N = R* x fp x ne x fl x fi x fc x L
—The Drake Equation
I was a Trekkie from day one. Lost In Space had debuted the year before, and even at 13 I realized how silly it was. Star Trek, on the other hand, was real science fiction for true nerds. It became my obsession for years to come. William Shatner’s voice over phrase from the title sequence, “to explore strange new worlds, to seek out new life and new civilizations, to boldly go where no man has gone before,” inspired me more than I care to admit.
Once I became political, I realized Star Trek embodied a lot of pretty reactionary ideas; the myth of the American frontier for one, and various Cold War and Vietnam War myths for another. And, of course, there was the sexism of “no man” frequently pointed out at the time. The show was steeped in American exceptionalism, yet I still hold a soft spot in my heart for the original series. But where are all the strange new worlds, the new life, and the new civilizations?
Or, as Enrico Fermi once asked: “Where is everybody?”
According to the Drake Equation, there should be 100 billion planets in our galaxy alone. About 50% of the Milky Way’s stars should have a planet. With all this potential for life, why are we confronted with the Fermi Paradox’s Great Silence?
Let’s leave aside criticisms of and revisions to the Drake Equation. Instead we’ll assume that its estimates are basically sound. According to Matt Williams “[T]he Fermi Paradox states that, given the sheer number of stars in the Universe (many of which are billions of years older than our own), the high-probability that even a small fraction would have planets capable of giving rise to intelligent species, the likelihood that some of them would develop interstellar travel, and the time it would take to travel from one side of our galaxy to the other (even allowing for sub-luminous speeds), humanity should have found some evidence of intelligent civilizations by now.” Yet the only planet that has life, not to mention intelligent life, is ours. Why haven’t we detected extraterrestrial life, let alone extraterrestrial intelligence (ETI)? It’s a conundrum that demands an answer, or at least a lot of speculation.
I can’t imagine that life on this planet, and humanity specifically, are some sort of special creation of an idiot god, a grandiose idea dwarfed by the incomprehensibility of the actual cosmos. The mathematics, even at its most conservative, does not support it. Nor do assertions like the simple-minded Hart-Tipler Conjecture make logical sense other than to reiterate that because we haven’t already detected ETIs they don’t exist. The simplest explanation is that life—simple microbial life—might very well teem across the universe, but that complex intelligent life is exceedingly rare.
Mars is our best bet for finding simple extraterrestrial life close at hand. Finding it even in fossil form would be monumental. But if the deafening silence from the rest of the universe is any indication, ETI is not likely to be discovered any time soon. Perhaps life becomes more unstable as it becomes more complex, limiting its capacity to produce intelligence. Complex life might not be capable of creating a stable natural environment for itself, or perhaps outside Extinction Level Events (asteroid strikes, solar fluctuations, etc.) make that environment unstable. Or if intelligence does evolve, maybe the civilization that results is only around for a short time, or it only broadcasts its existence for a short period as a consequence of succumbing to self-destruction, environmental destruction, or technology run amok.
These are all possible reasons, aggregated under the “Great Filter Hypothesis,” as to why intelligent life might not naturally arise or sustain itself for any length of time. But if ETIs are capable of evolving and surviving, and “if colonization is the rule,” according to Carl Sagan, “then even one spacefaring civilization would rapidly spread, in a time much shorter than the age of the galaxy, throughout the Milky Way. There would be colonies of colonies of colonies…” Must we conclude that ETIs don’t exist simply because they aren’t already here?
Not at all. Colonization might not be the rule, and interstellar travel might not be the norm. ETIs that venture into the stars might do so gradually, cautiously, and even ethically, with injunctions against colonizing populated but pre-technological worlds. The universe might be an exceedingly hostile place either naturally, due to starfaring killer alien civilizations, or Berserker/Cylon runaway technologies, requiring existing ETIs to remain hidden to keep from being annihilated. Aside from being extremely rare, ETIs might be otherwise camouflaged or in a state of hibernation. And there’s always the possibility that humanity has arrived early to the cosmic party or that we’re looking for ETIs in all the wrong places. There are plenty of reasons why advanced extraterrestrial civilizations could exist in the universe but still remain undetected.
There are tantalizing hints out there. Mysterious fast radio bursts; short-lived narrowband radio signals that appear to be aimed; indications of alien, energy-trapping megastructures surrounding nearby stars like Tabby’s Star (KIC 8462852); tentative biosignatures from planets near and far; and an odd “asteroid” dubbed ‘Oumuamua that slingshotted through our solar system only to mysteriously accelerate as it sped away—are all exciting but inconclusive clues. That hasn’t stopped generations of science fiction writers from turning all this speculation into genre tropes. My second novel, 1% Free, has lots of ETIs. My fictional explanation is that the various advanced extraterrestrial civilizations depicted all arose within five hundred years of each other because the Milky Way was originally seeded with organic life by a precocious, galaxy-spanning, alien progenitor species. We haven’t detected these ETIs because they are simultaneously co-evolving with humanity across the galaxy.
