Re: Hewitt Special Relativity Example (Long)

[Bernard Cleyet <anngeorg@PACBELL.NET>]

The journal " Science" back in the 70's or 80's discussed this.  I remember that it
included two accelerations, one when the astronaut leaves the earth and the other on
return.  The rest I don't remember except that it used JM's asymmetry.

bc

John Mallinckrodt wrote:

> Glenn Knapp wrote:
>
> > I recall reading (sorry, can't cite the source) that the time dilation in
> > the spacecraft is a result of its acceleration, which the stationary earth
> > does not experience.  The idea being that the spacecraft and the earth are
> > not two different reference frames moving away or towards one another at a
> > constant velocity.  One is an accelerated frame (at least at some point on
> > the voyage) and the other is not.
> >
> > So what is the actual, copper-bottomed, good to go, widely accepted
> > explanation for the twin paradox?
>
> I think the correct answer to this question--at least the "widely
> accepted" part--might be that there simply is none.  Nevertheless,
> any proper explanation will necessarily depend at some level on the
> fact that the frames are not equivalent due specifically to the fact
> that one of them accelerates at some point during the journey and the
> other doesn't.
>
> One way to go about it is to assume that the change in velocity is
> instantaneous (which of course smooshes the astronaut) and to note
> (using a spacetime diagram, for instance) that this causes the
> astronaut to jump instantaneously from a reference frame in which the
> stay at home twin's clock reads an earlier time, to one in which the
> same clock reads a later time.  During both legs of the journey the
> astronaut would find that the stay at home twin's clock runs slow,
> but the instantaneous jump forward at the journey's midpoint more
> than compensates.
>
> Another way is to consider the acceleration as producing an effective
> uniform gravitational field for the astronaut and to note that the
> stay at home twin is at a "very high altitude" in this field.  Then,
> as a result of the GR altitude effect, the stay at home twin's clock
> runs faster then the astronaut's during the acceleration phase.
>
> --
> John Mallinckrodt        mailto:ajm@csupomona.edu
> Cal Poly Pomona         http://www.csupomona.edu/~ajm
>
> This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.

This posting is the position of the writer, not that of SUNY-BSC, NAU or the AAPT.