This is an informational tour in which students gain a basic understanding of geologic time, the evidence for events in Earth’s history, relative and absolute dating techniques, and the significance of the Geologic Time Scale.
Geologist Ralph Harvey and historian Mott Greene explain the principles of radiometric dating and its application in determining the age of Earth.
While some physicists used these discoveries for applications ranging from nuclear weapons to nuclear medicine, others applied them to understanding the natural world.
While that's nearly 20 times older than the Earth was once thought to be, it's a geological eye blink.Mammals, which for 150 million years had been small, rodent-sized creatures, rapidly evolved to massive proportions in the wake of the Cretaceous-Tertiary extinction 65 million years ago.Geological timekeeping continues to be a lively science, with new methods emerging all the time.After all, the ever-changing Earth rarely left a complete geological record.The age of the planet, though, was important to Charles Darwin and other evolutionary theorists: The biological evidence they were collecting showed that nature needed vastly more time than previously thought to sculpt the world.
The primordial cloud of dust that came to form the Earth contained unstable atoms, known as radioactive isotopes.