DOC. 42
SPECIAL AND GENERAL RELATIVITY 273
28
Relativity
that clocks
of identical construction
are placed
at
the
points
A,
B and
C
of the
railway
line
(co-ordinate
system),
and that
they
are
set
in such
a manner
that the
positions
of their
pointers are
simultaneously
(in
the
above
sense)
the
same.
Under
these
conditions
we
understand
by
the
“time” of
an
event
the read-
ing (position
of the
hands)
of
that
one
of these clocks which
is
in the immediate
vicinity
(in
space)
of the
event.
In this
manner a
time-value
is
associated with
every event
which
is
essentially capable
of observation.
This
stipulation
contains
a
further
physical hypothesis,
the
validity
of which
will
hardly
be doubted without
empirical
[12]
evidence
to
the
contrary.
It
has
been
assumed that
all
these
clocks
go
at
the
same
rate
if
they
are
of identical construction.
Stated
more exactly:
When
two
clocks
arranged at rest
in dif-
ferent
places
of
a
reference-body
are
set
in
such
a
manner
that
a
particular position
of
the
pointers
of
the
one
clock
is
simul-
taneous
(in
the above
sense)
with the
same
position
of the
pointers
of the other
clock,
then
identical
“settings”
are
al-
ways
simultaneous
(in
the
sense
of the above
definition).