Monday, March 01, 2010

Not So Privlidged Planet

Oh, poor Creationists.

One of their favorite claims is that we live on a Privileged Planet that is just right for us. Thus magic man done it.

Unfortunately, science keeps coming along and showing that our egos are misplaced. We're special, but not magically so. We evolved big brains capable of deep thought, but it shares a common ancestor with all life.

Even our planet is a pale blue dot in a vast and inspiring universe. But Creationists constantly try to claim that this solitary orb is so amazingly perfect that it must have been made that way.

But even this claim is contradicted by the evidence. A new paper on arXiv takes a look at just how habitable planets similar to Earth can be.

The authors modeled Earth clones and varied numerous components of the system from the amount of ocean, to the eccentricity of the orbit, to the spin rate of the planet and looked to see just how far they could push them before the planet either froze into a snowball or became prohibitively hot.

Oh, the poor creationists. Their "privileged" prediction fails (not that this is surprising since previous work of Kasting et al. (1993) have shown the "habitable zone" is at least 0.95 to 1.37 AU).

The new paper suggests that eccentricity isn't an overly prohibitive constraint for planets. This is good since "40% [of exoplanets with measure eccentricities] are on more eccentric orbits than Pluto (e = 0:2488) and ~10% are on orbits with eccentricities >0.5." Surprisingly, for "planets with eccentricity 0.5... [the] greatest habitable semimajor axis can vary by more than 0.8 AU (78%!)"

This would be like Earth moving in as close as Venus and as far as Mars every orbit! According to Creationists this would be certain doom! Shame on reality for spoiling all the fun.

Ultimately, the most important factor of all the ones they simulated was the amount of ocean. Thanks to the high specific heat of water, it moderates the temperature even under large changes in eccentricity.

Regardless, the Creationist claim that Earth is so perfect for life just took another blow.

Perhaps one day the Creationists will actually notice.


Wayne said...

This study is very interesting, but you may be reading a wee bit too much into it. Liquid water oceans are certainly something we expect for habitable worlds, but that doesn't necessarily mean that life will originate or thrive over the long term (or develop intelligence or etc. etc. I won't go through the entire Drake equation). Clearly, there's more to the success of life on Earth than being in the "habitable zone", that's just a necessary precondition. When I was first introduced to the Drake equation in grad school, I was shocked that my professor used "2" as the number of habitable planets per planetary system, on the strength that "Venus and Mars are both right on the edges". One of the few terms we can pick with any certainty, and he goes for one MORE optimistic than our own Solar System? I always thought that was silly, and this study reminds me of that sentiment. There's nothing wrong with saying that life COULD exist on a wide range of worlds, but to be anywhere as successful as life on Earth has been I think requires a lot more "tuning".

Nicole said...

I read that pair of papers yesterday as well! They were pretty interesting. However, although the habitable zone is certainly increased for the larger eccentricities that we expect to see, the planets in these models, I think, oscillate through several "snowball" phases, which would make it difficult for rather complex life to evolve over time. A large ocean would certainly have some tempering effect, but it'll be quite clear that "we're not in Kansas anymore" if we do find one.

Can't wait for Kepler results... eeeeee!!!