"Everything which has come down to us from heathendom is wrapped in a thick fog; it belongs to a space of time we cannot measure.
We know that it is older than Christendom, but whether by a couple of years or a couple of centuries, or even by more than a millenium, we can do no more than guess." [Rasmus Nyerup, (Danish antiquarian), 1802 (in Trigger, 19)].
Scientists use a technique called radiometric dating to estimate the ages of rocks, fossils, and the earth.
But, carbon dating can't be used to date either rocks or fossils.
It is only useful for once-living things which still contain carbon, like flesh or bone or wood.
Once the tree dies, it ceases to take in new carbon, and any C-14 present begins to decay.
The changing ratio of C-12 to C-14 indicates the length of time since the tree stopped absorbing carbon, i.e., the time of its death.