天文学中“日心说”与“地心说”之争

地心说与日心说
地心说是长期盛行于古代欧洲的宇宙学说。它最初由古希腊学者欧多克斯提出，后经亚里多德、托勒密进一步发展而逐渐建立和完善起来。
托勒密认为，地球处于宇宙中心静止不动。从地球向外，依次有月球、水星、金星、太阳、火星、木星和土星，在各自的圆轨道上绕地球运转。其中，行星的运动要比太阳、月球复杂些：行星在本轮上运动，而本轮又沿均轮绕地运行。在太阳、月球行星之外，是镶嵌着所有恒星的天球——恒星天。再外面，是推动天体运动的原动天。下面是这种学说的示意图：
地心说是世界上第一个行星体系模型。尽管它把地球当作宇宙中心是错误的，然而它的历史功绩不应抹杀。地心说承认地球是“球形”的，并把行星从恒星中区别出来，着眼于探索和揭示行星的运动规律，这标志着人类对宇宙认识的一大进步。地心说最重要的成就是运用数学计算行星的运行，托勒密还第一次提出“运行轨道”的概念，设计出了一个本轮均轮模型。按照这个模型，人们能够对行星的运动进行定量计算，推测行星所在的位置，这是一个了不起的创造。在一定时期里，依据这个模型可以在一定程度上正确地预测天象，因而在生产实践中也起过一定的作用。
地心说中的本轮均轮模型，毕竟是托勒密根据有限的观察资料拼凑出来的，他是通过人为地规定本轮、均轮的大小及行星运行速度，才使这个模型和实测结果取得一致。但是，到了中世纪后期，随着观察仪器的不断改进，行星位置和运动的测量越来越精确，观测到的行星实际位置同这个模型的计算结果的偏差，就逐渐显露出来了。
但是，信奉地心说的人们并没有认识到这是由于地心说本身的错误造成的，却用增加本轮的办法来补救地心说。当初这种办法还能勉强应付，后来小本轮增加到80多个，但仍不能满意地计算出行星的准确位置。这不能不使人怀疑地心说的正确性了。到了16世纪，哥白尼在持日心地动观的古希腊先辈和同时代学者的基础上，终于创立了“日心说”。从此，地心说便逐渐被淘汰了。
日心说:认为太阳是宇宙的中心，地球和其他行星都绕太阳转动，日心说又称为“日心地动说”或“日心体系”。十六世纪，波兰天文学家哥白尼经过近四十年的辛勤研究，在分析过去的大量资料和自己长期观测的基础上，于1543年出版的《天体运行论》中，系统地提出了日心说。在托勒密的地心体系中，每个行星运动都含一年周期成分，但托勒密对此无法作出合理的解释。哥白尼认为，地球不是宇宙的中心，而是一颗普通行星，太阳才是宇宙的中心，行星运动的一年周期是地球每年绕太阳公转一周的反映。哥白尼体系另一些内容是：
①水星、金星、火星、木星、土星五颗行星和地球一样，都在圆形轨道上匀速率地绕太阳公转。
②月球是地球的卫星，它在以地球为中心的圆轨道上，每月绕地球转一周，同时跟地球一起绕太阳公转。
③地球每天自转一周，天穹实际上不转动，因地球自转才出现日月星辰每天东升西落的现象。
④恒星和太阳间的距离十分遥远，比日地间的距离要大得多。哥白尼曾列举了许多主张地球自转和行星绕太阳公转的古代学者名字，他发扬了这些学者的思想，竭尽毕生精力，经过艰辛的观测和数学计算，以严格的科学论据建立了日心体系。后来的观测事实不断地证实并发展了这一学说。
限于当时的科学发展水平，哥白尼的日心说也有缺点和错误，这就是：
①认为太阳是宇宙的中心，实际上，太阳只是太阳系中的一个中心天体，不是宇宙的中心；
②沿用了行星在圆轨道作匀速圆周运动的旧观念，实际上行星轨道是椭圆的，运动速度的大小也不是恒定的。

