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Benefits and risks of Carbon-14

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Title:
Benefits and risks of Carbon-14
Topic:
Radiation
Question: 

What are the benefits and risks of carbon-14 for carbon-dating?

Answer: 

Carbon-14 (C-14) dating is a way of determining the age of certain archeological artifacts of a biological origin up to about 50,000 years old. It is used in dating things such as bone, cloth, wood and plant fibers that were created in the relatively recent past by human activities.

C-14 dating becomes less accurate over about 50,000 years and it should not be used to date items over about 100,000 years old.

C-14 is created in the atmosphere. It decays to C-12, the most stable form of Carbon, with a half-life of 5730 years – this means that after 5730 years, half of the C-14 in an object will have turned to C-12. After another 5730 years, half of the remainder will have turned to C-12 and so on.

When an organism dies, it stops absorbing C-14 and the C-14 already in its body starts to turn to C-12. The ratio of C-14 to C-12 in the remains of an organism indicates how long it has been dead. The method assumes that the C-14 / C-12 ratio in the atmosphere over the last 50,000 or so years is the same as it is today – a potential source of error.

Naturally occurring C-14 is in the food we eat and the air that we breathe and represents no threat to our health. There is radiation all around us from Carbon-14 and other sources. The harm it causes in our cells is low; our bodies are used to it and are able to repair the damage.

Nobel Prize winner Georges Charpak has calculated that a 70 Kg human body contains potassium-40, C-14 and other radioactive minerals, producing an activity of 10,000 disintegrations per second (Beckerels), most of them absorbed by body tissues leaving only a small amount to be detectable. He also considers the effect of a single fast electron emitted by a radioactive atom. Such an electron would disturb less than 105 atoms. Each cell in the human body contains about 1014 atoms and a body has about 1014 cells – a total of about 1028 atoms..

These numbers provide some perspective to the cellular harm caused by natural radioactivity. The body is constantly repairing the small damage it causes.

See also How Carbon-14 Dating Worksfrom "howstuffworks".
 


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