登陆注册
14727000000008

第8章 PTOLEMY.(5)

This great philosopher shows very ingeniously that the earth must be at the centre of the sphere. He proves that, unless this were the case, each star would not appear to move with the absolute uniformity which does, as a matter of fact, characterise it. In all these reasonings we cannot but have the most profound admiration for the genius of Ptolemy, even though he had made an error so enormous in the fundamental point of the stability of the earth. Another error of a somewhat similar kind seemed to Ptolemy to be demonstrated. He had shown that the earth was an isolated object in space, and being such was, of course, capable of movement. It could either be turned round, or it could be moved from one place to another. We know that Ptolemy deliberately adopted the view that the earth did not turn round; he had then to investigate the other question, as to whether the earth was animated by any movement of translation. He came to the conclusion that to attribute any motion to the earth would be incompatible with the truths at which he had already arrived. The earth, argued Ptolemy, lies at the centre of the celestial sphere.

If the earth were to be endowed with movement, it would not lie always at this point, it must, therefore, shift to some other part of the sphere. The movements of the stars, however, preclude the possibility of this; and, therefore, the earth must be as devoid of any movement of translation as it is devoid of rotation. Thus it was that Ptolemy convinced himself that the stability of the earth, as it appeared to the ordinary senses, had a rational philosophical foundation.

Not unfrequently it is the lot of the philosophers to contend against the doctrines of the vulgar, but when it happens, as in the case of Ptolemy's researches, that the doctrines of the vulgar are corroborated by philosophical investigation which bear the stamp of the highest authority, it is not to be wondered at that such doctrines should be deemed well-nigh impregnable. In this way we may, perhaps, account for the remarkable fact that the theories of Ptolemy held unchallenged sway over the human intellect for the vast period already mentioned.

Up to the present we have been speaking only of those primary motions of the heavens, by which the whole sphere appeared to revolve once every twenty-four hours. We have now to discuss the remarkable theories by which Ptolemy endeavoured to account for the monthly movement of the moon, for the annual movement of the sun, and for the periodic movements of the planets which had gained for them the titles of the wandering stars.

Possessed with the idea that these movements must be circular, or must be capable, directly or indirectly, of being explained by circular movements, it seemed obvious to Ptolemy, as indeed it had done to previous astronomers, that the track of the moon through the stars was a circle of which the earth is the centre. A similar movement with a yearly period must also be attributed to the sun, for the changes in the positions of the constellations in accordance with the progress of the seasons, placed it beyond doubt that the sun made a circuit of the celestial sphere, even though the bright light of the sun prevented the stars in its vicinity, from being seen in daylight. Thus the movements both of the sun and the moon, as well as the diurnal rotation of the celestial sphere, seemed to justify the notion that all celestial movements must be "perfect," that is to say, described uniformly in those circles which were the only perfect curves.

The simplest observations, however, show that the movements of the planets cannot be explained in this simple fashion. Here the geometrical genius of Ptolemy shone forth, and he devised a scheme by which the apparent wanderings of the planets could be accounted for without the introduction of aught save "perfect" movements.

To understand his reasoning, let us first set forth clearly those facts of observation which require to be explained. I shall take, in particular, two planets, Venus and Mars, as these illustrate, in the most striking manner, the peculiarities of the inner and the outer planets respectively. The simplest observations would show that Venus did not move round the heavens in the same fashion as the sun or the moon. Look at the evening star when brightest, as it appears in the west after sunset. Instead of moving towards the east among the stars, like the sun or the moon, we find, week after week, that Venus is drawing in towards the sun, until it is lost in the sunbeams. Then the planet emerges on the other side, not to be seen as an evening star, but as a morning star. In fact, it was plain that in some ways Venus accompanied the sun in its annual movement.

Now it is found advancing in front of the sun to a certain limited distance, and now it is lagging to an equal extent behind the sun.

[FIG. 1. PTOLEMY'S PLANETARY SCHEME.]

