The phenomenon of radioactivity is rooted in fundamental laws of physics and follows simple mathematical formulas.Dating schemes based on rates of radioactivity have been refined and scrutinized for several decades.Or you can use it to find out how long it would take to get to a certain population or value on your house.The diagram below shows exponential growth:: The exponential growth model describes the population of a city in the United States, in thousands, t years after 1994.If you need a review on these topics, feel free to go to Tutorial 42: Exponential Functions and Tutorial 45: Exponential Equations. For example, if the model is set up at an initial year of 2000 and you need to find out what the value is in the year 2010, t would be 2010 - 2000 = 10 years.

But much to the consternation of scientists, young-earth creationism, which holds that the earth is only about 6000 years old, continues to be promoted in some quarters, and remains very popular with the public, especially in the United States.Some of the most commonly used radiometric schemes are [Dalrymple1991, pg. 55]: Each method has its own particular range of applicability, which derives from the half-life of the particular radioactive decay involved.Uranium-thorium dating, for instance, can be used to date specimens up to about 500,000 years old (since the half-life of the U-Th decay is 75,000 years), but Rubidium-Strontium dating can be used to date specimens billions of years old (since the half-life of the Rb-Sr decay is 48.8 billion years).One of the most well-known applications of half-life is carbon-14 dating.The half-life of carbon-14 is approximately 5,730 years, and it can be reliably used to measure dates up to around 50,000 years ago.