Making contact with aliens: the subject of many a sci-fi story, and a variety of imagined outcomes. Though no one knows what will happen if we encounter intelligent extra-terrestrial life, scientists are dividd on how we should proceed.

SETI, the Search for Extra-Terrestrial Intelligence, has been searching for signals from said ETs for many years with no positive results. Of course, there have been interesting signals, but nothing specifically indicative of intelligence.

Scientists from SETI are turning up the volume on a debate that has been raging for several years over whether we should start actively transmitting messages into outer space rather than continuing to passively scan the skies while only leaking weak radiation from our surface activities on the planet. In a press conference at the annual meeting of the American Association for the Advancement of Science in San Jose this week, Douglas Vakoch presented the question, and stated that beginning to transmit in an active, directed fashion would be part of humanity "growing up". He also wondered if it would be the approach to let us actually "make contact" with aliens.

On his side is scientist and science popularizer, Seth Shostak, who rapidly and eloquently listed the reasons that behoove us to set resources to an active search for intelligent life beyond our solar system. The primary argument being that our planetary radio leakage has probably been enough to alert any reasonably advanced civilization to our presence, so why not start chattering in earnest? There have also already been several active communication attempts by humans, just not on a repeated basis. Additionally, limiting our radio-frequency output will be a burden to technological and cultural development that future generations should not have to bear.

David Brin, popular science fiction author and physicist, countered that we have no idea who is out there or what their motivations might be. We certainly aren't invisible to anyone looking for signals of life in the universe, but we don't want to go looking for trouble. He stressed that this discussion of sending messages to extra-terrestrial intelligence (METI as opposed to SETI) should considered by all of humanity, as the outcome will have global effects.

Brin later wondered how prevalent altruism, a behavioral strategy in which organisms do nice things for others with no thought for themselves, actually is in in nature. How often it has evolved should be a question of concern, as it would likely be a large part of alien cultural development.

If altruism is a rarity, Brin postulated that quid-pro-quo, or the concept of trading things of equal value, would be more universally understood. In a future scenario where we need to trade with ETs, information will be our most valuable asset, and should be guarded and valued as such.

A further argument against embarking on activating a METI program, involves existential considerations of risk, like planetary protection, which David Grinspoon, an astrobiologist, detailed as the concern of contamination. We exist in a microbial world that we are only just beginning to describe, let alone understand. There is a high probability that aliens carry microbes of all sorts that would be completely foreign and devastating to our immune defenses. The same goes for the effect of our microbiota on any aliens we might meet.

All of these arguments, pro or con, are completely moot in light of economic considerations. It has been calculated that it would cost to send repeated or continuous signals of appropriate strength to a small number of nearby stars using current technology would be minimal (on the order of $640 per year). But, to expand that search would require new construction and new technology, not to mention immense energetic input.

Frank Drake, the congenial scientific namesake of the Drake equation, said in conversation that despite the many potential benefits of making contact with an advanced life-form, "it would be silly to send messages now." For starters, we won't be able to benefit from such a project for at least 50-100 years. So, it would be a waste of resources at this point in time. Our time, money, and energy would be better spent searching as "sending messages is not efficient."

According to Drake, we should focus our resources on exploring and utilizing our own solar system as "intelligent species wouldn't be travelling between the stars." Why is that? Moving between stars is cost prohibitive. He went on to say that a 100 year space flight to a nearby star at one-tenth the speed of light (the fastest tolerable to the human body) would require the equivalent of the full power output of the United States for 200 years… and, that doesn't include the power needed to stop or land.

Only the most advanced civilizations will have moved beyond their own solar systems. It's just cheaper to stay home, and listen.