Since 1985 there has been much theoretical progress on traversable wormholes. At first they were thought to enable time travel, so not taken seriously. More recent work rules out time travel and associated paradoxes, but still permits faster-than-light travel. This article explores some of the implications traversable wormholes have on the expansion of civilisations through the universe. In particular it is found each civilisation would impose a local region of simultaneity, or empire-time, which differs from the more natural, co-moving timeframe which astrophysicists usually use. Distant regions of the universe and alien civilisations can be reached in short periods of empire-time, whereupon their respective empire-time zones fuse together. Shortly after first contact is made all expanding civilisations connect together to form a universal time. Finally some limitations of euclidean space are contrasted with wormhole connected non-euclidean space.

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