Gilese 581 discovered for the first time....again

I'm finding it very strange that everyone's all a tizzy about the discovery of a potentially habitable planet, Gilese 581. This planet was discovered over three years ago. I remember this because it was an important consideration in the Fermi talk I delivered in Chicago the same year. Its discovery also motivated me to write about the Rare Earth Delusion. I'm not sure I understand all the sudden attention.

** ADDENDUM: 2010.10.05: Okay, everything is now illuminated: As my reader Richard Leis, Jr. points out, "The discovery of Gliese 581 c was announced in 2007. Last week's announcement was Gliese 581 g. C was initially considered a good candidate for potential life, but later calculations suggested it was actually outside the star's habitable zone. G is considered a better candidate because calculations place it more firmly within the habitable zone." **

Well, whatever. What's important to note is that (1) it reaffirms the notion that we (likely) live in a biophilic Universe and (2) its presence deepens the disturbing nature of the Fermi Paradox. As a potential data point that works to increase the value of n in the Drake Equation, it serves to reinforce the suggestion that, while we find ourselves in a Universe that is likely teeming with life, it's not one that's teeming in space-faring civilizations. Consequently, its discovery is not exactly good news.

Here's what I wrote back in April of 2007 when Gilese 581 was first discovered:

Wow, the blogosphere has been absolutely gushing these past few days over the news that an Earth-like planet may have been discovered in the 'hood. This planet may boast a moderate climate that could conceivably support life and is only 20 light years away.

Not surprisingly, this news has caused a number of pundits to fantasize about jumping into their rocketships and bidding adiós to our polluted, war-torn and diseased planet.

But not so fast, amigos. While many have misguidedly jumped on the bandwagon to the stars, a number of bloggers have gotten it right.

In his article, "'Don't Pack Your Bags Just Yet", Jamais Cascio notes that, "By the time we have the technology that would make a 20 light year trip even remotely plausible (the fastest space craft yet made would still take thousands of years to get there), we probably won't be all that interested in living in a watery gravity hole anyway. Nope -- give us some nice, massive gas giants to convert to computronium!"

Michael Anissimov points out that we have a human hospitable planet right here that we’ve barely even begun to use. He also argues that "even if we did need to leave the Earth, there is a tremendous amount of raw materials for space colonies right next door in the form of carbonaceous asteroids, which make up about 75% of known asteroids." Moreover, warns Anissimov, "we should think carefully before sending off colonists to far-away places without ensuring that they’re capable of protecting the fundamental freedoms of their citizens." Specifically, he worries that a blight may come back to haunt us (which also reminds me of the Honored Matres of the Dune series).

And as Tyler Cowen noted, "Are earth-like planets so common? That probably means lots more civilization-supporting planets than I had expected. But where are the alien visitors? As suggested by the Fermi paradox, we must revise our priors along several margins, one of which is the expected duration of an intelligent civilization."

Indeed, Cowen is on the right track. A primary argument used to reconcile the Fermi Paradox is the Rare Earth Hypothesis. This line of reasoning suggests that we haven't been visited by ETI's because life is far too rare in the cosmos.

But if we have discovered an Earth-like planet as little as 20 light years away, it's not unreasonable to suggest that our Galaxy must be absolutely teeming with life. This would seem to be a heavy blow to the REH.

So why is this bad news? It's bad news because our biophilic universe should be saturated with advanced intelligence by now...but it's not. The Fermi Paradox is very much in effect as a profound and disturbing unsolved mystery in astrosociobiology, philosophy and futurism.

Are all civilizations doomed before getting to the Singularity? Or is there something else at work here?

The 'Rare Earth' delusion

In my experience, the most common solution given to the Fermi Paradox is the Rare Earth hypothesis -- the idea that life in the Galaxy is exceptionally rare and that planets like ours are freakishly uncommon. For many, this conveniently explains why we haven't been visited by little green men. Or more accurately, extraterrestrial machine intelligences.

I've always thought, however, that given cosmologically large numbers that this sort of thinking is symptomatic of our small minds and limited imaginations. It's easy for us to throw up our hands and sheepishly declare that we're somehow special. Such a conclusion, however, needs to be qualified against the data involved, and by the mounting evidence in support of the notion that ours appears to be a life-friendly universe.

