This is sort of a rhetorical question but here goes, does it pay to search for extraterrestrial intelligence (SETI)?

Of course it pays, what an amazing discovery it would be to find a signal from another world, right? What could be a bigger game-changer in human existence when/if we do find intelligent (or any life) out there? Imagine the implications in our thought, education, policies, and religion! I'm anything but an expert but I do think there is some validity in the famous Drake Equation (http://en.wikipedia.org/wiki/Drake_equation) which is basically the statistical likelihood based on many values placed into an equation to life existing somewhere else in our galaxy.

Wouldn't we have to be rather egotistical to believe the we're the only "ones" out there? Based on the principle of mediocrity, there is nothing THAT special about earth, that is, unless you include specific religious faiths. If we take a step back though, and just examine actual evidence, there are clear-cut reasons we have life on earth; orbiting within the "habitable zone" of our star, being the biggest reason. Plate tectonics being another which gives the earth recycling properties that assist in temperature regulation. Still others, our atmosphere and magnetosphere. There are ~300 billion stars in our galaxy and it is widely accepted that there are close to the same number of galaxies. If we are fair, we won't multiply those numbers together to get an idea of how many planets could have life. Most galaxies aren't as big as our Milky Way, most planets don't lie in the habitable zone of their stars, etc. Regardless though, we're talking about a number (sextillion) with 21 zeros after it. Given those numbers, it is hard to believe there isn't some other forms life out there. Great, we just need to find it. Well, now the real problems arise.

The closest star to us is about 4 light years away so sending a message and getting a reply would take 8 years. That is for the closest star! For the exo-planets around "neighboring" star systems that have been discovered in the last 20 years, the average distance is much greater, in the area of 1000 light years. Let's say we "hear" a message from star system that far away. It would take 1000 years for our reply to get to them. That is a 2000 year round trip. What is the likelihood of our civilization even being around to recieve the following reply. Talk about a long distance pen pal!!

The distance problem is the easiest to consider. According to the Fermi Paradox (http://en.wikipedia.org/wiki/Fermi_paradox) there are many more.

- It is the nature of intelligent life to destroy itself. Given the time (>13 billion years) and distance (>13 billion light years) we're talking about, how could our civilization exist at the same "time" as another while coincidentally intercepting communication? It wouldn't happen right? Well, except that there are somewhat in the area of 6 sextillion other star systems out there. That's a lot. My brain already hurts.

- It is the nature of intelligent life to destroy others. Some argue that we must be alone because if there were other intelligent life, it would have found and destroyed us long ago. My problem is that there are 6 sextillion other star systems out there!!! Those aliens could be traveling at the speed of light and not even come close to visiting all the star systems. Have I mentioned how many there are? Here's another thought: imagine designing the routing system for a trip around the universe destroying all other life that would maximize energy/fuel and time. And we thought airlines had a tough gig!

- It is too expensive to spread out in the galaxy. Our civilization can't even afford/prioritize health care for everyone. Missions mere millions of miles throughout our solar system costs astronomical amounts of money. Maybe there are more advanced species elsewhere who have mastered the ability to keep printing more and more money arbitrarily without destroying the value of that money. That was meant to be a joke.

- We haven't been searching long enough. Not only that, but we haven't been broadcasting long at all. Sort of the whole time/distance problem all over again.

- Technical problems. We aren't listening for the right frequency. Perhaps our technology isn't at the same level as another intelligent lifeforms. Perhaps other lifeforms in the outreaches of space have a better understanding of physics and technology and communicate in a way we can't even dream of.

- Other intelligent life chooses not to communicate. If we were smarter, wouldn't we try to shield our communication a little bit better? Wouldn't it be potentially dangerous?

- Other lifeforms are here already, we just can't detect them. This is my favorite. We're just one big science experiment or like a zoo where other lifeforms come to watch us. I've read a similar argument regarding the existence of god and his non wiliness to communicate with us.

A lot of these points support the Rare Earth Hypothesis (http://en.wikipedia.org/wiki/Rare_Earth_hypothesis). I just don't buy it though. What really makes us so special?