The Personal Website of Mark W. Dawson

Containing His Articles, Observations, Thoughts, Meanderings,
and some would say Wisdom (and some would say not).

Intelligent Life in the Universe

We all thrill to the sci-fi movies, books and stories of humans communicating and/or meeting extraterrestrial civilizations. The mutual benefits (and quite possibly the mutual problems) of such contact would be interesting and challenging. Therefore, the question is "Is there Intelligent Life Out There?"

The Drake Equation postulates many Earth-like extra-solar planets that could support intelligent life forms. The Drake equation is a probabilistic argument used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy.

The Drake Equation was written in 1961 by Frank Drake, not for purposes of quantifying the number of civilizations, but as a way to stimulate scientific dialogue at the first scientific meeting on the search for extraterrestrial intelligence (SETI). The equation summarizes the main concepts which scientists must contemplate when considering the question of other radio-communicative life. It is more properly thought of as an approximation rather than as a serious attempt to determine a precise number.

As many skeptics have pointed out, the Drake equation can give a very wide range of values, depending on the assumptions, and the values used in portions of the Drake equation are not well established. Indeed, the assumptions themselves are highly conjectural and insufficiently defined that the combined effect is that the uncertainty associated with any derived value is so large that the equation cannot be used to draw firm conclusions. The main difficulties are “what are the factors and probabilities of the individual events occurring in each variable of the equation that determines the value to be utilized?”.

However, modern science has shown that the criteria for the development of a planet suitable for advanced life to form are more restrictive than the original Drake equation. The more criteria you inject into this equation the less likely a planet suitable for life to form. These additional criteria have brought the possible number of life capable planets to several orders of magnitude less than originally postulated. In fact, some have speculated that the number of life capable planets in our Milky Way galaxy may only be in the several thousand to hundreds of thousands. This is a small number considering that modern estimates of the number of stars in our galaxy are approximately 100 to 400 billion stars. While the number of possibly habitable planets is controversial (some claim that it is in the tens of millions or more) there is no consensus among knowledgeable scientists. You must also keep in mind that while we are discovering many earth-like planets orbiting other stars it takes much more than being earth-like for life to form. The criteria for an Earth-like planet to be able to form and sustain life are also constrictive to the number of life capable planets, and these criteria are subject to much scientific debate.

This is in stark contrast to "Rare Earth: Why Complex Life Is Uncommon in the Universe" is a 2000 popular science book about xenobiology by Peter Ward, a geologist and evolutionary biologist, and Donald E. Brownlee, a cosmologist, and astrobiologist, both faculty members at the University of Washington. The book is the origin of the term 'Rare Earth Hypothesis' which, like the book, asserts the concept that complex life is rare in the universe. The book argues that the universe is fundamentally hostile to complex life and that while microbial life may be common in the universe, complex intelligent life (like the evolution of biological complexity from simple life on Earth) required an exceptionally unlikely set of circumstances, and therefore complex life is likely to be extremely rare. The main lines of reasoning of Ward & Brownlee for a Rare Earth are:

