(Since this is a decay problem, I expect the constant to be negative.
If I end up with a positive value, I'll know that I should go back and check my work.) In Its radiation is extremely low-energy, so the chance of mutation is very low.
Libby invented carbon dating for which he received the Nobel Prize in chemistry in 1960.
If possible, the ink should be tested, since a recent forgery would use recently-made ink.
Carbon dating has given archeologists a more accurate method by which they can determine the age of ancient artifacts.
The last figure I heard was that there are currently eight nuclear subs on our ocean floors. It doesn't work for sea creatures and other things that are under water. Then they measure how much is left in the specimen when they find it.
It comes from cosmic rays that rain down on the earth (and us) from outer space.
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).