Offering in 1952 his new radiocarbon method for calculating the age of organic material (the time interval since the plant or the animal died), W. Libby clearly saw the limitations of the method and the conditions under which his theoretical figures would be valid: A.
Of the three reservoirs of radiocarbon on earththe atmosphere, the biosphere, and the hydrosphere, the richest is the lastthe oceans with the seas.
Familiar to us as the black substance in charred wood, as diamonds, and the graphite in “lead” pencils, carbon comes in several forms, or isotopes.
One rare form has atoms that are 14 times as heavy as hydrogen atoms: carbon-14, or C ratio gets smaller.
For example, the presence of recycled bricks at an archaeological site indicates the sequence in which the structures were built.
Similarly, in geology, if distinctive granitic pebbles can be found in the sediment beside a similar granitic body, it can be inferred that the granite, after cooling, had been uplifted and eroded and therefore was not injected into the adjacent rock sequence.
Radiometric dating and certain other approaches are used to provide absolute chronologies in terms of years before the present.
The two approaches are often complementary, as when a sequence of occurrences in one context can be correlated with an absolute chronlogy elsewhere.
These include some that establish a relative chronology in which occurrences can be placed in the correct sequence relative to one another or to some known succession of events.Even looking at geology alone, it is evident from the using a young earth. And, although you can come up with gross errors using radiometric dating, by and large, the millions of dates that have been accomplished lend support to their accuracy, granting, of course, a large margin of error.These "millions" of semi-accurate dates have correlated throughout the stratigraphic layers of the earth. Are they usable for giving a rough estimate of age..The correctness of the method depends greatly on the condition that in the last 40 or 50 thousand years the quantity of water in the hydrosphere (and carbon diluted in it) has not substantially changed. The method depends also on the condition that during the same period of time the influx of cosmic rays or energy particles coming from the stars and the sun has not suffered substantial variations.To check on the method before applying it on various historical and paleontological material, Libby chose material of Egyptian archaeology, under the assumption that no other historical material from over 2,000 years ago is so secure as to its absolute dating.Local relationships on a single outcrop or archaeological site can often be interpreted to deduce the sequence in which the materials were assembled.