Cosmology and astronomy Videos attempting to grasp a little bit about our Universe (many of the topics associated with "Big History") Community Questions Scale of the universe Things in our universe can be unimaginably large and small. In this topic, we'll try to imagine the unimaginable! Stars, black holes and galaxies Our universe is defined by stars. This topic explores how they came to be and where they end up. This includes a discussion of black holes and galaxies. Earth geological and climatic history What is the Earth made up of and how do we know? What causes the seasons? Are there longer-ranging cycles in Earth's climate? Life on earth and in the universe When and how did life emerge on Earth? How did humanity develop a civilization? Is there other intelligent life out there?