同类推荐
  • 不必定入定入印经

    不必定入定入印经

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 负暄野录

    负暄野录

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 禅林宝训笔说

    禅林宝训笔说

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • 算山

    算山

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
  • RELIGION

    RELIGION

    本书为公版书,为不受著作权法限制的作家、艺术家及其它人士发布的作品,供广大读者阅读交流。
热门推荐
  • 驭剑奇谈

    驭剑奇谈

    来自现代的路人甲,机缘巧合穿越到未知大陆……【作者小白一枚,写不太来简介,所以就这么凑合着用了,希望大家不要介意呀!】类型:玄幻风格:轻松大家一起戳进来看看吧。
  • 洪荒伽蓝

    洪荒伽蓝

    天下风云出我辈,一入洪荒岁月催,皇图霸业谈笑中,不胜人生一场醉。宇宙浩瀚,混沌海、三十三天、天狱、鸿蒙每个地方都是超乎想象的巨大。盘古开天地;女娲造人族;先贤以血筑家园,提笔安天下,跨马定乾坤。杀上九天揽明月,诛尽魔……圣人治理世间,明心、知念、收欲、克己,懂进退,晓知足,执念够深却不会被其左右。
  • 青春鸟笼之小红帽接送点

    青春鸟笼之小红帽接送点

    因为迟到,郑红再次领教了爸爸的暴力。妈妈只好将她送入了小红帽接送点。在接送点里,郑红四处找乐、惹是生非……接送点的学生对她又爱又恨,接送点的老师拿她无可奈何……郑红约秦天柱单挑,谁知二人竟然挑出了朦胧的情愫……秦天柱很快移情别恋,喜欢上了郑红的闺蜜。郑红伤心不已,正欲转学,小红帽接送点却突遭变故。阴差阳错之下,郑红成了老师的女儿。初中毕业,郑红意外地收到了秦天柱的情书。一切的一切,原来如此,郑红忍不住潸然泪下!
  • 火澜

    火澜

    当一个现代杀手之王穿越到这个世界。是隐匿,还是崛起。一场血雨腥风的传奇被她改写。一条无上的强者之路被她踏破。修斗气,炼元丹,收兽宠,化神器,大闹皇宫,炸毁学院,打死院长,秒杀狗男女,震惊大陆。无止尽的契约能力,上古神兽,千年魔兽,纷纷前来抱大腿,惊傻世人。她说:在我眼里没有好坏之分,只有强弱之分,只要你能打败我,这世间所有都是你的,打不败我,就从这世间永远消失。她狂,她傲,她的目标只有一个,就是凌驾这世间一切之上。三国皇帝,魔界妖王,冥界之主,仙界至尊。到底谁才是陪着她走到最后的那个?他说:上天入地,我会陪着你,你活着,有我,你死,也一定有我。本文一对一,男强女强,强强联手,不喜勿入。
  • 寰宇霹雳

    寰宇霹雳

    无边星辰藏慧识,道儒佛者隐真章。今朝来人皆为客,落日归途莫显狂。烽火三尺亮兵燹,天地风云战无边。傲笑寰宇谁为王?自古胜者皆无为。
  • 孽海情天林黛玉

    孽海情天林黛玉

    浮生着甚苦奔忙盛席华筵终散场.悲喜千般同幻泡,古今一梦尽荒唐.谩言红袖啼痕重更有情痴抱恨长.字字看来皆是血,一番辛苦不寻常.片言解秋心,噙香对月吟.血泪凝绛珠,三年销黛魂.岂知红尘中,漫漫洒甘霖.愁海变晴天花媚玉堂人。
  • 阴阳天城

    阴阳天城

    在这个充满玄力的天城里,也是刚好遇到了此生最重要的那个人,也是苍茫的天意所致,他封绝尘与对敌洛心岚的相遇,仿佛就已经定了终身。明明恨得透骨,却在美人受伤时默默腾出了自己的肩膀;明明彼此为敌,却一次又一次逼近了暧昧的中心,变得越来越强大。他轩昂不羁,她温柔如焰,在这分别之际,他们又该何去何从?美人请留步,让我用一辈子来看着你,绝不让你受伤!
  • 逆世谱

    逆世谱

    一个皇子比乞丐更艰辛的成长历史,一个天才比菜鸟更悲催的奋斗生活,从卑微到伟大,从屈服到抗争,从乞丐到帝王,命运从不是上天安排的,不是优秀的血统,辉煌的身世决定的,是不屈的抗争,磨砺的血汗铸就的。“我没有退路了,起义这条路,一旦踏上,不是前进,就是死亡。”各色人物齐聚一堂,谱写一段逆反世界,时代变更的恢弘乐章。一个少年,一段传奇,一场战争,一个时代。天厉大陆,中洲纪,友情,爱情,历史,神话。
  • 气运所钟

    气运所钟

    我叫钟运,气运所钟的钟运。ps:致敬《佛本是道》。
  • 无间道:我当卧底那些年

    无间道:我当卧底那些年

    曾经的国之利器,困龙出狱强势回归,卧底江湖叱咤风云,一边是铁血柔情,兄弟女人,一边是罪恶丑陋,蝇营狗苟,为了人民的利益,他将在真情与使命间做出艰难的抉择!