vistas in astronomy volume 20 issue part-p1 1976 [doi 10.1016%2f0083-6656%2876%2990005-2] william r....

8/12/2019 Vistas in Astronomy Volume 20 Issue Part-P1 1976 [Doi 10.1016%2F0083-6656%2876%2990005-2] William R. She

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Vistas in Astronomy 1976 Vol. 20, pp. 11-15. Pergamon Press. Printed in Gre at Bri ta in

S E S S I O N 2 - T H E R O Y A L O B S E R V A T O R Y G R E E N W I C H : S E T T I N G T H E S C E N E

2 . S O M E A S P E CT S O F P O S T - R E N A I S S A N C E A S T R O N O M Y

WILLIAM R. SHEA

McG ill University, M ontreal

I n 1 6 1 0 , G a l i l e o p u b l i s h e d h i s

Sidereus Nuncius

i n w h i c h h e r e v e a l e d t h e e x i s t e n c e o f u n k n o w n s t ar s ,

t h e n a t u r e o f t h e M i l k y W a y , t h e r u g g e d s u r f a c e o f th e M o o n , a n d t h e p r e s e n c e o f s a t e ll i te s a r o u n d

J u p i t e r . T h e s t r i k i n g s i m i l a ri t ie s b e t w e e n t h e M o o n a n d t h e E a r t h m a d e t h e a l r e a d y d u b i o u s d i v i si o n

b e t w e e n t h e s u b l u n a r y a n d t h e c e l e s ti a l w o r l d s e v e n le s s p l a u s i b le , a n d t h e f a c t t h a t J u p i t e r c o u l d

o r b i t w i t h a t r a i n o f f o u r s a t e ll i te s p r o v i d e d G a l i l e o w i t h a r e p l y t o t h o s e w h o a s k e d h o w t h e E a r t h

c o u l d r u s h t h r o u g h s p a c e w i t h o u t l o s in g i ts M o o n . T h e t e l e s c o p e c o n t i n u e d t o b e a r w i t n e s s to t h e

t r u t h o f C o p e r n i c u s ' v i s io n , a n d w i t h i n a f e w m o n t h s G a l i l e o w a s a b l e to a n n o u n c e t h a t V e n u s h a d

p h a s e s, a n d t h a t t h e v a r i a t i o n s o f t h e a p p a r e n t d i a m e t e r s o f M a r s a n d V e n u s w e r e i n a g r e e m e n t w i t h

t h e h e l i o c e n t r i c t h e o r y . B y th e e n d o f 1 6 1 0 , t h e C o p e r n i c a n h y p o t h e s i s h a d c r o s se d th e t h r e s h o l d o f

r e s p e c t a b i l i t y . E v e n C la v iu s , t h e s c h o l a r l y a n d p r u d e n t a s t r o n o m e r o f t h e C o l l e g io R o m a n o w e n t so

f a r as t o c o m m e n d G a l i l e o ' s d is c o v e r i es i n n o u n c e r t a i n t e r m s . 1

B u t t h e b a t t l e w a s b y n o m e a n s w o n . A m e r e l o o k i n g - g la s s c o u l d n o t d i s p e l a t h e o r y a b o u t t h e

s t r u c t u r e o f th e w o r l d . T h e A r i s t o t e l i a n s f e l t t h a t G a l i l e o w o u l d h a v e t o f o c u s t h e e y e o f h i s m i n d

o n t h e r e al p r o b l e m s b e f o r e h e c o u l d p e r s u a d e t h e m t o a l t e r th e i r c o n v i c ti o n s a b o u t t h e n a t u r e o f t h e

u n i v e r s e .

F r a n c e s c o S i z z i, a F l o r e n t i n e w h o w a s l a t e r t o a n t i c i p a t e G a l i l e o ' s d i s c o v e r y t h a t t h e p a t h o f

t h e s u n s p o t s i s o b l i q u e , w r o t e a s t r o n g l y - w o r d e d t r a c t in w h i c h h e p o i n t e d o u t t h e m a n i f e s t in c o n -

v e n i e n c e s o f i n c r e a s in g t h e n u m b e r o f p l a n e t s f r o m s e v e n t o e le v e n b y t h e a d d i t i o n o f t h e f o u r a l l e g e d

s a t e ll i te s o f J u p i t e r . H e o f f e r e d a v a r i e t y o f a r g u m e n t s , d r a w n f r o m t h e m i c r o c o s m - m a c r o c o s m

a n a l o g y , o f w h i c h t h e f o l l o w i n g is p e r h a p s t h e m o s t c o g e n t : s i n c e w e h a v e s ev e n o p e n i n g s i n o u r h e a d

( t w o e y e s , t w o e a rs , t w o n o s t r i ls a n d o n e m o u t h ) i t i s t h e r e f o r e " n a t u r a l " t h a t t h e r e s h o u l d b e o n l y

s e v e n p l a n e t s i n t h e f a c e o f t h e h e a v e n s . 2

S i z z i w a s n o t t a k e n t o o s e r i o u s l y e v e n i n h i s o w n d a y , b u t h i s p r e o c c u p a t i o n w i t h t h e n u m b e r

o f p l a n e t s is s y m p t o m a t i c o f h i s a g e a n d w a s sh a r e d b y m o r e p r o m i n e n t f i g u r e s o f t h e S c i e n t i f i c

R e v o l u t io n . T h e y o u n g K e p l e r i n c e s sa n t l y a s k e d h im s e l f, " W h y six p l a n e t s ? " a n d w e k n o w t h a t h e

n e v e r a b a n d o n e d t h e P y t h a g o r e a n s o l u t i o n b a s e d o n t h e f o u r r e g u l a r s o l id s t h a t h e f i r st a d v o c a t e d i n

hi s

Mysterium Cosmographicum

o f 1 5 9 7 .

