Lecture 3. Carl Sagan once stated, “We’re made of star stuff.” Today, we are going to discuss why that phrase is 100% true. This lecture, we will discuss a brief history of our planet beginning with a bang – the big bang. We will explore runaway greenhouse effects, the habitable zone, the cosmic abundance, the molten, hot early Earth, the differentiation of Earth into layers – and like always, we will focus on identifying the connectedness of systems and processes.