system
Given the following post, respond as if you're commenting on Reddit:
human
[Mass Effect] Does the galaxy "need" the Relays? Could they still travel to other systems at FTL speeds with generation ships?
gpt
Yes, they *can* travel at FTL but sub-relay speeds. Relay-to-relay was nearly instantaneous. A really good warp core can bring a thing to *about* 15ly/day. Drawbacks include that it needs to refuel and discharge status much more often along that trip, requiring that a whole hell of a lot more infrastructure be built up, society would need to build one along every - or every other - system with a gas giant suitable for refining, building an infrastructure waypoint-bridge to every point of interest. Lack of availability of suitable planets might mean that some of these routes need to be meandering or indirect.

What this means for the section of the quarian fleet stranded near Earth after the blown relay... they need to cover something like 20,000 light years to get back home. That would be about five years of non-stop travel, *if* they could fly in a straight line, and if the infrastructure they needed was already present. Though with a large fleet they probably have a mobile refining ship - which means they have to spend almost half their time stopping for maintenance, repairs, refining, and refueling of every child vessel in the fleet. If they're lucky, persistent, and don't have to take any major detours, they might get back to Rannoch inside of the next decade.

For the Turian fleet - they didn't come as prepared, or with as many self-sufficient food-producing live-ships as the quarians, if they even bothered to bring supplies for a long journey. Luckily, they have less than half as long of a trip... but since nothing on Earth is edible for them, they're going to have some major problems. A lot of aliens are never going to make it home.

Galactic civilization can't continue to exist in the form it has been. Trade and visitation between cultures will be a slow, years-long voyage. The Citadel is no longer in any way centrally located. Major colony worlds that sprouted up near mass relays will have to deal with a gross lack of resources (including food) in the short term, and will no longer be relevant as hubs for trade and exchange. Since the extranet relied on the relays to send data packets at FTL speeds, communication between worlds will have to be set up through QE molecules, and will be strangled down to a bare fraction of its former bandwidth. Every level of government is going to become a lot less centralized and more locally regulated.