S o m e 2 0 0 y e a r s la t e r , w h e n t h e p l a n e t s h a d , w i t h t h e a d d i t i o n o f U r a n u s , g r o w n t o s e v e n , a n

i n t e r e s t in t h e i r n u m b e r s w a x e d a g a i n . W h a t s p a r k e d t h e r e vi v al w a s B o d e ' s L a w , a n u m e r i c a l s e r ie s

t h a t b e g i n s w i t h f o u r a n d t h e n i n c r e as e s s t e p b y s t e p a c c o r d i n g t o a si m p l e r u le i n su c h a w a y t h a t

t h e n u m b e r s c o i n c i d e v e r y c lo s e l y w i t h t h e d i s t a n c e s o f th e p l a n e t s f r o m t h e S u n . W h e n U r a n u s w a s

d i s c o v e r e d i t w a s f o u n d t o f i t t h is l a w a n d h e n c e v a s t l y i n c r e a s e d it s p l a u s i b i l i ty . B u t B o d e ' s L a w

a l so ga v e a v a l u e f o r a p l a n e t a r y o r b i t b e t w e e n M a r s a n d J u p i t e r , a n d o n t h e C o n t i n e n t G e r m a n a s t r o -

n o m e r s b a n d e d t h e m s e lv e s in t o g r o u p s t o h u n t f o r t h e m i s si n g p l a n e t m u c h t o t h e d i s m a y o f t h e

e m i n e n t p h i l o s o p h e r , G . W . F . H e g e l , w h o f e l t t h a t t h e s e q u e n c e i n B o d e ' s L a w w a s p u r e l y a c c i d e n t a l

a n d d i d n o t w a r r a n t s u c h a f l u r r y o f s c i e n t if i c a c t i v i ty , H e g e l d o e s n o t a c t u a l l y s a y t h a t h e w a s w o r r i e d

a b o u t t h e t a x p a y e r s ' o r t h e p a t r o n s ' m o n e y , b u t t h e r e c an b e n o d o u b t t h a t h e b e l ie v e d i n t h e

r a t i o n a l i z a t i o n o f re s e a r c h a n d t h a t h e w i s h e d t h a t p r e c i o u s o b s e r v a t i o n t i m e s h o u l d n o t b e w a s t e d .

S c a n n i n g t h e s k y f o r a p l a n e t w h o s e e x i s t e n c e w a s s u r m i s e d f r o m B o d e ' s L a w a p p e a r e d t o H e g e l t o b e

a n a c t o f i n t e l l e c t u a l a n d a d m i n i s t r a t i v e ir r e s p o n s i b i l i t y . A l i t t l e s o u n d r e a s o n i n g , h e a r g u e d i n hi s

Habilitationsschrift

o f 1 8 0 1 , w o u l d s h o w t h a t t h e s ev e n k n o w n p l a n e t s ar e s u i t a b l y s p a c e d a n d t h a t

11


2/5

1 2 W I L L I A M R . S H E A

t h e r e i s n o g a p c r y i n g o u t t o b e f i l l e d b e t w e e n M a r s a n d J u p i t e r . L i k e K e p l e r h e f o u n d h is s o l u t i o n i n

P l a t o b u t t h i s t i m e i n t h e s o - c a l l e d P y t h a g o r e a n s e r i e s r a t h e r t h a n i n t h e r e g u l a r s o l i d s . T h i s s e r ie s

( 1, 2 , 3 , 4 , ( 2 2 ), 9 ( 3 2 ) , 8 ( 2 3 ) , 2 7 ( 3 3 ) n o t o n l y c o n v e n i e n t l y l i m i t s t h e n u m b e r o f p l a n e t s to 7 , b u t

i t a l so r e ta i n s b e t w e e n t h e f o u r t h a n d t h e f i f t h p l a n e t t h e l a r g e d i s t a n c e w h o s e i n c o n g r u i t y c a u s e d

a s t r o n o m e r s a l l o v e r E u r o p e t o l o o k f o r a p l a n e t b e t w e e n M a r s a n d J u p i t e r . O n H e g e l 's n e o -

P y t h a g o r e a n e x p l a n a t i o n t h e r e i s n o i n c o n g r u i t y , u n l e s s it is t o b e f o u n d i n h i s s t r an g e a n d u n e x p l a i n -

e d s u b s t i t u t i o n o f 1 6 f o r 8 a s th e r e l a t i v e d i s t a n c e o f t h e s i x t h p l a n e t S a t u r n . 3

A s t r o n o m e r s m a y e x p e r i e n c e d i f f i c u l t ie s i n j u s t i f y i n g th e i r u se o f p r e c i o u s o b s e r v a t i o n t i m e b u t

a r m c h a i r p h i l o s o p h e r s a r e s u b j e c t t o e v e n g r e a t e r p e r il s . B e f o r e H e g e l h a d d e l i v e r e d h i s in a u g u r a l

l e c t u r e a t I e n a i n 1 8 0 1 , P i a z z i h a d s i g h t e d t h e a s t e r o i d C e r e s a n d , w i t h i n 7 y e a r s , P a ll a s, J u n o , a n d

V e s t a h a d b e e n d e t e c t e d b y e n t h u s i a s t s o f B o d e ' s L a w .

