The Sleepwalkers (96 page)

Now
all
this
is
familiar
ground
to
us.
Copernicus
refers
first
to
the
so-called
"Egyptian"
system
of
Herakleides,
^*
that
"halfway
house",
in
which
the
two
inner
planets
circle
round
the
sun,
while
the
sun
itself,
and
the
outer
planets,
still
go
round
the
earth.
He
then
takes
the
second
step
(of
letting
the
outer
planets
too
circle
round
the
sun)
which
in
antiquity
was
taken
either
by
Herakleides
or
by
Aristarchus;
and
finally,
the
third
step
to
the
complete
heliocentric
system,
where
all
the
planets,
including
the
earth,
revolve
round
the
sun,
as
suggested
by
Aristarchus
of
Samos.

____________________

There
can
be
no
doubt
that
Copernicus
was
acquainted
with
Aristarchus'
idea,
and
that
he
was
following
in
his
footsteps.
The
proof
of
this
is
to
be
found
in
Copernicus'
own
manuscript
of
the
Revolutions
,
where
he
refers
to
Aristarchus
–
but,
characteristically,
this
reference
is
crossed
out
in
ink.
Thus
Aristarchus'
forerunners
are
given
credit
in
the
book,
but
not
Aristarchus
himself
–
just
as
the
names
of
Rheticus,
of
Brudzewski
and
Novara,
the
teachers
to
whom
Copernicus
owed
most,
are
omitted.
He
had
to
mention
the
fact
that
the
heliocentric
idea
was
known
to
the
ancients,
in
order
to
prove
its
respectability,
as
it
were;
yet
he
confused
the
trail,
as
was
his
habit,
by
leaving
out
the
most
important
among
them.
²⁷

It
is
highly
unlikely,
though,
that
Copernicus
should
have
stumbled
on
his
idea
simply
by
browsing
through
the
ancient
philosophers.
Talk
of
a
moving
earth,
of
the
earth
as
a
planet
or
star,
was
becoming
increasingly
frequent
in
the
days
of
his
youth.
We
have
seen
(p.
99
f)
that
during
the
later
Middle
Ages
the
system
of
Herakleides
had
been
favoured
by
most
of
the
scholars
who
took
an
interest
in
astronomy.
From
the
thirteenth
century
onward
the
influence
of
Ptolemy
had
reasserted
itself,
simply
because
there
existed
no
other
planetary
theory
as
detailed
and
comprehensive
as
the
Almagest
;
but
soon
afterwards
a
strong
current
of
criticism
and
opposition
arose.
Earlier
already,
Averroes,
the
greatest
Arab
philosopher
in
Europe
(1126-1198)
had
commented:
"The
Ptolemaic
astronomy
is
nothing
so
far
as
existence
is
concerned;
but
it
is
convenient
for
computing
the
non-existent."
²⁸
He
had
no
better
alternative
to
offer;
but
his
epigram
could
serve
as
a
motto
for
the
growing
discontent
with
the
prevailing
double-think
in
cosmology.

This
metaphysical
malaise
flared
into
open
revolt
in
the
first
half
of
the
century
into
which
Copernicus
was
born.
Nicolas
of
Cusa
(1401-
1464),
a
German
ecclesiastic,
the
son
of
a
boatsman
on
the
Moselle,
who
rose
to
the
rank
of
Cardinal,
was
the
first
to
kick
against
the
lid
of
the
medieval
universe.
In
his
Learned
Ignorance
,
²⁹
written
in
1440,
printed
in
1514,
twenty
years
before
the
Revolutions,
he
asserted
that
the
world
had
no
boundaries,
and
consequently
neither
a
periphery
nor
a
centre.
It
was
not
infinite,
merely
"interminate",
that
is
unbounded,
and
everything
in
it
was
in
flux:

"Since,
then,
the
earth
cannot
be
the
centre,
it
cannot
be
entirely
devoid
of
motion...
It
is
clear
to
us
that
the
earth
is
really
in
motion
though
this
may
not
be
apparent
to
us,
since
we
do
not
perceive
motion
except
by
comparison
with
something
fixed."
³⁰

Earth,
moon
and
planets
all
move
round
a
centre,
which
is
not
defined;
but
Cusa
expressly
denies
that
they
move
either
in
perfect
circles,
or
at
uniform
speed:

"Moreover,
neither
the
sun,
nor
the
moon,
nor
any
sphere
–
though
to
us
it
seems
otherwise
–
can
in
[its]
motion
describe
a
true
circle,
because
they
do
not
move
around
a
fixed
base.
Nowhere
is
there
a
true
circle
such
that
a
truer
one
would
not
be
possible,
nor
is
[anything]
ever
at
one
time
[exactly]
as
at
another,
neither
does
it
move
in
a
precisely
equal
[manner],
nor
does
it
describe
an
equally
perfect
circle,
though
we
are
not
aware
of
it."
³¹