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is directly related to the semimajor axis a） might be much less affected by perturbing plas than is the angular momentum exchange （which relates to e）。 Hence， the eccentricities of Venus and Earth can be disturbed easily by Jupiter and Saturn， which results in a positive rrelation in the angular momentum exchange。 On the other hand， the semimajor axes of Venus and Earth are less likely to be disturbed by the jovian plas。 Thus the energy exchange may be limited only within the Venus–Earth pair， which results in a negative rrelation in the exchange of orbital energy in the pair。
As for the outer jovian plaary subsystem， Jupiter–Saturn and Uranus–Neptune seem to make dynamical pairs。 However， the strength of their upling is not as strong pared with that of the Venus–Earth pair。
5 ± 5 × 1010…yr integrations of outer plaary orbits
Since the jovian plaary masses are much larger than the terrestrial plaary masses， we treat the jovian plaary system as an independent plaary system in terms of the study of its dynamical stability。 Hence， we added a uple of trial integrations that span ± 5 × 1010 yr， including only the outer five plas （the four jovian plas plus Pluto）。 The results exhibit the rigorous stability of the outer plaary system over this long time…span。 Orbital nfigurations （Fig。 12）， and variation of eccentricities and inclinations （Fig。 13） show this very long…term stability of the outer five plas in both the time and the frequency domains。 Although we do not show maps here， the typical frequency of the orbital oscillation of Pluto and the other outer plas is almost nstant during these very long…term integration periods， which is demonstrated in the time–frequency maps on our webpage。
In these two integrations， the relative numerical error in the total energy was ～10？6 and that of the total angular momentum was ～10？10。
5。1 Resonances in the Neptune–Pluto system
Kinoshita &；amp； Nakai （1996） integrated the outer five plaary orbits over ± 5。5 × 109 yr 。 They found that four major resonances between Neptune and Pluto are maintained during the whole integration period， and that the resonances may be the main causes of the stability of the orbit of Pluto。 The major four resonances found in previous research are as follows。 In the following description，λ denotes the mean longitude，Ω is the longitude of the ascending node and ？ is the longitude of perihelion。 Subscripts P and N denote Pluto and Neptune。
Mean motion resonance between Neptune and Pluto （3：2）。 The critical argument θ1= 3 λP？ 2 λN？？P librates around 180° with an amplitude of about 80° and a libration period of about 2 × 104 yr。
The argument of perihelion of Pluto ωP=θ2=？P？ΩP librates around 90° with a period of about 3。8 × 106 yr。 The dominant periodic variations of the eccentricity and inclination of Pluto are synchronized with the libration of its argument of perihelion。 This is anticipated in the secular perturbation theory nstructed by Kozai （1962）。
The longitude of the node of Pluto referred to the longitude of the node of Neptune，θ3=ΩP？ΩN， circulates and the period of this circulation is equal to the period of θ2 libration。 When θ3 bees zero， i。e。 the longitudes of ascending nodes of Neptune and Pluto overlap， the inclination of Pluto bees maximum， the eccentricity bees minimum and the argument of perihelion bees 90°。 When θ3 bees 180°， the inclination of Pluto bees minimum， the eccentricity bees maximum and the argument of perihelion bees 90° again。 Williams &；amp； Benson （1971） anticipated this type of resonance， later nfirmed by Milani， Nobili &；amp； Carpino （1989）。
An argument θ4=？P？？N＋ 3 （ΩP？ΩN） librates around 180° with a long period，～ 5。7 × 108 yr。
