The Fermi Paradox

I’ve wanted to talk about the apologetic worth of the Fermi Paradox and the Drake Equation for sometime. Now a recent paper on arXiv ( gives me the excuse, and some fascinating numbers to motivate discussion.  First a warning though, this paper is a preprint.  While submitted to a reputable journal (Proceedings of the Royal Society of London A), it has not undergone peer review.  As such one should take the results cautiously as the community is still coming to terms with this topic, as the paper shows.

So what is the Fermi Paradox?  Originally posed by Enrico Fermi in 1950 it goes something like this.  First assume that the 4.5 billion years (Gyr) it took our planet to evolve to its current stage of development is the average amount of time it takes for an intelligent species to arise.  If this is the case then there should be plenty of opportunities for intelligent life to evolve elsewhere in the galaxy as the galaxy is approximately 9 Gyr old.  After all there are about 250 billion stars in the galaxy and plenty of time to fit in the 4.5 Gyr needed to get to our current state of affairs.  In addition to traverse all the stars in the galaxy would only take roughly 10-1000 Myr (million years) assuming sub-light travel speeds.  As such there is plenty of time for an intelligent species to traverse the galaxy multiple times over.  Given all this we should see signatures of alien intelligent life all over the place but we only see ourselves.  So where are they?

From the opposition direction comes the Drake Equation.  It tries to estimate how many intelligent space faring civilizations there should be in the galaxy.  By combining estimates of how many earth-like planets there are, how many have given rise to abiogenesis, how many have had organisms evolve to be intelligent, and so on you can get a ball park figure as to how many civilizations you would expect to find.

Both of these are classic SETI (Search for ExtraTerrestrial Intelligence)/astrobiology thought experiments.  I taught them both to undergrads in graduate school.  They are great thought experiments because both are exceedingly sensitive to your biases. This is because we lack hard data to back up the numbers plugged into the Drake Equation, and the Fermi Paradox causes all sorts of ideas as to why we don’t see aliens.

The paper I alluded to above by Sandberg, Drexler, and Ord, called “Dissolving the Fermi Paradox” takes a survey of all the numbers used for estimates of the Drake Equation and instead of picking one, gives a range of probable answers and sees how likely it is statistically that we are in a universe with alien life.  The name of the paper comes from the fact that the Fermi Paradox goes away if we find out its probably that there to be no life besides us in the universe.  After looking at a variety of options they come to this conclusion:

We have seen that a Fermi paradox arises if we combine a high and extremely confident prior for the number of civilizations in our galaxy with the absence of evidence for their existence. The high confidence that causes this clash typically results from applying a Drake-like model using point estimates for the parameters. These estimates, however, make implicit knowledge claims about processes (especially those connected with the origin of life) which are untenable given the current state of scientific knowledge.
When we take account of realistic uncertainty, replacing point estimates by probability distributions that reflect current scientific understanding, we find no reason to be highly confident that the galaxy (or observable universe) contains other civilizations, and thus no longer find our observations in conflict with our prior probabilities. We found qualitatively similar results through two different methods: using the authors’ assessments of current scientific knowledge bearing
on key parameters, and using the divergent estimates of these parameters in the astrobiology literature as a proxy for current scientific uncertainty.
When we update this prior in light of the Fermi observation, we find a
substantial probability that we are alone in our galaxy, and perhaps
even in our observable universe (53%–99.6% and 39%–85% respectively). ’Where are they?’ — probably extremely far away, and quite possibly beyond the cosmological horizon and forever unreachable.
So by taking a look at the current state of affairs, they find it plausible that there is no life outside of Earth in the universe.  The numbers are even worse for intelligent life with it being very likely there is no intelligent life to be found else we would have encountered it already.  Thus it is a scientifically tenable conclusion that we are completely alone.
So why does this discussion make a good apologetic for Christians? After all, even if aliens were discovered it would not trouble the Christian.  Christians have historically had many interesting discussions on the topic of aliens as it makes for an interesting theological case study and the Scriptures are silent on the topic.  So regardless if the universe is teeming with life or constrained to just the Earth Christians have no problem.  Rather the results above pose a problem for the atheist.  The numbers here are damning and indicate that it is unlikely for life to arise by random chance. Observationally we can say fairly certainly that intelligent space-faring aliens do not exist else we would have seen them by now.
Even worse as we get better data for the variables in the Drake Equation (see the growing statistics on exoplanets and the emerging field of astrobiology) we may find that the Drake Equation would predict less than one civilization in the whole cosmos.  This would be an even worse paradox than the Fermi Paradox.  After all, we know for a fact that there is at least one intelligent civilization in the whole cosmos, our own.  If the Drake Equation were to predict less than one then we should not exist, yet we do.  This leads to a crisis as either we are the biggest statistical anomaly ever, or we are missing something.
As Christians we know the answer to this second apparent paradox, God created us and the whole cosmos. He is the explanation for why there is something rather than nothing.  We know who He is because He tells us about Himself in His Word by His Son Jesus Christ.  We do not need science to show us that there must be a God, we know there is one because He has told us so Himself.
All of this provides another argument in the back pocket of Christians against atheists.  This paper illustrates that there is a good chance that we are alone, even worse that we shouldn’t exist at all.  As Christians, we should pay close attention to these discussions as they continue to show the necessity of God as Creator and can be used to break down barriers to the Gospel.  That said we should be careful not to put to much weight on these numbers as they are still in flux, rather our foundation should always be on the Word and Christ’s Resurrection.  Nonetheless, it will be fascinating to see where research into both the Fermi Paradox and the Drake Equation goes in the future at it seems to be pointing to the inescapable conclusion that there is a God.

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