312
DOC.
31
ON THE RELATIVITY PROBLEM
stars,
and that this line does
not
change
its
position
with
respect
to
the visible vault
of
the
fixed
stars.
If
the
observer
possesses
natural
intelligence
but has learned neither
geometry
nor
mechanics,
he will conclude:
"My
masses are
carrying
out
a
motion
that
is,
at
least
in
part, causally
determined
by
the
system
of the fixed
stars.
The laws
according
to
which
masses
in
my
environment
move are
codetermined
by
the fixed
stars."
A
person
schooled in the sciences
will
smile
at
the
simplemindedness
of
our
observer and will
tell him:
"The
motion of
your
masses
has
nothing
to
do with the
heaven of the fixed
stars;
on
the
contrary,
this motion
is
determined
by
the laws of
mechanics
completely independently
of all of the other
masses.
There
is
a
space
R
in
which these laws
are
valid. These laws
are
such that
your
masses
remain
continually
in
one
plane
of this
space.
But the
system
of fixed
stars cannot rotate
in
this
space
because it would be
torn
apart by
tremendous
centrifugal
forces in that
case.
Hence
it must
necessarily
be
at rest
(at
least
almost!)
if
it is at
all
to
exist
permanently;
this
is
the
reason
why
the
plane
in which
your masses
move
always
crosses
the
same
fixed stars."
-
But
our
fearless observer will
say:
"You
may
indeed be
incomparably
well educated. But
just
as
I could
never
be made
to
believe
in
ghosts,
so
I
cannot
believe in
the
gigantic
thing
of which
you speak
to
me
and
which
you
call
space.
I
can
neither
see
such
a
thing
nor
imagine
it.
Or should
I
think
of
your space
R
as a
very
subtle
net
of bodies
to
which
all
other
things
are
referred?
Then
I can
imagine,
in
addition
to
R,
a
second such
net R'
that
moves
in
an
arbitrary
manner (e.g.,
rotates)
relative
to
R.
Are
your
equations
then
valid
at
the
same
time
also relative
to
R'?" The learned
person
denies this with confidence.
Upon
which the
simpleton:
"But how do the
masses
know with
respect
to
which of the
'spaces'
R,
R',
etc.
they
should be
moving according
to
your
laws,
how do
they recognize
the
space,
or
the
spaces,
by
which
they
should orient themselves?" Now
our
learned
person
is
in
a very embarrassing predicament.
He
certainly
insists that such
privileged spaces
must
exist,
but he
can give no reason
for
why
those
spaces
could be
distinguished
from other
spaces. Upon
which the
simpleton
would
say:
"Then,
for the time
being,
I'll consider
your privileged spaces
as an
idle invention and will stick
to
my
view that
the vault
of
the fixed
stars
codetermines the mechanical behavior of
my
test
masses."
Let
me
explain
in
yet
another
way
the violation of
the most
elementary postulates
of
epistemology
of which
our
physics
is
guilty.
One would
try
in vain
to
explain
what
it is
that
one
should understand
by
the
pure
and
simple
acceleration of
a
body.
One
would succeed
only
in
defining
the relative accelerations of bodies with
respect
to
each other. But
on
the other
hand,
we
base
our
mechanics
on
the
assumption
that
a
force
(cause)
is
necessary
for
creating
an
acceleration of
a
body, ignoring
the fact that
we are
unable
to
explain
what
it is
that
we are
to
understand
by
"acceleration,"
precisely
because
only
relative accelerations
can
be
an
object
of
perception.
The dubious
aspect
of
the
way
in
which
we proceed can
be illustrated
very nicely