Originally Posted By: jrustles
It comes down to relativity in this case- what seems like an effective idea to us like blasting the Beatles into space, might not be - at all- what they're looking for.
Well, there are certain things that are worth looking for and certain things that aren't worth looking for. Electromagnetic radiation that has an artificial pattern is a good one. Notably, it travels at a pretty good clip and doesn't need a medium. Listening for sound waves from Earth would be idiotic.
The laws of physics don't change for another hypothetical species looking for life elsewhere.
Originally Posted By: jrustles
Or perhaps they already have parts of the galaxy mapped out? Maybe some of them have been checking in on us and our rise and falls of civlization, maybe even long term observation like the evolution of species!
We have part of the galaxy mapped out. That doesn't mean much. Periodically "checking" on us takes some great leaps of faith. They have to find us first, and given the shear numbers of stars out there and the short period that we've been broadcasting, that's an impressive obstacle. Then, they have to get here. That's a bigger obstacle. And periodically checking on our civilizations would indicate they discovered us long before we started any EM transmissions, and I don't buy that for a second. We have one or two candidates for microbial life in this solar system, and we can't even do an exhaustive check yet.
No matter how much you stretch the physics, you have a daunting problem. There are trillions of stars in the known universe. Even taking conservative estimates as to how many could potentially support life, that's a staggering amount to check, no matter how fast one can travel. Of course, when we go to the fringe idea that, "Oh, well life could be totally different than what we consider life," then you have to increase the number of starts to check, right?
The biggest issue with respect to life on other planets, specifically with looking at the Drake equation, is the estimate of the value of L. It's beginning to get reasonably clear that L will be much shorter than original estimates. A civilization emitting detectable signals for much more than a hundred years is questionable, much less hundreds or thousands of years. We simply don't need TV stations pumping out megawatt signals any longer. Radio could follow. Our main concern these days for communication is to be able to communicate effectively with satellites (which doesn't require enormous power) or local cell phone towers, or WiFi 15 feet away.
There is little need to worry ourselves about whether and how aliens are visiting us or watching us with exotic technologies when we can't get a man past the moon. It's daunting.
And certain types of speculation simply don't help. It's easy to say that they're not looking at EM, or they have FTL travel. If one hasn't got some idea of a feasible alternative, then it's just science fiction.
The facts are inescapable. If one wishes to find something, one has to look. When one looks, one has to look for something feasible (i.e. EM radiation), or one has to go and do it (physically or by proxy through a probe), and that's a pile of work considering the number of stars.
To have had aliens visiting ancient man doesn't explain how they found ancient man, who did nothing to enable interstellar detection. That would mean the aliens had to come and physically check. Maybe they had to check Mars, too. After all, we thought it had canals and we are much closer. How many other planets and star systems did they have to check between their home and here, regardless of their speed? Thousands? Millions? Billions?
