214 DOC.
26
TIME, SPACE,
AND GRAVITATION
The
special
relativity
theory,
which
was
simply
a
systematic
extension
of the electro-
dynamics of
Maxwell and Lorentz,
had
conse-
quences
which reached
beyond itself. Must the
independence
of
physical
laws
with
regard to
a
system
of co-ordinates
be
limited to
systems
of co-ordinates in
uniform movement of transla-
tion
with
regard
to
one
another
?
What
has
nature
to
do with
the co-ordinate
systems
that
we propose and
with their
motions
?
Although
it
may be necessary for our descriptions of
nature
to employ systems of co-ordinates that
we
have selected arbitrarily, the
choice should
not
be limited in
any way so
far
as
their
stato
of
motion
is
concerned.
(General
theory
of rela-
tivity.)
The application of this
general
theory
of relativity
was
found
to
be in
conflict with
a
well-known
experiment,
according to which it
appeared
that the
weight
and
the
inertia
of
a
body depended
on
the
same
constants
(identity
of
inert and heavy
masses).
Consider
the
case
of
a
system
of
co-ordinates which is
conceived
as
being
in stable rotation
relative to
a
system of
inertia
in
the
Newtonian
sense.
The forces
which,
relatively to
this
system,
are
centrifugal
must, in the Newtonian
sense,
be attributed
to
inertia. But these
centrifugal
forces
are,
like
gravitation,
proportional
to
the
mass
of the
bodies.
Is it
not,
then,
possible
to
regard
the
system
of co-ordinates
as
at rest, and the
centri-
fugal
forces
as
gravitational?
The
interpreta-
tion seemed obvious,
but classical
mechanics for-
bade
it.
This
slight
sketch indicates how
a
generalized
theory
of relativity must
include the laws of
gravitation,
and
actual pursuit of
the
con-
ception
has
justified
the
hope.
But the
way was
harder than
was
expected,
because
it
contra-
dicted Euclidian
geometry.
In other words, the
laws
according to
which material
bodies
are
arranged
in space
do not exactly
agree
with
the laws of
space prescribed
by
the
Euclidian
geometry
of solids. This is what
is
meant by
the
phrase "a warp
in space." The
fundamental
concepts
"straight,'
"plane,"
&e.,
accordingly
lose
their
exact meaning
in
physics.
In
the
generalized
theory
of
relativity,
the
doctrine
of space
and
time,
kinematics,
is
no
longer
one
of
the absolute
foundations of general
physics.
The
geometrical states
of
bodies and
the
rates of
clocks depend
in the first
place on
their
gravitational
fields,
which
again
are pro-
duced
by
the material
systems
concerned.
Thus the
new
theory
of gravitation
diverges
widely
from that
of
Newton with
respect
to
its
basal principle.
But
in
practical
application
the
two
agrew so
closely
that it has been difficult
to find cases
in
which the actual differences
could
be subjected to
observation. As yet only
the
following
have
been
suggested
:-
1.
The distortion of
the oval orbits
of
planets
round the
sun
(confirmed
in the
case
of the
planet
Mercury).
2.
The deviation of
light-rays
in
a
gravita-
tional
field
(confirmed
by
the English
Solar
Eclipse
expedition).
3.
The
shifting of spectral
lines towards
the
red end of the
spectrum
in the
caso
of
light
coming to
us
from stars of appreciable mass
(not
yet confirmed).
The
groat
attraction of the theory is
its
logical
consistency.
If
any
deduction
from it
should
prove
untenable,
it
must
be
given up.
A
modification of
it
seems
impossible
without de-
struction of
the whole.
No
one
must
think that
Newton's
great crea-
tion
can
be overthrown
in
any
real
sense
by
this
or
by
any
other
theory.
His clear
and wide
ideas.
will
for
ever
retain
their
significance as
the
foundation
on
which
our
modern concep-
tions
of
physics
have been
built.
A
final comment. The
description
of
me
and
my
circumstances in The
Times shows
an
amusing
feat of
imagination
on
the part of the
writer.
By
an
application
of the
theory
of
relativity
to the taste of
readers,
to-day
in
Germany
I
am
called
a
German
man
of science,
and in
England
I
am represented as a
Swiss
Jew. If I
come
to be
regarded as a
bête
noire,
the
descriptions
will
be reversed, and
I shall
become
a
Swiss
Jew for the Germans
and
a
German
men
of
science for the
English
!
PROFESSOR
EDDINGTON ON
NEWTON'S
FORESIGHT.
In
an
article in the Contemporary
Review
on
"Einstein's Theory
of
Space
and Time," Professor
A. S.
Eddington,
referring to
the recent observations
of
the
eclipse
of the
sun,
says:-
"The
deflection of the star Images
means a
bending
of the
ray
of light
as
it
passes near
the
sun,
just
as
though
the light had
weight
which caused it
to drop towards the
sun.
But it is not
the bendine
of light
that
threatens
the downfall of Newton. On
the contrary,
were
Newton alive he would be
con-
gratulating himself
on
his foresight.
In
his
"Opticks"
we
read:-Query 1.-Do not bodies act
upon
light at
a
distance, and by their action bend
it's
rays,
and is not this action
(oce
toris paribus)
strongest at
the least distance
?
"Weight
of
light
seemed less strange to Newton
than
to
us,
because he believed light to conetst of
miaute corspuscles.
whereas for
us
the beading of
a
wave
of
light
is
a
much
more
difficult
conception.
This
confirmation of Newton’s
speculation
is in itself
a
strilking
result; It might perhaps be described
as
the
first
new thing
that
has
been learnt about gravitation
In
more
than 200 years."
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