The results can be as much as 150 million years different from each other! They then pick the date they like best, based upon their preconceived notion of how old their theory says the fossil should be .
So they start with the assumption that dinosaurs lived millions of years ago, then manipulate the results until they agree with their conclusion. So why is it that if the date doesn't fit the theory, they change the facts?
Here is one example of an isochron, based on measurements of basaltic meteorites (in this case the resulting date is 4.4 billion years) [Basaltic1981, pg. Skeptics of old-earth geology make great hay of these examples.
For example, creationist writer Henry Morris [Morris2000, pg.
We must assume to know that the rate at which carbon-14 decays into nitrogen-14 hasn't somehow changed throughout the unobservable past.
We must also assume to know what the ratio of carbon-12 to carbon-14 was in the environment in which our specimen lived during its lifetime.
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However, conditions may have been different in the past and could have influenced the rate of decay or formation of radioactive elements.
And finally, we must assume that there hasn't been any contamination in the specimen which we are attempting to date.
Scientific research has called the first two assumptions into question.
Evolutionists assume that the rate of cosmic bombardment of the atmosphere has always remained constant and that the rate of decay has remained constant.
Scientists place great faith in this dating method, and yet more than 50% of radiocarbon dates from geological and archaeological samples of northeastern North America have been deemed unacceptable after investigation.
So if scientists believe that a creature lived millions of years ago, then they would need to date it another way. They assume dinosaurs lived millions of years ago (instead of thousands of years ago like the bible says).