In our numerical integrations， the resonances （i）–（iii） are well maintained， and variation of the critical arguments θ1，θ2，θ3 remain similar during the whole integration period （Figs 14–16 ）。 However， the fourth resonance （iv） appears to be different： the critical argument θ4 alternates libration and circulation over a 1010…yr time…scale （Fig。 17）。 This is an interesting fact that Kinoshita &；amp； Nakai's （1995， 1996） shorter integrations were not able to disclose。
6 Discussion
What kind of dynamical mechanism maintains this long…term stability of the plaary system？ We can immediately think of two major features that may be responsible for the long…term stability。 First， there seem to be no significant lower…order resonances （mean motion and secular） between any pair among the nine plas。 Jupiter and Saturn are close to a 5：2 mean motion resonance （the famous ‘great inequality’）， but not just in the resonance zone。 Higher…order resonances may cause the chaotic nature of the plaary dynamical motion， but they are not so strong as to destroy the stable plaary motion within the lifetime of the real Solar system。 The send feature， which we think is more important for the long…term stability of our plaary system， is the difference in dynamical distance between terrestrial and jovian plaary subsystems （Ito &；amp； Tanikawa 1999， 2001）。 When we measure plaary separations by the mutual Hill radii （R_）， separations among terrestrial plas are greater than 26RH， whereas those among jovian plas are less than 14RH。 This difference is directly related to the difference between dynamical features of terrestrial and jovian plas。 Terrestrial plas have smaller masses， shorter orbital periods and wider dynamical separation。 They are strongly perturbed by jovian plas that have larger masses， longer orbital periods and narrower dynamical separation。 Jovian plas are not perturbed by any other massive bodies。
The present terrestrial plaary system is still being disturbed by the massive jovian plas。 However， the wide separation and mutual interaction among the terrestrial plas renders the disturbance ineffective； the degree of disturbance by jovian plas is O（eJ）（order of magnitude of the eccentricity of Jupiter）， since the disturbance caused by jovian plas is a forced oscillation having an amplitude of O（eJ）。 Heightening of eccentricity， for example O（eJ）～0。05， is far from sufficient to provoke instability in the terrestrial plas having such a wide separation as 26RH。 Thus we assume that the present wide dynamical separation among terrestrial plas （&；gt； 26RH） is probably one of the most significant nditions for maintaining the stability of the plaary system over a 109…yr time…span。 Our detailed analysis of the relationship between dynamical distance between plas and the instability time…scale of Solar system plaary motion is now on…going。
Although our numerical integrations span the lifetime of the Solar system， the number of integrations is far from sufficient to fill the initial phase space。 It is necessary to perform more and more numerical integrations to nfirm and examine in detail the long…term stability of our plaary dynamics。
——以上文段引自 Ito， T。&； Tanikawa， K。 Long…term integrations and stability of plaary orbits in our Solar System。 Mon。 Not。 R。 Astron。 Soc。 336， 483–500 （2002）
这只是作者君参考的一篇文章，关于太阳系的稳定性。
还有其他论文，不过也都是英文的，相关课题的中文文献很少，那些论文下载一篇要九美元（《Nature》真是暴利），作者君写这篇文章的时候已经回家，不在检测中心，所以没有数据库的使用权，下不起，就不贴上来了。
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第一百日（2）囤积粪便发家致富
唐跃坐在粪堆里，用剪刀剪开大便的真空包装，由于脱水和低温，袋中的粪便全部干燥而松脆，看上去坚硬，实际上轻轻一捣就会像沙子一样碎裂。
他长这么大也没想过自己此生会有幸与大便亲密接触，以往唐跃都是拉完提裤冲水走人，相当无情，从来不会回头看一眼。
唐跃把真空袋中的干燥粪便倒在铁盘子里，他甚至可以根据粪便中的食物残渣分辨出自己那天吃的是什么，许多富含粗纤维的食物在人的肠胃中得不到充分消化，会随着粪便一起排出来，唐跃有一阵子经常吃蔬菜罐头，那个时期的大便中就经常能看到未完全消化的植物纤维。
唐跃戴着两层口罩，好在这些大便都已经干燥了很长时间，没什么气味。
“粪便中的味道主要来自3…甲基吲哚，也就是粪臭素，这种东西如果沾在衣服上，那样你闻上去也会像一坨大便。”老猫坐在边上帮忙，它一边捣碎粪便一边碎碎念。
唐跃觉得它更大的兴趣在于粪便本身。
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