1. Radioactive Dating Calculating the age of a sample based
on the remaining amount of a radioactive isotope the sample contains.
By calculating the amount of uranium-238 and thorium-232, this meteorite was dated to be billion years old, give or take 2 billion.

2. How is Relative Dating Different?
Date fossils relative to their position in rock
No info on age in years

3. Half-life
The amount of time it takes for half of radioactive atoms in a sample to decay.
Different elements have different half lives and are used to date samples of various time periods

4. Used to date fossils and artifacts such as the “Ice Man”
Radiocarbon Dating
Used to date fossils and artifacts such as the “Ice Man”
found to be 5500 years old

5. Radiocarbon dating Method developed by William Libby at U. of Chicago
Won Nobel Prize in 1960
Also worked on Manhattan Project in 1940’s
Peaceful application of radioactive elements!

7. How does it work? Carbon-14 is taken in by living things
After organism dies, C-14 decays to form N-14 (escapes into air)
C-12 is common carbon isotope found in all living things and does NOT decay because it is stable!

8. How does it work? continued
Half life of C-14 is 5,730 years.
Ratio of C-14 to C-12 in living things is
1 to 1 trillion.
Materials are tested to see ratio of
C-14 to C-12 and date can be determined

9. Radiocarbon Dating

10. Sample problems:
What is the half life of a substance if 1/64th of the original amount remains after 1,500 years?
An isotope of cesium (cesium-137) has a half -life of 30 years.  If 1.0 mg of cesium-137 disintegrates over a period of 90 years, how many mg of cesium-137 would remain?