I n h i s

Naturpbilosopbie

o f 1 8 1 6 , H e g e l g r a c i o u s l y a c k n o w l e d g e d t h e e x i s t e n c e o f t h e s e a s t e ro i d s

a n d , s i n c e h e h a d b y t h e n b e c o m e E u r o p e ' s l e a d i n g p h i l o s o p h e r , h e e v e n a d m i t t e d s o m e m e r i t in

B o d e ' s L a w . H e w o u l d n o t , h o w e v e r , a b a n d o n h i s d e e p c o n v i c t i o n th a t t h e p l a n e t a r y s y s t e m w a s

" g o v e r n e d b y c o n s t r u c t s o f t h e m i n d " . T h e P y t h a g o r e a n s e r ie s w a s n o t , h e r e g r e t f u l l y c o n f e s s e d , t h e

o n e t h a t t h e C r e a t o r h a d u s e d i n o r d e r i n g t h e p l a n e t s . A l l t h a t c o u l d n o w b e a d d u c e d w a s t h a t t h e

p l a n e t s fe l l i n t o t h r e e g r o u p s . T h e f o u r p l a n e t s w i t h n o s a t e ll i te s , o r o n l y o n e s u c h a s t h e E a r t h , m a d e

u p t h e f i r s t, t h e a s t e r o i d s t h e s e c o n d , a n d t h e t h i r d w a s c o m p o s e d o f t h e o u t e r p l a n e t s w i t h s e v e ra l

s a t e l li t e s o r r in g s s u c h a s S a t u r n . 4 F o r t u n a t e l y , H e g e l d i e d in 1 8 3 1 a n d w a s s p a r e d t h e s h o c k o f t h e

d i s c o v e r y o f t w o s a t e ll i te s o f M a r s b y A s a p h H a l l i n 1 8 7 7

F o r t h e p u r p o s e o f t h i s p a p e r I c o n s i d e r P o s t - R e n a i s s a n c e a s t r o n o m y a s c o v e r in g t h e p e r i o d

b e t w e e n t h e h e r m e t i c j u s t i f i c a ti o n o f t h e n u m b e r s e ve n b y S i z zi a n d t h e P y t h a g o r e a n v i n d i c a t i o n o f

t h e s a m e n u m b e r b y H e g e l .

O f c o u r s e , d u r i n g th i s p e r i o d m u c h w a s g o i n g o n o u t s i d e t h e m i n d s o f p h i l o s o p h e r s , a n d t h e

m o s t e x c i t i n g e l e m e n t w a s n o t t h e q u e s t f o r t h e " t r u e " m a t h e m a t i c a l s e ri e s b u t t h e i n c r ea s e i n s iz e

o f t h e u n i v e r s e .

C o p e r n i c u s h a d b e e n f u l l y a w a r e o f t h e c o n s e q u e n c e o f as s e r ti n g t h a t t h e E a r t h m o v e d a r o u n d

t h e S u n a l t h o u g h t h e f i x e d st a r s a p p e a r i m m o b i l e . T h i s c o u l d b e r e c o n c i l e d w i t h t h e e x p e r i m e n t a l

e r r o r o f 6 t o 1 0 m i n u t e s o f a r c p r e s e n t in t h e d e t e r m i n a t i o n o f t h e p o s i t i o n o f s t a rs o n l y i f t h e y w e r e

a th o u s a n d t i m e s f a r t h e r t h a n t h e r a d i u s o f t h e E a r t h ' s o r b i t . T h i s m e a n t t h a t a v a s t t r a c t o f e m p t y

s p a c e m u s t s e p a r a t e S a t u r n f r o m t h e s p h e r e o f f i x e d s ta r s a n d C o p e r n i c u s s e e m s t o h a v e p o s i t iv e l y

w e l c o m e d t h i s a s e v i d e n c e o f t h e p e r f e c t i o n o f " t h e g o d l i k e w o r k o f t h e B e s t a n d G r e a t e s t A r t i s t "

w h o c l ea r ly s e t a p a r t " t h e m o v e d f r o m t h e u n m o v e d " , s B u t m a n y s a w in t h is e n o r m o u s d i s ta n c e

b o t h a l a c k o f p r o p o r t i o n a n d a m e a n i n g l e s s v o i d . S i m p l i c i o , i n G a l i l e o ' s

Dialogue on tbe Great

World Systems e x p re s se s a v ie w c o m m o n t o m a n y a s t r o n o m e r s i n cl u d i n g T y c h o B r a h e : " N o w w h e n

w e se e t h e b e a u t i f u l o r d e r o f t h e p l a n e ts , a r r a n g e d a r o u n d t h e E a r t h a t d i s t a n c e s c o m m e n s u r a t e w i t h

t h e i r p r o d u c i n g u p o n i t t h e i r e f fe c t s f o r o u r b e n e f i t , w h y g o o n t o p l a c e b e t w e e n t h e h i g h e s t o r b ,

n a m e l y t h a t o f S a t u r n , a n d t h e s t e ll a r s p h e r e a n e n o r m o u s , s u p e r f l u o u s a n d v a i n s p a c e w i t h o u t a n y

s t a r w h a t s o e v e r ? T o w h a t e n d ? F o r t h e u s e a n d c o n v e n i e n c e o f w h o m ? ' '6

