quote:It says that Potasium-argon does not work for recent dates. I wonder, why not? why only for ages older than 100kya?
Because it has a long half-life. Not enough Argon will have accumulated for an accurate reading. It is intended for measuring things millions and billions of years old, not thousands.
quote:A similar question for radiocarbon dating. If radiocarbon dating is only useful for a maximum date of 100,000 why is it that when dating anything older we would get "back nonsense numbers"?
Usually I think its from creationists contaminating the sample.
Radiocarbon, like all things, does not work in all situations or all circumstances. Honest researchers are aware of this, therefore they avoid carbon dating things that are likely to give inaccurate results. Creationists on the other hand will rush to carbon date things like 45 million year old petrified 'wood.' Also, its the ratio of C12 to C14 that is important. If you date something millions of years old and say that you found carbon there, that doesn't mean anything. Also, implying that radiocarbon dating doesn't work when tested in situations where it is not meant to work is like saying computers don't work because you just threw one in a volcano and it doesn't turn on anymore.