Alien Life - What are the Odds?
For millennia, humans have wondered about life on other planets. As the quote above says, how can we close our minds off to the enormity of the Universe and the nearly infinite possibilities? It is likely that our ponderings on life on other planets goes back even farther than recorded history. Around 400 B.C., the Greek philosopher Metrodorus of Chios wrote, “it is unnatural in a large field to have only one shaft of wheat and in the infinite universe only one living world.”
Fermi Paradox & the SETI Program
Through the years, philosophers and scientists pondered upon this topic. With the dawning of the Nuclear Age, science grew and matured. In 1950, Italian physicist Enrico Fermi was having a lunch conversation with his co-workers. He noted the apparent contradiction between the lack of evidence of extraterrestrial civilizations and what he and other scientists of the era believed to be a high probability of life elsewhere, which has been termed the “Fermi Paradox.” By 1959, the foundational science of the Search for ExtraTerrestrial Intelligence (SETI) program had been established.
So, here we are over sixty years later, the SETI Institute conducts its science – one of its missions is to examine data collected by
radio and optical telescopes in the search for alien life. A search that through today, to public knowledge, has not provided any concrete results. Similarly, the theoretical speculation of extraterrestrial life continues.
Over the past month, two peer-reviewed studies were published – one by a Columbia University professor, the other by University of Nottingham (UK) faculty – examining the likelihood of intelligent life developing on other planets. This research and results will be highlighted in this two-part article for ExoConsulting.
Math can seem Alien
In the June 2, 2020 issue of the Proceedings of the National Academy of Sciences, Dr. David Kipping, an astronomy professor at Columbia University, put pencil to paper to calculate the probability of intelligent life developing elsewhere in our Universe. His math-intensive analysis used a Bayesian approach, which allows for the researcher to determine the likelihood of an event based of the probability of the individual events that would lead up to the final conclusions.
Kipping’s goal was to determine the likelihood of existence of intelligent life on another planet within the Universe. As noted in the Crossroads quote, there are possibly a googol of planets to consider; a googol is 1 with 100 zeroes after it. Despite the fact that we only have one point of reference, Kipping states that does not mean we lack the needed information. That data point is Earth, which has experienced at least one abiogenesis event, which is the instance when living organisms developed from inorganic material.
The first factor that Kipping considered was whether there was a slow or a fast start to life on Earth. In relative terms, it is believed that our abiogenesis event occurred fast. In actuality, Kipping states under the “slow start” scenario, it is unlikely intelligent life develops for the mere reason that there is not enough time for its evolution. While anyone can make this statement without proof or evidence, Kipping offers a thorough mathematical analysis, yielding numerical results.
When we consider fast vs slow scenarios, it is hard to avoid the broader topic of “time scales,” which are in terms of billions of years. To establish how long it takes something to occur, we need to determine when to start counting. This analysis looked at two “sterilizing” events: first, the collision of Earth with Theia, a Mars-sized object, which collided with Earth about 4.5 billion years ago.
Its remnants then came together to form the Moon. About 40 million years later, another event occurred after a collision with Moneta. Given all that, by about 4.4 billion years ago, the components needed for life - an atmosphere and water - were present.
Based on microfossil records, this analysis estimated that life first appeared between 300 million (optimistic value) and 940 million years (conservative value) after the collision with Moneta. In either case, both of these values are higher than the uncertainty value, 76 million years, Kipping had quoted in his research. By means of the objective Bayesian methodology, the analysis showed that an abiogenesis event occurring in the fast scenario was almost three times more likely through a slow process. This value increases to the fast scenario being nine times more likely, using the more optimistic value.
The investigation was then taken one step beyond: what are the odds that intelligent life develops? This was another case where he developed both fast and slow emergence of intelligence scenarios, in addition to the use of the optimistic and conservative “emergence of life” time frames, established through the microfossil records. His results suggested a slight preference, essentially 3:2 odds, that intelligent life would emerge, if life initially developed on a planet.
Conclusions
In summary, Kipping offered the analogy that if we reran the tape for Earth, it was more likely that life would emerge relatively quickly. However, if the amount of time required for the evolution of intelligent life was long, then the fast scenario is just a necessity and not proof of a more universal rapid abiogenesis rate. With regards to the likelihood of an intelligence emergence, a weak preference, 3:2 odds, was derived.
Combining Kipping’s results offers an optimistic outlook in our search for intelligent life elsewhere in the Universe. Applying the conservative scenario for the likelihood of fast emergence of life, 75%, along with likelihood of the development of intelligent life, 60%, yields an overall probability of 45%. Given these results, Earth was still a slight underdog. However, in a universe where there are countless planets, it does offer a positive outlook for the programs like SETI.
Written by Aaron Studwell, June 10, 2020
(Author’s note: A googol of planets is 10,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000,000, 000,000,000,000,000,000,000,000,000,000,000,000,000,000 planets.)
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