“There is every reason to believe that Mars and other planets are inhabited. Why should the earth be the only planet supporting human life? It is not singular in any other respect.” – Albert Einstein quoted in the Daily Mail, 1920
Well, the jury’s out on whether there is life on Mars. It’s still possible that “extremophiles,” — life forms that can exist under extreme pressure and temperature — are thriving on Mars and we just haven’t found any evidence yet. However, Einstein’s assertion that Earth is nothing special, with the implication that “Human” life should be common on other planets is something entirely different.
It is easy to conclude that, just based on sheer numbers, the universe is so large that surely there is at least one other place or more where there are (or were) human-like aliens doing the things we have been doing for thousands, if not millions, of years.
With at least 200 billion galaxies out there (and possibly even more), some believe the Universe is filled with around 1024 planets. For those of you who like it written out, that’s 10,000,000,000,000,000,000,000,000 planets in our observable Universe.
Right here in our own Milky Way galaxy, NASA estimates there are about 100 billion stars.
As to the number of planets that might be suitable to support life, the current estimate is about 8.8 billion. Again, a very large number.
Of course, raw numbers are not sufficient to make a reasonable estimate. And very high numbers of planets supposedly harboring human-like aliens leads to “Fermi’s paradox.” Named after physicist Enrico Fermi, the paradox says that there is an apparent contradiction between the lack of evidence and high probability estimates. That is, the evidence so far suggests that there are very few, if any, extraterrestrial beings, much less “intelligent” beings.
The desire to detect human-like aliens on other planets comes from the human perspective. This is the “anthropic principle,” which is the philosophical consideration that observations of the Universe must be compatible with the conscious and sapient life that observes it. In other words, we humans project ourselves onto the visible universe and describe our observations the only way we can — anthropically. Otherwise, we would be unable to apprehend what we see.
That said, a project called the Search for Extraterrestrial Intelligence (SETI) began in earnest around 1960. But the search was not for Extraterrestrial Intelligence per se, but for radio waves that presumably intelligent beings like us would send out into the ether.
The method used to make estimates of how many of these alien civilizations might be out there sending us radio signals is known as the Drake Equation. Back in 1961, physicist Frank Drake came up with this equation:
Where N is the number of planets with “intelligent” life. It is computed by multiplying estimates for the various factors that Drake thought would be sufficient to approximate N.
The factors are:
R — How fast stars form in our galaxy.
fp — The percentage of stars that have planets.
ne –The number of earthlike planets around each star that has planets.
fl — The percentage of earthlike planets that develop life.
fl — The percentage of planets with life that develop intelligent life.
fc — The percentage of intelligent species that create technology that could be detected by an outside civilization like radio signals.
L — The average number of years the advanced civilizations release detectable signals.
From there it is a matter of assigning values to each of the factors:
Obviously, the variances are rather extreme. But these estimates are way too far apart to be meaningful, especially when you consider deterministics other than those the good Dr. Drake came up with. And, after all, those are just SWAG estimates anyway. (SWAG = Scientific Wild Ass Guess.)
But Dr. Drake and his fellow cosmologists have another problem here and that is the difficulty of “reductionism” — a procedure or theory that reduces complex data and phenomena in simple terms. The Drake Equation uses only 7 factors. But given the complexity of life and the influences — physical, chemical, and biological — surely there must be many more factors to be considered and, if possible, quantified. Then, too, we should remember H. L. Mencken, who wrote, “For every complex problem there is an answer that is clear, simple, and wrong.”
Nonetheless, the SETI project relies on Drake’s equation to help justify and continue its decades-long operation. And it has many supporters.
On July 20, 2015, physicist Stephen Hawking and a Russian tycoon named Yuri Milner held a news conference in London to announce that they are injecting $100 million and a whole lot of brain power into the search for intelligent extraterrestrial life, an endeavor they’re calling “Breakthrough Listen.” “We believe that life arose spontaneously on Earth,” Hawking said at the news conference, “So in an infinite universe, there must be other occurrences of life.”
Yes, Dr Hawking, I agree with you that there is extraterrestrial life all over the universe. In fact I would go so far as to say that life exists on millions of planets right here in our own Milky Way galaxy. But such life forms are most likely of the single cell variety. Even if extraterrestrials did evolve much like life here on earth, they may have just stopped with their equivalent of our whales and elephants and ravens and octopuses, all of which are intelligent, and none of which transmit radio signals. How will we detect those smart critters?
Having said all that, I believe the search for extraterrestrial beings that use radio transmitters is useless. I would call it a fool’s errand, but those involved are far from being fools.
My approach to this enquiry is to expand the Drake Equation to fill in the blanks that link one step to the next. When dealing with the possibility that there is another civilization on some planet somewhere in the universe that has the capability of contacting us via radio signals, it is helpful to know the series and sequence of events needed to reach that level of intelligence. And since there is no model we can follow, we have to use the only one we know about; namely the human beings on planet earth!
Just getting a planet from its formation to its ability to harbor life requires a number of conditions and events. For example, following the earth’s evolution and conditions from its creation, any other planet able to support life should have like characteristics.
So, here we have 16 conditions that must be present before life can begin on any given planet. But that is only the beginning. In our Milky Way galaxy with it’s 100 billion planets, there might be 6.25 billion with all of those 16 factors (100 billion/16 = 6.25 billion. That’s a smaller estimate than the estimate of 8.8 billion mentioned above. In any case, I’ll use the 6.25 billion as the base line for the analysis here.
