How old is that tooth???

[IrishEyes]

I have a question about age-dating. No, FreeT, not dating people that are really old!!

 

On a recent trip to a local beach, we found some shark's teeth and whale bones. Now, according to Jasper Burns, these things are millions of years old. Without going into the why of it in this forum (WARNING TO NOT TURN THIS INTO NEW/OLD EARTH BATTLE!!), we would like to watch the process of how an object is 'dated' to discover it's age. In my experience, it is a rather circular thing but we'd like to see the actual 'science' of it.

 

How does the process work?

 

And where can I send these teeth to find out their age?

[Freethinker]

Originally posted by: IrishEyes

I have a question about age-dating. No, FreeT, not dating people that are really old!!

She said she was over 18, HONEST!

And where can I send these teeth to find out their age?

Let us know how it turns out. It would be very interesting.

[Uncle Martin]

IrishEyes,

 

I would recommend you call the archaeology dept. of your nearest University. They are sometimes very happy to let their students accomodate requests like yours. They may even enjoy you making a "class project" of it with your kids. It never hurts to ask. I get all kinds of things tested for free this way.

[Bo]

yes i also think that uncle martin's suggestion is the right way to do this. As for your question how they do this: most dating goes by radioactive decay. The procedure is the following: You know (or assume to know) the relative abundency of a certain radioactive material in the teeth when it was created. Then you look up in a table how fast that material decays, and finaly you measure the abundancy in the present time. So a small (unrealistic) example: You know that on creation the ratio C14 (radioactive) / C12 (stable) should be 0.1. further you know that the half life of C14 is about 5000 years. So if we measure a ratio of C14/C12 = 0.05; this means that half of the C14 has decayed, so the sample is about 5000 years old.

 

Bo

[IrishEyes]

Unc - thanks for your info. I'd thought of that, but was hoping for another suggestion, as my 'local' university is more liberal arts and not all that strong in sciences. Luckily for us, we are not too far from some other very good schools, so I'll do some digging, so to speak.

 

Bo - also, thanks for your info. A few questions to clarify??? How does anyone know the 'relative abundancy of a certain radioactive material in the teeth when they were created"? Basically, I send them the teeth, they say "Hmm, old shark's teeth. Probably about 3 million years old", then they base their tests on the assumption that these teeth are about 3 million years old?

 

FreeT... help me out here! 'Splain it to me like I'm 6 years old!!!

[Freethinker]

Originally posted by: IrishEyes

 

FreeT... help me out here! 'Splain it to me like I'm 6 years old!!!

Common Irish, you know you are just trying to make fun of Evolutionary science which claims an earth billions of years old..

 

Is that a good start? :-)

How does anyone know the 'relative abundancy of a certain radioactive material in the teeth when they were created"?

It's simple. ALL living materials take in carbon and some part of it is carbon 14, some carbon 12. The ratio is the same for all living cells.

 

When the cell dies, it stop taking in additional carbon. The existing carbon 14 then decays to carbon 12. Thus, with an established amount of carbon14 to 12 for LIVING cells, the more carbon 12 there is to 14, the longer ago the sample lived. Based on the half life of Carbon 14 at 57,000 years or so (memory weak?), a direct ration of LIVE cell carbon 14 to dead cell carbon 14 gives an exact age. But because of the short half life, Carbon dating is only good to about 60,000 years.

 

However the same process can be used with other radioactive materials commonly present.

[Bo]

Nice site that explains it quite clear: http://www.c14dating.com/int.html

And Freethinker: C14 decays to N14 Bo

[IrishEyes]

Bo, thanks so much for that link. I'm going to bookmark it for future use.

 

FreeT, actually, I was being serious. Ages ago, in high school, we never went over the carbon dating process. Now, none of my children have been interested in it before, so there was no real need for me to research the actual methods. Now, thanks to my shark-tooth crazed son, it has become an interesing topic of conversation. I'm going to take the advice of Bo and Unc and get in touch with a college lab.

 

And FreeT, thanks for the explanation.

 

I'll keep you guys posted on what happens next.

[Freethinker]

Originally posted by: Bo

Nice site that explains it quite clear: http://www.c14dating.com/int.html

 

And Freethinker: C14 decays to N14 Bo

 

Yes you are correct. My bad.

 

As to a good reference site, I would suggest:

 

"How Carbon-14 Dating Works"

 

http://science.howstuffworks.com/carbon-14.htm

 

It is a much simpler discussion for a very basic level understanding. I think it would be perfect starter for Irish's kids.

[Freethinker]

Originally posted by: IrishEyes

Bo, thanks so much for that link. I'm going to bookmark it for future use.

 

FreeT, actually, I was being serious. Ages ago, in high school, we never went over the carbon dating process.

Of course not. At that time there had not been enough carbon atoms produced to have a measurable amount of C14! :-)

[Freethinker]

Originally posted by: Freethinker

Originally posted by: Bo

 

Nice site that explains it quite clear: http://www.c14dating.com/int.html

 

And Freethinker: C14 decays to N14 Bo

And before another correction comes around, there is also C13 taken in by cells, which like C12 is stable.

[TeleMad]

Freethinker: ALL living materials take in carbon and some part of it is carbon 14, some carbon 12. The ratio is the same for all living cells.

 

Wrong.

 

Each sample type has specific problems associated with its use for dating purposes, including contamination and special environmental effects. While the impact of radiocarbon dating has been most profound in archeological research and particularly in prehistoric studies, extremely significant contributions have also been made in hydrology and oceanography. In addition, in the 1950's the testing of thermonuclear weapons injected large amounts of artificial radiocarbon ("Radiocarbon Bomb") into the atmosphere, permitting it to be used as a geochemical tracer.

 

Carbon dioxide is distributed on a worldwide basis into various atmospheric, biospheric, and hydrospheric reservoirs on a time scale much shorter than its half-life. Metabolic processes in living organisms and relatively rapid turnover of carbonates in surface ocean waters maintain radiocarbon levels at approximately constant levels in most of the biosphere. (http://www.ndt-ed.org/EducationResources/CommunityCollege/Radiography/Physics/carbondating.htm)