Drake vs. Fermi: Skepticism and SETI

April 12, 2016

Most scientists are quite skeptical about the “UFO” phenomenon, and yet supportive of valid scientific efforts like SETI - the Search for Extraterrestrial Intelligence, which has been going on now for decades without finding proof of any extraterrestrial communications. Are skepticism and SETI still compatible, and at what point, if any, would SETI become pseudo-science?

              CFI and other skeptical organizations have spent a lot of time debunking UFO reports, and yet most of us who are skeptics are rather hopeful we will find evidence of intelligent life beyond our solar system at some point. These two positions are perfectly compatible given the science involved, and the laws of nature that stand in the way of traversing the stars, even for very advanced civilizations should they exist. As Douglas Adams famously penned in his book The Hitchhiker’s Guide to the Galaxy “Space is big. Really big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space.” It is the size of the universe that simultaneously make it unlikely that we are alone, and unlikely that we have or will ever be visited by other intelligent life-forms.

              Most of us have heard of the famous Drake equation, which is meant to help calculate the number of intelligent, communicating species in the universe. You can plug in some numbers yourself using the BBC’s Drake Equation Calculator. The most conservative values plugged into this calculator give a total of 1 intelligent and communicating species in our galaxy (presumably, us), and a total of 78 billion in the entire universe. The most optimistic numbers increase the number of such species in our galaxy to about 72,000. So, depending upon your level of optimism, there are between 1 and 72,000 intelligent, communicating species currently in our galaxy, and between 78 and 11,000,000 billion in the entire universe. Let’s forget the rest of the universe for now, because the vast distances involved and the likelihood of communications from that far away reaching us intact make it a wasted effort to look there, and let’s focus on our galaxy. Our Galaxy is one of hundreds of billions in the universe, and itself has between 300 and 400 billion stars. It is about 100,000 light years wide and about 10,000 “thick”.

              The “Fermi Paradox,” raised by Italian physicist Enrico Fermi, asks why, given the relatively high probability of the existence of intelligent life elsewhere in the universe, haven’t we heard from them? It’s a fair question, and might suggest to skeptics that we are indeed alone. There have been numerous attempts to answer this apparent paradox, including some that extrapolate from our unlikely survival here on Earth. Consider, for instance, that the universe is quite hazardous. Supernovae, gamma bursts, asteroids, and any number of natural phenomena may wipe out a species at any time. There is evidence of such mass extinctions here on our own planet and no reason to think it cannot happen again. Moreover, as an “intelligent” species, we may now be our own worst enemy, whether by nuclear Armageddon or cataclysmic climate change. The same pattern may exist for any evolving intelligent species, making the window for communications quite small.

              As a radio-communicating species, our presence would so far only be known to other radio-listening species within a 100 light year radius of us. There are about 500 stars within that radius, and so far, listening to them, we have heard nothing, although we have observed nearly 100 planets in that vicinity. There is a whole, huge galaxy we inhabit, full of stars we cannot even see given our current technology, and doubtless billions of planets, some of which exist in so-called habitable zones. But finding communications from other intelligent life that evolved in our galaxy depends greatly on chance - did they transmit in a way that we can detect, at such a time that their signals are now reaching us? Meanwhile, travel at speeds faster than light to actually visit other star systems remains physically impossible, short of exotic technologies and as-yet only theorized states of matter that may or may not exist. A new approach to the search for life beyond Earth, devised by Prof. Sara Seager of MIT, can help us to focus our search, and proposes not to look for signals from intelligent species, which as discussed above is much worse than looking for a needle in a haystack, but rather to look for bio-signature gases on detectable exoplanets.

              To the question of whether we are alone in the universe, given the sheer numbers involved (time, distance, and habitable planets estimated) a skeptic would likely answer “no, it is highly unlikely.” But as to whether nearby habitable planets within listening distance, or even in our galaxy, have intelligent life at the same level of technology so that we can hear them, the answer is also “no, it is highly unlikely.” SETI should continue to refine its methods for finding such signals, acknowledging that the chances of our detecting another civilization remotely are negligible, even while the scientific value of finding them would be huge. The math suggests it is possible, and as long as we can affordably listen in and hone our listening to the most likely candidates, then it remains a valid scientific endeavor worth the costs. Meanwhile, Prof. Seager’s equation gives us guidance for another, equally important search: the search for exo-biology – life beyond our planet. NASA continues to look for signs of life in our solar system, where we may still discover that it exists in places like Europa, where liquid water may exist, or we may yet discover that it once existed in now desolate Mars (where evidence of liquid water may have recently been found).

              SETI and skepticism are still compatible. The numbers involved suggest we should keep listening if we can keep the costs affordable, and new planet-detecting technologies, combined with refinements in the manners for which we search the galaxy for life may put us within a decade of detecting its traces, if not in our solar system, then nearby. Meanwhile, the very same science that shows us the vastness of the universe almost certainly harbors intelligent life, suggests they are almost certainly not visiting us, nor have then, nor will they. Which is fine with me, frankly, if they’re anything like us.


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