Carbon dating has given archeologists a more accurate method by which they can determine the age of ancient artifacts.
Libby invented carbon dating for which he received the Nobel Prize in chemistry in 1960.
The resulting standard value, A The first standard, Oxalic Acid SRM 4990B, also referred to as HOx I, was a 1,000 lb batch of oxalic acid created in 1955 by the National Institute of Standards and Technology (NIST).
Another standard is the use of 1950 as "present", in the sense that a calculation that shows that a sample's likely age is 500 years "before present" means that it is likely to have come from about the year 1450.After acceleration and removal of electrons, the emerging positive ions are magnetically separated by mass and the C counts per second are collected.It is expected then, for a 5,570 year (1 half-life) or 11,140 year old (2 half-lives) sample that 125 or 63 counts per second would be obtained.This is addressed by defining the standard to be 0.95 times the activity of HOx I.All of this first standard has long since been consumed, and later standards have been created, each of which has a given ratio to the desired standard activity.Other useful radioisotopes for radioactive dating include Uranium -235 (half-life = 704 million years), Uranium -238 (half-life = 4.5 billion years), Thorium-232 (half-life = 14 billion years) and Rubidium-87 (half-life = 49 billion years).The use of various radioisotopes allows the dating of biological and geological samples with a high degree of accuracy.Organic materials, which require the most processing, are limited to younger ages by their corresponding process blank.Due to counting and measurement errors for the blanks and samples, statistical errors are higher for very old samples. As soon as a living organism dies, it stops taking in new carbon.The ratio of carbon-12 to carbon-14 at the moment of death is the same as every other living thing, but the carbon-14 decays and is not replaced.