FERMI WAS RIGHT: SO WHERE ARE THEY?
Via Glenn Reynolds, this piece in Technology Review on a new twist to the Fermi Paradox makes the case that there may be an incredibly small number of intelligent, space faring civilizations in the entire universe - perhaps as few as 10:
The absence of alien probes visiting the solar system places severe limits on the number of advanced civilizations that could be exploring the galaxy.
The Fermi paradox focuses on the existence of advanced civilizations elsewhere in the galaxy. If these civilizations are out there–and many analyses suggest the galaxy should be teeming with life–why haven’t we seen evidence of them?
Today Carlos Cotta and Álvaro Morales from the University of Malaga in Spain add another angle to the discussion. One consideration is the speed at which a sufficiently advanced civilization could colonize the galaxy. Various analyses suggest that using spacecraft that travel at a tenth of the speed of light, a colonization wave could take some 50 million years to sweep the galaxy. Others have calculated that it may be closer to 13 billion years, which may explain why we have yet to spot extraterrestrials.
Cotta and Morales take a different tack by studying how automated probes sent ahead of the colonization could explore the galaxy. Obviously, this could advance much faster than the colonization wave front. The scenario involves a civilization sending out eight probes, each equipped with smaller subprobes for studying the regions that the host probe visits.
This is not a new scenario. One previous calculation suggests that in about 300 millions years, those eight probes could explore just 4 percent of the galaxy. The question that Cotta and Morales ask is this: what if several advanced civilizations were exploring the galaxy at the same time? Surely, if enough advanced civilizations were exploring simultaneously, one of their probes would end up visiting the solar system. So that fact we haven’t seen one places a limit on how many civilizations can be out there.
This is not only fascinating stuff, but a lot of fun as well. Next to politics, the search for extraterrestrial intelligence has been a favorite subject of mine since childhood. It parallels my fascination with space but, due to the speculative nature of the subject matter, forces me to stretch my thinking beyond facts and embrace a world of the mind unlike no other of which I am familiar. When contemplating the unimaginable distances and time periods that are necessary to give ETI serious thought, you exercise a part of the brain that is usually dormant - at least in rational laymen with an abiding interest in science but not the aptitude to get it down by the numbers.
Fermi’s Paradox, first uttered by Enrico Fermi at a lunch with several Los Alamos scientists in 1949, takes the statistical probability that there must be other intelligent species in the universe due to sheer numbers of possible planets, and asks an obvious question: So, where are they? Why haven’t they visited us? Why is there no physical evidence of them ever having been here?
Sorry, but as reliable as eyewitness accounts have been, there is no physical evidence that we’ve ever been visited - and that includes idiotic and insulting questions regarding who built the pyramids or carved the Easter Island statues. We humans are a very clever species and hardly need aliens to help us overcome small technical problems like how to haul a 10 ton block of stone the 4 miles from the Nile River to the Valley of Kings. It is insulting to humans to ascribe our ability to overcome these obstacles to anything except our own, native intelligence.
As for other “evidence,” no reputable scientist has ever come forth with physical evidence that could withstand the scrutiny of their peers. And even eyewitness accounts cannot confirm that what they report came from another planet. In short, as a scientist, Fermi was asking a perfectly legitimate question. We have no evidence of ET’s probes, or spaceships, or any other alien artifact despite the statistics that point to a universe that should be teeming with intelligent life.
And beyond that, there is the idea that a truly advanced civilization would probably require unlimited amounts of energy and would tap every atom and erg they could possibly get out of their own sun. Freeman Dyson speculated that such a race of beings would enclose their entire sun - perhaps their entire solar system - in a sphere in order to capture every atom of power possible (”Dyson Sphere”). The sphere would so alter the radiation signature of the star that it would be detected by even our crude by contrast instruments.
(A great treatment of a Dyson Sphere in pop culture was a Star Trek Next Gen episode that featured Scotty being trapped in a transporter loop for 70 years after becoming stranded on the surface of the sphere.)
