Re: Is 'time' time or is it not.

> >> There is no gravity in that example. There is no space-time curvature,
> >> only flat Minkowski space-time.
> >
> > When acceleration is involved it is not flat any more especially for
> > non negligible relativistic effect and should be treated by GR.
>
> Ok, now you'd have to say what you mean by "flat". Here's what I mean.
> Given any space-time metric, we can calculate its Riemann curvature
> tensor. If it is zero, then we say that the space-time is flat. This
> exactly what happens in Minkowski space.

There is no absolute space-time scene there is only space time of
observer which is formed by acceleration and by gravity. The observer
mass is irrelevant it only should be non zero. The microwave radiation
mapping showed that our universe (I mean universe from point of view of
observer) is quite flat - actually suspiciously flat it supports the
inflationary prospect about casually separated domains (relatively
observer) of enormously bigger structure and "flatness" of earth is
a good analogy to describe "flatness" of universe.

> One example is a space ship with a set of rocket engines. Acceleration
> can also refer to a coordinate system defined by an observer that is
> accelerating. None of which, changes the fact that we are still in
> Minkowski space-time, which is flat.

It is wrong, there is no undependable on observer space-time, there is
no absolute scene, there is no absolute reference frame, so statement
"the fact that we are still in Minkowski space-time, which is flat"
makes no sense since the observer space time curvature establishes
space-casual relation with another observers only in context of
observer reference frame.

My expertise in this area is just recall of my university time 20 years
ago, so technical details now is out of my grasp but I did spent a lot
time then trying to understand meaning of GR math.

Regards,
Stefan


Igor Khavkine wrote:
> On 2005-09-08, stefanbanev@xxxxxxxxx <stefanbanev@xxxxxxxxx> wrote:
> > Hi Igor,
> >
> >> There is no gravity in that example. There is no space-time curvature,
> >> only flat Minkowski space-time.
> >
> > When acceleration is involved it is not flat any more especially for
> > non negligible relativistic effect and should be treated by GR.
>
> Ok, now you'd have to say what you mean by "flat". Here's what I mean.
> Given any space-time metric, we can calculate its Riemann curvature
> tensor. If it is zero, then we say that the space-time is flat. This
> exactly what happens in Minkowski space.
>
> Acceleration refers to the curvature of the world line of an observer.
> One example is a space ship with a set of rocket engines. Acceleration
> can also refer to a coordinate system defined by an observer that is
> accelerating. None of which, changes the fact that we are still in
> Minkowski space-time, which is flat.
>
> > SR
> > guaranties that observer's clock is the fastest one in the universe
> > of the flat space time - in the universe of inertial systems. TP
> > arrangement is possible only if acceleration is allowed and the
> > acceleration is the only source of asymmetry so if time dilation in TP
> > experiment is not negligible the space time curvature is not negligible
> > as well and must be treated by GR.
>
> Again, acceleration does not imply curvature. If the space ship has
> small mass (or rather small density, since it's an extended object),
> gravity and curvature can be very well neglected.
>
> Igor

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