Underworlds

There are no major planets close to the sun, but there is a thick asteroid belt which is densely populated by civilizations which exploit the plentiful solar energy of the region. The region is handicapped by the intense solar radiation which destroys delicate electronic devices, fries unprotected organisms, and interferes with communication. Underworld cultures are very commercial, with much trading and traveling. Most intelligent species live in cramped artificial habitats burrowed into insulating rock, so when they can get out and see another rock, they generally do it.