Radiometric dating is used to tell the age of rocks difusora pirassununga online dating
In regions outside the tropics, trees grow more quickly during the warm summer months than during the cooler winter.
This pattern of growth results in alternating bands of light-colored, low density "early wood" and dark, high density "late wood".
The discovery of radioactive materials did more than disprove Thomson's estimate of Earth's age.
It provided a way to find the absolute age of a rock.
The thin, dark part of each ring represents slow autumn and winter growth.
This estimate was a blow to geologists and supporters of Charles Darwin's theory of evolution, which required an older Earth to provide time for evolution to take place.
Radioactive materials in Earth's interior provide a steady source of heat.
Calculations of Earth's age using radioactive decay showed that Earth is actually much older than Thomson calculated.
While tree rings and other annual layers are useful for dating relatively recent events, they are not of much use on the vast scale of geologic time.
During the 18th and 19th centuries, geologists tried to estimate the age of Earth with indirect techniques.