What methods are used to calculate the age of the earth?
One of the first ways to calculate the age of the Earth began in 1896 with radioactivity. Relative dating, in which events are placed in sequence without knowing their age in years, was conducted with respect to law of superposition. The law of superposition states that in layers of sedimentary rocks or lava flow, the oldest layer is on the bottom and the youngest is on the top. This application provided a rational basis for measuring relative time. Contrary to past beliefs, such as that of James Ussher whose calculation made Earth about 6,000 years old today, the age of the Earth is 4.5 billion years.
