Final answer:
Scientists determine the absolute age of Earth's rocks and ancient fossils through radiometric dating, measuring radioactive isotopes' decay. Absolute dating provides exact ages, in contrast to relative dating which only establishes sequence without numerical ages. Key elements include carbon-14 as well as other isotopes, with important assumptions about the sample's original isotope content and its closed-system status.
Step-by-step explanation:
Scientists assign absolute age to Earth's rocks and ancient fossils using a method called radiometric dating. This technique is based on the decay rate of radioactive isotopes within rocks and fossils. The basic principle involves measuring the remaining quantity of the parent radioactive isotope and its daughter decay products within a sample. Using known decay rates, scientists can calculate the time elapsed since the rock or fossil formed.
Absolute dating differs from relative dating, which can only determine the sequence of events and not the exact age. Radiometric dating not only helps in establishing dates for rocks but also provides accurate age estimates for fossils by measuring elements like carbon-14 or other radioactive isotopes. This process requires certain assumptions, such as the rock being a closed system since its formation and starting with no daughter atoms.
The age of the rocks and fossils is crucial for constructing Earth's history, as it allows scientists to understand the timeline of life and geological events. By comparing parent and daughter isotopes, specialists can determine the age of geological materials and foster a deeper understanding of Earth's ancient past.