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死在火星上-第20部分

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  3。2 Time–frequency maps
  Although the plaary motion exhibits very long…term stability defined as the non…existence of close enunter events, the chaotic nature of plaary dynamics can change the oscillatory period and amplitude of plaary orbital motion gradually over such long time…spans。 Even such slight fluctuations of orbital variation in the frequency domain, particularly in the case of Earth, can potentially have a significant effect on its surface climate system through solar insolation variation (cf。 Berger 1988)。
  To give an overview of the long…term change in periodicity in plaary orbital motion, we performed many fast Fourier transformations (FFTs) along the time axis, and superposed the resulting periodgrams to draw two…dimensional time–frequency maps。 The specific approach to drawing these time–frequency maps in this paper is very simple – much simpler than the wavelet analysis or Laskar's (1990, 1993) frequency analysis。
  Divide the low…pass filtered orbital data into many fragments of the same length。 The length of each data segment should be a multiple of 2 in order to apply the FFT。
  Each fragment of the data has a large overlapping part: for example, when the ith data begins from t=ti and ends at t=ti+T, the next data segment ranges from ti+δT≤ti+δT+T, where δT?T。 We ntinue this division until we reach a certain number N by which tn+T reaches the total integration length。
  We apply an FFT to each of the data fragments, and obtain n frequency diagrams。
  In each frequency diagram obtained above, the strength of periodicity can be replaced by a grey…scale (or lour) chart。
  We perform the replacement, and nnect all the grey…scale (or lour) charts into one graph for each integration。 The horizontal axis of these new graphs should be the time, i。e。 the starting times of each fragment of data (ti, where i= 1,…, n)。 The vertical axis represents the period (or frequency) of the oscillation of orbital elements。
  We have adopted an FFT because of its overwhelming speed, since the amount of numerical data to be deposed into frequency ponents is terribly huge (several tens of Gbytes)。
  A typical example of the time–frequency map created by the above procedures is shown in a grey…scale diagram as Fig。 5, which shows the variation of periodicity in the eccentricity and inclination of Earth in N+2 integration。 In Fig。 5, the dark area shows that at the time indicated by the value on the abscissa, the periodicity indicated by the ordinate is stronger than in the lighter area around it。 We can regnize from this map that the periodicity of the eccentricity and inclination of Earth only changes slightly over the entire period vered by the N+2 integration。 This nearly regular trend is qualitatively the same in other integrations and for other plas, although typical frequencies differ pla by pla and element by element。
  4。2 Long…term exchange of orbital energy and angular momentum
  We calculate very long…periodic variation and exchange of plaary orbital energy and angular momentum using filtered Delaunay elements L, G, H。 G and H are equivalent to the plaary orbital angular momentum and its vertical ponent per unit mass。 L is related to the plaary orbital energy E per unit mass as E=?μ2/2L2。 If the system is pletely linear, the orbital energy and the angular momentum in each frequency bin must be nstant。 Non…linearity in the plaary system can cause an exchange of energy and angular momentum in the frequency domain。 The amplitude of the lowest…frequency oscillation should increase if the system is unstable and breaks down gradually。 However, such a symptom of instability is not prominent in our long…term integrations。