Y e t C o p e r n i c u s h a d a ra d i c a l p r e c u r s o r i n C a r d i n a l C u s a n u s w h o , i n h i s

Docta Ignorantia

s p o k e

o f a n i n fi n i te w o r l d , a v i ew t h a t w a s c h a m p i o n e d i n so m e w h a t m o r e s t r id e n t t o n e s b y G i o r d a n o

B r u n o i n t h e s i x t e e n t h c e n t u r y . F o r B r u n o ' s f o l l o w e r s t h e r e w e r e a s m a n y w o r l d s as t h e r e a r e f i x e d

s t ar s a n d t h e y d e c l a r e d t h a t t h e n o v a o f 1 6 0 4 h e r a l d e d t h e b i r t h o f a n e w w o r l d . T h i s , f o r K e p l e r ,

w a s s l e e p w a l k i n g o f t h e w o r s t k i n d : t h e n o t i o n o f a n i n f in i t e u n i v e r se m a d e h i m s h u d d e r a s a t t h e

m e n t i o n o f s o m e t h i n g o c c u l t . 7

B u t t h e t e l e s c o p e w e n t o n d i s c l o s in g h o w s i m i la r o t h e r p l a n e t s ar e to t h e E a r t h . T h e m o s t

s p e c t a c u l a r re v e l a t i o n w a s t h e d i s c o v e r y t h a t t h e a p p a r e n t l y s m o o t h a n d p e r f e c t l y s p h e r i c a l s u r f a c e

o f th e M o o n w a s r e a ll y " u n e v e n , r o u g h , a n d f u l l o f ca v i ti e s a n d p r o m i n e n c e s " . 8 T h e M o o n a p p e a r e d

s o m u c h l ik e t h e E a r t h t h a t G a l i l e o d e s c r i b e d a la r g e c i r c u la r s p o t i n t h e c e n t r e a s o f f e r i n g " t h e s a m e

a p p e a r a n c e a s w o u l d a r e g i o n l ik e B o h e m i a i f t h a t w e r e e n c l o s e d b y v e r y l o f t y m o u n t a i n s a r r a n g e d

e x a c t l y i n a c i r c l e " . 9

S u c h a c o m p a r i s o n w a s f r a u g h t w i th d a n g e r i n th e h o m e o f t h e C o u n t e r - R e f o r m a t i o n a n d

M o n s i g n o r C i a m p o l i , G a l i l e o ' s f r i e n d in R o m e , f o u n d i t n e c e s s a r y t o w a r n G a l i l e o : " Y o u r o p i n i o n

r e g a r d i n g t h e p h e n o m e n a o f l ig h t an d s h a d o w i n t h e b r i g h t a n d c l ar k s p o t s o f t h e M o o n c r e a t es s o m e

a n a l o g y b e t w e e n t h e l u n a r g l o b e a n d t h e E a r t h ; s o m e b o d y e x p a n d s o n t h i s, a n d s ay s t h a t y o u p l a c e

h u m a n i n h a b i t a n t s o n t h e M o o n ; t h e n e x t f e l lo w st a r t s t o d i s p u t e h o w t h e s e c a n b e d e s c e n d e d f r o m


3/5

S o m e a s p e c ts o f p o s t - R e n a is s a n c e a s t r o n o m y 13

A d a m , o r h o w t h e y c a n h a v e c o m e o f f N o a h ' s a r k, a n d m a n y o t h e r e x t ra v a g a n c e s y o u n e v e r d r e a m e d

O f " . 1 0

B u t t h e t e n d e n c y t o p e o p l e t h e p l a n e t s p r o v e d i r r e s is t ib l e . O n r e a d i n g t h e

Sidereus Nuncius ,

K e p l e r i m m e d i a t e l y b e t h o u g h t h i m s e l f o f c o - o p e r a t i n g w i t h G a l il e o in p r e p a r i n g f o r a n e v e n t u a l t r ip

t o t h e M o o n a n d J u p i t e r . T h e s e p l a n e t s p r o b a b l y h a d i n h a b i t a n t s a n d i t w a s l i k e l y t h a t e x p l o r e r s

f r o m t h e E a r t h w o u l d r e a c h t h e m a s s o o n a s t h e a r t o f f l y i n g w a s m a s t e r e d J

I n 1 6 3 8 , t h e B i s h o p o f C h e s t e r, J o h n W i l k i ns , w r i t i n g u n d e r s o m e w h a t l e s s s e v e re t h e o l o g i c a l

c o n s t r a i n t s t h a n G a l i l e o , a f fi r m e d t h e p l a u s i b i l i t y o f e x t r a t e r r e s t r i a l s b u t s t il l f e l t i t n e c e s s a r y t o d e -

v o t e h a l f h i s b o o k t o s h o w i n g t h a t s u c h a n o p i n i o n w a s n e i t h e r im p i o u s n o r i r r a t io n a l . A f e w y e a r s

l a t e r, P i e rr e B o r e l t h o u g h t h e c o u l d p r o v e t h a t t h e M o o n w a s i n h a b i t e d , 1 2 a n d F o n t e n e l l e , i n h i s

w i d e l y r e a d

Entre t iens sur la plurali t e des mon des ,

s i m p l y t o o k i t fo r g r a n t e d . B y t h e e n d o f t h e

c e n t u r y , a s i s e v i d e n c e d i n J o h n R a y ' s The W i sdom o f G od M ani f e s t e d i n t he W ork s o f C re a ti on , i t

h a d a c h i e v e d t h e s t a tu s o f a t h e o l o g i c a l c o m m o n p l a c e . 1 3

