material and is consistent with the radiometric ages of the oldest-known terrestrial and lunar samples.
Following the development of radiometric age-dating in the early 20th century, measurements of lead in uranium-rich minerals showed that some were in excess of a billion years old.
They then gather the radioactive, or M side up M&Ms, put them back in the container, and then pour them out again. and continue this process until all M&Ms are stable, or M side down.
During each trial, students record the number of radioactive parent isotopes and record this in a data table.
Once all groups finish, each group records their info on the class decay table (on the board) and we calculate the averages of the class. Isotope Concepts: Students should begin to see the pattern that each time they dump out their M&Ms, about half become stable.
Once this info is calculated, students create a graph comparing the class average of parent isotopes to the number of half-lives. Students will be able to explain what a half-life of a rock is. Students will have a more in-depth understanding of what radioactive decay is. Students will understand how scientists use half-lives to date the age of rocks. Students then should be able to see the connection of the M&Ms and radioactive elements in rocks, and how scientists can determine the age of rocks by looking at the amount of radioactive material in the rock.
When I first got involved in the creationism/evolution controversy, back in early 1995, I looked around for an article or book that explained radiometric dating in a way that nonscientists could understand. Young-Earth creationists -- that is, creationists who believe that Earth is no more than 10,000 years old -- are fond of attacking radiometric dating methods as being full of inaccuracies and riddled with sources of error.
All these methods point to Earth being very, very old -- several billions of years old.
Paul, MN, based on an original activity retrieved from also with the help of Jenni Johansen (other 8th grade science teacher at So. Paul Junior High School In this activity, students gain a better understanding of radioactive dating and half-lives.
It is also difficult to determine the exact age of the oldest rocks on Earth, exposed at the surface, as they are aggregates of minerals of possibly different ages.
Studies of strata, the layering of rocks and earth, gave naturalists an appreciation that Earth may have been through many changes during its existence.
Before 1955, ages for the Earth based on uranium/thorium/lead ratios were generally about a billion years younger than the currently popular 4.5 billion years. old Earth is reviewed and deficiencies of the uranium/lead method are discussed.
The basic theory of radiometric dating is briefly reviewed.