  In Fig。 7, the total orbital energy and angular momentum of the four inner plas and all nine plas are shown for integration N+2。 The upper three panels show the long…periodic variation of total energy (denoted asE… E0), total angular momentum ( G… G0), and the vertical ponent ( H… H0) of the inner four plas calculated from the low…pass filtered Delaunay elements。E0, G0, H0 denote the initial values of each quantity。 The absolute difference from the initial values is plotted in the panels。 The lower three panels in each figure showE…E0,G…G0 andH…H0 of the total of nine plas。 The fluctuation shown in the lower panels is virtually entirely a result of the massive jovian plas。
  paring the variations of energy and angular momentum of the inner four plas and all nine plas, it is apparent that the amplitudes of those of the inner plas are much smaller than those of all nine plas: the amplitudes of the outer five plas are much larger than those of the inner plas。 This does not mean that the inner terrestrial plaary subsystem is more stable than the outer one: this is simply a result of the relative smallness of the masses of the four terrestrial plas pared with those of the outer jovian plas。 Another thing we notice is that the inner plaary subsystem may bee unstable more rapidly than the outer one because of its shorter orbital time…scales。 This can be seen in the panels denoted asinner 4 in Fig。 7 where the longer…periodic and irregular oscillations are more apparent than in the panels denoted astotal 9。 Actually, the fluctuations in theinner 4 panels are to a large extent as a result of the orbital variation of the Mercury。 However, we cannot neglect the ntribution from other terrestrial plas, as we will see in subsequent sections。
  4。4 Long…term upling of several neighbouring pla pairs
  Let us see some individual variations of plaary orbital energy and angular momentum expressed by the low…pass filtered Delaunay elements。 Figs 10 and 11 show long…term evolution of the orbital energy of each pla and the angular momentum in N+1 and N?2 integrations。 We notice that some plas form apparent pairs in terms of orbital energy and angular momentum exchange。 In particular, Venus and Earth make a typical pair。 In the figures, they show negative rrelations in exchange of energy and positive rrelations in exchange of angular momentum。 The negative rrelation in exchange of orbital energy means that the two plas form a closed dynamical system in terms of the orbital energy。 The positive rrelation in exchange of angular momentum means that the two plas are simultaneously under certain long…term perturbations。 Candidates for perturbers are Jupiter and Saturn。 Also in Fig。 11, we can see that Mars shows a positive rrelation in the angular momentum variation to the Venus–Earth system。 Mercury exhibits certain negative rrelations in the angular momentum versus the Venus–Earth system, which seems to be a reaction caused by the nservation of angular momentum in the terrestrial plaary subsystem。
  It is not clear at the moment why the Venus–Earth pair exhibits a negative rrelation in energy exchange and a positive rrelation in angular momentum exchange。 We may possibly explain this through observing the general fact that there are no secular terms in plaary semimajor axes up to send…order perturbation theories (cf。 Brouwer &;amp; Clemence 1961; Boccaletti &;amp; Pucac 1998)。 This means that the plaary orbital energy (which 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。
  ………………………………
  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。
  “唐跃,你看这坨翔,这里面有个长长的东西……是蛔虫吗?啊不对,是未消化的纤维……”
  “唐跃,你这天吃的是不是蔬菜?我看到了菜叶子残渣,这是食物浪费你知道么?我觉得这些菜叶子挑出来还能吃。”
  “唐跃,你是不是肠胃功能和消化不太好呜呜呜呜呜……”
  唐跃拍了拍手,转过身来。
  他刚刚把一团卷起来的手套塞进了老猫的嘴里。
  总算消停了。
  “人畜粪便是一种非常传统的肥料,富含氮磷钾钙等元素,用来种植蔬菜非常合适,它们能给番茄提供足够的营养。”麦冬的声音在耳机响起,“唐跃,你需要把这些干燥的粪便进行复水,也就是加入水后充分搅拌,然后与取来的泥土进行混合。”
  进行复水……
  唐跃的额头上开始冒汗。
  虽然麦冬说得这么学术,但这个行为不就是……搅屎吗?
