The science of planet formation is not sufficiently well
developed to exclude solar systems that do not resemble our own. Indeed it
seems the laws of physics as we understand them allow for as much variety of
star systems as there are initial conditions. It makes sense then, to not presume
what kinds of worlds we can expect to find based on our sample size of one.
In looking for extraterrestrial life some have limited their focus to finding earth-twin biology. They go so far as to establish criteria that would eliminate much of the diversity of life on our own planet to narrow the field down to some favoured grouping of arbitrary selection. There are others who have attempted to define life not in terms of amino acids or photosynthesis or other such wet-ware characteristics and instead focused on the processes that are recognizably life-like. This is most certainly a preferential approach to take if we wish to meet with success in identifying other life, certainly life that we could potentially communicate with. The former approach is perhaps best suited to narrowing the field assuming the observer is spoiled for choice in identifying worlds acceptable for future human habitation, as finding a nascent earth-like biology would certainly make the terra-formation process significantly easier and less expensive. In Robert J. Sawyer's novel Calculating God, he imagines alien civilizations that have entombed themselves in virtual worlds presumably to escape death and have left the physical realm, their planets now barren and devoid of life. In an admittedly poorly written short story of mine I imagined a not too dissimilar scenario as a fate for the future of humanity, only I also imagined a form of artificial life serving as our caretakers and ultimately taking the reins from us as rulers of the physical domain. Certainly it seems that given our present technological course we will be able to realize virtual worlds akin to that seen in The Matrix supervised by artificial intelligences before we develop the technology to conveniently travel to distant planets. Indeed, there is a possibility that we may never develop into a significant interstellar species, peering over our fence perhaps, but never leaving our own backyard. Supposing this possibility exists for all technological civilizations seems no more far-fetched than supposing that interstellar travel and communication is a possibility for all technological civilizations and we should see no reason why it should be outright dismissed. There then exists the very real likelihood that the first intelligent life we would encounter would not be biological entities evolved in the primordial womb of some planet, but rather the evolutionary descendants of such beings, perhaps involving sophisticated synthetic biology or being beyond biology altogether. Such post-aliens (a term intended to evoke post-human) would most likely be longer lived and more stable than their predecessors, and perhaps would be the only ones to truly reach out to the stars. Such an alien race would fit all of our hopes of a superior and technologically advanced civilization that has dispersed amongst the stars and looked deep into the mysteries of the universe. And yet we would miss such life-forms. We would be completely and utterly blind to their tell-tale signs, stuck as we would be looking for bio-signatures and radio waves. Searching for a specific chemistry such as the signs of carbon based life as we know it on earth may be as short-sighted as looking for flowers in a garden by scent, using the scent of a rose as a template. While you may find roses, you will miss all the other flowers, and by extent the richness of the garden using such a narrow field. If we are interested in life in all its forms then we need to look for signatures that can broadly encompass all the various forms we can imagine, while excluding that which we know to be noise, the signature of what we know to be life-less.
In looking for extraterrestrial life some have limited their focus to finding earth-twin biology. They go so far as to establish criteria that would eliminate much of the diversity of life on our own planet to narrow the field down to some favoured grouping of arbitrary selection. There are others who have attempted to define life not in terms of amino acids or photosynthesis or other such wet-ware characteristics and instead focused on the processes that are recognizably life-like. This is most certainly a preferential approach to take if we wish to meet with success in identifying other life, certainly life that we could potentially communicate with. The former approach is perhaps best suited to narrowing the field assuming the observer is spoiled for choice in identifying worlds acceptable for future human habitation, as finding a nascent earth-like biology would certainly make the terra-formation process significantly easier and less expensive. In Robert J. Sawyer's novel Calculating God, he imagines alien civilizations that have entombed themselves in virtual worlds presumably to escape death and have left the physical realm, their planets now barren and devoid of life. In an admittedly poorly written short story of mine I imagined a not too dissimilar scenario as a fate for the future of humanity, only I also imagined a form of artificial life serving as our caretakers and ultimately taking the reins from us as rulers of the physical domain. Certainly it seems that given our present technological course we will be able to realize virtual worlds akin to that seen in The Matrix supervised by artificial intelligences before we develop the technology to conveniently travel to distant planets. Indeed, there is a possibility that we may never develop into a significant interstellar species, peering over our fence perhaps, but never leaving our own backyard. Supposing this possibility exists for all technological civilizations seems no more far-fetched than supposing that interstellar travel and communication is a possibility for all technological civilizations and we should see no reason why it should be outright dismissed. There then exists the very real likelihood that the first intelligent life we would encounter would not be biological entities evolved in the primordial womb of some planet, but rather the evolutionary descendants of such beings, perhaps involving sophisticated synthetic biology or being beyond biology altogether. Such post-aliens (a term intended to evoke post-human) would most likely be longer lived and more stable than their predecessors, and perhaps would be the only ones to truly reach out to the stars. Such an alien race would fit all of our hopes of a superior and technologically advanced civilization that has dispersed amongst the stars and looked deep into the mysteries of the universe. And yet we would miss such life-forms. We would be completely and utterly blind to their tell-tale signs, stuck as we would be looking for bio-signatures and radio waves. Searching for a specific chemistry such as the signs of carbon based life as we know it on earth may be as short-sighted as looking for flowers in a garden by scent, using the scent of a rose as a template. While you may find roses, you will miss all the other flowers, and by extent the richness of the garden using such a narrow field. If we are interested in life in all its forms then we need to look for signatures that can broadly encompass all the various forms we can imagine, while excluding that which we know to be noise, the signature of what we know to be life-less.
