Kennedy addresses this problem

Dating old fossils

Some critics, particularly religious fundamentalists, argue that neither fossils nor dating can be trusted, and that their interpretations are better. For example, if a magma chamber does not have homogeneously mixed isotopes, lighter daughter products could accumulate in the upper portion of the chamber.

Radiocarbon dates come from organic matter that contain the element carbon. By measuring the ratio of the amount of the original parent isotope to the amount of the daughter isotopes that it breaks down into an age can be determined. You can't predict when a specific unstable atom, or parent, will decay into a stable atom, or daughter. The Wheeler Formation has been previously dated to approximately million year old, so we know the trilobite is also about million years old. There are two main methods determining a fossils age, relative dating and absolute dating.

In the past years they have not found any fossils that Darwin would not have expected. The first work was done in England and France. So, often layers of volcanic rocks above and below the layers containing fossils can be dated to provide a date range for the fossil containing rocks. If the fossils, or the dating of the fossils, could be shown to be inaccurate, all such information would have to be rejected as unsafe.

Fossils may be dated by calculating

They point to minor changes within an organism, e. Fossils may be dated by calculating the rate of decay of certain elements. Think of the nucleus as a pyramid of building blocks. Secondly, you must have an observable time span so we can be certain nothing has affected the amount of the radioactive element being measured, e.

Scientists can check their accuracy by using different isotopes. Accuracy of the fossils Fossils prove that humans did not exist alongside dinosaurs. To determine the ages of these specimens, scientists need an isotope with a very long half-life. So to determine the age of sedimentary rock layers, researchers first have to find neighboring layers of Earth that include igneous rock, such as volcanic ash. Using relative dating the fossil is compared to something for which an age is already known.

The mathematical premise undergirding the use of these elements in radiometric dating contains the similar confounding factors that we find in carbon dating method. To read the time on this radioactive clock, scientists use a device called a mass spectrometer to measure the number of parent and daughter atoms. This is some finite point in the future. Carbon, the radioactive isotope of carbon used in carbon dating has a half-life of years, so it decays too fast.

There are so many complicated phenomena to consider like this that it calls the whole radiometric dating scheme into question. Only then can you gauge the accuracy and validity of that race. After death, organisms tend to decompose quickly.

They point to minor changes

This is the major flaw in radiometric dating, e. In a hypothetical example, a rock formation contains fossils of a type of brachiopod known to occur between and million years. The strict rules of the scientific method ensure the accuracy of fossil dating. Such a distribution would give the appearance of age. Certain naturally occurring elements are radioactive, and they decay, or break down, at predictable rates.

Sometimes multiple index fossils can be used. Though still heavily used, relative dating is now augmented by several modern dating techniques. Other methods scientists use include counting rock layers and tree rings. Chemists measure the half-life of such elements, i. Composed of layers of sediments laid down by colonies of cyanobacteria, stromatolites still exist, but are quite rare today.

Repeated, and tough, regimes of testing have confirmed the broad accuracy of the fossils and their dating, so we can read the history of life from the rocks with confidence. Carbon, or radiocarbon, is a naturally occurring radioactive isotope that forms when cosmic rays in the upper atmosphere strike nitrogen molecules, which then oxidize to become carbon dioxide.