Big History tells the story of the Universe from the Big Bang to the present. It would be impossible for any history course to cover everything related to its subject matter, and this challenge is particularly great in Big History because of the scales of time and size involved. Big History deals with this challenge by focusing on the eight turning points, or thresholds, over the course of the 13.8 billion-year story. At each of these thresholds, the Universe became more complex, and things appeared with significant new emergent properties. In this lesson, you’ll review what you’ve learned about this story, which will put you in the perfect position to think about the future of Big History in subsequent lessons in this unit.
As you learned in Unit 5, the biosphere is not static. The biosphere changes as a result of astronomical, geological, and biological influences. The dinosaurs, for example, became extinct as a result of an astronomical event—the effects of an asteroid impact on Earth. Every species impacts the biosphere, though the extent of that impact can vary dramatically. The impact of humans has changed over time. The impact of foragers was not dramatic, but these early humans did have the ability to destroy flora and fauna and cause fires in different parts of the Earth. Agriculture, and later the modern revolution, significantly increased the impact of humans on the biosphere. The acceleration of the last 100 years has seen an acceleration of these human impacts on the biosphere. What are the most significant of these impacts and what should humans be doing about them?
Historians typically focus on the past, asking questions like: What happened in the past? Why did it happen? What lessons can be drawn from these events? Studying the past is possible because there is lots of interesting evidence left behind for scholars of many disciplines—not just historians—to look at. Physicists, for example, can look at the abundance of hydrogen and helium in the Universe today and draw conclusions about the early history of the Universe. Geologists can look at the distribution of plants and animals and rock formations on the Earth today and draw conclusions about the how the configuration of the Earth’s continents has changed over time. Each discipline has its own questions and evidence and is interested in investigating change over time. Historians don’t typically predict the future, but given the number of trends you’ve studied in this course, it seems appropriate to give some thought to what the future might be like.