Man has always gazed at the stars and attempted to answer the question about the existence of any life anywhere else in the Universe apart from Earth. While for the better part of the first two thousand years After Christ, there was a popular assumption that Man is unique in the Universe, the acceptance of the ‘Copernican Principle’ (Tyson, 2003) in the 1500s, when Nicholas Copernicus put the sun back in its proper place at the center of the solar system, propelled the notion that man may not be unique after all. Given the fact that the three most common elements on Earth- Hydrogen, Oxygen and Carbon- are also the most common elements in the Universe, popular imagination took wings, expecting extraterrestrial life to be discovered sooner rather than later with the advances in science and technology.
Over the last fifty years, however, technology has only flattered to deceive. Countless ‘proofs’ of extraterrestrial life have been discovered, only to be debunked later with explanations based on scientific observation. A purported UFO crash at Rosewell, a New Mexican town, turned out to be a weather balloon from a secret spy program (Space, 2006). Many people who reported abductions by aliens have been later found to have suffered from hallucinations caused as negative side effects of psychotherapy. Similarly, the unexplained crop circles in rural English and American farms are likely to be the result of elaborate hoaxes (Space, 2006).
Nevertheless, new and unexplained occurrences and purported evidences keep emerging, arguing for the presence of extraterrestrial life and ensuring that the question lingers on. At the forefront of the search for extraterrestrial life is NASA, and hundreds of scientists around the world looking for radio signals from outer space. NASA has discovered more than 5,000 planets so far, and ‘expects to find alien life in the coming decades’ (Snelling, 2014). To aid its search, NASA plans launching powerful telescopes and extends its partnership with international space endeavors.
Those who have continuously debunked claims of the existence of aliens with scientific proofs, however, are fast reaching a conclusion that NASA’s efforts would yield little. In effect, the world finds itself in two camps- one, arguing that extraterrestrial life exists and another, which claims that it is not plausible. This paper would attempt to assess both sides of the coin, and make an assessment of the relative merits of each.
Perhaps the biggest impetus that was provided in the bid to search for extraterrestrial life came not from any real sighting but from the articulation of the mathematical probability of such a sighting. Following a 1959 assertion by physicists Giuseppe Cocconi and Philip Morrison that radio telescopes had become sufficiently powerful to pick up transmissions from civilizations residing elsewhere in the Universe, radio astronomer Frank Drake took it upon himself to search for intelligent life in the cosmos by monitoring a 25 meter dish at the National Radio Astronomy observatory in Virginia. Though Drake did not encounter success, he then sponsored a meeting in 1961 with the agenda of searching for extraterrestrial intelligence. The famous Drake equation is the result of that meeting (Foothill College, n.d.). The Drake Equation is as under: -
“N = R* . fp . ne . fl . fi . fc . L” (Foothill College, n.d.), where
N = the number of civilizations in our galaxy with whom we might be able to communicate (Foothill College, n.d.).
R* = the average number of star formations per year in our galaxy (Foothill College, n.d.).
fp = the fraction of those stars that have planets (Foothill College, n.d.).
ne = the average number of planets that can potentially support life per star that has planets (Foothill College, n.d.).
fi = the fraction of planets with life that actually go on to develop intelligent life (Foothill College, n.d.).
fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence in space” (Foothill College, n.d.).
L = the length of time for which such civilizations release detectable signals in space.” (Foothill College, n.d.).
The original estimates by Drake and his colleagues were that there is one star being formed per year at an average, that between one fifth and half of all stars have planets, that stars with planets would have between one and five planets capable of developing life, that all these planets would eventually develop intelligent life, that around 10-20% of these planets would be able to communicate, and that such communication would last for anything between 1000 and a 100 million years. Given these estimates, Drake came to the conclusion that there were probably between 1000 and 100 million civilizations in the Milky Way Galaxy (Foothill College, n.d.).
Over a period of time, scientists have proposed a number of amendments to the original estimates of Drake. The most optimistic estimates, taking the higher values of each factor, resulted in arriving at a figure of N = 36.4 million, providing popular motivation and some funding for SETI (Search for Extraterrestrial Intelligence) research. The key goal of SETI, a non-profit organization, is to progress research that would yield additional information related to any of the factors of the Drake equation.
