The Sleepwalkers (161 page)

"It
is
therefore
clear
that
the
traditional
doctrine
about
gravity
is
erroneous...
Gravity
is
the
mutual
bodily
tendency
between
cognate
[i.e.
material]
bodies
towards
unity
or
contact
(of
which
kind
the
magnetic
force
also
is),
so
that
the
earth
draws
a
stone
much
more
than
the
stone
draws
the
earth...

Supposing
that
the
earth
were
in
the
centre
of
the
world,
heavy
bodies
would
be
attracted
to
it,
not
because
it
is
in
the
centre,
but
because
it
is
a
cognate
[material]
body.
It
follows
that
regardless
where
we
place
the
earth
...
heavy
bodies
will
always
seek
it...

If
two
stones
were
placed
anywhere
in
space
near
to
each
other,
and
outside
the
reach
of
force
of
a
third
cognate
body,
then
they
would
come
together,
after
the
manner
of
magnetic
bodies,
at
an
intermediate
point,
each
approaching
the
other
in
proportion
to
the
other's
mass
(my
italics).

If the earth and the moon were
not kept in their respective orbits by a spiritual or some other
equivalent force, the earth would ascend towards the moon one
fifty-fourth part of the distance, and the moon would descend the
remaining fiftythree parts of the interval, and thus they would
unite. But the calculation presupposes that both bodies are of the
same density.

If
the
earth
ceased
to
attract
the
waters
of
the
sea,
the
seas
would
rise
and
flow
into
the
moon...

If
the
attractive
force
of
the
moon
reaches
down
to
the
earth,
it
follows
that
the
attractive
force
of
the
earth,
all
the
more,
extends
to
the
moon
and
even
farther...

Nothing
made
of
earthy
substance
is
absolutely
light;
but
matter
which
is
less
dense,
either
by
nature
or
through
heat,
is
relatively
lighter...

Out
of
the
definition
of
lightness
follows
its
motion;
for
one
should
not
believe
that
when
lifted
up,
it
escapes
to
the
periphery
of
the
world,
or
that
it
is
not
attracted
by
the
earth.
It
is
merely
less
attracted
than
heavier
matter,
and
is
therefore
displaced
by
heavier
matter,
so
that
it
comes
to
rest
and
is
kept
in
its
place
by
the
earth..."
35a

In
the
same
passage,
Kepler
gives
the
first
correct
explanation
of
the
tides
as
a
motion
of
the
waters
"towards
the
regions
where
the
moon
stands
in
the
zenith".
In
a
later
work
(the
Somnium
)
he
explained
the
tides,
not
by
the
attraction
of
the
moon
alone,
but
of
moon
and
sun
combined;
he
thus
realized
that
the
attraction
of
the
sun
reached
as
far
as
the
earth!

Yet
in
spite
of
this,
the
sun
in
his
cosmology
is
not
an
attracting
force,
but
acts
like
a
sweeping
broom.
In
the
text
of
the
New
Astronomy
he
seems
to
have
forgotten
all
that
he
said
in
the
Preface
about
the
mutual
attraction
between
two
bodies
in
empty
space,
and
his
strikingly
correct
definition
of
gravity
being
proportional
to
the
attracting
mass.
The
definitions
of
gravity
in
the
Preface
are
indeed
so
striking,
that
Delambre
exclaims:
³⁶
"
Voilà
qui
é'tait
neuf,
vraiment
beau,
et
qui
n'avait
besoin
que
de
quelques
developpements
et
que
de
quelques
explications.
Voilà
les
fondaments
de
la
Physique
moderne,
céleste
et
terrestre
."
^*
But
when
he
tried
to
work
out
the
mechanics
of
the
solar
system,
all
these
beautiful
new
insights
were
lost
again
in
confusion.
Could
some
similar
paradox
be
responsible
for
the
crisis
in
modern
physics
–
some
unconscious
blockage
which
prevents
us
from
seeing
the
"obvious",
and
compels
us
to
persist
in
our
own
version
of
wave-mechanical
double-think?

____________________

At
any
rate,
most
twentieth-century
physicists
will
feel
a
sneaking
sympathy
for
the
man
who
nibbled
at
the
concept
of
gravity,
and
yet
was
unable
to
swallow
it.
For
Newton's
concept
of
a
'gravitational
force"
has
always
lain
as
an
undigested
lump
in
the
stomach
of
science;
and
Einstein's
surgical
operation,
though
easing
the
symptoms,
has
brought
no
real
remedy.
The
first
to
sympathise
with
Kepler
would
have
been
Newton
himself,
who,
in
a
famous
letter
to
Bentley,
wrote: