Fun fact: The Tyrannosaurus rex was one of the last dinosaurs to evolve, about 70.6 Ma (a specific date). The first dinosaurs evolved about 230 Ma (a specific date), 159 myr (a length of time) before T-rex evolved. We are closer in time to the T-rex than the T-rex is to its earliest dinosaur ancestor! See the difference in abbreviations yet?
Entire courses and careers have been based on the wide-ranging topics covering Earth’s history. Throughout the long history of Earth, change has been the norm. Looking back in time, an untrained eye would see many unfamiliar life forms and terrains. The main topics studied in Earth history are paleogeography, paleontology, paleoecology, and paleoclimatology—respectively, past landscapes, organisms, ecosystems, and environments. This chapter will cover (briefly) the origin of the universe, how we organize Earth’s immense 4.543 billion-year history, and how we understand Earth as a balanced system throughout that time.