With continued advances in technology, the factors of the Drake equation are continually getting evolved. Latest calculations from NASA indicate that R*, the rate of star creation in our galaxy is about seven per year (Foothill College, n.d.). Microlensing surveys have recently found that fp, the fraction of those stars having planets may well be 1, as stars invariably have planets. While many of these planets are too close to the stars, scientists have discovered many planetary systems akin to solar systems, such as “ HD 70642, HD 154345, Gilese 849 and Gilese 581” (Foothill College, n.d.). Geological evidence from Earth suggests that the fraction of such planetary systems that could actually go on to develop life could be very close to 100%. Out of such planets, the fraction that develops intelligent life is open to conjecture. Votaries for extraterrestrial life note that life, once it takes root, eventually becomes progressively complex, and that the eventual appearance of intelligence is almost axiomatic (Foothill College, n.d.). The aspect of what fraction of intelligent civilizations would release detectable signs of their existence into space has become relatively irrelevant, as it is observed that current signatures of civilization on Earth are readily detectable from outer space. The final factor, the expected lifetime of such civilizations, is again open to conjecture. It is often argued that once life forms like humankind reach a certain level of sophistication, they could theoretically continue to survive for all time unless doomed by their own indiscretions like climate change and nuclear war (Foothill College, n.d.). Recent attempts at arriving at more realistic estimates for the Drake equation have led to consensus around establishing a lower bound in the probability of finding intelligent life in the galaxy (Frank & Sullivan, 2016). Such a lower bound becomes a basis of optimism that man would eventually be able to discover extraterrestrial life.
The Drake Equation, thus, provides a framework for an estimate of how many intelligent civilizations exist in our galaxy. While the equation does not provide proof of extra terrestrial life, the components of the equation spur scientists to arrive at increasingly accurate estimates, narrowing down the likely numbers of intelligent civilizations in the galaxy. The charm of the Drake equation, therefore, is not in the proof, but in the promise that there are likely to be hundreds and even thousands of intelligent civilizations in the galaxy. It is this promise that propels mankind’s push to reach out and find such life forms.
Fermi Paradox, Rare Earth Hypothesis & Rare Earth Equation
At the opposite end of the spectrum, arguing against the possibility of intelligent life in the galaxy apart from mankind on earth is the Fermi Paradox. The basic foundation of the Fermi Paradox is simply the lack of extraterrestrial contact. The pessimist argument is that if there indeed were any civilization in the galaxy that existed for tens of millions of years, it could have had plenty of time to travel anywhere in the galaxy. Further, there have been no confirmed signs of intelligence anywhere in our galaxy or in any of the galaxies in the universe. Given the universal trait of living things to occupy all possible territory, the pessimists argue that the Earth should by now have been colonized or visited by species representing extraterrestrial intelligence. However, there is a singular lack of evidence of such contact. This propelled Fermi to ask, ‘Where is everybody?” (Foothill College, n.d.).
The Fermi Paradox chooses to justify itself through a number of options. One option is that there are few intelligent civilizations that ever arise. This argument is based on hypothesizing that at least one of the terms in the Drake Equation would necessarily be of an infinitesimally low value. The value of fi, the fraction of habitable planets that go on to host intelligent life, is argued to be low by votaries of Fermi Paradox.
A corollary of the Fermi Paradox, the Rare Earth Hypothesis (Ward & Brownlee, 2003), argues that the small term in the Drake Equation is ne, the average number of planets that can potentially support life per star. The Rare Earth Hypothesis contends that while microscopic, sludge-like organisms could indeed be eventually found in other planetary systems, it would be very rare to find that such rudimentary life forms have evolved into higher order organisms, and such organisms have survived for long terms to become intelligent. The Rare Earth Hypothesis bases its conjecture on the very nature of evolution of the earth. While primitive forms of life existed on earth for most of its history, more complex organisms came about only in relatively recent years due to extremely fortuitous circumstances that could not be plausibly common to other planets. Therefore, as a repartee to the Drake Equation, Ward and Brownlee devised the Rare Earth Equation, which is:-
“N = N* . ne . fg . fpm . fi . fc . fl . fm . fj . fme, where
N= number of earth-like planets in the Milky Way (Ward & Brownlee, 2003).
N* = number of stars in the Milky Way (Ward & Brownlee, 2003).
ne = average number of stars in a star’s habitable zone. Ward and Brownlee contend that this figure is constrained by exacting requirements of planetary temperatures and the requirement of water to remain in liquid form (Ward & Brownlee, 2003).
