if you rearrange a galaxy, will anyone notice?
Individual humans aren’t much of an impact on nature by themselves. Considering the sheer size of the Earth and our finite life spans, one would think we have very little effect on our world. But there are a lot of us and in the last thousand years, we’ve dammed or diverted many major rivers, built artificial islands, pumped billions of tons of greenhouse gasses into the atmosphere, lit up the the night skies with our networks of cities, put a smattering of objects in orbit, and managed to connect the world with fiber optic cables stretching across the ocean floor for thousands of miles. We’re slowly but surely changing the world, and if we were gone tomorrow by some bizarre happenstance, it would take nature centuries to truly erase the mark we left so far.
That’s why some scientists started calling the modern age the Anthrophocene, to reflect on how we changed our planet while developing a fully fledged civilization. And space writer Ray Villard ponders whether we could know if a similar temporal designation may apply to the universe itself after reading a paper by a theoretical physicist speculating on whether any species grow powerful enough to alter entire galaxies, doing what humans do on a scale many orders of magnitude greater and involving entire solar systems instead of cities or islands.
Here’s the question. If a species old enough amasses enough technological prowess, would it one day have to manipulate stellar structures big enough for another sufficiently advanced species to notice? This idea is a cornerstone of the Kardashev Scale by which such powerful creatures would register at Level 3 while we are barely even on the chart. For the time being, let’s leave aside the questions of how likely it would be for aliens to evolve the intelligence necessary to build massive interstellar spacecraft and continue to survive and thrive for millions of years as they roam the stars.
Maybe they’re just really lucky and have such a passionate vision, they banded together and made it their duty to reach beyond their own solar system. But how far would such a species reach? After all, a galaxy the size of the Milky Way is vast, and to modify it on a noticeable scale would require that the aliens in question manipulate tens of billions of stars. They’ll need trillions of intelligent robots doing their bidding across thousands of light years and executing complex orbital maneuvers that would sync their efforts to a sequence of events planned to last millennia. And they would need to somehow collect all the energy they would generate in this elaborate process. How would they even try to go about that?
Well, if we get very creative for a second and think back to a paper arguing that powerful aliens could draw a lot of energy from stellar mass artificial black holes, we could extrapolate further and make the leap to dark matter being the unseen influence of extremely advanced technology which keeps galaxies rotating around a central supermassive black hole which is periodically fed for a power boost, an artificial quasar of sorts.
Most of the energy wouldn’t be generated by the accretion disk in the galactic core, however, it would come from the quickened rotation of the galaxy. So imagine the Milky Way or Andromeda as giant turbines being ran by some insanely powerful alien civilization which channels the enormous currents generated in the process to power warp gates and supply its sprawling empire, an empire so huge we may never be able to detect it. Is this an idea we could actually use in SETI? Probably not, not only because such a phenomenon happening would be so extremely unlikely as to be practically impossible, but because we haven’t a clue as to how this would work and find any support for a species capable of manipulating an entire galaxy as their power grid. How would an astronomer find something we can’t even really conceive of beyond wild, random speculation?
Kardashev Level 3 entities should technically be some of the easiest alien civilizations to notice because an entire galaxy could give us clues to their existence and we can survey a whole lot of galaxies. But their means of altering these cosmic objects would have to be so far beyond us, we may well have seen a myriad of such powerful and technologically advanced aliens in public Hubble image galleries and don’t know it. Maybe we’ll never for sure know if these creatures exist or not. Though it may be fun to think about how exactly they would pull off the feats we usually tend to attribute to them. Who knows, maybe it would inspire us to start a mega-engineering project of our own to see how far we can advance our own technology in the process?