We consider a clock paradox where an observer leaves an inertial frame, is accelerated, and after an arbitrary trip returns. We discuss a simple equation that gives an explicit relation in 1+1 dimensions between the time elapsed in the inertial frame and the acceleration measured by the accelerating observer during the trip. A non-closed trip with respect to an inertial frame appears closed with respect to another suitable inertial frame. We use this observation to define the differential aging as a function of proper time. The reconstruction problem of special relativity is discussed and it is shown that its solution would allow the construction of an inertial clock.

1.
P.
Pesic
, “
Einstein and the twin paradox
,”
Eur. J. Phys.
24
,
585
590
(
2003
). This paper gives a historical introduction to the twin paradox. For a bibliography with older papers see Refs. 2,3 4.
2.
G.
Holton
, “
Resource letter SRT1 on special relativity theory
,”
Am. J. Phys.
30
,
462
469
(
1962
).
3.
H. Arzelies, Relativistic Kinematics (Pergamon, Oxford, 1966).
4.
L. Marder, Time and the Space-Traveller (University of Pennsylvania Press, Philadelphia, 1971).
5.
G. D.
Scott
, “
On solutions of the clock paradox
,”
Am. J. Phys.
27
,
580
584
(
1959
).
6.
G.
Builder
, “
Resolution of the clock paradox
,”
Am. J. Phys.
27
,
656
658
(
1959
).
7.
R. H.
Romer
, “
Twin paradox in special relativity
,”
Am. J. Phys.
27
,
131
135
(
1959
).
8.
A.
Schild
, “
The clock paradox in relativity theory
,”
Am. Math. Monthly
66
,
1
18
(
1959
).
9.
C. A.
Hurst
, “
Acceleration and the ‘clock paradox,’ 
J. Austral. Math. Soc.
2
,
120
121
(
1961
/1962).
10.
H.
Lass
, “
Accelerating frames of reference and the clock paradox
,”
Am. J. Phys.
31
,
274
276
(
1963
).
11.
W. G.
Unruh
, “
Parallax distance, time, and the twin ‘paradox,’ 
Am. J. Phys.
49
,
589
592
(
1981
).
12.
S. P.
Boughn
, “
The case of identically accelerated twins
,”
Am. J. Phys.
57
,
791
793
(
1989
).
13.
E.
Eriksen
and
O/.
Grøn
, “
Relativistic dynamics in uniformly accelerated reference frames with application to the clock paradox
,”
Eur. J. Phys.
11
,
39
44
(
1990
).
14.
E. A.
Desloge
and
R. J.
Philpott
, “
Comment on ‘The case of the identically accelerated twins,’ by S. P. Boughn
,”
Am. J. Phys.
59
,
280
281
(
1991
).
15.
T. A.
Debs
and
L. G.
Redhead
, “
The twin ‘paradox’ and the conventionality of simultaneity
,”
Am. J. Phys.
64
,
384
392
(
1996
).
16.
R. P.
Gruber
and
R. H.
Price
, “
Zero time dilation in an accelerating rocket
,”
Am. J. Phys.
65
,
979
980
(
1997
).
17.
H.
Nikolic̀
, “
The role of acceleration and locality in the twin paradox
,”
Found. Phys. Lett.
13
,
595
601
(
2000
).
18.
E. A.
Milne
and
G. J.
Whitrow
, “
On the so-called ‘clock-paradox’ of special relativity
,”
Philos. Mag.
40
,
1244
1249
(
1949
).
19.
J.
Kronsbein
and
E. A.
Farber
, “
Time retardation in static and stationary spherical and elliptic spaces
,”
Phys. Rev.
115
,
763
764
(
1959
).
20.
C. H.
Brans
and
D. R.
Stewart
, “
Unaccelerated-returning-twin paradox in flat space-time
,”
Phys. Rev. D
8
,
1662
1666
(
1973
).
21.
T.
Dray
, “
The twin paradox revisited
,”
Am. J. Phys.
58
,
822
825
(
1990
).
22.
R. J.
Low
, “
An acceleration-free version of the clock paradox
,”
Eur. J. Phys.
11
,
25
27
(
1990
).
23.
J. R.
Weeks
, “
The twin paradox in a closed universe
,”
Am. Math. Monthly
108
,
585
590
(
2001
).
24.
J. D.
Barrow
and
J.
Levin
, “
Twin paradox in compact spaces
,”
Phys. Rev. A
63
,
044104
-
1
(
2001
).
25.
J. P.
Luminet
,
J. P.
Uzan
,
R.
Lehoucq
, and
P.
Peter
, “
Twin paradox and space topology
,”
Eur. J. Phys.
23
,
277
284
(
2002
).
26.
O. Wucknitz, “Sagnac effect, twin paradox and space-time topology:- Time and length in rotating systems and closed Minkowski space-times,” gr-qc/0403111.
27.
C. Møller, The Theory of Relativity (Clarendon, Oxford, 1962).
28.
R. H.
Good
, “
Uniformly accelerated reference frame and twin paradox
,”
Am. J. Phys.
50
,
232
238
(
1982
).
29.
E. A.
Desloge
and
R. J.
Philpott
, “
Uniformly accelerated reference frames in special relativity
,”
Am. J. Phys.
55
,
252
261
(
1987
).
30.
J.
Crampin
,
W. H.
McCrea
,
F. R. S.
McNally
, and
D.
McNally
, “
A class of transformations in special relativity
,”
Proc. R. Soc. London, Ser. A
252
,
156
176
(
1959
).
31.
P. J. Nahin, Time Machines: Time Travel in Physics, Metaphysics, and Science Fiction (Springer, New York, 1999).
32.
E. F. Taylor and J. A. Wheeler, Spacetime Physics (Freeman, San Francisco, 1966).
33.
E.
Sheldon
, “
Relativistic twins or sextuplets?
,”
Eur. J. Phys.
24
,
91
99
(
2003
).
34.
R.
Montgomery
, “
How much does the rigid body rotate? A Berry’s phase from the 18th century
,”
Am. J. Phys.
59
,
394
398
(
1991
).
35.
M.
Levi
, “
Geometric phases in the motion of rigid bodies
,”
Arch. Ration. Mech. Anal.
122
,
213
229
(
1993
).
36.
M.
Levi
, “
Composition of rotations and parallel transport
,”
Nonlinearity
9
,
413
419
(
1996
).
37.
C. W. Misner, K. S. Thorne, and J. A. Wheeler, Gravitation (Freeman, San Francisco, 1973).
38.
M.
Pauri
and
M.
Vallisneri
, “
Märzke-Wheeler coordinates for accelerated observers in special relativity
,”
Found. Phys. Lett.
13
,
401
425
(
2000
).
39.
C. E.
Dolby
and
S. F.
Gull
, “
On radar time and the twin ‘paradox,’ 
Am. J. Phys.
69
,
1257
1261
(
2001
).
40.
F. W. Sears and R. Brehme, Introduction to the Theory of Relativity (Addison–Wesley, Reading, MA, 1968).
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