of
> >>>> propagation of light to be an isotropic universal constant in that
> >>>> frame.
>
> >>>  There is not one unique center of mass for the entire universe. GR
> >>> indicates that the center of mass of the universe doesn't have to be
> >>> unique even in a finite universe.
>
> >> GR considers the universe as embedded in 4-D spacetime, which is a
> >> sort of 4-D 'block' view of the universe. In my opinion, this faulty
> >> view of the universe has been created by wrongly treating the
> >> 'spacetime' as a physical entity, instead of recognizing it as a
> >> mathematical model used for simulating trajectories of particles.
> >> Basically our dynamic universe is embedded in a 3-D Euclidean space
> >> and its dynamic behavior or characteristic changes can be represented
> >> with the use of an independent time coordinate. The notion of center
> >> of mass can be associated with practically any spatial distribution of
> >> mass in a 3-D space.
>
> > Actually, GR does quite a bit more than this.
>
> Yes, GR also creates great fantasies in cosmology.

What fantasies? Have they been shown wrong by direct experimental
counterevidence?

>
> > The point of GR is that
> > there IS NO fixed 4D metric, and that in fact, the metric is a
> > *dynamical* property.
>
> What exactly do you mean by "fixed" metric? Is the metric of spherical
> polar coordinates {g_11 = 1; g_22 = r^2; g_33 = r^2.sin^2(theta)} a
> "fixed" metric?

Yes!

> If so, by what magic wand does GR convert this metric
> into a *dynamical* property?

GR doesn't *convert* anything. Nature does not exhibit a fixed metric,
period. GR is the *discovery* of that observational fact. GR describes
the *relationship* between the *observed* change in the metric and the
presence of energy and matter in the region.

>
> > Folks in quantum gravity call this feature of GR
> > "background-free". The geometry is not an independent background upon
> > which the laws of nature play. The geometry is *governed by* the laws
> > of physics, which play out on a more fundamental basis.
>
> As per GR paradigm or 'belief system', "mass curves spacetime, and
> spacetime tells the mass how to move". Which laws of physics 'tell'
> the mass *how* to 'curve' the spacetime?

Those are the laws that are described by GR.

> And which laws of physics
> 'tell' the spacetime *how* to 'make' mass move on its geodesics?  Is
> there no law of physics which could also 'tell' the charged particles
> to 'learn' how to curve the spacetime?

Such a law might indeed exist, but none yet has been proposed that has
been successful, for a variety of reasons.
There is also good evidence that the laws that govern electrodynamics
are different than the laws that govern gravity.

> Is there no law of physics
> which could force the charged particles also to move on the geodesics
> of curved spacetime? Or is it that GR makes its own laws and tells
> everybody that these are the laws of physics?

No theory MAKES laws of physics. Theories are DISCOVERIES of what the
laws of nature are. Those theories are testable by experiment. If the
experiments pan out, then we have a high level of confidence that our
description actually matches the laws by which nature operates.
From: NoEinstein on
On Aug 6, 7:37 am, "Autymn D. C." <lysde...(a)sbcglobal.net> wrote:
> On Aug 3, 7:59 am, NoEinstein <noeinst...(a)bellsouth.net> wrote:
>
>
>
>
>
> > On Aug 2, 5:04 am, "Autymn D. C." <lysde...(a)sbcglobal.net> wrote:
>
> > > On Aug 1, 4:54 pm, NoEinstein <noeinst...(a)bellsouth.net> wrote:
>
> > > > On Aug 1, 9:27 am, "Autymn D. C." <lysde...(a)sbcglobal.net> wrote:
>
> > > > > On Jul 28, 5:19 pm, NoEinstein <noeinst...(a)bellsouth.net> wrote:
>
> > > > > > On Jul 26, 4:17 am, "Autymn D. C." <lysde...(a)sbcglobal.net> wrote:
>
> > > > > > Dear Aut...:  If I missed an important reply of yours, I'm sorry.
> > > > > > Simply copy and paste it again.  —NE —
>
> > > > > Don't write under my header, fuckwit, and go back in the thread and
> > > > > read it.
>
> > > > Dear Autymn:  You don't have the smarts to be making a '+new post'.
> > > > Sorry if I offend your non-intellect.  — NoEinstein —
>
> > > I made a new post not long ago, and earlier this year.  Stop thwartin
> > > the thread, shyster cretin.  All of your arguments are nothing.
>
> > > -Aut
>
> > Dear Aut....:  And YOUR arguments contributing in any way the science
> > are where?  — NoEinstein
>
> in which?- Hide quoted text -
>
> - Show quoted text -

How about right here on sci.physics, so the readers can see your
shallowness. — NoEinstein —