Conversation

I gather from my recent post about sci-fi space combat that there are plenty of people here willing to have nerdy discussions about that kind of thing. There's something that's been at the back of my mind ever since I started reading the Expanse series that doesn't have an answer in the text, and I suspect probably never will, but I think it's interesting to thing about nonetheless. I'll try to describe things well enough that those unfamiliar with the series can still weigh in. WARNING: Some Expanse spoilers ahead, up to roughly book/season 3.

In the story, we're presented with artifacts from an extinct alien civilization that once colonized some portion of the galaxy using what appear to be stable wormholes. These wormholes link ~1300 star systems to a central nexus point, such that you can enter a wormhole in any one of those systems, traverse a small pocket dimension of some kind, and emerge through another wormhole in any one of the connected systems using conventional propulsion.

It appears that this massive wormhole network was built by sending advance probes to these star systems to construct a wormhole endpoint ("ring gate") locally which then phone home to the nexus point to establish a link. We don't have any direct evidence that these beings were capable of FTL travel outside of the use of wormholes, so I think it stands to reason that these probes were sent from their point of origin at sub-light speed. We also know that the probe which was sent to our system ended up getting stuck in orbit of Jupiter, so it was going fairly slow, at least by the time it got here.

I don't know what the average distance between stars is in the Milky Way (and it likely varies considerably by region) but I do know that our closest stellar neighbor is roughly 4 light years away. If we wanted to send a probe there (and have it stop rather than zoom past) then the absolute fastest possible sub-light journey would be about 8 years (assuming half the trip was spent slowing down), and likely much, much longer than that as getting the probe anywhere near light speed would be pretty hard. So, if these distances are at all typical (and ignoring that the average distance to a "habitable" planet is probably much further than merely the nearest star) then I'd expect that this 1300 star system wormhole network would have taken a LONG time to build out, at least in human terms.

We don't have a map of where these systems are in the galaxy, but I think it's a likely guess that they stretch out in a branching pattern from some origin point (i.e. the aliens pick a system that is a reasonable distance from several other desirable systems, then once linked up they send more probes out from there instead of from their home system). That would probably mean that the growth of the network would start slow but rapidly accelerate as more nodes came online. There would still be some pretty hefty wait times between iterations, I think.

The only other major clue about the aliens' technology that we have that I can think of readily is Eros. In the books, the alien technology was able to propel a large asteroid without any discernible means thrust, and those inside it felt no effects from the acceleration. There's no indication of what kind of speeds it might have been capable of, or how long it could sustain propulsion but the acceleration demonstrated was on the order of 20 Gs or so, IIRC.

Anything other details I'm forgetting?

So, how did they (the aliens) likely approach this? How long did it take? What tricks might they have used or what shortcuts might they have taken?

#theexpanse #scifi #physics #astronomy #spacetravel #propulsion #aliens #nerds