The Rare Earth Hypothesis asserts that the combined multiple of all further factors in the equation is not more than 10-10.
fg = Fraction of stars in the galactic habitable zone. Ward and Brownlee estimate this figure to be 0.1 (Ward & Brownlee, 2003).
fpm = fraction of planets that are rocky rather than gaseous (Ward & Brownlee, 2003).
fi = Fraction of planets where microbial life exists. This is expected to be a high proportion (Ward & Brownlee, 2003).
fc = Fraction of planets where complex life evolves. Ward and Brownlee argue that this figure would be exceedingly small (Ward & Brownlee, 2003).
fl = Fraction of the total lifespan of a planet during which complex life is present (Ward & Brownlee, 2003).
fm = Fraction of habitable planets with a large moon. Ward and Brownlee contend that the moon has had a stabilizing influence on the earth’s rotation, and that it is unlikely that most habitable planets would have such large moons (Ward & Brownlee, 2003).
fj = Fraction of planets with large Jovian planets, which is expected to be large (Ward & Brownlee, 2003).
fme = Fraction of planets with a sufficiently low number of extinction events. Ward and Brownlee contend that the Earth is singularly lucky not to have faced cataclysmic extinction events after the Cambrian explosion when simple forms of life gave way to complex organisms” (Ward & Brownlee, 2003).
Thus, while the Fermi Paradox challenges the existence of extraterrestrial life by the contention that no such life has been observed, the Rare Earth Hypothesis argues that complex forms of intelligent life are not possible but for the extremely fortuitous circumstances mankind has found itself in.
We therefore have two ends of the spectrum as far as claims regarding the presence of extraterrestrial life are concerned. Agencies like NASA and SETI continue to search for life in the galaxy, propelled by modifications in the Drake Equation that set a lower boundary to the theoretical possibilities, effectively setting a lower limit that is higher than improbable. The Fermi Paradox and Rare Earth Hypothesis are content to await positive proof. Their argument about mankind being born in fortuitous circumstances can only be proven wrong when positive proof of some other form of extraterrestrial life is available. In effect, it is not for the votaries of the Fermi Paradox to provide evidence that no extraterrestrial life exists. So long as none is found, the Paradox and, in corollary, the Rare Earth Hypothesis, are intact.
While it is extremely difficult to write off either of the stances on extraterrestrial life, if a choice has to be made, one must side by the votaries of the Drake Equation and vouch for the possible existence of extraterrestrial life. The Rare Earth Hypothesis has, to its support, the contributory factors that made advanced forms of life possible on earth. However, it cannot be conclusively stated that such sets of factors in other combinations cannot exist elsewhere. The fact that the three elements most common in the Universe- Oxygen, Carbon and Helium – are what constitute 95% of life on earth goes to underline the fact that the basic building blocks for life definitely exist elsewhere in the galaxy. It is possible, for instance, that life exists elsewhere, but such life exists in faraway pockets, and different species of extraterrestrial life are separated by huge voids of nothingness. We are aware that the Universe is expanding. It may, therefore, be a possibility that the likelihood of radio transmissions being actually received from other extraterrestrial civilizations is actually receding, despite their existence.
While there has been no conclusive proof of extraterrestrial life, it may be premature to give up on the possibility. After all, it is only in the last century that mankind has developed the technological tools that would aid in the search for extraterrestrial life. While new technology in terms of radio telescopes and galactic rocket missions would ever expand the chances of finding extraterrestrial life, man would nevertheless need to keep the arguments of the Rare Earth Hypothesis in mind, and ensure that he does not self-destruct his natural environs through triggering climatic cataclysms or wars. Ultimately, it is for man to find his mirror in the Universe, while he continues to ensure that he is not the reason for his own downfall.
Foothill College. (n.d.). Drake equation. Retrieved May 7, 2016, from http://www.foothill.edu/attach/938/Drake_equation.pdf
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Snelling, D. (2014). Aliens are coming! NASA tells the world extraterrestrial life does exist on other planets. Retrieved May 7, 2016, from http://www.dailystar.co.uk/tech/news/389080/NASA-confirms-Extraterrestrial-life-DOES-exist-on-other-planets
Space. (2006). Ten alien encounters debunked. Retrieved May 7, 2016, from http://www.space.com/9704-ten-alien-encounters-debunked.html
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Ward, P.D., & Brownlee, D. (2003). Rare Earth: why complex life is uncommon in the universe. New York, NY: Copernicus.