With the discovery of radiometric dating, it became possible for the first time to attempt precise figures.Radiometric dating works on the principle that certain atoms and isotopes are unstable.here are the half-lives of some otehr radioactive elements: ).
Different world-views have different time-scales as regards the history of the Earth and the universe.Buddhist, Jain and Hindu cosmologies describe the universe as a never-ending series of cycles each lasting millions or billions of years.During the 19th century, and even well into the twentieth, geological chronology was very crude.Dates were estimated according to the supposed rate of deposition of rocks, and figures of several hundred million years were bandied out; usually arrived at through inspired guesswork rather than anything else.(The item being tested must be organic based, and must be dead - tests on live mollusks showed an age of 2000 years).
If a fossil is completely replaced (permineralized), then it would be useless in a similar test - because it no longer is organic.
Tree ring data (dendrochronology) can be used to even out this inconsistency, however the oldest trees used for calibration are in the order to about 6,000 years old, so any further back than that and you can't correct your dates (although there are reportedly some preserved huon pines in Tasmania that could take this right back to 30,000 years or so, if anyone wants to spend half their life time counting tree rings).
Even if dates are corrected with tree ring data they are still not considered calander years, but rather radiocarbon years.
Carbon 14's half-life is not nearly long enough to measure dates in the geological past.
For that elements with a half life of many millions of years are required.
The radioactive isotope Carbon 14 has a half-life of 5,730 years.