F o n t e n e l l e i n d u l g e d i n a d e s c r i p t i o n o f t h e p h y s i c a l an d p s y c h o l o g i c a l t r a i ts o f t h e i n h a b i t a n t s

o f th e v a r i o u s p l a n e t s . T h e M a r q u i s e , h is p u p i l , is m a d e t o u n d e r s t a n d t h a t t h e p e o p l e o n V e n u s m u s t

r e s e m b l e t h e M o o r s o f G r a n a d a , a s m a l l b l a c k p e o p l e f u l l o f s p i r i t a n d f i r e a lw a y s r e a d y t o m a k e l o v e ,

b u s y w r i t i n g p o e t r y a n d e a g e r t o in v e n t fi e s ta s , d a n c e s a n d p a r a d e s e v e r y d a y J a F o n t e n e l l e ' s

Ent re t i e ns r a n i n t o t h i r t y - t h r e e e d i t i o n s d u r i n g h i s l i f e t i m e a n d s c i e n t is t s d o n o t a p p e a r t o h a v e l o o k e d

a s k a n c e a t th e m . H u y g e n s ' o b j e c t i o n t o s u c h p h a n t a s i e s w a s n o t t h a t t h e y w e r e w r o n g - h e a d e d b u t

t h a t t h e y l a c k e d a s o u n d s c i e n t i fi c f o o t i n g , w h i c h h e p r o c e e d e d t o s u p p l y i n h is o w n

C osmot be ore os .

S i n c e th e s a m e l a w s a p p l y t h r o u g h o u t t h e u n i v e r s e, H u y g e n s d e s c r i b e d in c o n s i d e r a b l e d e t a i l b o t h t h e

p o p u l a t i o n s a n d t h e e c o - s y s t e m s o f o u r n e i g h b o r i n g p l a n e t s. H e w a s a ls o a b l e to e n l i g h t e n h i s r e a d e r s

o n e n g i n e e r i n g t e c h n i q u e s a n d o n t h e p r a c t i c e o f s h i p b u i l d i n g e s p e c i a ll y o n J u p i t e r a n d S a t u r n . 1 s

T h e e i g h t e e n t h c e n t u r y m a y b e s a id to b a s k in t h e l i g h t o f t h e s e n e w c e r t i tu d e s . B e r k e l e y

a s se r ts o n t h e g r o u n d s o f " c o m m o n s e n se " t h a t " t h e r e a r e in n u m e r a b l e o r d e r s o f i n te l l ig e n t b e i n g

m o r e h a p p y a n d m o r e p e r f e c t t h a n m a n " J 6 J .H . L a m b e r t , in h is Cosmologiscbe Brie fe o f 1 7 5 1 , a l s o

f e l t t h a t t h e e x i s t e n c e o f e x t r a t e r r e s t r i a l s w a s o b v io u s .~ 7 W h e n B o d e t r a n s l a t e d F o n t e n e l l e ' s

Ent re t i e ns

i n t o G e r m a n , h e l e f t n o d o u b t t h a t h e u n d e r t o o k t h e t a s k in a s c i e n t if i c r a t h e r t h a n a

l i t e r a r y f r a m e o f m i n d . T h e p a s s ag e in w h i c h F o n t e n e l l e d e s c r i b e s th e e x t r e m e l i v e li n e ss o f t h e

i n h a b i t a n t s o f V e n u s c a l le d f o r t h t h e f o l l o w i n g c o m m e n t : " P e c u l i a r [ O n e f i n d s r a t h e r w i t h u s h e r e

[ in B e rl in ] t h a t t o o m u c h h e a t m a k e s t h e m i n d m o r e s l e e p y a n d l a z y r a t h e r t h a n l i v e l y " ) s

K a n t w a s c o n v i n c e d t h a t t h e p l a n e t s w e r e p o p u l a t e d a n d h e d e s c r i b e d t h e c h a r a c t e r i s t ic s o f t h e

v a r i o u s p l a n e t a r y r a c e s a s c o n d i t i o n e d b y t h e i r r e la t i v e p o s i t i o n . A s t h e v a r i o u s r a c e s o f m a n k i n d h a v e

t h e i r p h y s i c a l a n d m e n t a l c h a r a c t e r i s t ic s m o u l d e d b y t h e i r g e o g r a p h i c a l e n v i r o n m e n t s o t h e m o r a l a n d

i n t e l l e c t u a l c h a r a c t e r i s t i c s o f t h e v a r i o u s p l a n e t a r y b e i n g s a re d e t e r m i n e d b y t h e i r d i s t a n c e f r o m t h e

S u n .

