Time and Trade

Time is a difficult concept when discussing an interstellar society. Let us first assume an interstellar society with faster-than-light travel. This society has many settled worlds, space colonies and interstellar trade. A society that trades and otherwise intermingles between the stars has communications, treaties and other activity befitting a society, including possibly government, interstellar or planetary and/or both.

Now time becomes more significant. As a day, as currently understood, is a rotation of the planet Earth around it's axis. It can be possible for humans to adapt to different time cycles on other planets and time can follow either the local time (possibly having more or less hours in a day and such) or follow a specific calendar, such as the gregorian calendar on Earth. Or both. We can manage to follow GMT, EET and EST simultaneously, following, for instance Proxima-2 time and Terran Standard simultaneously should be no problem. As long as both are known.

But are they known? Let us assume that FTL is instantenous and takes us from one point in space to another in zero or nearly zero time from traveller point of view. Starship goes to jumppoint, disappears. In destination, starship appears. Simple. And if the time elsewhere (destination, departure point) stays the same, the ship returns when making the jump back, perhaps a few days later. Universal time is easy to maintain and no one gets confused. There might even be no official planetary times, just some adjustments to get the real feel of the planetary or station flow of time.

Let us now assume that the ship has travelled instantenously and there is a time lag of month per lightyear of distance. Much faster than speed of light. But a round-trip to Alpha Centauri takes almost 9 months on Earth while the traveller has been gone, from his point of view, a few days or a week or so. This is more confusing but it is possible to calculate. Travel also becomes a bit less tempting, as will trade. If taking care of immediate demands somewhere takes months at best, colonies on other starsystems tend to be very self-reliant and basically only ordering machine parts or other items not normally available in that system or planet. Trade focus is interplanetary and interstellar trade is more like spice trade in the 18th century, high-risk, high-gain. The items sought for might no longer be needed and the merchant is left sitting on a pile of useless goods. Still, zero-time travel from traveller point of view makes the trade reasonably profitable on goods that are always on demand. The merchant simply pops in, queries the planet for their needs. If none, he moves elsewhere to trade. Time on his ship passes more slowly than in the surrounding world meaning that he will have to synchronize his clocks after each jump. Time becomes more difficult to manage on other planets as well, as jump-ship time is out-of-date. If time lag can be accounted for exactly, time shouldn't be a problem. There would probably be several different calendars in use, one for each inhabited system or planet.

Third scenario. Let us assume that this FTL travel is not instantenous, say, jump time from Sol to Alpha Centauri takes a week in hyperspace. After this, ship arrives at edge of Alpha Centauri system and with good engines arrives at orbit of the inhabited inner planet(s) in a month or so. This cuts the travel time in short and creates incentive to systems to establish trading posts near the outer edges of the system. The planetary transports transfer the goods to the trade post and from the trade post, merchants never really entering the system. In this case there is also some lag, as the needs of a system or planet are known about a few weeks afterwards, but still less than the months. Time passes in this scenario as well, but less so and the time can be more easily managed.

Let us now assume two additional scenarios.

1) There is no FTL, but ships can achieve near-lightspeed speeds. A one-way trip to Alpha Centauri could take, say, 20 years from observer point of view. To the traveller, less time has passed. Far-flung interstellar colonies are practically self-sufficient. There is no interstellar trade, probably only supply ships and communications from government, if even that. Travel is mainly transportation of people for permanent settlement or possibly military expeditions, though even these might be rare. All time is system-local, probably based in colonization dates on the interstellar colonies. There might be estimates or even actual knowledge of current time back home, but it is probably used for reference if it is not useful for the settlers in some way.

2) The FTL time delay is determined by an unknown or possible random factor (quantum mechanics or such). If time delay is not noticed and there is no FTL radio, there is mainly local time, based on colonisation dates or some other notable event. Or it tries to maintain the Earth Standard (or equivalent) time.

A little on-off topic on this one, but hopefully enlightening on the matters of time, trade and interstellar space.