/sci/ - Science & Math

My two favorite solutions (beyond the easy cop-out: complex life is just rare AF and we're out in the boonies), are:

1) The Great Filter is merely the need to abandon the biological drive for infinite growth. Failure to do so means you'll likely exhaust your planetary biosphere before you become space faring. Biological immortality may oft come before space faring technology (and is more or less required for it, in a non-FTL verse), so that alone would force a population cap. If you have such a cap, once you've colonized a few systems, expanding more in the same galaxy cannot further ensure your species's survival. As you've no need for superstructures to power such small scale civilizations, those colonies you do have will probably have a small footprint, pretty much invisible to modern technology even if they happen to be nearby.

(And if that sounds too much like hippie talk.)

2) The Great Filter is the realization that the universe is doomed. Every civilization that builds a large enough particle collider to measure the top quark realizes we live in a False Vacuum, and the whole of reality could be reduced to hydrogen gas at any moment as a result. As soon as this is discovered, they build another even larger collider to create their own universe and (somehow) slip into it. Or, being immortal and extremely forward thinking, sink themselves inside the event horizon of a particularly large black hole to buy themselves more time.

Would be nice if they left a note for the rest of us though.