Extrasolar planets: a challenge to biblical cosmology?
New methods using increased precision have allowed mankind to answer a fundamental question: Do other stars have planets? Natural philosophers have pondered this question for centuries. Johannes Kepler imagined beings on other planets in his book, The Dream, considered the first work of science fiction. Today’s scientists are finally able to move from fiction to fact. The answer is: Yes! Other stars do have planets. A follow-up question for creationists (and evolutionists) is: what does it mean for our worldview?
The first such planets were discovered by means of wobbles. Planets tug on their host stars as they orbit, causing very slight but detectable oscillations. Later, the transit method was perfected for the Kepler spacecraft. As planets pass in front of their host stars, very slight dips in light intensity can be detected. These measurements are extremely difficult to make, but larger telescopes and spacecraft, high-precision instruments, and software have made it possible to detect their presence, even though they cannot be imaged directly. Over 1,000 planets have been confirmed to date, with another 3,600 Kepler planet ‘candidates’ (unconfirmed possible planets), plus another 192 unconfirmed from other sources.1
Some of the candidates have since proved to be mirages.2
Astronomers are astonished that extrasolar planetary systems look nothing like our solar system. The vast majority of known exoplanets are ‘hot Jupiters’—gas giants very close to their stars, many closer than Mercury is to our sun! Obviously, such planets are not candidates for life. Orbiting in days or even hours, fully exposed to the heat and flares of their stars, they reach enormously high temperatures that would render them sterile even if they had solid surfaces under the dense, hot gas. This has been a big letdown to evolutionists, who expected to find planets arranged like ours: rocky planets close in, and gas giants farther out. Even allowing for ‘selection bias’ (since large planets are easier to detect), the predicted pattern has been the exception rather than the rule. It’s a lesson on not extrapolating a trend based on a sample size of one (the earth).
The discovery of such hot Jupiters has devastated evolutionary theories of planet formation. Those who theorize about the origin of planets thought it impossible for large gas giants to form so close to a star—again, based on our own solar system’s arrangement. The ‘nebular hypothesis’ of mystic Emanuel Swedenborg and atheist Pierre-Simon Laplace in the 18th century was built from the same ‘sample size of one.’ Subsequent theories claimed success at explaining our solar system: rocky material, with a higher melting point, condensed close to the star; while gases and ices, with lower melting points, condensed farther out, beyond the so-called ‘frost line,’ a radius at which solar heat was low enough to prevent destruction of volatile (easily-vaporized) material. This seemed to match the composition of planets in our solar system. Comets were thought to come from pristine icy material at the outer reaches, unchanged since the birth of the sun. Everything happened very slowly, by ‘core accretion’ over millions of years.
Hot Jupiters have all but thrown that thinking out the window. It dawned on cosmologists that if gas giants did form farther out, they must be subject to rapid migration inward. Since it would only take a few thousand years for their components to spiral into their stars on conveyor belts of dust and gas and be destroyed, hot Jupiters had to have formed rapidly. When I was working at JPL3 in 2006, I remember hearing noted cosmogonist Alan Boss in a lecture sheepishly defending his new ‘heretical’ model of planet formation. He called it ‘disk instability’. It was a proposal for getting gas giants to form in less than a thousand years by imagining knots of material in a dust disk collapsing quickly.
Other astronomers are reluctant to abandon the old nebular hypothesis, even though it has numerous problems of its own. For instance, particles in a dust disk less than a kilometre in diameter do not accrete; they disrupt. Any ‘planetesimals’ (small bodies thought to be growing into planets) must grow fast enough to clear out a path in their orbits before inward migration sets in. Both theories, therefore, require rapid formation of planets.
The ‘bottom-up’ theories of evolutionists have effectively been falsified. For this reason, creationists should defend a ‘top-down’ model of planet formation. Believers in God should not be surprised that God created stars with orbiting bodies from the beginning. The top-down model is supported by the principles underlying the Second Law of Thermodynamics, which reveal a relentless tendency for things to become more disordered over time.4 That is exactly what we see: stars and planets winding down and wearing out. Some stellar dust disks that were thought to be forming planets are now believed to be the ruins of destructive collisions. If it were not for God’s unique design and care for our earth, it would not long survive.
