Originally posted by Ponderable
They could just be too far away?
How far to Proxima Centauri? Hw long a travel at sub-light speed? Is it worth the effort?
Even at 1/20th of c the trip from Centauri to here would a mere 80 years. A couple of generations of humans but if the alleged aliens lived for a thousand years....
The real deal is the life span of civilizations. For instance, our home galaxy is about 100,000 light years across. So signals from Earth have been going out in an expanding radius of about 100 light years so far.
First just electric noise then modulated morse code and such then audio, then video and data and now it seems clear we are headed for a more quiet RF environment and a hundred years from now there may not even be TV and radio stations as we know them now.
But instead all wifi'd to the hilt so just about every spot on earth can utilize RF signals of a watt or so and at that point the expanding wavefront or RF signature will effectively halt.
So supposing that takes not a couple hundred years but give it a thousand years. So we imagine a moving wavefront 1000 light years in radius which then ceases.
So that wavefront travels through the galaxy and a hundred thousand years later there are no more signals coming from Earth. Doesn't matter why, they will just cease. So if the same thing happens to other technological civilizations, even if they last 10,000 years, there is room for 10 such civilizations to come and go and nobody the wiser.
That is most likely why we have never detected any advanced civilization in our galaxy even though our equipment is sensitive enough to detect US all the way across the galaxy, assuming our signal and that detection happened at the same time.
So chances are, a galaxy gets one advanced civilization at a time. And now it's our turn and we won't find much of ANY advanced life in the galaxy even assuming we get all the fancy sci fi faster than light propulsion systems.
Worm holes, space benders, whatever, we will probably find, say we are able to go out into the galaxy at a million times the speed of light starting a thousand years from now, we could at least get close enough to detect small signatures of life anywhere in the galaxy.
I suspect we will find only ancient dead civilizations, lots of archaeology to study though. Maybe even new technologies we didn't think of but no living advanced life. I have no doubt we will find life of some sort but very unlikely for any of that to be even in the level of ancient Rome.