People think about petty things, you know what I mean? I just think about the economy, business, world affairs.
Usually mathematics and philosophy. I would think a lot about graph theory, mathematics, logic especially. Regulatory networks in cells, the colonization of space, evolution (mostly about how evolution has shaped current life forms and their operating systems, especially at the cellular level. But I also think about the probable evolution of humanity from this point forward), and, on a more local level, enjoying life, staying in good health. When I was younger I studied Egyptology.