Changes
The rate of decay of C-14 is such that 50% of the C-14 in the sample will decay in 5730 years: 50% of the C-14 in the sample is left, after 11460 years 25% will be left, after 17190 years 12.5% will be left, after 50,000 years only about 1/500th of the C-14 remains - and since even initially it is only present as a minute proportion of the whole (0.0000000001% of all Carbon atoms)<ref>http://www.enviroliteracy.org/article.php/1006.html</ref>, measuring the exact quantity present accurately enough to be of use for dating purposes is extremely difficult. For this reason, scientists do not generally attempt to carbon date material that is believed to be older than about 50,000-60,000 years old.
[[Image:C-14decay.JPG|framed|The first-order decay curve of carbon-14 based on the half-life of 5730years. Most decay comes to a stop after 50,000 years.]]
== Limits of Carbon Dating ==
