54
DOC.
43 JANUARY
1915
and
as
has
actually
been advanced
by you (and
to
a
lesser
extent
by Poincaré).
Nevertheless, surely my approach
was
not
really
so
terribly
unsatisfactory.
In
want of
a
general theory, pleasure
can
also be found in
the
explanation
of
a single
fact, provided
this
explanation is not
forced. This the
interpretation
offered
by
me
and FitzGerald
was
not;
it
was,
on
the
contrary,
the
only possible one,
and
I
added the
observation
that the
hypothesis
is
obtained when
you
extend
to
other
forces
what
was
already
known
about the
influence of
translation
on
electrostatic
forces.[12]
Had
I
stressed
this
more[13]
[I
must
admit,
though,
that
I
made this ob-
servation
only
after I
had
found the
hypothesis],
then the
hypothesis
would have
left less of
an
ad
hoc[14]
contrived
impression.
Whether
it involves
the
explanation
of
a negative or a
positive
result
seems
to
me
hardly
to
make
a
difference.
I
would like to
attach another
remark
of
a more
didactic nature. If
the
“con-
traction”
is
derived from
the
formulas of
the
theory
of
relativity
(which
is nat-
urally justified
in and of
itself)
and
nothing
more
is
added in
commentary,
then
there
is
a
danger
of
raising
the
impression
that
only
“fictitious”
things
were
in-
volved here
and
not
a
real
physical phenomenon;
at least
I
have
occasionally
encountered statements
by proponents
of relativity theory
which
appear
to attest
to
such
a
view.
In consideration of
this,
a
comment
can
be made
that
when
we
observe
a “change” by
constantly
comparing
it
to
one
and
the
same
coordinate
system
K,
this
“change” according
to
common
usage (and why
can we
not
keep
to
that?) represents
a
physical phenomenon.
The contraction of
a
rod
moving
with reference
to
K
is just
as
real
as
expansion
at
raised
temperatures,[15]
and
in molecular theory
the
one
phenomenon
is
explained completely similarly
to
the other from the
point of view
of molecular
forces.
It
can
be said that these
forces
and their
effect
are
modified
by
the
translation,
an
interpretation
which
can
be
given slightly
more
vivid color
by
thinking
of
a
transmission
of
the
effects
through
an
ether.[16]
It
goes
without
saying
that without
tracing
these
changes
in
detail,
the
statement would
suffice
that all actions
of force
must be such
that
they
comply
with the
principle
of
relativity.
We
earlier
spoke
repeatedly
about
“time”
and
“simultaneity.”
For
this
reason
I
take
the
liberty
to
examine
the
interpretation
that
most
appeals
to
me.
First
of all I
note
that
it has to do with the
images
we
form for ourselves of
the
phenomena
which, according
to
our
individual
characters, acquire
more or
less
superfluous ingredients
and
are more or
less
vividly
colored.
Whatever
they
may be,
however,
the
framework in which
the
image
is sketched,
as
it
were,
is
determined
by
our
conceptions
of
space
and
time.
I
do
not venture to
examine
the
origin
of these
conceptions
and
their
deeper
significance;
it
seems
indisputable
to
me
that
each
one
of
us
simply
has them and
that,
as
far
as
we can
know, they
agree among
different
persons.
We
see
quite clearly
not
only
the
concepts
of “next
to,” “behind,”
and
“above”
one
another,
but
also of
“after.” In this
connection,
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