  唐跃看了一眼自己手中的铁钎子,一根棍子的用途取决于它在什么人手中,如果是在哈利波特手上,那么它就是一支高大上的魔杖,如果在唐跃手上……它就只能是一根搅屎棍。
  出身决定一切。
  唐跃让老猫去把上次冷凝的水端了过来,淡水具体应该用多大的量麦冬没有说明,她只描述说“加入的水要让粪便足够软化稀释,黏稠程度介乎于稀汤和浓粥之间,应该像一锅水分稍稍过量的咖喱。”
  “接着再把粪便加在基质泥土中,就像把咖喱浇在米饭上那样。”
  这个比喻真是无敌了。
  唐跃这辈子都不想吃咖喱饭了。
  由于是初步实验性质的种植,麦冬和唐跃都不准备把所有的番茄种子全部用光,如果不慎失败,那就完蛋了。唐跃决定第一批只种十株左右的番茄,以此来验证方案的可行性,等到有了百分之百的把握,再把剩下的蔬菜种子撒下去也不迟。
  所以泥土和粪便都是按照十株番茄的用量而准备的,唐跃手中还有不少大便……在荒芜的火星上,大便确实是一种有价值的稀缺资源。
  唐跃想象着火星上如果有一个原始的农耕文明,那么大便必然是抢手货,或许有人会通过收集囤积大便来发家致富。
  老猫和唐跃一人头上套了一个头盔,如临大敌。
  老猫手里端着水槽,水槽中盛着冰水。
  唐跃手中紧握着一根铁扦子,面前摆着一个大烧杯,烧杯中是深棕色的神秘粉末与块状物。
  “准备好了么?”老猫眼神坚毅。
  “准备好了。”唐跃点头。
  老猫倾斜水槽,把清水倒进烧杯中,杯中的粪便被冲开,清水立即变得浑浊起来,黑色残渣混合泡沫旋转着漂浮上来,水分被粪便迅速吸收,干燥的粉末大便重新变得粘稠起来,就像是一罐子稀泥,唐跃屏住呼吸,把手中的铁扦子插进大便中,开始奋力地搅拌起来。
  唐跃安慰自己是个快乐的掏粪工。
  “唐跃,你只要把它想象成黑芝麻糊就好了嘛。”麦冬说。
  唐跃和老猫都一窒。
  “姐姐我求你不要再说话了,你已经祸害了咖喱饭,请不要再祸害芝麻糊!”
  ·
  ·
  ·
  麦冬穿着蓝色的工作服,头上戴着一顶配套的帽子,漂浮在晶体号核心舱内,她面前的屏幕连通的是昆仑站的通讯系统,前后左右都是密密麻麻的控制面板。
  麦冬从来不敢关闭通讯系统,她担心昆仑站上的老猫和唐跃也会像地球那样,一觉醒来就消失不见了。
  只有看着那贱兮兮的一人一猫,麦冬才知道自己还活着。
  孤身一人在空间站内的生活是枯燥而乏味的,尽管宇宙大得漫无边际,但身处狭小的空间站内却会让人产生幽闭恐惧,晶体号核心舱是联合空间站中最大最宽敞的舱室,但来回也不过几个步长,其他的舱室不像是房间,更像是管道,圆柱体或者长方体的管道,穿行在这些管道间有种游历迷宫或者蚁穴的感觉。
  麦冬每天的生活很规律,体能训练,进食,检查空间站的工作,照顾植物样本,最后睡觉,她每天只睡五到六个小时,身在近地轨道上昼夜不分,所以麦冬常常失眠。
  所有的科研工作全部取消之后,腾出来的空闲时间女孩用来休息和娱乐,空间站内有很多音乐,电影和电子游戏,甚至还有一套索尼特供版PS10游戏主机,这台游戏机是老汤带过来的——每个宇航员都有一定的私人物品携带份额,除开必要的补给和科研用具,科考队员们被允许携带一定重量的个人用品,你可以带玩偶,带相册,甚至带黑胶唱片,只要不违反安全条例。
  为了在漫长的旅途中解乏,大多数人带的都是娱乐用品,比如十几个TB的电影和音乐——除了老麦这个二百五,他是个数学狂人,他带了一大摞草稿纸,宣称要在火星任务飞行途中攻克哥德巴赫猜想。
  当然,他上了船就把这个雄心壮志忘到脑后去了,快快乐乐地和老王开始打上古卷轴和使命召唤。
  麦冬不打游戏,她在空闲时间里就听音乐,看电影,空间站里有很多非常经典的老电影,女孩对好莱坞拍的那些光怪陆离的特效大片不感兴趣,自从地球消失之后,麦冬就在反复地看《乱世佳人》,《巴黎圣母院》以及BBC的纪录片,想象着那颗蔚蓝色的星球还在一亿公里之外。
  ………………………………
  第一百日(3)滑向深渊
  麦冬伸手按下面板上的按钮,电脑屏幕上弹出窗口“PSYCHOLOGICAL TES
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