Foundation and Earth

This is one of the "later" foundations books that Asimov wrote because people wanted to write them. We start with Travize on Gaia. Gaia is a collective mind where everybody shares the thoughts of everyone else, whether they be thoughts or emotions. Travize is going on a mission to try to find the legendary planet Earth.

Most of the novel consists of the group traveling around ancient, "uncharted" planets trying to find earth. Asimov uses this as a route to explore how isolated societies can fall. We have one planet that is now devoid of people, but now ruled by dogs and other carnivores. Another planet has people that have become hermaphrodites in order to not require the interaction with other humans and obtain maximal "personal freedom". (They also produce power on their own through 'tranducer lobes'.) Another society has a primitive culture that has advances in biotechnology and weather manipulation. They seem very peaceful. However, in order to maintain their their isolation, they inflict visitors with a deadly virus.

And so the novel goes, exploring these and a few other planets in order to find out more about the legendary earth (and hopefully find earth itself.) The exploration suffers from being very tied into the time Asimov's writings. These societies are separated by vast distances of space and time, yet they are very late-20th century in their outlook and behaviors. A "primitive" society looks a lot like 18th century Polynesia, despite being settled from earth many years in our future. (They also manage to maintain the same language despite thousands of year of time passing.) There are occasional "big differences" in technology, but somehow these don't cause any alterations to the society beyond their direct impacts.

Eventually the protagonists find earth. However, as in the legends, it appears to be too radioactive to support life. However, through something that looks like happenstance they end up on the moon, where a 20,000 year old robot has been manipulating human activity for some time.

The robot is on its last legs an has been quietly manipulating them so they can arrive there. This is an Asimovian robot with strong human characteristics. (The society at large is devoid of robots, viewing them as something that leads to degeneration.) The robot can manipulate people. However, it must adhere to the laws of robotics which require it to help humans and humankind. Thus it relies on Travize to make the decision to implement "Galaxia" instead of the Seldon plan for the betterment of humanity. Travize agrees and everything is happy.