马克思《青年在选择职业时的考虑》英文版

Reflections of a Young Man
on The Choice of a Profession
Source: MECW Volume 1
Written: between August 10 and 16, 1835
First published: in Archiv für die Geschichte des Sozialismus und der Arbeiterbewegung, 1925
Translated from the Latin.
Transcribed: by Sally Ryan.
Nature herself has determined the sphere of activity in which the animal should move, and it peacefully moves within
that sphere, without attempting to go beyond it, without even an inkling of any other. To man, too, the Deity gave a
general aim, that of ennobling mankind and himself, but he left it to man to seek the means by which this aim can be
achieved; he left it to him to choose the position in society most suited to him, from which he can best uplift himself
and society.
This choice is a great privilege of man over the rest of creation, but at the same time it is an act which can destroy his
whole life, frustrate all his plans, and make him unhappy. Serious consideration of this choice, therefore, is certainly
the first duty of a young man who is beginning his career and does not want to leave his most important affairs to
chance.
Everyone has an aim in view, which to him at least seems great, and actually is so if the deepest conviction, the
innermost voice of the heart declares it so, for the Deity never leaves mortal man wholly without a guide; he speaks
softly but with certainty.
But this voice can easily be drowned, and what we took for inspiration can be the product of the moment, which
another moment can perhaps also destroy. Our imagination, perhaps, is set on fire, our emotions excited, phantoms
flit before our eyes, and we plunge headlong into what impetuous instinct suggests, which we imagine the Deity
himself has pointed out to us. But what we ardently embrace soon repels us and we see our whole existence in ruins.
We must therefore seriously examine whether we have really been inspired in our choice of a profession, whether an
inner voice approves it, or whether this inspiration is a delusion, and what we took to be a call from the Deity was
self-deception. But how can we recognise this except by tracing the source of the inspiration itself?
What is great glitters, its glitter arouses ambition, and ambition can easily have produced the inspiration, or what we
took for inspiration; but reason can no longer restrain the man who is tempted by the demon of ambition, and he
plunges headlong into what impetuous instinct suggests: he no longer chooses his position in life, instead it is
determined by chance and illusion.
Nor are we called upon to adopt the position which offers us the most brilliant opportunities; that is not the one which,
in the long series of years in which we may perhaps hold it, will never tire us, never dampen our zeal, never let our
enthusiasm grow cold, but one in which we shall soon see our wishes unfulfilled, our ideas unsatisfied, and we shall
inveigh against the Deity and curse mankind.
But it is not only ambition which can arouse sudden enthusiasm for a particular profession; we may perhaps have
embellished it in our imagination, and embellished it so that it appears the highest that life can offer. We have not
analysed it, not considered the whole burden, the great responsibility it imposes on us; we have seen it only from a
distance, and distance is deceptive.
Our own reason cannot be counsellor here; for it is supported neither by experience nor by profound observation,
being deceived by emotion and blinded by fantasy. To whom then should we turn our eyes? Who should support us
where our reason forsakes us?
Our parents, who have already travelled lifes road and experienced the severity of fate - our heart tells us.
And if then our enthusiasm still persists, if we still continue to love a profession and believe ourselves called to it after
we have examined it in cold blood, after we have perceived its burdens and become acquainted with its difficulties,
then we ought to adopt it, then neither does our enthusiasm deceive us nor does overhastiness carry us away.
But we cannot always attain the position to which we believe we are called; our relations in society have to some
extent already begun to be established before we are in a position to determine them.
Our physical constitution itself is often a threatening obstacle, and let no one scoff at its rights.
It is true that we can rise above it; but then our downfall is all the more rapid, for then we are venturing to build on
crumbling ruins, then our whole life is an unhappy struggle between the mental and the bodily principle. But he who is
unable to reconcile the warring elements within himself, how can he resist lifes tempestuous stress, how can he act
calmly? And it is from calm alone that great and fine deeds can arise; it is the only soil in which ripe fruits successfully
develop.
Although we cannot work for long and seldom happily with a physical constitution which is not suited to our
profession, the thought nevertheless continually arises of sacrificing our well-being to duty, of acting vigorously
although we are weak. But if we have chosen a profession for which we do not possess the talent, we can never
exercise it worthily, we shall soon realise with shame our own incapacity and tell ourselves that we are useless
created beings, members of society who are incapable of fulfilling their vocation. Then the most natural consequence
is self-contempt, and what feeling is more painful and less capable of being made up for by all that the outside world
has to offer? Self-contempt is a serpent that ever gnaws at ones breast, sucking the life-blood from ones heart and
mixing it with the poison of misanthropy and despair.
An illusion about our talents for a profession which we have closely examined is a fault which takes its revenge on us
ourselves, and even if it does not meet with the censure of the outside world it gives rise to more terrible pain in our
hearts than such censure could inflict.
If we have considered all this, and if the conditions of our life permit us to choose any profession we like, we may
adopt the one that assures us the greatest worth, one which is based on ideas of whose truth we are thoroughly
convinced, which offers us the widest scope to work for mankind, and for ourselves to approach closer to the general
aim for which every profession is but a means - perfection.
Worth is that which most of all uplifts a man, which imparts a higher nobility to his actions and all his endeavours,
which makes him invulnerable, admired by the crowd and raised above it.
But worth can be assured only by a profession in which we are not servile tools, but in which we act independently in
our own sphere. It can be assured only by a profession that does not demand reprehensible acts, even if
reprehensible only in outward appearance, a profession which the best can follow with noble pride. A profession
which assures this in the greatest degree is not always the highest, but is always the most to be preferred.
But just as a profession which gives us no assurance of worth degrades us, we shall as surely succumb under the
burdens of one which is based on ideas that we later recognise to be false.
There we have no recourse but to self-deception, and what a desperate salvation is that which is obtained by selfbetrayal!
Those professions which are not so much involved in life itself as concerned with abstract truths are the most
dangerous for the young man whose principles are not yet firm and whose convictions are not yet strong and
unshakeable. At the same time these professions may seem to be the most exalted if they have taken deep root in
our hearts and if we are capable of sacrificing our lives and all endeavours for the ideas which prevail in them.
They can bestow happiness on the man who has a vocation for them, but they destroy him who adopts them rashly,
without reflection, yielding to the impulse of the moment.
On the other hand, the high regard we have for the ideas on which our profession is based gives us a higher standing
in society, enhances our own worth, and makes our actions un-challengeable.
One who chooses a profession he values highly will shudder at the idea of being unworthy of it; he will act nobly if only
because his position in society is a noble one.
But the chief guide which must direct us in the choice of a profession is the welfare of mankind and our own
perfection. It should not be thought that these two interests could be in conflict, that one would have to destroy the
other; on the contrary, mans nature is so constituted that he can attain his own perfection only by working for the
perfection, for the good, of his fellow men.
If he works only for himself, he may perhaps become a famous man of learning, a great sage, an excellent poet, but
he can never be a perfect, truly great man.
History calls those men the greatest who have ennobled themselves by working for the common good; experience
acclaims as happiest the man who has made the greatest number of people happy; religion itself teaches us that the
ideal being whom all strive to copy sacrificed himself for the sake of mankind, and who would dare to set at nought
such judgments?
If we have chosen the position in life in which we can most of all work for mankind, no burdens can bow us down,
because they are sacrifices for the benefit of all; then we shall experience no petty, limited, selfish joy, but our
happiness will belong to millions, our deeds will live on quietly but perpetually at work, and over our ashes will be shed
the hot tears of noble people.