What will I learn in this guide?
The difference between interstellar and intergalactic, why you can't go have casserole with that nice couple from the Andromeda galaxy (sorry), whether or not Spock will strangle Kirk (again), how far a photon goes before its first birthday, how long it would take Voyager to cross the entire Milky Way, and what exactly "warp speed" means, in practical terms.
Really big. Much bigger than this image. So big, in fact, that we have to just refer to it as the “observable universe”, because we can’t see all of it to know whether or not it is, in fact, infinite. The important thing here is distance. More distance than we can really conceive of, because we have nothing concrete that we can even come close to comparing it to.
Look, the Milky Way! Let’s zoom in some more.
[Milky Way photo via wikipedia]
Take a moment to be in awe. …Okay, back on topic:
It’s bigger than its neighboring (dwarf) galaxies (100,000–120,000 light-years across the spiral), but still tiny compared to the vastness of our universe. Our Solar system (Sol) sits towards the inside (but not at the center of) the spiral. In Trek terms, we're right between the Alpha and Beta quadrants, and have done the most exploring there.
Who are our neighbors, and why can’t we (in the USS Enterprise, for the purposes of this argument) visit them?
We've got several dwarf galaxy neighbors, mentioned above, but our closest galactic neighbor of similar size is the Andromeda galaxy, 2.5 million light years away. We'll be using it for the remainder of this demonstration. Why can't we visit, you ask? Well...
[Helpful image also via wikipedia]
"Oh hey, I’m over in the Andromeda galaxy, welcome to the neighborhood, come over and have some casserole- oh wait sorry, you can’t, because EVEN AT MAXIMUM WARP it would take you so long that your ship would run out of power, likely before it even left your galaxy. Haha suckers, you haven’t developed intergalactic travel like we have."
UGH. And I really wanted that casserole, too.
What do you mean I can’t go to other galaxies with maximum warp? I thought warp speed was faster than the speed of light! That’s really fast, isn’t it?
Well, yes and no. First you need to understand the unit of measurement called a "light year" (you're probably already familiar with it, but maybe you slept through that particular physics class). It measures distance. Yes, I know, I know, it sounds like a unit of time. But since scientists just like to confuse people, it's actually distance. If I was actually serious about astronomy, I'd be using parsecs, but we're gonna stick with light years, because I don't want to do more math than I already have to.
There, you've understood it! So much easier than parsecs.
In earth terms, yes, faster-than-light travel is really fast. The closest we’ve gotten in real life (not Star Trek) is sending protons (3 meters per second slower than the speed of light) in a circular tube around Switzerland (I may be wrong, we may have made something move faster at some point, but this is still Pretty Damn Fast), without even consuming the earth in a black hole in the process! Science is amazing. (Sorry Vulcan, we’re doing better than you on the whole not-getting consumed-by-black-holes front.)
In the Trek-verse, you can look at this article that breaks what “Warp speed” actually means down by series and speed and describes all the canon inconsistencies (and oh boy are there canon inconsistencies. We’re going with the streamlined model and expressing all speeds between warp 9 and warp 10 as warp 9.X, though). Basically, ‘current’ canon wisdom gives warp 10 as the upper limit for faster-than-light travel, and we’re sticking with that, despite changes in in-universe terminology over time.
----At warp 1, the Enterprise can travel AT the speed of light, so 1 light year in 1 year. (ENT)
----At warp 5, the Enterprise can travel 200 light years in 1 year. (ENT)
----At warp 9.975, Voyager can travel 1,584 light years in 1 year. (VOY)
Okay, let’s go ahead and ignore that outlier, on the grounds that it was the 60s
Oh, right, it’s REALLY DAMN BIG. At warp 9.975, if Janeway wanted to cross the entire galaxy, it would take her 75 years. That’s without any stopping, random alien encounters, equipment malfunctions, unfortunate plot devices, or mutinies. Her chances are not looking good. She’s probably better off doing… whatever she ended up doing (guess who hasn’t finished Voyager yet? Me!).
So how long would it actually take if you wanted to leave this Galaxy entirely and head over to Andromeda for that casserole (at warp 9.975, of course)? About 1,600 years, most of it through intergalactic space (what most of the universe consists of), which is very empty. On the plus side, it’s almost certainly Borg-free! On the minus side, you can look forward to dying of extreme boredom before you die of of life-support failure (or, in the best-case scenario, of old age).
Hope you enjoy road trip games.
In conclusion, you should probably at least limit travel in your fics to locations within our galaxy. It helps keep your audience’s disbelief suspended, and keeps that crucial “science” part of science fiction intact. I would give you a specific distance, but considering canon, just keep it in the galaxy and use a convenient plot device (super-powerful/omnipotent aliens generally work. When in doubt, blame Q.) if they're traveling farther than a few thousand light years or so.
...And it keeps Spock from strangling Kirk again, which he absolutely would if he was stuck playing “I Spy” and “20 Questions” on the bridge with him for a lifetime. (“I spy with my little eye something… red!” “It is Lieutenant Uhura’s uniform.” “Damn, how’d you get it so quick?” “Captain, you have been using the same three objects for the past 2.75 months.” “…oh. So who’s up for 20 questions? I’ll go first! I’m thinking of an object bigger than a breadbox-” …and then strangulation.)
Unless, of course…
BUT WAIT! You never told me the difference between "interstellar" and "intergalactic"! You promised!
...If you haven't figured out by now that "interstellar" means "between stars" and "intergalactic" means "between galaxies", there is no hope for you.
DISCLAIMER/CITATION: If there are any factual errors in here, please remember that I am an art student, and that I wrote this from 11pm to 4:30am last night.
All of my information about physics and space is from Wikipedia and my Trek reference is Memory Alpha, because this isn't a damn term paper.
All drawings are mine except where otherwise noted. I'm so very not sorry for the Magic School Bus reference.
This guide first seen in a tumblr post; it has been edited and expanded to appear here. Reblog it here.