The memory of Earth - Orson Scott Card

The planet called Harmony had been settled by humans nearly forty years before. The colony had been placed under the care of an artificial intelligence, the Oversoul, high in orbit. This master computer had one overriding command: guard the people of Harmony.

But now the Oversoul is itself in danger. Soon, within a thousand years, catastrophic war will break out on Harmony unless the Oversoul can be repaired. The master computer has determined that it must be taken back to lost Earth; someone on Harmony must be given back the knowledge of space travel in order to save the planet from destruction. For one family, about to be caught up in an approaching civil war, life will change for ever.

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