如何解释为什么红移可以作为宇宙大爆炸的证据？

来看样题中的例题：

问题：State and explain what can be deduced from the ‘redshift’ observed by astronomers in the light from all distant galaxies.[3] 

答案：

any three from:

• wavelength from distant galaxy is measured/compared with wavelength (of line spectrum) on Earth

• wavelength from distant galaxy is shifted to(wards) red end of spectrum

• distant galaxy is receding OR moving away from the Earth

• evidence that the Universe is expanding

这题共3分，答案从四条中任选3条即可。

Red shift是Doppler effect的其中一种，观察到的wavelength向红光移动，也就是波长增加了。

Red shift意味着distant galaxy在远离地球，并且距离越远的galaxy，远离地球的速度（receding speed）越快。

并且galaxies相互之间也是互相远离的。

这也就说明了宇宙是从一个点（singularity）开始膨胀的，也就是我们说的Big Bang Theory大爆炸理论。

我们再补充两条帮助大家理解这个evidence。

• the further away, the faster the galaxy moves away
  

• galaxies moving apart from each other implies expansion from a single point or since the Big Bang

如何解释宇宙微波背景辐射可以作为宇宙大爆炸的证据？

来看样题中的例题：

问题：Describe and explain what can be deduced from cosmic microwave background radiation (CMBR).[3] 

答案：

any three from:

• microwave radiation is observed at all points in space around the Earth o.w.t.t.e.

• radiation was produced when the Universe was formed

• this radiation has expanded into the microwave region of the electromagnetic spectrum

• this is evidence that the Universe expanded

这题共3分，答案从四条中任选3条即可。

宇宙微波背景辐射在地球周围各个方向、各个点都存在，因此我们叫背景辐射（background radiation）。

这也意味着这些辐射来源于一个点。

在宇宙膨胀的初期，温度较高，因此辐射波长比较短。随着膨胀，宇宙在降温，辐射波长增加。直到膨胀至今，辐射处于微波波段。这也恰恰说明宇宙以前温度很高。

我们补充以下几点来帮助大家理解这个问题。

• CMBR implies all parts of the Universe were in contact a long time ago;  or coming from single point or singularity  

• wavelength has increased as the universe has expanded; universe was (significantly) hotter long ago