The Sleepwalkers (120 page)

It
would
be
difficult
to
over-estimate
the
revolutionary
significance
of
this
proposal.
For
the
first
time
since
antiquity,
an
attempt
was
made
not
only
to
describe
heavenly
motions
in
geometrical
terms,
but
to
assign
them
a
physical
cause
.
We
have
arrived
at
the
point
where
astronomy
and
physics
meet
again,
after
a
divorce
which
lasted
for
two
thousand
years.
This
reunion
of
the
two
halves
of
the
split
mind
produced
explosive
results.
It
led
to
Kepler's
three
Laws,
the
pillars
on
which
Newton
built
the
modern
universe.

Again
we
are
in
the
fortunate
position
of
being
able
to
watch,
as
in
a
slow-motion
film,
how
Kepler
was
led
to
taking
that
decisive
step.
In
the
key
passage
from
the
Mysterium
Cosmographicum
which
follows,
the
index-numbers
are
Kepler's
own,
and
refer
to
his
Notes
in
the
second
edition:

"If
we
want
to
get
closer
to
the
truth
and
establish
some
correspondence
in
the
proportions
[between
the
distances
and
velocities
of
the
planets]
then
we
must
choose
between
these
two
assumptions:
either
the
souls
ⁱⁱ
which
move
the
planets
are
the
less
active
the
farther
the
planet
is
removed
from
the
sun,
or
there
exists
only
one
moving
soul
ⁱⁱⁱ
in
the
centre
of
all
the
orbits,
that
is
the
sun,
which
drives
the
planet
the
more
vigorously
the
closer
the
planet
is,
but
whose
force
is
quasi-exhausted
when
acting
on
the
outer
planets
because
of
the
long
distance
and
the
weakening
of
the
force
which
it
entails."
¹¹

To
this passage Kepler made, in the second edition, the following notes:

"(ii).
That
such
souls
do
not
exist
I
have
proved
in
my
Astronomia
Nova
.

(iii).
If
we
substitute
for
the
word
'soul'
the
word
'force'
then
we
get
just
the
principle
which
underlies
my
physics
of
the
skies
in
the
Astronomia
Nova
...
For
once
I
firmly
believed
that
the
motive
force
of
a
planet
was
a
soul...
Yet
as
I
reflected
that
this
cause
of
motion
diminishes
in
proportion
to
distance,
just
as
the
light
of
the
sun
diminishes
in
proportion
to
distance
from
the
sun,
I
came
to
the
conclusion
that
this
force
must
be
something
substantial
–
'substantial'
not
in
the
literal
sense
but
...
in
the
same
manner
as
we
say
that
light
is
something
substantial,
meaning
by
this
an
unsubstantial
entity
emanating
from
a
substantial
body."
12

We
are
witnessing
the
hesitant
emergence
of
the
modern
concepts
of
"forces"
and
"radiating
energies"
which
are
both
material
and
non-material,
and,
generally
speaking,
as
ambiguous
and
bewildering
as
the
mystical
concepts
which
they
have
come
to
replace.
As
we
watch
the
working
of
the
mind
of
Kepler
(or
Paracelsus,
Gilbert,
Descartes)
we
are
made
to
realize
the
fallacy
of
the
belief
that
at
some
point
between
the
Renaissance
and
the
Enlightenment,
man
shook
off
the
"superstitions
of
medieval
religion"
like
a
puppy
getting
out
of
the
water,
and
started
on
the
bright
new
road
of
Science.
Inside
these
minds,
we
find
no
abrupt
break
with
the
past,
but
a
gradual
transformation
of
the
symbols
of
their
cosmic
experience
–
from
anima
motrix
into
vis
motrix,
moving
spirit
into
moving
force,
mythological
imagery
into
mathematical
hieroglyphics
–
a
transformation
which
never
was,
and,
one
hopes,
never
will
be
entirely
completed.

The
details
of
Kepler's
theory
were
again
all
wrong.
The
driving
force
which
he
attributed
to
the
sun
has
no
resemblance
to
gravity;
it
is
rather
like
a
whip
which
lashes
the
sluggish
planets
along
their
paths.
As
a
result,
Kepler's
first
attempt
to
formulate
the
law
relating
planetary
distances
with
periods
was
so
obviously
wrong,
that
he
had
to
admit
it.
¹³
He
added
wistfully:

"Though
I
could
have
foreseen
this
from
the
beginning,
I
nevertheless
did
not
want
to
withhold
from
the
reader
this
spur
to
further
efforts.
Oh,
that
we
could
live
to
see
the
day
when
both
sets
of
figures
agree
with
each
other!
...
My
only
purpose
was
that
others
may
feel
stimulated
to
search
for
that
solution
toward
which
I
have
opened
the
path."
¹⁴