What about Fermi's paradox though? I mean, where is everyone?
Why are there no other detectable signs of human life, like smoke signals, territory markers, or emissaries from any more but a handful of other tribes? Surely if advanced humans existed, they would have contacted these tribes by now, to share technology, discoveries, and medicine. Yet they haven't.
How can the whole planet be so... silent?
And, won't uncontacted tribes in the amazon have seen airplanes and such?
So, we don't see or hear artificial signs in other galaxies because light is from the times when there was not complex life in the universe.
Now, we only have to solve why we don't see or hear artificial signs in our galaxy. But the problem is not so perplexing because we are talking about one or two million years.
If, for instance, a big part of the galaxy is bad for complex life (after all, we are far away from the center and that could be relevant), Fermi's paradox is solved.
To be clear, I'm not saying that's what it is ... the fermi paradox is a great thought experiment. But let's just keep things in perspective. Low odds don't mean something won't happen, just like "true random" doesn't mean the same song can't/won't play 10 times in a row ;)
As in, the universe may be littered with the ruins of single-planet civilizations slightly ahead of our technology level. We may have observed and cataloged many such planets, failing to notice the ruins.
If all the civilizations started more or less at the same time that us, it's not so weird that we have not found anybody else. If you add some other factor (maybe civilizations are only possible far from the center, so there is a big spread between them) the probabilities improve.
It also would mean interesting times ahead for humanity.
Of course, all this is only idle speculation.
1)
Ordinary Matter ~10^53 kg (4.9%)
Dark Matter ~5*10^53 kg 26.8%
Dark Energy ~1.3*10^54 kg 68.3%
Undiscovered ? ?
Also, people talk a lot about not meeting aliens, but just talking to them. Based on the fact that we have little/no idea how Dark Matter and Energy works, and we only really use radio signals (when funding permits), it may be like trying to whisper at the Queen of England while standing in Norway; a telephone would be much better.
2) Tom Scott on immortality and risk : https://www.youtube.com/watch?v=B5a6wrJpxP4
3) Life may be so abundant in the universe that it's not worth talking or meeting up with. What would you say to a single mayfly if you could talk to one on it's level? No scientist or other person has bothered to try, and I think there's a good reason for that.
http://www.jodrellbank.manchester.ac.uk/media/eps/jodrell-ba...
And just the existence of life doesn't mean there's complex life. We don't have a firm lower bound on how long life took to arise on Earth after we got liquid water on the surface but it can't have been more than 120 million years. Photosynthesis, mitochondria, and other innovations allowing for complex life like you and me took way, way longer. I made a diagram for a blog post here:
http://hopefullyintersting.blogspot.com/2018/03/the-drake-eq...
In the context of this thread, lets say you are a species which stepped out of your planet, there are plenty of asteroids, and even planets lying around you can mine for resources. You settle billions of your kind in space. You are not running out resources and have no motivation beyond research and science to venture out a little far.
Would you, such a race, want to travel interstellar distances? You would travel far distances by organic growth.
Also its likely how old the universe is anybody who didn't kill themselves to extinction, is likely at our phase of development. And is likely asking the same questions as us. Those beyond our phase of development are hiding for a good reason.
It's not a given that alien civilizations "should" have developed this or that technology that we ourselves don't have.
Of those, I find plausible the observation that as we tame the world to suit us, we shrink. Cities, civilization, supermarkets, products, TV, internet. By this trend, we'll live in dream terranes before long. (BTW as people get richer, reproduction gets less).
But we'll need power, and eventually a dyson sphere to capture all the sun's light - perfect for an inward-looking, closed-off people! Then what, I'm not sure. Perhaps long before that, we won't need other suns; we'll have artificial suns (controlled fusion).
That's what happens to everyone else: as they grow in technological sophistication, they get better and better at directly meeting their own (previously evolved) needs.
As a result, intelligent life around the universe only exists as short 'blips', being around for too short a time to ever meet other species.
I don't get this. What use are ethics when everyones dead and gone?
Seeing the wide spectrum of intelligence and education that humans manage it's hard for me to believe we'll ever reach a point of uniformity as a species were something like self-imposed extinction would be plausible.
There's always a risk of that, unless you can 100% guarantee this won't happen you're basically gambling with another person's life. I don't think you have the right to do that.
The history of man suggests otherwise. The more our civilization progresses, and the more the population swells, the broader the array of philosophical positions those within the civilization tend to hold. We have no evidence for everyone eventually coalescing around one 'right' belief set.
History is also littered with non-reproductive sects, like the Essenes, aesthetics, or, today's answer to these, anti-natalists and child-free individuals. These groups don't tend to be very good at passing their belief systems on to new generations however, as one might expect, and they don't tend to last particularly long once they've emerged on the civilization scene.