Once the conditions are right for life to form on a planet, there must be an evolution from microscopic single cell forms all the way up to human-like aliens. And since, again, the only model we have for this evolution is our own planet, it might be reasonable that life on another planet would follow a similar path. That is, life follows from its roots through various branches that ultimately evolve into earth-like beings with intelligence at least equal to we homo sapiens sapiens. That taxonomy might look something like this:
So, here we have 18 more factors to add to the 16 mentioned above. We must assume that the drivers of basic biological evolution — natural selection, mutated genes, adaptability and enough time — are present and part of the taxonomy of human-like aliens. And that process, in our case at least, ended some 200,000 years ago.
From that point in time, our would-be extraterrestrial beings must begin to use their brains . For them to be able to make radio transmitters, they must first make some discoveries and apply their evolving intelligence to establish culture and to produce inventions that enhance their survivability.
Along with these additional factors to crank into a Drake-like formula, we should also consider that, from the physical and biological changes over the planet’s life, there have been at least 25 extinction events with five major “near extinction” events, including:
1 The end of the Ordovician, 444 million years ago, 86% of species lost
2 The end of the Devonian, 375 million years ago, 75% of species lost
3 The end of the Permian, 251 million years ago, 96% of species lost
4 The end of the Triassic, 200 million years ago, 80% of species lost
5 The end of the Cretaceous, 66 million years ago, 76% of all species lost
And biologists today are telling us the we are well into the sixth extinction event given the number of species that have disappeared in the last 10.000 years.
In fact, we humans were involved in a potential extinction event some 74 thousand years ago when the Toba volcano erupted in Indonesia. It is estimated that the population of our species dropped to 10,000 as a result. It created what geneticists call a “bottleneck” in our genome. (For comparison, the explosive force of Toba was 2,500 times that of Mt. St Helen’s.)
At the end of the day (which may be longer or shorter on another planet), what we have here are four distinct sets of conditions for human-like aliens to reach the point where they could produce radio signals.
16 Conditions for Life to Exist on Another Planet
18 Steps in Evolution from Single Cell to Modern Human-like Aliens
18 Events Needed for Human-like Aliens to Transmit Radio Signals
5 Near extinction events
Of course, there are many other variables that are difficult to quantify, not to mention identify via telescope. These would be what we call the “Humanities.” They include literature, visual and performing arts, philosophy, religion, law, politics and a sense of morality.
Would any human-like aliens have Eastern and Western civilizations like us? Are there racial issues? Are there rich and the poor? And just how much do any of these humanities influence human-like aliens in their ascendancy through time to invent radios?
But besides the Humanities, changes in the intelligent extraterrestrials’ culture might also play a role in their intellect and their motivations. Were they active, for example, in sports, or games? Were they warlike? Did they have tribes, kingdoms or empires, or multiple civilizations? Did they own slaves, have different races, have political revolutions? Did they have a Plato, a Euclid, a Shakespeare, a Beethoven, a Michelangelo, a Newton, an Einstein, a Hitler?
All of these are factors to consider in understanding what would prompt a civilization to develop science and to promote an interest in communicating with other alien species.
Without attempting to quantify the various abstract humanities and cultural factors, we can make estimates based on the conditions set out above. From the first 16, we came up with 6.25 billion planets as a base. Then there are 16 conditions for the evolution of life needed for a human-like alien, and another 16 conditions involving inventions and discoveries that conclude with the ability to produce radio signals. It is the last two sets of factors — 36 in total — to be considered. And those 36 are in sequence — one follows the next in order.
The question then, is what are the odds that an alien civilization on another planet somewhere could have followed in our footsteps to reach the level of technology that would allow them to communicate with us via radio signals?
One way of determining this is to use something similar to the Drake Equation, except there are many more variables to consider. Since the 36 conditions listed above are more or less in sequence, the methodology would be something like calculating how many times it would take to shuffle a deck of 52 cards so as to repeat the first shuffle. The answer, according to the mathematicians is the factorial of 52, which is 8.06567 Written out, that’s 80,658,175,170,943,878,571,660,636,856,403,766,975,289,505,440,883,277,824,000,000,000,000
So, similar to the card shuffling example, determining the order of the 36 conditions for life to exist on another planet would be 36!, which is 3.7242 , which is a 372 trillion, trillion, trillion, million. But we’ve only 6.25 billion planets to work with. Therefore, we are many trillion planets short of the number needed to have the same conditions as here on earth. And this is before we consider any other variables!
Even for the 18 steps needed evolution, we need 18!, which is 6.4015 Again, way higher than the number of potential planets available. Of course, the case is the same as the 18 events necessary to get the evolved human-like aliens to the point of transmitting radio signals.
These humongous numbers illustrate how many combinations and permutations it would take to duplicate the requirements for a planet like ours sufficient to evolve an intelligent species with the ability to produce radio signals like those of we earthlings.
Therefore, on the basis of this analysis, and under the assumptions made, it is statistically impossible for another planet in the Milky Way, and probably the entire universe, to have intelligent beings like us who can transmit their version of “I Love Lucy.”
The SETI project is interesting but not very useful, unless perhaps, it can, like the NASA programs, serendipitously lead to other discoveries that might help advance science.
On that sad note, I’ll close with an excerpt from Carl Sagan’s book, “Pale Blue Dot: A Vision of the Human Future in Space.” Looking back at earth from 4 billion miles out, Sagan writes,
“From this distant vantage point, the Earth might not seem of any particular interest. But for us, it’s different. Consider again that dot. That’s here. That’s home. That’s us. On it everyone you love, everyone you know, everyone you ever heard of, every human being who ever was, lived out their lives. The aggregate of our joy and suffering, thousands of confident religions, ideologies, and economic doctrines, every hunter and forager, every hero and coward, every creator and destroyer of civilization, every king and peasant, every young couple in love, every mother and father, hopeful child, inventor and explorer, every teacher of morals, every corrupt politician, every superstar, every supreme leader, every saint and sinner in the history of our species lived there on a mote of dust suspended in a sunbeam.”