Re: Is the LT for time correct?


"xray4abc" <lemhenyil@xxxxxxxx> wrote in message news:246b7283-4867-46c4-b27c-bfea2b2cbd24@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
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?

We can send radar signals to the endpoints of the moving
object and arrange things in such a way that the reflection
events of the signals occor simultaneously. By timing the
signals and their echos we get the distances to these
endpoints. The difference between these distances is
the lenght of the moving object.

Operational procedure:
- Send signal1 at local time ts1 to endpoint1.
- Send signal2 at local time ts2 to endpoint2.
- Receive echo1 from signal1 at local time te1.
- Receive echo2 from signal2 at local time te2.
- Time of reflection event1 on eindpoint1 = 1/2 (te1+ts1).
- Time of reflection event2 on eindpoint2 = 1/2 (te2+ts2).
- Distance of reflection event1 on eindpoint1 = 1/2 (te1-ts1) c.
- Distance of reflection event2 on eindpoint2 = 1/2 (te2-ts2) c.
- If times are equal, i.o.w. if
1/2 (te1+ts1) = 1/2 (te2+ts2),
then length of moving object is given by
| 1/2 (te1-ts1) c - 1/2 (te2-ts2) c |

Note that this length measuring method also works for
non-moving objects. In that case we don't even need
to arrange the simultaneity of the reflection events.

A less practical, but still possible, way is by measuring
the length of a moving object by putting 'fixed' clocks
all along its path and having these clock mark the time
when the endpoints are passing. The difference between
any pair of such clocks that mark the same time, is the
lenght of the moving object,

If not, then, this makes the Lorentz transformation
for time, in it known form, questionable, doesn't it?
;--))

Indeed it would. But the transformation was of course
conceived with the above measuring methods in mind.
After all, this is physics, remember, not philosophy.

Dirk Vdm
.

Relevant Pages

  • Re: Is the LT for time correct?
    ... different IRFs, one must refer to the endpoints ... We can send radar signals to the endpoints of the moving ... the lenght of the moving object. ... Note that this length measuring method also works for ...
    (sci.physics.relativity)
  • Re: Is the LT for time correct?
    ... different IRFs, one must refer to the endpoints ... the lenght of the moving object. ... Note that this length measuring method also works for ...
    (sci.physics.relativity)
  • Re: Is the LT for time correct?
    ... Dirk Van de moortel skrev: ... different IRFs, one must refer to the endpoints ... the lenght of the moving object. ...
    (sci.physics.relativity)
  • Re: Is the LT for time correct?
    ... >>> one IRF at a time, i.e. in the frame where the ... >> We can send radar signals to the endpoints of the moving ... >> the lenght of the moving object. ... but the (remote!) reflection events are simultaneous if ...
    (sci.physics.relativity)
  • Re: Is the LT for time correct?
    ... >>> one IRF at a time, i.e. in the frame where the ... >> We can send radar signals to the endpoints of the moving ... >> the lenght of the moving object. ... The echo reflection events are simultaneous if ...
    (sci.physics.relativity)
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