How reliable is radiometric dating
That is, they take up less than would be expected and so they test older than they really are.Furthermore, different types of plants discriminate differently.The strength of the Earth's magnetic field affects the amount of cosmic rays entering the atmosphere.A stronger magnetic field deflects more cosmic rays away from the Earth.It cannot be used to date volcanic rocks, for example.The rate of decay of N in 5,730 years (plus or minus 40 years).These techniques are applied to igneous rocks, and are normally seen as giving the time since solidification.The isotope concentrations can be measured very accurately, but isotope concentrations are not dates.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
This also has to be corrected for. Second, the ratio of C in the atmosphere at that time to be estimated, and so partial calibration of the “clock” is possible.
Accordingly, carbon dating carefully applied to items from historical times can be useful.
So, we have a “clock” which starts ticking the moment something dies.
Obviously, this works only for things which were once living.