Goldilocks and the Four Moons

by Dr. Neal Doran
January 11, 2011

After following the report of a distant, Earth-like planet in the scientific literature, a Time magazine article reminded me of the caution required in reading news reports on science. Artistic renderings of this planet’s red dwarf “sunsets” can be found on the Internet, but what should a properly informed scientific position be for claims such as these? How should we as Christians view these so-called “findings?” As with so much of what today is presented as scientific fact, I would suggest a respectful skepticism.

The reason is that finding a planet like Earth anywhere in the universe is extremely unlikely. Gliese 581 g is a candidate planet circling a red dwarf star in the Libra constellation, 20 light years away. The rarity of such a find makes it newsworthy. If you are looking for a world where life might thrive, a planet must be at the right temperature for water to exist in liquid form. Therefore, it needs to orbit its sun, or star, in the so-called “habitable zone.” Astronomers refer to such elusive worlds as “Goldilocks” planets, celestial bodies in which, like the children’s story, everything must be “just right” -- not too hot, not too cold. Gliese 581 g seems to fit these minimum criteria. And while no one knows whether the planet actually contains so much as a drop of water -- another requirement for life -- proper temperature is nonetheless one of many of life’s requirements.

Yet the discovery in itself raises a more important question. For instance, if such a discovery is so unlikely -- the odds so remote of duplicating earth’s almost immaculate fusion of favorable conditions -- why do scientists continue the search? The primary motive of researchers seeking the existence of such planets is rooted in the scientific speculations of the 1940s and ‘50s. The Goldilocks planet expectation is, in fact, an echo of something known as the “evolutionary synthesis.” Since theorists concluded that the cosmos teemed with life, the logic followed that if life evolved on Earth, then the chemical evolution of life (a.k.a., abiogenesis) must happen as a rule -- not an exception -- throughout the cosmos. Why should Earth be unique?

Jupiter's moon Europa

The Goldilocks principle drives searches in our solar system as well. Similar to the Goldilocks scenario, Jupiter’s four largest moons provide some life-favoring conditions. Astronomers named the moons after four of the mythological Jupiter’s many divine dalliances: Europa, Io, Ganymede and Callisto. These caught the eye of none other than Galileo, who tracked the orbits exactly four hundred years ago. They are the most observable of Jupiter’s 63 moons, visible today even with a backyard binocular gaze. Three moons have evidence of liquid water while a fourth (Europa), remarkably, has an ocean. An amazing photograph later captured a volcanic eruption in process on Io (thus showing heat). Notes Harvard astronomer David Charbonneau, “What you want (for life) is a nice toasty ocean with a little bit of atmosphere.” Contrast this with the paucity of information we have of “exoplanets” such as Gliese 581 g, which reveal themselves as mere flickers of light across 20 light-years. To quote the TIME article: “Detecting a planet this small is monstrously hard... The instruments you use to detect tiny back-and-forth motions in the star -- motions caused by the orbiting planet’s gravitational tugs, which are often the only way to infer that worlds exist at all -- simply weren’t sensitive enough.”

Ice patterns on the surface of Europa provide evidence that liquid water exists below.

Let me stop to clarify by asking a question: should the prospect of life on other planets be rejected on purely theological grounds? In my view, no, Scripture is silent. Should believers be characterized by a reflexive anti-intellectualism that dismisses such questions out of hand? No. Properly pursued and verifiable, scientific knowledge is always good, and that includes attempting to answer questions such as these. The problem, rather, is science’s almost evangelical pursuit of poorly evidenced speculations. Forget the fact that there are far more hurdles in obtaining a Goldilocks scenario than was ever dreamed 50-odd years ago. The real question is, what is driving these philosophically driven speculations which, to judge from the cold, hard data, remain objectively void of empirical validation? Where testability is lacking, shouldn’t such sketchy claims by scientists be consigned to the realm of fiction?

At least Jupiter’s Europa leaves open a door for testability. This open door, in turn, shows the difficulty of the pursuit. For example, Europa’s estimated ocean depth is 60 miles. (For comparison, our deepest ocean trench is a paltry seven miles.) Such depth would create a crushing water pressure without parallel on Earth. Consequently, this water would also be extremely saline (and likewise hostile to life). On Earth, coastal evaporation reduces ocean salinity. But Europa lacks both continents and sufficient heat to drive evaporation. No such scientific observation -- let alone informed inference -- is possible for exoplanets such as Gliese 581 g. Verification of oceanic salinity -- if oceans exist at all -- is unobtainable through the lens of a telescope. This is particularly true when all we will ever see is its sun. Jupiter’s moons at least allow an occasional satellite flyby.

The Evangelical community is too often polarized between a derisive disregard of science, on the one hand, and unconditional embrace of its every assertion, on the other. Scientific research is good. Yet speculative ideas beyond the reach of physical investigation are frequently the fuel for ideologically driven bandwagons. As a believer, I am open to a strongly evidenced case that an extraterrestrial body may contain life. Yet my philosophical framework provides no reason to think this is a fruitful use of resources. Scientific philosophies that remove God from reality eventually produce alternatives to His existence. Unfortunately, these seem to result in zealous pursuits of the highly improbable. As a result, the embrace of the nearly impossible becomes a passionate crusade.

If weak speculation was not problematic enough, my search of the scientific literature revealed an additional problem. Astronomers now doubt that Gliese 581 g exists at all; it may have been the result of an error in data analysis. This underscores my point: when both reason and evidence fail, skepticism of theoretical conjecture is the best path.

Dr. Neal Doran teaches biology at Patrick Henry College. His fields of interest include invertebrate and micropaleontology, morphometrics, the metaphysics behind modern biological thought, and origins.