作者君在作品相关中其实已经解释过这个问题。
不过仍然有人质疑——“你说得太含糊了”，“火星轨道的变化比你想象要大得多！”
那好吧，既然作者君的简单解释不够有力，那咱们就看看严肃的东西，反正这本书写到现在，嚷嚷着本书bug一大堆，用初高中物理在书中挑刺的人也不少。
以下是文章内容：
long-teringunstablewhenacloseencounteroccurssoprehensive，butitseeputationprocesses.inrelationtothis，wisdoparetheseintegrationssipletedallthecalculations.seesection4.1forparedtheresultofourparethetestintegrationwiththeposedintofrequencycoponentperunitpletelylinear，theorbitalenergyandtheangularponentoftheinnerfourplanetscalculatedfroparedwiththoseoftheouterjovianplanets.anotherthingwenoticeisthattheinnerplanetarysubsysteeunstableparedwiththatofthevenus–earthpair.
5±5x1010-yrintegrationsofouterplanetaryorbits
sincethejovianplanetaryeszero，i.e.thelongitudesofascendingnodesofneptuneandplutooverlap，theinclinationofplutobecoeses90°.whenθ3becoeseses90°again.williams&bensonanticipatedthistypeofresonance，laterconfirmedbymilani，nobili&carpino.
anargumentθ4=?p??n+3libratesaround180°withalongperiod，～5.7x108yr.
inournumericalintegrations，theresonances–arewellmaintained，andvariationofthecriticalargumentsθ1，θ2，θ3remainsimilarduringthewholeintegrationperiod.however，thefourthresonanceappearstobedifferent:thecriticalargumentθ4alternateslibrationandcirculationovera1010-yrtime-scale.thisisaninterestingfactthatkinoshita&nakai'sshorterintegrationswerenotabletodisclose.