1. The first step is the creation of a Planetary System around a star which originates in the right type of Galaxy (most likely a spiral galaxy), the right galactic location (not too close to or too far from the galactic nucleus which determine Cosmic ray and Cosmic dust impacts on life), and with the proper stellar classification that would allow life to form (basically, a not too hot or not too cold Main Sequence star).
2. Then, a Gaseous Nebula in this proper galactic location with sufficient mass to collapse into a star with sufficient heavy elements requisite for terrestrial planetary formation. In addition, this collapse should result in a single star creation, as there is some doubt that life could form and evolve in a binary or multiple-star
3. A star created from a gaseous nebula cloud, which contains molecular chains that are needed to seed the terrestrial planet with proto-life by means of meteoric or cometary impacts.
4. A Planetary System with the right arrangement of planets in the planetary system (i.e., the terrestrial planets close in and gas giants further out from the star). Any other arrangement would destabilize the orbit of a terrestrial planet and negatively impact life creation and evolution.
5. A terrestrial planet of the right size, mass, and gravity in a Habitable (Goldilocks) Zone, in a stable orbit around the star. This habitable zone is neither too hot nor too cold, allows for liquid water, and for the possibility of life as we know it.
6. A proper planetary orbit around the Star and the proper rotation of the Planet, which controls the temperature and the seasons of a planet, which are essential to the creation and evolution of life.
   • A terrestrial planet with an elliptical eccentricity that does not bring it too close (Perihelion) nor too far (Aphelion) within the Goldilocks Zone from its star.
   • A terrestrial planet with the proper rotational axis and diurnal period.
7. A terrestrial planet with a magnetosphere to deflect extraterrestrial radiation.
8. A terrestrial planet with the proper atmosphere conducive to life, i.e., sufficient nitrogen and not too much or too little oxygen or carbon dioxide, and only trace amounts of other gases.
9. A terrestrial planet where the asteroid and meteor bombardment does not massively evaporate surface water or destroy the life that was created on the planet.
10. A terrestrial planet with large quantities of surface water to expedite life creation and evolution.
11. A terrestrial planet with insufficient geological or meteorological forces that would result in the evaporation of surface water or pollution of the atmosphere, which would be destructive to life.
12. A terrestrial planet with a large moon that exerts tidal forces on the water and mantle of the planet, which allows for the molecular chains to slosh around and contact, then combine with each other.
13. A terrestrial planet with Continents and Plate tectonics for geothermal energy and heavy elements to be released from the core of the planet.
14. One or more (unknown) evolutionary triggers for microbial and complex life to form in water.
15. A complex life form that migrates from water to land masses to evolve into multiple plant and animal life forms.
16. A complex animal life that evolves with dexterous fingers and opposing thumbs to manipulate objects.
17. The further evolution of this dexterous-fingered and opposable thumbs species to a bipedal species with dexterous toes for bipedal balance control.
18. The further evolution of this bipedal species with enhanced multiple sensory systems that are not predominated by one sensory system, and whose field of senses is not constrained to their immediate vicinity.
19. The loss of fear of fire and the gaining of control over fire.
20. The rise of food cooking.

The Rare Earth hypothesis argues that the origin of life and the evolution of biological complexity such as sexually reproducing, multicellular organisms on Earth (and, subsequently, human intelligence) required an improbable combination of astrophysical and geological events and circumstances. Ward & Brownlee proposed a Rare Earth Equation to define these probabilities.

So, what are these equations?

The Drake Equation: where: N = the number of civilizations in our galaxy with which communication might be possible (i.e. which are on our current past light cone); R* = the average rate of star formation in our galaxy fp = the fraction of those stars that have planets ne = the average number of planets that can potentially support life per star that has planets fl = the fraction of planets that could support life that actually develops life at some point fi = the fraction of planets with life that actually go on to develop intelligent life (civilizations) fc = the fraction of civilizations that develop a technology that releases detectable signs of their existence into space L = the length of time for which such civilizations release detectable signals into space

The Rare Earth Equation: where : N* = stars in Milky Way, ng = stars in Galactic habitable zone, ne = planets in star's habitable zone, fp = fraction of stars with planets, fpm = fraction of metal-rich planets, fi = fraction of habitable planets where life arises, fc = fraction of planets with life where complex life (eukaryotic-type cells) arises, fl = percentage of a lifetime of a planet that is marked by the presence of complex life, fm = fraction of planets with large Moon, fj = fraction of planetary systems with Jupiter-sized planets, fme = fraction of planets with critically low mass-extinction events

The problem with both of these equations is that the correct numbers for the factors are unknown, and perhaps unknowable. The Drake Equation can predict up to approximately 15 million inhabitable planets, while the Rare Earth equation can predict between one and a few thousand inhabitable planets.

The Drake equation can be modified to determine just how unlikely intelligent life must be, to give the result that Earth has the only intelligent life that has ever arisen, either in our galaxy or the universe as a whole. This simplifies the calculation by removing lifetime and communication constraints. Since star and planets counts are known, this leaves the only unknown as the odds that a habitable planet ever develops intelligent life. For Earth to have the only civilization that has ever occurred in the universe, then the odds of any habitable planet ever developing such a civilization must be less than 2.5×10-24. Similarly, for Earth to host the only civilization in our galaxy for all time, the odds of a habitable zone planet ever hosting intelligent life must be less than 1.7×10-11 (about 1 in 60 billion). The figure for the universe implies that it is highly unlikely that Earth hosts the only intelligent life that has ever occurred. The figure for our galaxy suggests that other civilizations may have occurred or will likely occur in our galaxy.

