How Science Figured Out the Age of Earth
For centuries scholars sought to determine Earth’s age, but the answer had to wait for careful geologic observation, isotopic analyses of the elements and an understanding of radioactive decay
Stories by Paul S. Braterman
![The Age of the Earth—An Age-Old Question [Excerpt]](https://static.scientificamerican.com/sciam/cache/file/C35DEFC5-ED60-4989-B06A78140A6F65FD_agenda.jpg?w=275&h=154&fit=crop)
The Age of the Earth—An Age-Old Question [Excerpt]
Lord Kelvin applied thermodynamics to the problem of Earth’s age. Although his estimates are now known to be incorrect by several orders of magnitude, they shook up the established theories of 19th-century geologists