August 29th, 2016
My book Improbable Planet, due to be released next week, provides the most extensive explanation and documentation to date that the entire universe, every event in Earth’s history, and every life-form that has ever existed must be exquisitely fine-tuned to make possible the existence of human beings. Now, the premise of my book is finding strong support in a soon-to-be-published paper by three astronomers at Harvard and Oxford universities.1
A summary of the content and conclusion of the paper was released to the public in a news release posted on August 1. Within hours the Internet was abuzz with commentary on the news that we humans must be the first advanced life species to appear in the history of the universe.
Most of the web articles focused on the lead author Abraham Loeb’s verbal comment, “We find that the chance of life grows much higher in the distant future,”2 and the implication that though we may be alone now, trillions of advanced species on trillions of different planets will arise in the future. As always, I recommend that laypeople at least read the abstract of the peer-reviewed paper before they draw any conclusions from the popular web articles commenting on the paper. Abstracts of peer-reviewed science research papers are always free of charge to the public and can be easily accessed on the respective journal’s website.
How Likely Is it That Aliens Exist?
In the paper, the three astronomers calculated the likelihood for advanced life as a function of cosmic time and concluded that we humans must be the first on the cosmic scene. In their calculation, they presumed that any life possibly existing in the universe must be like us in that its chemistry is carbon-based. As Fazale Rana and I pointed out in our book Origins of Life, this conclusion was proven correct decades ago.3 The astronomers also presumed that advanced life requires a planet equal or very nearly equal to the mass of Earth. A planet less massive than Earth will lack the strong surface gravity needed to keep its atmosphere from evaporating away. A planet more massive than Earth will accrete too heavy of an atmosphere.
The three astronomers then produced a numerical expression that related the likelihood of life appearing as a function of cosmic time in terms of:
- the nuclear burning lifetime of stars as a function of their mass;
- the population density of stars for different stellar mass values; and
- the probability of Earth-mass planets residing in the liquid water habitable zone.
Their numerical expression ruled out all planets orbiting stars more massive than the Sun. The nuclear burning lifetimes of such stars are not long enough, even in the most optimistic scenarios, to permit advanced life to arise. Even for a star as massive as the Sun, the team judged the possible arrival of advanced life on one of its planets as highly unlikely. That deduction was the basis for their conclusion that we humans must be the first advanced life species to exist in the history of the universe. In other words, we must be alone.
The three astronomers were much more optimistic (with one important caveat) about stars much less massive than the Sun. Such stars can burn up to a thousand times longer than the Sun can. This much longer time, the three astronomers argued, greatly increased the probability of advanced life arising. The caveat, which the popular web articles overlooked, is “unless habitability around low mass stars is suppressed.”4
Habitability around low-mass stars indeed is strongly suppressed. Citing the latest research findings, I make the case for this strong suppression in Improbable Planet. In that book I show that low-mass stars fail to provide the spectral response and luminosity stability that advanced life needs. I also explain how advanced life requires a planet that resides not just in the liquid water habitable zone but in seven other habitable zones as well. Only a star equal to the Sun’s mass affords the possibility of one of its planets residing in all eight habitable zones. In a previous blog article, I described the discovery of a ninth habitable zone—the electric field habitable zone.5 This ninth condition for habitability rules out all low-mass stars.
Don’t Expect an Alien Invasion Any Time Soon
The three astronomers conclude their paper by demonstrating that the probability of advanced life arising must be far more remote than what they calculated. In addition to just the three factors they considered in their numerical expression, they list several more that clearly play roles in limiting the possibility of advanced life arising. They note that the origin of simple life might not occur immediately once a planet becomes “habitable.” They note that advanced life requires:
- very stable habitable zones;
- the Milky Way consuming many very small dwarf galaxies on a regular basis but no large ones;
- a single large moon to stabilize the climate;
- highly fine-tuned asteroid and comet belts in the planetary system;
- a highly fine-tuned orbital structure for accompanying planets;
- a fine-tuned location within the host galaxy;
- fine-tuned features of the host galaxy; and
- a fine-tuned mix of elements in the planet’s core, mantle, and crust.
I describe the critical need for all of these factors in my new book and describe and document dozens more. The bottom line is that nothing less than the intimate, direct, supernatural interventions of the Creator God of the Bible explains why advanced life exists on Earth. As I close in chapter 16 of Improbable Planet, all this fine-tuning design exists so that billions of humans in a very brief window of time can hear and respond to God’s offer of redemption.
- Abraham Loeb, Rafael Batista, and David Sloan, “Relative Likelihood for Life as a Function of Cosmic Time,” Journal of Cosmology and Astroparticle Physics (August 2016): doi:10.1088/1475-7516/2016/08/040.
- Harvard-Smithsonian Center for Astrophysics, “Is Earthly Life Premature from a Cosmic Perspective?” news release, August 1, 2016, https://www.cfa.harvard.edu/news/2016–17.
- Fazale Rana and Hugh Ross, Origins of Life: Biblical and Evolutionary Models Face Off (Covina, CA: RTB Press, 2014), 95–97.
- Loeb, Batista, and Sloan, “Relative Likelihood,” 1.
- Hugh Ross, “‘Electric Wind’ Becomes 9th Habitable Zone,” Today’s New Reason to Believe (blog), Reasons to Believe, July 4, 2016, http://www.reasons.org/blogs/todays-new-reason-to-believe/electric-wind-becomes-9th-habitable-zone.
Subjects: Exoplanets, Sun, Solar System Design