红移和蓝移 Redshift and Blueshift
红移和蓝移，也被叫做多普勒效应，描述了空间中物体向我们靠近或远离时，光波是如何变得更短或更长的。
Redshift and blueshift，also know as the Dopper effect, describe how light shifts toward shorter or longer wavelengths as objects in space move towards or away from us.
通过观察彩虹我们知道，光是由一系列颜色组成的，而每一种颜色的光波频率都不同，白光就是由所有不同颜色光波混合而成的。
As we know from looking at the rainbow, light is made a range of colours, and each with different frequency, white light is a mixture of all those different colour light waves.
光谱的一端是频率稍低的红光，另一端则是高频蓝光。
On one end of spectrum is red light with slightly lowered frequencies and on the other end is high frequency blue light.
图为可见光谱 - 红色端为较低频率的光波，蓝色端为较高频率的光波
The visible light spectrum - the red end shows light waves with lower frequencies, the blue end shows light waves with greater frequencies.
当波的源头远离观测者时，因为频率随着波的传播而分散，波会向红端移动，因此被称为红移。另一方面，如果源头向着我们移动，波会被压缩并提高频率，蓝移就会发生。
As the source of wave move away from the observer, the waves shift towards red end, since the frequencies become lower as waves spread out, hence called redshift. On the other hand, if the source move towards us, blueshift will happen as the waves get compressed.
在我们的日常生活中，救护车接近和离开的声音就是一个很好的例子。和光一样，声音也是由波构成的，频率越高，音高就越高。
An example in our daily life the sound of ambulance approaching and driving away. Like light, sound is also made of waves, and the higher the frequency the higher the pitch.
这就是为什么当救护车接近时，它的声音特别高(频率压缩并增加)，而当它离开时(频率分散并减少)就会非常低， 声音比来的时候低了不少。
That’s why when an ambulance approaches, it’s sound is especially high pitched (frequency increase) and much lowered when it leaves (frequency decreasing).
对于星系来说，当z=0时，相对我们的银河系，那物体就在和我们一样的速度和方向移动。
For galaxies, when z=0, there is no motion towards or away for our milky way.
视频为多普勒效应的解析
Explanation of the Doppler Effect
所以C1-23152的z= 3.35显示了它移动的速度有多快。相比之下，距离银河系最近的仙女星系的z = -0.001001。虽然负号表示它在正在向我们移动，但不用担心。
So the z = 3.35 for C1-23152 just shows how far and fast it is moving away. In comparison, the closest galaxy to the Milky Way, the Andromeda galaxy, have z = -0.001001. Although the minus sign indicated it moving towards us, it is nothing to worry about.
数据显示，当两个星系相撞时，由于密度低，两颗恒星相撞的可能性非常低，更不用说行星相撞了。而且仙女星系也需要至少40亿年才能到达银河系。
Statistics show, when two galaxies collide, due to the low density, it is very unlikely for two stars to collide, let alone planets. It will also take at least 4 billion years before it coming to us.
图为NASA的仙女星系
Image of the Andromeda galaxy by NASA
图片来自 NASA, KSU官网
Picture from official website of NASA, KSU.
