Stellar cartography

We've all seen or read science fiction tales of ships "warping" through space, of being instantaneously transported to somewhere very far away through some kind of wormhole or tunnel in space. It's pretty far-fetched and unless if someone can definitively find such a method of traversing vast distances in a blink of an eye, I'll put my money on good old-fashioned sublight travel.

But what if there were traversable wormholes? Hypothetically, if you were in a sublight ship that somehow entered one end of the wormhole at just the right vector and managed to survive the stresses of passing through that bridge, how would you know where you were? Science fiction writers typically get around that prickly problem by sidestepping it with powerful computers that could calculate position based on the stars.

You know what? That's not that easy. You see, in order to triangulate positioning using the stars, we'd need to know several things:

1. How far the star is from Earth (or some other known reference point)
2. How to identify the star from all the other stars out there

We have an idea of how far the stars are from Earth but we don't know for sure, especially for the really distant stars. We can measure distances to the stars using the parallax method for the nearer stars but as things get farther away, our measurements get progressively wobblier in precision. In fact, our distances could be out by as much as several orders of magnitude. So, if we don't know how far things are, we can't really triangulate at all. That, and in order to use the parallax method, that starship will have to take a measurement, travel a great distance, take another measurement and then it can do its calculations. In short, it takes time and even then, there's no guarantee it'll work.

We can identify stars here on Earth primarily by where it is on the celestial sphere. You can't really do that if you're somewhere else, especially if it's somewhere else very far away. But what if we can identify individual stars based not on their positioning as seen on Earth but by some other intrinsic property, perhaps through spectrographic analysis of the known stars? Well, that does have some merit...except for one tiny problem: here on Earth, we don't really see the stars as they are right now. What we are seeing is the light from the stars as they arrive here on Earth, which means that the farther away the star is, the larger the time delay will be. In other words, we're seeing what the star was, not what it currently is and that time delay is directly dependent on how far away the star is, as light travels. That's a bit of a problem because any spectrograph we have of the star will be wrong because as the star ages, its composition changes as it burns through its nuclear fuel. We can extrapolate what its current composition will be...but then we'd need to know how far away it was from Earth. Oops.

It's a bit more complex than that, actually. You see, in theory, wormholes don't just link two points in space - they might link two points in space and time. What that means is that when you pop out the other end of the wormhole, you will not only be somewhere else, you might be somewhen else too. Which tosses yet another wrinkle on the whole "figure out where you are by watching the stars" method.

Don't get me wrong. You can figure out where you are...roughly. Depending on the density of visible stars, you can probably figure out where you are in terms of being above or below the galactic plane. Likewise, you can probably figure out where you are in terms of distance to the galactic center, which is a pretty good reference point. Heck, if you had enough data, you can probably figure out which arm of the galaxy you're in. All of that gives you a decent picture of where you might be. Well, except for one small thing: this all presupposes you pop out in the same galaxy. If you popped out in another galaxy...all bets are off. Oops.

Stellar navigation is tricky because there's so much space (sic) out there. More than that, once you toss in wormholes, you now potentially have all of time to play in too. Which means that if you get lost, you're really lost. Does this mean we can never ever figure out where we are? Yes...and no. Given what we currently have, the short answer is no. What might be our saving grace is if we manage to figure out faster-than-light (FTL) communications, perhaps via communications devices that use quantum entanglement to provide a bearing to a beacon. We need FTL beacons because otherwise, you'd die waiting for the signal to reach you as it may take a very very VERY long time before it gets to you even if the signal travels at the speed of light. The first ship through the wormhole will have a really tough time of it but once you have a series of beacons scattered through space, triangulation becomes easier. Heck, you can even figure out when you are if you know when the beacons came online. Of course, if you jumped to a time before the beacons were deployed...you're still hooped.

Interesting problem. Sometimes, I think that being grounded on Earth due to physical frailty isn't such a bad thing.