hatkindofdynamicalmeismmaintainsthisloabilityoftheplaarysystem?weimmediatelythinkoftwomajorfeaturesthatmayberesponsiblefortheloability.first，thereseemtobenosignifitlower-orderresonances(meanmotionandsecular)betairamongthenineplas.jupiterandsaturnareclosetoa5:2meanmotionresohefamous‘greatinequality’)，butnotjustintheresonane.higher-orderresonancesmaycausethechaotiatureoftheplaarydynamicalmotion，buttheyarenotsastodestroythestableplaarymotionwithinthelifetimeoftherealsolarsystem.thesedfeature，whichwethinkismoreimportantfortheloabilityofourplaarysystem，isthedifferendynamicaldistaweenterrestrialandjovianplaarysubsystems(itotanikawa1999，2001).whenwemeasureplaaryseparationsbythemutualhillradii(r_)，separationsamongterrestrialplasaregreaterthan26rh，whereasthoseamongjovianplasarelessthan14rh.thisdifferenceisdirectlyrelatedtothediffereweendynamicalfeaturesofterrestrialandjovianplaerrestrialplashavesmallermasses，shorterorbitalperiodsandwiderdynamicalseparation.theyarestronglyperturbedbyjovianplahathavelargermasses，longerorbitalperiodsandnarrowerdynamicalseparation.jovianplasareurbedbyanyothermassivebodies.
thepresentterrestrialplaarysystemisstillbeingdisturbedbythemassivejovianplas.however，thewideseparationandmutualiionamoerrestrialplasrehedisturbaneffective;thedegreeofdisturbancebyjovianplasiso(ej)(orderofmagnitudeoftheetricityofjupiter)，sihedisturbancecausedbyjovianplasisaforcedoscillationhavinganamplitudeofo(ej).heighteningofetricity，forexampleo(ej)～0.05，isfarfromsuffittoprovokeinstabilityierrestrialplashavingsuchawideseparationas26rh.thusweassumethatthepresentwidedynamicalseparationamongterrestrialplas(;26rh)isprobablyohemostsignifitditionsformaintainiabilityoftheplaarysystemovera109-yrtime-span.ourdetailedanalysisoftherelationshipbetweendynamicaldistaweenplasaabilitytime-scaleofsolarsystemplaarymotionisnowon-going.
althoughournumeritegrationsspanthelifetimeofthesolarsystem，thenumberofiionsisfarfromsuffittofilltheinitialphasespace.itisnecessarytoperformmoreandmorenumeritegrationstofirmandexamineiailtheloabilityofourplaarydynamics.
——以上文段引自ito，t.tanikawa，k.long-termiionsandstabilityofplaaryorbitsinoursolarsystem.mon.not.r.astron.soc.336，483–500(2002)