The Sleepwalkers (94 page)

Towards
the
end
of
this
painful
chapter,
where
Copernicus'
obsession
with
circles
reaches
its
climax,
as
it
were,
the
manuscript
contains
the
lines:
"It
should
be
noticed,
by
the
way,
that
if
the
two
circles
have
different
diameters,
other
conditions
remaining
unchanged,
then
the
resulting
movement
will
not
be
a
straight
line
but
...
an
ellipse
."
^*
This
is
actually
not
true,
for
the
resulting
curve
will
be
a
cycloid
merely
resembling
an
ellipse
–
but
the
odd
fact
is
that
Copernicus
had
hit
on
the
ellipse
which
is
the
form
of
all
planetary
orbits
–
had
arrived
at
it
for
the
wrong
reasons
and
by
faulty
deduction
–
and
having
done
so,
promptly
dropped
it:
the
passage
is
crossed
out
in
the
manuscript,
and
is
not
contained
in
the
printed
edition
of
the
Revolutions
.
The
history
of
human
thought
is
full
of
lucky
hits
and
triumphant
eurekas
;
it
is
rare
to
have
on
record
one
of
the
anti-climaxes,
the
missed
opportunity
which
normally
leaves
no
trace.

____________________

4.
The
Genesis
of
the
Copernican
System

The
figure
of
Copernicus,
seen
from
the
distance,
is
that
of
an
intrepid,
revolutionary
hero
of
thought.
As
we
come
closer,
it
gradually
changes
into
that
of
a
stuffy
pedant,
without
the
flair,
the
sleepwalking
intuition
of
the
original
genius;
who,
having
got
hold
of
a
good
idea,
expanded
it
into
a
bad
system,
patiently
plodding
on,
piling
more
epicycles
and
deferents
into
the
dreariest
and
most
unreadable
among
the
books
that
made
history.

To
deny
that
Copernicus
was
an
original
thinker
may
sound
paradoxical
or
blasphemous.
Let
us
try
to
retrace
the
process
of
reasoning
which
led
Nicolas
Koppernigk
to
the
Copernican
system.
It
is
a
much-debated
problem,
and
of
a
certain
interest
both
to
the
psychology
of
discovery
and
the
history
of
human
thought.

Our
starting
point
is
his
first
astronomical
treatise,
the
Commentariolus
.
It
opens,
characteristically:

"Our
ancestors
assumed
a
large
number
of
celestial
spheres
for
a
special
reason:
to
explain
the
apparent
motion
of
the
planets
by
the
principle
of
regularity.
For
they
thought
it
altogether
absurd
that
a
heavenly
body
should
not
always
move
with
uniform
velocity
in
a
perfect
circle."

Having
stated
his
credo
,
Copernicus
turns
to
Ptolemy,
whose
system,
he
says,
is
consistent
with
the
observed
facts,
but
...
and
here
follows
a
revealing
passage
which
explains
the
reason
that
started
Copernicus
on
his
quest.
It
is
his
shocked
realization
of
the
fact
that
in
Ptolemy's
universe
a
planet
moves
on
perfect
circles,
but
not
really
at
uniform
speed.
More
precisely,
the
planet
does
not
cover
equal
distances
at
equal
times
when
seen
from
the
centre
of
its
circle
–
it
only
appears
to
do
so
when
observed
from
a
different
point
specially
chosen
for
that
purpose.
This
point
is
called
the
punctum
equans,
or
"equant"
for
short.
Ptolemy
invented
this
trick
to
save
the
principle
of
uniform
motion
–
his
punctum
equans
enabled
him
to
say
that
there
exists,
after
all,
a
point
in
space
where
an
observer
could
enjoy
the
illusion
that
the
planet's
motion
is
a
steady
one.
But,
Copernicus
remarks
indignantly,
"a
system
of
this
sort
seemed
neither
sufficiently
absolute
nor
sufficiently
pleasing
to
the
mind."
²³

It
was
the
grievance
of
a
perfectionist
who
could
not
tolerate
this
offence
against
his
ideal
of
circular
uniform
motion.
It
was
an
imaginary
grievance,
for
in
reality
the
planets
did
not
move
in
circles
anyway,
but
on
the
epicycles
of
epicycles,
producing
oval
curves;
and
whether
uniformity
was
"saved"
relative
to
the
centre
of
the
imaginary
epicycle,
or
to
the
equally
imaginary
equant,
made
hardly
any
difference
except
to
an
obsessional
mind.
Yet,
as
Copernicus
himself
explains,
it
was
this
grievance
which
started
the
whole
chain-reaction:

"Having
become
aware
of
these
defects,
I
often
considered
whether
there
could
perhaps
be
found
a
more
reasonable
arrangement
of
circles
...
in
which
everything
would
move
uniformly
about
its
proper
centre,
as
the
rule
of
absolute
motion
requires."
²⁴