Potassium argon dating and carbon 14 dating

This radioactive carbon 14 slowly decays back into normal, stable nitrogen.

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An illustration may help: Imagine you found a candle burning in a room, and you wanted to determine how long it was burning before you found it.

You could measure the present height of the candle (say, seven inches) and the rate of burn (say, an inch per hour).

Radiation from the sun strikes the atmosphere of the earth all day long.

This energy converts about 21 pounds of nitrogen into radioactive carbon 14.

In order to find the length of time since the candle was lit we would be forced to make some assumptions.

We would, obviously, have to assume that the candle has always burned at the same rate, and assumes an initial height of the candle. Similarly, scientists do not know that the carbon-14 decay rate has been constant.

The C-14 in the plant or animal will begin to decay back to normal nitrogen.

The older an object is, the less carbon-14 it contains.

One gram of carbon from living plant material causes a Geiger counter to click 16 times per minute as the C-14 decays.

A sample that causes 8 clicks per minute would be 5,730 years old (the sample has gone through one half life), and so on. Although this technique looks good at first, carbon-14 dating rests on two simple assumptions.

Plants breathe CO2 and make it part of their tissue.

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