This is the sort of thing that keeps me up at night.*

...the sort of thing I'm always thinking about obsessively. In the Star Trek episode "Miri," the Enterprise (back when ships used to be all called the Something and not just Something) visits an earth-like planet overrun by a deadly virus which has killed all the adults and extended the lifespan of the kids. How Earth-like? how about Earth-freakin'-identical?!?:


Now, I do know why so many of the planet surfaces that Kirk and his merry crew visited looked like Earth, or more accurately, the backlot of Desilu Studios or canyons in the outskirts of Los Angeles: sheer economics of television production. (Also the same reason most aliens had two arms, two legs, and maybe, if we were lucky, a funny nose). There's also an in-universe explanation of this: Hodgkin's Law of Parallel Planetary Development, the idea that cultures across the universe evolve in similar ways, which is why you could spend Stardate 3972.2 on the Cowboy Planet and then warp over to Nazi World by Stardate 4001.9, making only a quick detour to Roman Planet on the way. Star Trek: The Next Generation backed this up with a story that made canon the long-discussed in-universe belief that each of the major galactic races was seeded by a group of superbeing meddlers, spreading similar beings across the far reaches of the galaxy much like you or I leaving our action figures in the back yard after a rousing afternoon playing "Infinite Crisis on Ultimate Secret Civil Wars." Whoops, that reminds me!

(sprinting out into the yard, retrieving my Captain America figure before the sprinklers come on, running back to the computer)

None of that, in or out of universe, however, explains why Miri's planet looks like Earth II: The Next Generation:


It's only commented on in the pre-credits tease of the episode when Uhura gasps and Kirk says in "Another earth...another earth!" Well, yes, Jimmy T., that is what we're looking at. But once y'all beam down to the planet and play with some tricycles and Yeoman Rand shows you her legs, everybody seems to forget this planet out in the middle of nowhere has an Africa and an Australia and a Bay of Biscayne, although they're probably all overrun with annoying little pre-teen twerps going "bonk bonk" in various languages.

So, my question, the thing I muse about at night, is this. I know that the episode itself never explained why this planet is a duplicate of Earth. Nor did any episodes of any of the follow-up shows: Star Trek: The Next Generation, or Star Trek: Deep Space Nine, or Star Trek: Hey Look, We Have a Borg in a Silver Catsuit or Star Trek: We're Not Going to Call Ourselves Star Trek, Oh Wait, Now We Are. Sheesh, we even had a Star Trek episode devoted solely to explain why some Klingons have bumpy foreheads and why others didn't. But although I know they're not "canon," did any of the Star Trek novels, of which there appear to be approximately one gazillion, try to explain it? Maybe as a parallel universe Earth that slipped through a wormhole? Trick of Trelane? Trick of Q? Giant alien race who copied the Earth for kicks? Cunningly-placed space mirrors? The world, well, just I, really, really want to know. And then maybe I'll sleep better at night.

After I figure out why we always see starships facing each other oriented on exactly the same plane, of course.

*Also, my fear of night-flying vampire bats.