问题的出现是因为天文学家已经注意到天空中的有些行星看似静止，有些向相反的方向运行，有些在作圆周运动。有时一些行星会显得比其他的行星更耀眼，而有些却显得比其他的暗。如果说地球是太阳系的中心并且所有行星都围绕着地球转的话，这些现象就非常奇怪了。

　　哥白尼努力地思考这些问题很长时间了，试图找到一个答案。他已经收集了那些星星的观察数据，并利用他全部的数学知识来解释它们。但只有他的新学说才能够做到这一点。因此，在1510年到1514年之间，他一直致力于对此进行研究，渐渐地改进他的学说直到他感觉已经完善为止。

　　In 1514 he showed it privately\s\up1(23(23) to his friends. The changes he made to the old theory were revolutionary. He placed a fixed\s\up1(24(24) sun at the centre of the solar system with the planets going round it and only the moon still going round the earth\s\up1(25(25). He also suggested that the earth was spinning\s\up1(26(26) as it went round the sun and this explained changes in the movement of the planets and in the brightness\s\up1(27(27) of the stars. His friends were enthusiastic\s\up1(28(28) and encouraged him to publish his ideas\s\up1(29(29)， but Copernicus was cautious\s\up1(30(30). He did not want to be attacked by the Christian Church, so\s\up1(31(31) he only published it as\s\up1(32(32) he lay\s\up1(33(33) dying in 1543.,\s\up1(23(23)privately ['praIvItlI] adv.私下地；秘密地

　　\s\up1(24(24)fixed adj.固定的；不动的

　　\s\up1(25(25)with the planets going round ... earth为with复合结构，作方式状语。

　　\s\up1(26(26)spin [spIn] vi.&vt. (spun, spun)(使)旋转；纺(线或纱)

　　\s\up1(27(27)brightness ['braItnIs] n．明亮；亮度；聪颖

　　\s\up1(28(28)enthusiastic [InˌθjuːzI'æstIk] adj.热情的；热心的

　　\s\up1(29(29)encourage sb. to do sth.鼓励某人去做某事

　　\s\up1(30(30)cautious ['kɔːʃəs] adj.小心的；谨慎的

　　\s\up1(31(31)so连接并列分句，表示因果关系。

　　\s\up1(32(32)as至句末为时间状语从句。

　　\s\up1(33(33)lie vi. (lay, lain)躺

　　 [第4段译文]

1514年，哥白尼私下里给他的朋友们看了他的新理论。他对旧理论所做的改动是革