14c and carbon dating

Absolute dating represents the absolute age of the sample before the present.

Historical documents and calendars can be used to find such absolute dates; however, when working in a site without such documents, it is hard for absolute dates to be determined.

Looking at the graph, 100% of radiocarbon in a sample will be reduced to 50% after 5730 years.

In 11,460 years, half of the 50% will remain, or 25%, and so on.

For example, Christian time counts the birth of Christ as the beginning, AD 1 (Anno Domini); everything that occurred before Christ is counted backwards from AD as BC (Before Christ).

Plankton absorbs, Carbon-14 from the ocean much like terrestrial plants absorb Carbon-14 from the air.

Since plankton is the foundation of the marine food chain, Carbon-14 is spread throughout aquatic life.

Limitations and calibration: When Libby was first determining radiocarbon dates, he found that before 1000 BC his dates were earlier than calendar dates.

He had assumed that amounts of Carbon-14 in the atmosphere had remained constant through time.

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