K a n t w a s i n c l i n e d t o se e k t h e m o s t p e r f e c t c l as s es o f r a t i o n a l b e i n g s fa r a w a y f r o m t h e c e n t r e o f

t h e s o l a r s y s t e m s i n c e i t is l i k e l y t h a t t h e m a t t e r o f t h e o u t e r p l a n e t s is li g h t e r a n d f i n e r a n d w o u l d

p r o v e l es s o f a h i n d r a n c e t o t h e a c t i v it i e s o f t h e s o u l . I n t h e t h i r d p a r t o f h is

Universal Natura l His tory

a n d T h e o r y o f t b e H e a v e n s ( u n a c c o u n t a b l y o m i t t e d f r o m t h e E n g l is h t r a n s la t i o n ) h e ev e n su g g e s ts

t h a t N e w t o n w o u l d b e l o o k e d u p o n a s a n a p e o n J u p i t e r o r w o r s e s ti ll o n S a t u r n . 19

B u t w h i l e a c o m m u n i t y o f n a t io n s , a l b e i t o f v a r y i n g m o r a l a n d i n t e l l e c t u a l a p t i t u d e s , w a s b e i n g

p o s t u l a t e d , t h e p l a n e t s t h e m s e l v e s w e r e m o v i n g a p a r t a t a t r e m e n d o u s p a c e a s e a c h s u c c e s si v e ly m o r e

p r e c i se d e t e r m i n a t i o n i n c r e a s e d t h e s i ze o f t h e s o l a r s y s te m .

O n e o f t h e a d v a n t a g e s o f t h e C o p e r n i c a n s y s t e m w a s th e r e m a r k a b l y a c c u r a t e d e t e r m i n a t i o n o f

t h e r e l a ti v e p l a n e t a r y d i s t a n c e s as ca n b e s ee n w h e n t h e y a r e c o m p a r e d w i t h t h e m o d e r n d a t a g iv e n in

p a r e n t h e s e s : 0 . 3 7 ( 0 . 3 8 ) , 0 .7 2 ( 0 . 7 2 ) , 1 . 5 2 ( 1 .5 2 ) , 5 . 2 2 ( 5 . 2 0 ), 9 . 1 7 ( 9 .5 4 ) . T h e i m p o r t a n c e o f s u c h

r e l a ti v e s p a c i n g w as b r o u g h t o u t i n K e p l e r ' s T h i r d L a w c o n n e c t i n g t h e p e r i o d s a n d m e a n d i s t a n c e s o f

t h e p l a n e t s . K e p l e r w as e a g e r t o p o i n t o u t h o w s u i t a b l e i t w a s t o u s e t h e E a r t h - S u n d i s t a n c e a s t h e

m e a s u r i n g r o d o f t h e U n i v e r s e b u t , h o w e v e r a p p r o p r i a t e , t h e m e a s u r i n g - r o d c o u l d n o t b e g i n to c o n v e y

t h e g r a n d i o s e d i m e n s i o n s o f t h e s o l a r s y s t e m u n t i l i ts l e n g t h h a d b e e n d e t e r m i n e d . T h i s w a s n o t

a c h i e v e d w i t h r e a s o n a b l e a c c u r a c y u n t i l a b o u t 4 0 y e a r s a f t e r K e p l e r ' s d e a t h w h e n , i n 1 6 7 2 , R i c h e r a n d

P i c a r d m e a s u r e d t h e p a r a l l a x o f M a r s. T h e v a l u e o f t h e p a r a l l a x o f M a r s y i e l d e d o n l y i ts d is t a n c e , b u t b y

K e p l e r ' s T h i r d L a w t h e d i s t a n c e s o f al l t h e o t h e r p l a n e t s f o l lo w e d r e a d i l y , a n d s o t h e r i c h l y e n d o w e d

i n h a b i t a n t s o f S a t u r n a t t h e o u t e r l i m i ts o f t h e so l a r s y s t e m , t u r n e d o u t t o b e n o t a t 2 0 , 0 0 0 b u t a t

2 0 0 , 0 0 0 E a r t h - r a d i i .


4/5

14 WILLIAM R. SHEA

If the solar system had increased tenfold, the stars had receded even more. But by how much?

Kepler had offered 60 million Earth-radii for the distance of the fixed stars, a value that he obtained

from geome try rather than observation, namely by assuming that the or bit of Saturn was a geo -

metrical mean betw een the di ameter of the Sun and the diam eter of the spheres of fixed stars. 20 Bold

as this conjectur e of 60 million Earth-radii was, it represents only 1 of the correct value for the

nearest stars.

Huygens arrived at a much larger value by assuming that the Sun and Sirius were similar stars

and looking through various holes until he found one through which the Sun appeared with a bright-

ness equal to Sirius. This gave him a distance for Sirius of 27,664 astrono mical units, and to bring

the enormi ty of this home to his readers he explained that a bullet that took 25 years to cover the

distance to the Sun from t he Earth w ould have to travel some 700 ,000 years to reach Sirius. 21 And

yet the value suggested by Huygens falls short of the correct value by a factor of about 18.

The frontiers of the cosmos had been pushed well beyond the limits of the sphere of fixed stars

and even the central position of the Sun, to which Copernicus and Kepler paid an almost religious

homage, began to look arbitrary. New ton spoke of his law of gravitati on as requiring an infinite

amount of matter distributed in infinite space, lest the attraction should pull all matter into one huge

bulk. But the starry sky showed anything but unif orm ity. This appeared as a challenge to Thom as

Wright of Durham who could not believe that God had strewn the stars across the heavens carelessly.

Wright suggested that the disorderly distribution was merely apparent and that it arose from the

Earth's position near the centre of the Milky Way, a vast assemblage of separate stars moving in the

same direct ion and in approxi mate ly the same plane. 22

The next step was taken by Kant who happened to read in 1751 in the Hamburg journal, Freie

UrteiIe

an essay review of Wright's book. Fou r years later in his

Universal Natural His tory and

The ory o f t he He av ens

Kant argued that the luminous patches long observed in the heavens were dis-

tinct Milky Ways, and that they appeared circular or elliptical according to their position with respect

to the earth. Kant saw in this a manif estat ion of the Creator 's wisdom and power and he conclude d

that the countless number of Milky Ways must be grouped in a hierarchical system.

