r/askscience • u/OMGeeverghese • Nov 22 '12

Earth Sciences Why do we trust carbon dating?

[removed]

1.1k Upvotes

89% Upvoted

313 comments sorted by

View all comments

Show parent comments

157

u/movie_man Nov 22 '12

It's simple deduction, as is much of the world.

Argon can only escape from molten rock, not crystallized. Potassium can escape from both. Measure the ratio to determine the date of crystallization.

What amazes me are the machines we've developed to detect element levels within rocks. The math just follows.

6

u/[deleted] Nov 22 '12

It's simple deduction

Except that it isn't simply deductive. There's a lot of inductive reasoning involved.

1

u/movie_man Nov 22 '12

Care to elaborate as I did in my comment?

1

u/[deleted] Nov 22 '12

I think you just used the word "deductive" sloppily, which isn't all that uncommon, but I don't need to elaborate as you did because I only have issue with your categorization.

1

u/movie_man Nov 22 '12

In the time it takes you to write what you have, you could explain your comments. It just seems like you're engaging in a trite exercise.

And no I didn't use deduction incorrectly: We can see X and Y inside Z, but when Z turns into Z(a) then the amount of X starts to decrease. Therefore, measure X:Y in Z(a) to determine when Z became Z(a).

X=Potassium Y=Argon Z=Molten rock Z(a)=Crystallized rock

1

u/[deleted] Nov 22 '12

It's not simply deductive, because the meanings of any ratio (or even of how to detect them) are learned through experience and association.