In the Rare Earth hypothesis as any term in the equation approaches zero, so does the final result. The problems with the Rare Earth hypothesis are proving that these events are required for complex life to evolve, and then what are the probabilities of their occurrence?

The Rare Earth equation, unlike the Drake equation, does not factor the probability that complex life evolves into intelligent life that discovers technology (Ward and Brownlee are not evolutionary biologists). Barrow and Tipler (cosmologists) review the consensus among such biologists that the evolutionary path from primitive Cambrian chordates, e.g., Pikaia to Homo sapiens, was a highly improbable event. For example, the large brains of humans have marked adaptive disadvantages, requiring as they do an expensive metabolism, a long gestation period, and a childhood lasting more than 25% of the average total life span. Other improbable features of humans include:

• Being one of a handful of extant bipedal land (non-avian) vertebrate. Combined with unusual eye-hand coordination, this permits dextrous manipulations of the physical environment with the hands.
• A visual apparatus that allows for three-dimension perception and color recognition.
• A vocal apparatus far more expressive that of any other mammal, enabling speech. Speech makes it possible for humans to interact cooperatively, to share knowledge, and to acquire a culture.

These items, in combination with each other, required a larger brain to process this information. This allowed for the capability of formulating abstractions to a large degree permitting the invention of mathematics, and the discovery of science and technology. Only recently did humans acquire anything like their current scientific and technological sophistication.

Dr. Marc J. Defant is a professor of geology/geochemistry at the University of South Florida. Dr. Defant believes that the emergence and evolution of humans was a series of fortuitous events. He does so in a rational, logical, and scientific basis. His fortuitous events are:

• A nearby Supernova that seeded our Solar Nebula with the heavy elements requisite for life, and that started the collapse of the Solar Nebula that resulted in our Solar system.
• The size of the Meteor that struck the Earth at the end of the era of the dinosaurs about sixty-five million years ago, which allowed mammalian life to become dominant on Earth. If the meteor was any larger than it may have wiped out all but microbial life, and if was smaller it may not have completely wiped out the dinosaurs allowing them to once again dominate Earth.
• Of all the primates on Earth, only one primate species became intelligent. He believes that this was due to the East African Rift zone, which started expanding about ten million years ago. This rift deforested an area of Africa, home to large primates, and forced the primates out of the trees to become bipedal. This bipedalism accelerated the development of a larger brain which led to intelligence.

Given the low probability of these events occurring, and in the proper sequence, he believes that the development of intelligent life has a low probability.

Given all of the above, the number of planets capable of supporting advanced life in our galaxy may be very small. This constrictive number of advanced life capable planets may be why SETI has not discovered any evidence of intelligent life after several decades of searching for it. At the same time you need to consider that an Apocalyptic Event could have wipe out life or a civilization on another planet, as I have written in my science article on “Apocalyptic Events”.

Another question is not the number of extraterrestrial civilizations, but the number of extraterrestrial civilizations in their current state of evolutionary and technological development that would have a mutual interest in communications. If you think about where human civilization was at the beginning of the 20th century, versus where we are at the beginning of the 21st century, we would probably have little interest in communicating with an early 20th-century civilization, and probably no interest in communicating with a pre-20th-century civilization. After all, they had no radio or television, no air or space flight, automobiles were newfangled and scarce, electrification and the utilization of fossil fuels was just beginning, industrialization was just starting, and labor was a crude and brute force process. And where will we be at the end of the 21st century? Anyone living today would probably not recognize our civilization at the end of the 21st century. 

You must always keep in mind Arthur C. Clarke's Laws of Scientific and Technological advancement:

• When a distinguished but elderly scientist states that something is possible, he is almost certainly right. When he states that something is impossible, he is very probably wrong.
• The only way to discover the limits of the possible is to go beyond them into the impossible.
• Any sufficiently advanced technology is indistinguishable from magic.

