What the effects of differing speeds of faster-than-light travel in terms of a galactic civilization

Question

In a science-fiction story, the speed and ease of transiting from one star system to another should affect how the civilization works. I have read stories where different rooms in a house are in different star systems with instantaneous portals connecting the rooms. I have also read stories in which people commute from one star system to another on a daily basis. Then there are the FTL setups where travel can take weeks to make the transit. There is also the factor of the locations in the star system where FTL can take place. Typically gravity wells are bad and open spaces far from gravity wells are good.

Answer 1

Since you posted this on Writing, let's focus on the story impacts of the FTL speed.

The pacing and needs of your plot should dictate how fast people travel. Not only in space but everywhere. Since FTL already breaks the hard laws of physics as we know, the difference between instantaneous or 200% C is a matter of stylistic choice.

Is your story supposed to cover several generations of a family? A single month? Do you have any plot to happen during travel? Set your FTL to the speed most convenient to your plot.

Mary's answer already covers the effects of travel time on governance and defense of an empire. Take too long to reach the far edges of your domain and it might as well be another country.

Information and news may travel a bit faster than people but not much faster. The exchange of ideas is greatly hindered by the distance and time it takes to send messages back and forth. The Internet of the early XXI century saw the death of the "snail mail" but space travel that takes weeks or months to send a missive to and then again fro might resurrect the postal office.

The need to ferry messages and people to and fro can get you a space opera version of the Pony Express or of the Orient Express, in spayce![SIC]. Lots of good plot ideas there.

Let's not forget the Twin Paradox. People who travel the stars age slower than their planet-bound fellows, and space sailors going on a long tour of duty might return home to find their grandkids now look older than them.

Also, living in [zero-g / low-g / artificial-g] might cause health problems. In some fictions, people born and raised in space cannot go to the surface of the planet because their spines and bodies would be crushed.

Answer 2

The best thing to do would be to compare how differing speeds affected civilizations on earth. The chief effects are, of course, on trade and governance, but the effects are numerous.

An empire can only survive when it can get armed forces to a place in at most months to put down a rebellion. Quick travel also allows for quick communication, which allows the central government to have more direct control, rather than having to trust the man on the spot to deal with a situation. Emigration is mentally easier when you can travel back for visits, thus mixing up populations. Trade allows more specialization, though it does raise the danger of blockades.