Re: Clock synch

kenseto wrote:
"Tom Roberts" <tjroberts137@xxxxxxxxxxxxx> wrote in message
news:j_PDg.6702$1f6.2244@xxxxxxxxxxxxxxxxxxxxxxxxxxxxx
Those two observers follow different paths through spacetime, and their
path lengths are different. For a timelike observer, elapsed proper time
corresponds to the path length, so it is no surprise that their clocks
display different values when they rejoin, because clocks simply
indicate their elapsed proper times. <shrug>

This is nonsense.....they show different proper time because they were
running at different proper rates when they were apart.

No. If one assumes the clocks tick a different _PROPER_ rates, one does not obtain agreement with experiment.

When any observer in an inertial frame observes the tick rate of a moving clock, it is observed to tick more slowly than the observer's own clocks. When any observer in an inertial frame observes her own clock, it is observed to tick at the same rate as her own clocks (duh!). This latter is a proper measurement, because in modern physics the word "proper" means "in the object's instantaneously comoving inertial frame" (or series of such frames). Note there is nothing "absolute" here, because this applies to _ANY_ inertial frame.

I repeat: the scenario I described above is directly analogous to the fact that two sides of a triangle have a different total path length than the other side. <shrug>


But it is not wrong to say that "their clocks tick at
different rates"

That is not wrong ONLY if you also specify how those rates are to be measured (i.e. from which inertial frames, using what procedures). You always get it wrong because you are not precise enough in your thinking or writing. <shrug>


Tom Roberts
.

Relevant Pages

  • Re: I am Trying To Learn Relativity
    ... let each observer be moving inertially and have ... a co-moving array of assistants that each has a clock synchronized to ... Obviously, by synching clocks with light, SR effectively uses the flash to ... wrt any inertial frame. ...
    (sci.physics.relativity)
  • Re: I am Trying To Learn Relativity
    ... let each observer be moving inertially and>>> have ... Obviously, by synching clocks with light, SR effectively uses the flash to ... >wrt any inertial frame. ... but you are free to synchronize the real clocks of your ...
    (sci.physics.relativity)
  • Re: I am Trying To Learn Relativity
    ... the time they saw the flash, and send it to the observer. ... Obviously, by synching clocks with light, SR effectively uses the flash to ... wrt any inertial frame. ... but you are free to synchronize the real clocks of your ...
    (sci.physics.relativity)
  • Re: Clock synch
    ... There is no "shortening/elongating", in the sense of a given object physically getting shorter or longer. ... d'Inverno is NOT describing a clock whose intrinsic tick rate has physically changed, he is describing a measurement of a clock's rate by an observer in another frame, as I described earlier in this thread. ... which both have identical clocks and which initially show the same value. ... For a timelike observer, elapsed proper time corresponds to the path length, so it is no surprise that their clocks display different values when they rejoin, because clocks simply indicate their elapsed proper times. ...
    (sci.physics.relativity)
  • Re: Clock synch
    ... This should have been Ray ... which both have identical clocks and which initially show the same value. ... How would you call the effect, that, if Observer A stays at home ... experienced different elapsed proper time" then it is correct. ...
    (sci.physics.relativity)