This chapter has introduced three principles that can help us focus on major concepts rather than get lost in confusing details. The next three chapters will help you understand each of these three principles much more deeply. You will know and be able to explain how Earth works in terms of cycles of matter, flows of energy and the web of life.

But merely knowing something, even something as important as how our planet works, is not enough. We need to apply that information in our lives. The last two chapters apply this understanding of the whole Earth system to environmental issues that we face globally and locally. Dr. Art’s Guide to Planet Earth will not only help you understand these issues but it will also provide guidance regarding what we need to do as a global species, nations, local communities and as individuals.