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We’ve all watched television shows and movies with space aliens in them. You’ve heard about the Drake equation on the Big Bang Theory, which can be used to estimate the likelihood of concurrent civilizations if we had data, but what exactly is it? Dr. Frank Drake, the first program manager for the SETI project proposed the equation in 1960 at the inaugural SETI conference. His equation has since undergone some changes, but the basics are left in place. He and subsequent astronomers suggested that the answer lay in a series of factors that were as yet unknown, including the rate of star formation; likelihood of stars having planets; and the fraction of planets where life occurs, is intelligent, has developed technology, and wants to communicate.

Can we solve this age-old question first asked by Dr. Drake? The lack of data has also made it difficult to answer the question posed by Dr. Enrico Fermi: “How many alien worlds like ours are out there?”  This absence of data has impeded progress on finding an answer, although many experts have weighed in with answers ranging from a few dozen to millions.  

These were the questions pondered more than 10 years ago by Dr. Frederick Bloetscher, associate dean for Undergraduate Studies and Community Engagement and professor at the FAU College of Engineering and Computer Science Professor. Due to the shortage of data, Dr. Bloetscher created a probabilistic solution for the number of concurrent civilizations, using statistical techniques that can use limited or subjective data. His solution involves predictive Bayesian statistics, which uses limited data and probability distributions to create answers in probability terms. The methods expand on work he did for his PhD and are useful because added data improves the answers directly. The solution he developed expands the current unknown variables to 10, including variables for star type, planet size, moons, and distance from the star that replace the number of planets variable. The results of the research were published in February 2019 in the respected British astronomical journal Asta Astronautica (Volume 155, February 2019, Pages 118-130, Using predictive Bayesian Monte Carlo- Markov Chain methods to provide a probabilistic solution for the Drake equation).  

“The idea came out of modeling risk for injection wells,” Dr. Bloetscher said. “Not much was known about some of those variables either, and there are many of them. For injection wells we can create probability distributions for those variables. So, I wondered, why not for the parameters of the Drake equation parameters?” 

Dr. Bloetscher notes that he has spent over 10 years off and on thinking about how to create distributions where there was basically little or no data. “It helped when Kepler started finding planets around other stars,” he said. “In addition, since certain types of stars were more likely to have planets, and we knew something about where planets would have to exist to have water, the concept for the probability distributions started to develop.”

So, what is the answer? “I did not create an exact answer because we simply have so little data,” Dr. Bloetscher said. “However, what data we have or can infer today seems to indicate that there is over a 50% chance we are alone in the galaxy. The likelihood we can find anyone is small due to distance. The variables affecting the answer the most were star formation and life expectancy of civilization.”  

That creates two challenges. First, although the possibility of finding other civilizations is unlikely, scientists should not give up the search. There are only 100 or so stars within 100 lightyears of Earth. If any of them had a civilization, they might not have signal yet, nor would they have been able to respond. Second, they are unlikely to be easily to colonize, making what we do on Earth critical to our survival. Therefore, it is incumbent upon scientists to continue to conduct research in this area, so that one day we will have enough data to fully answer the question.