Are we the lone sentient life in the universe? So far, we have no evidence to the contrary, and yet the odds that not one single other planet has evolved intelligent life would appear, from a statistical standpoint, to be quite small. There are an estimated 250 billion (2.5 x 10¹¹ ) stars in the Milky Way alone, and over 70 sextillion (7 x 10²² ) in the visible universe, and many of them are surrounded by multiple planets.
Meanwhile, our 4.5 billion-year old Solar System exits in a universe that is estimated to be between 13.5 and 14 billion years old. Experts believe that there could be advanced civilizations out there that have existed for 1.8 gigayears (one gigayear = one billion years).
Fermi reasoned, if there are other advanced extraterrestrial civilizations, then why is there no evidence of such, like spacecraft or probes floating around the Milky Way. His question became famously known as the Fermi Paradox. The paradox is the contradiction between the high estimates of the probability of the existence of extraterrestrial civilizations and yet the lack of evidence for, or contact with, any such civilizations.
Given the extreme age of the universe, and its vast number of stars, if planets like Earth are at all typical, then there should be many advanced extraterrestrial civilizations out there, and at least a few in our own Milky Way. Another closely related question is the Great Silence, which poses the question: Even if space travel is too difficult, if life is out there, why don’t we at least detect some sign of civilization like radio transmissions?
Milan Cirkovic of the Astronomical Observatory in Belgrade, points out that the median age of terrestrial planets in the Milky Way is about 1.8 gigayears greater than the age of the Earth and the Solar System, which means that the median age of technological civilizations should be greater than the age of human civilization by the same amount. The vastness of this interval indicates that one or more processes must suppress observability of extraterrestrial communities.
Mike Treder of the Institute for Ethics and Emerging Technologies suggests that since there is, at this point, no direct and/or widely apparent evidence that extraterrestrial life exists, it likely means one of the following:
We are (A) the first intelligent beings ever to become capable of making our presence known, and leaving our planet. At this point, there are no other life forms out there as advanced as us. Or perhaps extraterrestrial life does exists, but for some reason extraterrestrial life is so very rare and so very far away we’ll never make contact anyway—making extraterrestrial life nonexistent in a practical sense at least.
Or is it (B) that many advanced civilizations have existed before us, but without exception, they have for some unknown reason, existed and/or expanded in such a way that they are completely undetectable by our instruments.
Or is it (C) There have been others, but they have all run into some sort of “cosmic roadblock” that eventually destroys them, or at least prevents their expansion beyond a small area.
Then ancients once believed that Earth was the center of the universe. We now know that Earth isn’t even at the center of the Solar System. The Solar System is not at the center of our galaxy, and our galaxy is not in any special position in contrast to the rest of the known universe. From a scientific viewpoint, there is no apparent reason to believe that Earth enjoys some privileged status.
Since Earth’s placement in space and time appears to be unremarkably random, proposition “A” seems fairly unlikely. Assuming humans evolved like other forms of life into our present state due to natural selection, then there’s really nothing all that mystical, special or remarkable about our development as a species either. Due to the shear numbers, there are almost certainly other planets capable of supporting at least some form of life. If that is so, then for Earthlings to be the very first species ever to make a noticeable mark on the universe, from a statistical perspective, is incredibly unlikely.
For proposition “B” to be correct would defy all logic. If potentially thousands, or even millions of advanced extraterrestrial civilizations exist in the known universe, then why would all of them, without exception, choose to expand or exist in such a way that they are completely undetectable? It’s conceivable that some might, or perhaps even the majority, but for all of them to be completely undetectable civilizations does not seem likely either.
Proposition C, according to Treder, appears to be more likely than A or B. If “survival of the fittest” follows similar pathways on other worlds, then our own “civilized” nature could be somewhat typical of extraterrestrial civilizations that have, or do, exist. Somehow, we all get to the point where we end up killing ourselves in a natural course of technological development and thereby self-inflict our own “cosmic roadblock”.
“Perhaps the most disturbing aspect of the Fermi Paradox is what it suggests for the future of our human civilization. Namely, that we have no future beyond earthly confinement and, quite possibly, extinction. Could advanced nanotechnology play a role in preventing that extinction? Or, more darkly, is it destined to be instrumental in carrying out humanity’s inevitable death sentence?” wonders Mike Treder, executive director of the Center for Responsible Nanotechnology (CRN).
Treder believes that some of the little understood new technologies now being developed such as nanotech, and others, could well be either our salvation or just as likely end up causing our ultimate destruction.
“Whatever civilizations have come before us have been unable to surpass the cosmic roadblock. They are either destroyed or limited in such a way that absolutely precludes their expansion into the visible universe. If that is indeed the case—and it would seem to be the most logical explanation for Fermi’s Paradox—then there is some immutable law that we too must expect to encounter at some point. We are, effectively, sentenced to death or, at best, life in the prison of a near-space bubble,” suggests Treder. “Atomically-precise exponential manufacturing could enable such concentrations of unprecedented power as to result in either terminal warfare or permanent enslavement of the human race. Of course, that sounds terribly apocalyptic, but it is worth considering that the warnings we heard at the start of the nuclear arms race, and the very real risks we faced in the height of the Cold War, were but precursors to a much greater threat posed by an arms race involving nano-built weaponry and its accompanying tools of surveillance and control.”
When we consider the chronological history of life on Earth, humans have only existed for a small fragment of time and our existence has always been precarious. The entire time we’ve existed, we been banding into various groups and attempting to kill each other—or at least are constantly in the process of developing more effective ways of killing each other—just in case. The US government, for example, spends on “Defense” (including “preemptive” warfare) and Homeland Security, 8 times what it spends on educating the next generation. There is enough nuclear weaponry in storage around the world to kill every living creature on the planet several times over. Clearly, we’re a species with poor odds of surviving indefinitely.
Our self-destructive natures aside, curiosity may end up killing more than the cats. The faster technology is advancing, the more our “leap now, look later” nature appears to grow as well. If evolution on Earth serves as a somewhat typical template for evolution of other life forms, then becoming a truly advanced civilization must be a very daunting task indeed and a very rare, if not impossible, achievement.
In fact, Sir Martin Rees, Great Britain’s Astronomer Royal and respected professor of astrophysics at Cambridge University has estimated that humans have only a 50-50 shot of making it through the 21st century. If Rees is right, and our standing on the planet is as precarious as he and others believe it is, then we may be alone due to a built-in evolutionary self-destruct button. Others have come before and others will exist after, but the cosmic roadblock may be an innate, finite nature, which only allows sentient life forms to exist for a very small window of time—windows of life which may be too small for our civilization to match up with the small windows of other civilizations that have been before or will come after.
In a contrary point of view, Milan Cirkovic believes that highly efficient city-state type of advanced technological civilizations could easily pass unnoticed even by much more advanced SETI equipment, especially if located near the Milky Way rim or other remote locations.