American dating system
Carbon-14 dating works well for samples less than about 50,000 to 60,000 years old and for things that were getting their carbon from the air.The long ages (billions of years) given by radioactive dating of rocks seems an impossibly long time for some people.The discussion above is for the case of determining when a ) are the radioactive carbon-14 isotope that will decay to form nitrogen-14 with a half-life of 5,730 years.
The old surface will have many craters per area because it has been exposed to space for a long time. If you assume that the impact rate has been constant for the past several billion years, then the number of craters will be proportional to how long the surface is exposed.That number is also the amount of parent that has decayed (remember the rule #parent #daughter = constant). in the age measurements of less than 100 million years.The narrow range of ages is taken to be how long it took the parent bodies of the meteorites to form.When plants absorb carbon-dioxide in the photosynthesis process, some of the carbon dioxide has the carbon-14 atom in the molecule.Assuming that our atmosphere's composition and the cosmic ray flux has not changed significantly in the last few thousand years, you can find the age of the organic material by comparing its carbon-14/carbon-12 ratios to those of now-living plants.