How does carbon dating work?

Question

If carbon 14 is continually decaying why is there any left at all? I understand the carbon comes from carbon dioxide. But where is the isotope made? In the plants? From animal respiration? To me the plants or the animals have to create the isotope, if it was there before it should be decayed already.

Update:

thanks dooberheim, for being helpful amongst trolls

Tyler · Accepted Answer

Radiocarbon / Carbon-14 is a radioactive isotope of carbon with a nucleus containing 6 protons and 8 neutrons.

There are three naturally occurring isotopes of carbon on Earth: 99% of the carbon is carbon-12, 1% is carbon-13, and carbon-14 occurs in trace amounts. 

Carbon-14 is produced in the upper layers of our atmosphere by thermal neutrons absorbed by nitrogen atoms. The highest rate of carbon-14 production takes place at altitudes of 9 to 15 km (30,000 to 50,000 ft) and at high geomagnetic latitudes. 

Carbon-14 readily mixes and becomes evenly distributed throughout the atmosphere and reacts with oxygen to form radioactive carbon dioxide which dissolves in water and thus permeates the oceans.


***In Short***

The ratio found in living organisms is ~1%. We breathe in 14C and our skin comes in contact with it even if only in trace amounts. This is how is gets into all organisms tissues planet wide. The isotope is not manufactured by some biological process. 

**FUN FACT**

People born between the years of about 1950 through about 1980 have a higher concentration of 14C in their tissues since many countries were field testing nuclear weapons which increased 14C in the atmosphere. 

One side effect of the change in atmospheric carbon-14 is that this has enabled some options for determining the birth year of an individual, in particular the amount of carbon-14 in tooth enamel or the lens of the eye.

dooberheim · Answer

C-14 is continually created in the upper atmosphere by cosmic radiation, and it filters down to the surface and gets incorporated in plants and animals.  It has a half life of 5700 years, (meaning half of it is gone in that time), so scientists can measure the proportion of C-14 to regular carbon and determine when a particular artifact was made/grew.

DK

Anonymous · Answer

Radiocarbon dating (usually referred to as simply carbon dating) is a radiometric dating method that uses the naturally occurring radioisotope carbon-14 (14C) to estimate the age of carbon-bearing materials up to about 58,000 to 62,000 years

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How does carbon dating work?

3 Answers