Gliese 581g and the Question of Intelligent Life

As I'm sure you've heard by now, there may be a new kid on the liveable planet block, Gliese 581g. This is the first exoplanet that has the potential to have a solid surface and that is in the habitable zone around its star where liquid water can exist. We all immediately thought, "could there be life?" and one SETI researcher claims to have a possible signal.

There really is no telling yet how many potentially habitable planets there are in the galaxy, though one could make an estimate based on the solar system and Gliese 581's system.

However, just being in the "Goldilocks zone" is not enough to truly be habitable to life as we know it, as we can see from Mars in our very own solar system. But to find such a planet a mere 20 light-years away is still tantalizing. After all, if there was an intelligent civilization there, we could have a short conversation in a human lifetime!

Ragbir Bhathal, an astronomer affiliated with the Australian SETI effort, says that he detected a blip of light, similar to what optical SETI projects might expect from an intelligent civilization, in the direction of Gliese 581 two years ago.

Now, one blip does not a solid detection make, and for decades SETI researchers have been excited then disappointed by strange signals that never repeat. If Bhathal produces this data for scrutiny from other scientists, repeatability would still be needed before a detection of extra-terrestrial intelligence could be claimed. So don't get your hopes up just yet.

But still, if habitable planets are fairly common in the galaxy, as the existence of Gliese 581g suggests, that still leaves me with a burning question... Where is everyone?

This question was famously posed over lunch by Enrico Fermi in 1950, thus it is now called the "Fermi Paradox." In a galaxy where habitable planets could have formed as many as 10 billion years ago -- Gliese 581g, for example, is approximately 8 billion years old -- then where are the civilizations that had a 5 billion year head start on us? Homo sapiens have only been around for 150,000 years, so imagine what they would be like!

If you are skeptical of the scores of UFO and abduction reports, as I am for several reasons, then you are left with three possibilities. One is strangely reminiscent of Star Trek's prime directive, that they are here, but are careful to ensure that we don't know about it. Or, intelligent life has arisen elsewhere, but they don't explore the galaxy, either for lack of trying, because it is too difficult, or because they blow themselves to bits in the process. Or, we truely are the first, or among the first, sentient beings in our galaxy.

When I asked my "Life Beyond Earth" students which of those three scenarios they thought was most likely, they leaned towards the second explanation, that something has prevented previous civilizations from colonizing the galaxy. However, they all hoped that the first scenario was really the true one! I can't say I blame them. How do you think, and hope, that the Fermi Paradox can be solved? Maybe, the truth is something even stranger than we can imagine just yet.