如何解釋為什么紅移可以作為宇宙大爆炸的證據？

來看樣題中的例題：

問題：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

這題共3分，答案從四條中任選3條即可。

Red shift是Doppler effect的其中一種，觀察到的wavelength向紅光移動，也就是波長增加了。

Red shift意味著distant galaxy在遠離地球，并且距離越遠的galaxy，遠離地球的速度（receding speed）越快。

并且galaxies相互之間也是互相遠離的。

這也就說明了宇宙是從一個點（singularity）開始膨脹的，也就是我們說的Big Bang Theory大爆炸理論。

我們再補充兩條幫助大家理解這個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

如何解釋宇宙微波背景輻射可以作為宇宙大爆炸的證據？

來看樣題中的例題：

問題：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

這題共3分，答案從四條中任選3條即可。

宇宙微波背景輻射在地球周圍各個方向、各個點都存在，因此我們叫背景輻射（background radiation）。

這也意味著這些輻射來源于一個點。

在宇宙膨脹的初期，溫度較高，因此輻射波長比較短。隨著膨脹，宇宙在降溫，輻射波長增加。直到膨脹至今，輻射處于微波波段。這也恰恰說明宇宙以前溫度很高。

我們補充以下幾點來幫助大家理解這個問題。

• 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