One thing we often fail to understand is just how small our time window is. I call it a window because as we look further away we look at a different sliver of time, but always a tiny sliver of galactic time. A civilization could last a million years and span half a galaxy and we could fail to see it because the window we look at is offset by a hundred million years. Our window is tiny. The universe could teem with intelligent life and we might just be missing it.
Or turn it around. We started transmitting strong radio signals about 70 years ago. We’re visible to something like a dozen solar systems out of hundreds of billions of solar systems in our galaxy out of hundreds of billions of galaxies. It’s likely we won’t be transmitting radio signals for more than a hundred years given our current rates of self-destructive behavior.
It’s unlikely that our radio signals will reach very far for very long when considered against the vastness of space and time.
Worth noting:<p>- Historically, human civilizations needed nothing resembling a "wiped out" disaster to completely collapse. Put a bit of stress on 'em (modest & local climate change, "mining out" some so-convenient resource, or whatever), or just give 'em a few generations of "the good life" to get complacent, and things often collapsed. Usually, the "why?" amounted to "it's easy to be short-sighted and stupid, and that's pretty much how they behaved".<p>- A human civilization built on pre-1800-ish technology can suffer fairly complete collapse, and the survivors rebuild pretty quickly - repeatedly if needed. The vast majority of the population are <i>relatively</i> self-sufficient farmers. Livestock breeds. They grow their own seeds. There is little long-distance transportation, and that's mostly via wooden boats / barges / ships. And all the skills and knowledge needed to maintain (or rebuild) a "95%" version of a fallen civilization can fit into a few dozen human heads.<p>- Today's human civilization would fare vastly worse in any sort of "complete collapse" scenario. Supply chains, even for critical parts of our infrastructure, are global. And you'd need <i>tens of thousands</i> of experts to have all the skills required to rebuild a "95%" version of today's world.