LET’S say life has arisen somewhere in the universe and that it has been very successful – so successful that it has ventured out into space. Let’s also say that we know nothing about it, and that this birth and maturation all happened so long ago that there has been time long enough for the beings to travel throughout the vast known universe. And finally, assume that these beings want to hang out in the galaxies (for the cuisine, or any other reason) while remaining hidden to us.
Given our current understanding of the physics of information, there’s likely a universal limit to the amount of computational power in a given amount of matter – you can only cram so much information and processing mechanism into your CPU/grey matter. So, assuming this limit is reached, the only way for an enterprising entity to add more intellectual capability is to add more mass. Ergo, our hypothetical superintelligent spacefaring lifeforms are likely to be fairly massive. But all this mass presents a problem – we stipulated that these beings want to keep us in the dark as to their existence, and no matter how clever you may be at concealing your matter (i.e. by ‘cloaking’ or via some other camouflage), gravitational lensing will give you away.
So what’s an alien to do? Well, one way to avoid the gravitational lensing effects would be to become less dense. Light rays would then deflect less, and an extended body could remain undetectable as long as the constituent mass has no apparent absorption or emission of light. (This argument also holds for a being of pure energy, as per Einstein’s relativity it would also produce a gravitational field.)
But there’s one clue that even the most superintelligent of superintelligent life would find difficult to conceal – their large scale effect on the dynamics of galactic material. If these beings became really massive (in summation on the scale of many multiples of stars) they would produce large gravitational effects that would alter the paths of the other (visible) objects in the galaxies they inhabit, effects that are inexplicable in the absence of the extra mass. It may be possible to counteract these effects through compensatory motion, but the energy cost would be so enormous as to be unsustainable. The large scale qualities of the galaxies themselves would tell the tale of their inhabitants presence.
In review, here’s our list of qualities for hidden supermassive superintelligence that like to live in galaxies:
• Result in galaxies with strange behavior
Interestingly, these are all qualities of “dark matter”, the invisible stuff that comprises 84% of the matter in the universe and was first detected indirectly by observations of galactic rotation rates.