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102.红移
P1:宇宙的起源和命运可以通过其组成部分的运动探索出来。其他星系在往各个方向远离。说明宇宙正在扩张、星系被分开。
P2:最近发现星系不是静止的。研究星系的运动可能可以回答:星系将会继续扩张?还是停止甚至逆转?
P3:Doppler effect:星系相对观察点移动产生的辐射或声音波长的变化。大多数星系产生红移说明光谱线正被红色或波长更长的光谱所替代。红移表明移动正在远离观察点。
P4:60年前大家比较难相信其他星系正在远离的说法。即使H观察到、也将其解释为不运动的宇宙。
P5:直到1930,宇宙扩张的观点已被大部分人接受。星系逃逸速度等于其距离乘以常数。这带来两个启示:宇宙往外膨胀是非常均匀、一 致的;膨胀源于150亿年前的大爆炸。
imprint 印记;constituent成分;motion 运动、手势;recede 退去;fabric 结构;spectral line 光谱线,spectrum 光谱、范围、幅度;static 静止的,静电的;dilation 扩大、膨胀;uniform 始终如一的、制服;unleash 释放、发泄
Sixty years later it is difcult to appreciate how radical suggestions that other galaxies are receding in all directions sounded when they were made in the early 1920's. They represented a change in world view in every way as fundamental as the Copernican revolution; the notion of a static universe was by then as well established as the geocentric universe had been in the 15th centuiry.
A being in a galaxy billins of light- years away would see the same relation between distance and red shift in surrounding galaxies as is seen from the Milky Way. |
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