A civilization that is advanced enough might attempt to re-engineer their entire galaxy. In Carl Sagan’s book Contact, Ellie Arroway sees a black hole at the center of the Milky Way galaxy “eating” stars in copious amounts. It turns out that the aliens who brought her to this particular planet were trying to alter the mass of the galaxy to keep if from flying apart - a nice trick if you can do it. Again, statistics say there should be civilizations capable of such a feat but so far, we have been unable to detect such an obvious beacon of intelligence elsewhere.
So, where are they? This one should send chills down your spine:
Another possibility is that intelligent species beyond a certain point of technological capability will destroy other intelligence as it appears. The idea that someone, or something, is destroying intelligent life in the universe has been well explored in science fiction[35] and scientific literature.[3] A species might undertake such extermination out of expansionist motives, paranoia, or simple aggression. In 1981, cosmologist Edward Harrison argued that such behavior would be an act of prudence: an intelligent species that has overcome its own self-destructive tendencies might view any other species bent on galactic expansion as a kind of virus.[36]
This hypothesis requires at least one civilization to have arisen in the past, and the first civilization would not have faced this problem.[37] However, it could still be that Earth is alone now. Like exploration, the extermination of other civilizations might be carried out with self-replicating spacecraft. Under such a scenario,[35] even if a civilization that created such machines were to disappear, the probes could outlive their creators, destroying civilizations far into the future.
If true, this argument reduces the number of visible civilizations in two ways - by destroying some civilizations, and forcing all others to remain quiet, under fear of discovery. (see They choose not to interact with us) as we have seen no signs of them.
So are we being incredibly stupid in sending out signals into the void announcing our presence as an intelligent species? Some scientists have actually advanced that argument and indeed, common sense caution might be the better part of valor in this case. I can just imagine these thousands, perhaps millions of civilizations out there who are cowering in fear of some Borg-like race of bloodthirsty aliens. Very kewl. But not likely.
What is much more likely is that Einstein is right, that light speed cannot be exceeded, and that intelligent species are reduced to building multi-generational ships if they wish to explore. The biggest problem with that idea is one of technological development on the home planet outrunning the technology that built the ship originally.
Suppose we built a ship that could travel at one tenth the speed of light. We send them off to Barnards Star 10 light years away, a trip that theoretically would take 100 years (relativistic effects on time don’t become obvious unless you are traveling above 90% the speed of light).
But let’s say 10 years after the ship leaves earth, we build a vehicle that can travel at 1/5 the speed of light (2/10ths). That ship would pass the first ship in about 40 years, in which case you have expended an enormous amount of effort to build the first ship basically for nothing.
Much more likely is the probe idea outlined in the article linked above. It would take much less effort to deploy probes to search the galaxy for that “needle in a haystack.” Even given the time frame allowed - 50 million years or more - a truly advanced civilization would no doubt have overcome many mundane problems that we deal with like ecological disasters, or perhaps even death itself.
Time is an artificial construct anyway. To beings so advanced, it may even be meaningless.
The probability is, we can’t detect the aliens because we don’t even know what we’re supposed to be looking for. And the thing that always bothers me about pop culture treatment of ET is that just because the probability of life on other planets is fairly good (we may even find life in our own solar system before too long), it doesn’t necessarily follow that intelligent life - self aware, cognizant abilities, etc.) would arise.
There is even a question as to whether complex life forms beyond viruses and bacteria could ever develop elsewhere except in extremely rare cases. But intelligence itself is not where evolution on any planet would be required to end up. That’s because intelligence is simply one of a million adaptations made by living creatures, no more surprising or necessary than a giraffe’s long neck or a cheetah’s speed. It eventually made us into a super-predator, but that was only after millions of years.
So despite what the statistics tell us about life elsewhere, the Fermi Paradox might indeed apply. At any given time in the existence of the universe, perhaps no more than a handful of intelligent beings exist who have the industrial know how, engineering skills, and scientific knowledge to leave their home planet and go exploring. It certainly would answer the question “Where are they,” although it will never put the issue to rest as long as we continue to reach for the stars ourselves.