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IGCSE物理(0625|0972)新增考綱：Big Bang的兩大證據(jù)
時(shí)間：2023-12-26
來源：網(wǎng)絡(luò)
作者：未知
IGCSE Physics（0625&0972） 已從2023年開始將啟用新大綱（2023-2025）。
新增的天體部分，內(nèi)容比較廣泛，涉及了有關(guān)地月系、太陽系、恒星及宇宙的各個(gè)方面。
本期帶大家復(fù)習(xí)支持Big Bang Theory（宇宙大爆炸）的兩大證據(jù)（Evidence）。這個(gè)知識點(diǎn)的考察考法可以很靈活，可以是選擇題，也可以是簡短簡答題，或者是3分或3分以上的簡答題。
先來看新考綱對這兩個(gè)知識點(diǎn)的要求：
4 Know that redshift in the light from distant galaxies is evidence that the Universe is expanding and supports the Big Bang Theory
6 Explain that the CMBR was produced shortly after the Universe was formed and that this radiation has been expanded into the microwave region of the electromagnetic spectrum as the Universe expanded
①Red shift 紅移
如何解釋為什么紅移可以作為宇宙大爆炸的證據(jù)？
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(yuǎn)離地球，并且距離越遠(yuǎn)的galaxy，遠(yuǎn)離地球的速度（receding speed）越快。
并且galaxies相互之間也是互相遠(yuǎn)離的。
這也就說明了宇宙是從一個(gè)點(diǎn)（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(bǔ)充兩條幫助大家理解這個(gè)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
②CMBR 宇宙微波背景輻射
如何解釋宇宙微波背景輻射可以作為宇宙大爆炸的證據(jù)？
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(gè)方向、各個(gè)點(diǎn)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(gè)點(diǎn)。
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(bǔ)充以下幾點(diǎn)來幫助大家理解這個(gè)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
