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How To Determine How Old Is Something?

 

When archeologists find bones during digging, not many information can be obtained by bones visual inspection. With good knowledge of human skeleton, by visually inspecting the bones found, you can determine the approximate age of the person at the time of death and his/her sex, but the age of the bone, meaning when did that person die can be determined only after the Carbon 14 Dating, or by determining the amount of Carbon-14 in that bone.

 

 

What is carbon-14?

The atmosphere on our planet consists of 78% nitrogen. Under the influence of cosmic radiation from the universe, this nitrogen turns into carbon-14. This process is constantly going on. Carbon that is most widespread on our planet is carbon-12, so carbon-14 is its isotope (the simplest explanation for the isotope would be that it is a different variant of the same chemical element). Carbon-14 can also form CO2 (reacting with oxygen) which plants use to make food for themselves, with the help of the sunlight. Those plants that use CO2 made of carbon-14 are eaten by animals or people and so carbon-14 remains trapped inside of our bodies. This means that carbon-14 can only be intaken while we are alive or when we eat; after death it can no longer become part of the tissue. This carbon-14 is, during time, broken down into the nitrogen from which it originated. It is shown that the time required for 50% of carbon-14 to decay to nitrogen (this time is generally referred to as the half-life) is approximately 5730 years. Over time, scientists have estimated how much carbon-14 is inside of us and animals (in bones primarily), but also inside of plants (which is important for assessing the age of wooden items, fabrics, paper, etc.). Therefore, it is now possible to determine age of, for example, human bones as follows: if half of the expected amount of carbon-14 was found in the bones, it would mean that the bone was approximately 5730 years old (because the time required for half of carbon-14 to decay is 5730 years); If the amount of carbon-14 found is ¼ of the predicted amount, it means that half of it already decayed (so the 5730 years already passed), so the other half remained. Half of the remaining half decayed (so that’s 5730 years more) and ¼ remained; thus, 11460 years have passed and we can say that the bones are 11460 (5730+5730 years) years old.

The amount of carbon-14 can be measured by various methods, most often depending on the nature and quantity of the sample.

The disadvantage of this method as a method for determining the age of a certain sample is that it can be used for samples aged up to 60,000 years, because everything older than this contains negligible amounts of carbon-14.

For samples older than 60,000 years (such as volcanic stones aged about one million years), the Potassium-Argon dating method is used (which we may explain in another article).

 

Note: For a better understanding, some scientific facts are very simplified.

 

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