DOC.
38 ETHER AND RELATIVITY 177
ETHER
AND
RELATIVITY
19
space
is
physically empty.
But
therewith
the
conception
of
the ether
has
again
acquired an intelligible
content,
although
this
content differs
widely
from
that
of
the
ether
of
the
mechanical
undulatory theory
of
light.
The ether
of
the
general
theory
of relativity
is
a
medium which
is
itself
devoid of all mechanical
and
kinematical
qualities,
but
helps
to
determine mechanical
(and electromagnetic)
events.
What
is
fundamentally
new
in
the
ether
of
the
general
theory
of
relativity
as op-
posed
to
the ether
of Lorentz consists in
this,
that the
state of
the
former is
at
every place
determined
by
connections with
the
matter
and the
state
of
the
ether in
neighbouring places,
which
are
amenable
to law in
the
form of differential
equations;
whereas
the
state
of
the
Lorentzian
ether
in the
absence
of
electromagnetic
fields
is
conditioned
by
nothing
outside
itself,
and
is
everywhere
the
same.
The ether of
the
general
theory
of
relativity
is trans-
muted
conceptually
into
the ether of
Lorentz if
we
substitute
constants for
the
functions of
space
which describe the
[21]
[22]
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