TenForward: Where Every Vulcan Knows Your Name

Just another world filled with the ruins of a civilization that ascended to energy beings

No kidding. They experienced 24 hours every 1.03 seconds--a differential of 88,992, meaning that 88,992 years pass on the planet for every one year in the galaxy at large. That's a staggering speed.

If you were to just map Earth's development directly onto that timescale, then that species would have evolved into its modern form only about three (galactic) years prior, around the time that the Voyager crew was getting stranded on that deserted planet by Seska and the Kazon. They were discovering fire around the time of the Enterprise-D's launch. Right now, today, if that planet existed, dogs would only just be evolving. Their geological time is almost perceptible to us.

So 20 galactic years would be the equivalent of about 1.8 million years on that planet. That's about how long ago we developed the idea of language. Obviously, we've never seen a species that advanced. Assuming they survived, they likely wouldn't even be the same anatomically as the peoples that the crew of Voyager met. We'd expect them to have developed concepts as transformative for their culture as language, fire, art, and clothing have been for ours.

It's possible that they'd see humans in a similar way that we see Australopithecus. They would have advanced so far beyond humans that humanity's scientific advancements over those 20 years would seem about as notable to them as our scientific advancements over the course of this morning seem to us. Voyager would almost certainly have receded beyond history, legend, or even myth. Some predictions of human advancement suggest that this species would have already surpassed the advancement needed to be a Type III on the Kardashev scale, but the fact that they are essentially trapped on that planet might direct their research inwards, in a similar way to how John Barrow modified the Kardashev scale. If they are a Type III-minus civilization after those twenty years, genetic modification is essentially child's play. They're probably hand-crafting exotic new materials and elements from scratch, and flirting with the idea of manipulating atoms directly.

If the species did not survive those twenty years, then the planet may be moving toward the rise of another sentient species altogether; assuming the biosphere remained intact.

That's super fun to think about.

If they venture out beyond their planet, they'll start losing loved ones left and right within 10 minutes. You'd have to have no ties on your home world to become an explorer. It's like shitty relativistic time dilation, except you don't have to be anywhere near light speed to experience it. I imagine that may dissuade a lot of them from leaving.