A fossil can be studied to determine what kind of organism it represents, how the organism lived, and how it was preserved.However, by itself a fossil has little meaning unless it is placed within some context.Despite seeming like a relatively stable place, the Earth's surface has changed dramatically over the past 4.6 billion years.
Here is one example of an isochron, based on measurements of basaltic meteorites (in this case the resulting date is 4.4 billion years) [Basaltic1981, pg. Skeptics of old-earth geology make great hay of these examples.For example, creationist writer Henry Morris [Morris2000, pg.Despite this, the momentum gained in the two decades prior to 1972 has made 4.5 b.y.a popularly accepted “universal constant” even though the foundations on which it was based have been virtually removed.These changes typically occur so slowly that they are barely detectable over the span of a human life, yet even at this instant, the Earth's surface is moving and changing.
As these changes have occurred, organisms have evolved, and remnants of some have been preserved as fossils.
Some evidence is also presented to show that radiometric results that are in agreement with the accepted geological time scale are selectively published in preference to those results that are not in agreement.
The geological time scale and an age for the Earth of 4.5 b.y.
The latest high-tech equipment permits reliable results to be obtained even with microscopic samples.
Radiometric dating is self-checking, because the data (after certain preliminary calculations are made) are fitted to a straight line (an "isochron") by means of standard linear regression methods of statistics.
In a related article on geologic ages (Ages), we presented a chart with the various geologic eras and their ages.