An introduction to astronomy: designed as a text-book for the use of students in college. By Denison Olmsted ...

130'HI': MOON.
227. Suppose the m1oon settintg o{it fiom the iquarter thlat
precedes tile conljtunction Awith at elocity that wtoutld make hler
describe an exact circle ronlnd the fearth the stin's action 1ltad
no neftct on her' since ler graxvity is imcicascd by that actioii,
slle i m1ust dlescenll toward te, tt ea rth:'t1(l luove witlhin that cii'cle. telr orbit then would be n orlf cr'vedt thanl it othlerwiso
would t1have been; bcaus(.-.e tthc itddition to helr gravity will
al<kle her fall frthler iat tthe cd of anl are below thle talngent
drtawn at thlie otlher e(l' d of'it. Ilcr' mot io'l ill be thus accelerated, and it will contillte to 1be accet crated untttil shte arrives
at tile elsuillg (onjunll ction, because thle direction of the sun's
action upon terl 1t'p,il tl at timle1, makes anIt acute atgle witlI
the direcctionl of lter mtotion. (See' tig. ft.) At the conitjICetion, lhc gravit2y toward tile etlrth being ditminisiled by the
actionl of the sill), her orbi't \will then be less cutlved, and asll
-w\ill be carrifed furtther flom thle earth as she moves to the next
quarter; 111d becautise the,cttion of thle s1t1 maltkes there an
o)ttlse tangle with the direction of
her lmotion, tshe will be retarded illn g. 8.
thee same degree as slhe was acceler- 1
ated befort.
228. After this qgcneral explalna- w t1r
tiot of t-he mode il Whl iell th et sun.
acnts; ai disturbing' frcee o11 thle mao-.. f
tions of thle mnoon, the learner will 0
bte prep(' (l to understand th}e math- \ -..s
cltiatical developmecnt of thte Asa A
doctri le. -
T.ht1crefore, lct AD)Bt3C (Fig. 48) be
the orbit, nearly cit'ular, illn wlich
the mlooll M revolves ill thle direction l( CA'\ l):I, roulnd tile earth 1 /.
Leta S bet tile sun, andl let SE, the
radiuss of thle earth's orbit, be takeln
to represent tle force with \whichll
the eart h gravitates to thle suIl.'"" tea (Art. 181) Sl; SJ t e force by.\.. iic..
the sunl d(rawl s thle 1 1oo ill thle direction TMS. liTake M:Gt::::