Hence by the second half of the eighteenth century, thanks to this philosphical yeast, the notion

that stars are grouped in disc-like systems was willingly entert ained. To su bstantiate such a view,

however, systematic observations and measurements were indispensable, and neither Wright nor Kant

att empt ed t o supply them. This giant step was left to William Herschel, for in spite of popular specu-

lation about infinite worlds and countless Milky Ways, the starry sky was for the practical astronomer

what it had been fo r the Greeks: a huge, concave, spherical surface with a fixed radius. As Herschel

put it in 1784:

Hitherto the sidereal heavens have, not inadequately for the purpose designed, been represented by the

concave surface of a sphere, in the center of which the eye of an observer might be supposed to be placed...

In future, therefore, we shall look upon those regions into which we may now penetrate by means of such

large telescopes, as a naturalist regards a rich extent of ground or chain of mountains, containing strata vari-

ously inclined and directed, as well as consisting of very different material. A surface of a globe or map,

therefore, will but ill delineate the interior parts of the heavens.23

Herschel had set himself a colossal task, and he pursued it with remar kable assiduity. His

catalogues published in 1786, 1789, and 1802 added over 2,500 nebulae to the 103 found in the pre-

vious list of Messier. This enabled him to establish that t he Ne wton ian assumpt ion of a uni for m star

distribution was not in keeping with the facts.

Herschel used a 20-foot telescope to determine the diameter of the Milky Way which he gave

as 6,000 light years (as against the present value of 80,000 light years) but when he began to use a

40-foot telescope he was led to a radical reappraisal:

In these ten observations the gages applied to the milky way were found to be arrested in their progress

by the extreme smallness and faintness of the stars; this can however leave no doubt of the progressive extent

of the starry regions; for when in one of the observations a faint nebulosity was suspected, the application of

a higher magnifying power evinced, that the doubtful appearance was owing to an inter-mixture of many

stars that were too minute to be distinctly perceived with the lower power; hence we may conclude, that

when our gages will no longer resolve the milky way into stars, it is not because its nature is ambiguous, but

because i t is fathomless. 24


5/5

S o m e a s p e c ts o f p o s t - R e n a i s s a n c e a s t r o n o m y 1 5

B y t h e e n d o f o u r p e r i o d , t h e r e f o r e , t h e u l t i m a t e f r o n t i e r s o f t h e u n iv e r s e e lu d e d m e n a n e w

a n d a s t r o n o m e r s w e r e l a u n c h e d o n c e a g a i n o n t h e i r q u e s t f o r t h e e v e r - r e c e d in g h o r i z o n s o f t h e u n i -

v e r s e ,

N O T E S A N D R E F E R E N C E S

1. Ch r i s to ph er Clavius, Com m e n tar lum in Sphae ram J oann i s de Sac ro Bosc o in Opera Omnia , Ma i nz , 1611 ,

vol . III , p. 75.

2 . F r a nc e s c o S i z z i, Dianoia Astronomica, Opt ica , Pbysica ( V e n i c e , 1611 ) i n G a l i le o G a l i le i , Opere (ed . A.

Fa va r o ) , F l o r e nc e : B a r b6 r a , 1890- 1909 , vo l . I I I , p . 214 .

3. G.W .F. Hegel , Dissertat io Phi losophica de Orbi ti s Plane tarum in Sa 'mt l iche Werke ( e d . H . G l oc kne r ) ,

S t u t t ga r t : F r o m m a rt s V e r l a g , 1927 , vo l . I, p . 28 . I t is on l y f a i r t o no t e t ha t H e ge l ' s r e f e r e nc e t o t he s e r ie s

a t t r i b u t e d t o t h e D e m i u r g e (T im ae us 3 6 ) i s n o t w i t h o u t i r o n y .

4. G.W .F. Hegel ,

Phi lo sophy o f Na ture,

t r a ns , by M. J . Pe r r y , 3 vo ls . Lond on : A l l e n & U nw i n , 1 970 , vo l . I ,

p . 281 .

5 . C ope r n i c us ,

O n tbe Re v o lu t ions o f tbe H e av e n ly Spbe re s ,

t r a n s, b y C h a r l e s G l e n n W a ll is [ G r e a t B o o k s o f

t he We s t e r n Wor l d , vo l . 16 ] . C h i c a go : Enc y c l opa e d i a B r i t a nn i c a , 1952 , p . 529 .

6 . Gal i l eo , D ialogue Conc e rn ing the Tw o Ch ie f Wor ld Sy s t e m s , t r a ns , by S t i l l m a n D r a ke . B e r ke l e y : U n i ve r s i t y

of Cal i fornia Press, 1 962 , p . 367.

7 . " Q u a e s o la c o g it a t io , n e s ci o q u i d h o r r o r i s o c c u l t i p r a e se f e r t ; d u m e r r a r e s e se q u i s d e p r e h e n d i t in h o c

i m m e n s o " . ( K e p l e r , De Ste l la Nov a in Pede Serpentari i [ 1 6 0 6 ] i n G e sam m e l t e We rk e ( e d . Ma x C a s pa r ) ,

18 vo l. t o da t e , M un i c h : G .H . B e c k ' s c he V e da g , 1938- , vo l . I, p . 25 ) .

