Another cute FTL trick to explain away the "why aren't the skies crawling with advanced spaceships" question is the "everyone gets it at the same time" hypothesis. This may or may not be scientifically plausible (I bet you could crowbar it into semi-plausbility if you were really determined) but it fits very nicely into the SE4 universe. It goes something like this:
Literal FTL is impossible. Warp drives, gravity drives, hyperspace- it's all bunk. The only possiblity for FTL travel is a wormhole, but they require insane quantities of energy to create artificially, and few- if any- civilisations are lucky enough to get one within range of their home system.
Therefore, all the sentient species in the galaxy/ universe develop in isolation. Some are still swinging around in what pass for trees on their planets bashing one-another with rocks; others have fully exploited their homesystems, cruising along at the stagnant peak of their civilisations and are just now thinking about sending STL probes or colonisers to nearby systems; others are just at the chemical-rocket-powered dawn of their interplanetary era, blah blah blah.
Suddenly, one day, it all changes. Some mysterious event occurs. Perhaps an unbelievably ancient and advanced species on the other side of the galaxy has harnessed some unimaginably powerful energy source and started tinkering with artificial wormhole creation; perhaps some not-quite-so-advanced race found a natural wormhole and started screwing around with it; perhaps it was some as-yet unhypothesised natural cosmic phenomneomeneon that suddenly decided to take place all on its own. Maybe God, having collected enough insects, decides to stick them all in the same jar and see who gets eaten first. Who knows? All we know is that somewhere, a single event kick starts a galaxy-wide chain reaction. A network of wormholes (*cough*warp points*cough*) begins to spread across the galaxy. Wormholes are springing spontaneously into being, stretching out from gravity well (star system) to gravity well. Each system that is touched by this network spawns one or two or three more wormholes, creating an exponential expansion from the unknown point of origin. The whole thing happens quickly. One day, humanity is all on its own, minding its own business, busily mining the asteroid belt and bombing one another over who gets to stick a flag in Europa. Overnight, a big, blue, wierd, great wobbly thing appears in space just outside Pluto's orbit, and then a few days later more appear. Suddenly, the human race is just a few jumps away from other star systems and other races who, despite being at hugely varied levels of technological development, all find themselves at the dawn of FTL travel at almost precisely the same moment in the galaxy's history.
It's at about this point you either start up se4 and click "new game", or start writing.
And if you use that, I want a free copy of your book.
