Enrico Fermi was a physicist working at Los Alamos National Laboratory in the 1950s. Following a discussion about extraterrestrial intelligence with colleagues, he apocryphally posed the question, ‘Where are they?’. By which he meant that it seemed impossible, if life existed elsewhere in the universe, that we had not yet seen evidence of it given the vast amounts of time that such civilizations would have had to spread out into the cosmos. Even our rudimentary observatories of that era should have been able to spot their galactic Hoover Dams, interstellar expressways and other engineering projects, he reasoned. With the exception of a few UFO nuts, nobody had evidence of visitations to Earth, which should have been much more frequent if aliens had been colonizing the Milky Way galaxy with a billion-year head start. Fermi’s paradox is a direct affront to both the UFO believers and those scientists who’ve devoted their efforts to projects like SETI. Really, shouldn’t we be able to detect much more than just feeble radio emissions from an advanced supercivilization?

But neither the UFO crowd nor the scientists have been content to shrug their shoulders at Fermi’s logic and walk away from the problem. It may be because people from both groups, like myself, deeply want to live in a universe populated by other intelligences. How do we keep that possibility alive, in light of Fermi’s (lack of) evidence?

Many people have proposed ‘solutions’ to his paradox, conditions under which life may still exist beyond Earth, but for a variety of reasons has remained invisible to us.

Here are five of my own favorite answers to Fermi’s question:

 

1) Fermi’s assumptions about galactic engineering are wrong

Fermi was surprised at the lack of clearly visible artifacts of a galactic alien civilization. But that assumption was anthropocentric, based on the belief that an advanced alien species would do what we have done on Planet Earth, just on a larger scale. There should have been huge, artificial structures — perhaps as large as entire star systems — visible in outer space. His perspective made sense in the 1950s when twentieth-century modernization projects were in full swing around the globe. Egypt’s Aswan dam, which was initiated in 1954 but not completed until 1970, was typical of these mega engineering projects. The Panama canal, in use since the beginning of the twentieth century, was another. It would have been logical therefore for Fermi to share a belief with other scientists that the future of humanity would involve even more explicit and ostentatious mastery of nature.

But in the decades since then, our civilization has actually taken the opposite tack. We’ve become obsessed with building tools at smaller, rather than larger scales. Computers, which in Fermi’s day took up the size of a research lab, now fit in between the sleeves of paper in a talking birthday card. Microchip manufacturers will be moving to a 32nm fabrication process in 2011, with individual transistors being the size of the smallest biological viruses. 60,000 of these 32nm transistors will fit on the head of a pin. The hulking ENIAC computer used in Fermi’s day contained around 17,000 vacuum tubes.

Soon, we may be able to harness tremendous energy at the quantum scale, obviating the need for a Kardashev-style supercivilization. When we do send probes out into the interstellar medium, perhaps as early as the end of this century, they are not likely to be much bigger than say, a toaster. But because they will contain quantum-scale computers and sensors, these tiny probes will be able to perform as well as a gigantic spaceship, at a cost of much less fuel. There could already be a toaster-probe lurking somewhere in our solar system, less detectable than the millions of rocky asteroids that have yet to be systematically tracked.

 

2) The galaxy is full of Ewoks

Many critics of the third Star Wars movie didn’t like the Ewoks, because the teddy-bear-like creatures felt out of place in the science fiction universe that George Lucas crafted in the first two films. But they might turn out to be the most realistic portrayal of ET life in the trilogy: there are likely many more planets populated by creatures like the Ewoks than by civilizations capable of interstellar space travel. Consider the example of Earth: for the first 200,000 years of Homo Sapiens on this planet, we had much in common with the cuddly forest-dwellers of the fictional moon Endor. We made rudimentary tools, we trapped animals for food, we huddled in fear of larger predators. Some of us did – and still do – live in trees. Paleontologists even contend that we were shorter and had hair covering more of our bodies than we do now.

Compared to the millennia that we spent living in primitive conditions, the modern period is contained in a mere 300-year blink of an eye. The odds of meeting an extraterrestrial species during its Ewok phase are much greater than meeting a technological civilization, as far as we can tell from history on Earth. The Ewok society is also much more stable than ours – without the upheavals of constant technological progress, a species could go on for millennia in a state of equilibrium with nature. It is hard to say that about modern-day Earth, where our ecosystem and political structures are under the constant assault of modernity. Earth 1000 years hence won’t look anything like it does today, barring some kind of disaster that sends us back to a more stable and recognizable stone age.