But what about intriguing hints that aliens are already here? I’m not talking about whether we’ve been covertly invaded by extraterrestrials a la John Carpenter’s film They Live. More interesting are a couple of speculative scientific theories being discussed regarding a “second genesis” here on earth. The “easy” version envisions some form of carbon-based life native to our planet that’s become alien by literally “rewriting the recipe for DNA.” In 2009, a NASA astrobiology fellow named Felisa Wolfe-Simon isolated an unusual strain of rod-shaped bacteria in the family Halomonadaceae from the hypersaline, alkaline environment of California’s Mono Lake. GFAJ-1. as it’s called, seems to metabolize arsenic to substitute for the phosphorus integral to all life on earth. The latest evidence casts doubt on that possibility, but debate is ongoing and not yet settled.
Carol Cleland and Shelley Copley coined the term “shadow biosphere” in 2005 for the scientific speculation of a hypothetical microbial biosphere based on essentially different biochemical and molecular processes from life as we currently know it. Carbon-based organisms based on RNA instead of DNA, having different amino acids in their proteins or base/sugar molecular units in their nucleic acids, relying on mirror-image chemistry, or metabolizing nonstandard amino acids or arsenic instead of phosphorus are the main options. For instance, might life have evolved on Earth more than once—perhaps centered around RNA instead of DNA—involving the existence of microorganisms with no evolutionary connection to any other known form of life? Might such life still exist today unnoticed because, for instance, it doesn’t contain ribosomes which are normally used to detect living microorganisms? And might Lynn Margulis’s version of the theory of symbiogenesis—where individual microorganisms cooperate and incorporate to form new, more complex life—be used to speculate on the existence of complex RNA alien life here on Earth? Discovering any such “shadow biosphere,” GFAJ-1 notwithstanding, so far has been elusive.
The “hard” version to have a “second genesis” is to find life on this planet that is fundamentally different from the carbon-based life we’re familiar with. The most frequent option postulates alien life native to earth based on silicon instead of carbon, like the fanciful silicon creature called “horta” in the Star Trek episode “The Devil in the Dark” that lived underground and burrowed through solid rock. Whereas a “shadow biosphere” entails alternate life hiding in plain sight, visible but not really seen, hypothetical silicon-based life would constitute a parallel biosphere that we would not even be aware exists. Such a parallel biosphere might appear to involve familiar, non-organic processes that we don’t recognize as being alive at all. Consider the fantasy of silicon life living deep within the earth’s crust that is somehow complicit in earthquakes or plate tectonics. We would have no way of knowing that such normal geological processes involved a parallel silicon biosphere, say a silicon-based “horta-culture.”
As an inveterate leftist, imagining political alternatives to the state, capitalism, patriarchy, and white supremacy are my bread and butter. No wonder then that I’m equally fascinated by the scientific alternatives of ETI’s and “shadow biospheres.” I’m thoroughly dispirited by the mess we humans have made of the planet and our social realm so a little political and scientific utopianism is inevitable.
SOURCES:
Personal recollections
“Direct contact among galactic civilizations by relativistic interstellar spaceflight” by Carl Sagan (Planetary and Space Science, 1963)
Intelligent life in the universe by I.S. Shklovskii & Carl Sagan (1-1-1966)
“The Quest for Extraterrestrial Intelligence” by Carl Sagan (Cosmic Search; v. 1, n. 2; 1966)
“The Great Silence – the Controversy Concerning Extraterrestrial Intelligent Life” by G.D. Brin (Quarterly Journal of the Royal Astronomical Society; v.24, n. 3; 1983)
“The Great Filter – Are We Almost Past It?” by Robin Hanson (paper, 9-15-1998)
Symbiotic Planet: A New Look at Evolution by Lynn Margulis (1998)
“Is there a common chemical model for life in the universe?” by Steven A Benner, Alonso Ricardo and Matthew A Carrigan (Current Opinion in Chemical Biology, 2004, Science Direct)
“The possibility of alternative microbial life on Earth” by C.E. Cleland, S.D. Copley (International J. Astrobiology; v. 4, n. 3-4; 2005)
“The Fermi Paradox” Episodes 1- 24 (Astronomy Cast, 2-19-2007)
“Signatures of a Shadow Biosphere” by Paul C.W. Davies, Steven A. Benner, Carol E. Cleland, Charles H. Lineweaver, Christopher P. McKay, Felisa Wolfe-Simon (Astrobiology; v. 9, n. 2, 2009)
“A bacterium that can grow by using arsenic instead of phosphorus” by F. Wolfe-Simon, J.S. Blum, T.R. Kulp, G.W. Gordon, S.E. Hoeft, J. Pett-Ridge, J.F. Stolz, S.M. Webb, P.K. Weber, P.C.W. Davies, A.D. Anbar, R.S. Oremland (Science #332, 11-3-2010)
The Politics of Star Trek: Justice, War, and the Future by George A. Gonzalez (2015)
“What is the Drake Equation?” by Matt Williams (Universe Today, 6-13-2017)
“Beyond ‘Fermi’s Paradox,” Episodes I-XVI (Universe Today, 4-7-2015 thru 1-7-2021)
Buy my book, 1% Free, here.
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