Detection at a distance is not that easy. The primitive analog radio signals we used until about 1995 are easy to recognize, because they are so simple. The digital, encoded, encrypted signals we use today are much more difficult to distinguish from naturally occurring signals. They tend to be more efficient and to vanish into noise much more quickly. So in our case, the time window during which we were visible in space was about 25 to 30 years. We only recently became capable of detecting the light of entire planets, what makes us think we can detect their radio signals?
Regarding the more general problem: what about economics? Even if it is technologically viable for us to go into space, it is remarkably expensive. We couldn't sustain a Moon program, for all its scientific interest. So we need a pretty big return on investment to do further space exploration.
To me, there are really only two options:
1) Speed of light can't be broken, and colonization only happens by losing any practical contact with your descendants (a ping time of 1s is bad enough, think about 100 years). This reduces its economic appeal to practically zero. No return on investment at all. Not even intellectual satisfaction: you will not even know in your lifetime if your expedition was a success. So why bother?
2) Faster-than-light travel is possible, and relativity tells us it's basically equivalent to time travel. Now, just try to imagine how well our own economy would survive the availability of time travel... This is one thing that Star Trek or Star Wars or Galactica never get right, it's a problem they never consider because it's too hard to think about it. If you can jump or warp or whatever, then to the best of our knowledge, you can travel back and forth in time. How does a civilization survive this? I have no idea. A good example of singularity.
One final thought: the Fermi paradox always start with the premise that we don't see aliens. But most serious work on UFOs claims that a fraction of UFOs can't be explained away. In short, some UFOs appear to be artificial, to exhibit intelligent behavior, and to show technological capabilities well beyond our own. I'm quite surprised to write this comment at a point where there are 86 comments, and I'm the first one writing UFO. Taboo?
Regarding the more general problem: what about economics? Even if it is technologically viable for us to go into space, it is remarkably expensive. We couldn't sustain a Moon program, for all its scientific interest. So we need a pretty big return on investment to do further space exploration.
To me, there are really only two options:
1) Speed of light can't be broken, and colonization only happens by losing any practical contact with your descendants (a ping time of 1s is bad enough, think about 100 years). This reduces its economic appeal to practically zero. No return on investment at all. Not even intellectual satisfaction: you will not even know in your lifetime if your expedition was a success. So why bother?
2) Faster-than-light travel is possible, and relativity tells us it's basically equivalent to time travel. Now, just try to imagine how well our own economy would survive the availability of time travel... This is one thing that Star Trek or Star Wars or Galactica never get right, it's a problem they never consider because it's too hard to think about it. If you can jump or warp or whatever, then to the best of our knowledge, you can travel back and forth in time. How does a civilization survive this? I have no idea. A good example of singularity.
One final thought: the Fermi paradox always start with the premise that we don't see aliens. But most serious work on UFOs claims that a fraction of UFOs can't be explained away. In short, some UFOs appear to be artificial, to exhibit intelligent behavior, and to show technological capabilities well beyond our own. I'm quite surprised to write this comment at a point where there are 86 comments, and I'm the first one writing UFO. Taboo?