The famous astrophysicist Carl Sagan once showed a picture of the Earth from hundreds of miles in space, looking like a dot. He said to a crowd “Look again at that dot. That 's here. That 's home. That 's us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every