From: ram@zedat.fu-berlin.de
Luigi Fortunati writes:
>So let's make him come back at the same speed, so that it
>takes him another 48 hours to come back, while the Earth
>makes another rotation.
>In doing so, the traveler twin travels for 96 hours (48 to go
>and 48 to return) and ages 96 hours (4 days).
>But on Earth (which rotated only twice) the terrestrial twin
>aged only 2 days and, therefore, remained younger than his
>traveler brother!
>How is it possible?
There is an additional time of aging on Earth that you have not
taken into account.
For the sake of simplicity, I assume that the traveler reverses
his speed instantaneously during the turnaround.
The remaining twin ages during three intervals:
1. During the first phase of the journey, the remaining person
experiences points in time which the traveler moving away from
him perceives as simultaneous to himself (to the traveler).
2. Then, the remaining person experiences points in time that
the traveler never perceives as simultaneous with himself
(with the traveler), neither during the outward journey nor
during the return journey.
3. Finally, during the second and last part of the journey, the
remaining person experiences points in time which the traveler
moving towards him perceives as simultaneous with himself
(with the traveler).
During "1." and "3." the traveling twin ages 96 hours and the
remaining person ages only 48 hours, insofar you were right,
but during "2." the remaining person ages so much more that
at the reunion he is older than the traveler!
Here is a diagram (not true to the angle); it is intended to
be viewed with a monospaced font, but you may get the gist
of it with other fonts as well. (Moderation may omit it if
diagrams of this kind are not allowed in this newsgroup.)
The lines A, B, C, and D, E, F each consist of events which
are simultaneous for the traveling twin. One can see the
large interval "2." with events on Earth for which there
are no simultaneous events for the traveler.
Earth
time ^ t (Earth)
-
-
-
..:. reunion
.- =-,
| - .-.
| =. ,-
| =-. .-,
3.| = ,. ,,
| =. F ,-,
| =-. . ,=.
| - ,. ,=-
| =. .. ,-.
'-..:-. ,. ,-
.- = ,. ,. .-,
| - .. E., ,-
| - ,. . ..-,
| - ,. ,. ,-. inward journey
| = ., .,-,
| = D .. ,:.
| - ,. .=-
| - ,, .-,
| - ., ,-
| ..= .. . -,
| ., .-.
| - .,.-,
| - -=.
| - ..--
| ,=-
2.| = ,== point of reversal
| - .-=.
| - -=.
| - .,.-,
| = .. .-.
| ..= . .. -,
| - ., ,-.
| - ,, .-,
| - .. .--
| = C. ,:,
| ., .,-,
| - ,. ,. ,-.
| - . . . . .-, outward journey
| - .. ., ,-.
'- = ,. ,.B .-,
.-..:,. ,. ,-
| =. .. .-.
| - ,. ,=,
| =-. . ,=.
| =. ,-,
1.| = ,. ,-.
| -,.A .-,
| =, ,-
| - .-.
| =-- Start location
'- ,-..,.,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,,.,.>
x (Earth)
--- SoupGate-Win32 v1.05
* Origin: you cannot sedate... all the things you hate (1:229/2)
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