What Do You Mean, 'Rare'?

Let's pause for a moment and look at the numbers.

Recent figures place the total number of stars in the Milky way at an astounding three trillion. I don't need to tell you that that is a huge number. But given how poor the human mind is at groking large figures I'm going to play with this number for a bit:

• 3 trillion fully expressed is 3,000,000,000,000 (12 zeros)
  
• As an exponent it can be expressed as 3 x 10¹²
• Re-phrased, it is 3 thousand billions, or 3 million millions

Which necessarily leads to this question: given such a ginormous figure, what does it mean to be rare?

Even if the Earth is a one in a million occurrence, that means there are still 3 million Earthlike planets in the Galaxy (assuming one Earthlike planet per star). Does that qualify as rare? Not in my books.

If, on the other hand, the Earth is a one in a billion occurrence, then there are only 3,000 Earths in the galaxy. That sounds a bit more rare to me -- but one in a billion!? Seriously?

We also have to remember that the 3 trillion stars only accounts for what exists right now in the Milky Way. There have been well over a billion trillion stars in our past Universe. As Charles Lineweaver has noted, planets began forming in our Galaxy as long as 9 billion years ago. We are relative newcomers to the Galaxy.

Our Biophilic Universe

But all this numerological speculation might be moot. We're overlooking the mounting evidence indicating that we live in a universe exceedingly friendly to life. What we see in the physical laws and condition of the universe runs contrary to the expectations of the Rare Earthers.

Indeed, we are discovering that the Galaxy is littered with planets. Scientists have already cataloged 321 extrasolar planets -- a number that increases by a factor of 60 with each passing year. Yes, many of these are are so-called "hot Jupiters," but the possibility that their satellites could be habitable cannot be ruled out. Many of these systems have stable circumstellar habitable zones.

And shockingly, the first Earthlike planet was discovered in 2007 orbiting the red star Gilese 581. It's only 20 light-years away, 1.5 times the diameter of Earth, is suspected to have water and an atmosphere, and its temperature fluctuates between 0 and 40 degrees Celsius.

If we are one in a billion, then, and considering that there are only 0.004 stars per cubic light-year, what are the odds that another Earthlike planet is a mere 20 light-years away?

Indeed, given all this evidence, the Rare Earthers are starting to come under attack. Leading the charge these days is Alan Boss who recently published, The Crowded Universe. Boss estimates that there may be billions of Earthlike planets in the Milky Way alone. "I make the argument throughout the book that we already know that Earths are likely to be incredibly common—every solar-type star probably has a few Earth-like planets, or something very close to it," says Boss. "To my mind, at least, if one has so many habitable worlds sitting around for five billion or 10 billion years, it's almost inevitable that something's going to start growing on the majority of them."

Life Abounds

And it gets worse for the Rare Earthers. They also have to contend with the conclusions of astrobiologists.

It's a myth, for example, that it took life a long time to get going on Earth. In reality it was quite the oppoite. Our planet formed over 4.6 billion years ago and rocks began to appear many millions of years later. Life emerged relatively quickly thereafter some 600 million years after the formation of rocks. It's almost as if life couldn't wait to get going once the conditions were right.

We also live in a highly fertile Galaxy that's friendly to extremophiles. The Panspermia hypothesis suggests that 'life seeds' have been strewn throughout the Galaxy; evidence exists that some grains of material on Earth have come from beyond our solar system.

Recent experiments have shown that microorganisms can survive dormancy for long periods of time and under space conditions. We also now know that rocks can travel from Mars to Earth and that simple life is much more resilient to environmental stress than previously imagined. Consequently, biological diversity is probably much larger than conventionally assumed.

Common Earth

My feeling is that the Rare Earth hypothesis is a passing scientific fad. There's simply too much evidence growing against it.

In fact, the only thing going for it is the Fermi Paradox. It's comforting to think that the Great Silence can be answered by the claim that we're exceptionally special. Rare Earth steers us away from other, more disturbing solutions --namely the Great Filter hypothesis.

But such is the nature of scientific inquiry. We're not always going to like what we find, even if it is the truth.

As for the Fermi Paradox, we'll have to look for answers elsewhere.