Defining Life

A book came out several years ago called Rare Earth. It was written by a pair of scientists arguing that the human race is likely alone in the universe because life as we know it thrives only within a very narrow band of set circumstances. Did you catch the same caveat I did when I first read the book? "Life as we know it". Turns out, since the book was published, life as we know it, and the conditions under which it can and will thrive, has been expanded several times, so, too has the habitable zone - the boundry in a solar system wherein one could assume life forms might be able to survive. What if "life as we know it" is too limiting? The major issue, of course, is that life as we know *is* all we know. It's dreadfully difficult to look for something when you can't describe it. Scientists can't agree on whether or not viruses are alive. How can you search for life that isn't as you know it when you can't even define what you do know? Now, physists are suggesting SETI - the folks scanning the radio frequencies of the skies for an ET phoning anyone at all - is too narrowly focused, that the search for alien intelligence is defined based on human, radio technology that is increasingly being left in our own past. Scientists urged investigators to broaden not only their search, but also their thinking by looking into our future and make some educated guesses about how other living things might give us clues as to their existence. The linked article offers another link to a detailed list of some of the scifi suggestions. For those of us feeding our imaginations, the next obvious question is what happens when your theory pans out and you find signs of an alien civilization? How pleased (or not) is that race about having been seen? And depending on how "life as we know it" they are, how much trouble is your hero or heroine in?