Carbon dating

Carbon dating was invented in the beginning of XIX by Willard Libby who later received Nobel Prize for it. I will now explain the idea of this method.
Our planet is constantly stroked with sun rays and radio waves. Nitrogen can be transformed into an isotope of carbon(carbon-14) when exposed to them and this is what happens in upper atmosphere. Just like all isotopes, carbon-14 is unstable and half of it will become nitrogen again after ∓5730 years. The amount of carbon-14 is precisely measured(let's name it X for clarity of explanation) by scientists and it is assumed that this amount was always the same. Plants "breath in" carbon dioxide and make their tissue out of it and animals eat plants. Then plants and animals contain the same percentage of carbon-14 as atmosphere does. After death, organisms stop consuming new carbon-14. 
To estimate something's age, you have to measure how much carbon-14 does it contain. If it contains half the X, then the age we are looking for equals 5730 years. A quarter of X means 11460 years old etc. This method can't be used for organisms older than 30000 years.
The whole idea of carbon dating might be based on false assumptions, though. We don't know if the amount of carbon-14 was the same in the past. We don't know how fast carbon decayed earlier, either. 

Homework 03.01.18

Interesting words and phrase from video to learn:

1. Bairn=child
2. Cloth - materiał, tkanina
3. Unbeknownst to sb - nieznany dla kogoś