How do scientists determine the age of once-living organisms when using Carbon-14?

Answer 1

C-14 is a radioactive isotope of carbon. This means it is always spontaneously changing the composition of its nucleus, in this case by beta decay. The carbon changes to Nitrogen-14.

In LIVING things the amount of C-14 stays the same, however, because living tissue is always making cells which constantly replaces any C-14 lost. It does this because the N-14 in the living cells reacts with neutrons from cosmic radiation and forms C-14 which gets incorporated into the living tissue.

Once the living tissue dies, the C-14 that is lost is not replaced anymore. The amount of C-14 steadily decreases according to the half-life of the C-14 (the time it takes for half of the C-14 to change to N-14) which is 5730 years. The ratio of the amount of C-14 in the dead tissue and the amount of C-14 in the living tissue is compared and the time is then calculated.

If you want the equations and the math, here they are:

N-14 + neutron = C-14 + H-1 (replenishment of C-14 in live cells)

C-14 = electron + N-14 (decay of C-14; the electron is the beta particle)

calculation of time:

N= activity of C-14 in the dead tissue
No = activity of C-14 in living tissue (always 14 disintegrations per second)
L (really should be the Greek letter "lambda" ) = 0.693/half-life
(half life of C-14 is 5730 years). This works out to be 0.00012

ln = the natural logrithim
The equation is:

ln N/No = -Lt or

ln N/14 = -.00012t (don't forget the minus sign)

All you need to do is measure the activity of the C-14 in the dead tissue and then solve for time.

Answer 2

There is a cerain ratio of C-12 to C14. When an organism is living it keeps taking in carbon either as CO2 in a plant or food in an animal. When it dies it stops taking in the carbon, but the C-14 keeps decomposing at its known rate, half life. So when a specimen is tested they test the ratio of C-12to C-14 and determine how much C-14 as decomposed. That tells how long it has been dead.

Answer 3

A certain amount of carbon-14 is in every living being, and only starts to decay after the organism dies. The half-life is 5730 years long, which means that every 5730 years, the amount of carbon remaining is half of what it was 5730 earlier.

By examining the amount of carbon-14 remaining in a specimen, scientists can determine how old it is.

Answer 4

The amount of carbon-14 in living things is the same as it is in the environment. Once something living dies, the carbon-14 present at that time begins to decay and is not replenished. By measuring the amount present, the time of death can be estimated.

Answer 5

They use Half life formula :D