8 . Gal i l eo , Sidereus Nuncius ( 1 6 1 0 ) i n Discoveries and Opinion s o f Gal ileo, t r a n s, b y S t i l lm a n D r a k e , G a r d e n

C i t y, N . Y .: D o u b l e d a y A n c h o r B o o k s , 1 9 5 7 , p . 3 1 .

9. Ibid., p. 36.

1 0 . L e t t e r o f C i a m p o l i t o G a l il e o , 2 8 F e b r u a r y 1 6 1 4 , i n

Discoveries and Opinion s o f Gal ileo,

t r a ns , by S t i l l m a n

D r a k e , G a r d e n C i ty , N . Y . : D o u b l e d a y A n c h o r B o o k s, 1 9 5 7 , p . 1 5 8 .

11. Kepler , Dissertatio cure Nuncio Sidereo, c r i t i c a l e d i t i on a n d no t e s by E . Pa s o li a nd G . Ta ba r r on i . Tu r i n :

B o t t e g a d ' E r a s m o , 1 9 7 2 , p . 6 0 . K e p l e r ta k e s u p t h e q u e s t i o n o f p l a n e t a r y v o y a g e s i n h i s p o s t h u m o u s

S o m n i u m . . D e A s t r o n o m i a L u n a r i . F r a n k f u r t , 1 6 3 4 . S e e a ls o J o h n W i l ki n s, T h e D i s c o ve r y o f a N e w W o r l d

[ 1 6 3 8 ] f o r p o s si b l e m o d e s o f c o n v e y a n c e t o t h e m o o n ( J o h n W i l ki n s, Mathe m a t i c a l and Ph i lo sophic a l

Works. L o n d o n , 1 7 0 8 , p p . 1 1 3 - 1 3 5 ) .

12. Pier re Bore l , Discours nouve aux pro uvan t la p lural i te des mond es, que les astres son t des terres habitues.

Par i s , 1657.

1 3 . J o h n R a y , The Wisdom o f G od Man i f e s t e d in t be W ork s o f Cre at ion , 3r d e d i t i on , London , 1708 , p . 6 .

14 . Fon t e ne l l e , En tretiens su r la pluralit des mondes . Edi t i o n c r i t i que e t no t e s pa r A . C a i a m e . Pa r i s: Ma r c e l

Didier , 1966, p . 105 .

15 . C hr i s t i a n H uyge ns , C o s m o t b e o r e o s [ 1 6 9 8 ] i n Oeuvres Comple tes 22 vo l s. i n 23 . La H a ye : M a r t i nus N i j ho f f ,

1 8 8 8 - - 1 9 5 0 , v o l. 2 1, p p . 6 8 1 - 7 6 3 .

16 . G e n go B e r ke l e y ,

Alc ipbron ,

i n Wor ks ( e ds. A .A . Luc e a nd T .E . J e s s op ) 9 vo l s. Ed i n bur g h : Ed i n bur g h

U ni ve r s i t y P r es s, 1 94 8- 19 57 , vo l . I I I, p . 172 .

1 7 . J . H . L a m b e r t ,

Cosm ologiscbe Briefe .

A ugs bur g , 1751 , p . 63 .

18 . C i t e d i n S t a n l e y J a k i ,

The R elevance o f Physics.

C hi c a go : C h i c a go U n i ve r s i t y P re ss ,

1966, p . 199.

1 9 . I m m a n u e l K a n t , We rk e ( e d . Wi l he l m We i s c he de l ) 6 vo ls . Wi e s ba de n : I n s e l- V e r l ag , 1960 , vol. I , p. 387.

20. Kepler , Epi to m e As t ron om ic ae Copern ic anae L ibe r Q uar tu s [ 1 6 2 0 ] , i n Werke, vol . VII , p . 286.

21 . H uyge ns , i n Oeuvres Comple tes, 2 2 v o ls i n 2 3 . L a H a y e : M a r t i n u s N i j h o f f , 1 8 8 8 - 1 9 5 0 , v o l. 2 1 ,

p p. 8 1 4 - 8 1 7 .

2 2 . T h o m a s W r i g h t, O rig ina l The or y o r Ne w H y po the s i s o f t he U n iv e rse , L o n d o n , 1 7 5 0 .

2 3 , W i l li a m H e r s ch e l , " A n A c c o u n t o f s o m e O b s e r v a t i o n s T e n d i n g t o I n v e st i g a te t h e C o n s t r u c t i o n o f t h e

H e a ve ns " , Phil. Trans. R. Soc. 74 , p . 438 ( 1784) .

2 4 , W i l li am H e r s ch e l , " A s t r o n o m i c a l O b s e r v a t i o n s a n d E x p e r i m e n t s , se l e c t ed f o r t h e p u r p o s e o f a s c e r t a i n in g

t h e r e l a t iv e d i s t a n c e s o f c l u s te r s o f s ta r s , a n d o f i n v e s t ig a t i n g h o w f a r t h e p o w e r o f o u r t e l e s c o p e s m a y b e

e x p e c t e d t o r e a c h i n t o s p a c e , w h e n d i r e c t e d t o a m b i g u o u s c e l e s ti a l o b j e c t s " , Phil. Trans, R. Soc. 1 0 8 , 4 6 3

( 1 8 1 8 ) .

vistas in astronomy volume 20 issue part-p1 1976 [doi 10.1016%2f0083-6656%2876%2990005-2] william r....

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