It is most likely that mutual communication between extraterrestrial civilizations would only occur within a one-hundred-year period (+ or - 50 years of one of the extraterrestrial civilizations would be required). It has been pointed out that if the evolution of our solar system was a clock the evolution of intelligent life occupied only the last second of that clock. And other planetary systems have their own clock with different starting points and time scales than our clock. Given the immensely long time for intelligent life to evolve (millions of years) and the (relatively) small time for scientific and technological advancement (thousands of years), it is unlikely that two extraterrestrial civilizations exist within that 100-year time frame. This may be another reason why SETI has not discovered any evidence of intelligent life after several decades of searching for it. Also, given the immense distances between stars and the limitations of the speed of light, such communications may take several decades to travel between the two stars. A two-way conversation between extraterrestrial intelligent life would therefore be almost impossible to maintain and may even be impossible to understand. Translating from one human language to another is fraught with problems, as anyone who has learned to read, write, and speak a second language is aware. Even when the languages are similar, there is a multitude of problems. When learning dissimilar languages, i.e., English and Mandarin, the problems are of a greater magnitude. It is possible for humans to do this, as we are all human and have many commonalities that assist us in this translation. Now imagine trying to learn an alien language in which there are few commonalities.

As to traveling to meet these extraterrestrial civilizations the immense distances are also prohibitive. Given the energy required, as well as the technical and ecological factors required to make the trip, would also be extremely difficult. Even the sci-fi speculation of such things as warp drive, wormholes, subspace, and other exotic means of transportation would be an immense scientific and technological feat and could put us out of that 100-year time frame. And we must also keep in mind the problems of Einstein's Special Theory of Relativity when making this trip. These costs and difficulties are more fully explained in my article "Science vs. Science-Fiction" and I would encourage you to read this article.

Given the above, I believe that extraterrestrial civilizations are a possibility, but are not probable. If there are extraterrestrial civilizations it may be impossible of us ever communicating with them, let alone visit them, or even that they could exist in the same 100-year time frame.

You should also be careful of wanting to meet extraterrestrial civilizations. Human history has many sad examples of when a more advanced society meeting a less advanced society. It has often been the case that the less advanced society suffers tremendously, if not being obliterated.   

As can be seen from the debate over Complex vs. Rare Earths the science is very open to different assumptions that can produce different results. This is because so much of the data is ill-defined or unknown to modern science.

You should also remember what a famous science fiction writer once said about Intelligent Life in the Universe:

“Sometimes I think we're alone in the universe, and sometimes I think we're not. In either case, the idea is quite staggering.” - Arthur C. Clarke

* * * * *

Note 1 - the book "Rare Earth: Why Complex Life Is Uncommon in the Universe" does not examine the issue of God or an Intelligent Designer. It has, however, been appropriated by those who believe this as a supporting case for their beliefs. This is a shame as the book does none of these things but is only a serious scientific examination of the probabilities of a Complex versus Rare Earth hypothesis.

Note 2 - Dr. Defant fortuitous events do not account for the timing of the meteor strike. If the strike had occurred and few minutes before or after it it actually occurred it would have struck deeper waters, rather than the land/water impact that occurred, and its catastrophic impacts would have been significantly different. Significant enough to have change the evolutionary history of life on Earth.

Note 3 – Many of the sentences and a few paragraphs were extracted from the Wikipedia articles that I have hyperlinked in this article.

Note 4 - An interesting TEDx Talk “Why We are Alone in the Galaxy” by Marc Defant raises some of these questions of Intelligent Life in our galaxy.

Note 4 – My own opinion is that the Rare Earth argument is more likely to be correct than the Drake argument. But as I am not a scientist, I cannot make a scientific judgment.

Disclaimer

Please note that my Science Articles disclaimer applies to this article, as it does to all of my science articles. These science articles are for the purposes of general scientific information that is understandable to a layperson, so that they can grasp the concepts of the topic being discussed. As such, they are neither as accurate nor as thorough as academics, scientists, engineers, and science writers strive to achieve. My hope is that these science articles will be informative and interesting, and that they will pique the reader's interest in exploring these topics in further detail via the hyperlinks that I have embedded into these articles.