Where Are They?
Are we alone? Humans
have been endeavoring to find an answer to this question for generations. Many debates have ensued about the true
answer. The optimists have generally
held sway in the debate. In the 1930s, this optimism captured the physicist
Enrico Fermi. He was heavily persuaded
by the argument that the vast number of stars in the universe must imply that
some of them must host planets with intelligent life. This line of reasoning
led Fermi to ask the question "Where are they?" If there is intelligent life out there, why
we have not been contacted is a mystery. Radio astronomers have listened for
radio messages and heard none. Our skies are not filled with alien visitors
observing us or trying to contact us. There is no concrete evidence of
"ancient astronauts" or alien visitations in earlier Earth history.
In a further demonstration of optimism, theorists have even
argued that any one civilization could colonize all the habitable planets in
the galaxy. Not only could it colonize
the Milky Way, but it could do so on a time scale short compared to the age of
the galaxy. Such a civilization could feasibly explore the galaxy without
colonization by sending spacecraft to other planetary systems. These probes
could then use local materials to replicate themselves and they could rapidly
propagate through the galaxy, sending information back at light speed to the
originators. If this sounds far-fetched, remember that such a scenario requires
only a modest extrapolation of our current technology — we are probably less
than 100 years from robots that can construct other robots and propulsion
systems that can reach a tenth the speed of light in space.
If this were truly the case, we might expect that we have
been contacted by an extraterrestrial civilization. Polls in the
Popular culture paints two opposing versions of the alien
myth. The first is the optimistic view, expressed by movies such as E.T., Close Encounters of the
Third Kind, and more recently by Contact.
This view demonstrates our desire for knowledge, camaraderie in a vast
universe, and even salvation. Second is the pessimistic view, seen in movies
such as Alien
and Independence Day,
which places us at jeopardy in a universe of superior life forms. The belief in
aliens can be equated with a modern religious metaphor. Perhaps a more
interesting question than "Are we alone?" is "Why are we so
lonely?"
There are other logical conclusions other than that arrived
at by Fermi. One conclusion is that there are no other aliens — intelligent
life is a unique consequence of random events in the universe. Alternatively,
the universe could be heavily populated, but the nearest civilizations are in
distant galaxies. Their radio messages would be million of years old by the
time they reached Earth. Spaceships
would be unlikely to reach Earth if limited to speeds less than that of light,
as current physics demands. It is entirely consistent with our current
knowledge to propose that simple microbial life is quite common in the
universe, but that intelligence and technology are extremely rare.
It is also possible that space exploration and the desire
for communication are uniquely human characteristics. After all, it can be
argued that there is more than one intelligent species on our planet but that
the technology and desire to explore and communicate are unique to humans.
Technology is not even universal among human societies. Are humans fated to be
explorers, bridge-builders, and scientists rather than artists, athletes, or
daydreamers? Is the stereotyped aggressive Westerner more representative of the
essence of humanity than the stereotyped contemplative Easterner? Our
technocracy may be just one type of cultural activity rather than a natural
consequence of biological evolution. Historically, patterns we once assumed to
be results of our biology have turned out to be consequences of cultural
influences (confusion between these two has led to racist and sexist biases
that we are still trying to overcome). We have all been influenced by the
appealing image from science fiction of space exploration and communication as
a universal cultural activity. In fact, it is absurdly anthropocentric to
suppose that beings on other planets would resemble us physically, psychologically,
or socially.
Possibly the most significant answer to the question
"where are they?" is that we may be separated from aliens more by
evolutionary time than by actual physical space. Let us conduct a hypothetical
experiment. Imagine a planetary twin of Earth that started evolving at exactly
the same time. Even if life on both planets chose similar biochemical pathways,
organisms on the two planets are likely to be out of evolutionary phase with
one another. Just a slight difference in
temperature between the planets could cause the evolutionary "clocks"
on the two planets to be out of synch. If even 1 percent out of synch, life on our twin would be 40
million years behind or ahead of us. This is as far from us
evolutionarily as we are from early mammals. If the clocks differ by 10% to
15%, then we are talking about the enormous evolutionary difference between
single-celled microorganisms and ourselves! The timing argument carries one
important consequence. We have had the capability for interstellar communication
for only 50 years, which is a mere instant in evolutionary and cosmic time. Due
to the time it takes signals to travel through interstellar space, it is likely
that any civilization with which we could make contact will be far more
advanced than us, by thousands or perhaps millions of years. Even if we were at the same evolutionary
stage as our twin, the large distances coupled with anticipated lifetime of
civilizations (the oldest civilizations on Earth have lasted only thousands of
years) makes the idea of communication futile.
Optimists in the search for extraterrestrial intelligence
have an answer for the bleak scenario where intelligent life is rare in the
galaxy. Rather than use signals for communication from point to point, alien
civilizations might use signals to store information in a vast, cosmic
internet. If one civilization succeeded in sending probes across the galaxy,
they could use these probes to set up a communication network across the
galaxy. These artificial stations could beam information at planets, collect
information from planets with intelligent life forms, and store the information
in a growing database. Each newly intelligent civilization would not have to
wait thousands of years of light travel time to communicate across the galaxy;
they would only have to wait the much shorter time to tap into the nearest node
of the network. The information in this cosmic internet would survive the death
of any civilization and act as a kind of galactic consciousness.
All of these are hypothetical ideas, but we should recall
the words of physicist Freeman Dyson: "Nature always has more imagination
than us." We are a young
intelligent species, peering into the vastness of our cosmic environment with
the naivety of a newborn. We may be
surprised at what we find.
Recommendations:
THE ORIGIN OF LIFE ON EARTH
EVOLUTION AND INTELLIGENCE
FROM MOLECULES TO CELLS
THE NATURE OF LIFE
LIFE AS DIGITAL INFORMATION
NATURAL SELECTION
EARLY COSMOLOGIES
DIVIDING TIME