Re: Is the LT for time correct?

On Nov 30, 11:45 pm, xray4abc <lemhen...@xxxxxxxx> wrote:
When comparing the length of an object from 2
different IRFs, one must refer to the endpoints
of the object as locatable simultaneously.
In fact, it seems that, this can be done only in
one IRF at a time, i.e. in the frame where the
object is not moving.
For the moving frame we can not attach a
certain time value to the L' length , can we?
If not, then, this makes the Lorentz transformation
for time, in its known form, questionable, doesn't it?

The problem is not insurmountable:

<<..the instantaneous Coulomb potential associated with
the charge density, which appears at first glance to
violate causality, since motions of electric charge appear
everywhere instantaneously as changes to the Coulomb
potential. This is generally explained by pointing out
that the scalar and vector potentials themselves do not
affect the motions of charges, only the combinations
of their derivatives that form the electromagnetic
field strength. Although one can compute the field
strengths explicitly in Coulomb gauge and demonstrate
that changes in them propagate at the speed of light,
it is much simpler to observe that the field strengths
are unchanged under gauge transformations and to
demonstrate causality in the manifestly covariant
Lorenz gauge described below. >>
http://en.wikipedia.org/wiki/Gauge_fixing

So the contraction moves in spacetime.

<< a general Lorentz transformation preserves the
volume of space-time. Since time is dilated by a
factor gamma in a moving frame, the volume of space-time
can only be preserved if the volume of ordinary 3-space
is reduced by the same factor. As is well-known, this
is achieved by length contraction along the direction
of motion by a factor gamma. >>
http://farside.ph.utexas.edu/teaching/em/lectures/node114.html

Remembering...

<< space-time cannot be regarded as a straightforward
generalization of Euclidian 3-space to four dimensions,
with time as the fourth dimension. The distribution of
signs in the metric ensures that the time coordinate
is not on the same footing as the three space coordinates.
Thus, space-time has a non-isotropic nature which is
quite unlike Euclidian space, with its positive
definite metric. According to the relativity principle,
all physical laws are expressible as interrelationships
between 4-tensors in space-time. >>
http://farside.ph.utexas.edu/teaching/em/lectures/node113.html

Sue...



;--))

Regards, LL

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