The Sleepwalkers (182 page)

In
his
previous
book
on
optics,
published
in
1604,
Kepler
had
shown
that
the
intensity
of
light
diminishes
with
the
square
of
distance;
he
had
explained
the
principle
of
the
camera
obscura
,
the
forerunner
of
the
photographic
camera,
and
the
manner
in
which
the
spectacles
for
the
short
and
long-sighted
worked.
Spectacles
had
been
in
use
since
antiquity,
but
there
existed
no
precise
theory
for
them.
Nor,
if
it
comes
to
that,
did
a
satisfactory
explanation
exist
for
the
process
of
sight
–
the
refraction
of
the
incoming
light
by
the
lenses
in
the
eye,
and
the
projection
of
a
reversed
image
onto
the
retina
–
until
Kepler's
first
book
on
optics.
He
had
modestly
called
it
"a
Supplement
to
Vitellio".
³
This
Vitellio,
a
thirteenth
century
scholar,
had
written
a
compendium
of
optics
mainly
based
on
Ptolemy
and
Alhazen,
and
this
was
the
most
up-to-date
work
on
the
subject
till
Kepler's
advent.
One
must
constantly
bear
in
mind
this
lack
of
continuity
in
the
development
of
science,
the
immense,
dark
lowlands
extending
between
the
peaks
of
antiquity
and
the
watershed,
to
see
the
achievements
of
Kepler
and
Galileo
in
true
perspective.

The
Dioptrice
is
Kepler's
soberest
work
–
as
sober
as
the
geometry
of
Euclid.
He
wrote
it
in
the
same
year
as
his
punchdrunk
Conversation
with
the
Star
Messenger
.
It
had
been
one
of
the
most
exciting
years
in
Kepler's
life;
it
was
followed
by
the
blackest
and
most
depressing.

2.
Disaster

The
year 1611 brought civil war and epidemics to Prague; the abdication
of his imperial patron and provider; the death of his wife and
favourite child.

Men
less
prone
to
astrology
would
have
blamed
such
a
series
of
catastrophes
on
the
evil
influence
of
the
stars;
oddly
enough,
Kepler
did
not.
His
astrological
beliefs
had
become
too
refined
for
that:
he
still
believed
that
the
constellations
influenced
the
formation
of
character,
and
also
had
a
kind
of
catalysing
effect
on
events;
but
the
cruder
form
of
direct
astrological
causation
he
rejected
as
superstition.

This
made
his
position
at
Court
even
more
difficult.
Rudolph,
sliding
from
apathy
into
insanity,
was
now
virtually
a
prisoner
in
his
citadel.
His
cousin
Leopold
had
raised
an
army
and
occupied
part
of
Prague.
The
Bohemian
Estates
appealed
for
help
to
his
brother
Matthias,
who
had
already
dispossessed
Rudolph
of
Austria,
Hungary
and
Moravia,
and
was
preparing
to
take
over
what
was
left.
Rudolph
craved
reassurance
from
the
stars;
but
Kepler
was
too
honest
to
provide
it.
In
a
confidential
letter
to
one
of
Rudolph's
intimate
advisers,
he
explained:

"Astrology
can
do
enormous
harm
to
a
monarch
if
a
clever
astrologer
exploits
his
human
credulity.
I
must
watch
that
this
should
not
happen
to
our
Emperor...
I
hold
that
astrology
must
not
only
be
banished
from
the
senate,
but
also
from
the
heads
of
all
who
wish
to
advise
the
Emperor
in
his
best
interests;
it
must
be
kept
entirely
out
of
his
sight."
⁴

He
went
on
to
say
that,
consulted
by
the
Emperor's
enemies,
he
had
pretended
that
the
stars
were
favourable
to
Rudolph
and
unfavourable
to
Matthias;
but
he
would
never
say
this
to
the
Emperor
himself,
lest
he
became
over-confident
and
neglected
whatever
chance
there
may
be
left
to
save
his
throne.
Kepler
was
not
above
writing
astrological
calendars
for
money,
but
where
his
conscience
was
involved,
he
acted
with
a
scrupulousness
most
unusual
by
the
standards
of
his
time.

On
23
May,
Rudolph
was
forced
to
abdicate
the
Bohemian
crown;
the
following
January
he
was
dead.
In
the
meantime,
Frau
Barbara
contracted
the
Hungarian
fever,
which
was
followed
by
attacks
of
epilepsy
and
symptoms
of
mental
derangement.
When
she
got
better,
the
three
children
went
down
with
the
pox,
which
the
soldiery
had
imported.
The
oldest
and
youngest
recovered;
the
favourite,
six-year-old
Friedrich,
died.
Then
Barbara
relapsed:

"Numbed
by
the
horrors
committed
by
the
soldiers,
and
the
bloody
fighting
in
the
town;
consumed
by
despair
of
the
future
and
by
an
unquenchable
longing
for
her
lost
darling
...
in
melancholy
despondency,
the
saddest
of
all
states
of
mind,
she
gave
up
the
ghost."
⁵