Because evolutionists desperately want to prove that the origin and evolution of life is common in the universe, the search for habitable planets has intensified. Once again, though, the observations point to earth-like planets being extremely rare. At this time, the Planetary Habitability Laboratory website5 lists only one earth-size planet candidate from Kepler data out of thousands. Another 48 are labelled ‘potentially habitable exoplanets’, but these are all in the ‘super-earth’ category: much larger than earth, which creates additional habitability issues.
Other factors have thrown a wet blanket on hopes for life. It’s not enough for a planet to be in the ‘continuously habitable zone’ of a star, a radius where water can remain in a liquid state. The star must be quiescent, not subject to large flares or excessive stellar winds. The planet’s orbit must be nearly circular, and not given to surges in obliquity (tilt). The planet must be chemically and thermodynamically constructed to support water. The planet’s star must have the right chemistry to avoid giving off excessive ultraviolet light, which would be deadly to life on its planet. About a dozen factors are now seen as constraining the ‘habitable zone’ to a small fraction of stars.
Another problem is that about 80% of all stars are red dwarfs. These are about a third as large and about a thousandth as bright as our sun, so we can’t see them with the naked eye. For a planet to be in a red dwarf’s habitable zone, it would need to be so close that it would be tidally locked, i.e. one side always facing the star. So one side would be frying in perpetual day and the other freezing in perpetual night.
Issues for creationists
As observational precision improves, we can expect that more planets will be found, and more of these may prove habitable. (That doesn’t mean they are inhabited—just habitable.) In future years, astronomers hope to detect ‘biosignatures’ in exoplanet atmospheres: gaseous or spectral indicators of life that would be difficult to explain abiotically, such as excesses of methane or carbon dioxide, or lots of green in the spectrum.
After 50 years of failure, some SETI6 people still scan the skies for alien radio messages. It’s highly doubtful, however, that any such indicator of intelligence will be received in the foreseeable future.
Let’s suppose that, against all odds, they do find life. What would it mean for biblical interpretation? It depends on the type of life discovered. Intelligent life is ruled out, because we know from Heb. 9:24–26 that Christ died for sins once, and only once—for the sins of humanity. He did not have to “suffer repeatedly since the foundation of the world” (i.e., the universe). Nowhere in Scripture is there any hint that Christ became incarnate for the sins of any other beings. For this reason, it is highly unlikely that alien intelligence (as opposed to fallen angels impersonating aliens) will ever be found.7 But what about non-sentient, e.g. microbial, life? Though one cannot rule it out, it is highly unlikely that this exists, either. All of creation seems focused around mankind on earth, and the plants and animals are part of our life support system.
All life is intelligently designed. Only humans are made in the image of God, have fallen into sin, and are in need of salvation. Christ Jesus provided grace uniquely to humans by His death on the cross and His glorious Resurrection. Unverifiable speculation about life on other planets may be fun, but in the end, it is futile. We can know for sure what we need to know: that God has provided for our physical and spiritual needs on our superbly designed planet.8
References and notes
- Planetary Habitability Laboratory, phl.upr.edu. Return to text.
- Crosswell, K., Science Shot: Some Young Planets May Be Mirages, news.sciencemag.org, July 2013, accessed November 2013. Return to text.
- Jet Propulsion Laboratory (NASA-affiliated). Return to text.
- Wieland, C, World Winding Down: a layman’s guide to the second law of thermodynamics, Creation Book Publishers, Powder Springs GA, 2013. Return to text.
- See ref. 1. Return to text.
- Search for Extra-Terrestrial Intelligence. Return to text.
- Bates, G., Did God create life on other planets?, Creation 29(2):12–15, March 2007; creation.com/life-planets. Return to text.
- See also Harwood, M., Created to be inhabited, Creation 35(3):38–40, July 2013; creation.com/earth-design. Return to text.