 

3) They have already visited us and we refuse to acknowledge it

Fermi and his colleagues were dismissive of UFO stories, but what if the solution to Fermi’s paradox has been staring us in the face all along? By 1950, there had already been a number of high profile sightings of unusual objects in the sky. Beginning with stories by Allied airmen in World War 2 of strange ‘foo fighters’ that followed their bombers over the skies of Europe, the western world was atwitter with stories of possible visitors from beyond Earth. Another famous sighting by Kenneth Arnold in 1947 set off a nation-wide flap of UFO reports, and culminated with the mysterious events at Roswell New Mexico in July of that year. Fermi and his colleagues must have been aware of public reports of UFOs (some not far from their own lab). But what did they make of these stories? Did the accounts of small, metallic objects with incredible handling characteristics not satisfy Fermi’s burning question? And if not, why not?

Part of this could be attributed to the scientific method. Serious scientists have always had a difficult time with the UFO topic, because to date (as far as the public knows) no ET phenomenon has been subjected to systematic laboratory experiment. The plural of ‘anecdote’, as they say, is not data. The fringe element of lunatics who formed around the edge of the UFO story also meant that scientists who did get involved with the phenomenon risked losing their credibility, not something that Fermi or his colleagues would have been eager to do as government employees.

But what if UFO stories go largely ignored because of some bigger civilizational blindspot? The zipping metallic spheres reported in the news in the late 1940s clearly didn’t fit Fermi’s preconceptions about what alien visitation should look like. But taking an anthropocentric view on the matter might blind us to possibilities that are literally, alien to us. Perhaps aliens would be so shocking to our sense of reality that we would be unable to ‘see’ them even if they were staring us right in the face. Imagine an alien piloting a shiny metallic craft through our atmosphere finding that to be the most blatantly obvious sign of “hello” possible. Meanwhile, humans on the ground looking up might just shake their heads and think, “nah, it can’t be”.

 

4) There is an established protocol for contact

Also known as the ‘zoo hypothesis’ and more popularly as the prime directive from Star Trek. Also, judging by the behavior of Captain James T. Kirk, the most frequently violated directive in the entire Starfleet manual. But what if aliens, with much more discipline and experience than our fictional space captain, really do have some established set of rules for dealing with less advanced species? A no-contact rule would definitely make sense given the disastrous consequences of contact between European explorers and native populations during the age of discovery. And those encounters, as horrible as some of them were, involved members of the same species.

If life really is plentiful in the galaxy, there might already be a history of encounters between intelligent species upon which they have collectively developed a system for incorporating newcomers as painlessly as possible. Perhaps they have found, based on experience, that there is an appropriate stage in a civilization’s development when it is acceptable to introduce themselves. Maybe a civilization needs to have evolved a stable, planetary government. Perhaps its citizens have to have been inured to the existence of ET life by the discovery of microorganisms already in space. In that case, perhaps the intelligent aliens will show up shortly after we discover evidence of bacteriological life on Mars. The discovery of a second genesis, in such close proximity to Earth would instantly force any logical mind to realize the obvious: the universe would necessarily be teeming with life. If aliens were consciously hiding their existence from us, at that point the jig would almost certainly be up.

“Sorry guys, you got us. We’ve just been waiting for you to make the discovery yourselves so we wouldn’t freak you out.”

 

5) They can observe us without needing to visit

Since the year 1886, when Heinrich Rudolf Herz tested the first radio transmitter, the earth has been streaming electromagnetic radiation into outer space. The Earth is now at the center of an expanding bubble of electromagnetic communication, advertising our existence to all who would care to listen. The bubble, expanding at the speed of light, contains all of the man-made electromagnetic transmissions of the earth – radio, TV, radar and so on. In theory, an alien civilization within a radius of 125 light years could receive these signals, and form their opinion about the earth by analyzing them. There are more than 25,000 stars within that range, although that’s not many by galactic standards.

Even though we are still early on in our technological development, we can already detect planets orbiting stars much further away. Our detection equipment is getting better every year, as we harness the exponentially accelerating power of computers to make our measurements even more precise. Consider the exponential growth in the number of known exoplanets. In 1992, we discovered evidence of the first planet orbiting a star beyond our solar system. By the end of the 1990s, that number had grown by dozens more, and by last year we had about 500 known exoplanets on the books. But in 2011 alone, that number is expected to jump by more than 1200, thanks to the Kepler telescope. Within 20 more years, we might be able to visually image some of those planets, and use spectrography to discern the chemical composition of their atmospheres.

Now fast-forward a thousand years. Our imaging and remote detection capabilities are likely to be so advanced they might appear godlike to an observer today. Right now our satellites can read your license plate from hundreds of miles up in orbit. Might we be able to read a license place on the Planet Gliese 581 g by then? And if we could, what would be the point of burning all of the required fuel and traversing all those many light years, just to buzz overhead in our silvery UFO and wave hello?