Some theories on extra-terrestrial life become particularly
absurd in their insistence on resembling the most minute details of life here
on earth. Supposing for example that a technological society must first
manipulate fire and that life that evolves in conditions that preclude fire
cannot become technologically advanced, or supposing that significant
intelligence can only arise in predators due to the cognitive demands of
hunting. It gets quite ridiculous, at some point we must admit we are not
interested in extra-terrestrial life, or even intelligent extra-terrestrial
life, no, we are only interested in warm blooded mammalian humanoids preferably
speaking English who happen to differ from us only in ways that are superficial
and entirely unimportant. If human beings and the primates died off on our
planet and life as we know it was left alone for several millions of years of
evolution, which species would we expect to achieve a technological society:
dolphins? elephants? octopuses? crows? rats? All show remarkable signs of
intelligence and surprise us the more we study them. Yet they diverge from us
in many ways. It does not take a great deal of imagination to conjure up images
in one's head of technologically advanced races of any of the above species, so
why should we be surprised at the thought of aliens that diverge from us at
least as much as life on our own planet does?
One thing we should not forget with technological civilizations is that if they are long-lived (and a civilization must necessarily be long-lived for us to have a reasonable chance of detecting them) then they must be efficient. Radio signals are an inefficient means of local communication, so much of the signal is dispersed over an area that is not the intended recipient, and indeed it seems that over the next few decades our radio signals will all effectively dry up as we transition towards targeted high resolution communication methods. If a civilization is technological and long-lived then it is not a stretch to imagine that it is collectively intelligent and can therefore select the least energy intensive alternative in a given scenario. As an example, Dyson Spheres are postulated constructs that envelop a planet and its star, requiring all the matter in a solar system to construct and absorbing 100% of the star's energy output so that it is available to the residents of the planet that built it. Such a construct would allow an energy demanding civilization to at least temporarily quench its thirst. But it would be far less energy intensive and therefore preferable for such a civilization to manage its resources more carefully or develop radical technologies (such as cold fusion or other vaguely science fiction energy generators) than to undertake such an endeavour So much so that we should be incredibly lucky to ever encounter such a preposterous structure as a Dyson Sphere. On intelligent civilizations behaving intelligently many will counter that humanity, an intelligent civilization, does not behave intelligently on a global scale, it still exhibits the dumb, occasionally self-destructive nature of primitive life in a container competing for food. The first mistake is assuming that our civilization is an intelligent one. While technological, it is not intelligent, on an interstellar scale our highest achievements are doorknob dumb. We are ugly eyeless tadpoles in a vast unexplored pond. Given the pace of our technological advancement and its acceleration and the consequences that come with it, it is clear that with great power comes great potential to destroy one's self. If we are to be long-lived, that is survive into the future for tens of thousands of years and longer as a technological civilization (not a series of rises and falls so that on a cosmic scale we remain essentially stationary) then we must counter the ease with which we can end our civilization with appropriate measures. The ability to incorporate such measures is a sign of collective intelligence. In effect, a system that gives rise to nuclear warheads must give rise to equally powerful counters if it is to be long-lived, and the emergence of such counters is a signature of system-level intelligence. Just as an arms race exists between individuals competing for resources with which to propagate their genetic code, on a system level an arms race arises between the system's ability to destroy itself and its defences against such destruction. If the system's ability to destroy itself is able to sufficiently outpace its self-preserving defences then the system tends towards instability, and this instability leads towards the self-destruction of the system. The time-scale over which such instability can continue is dependent on many factors, but it is apparent that when long-lived is taken to be on the order of millions of years, we cannot expect a system tending towards runaway instability to be long-lived in any meaningful sense.
Living systems grow together, blurring the lines between
where one system ends and the next begins, and create feedback loops within
themselves. It is a natural characteristic of life. What evolves is a natural
interdependence that becomes necessary for the system's survival and yet
incredibly complicated in its interconnections. The more we learn out the
ecosystems of our own planet, the more incredible it may seem that life exists
at all. If we remove or disrupt one system, it seems the house of cards falls.
It then seems difficult to imagine life on a planet without water, without
plate tectonics, without seasons, without a night and day cycle, etcetera. To think
that it must be so is a mistake, akin to observing the interplay between insect
and plant life and concluding that neither could exist without the other and
therefore they must arise simultaneously if either is to have long term
survival. While the lack of life on other worlds within our solar system gives
us pause and good reason to conclude that specific conditions are required for
life, putting strong restrictions on those conditions and dictating them on our
only sample size ignores the broader picture: life only needs a crack to stick
its foot in the door, once it's in it will begin to make itself at home. Our
own planet shows us this time and again with the diversity of life we observe,
extremophiles that exist without oxygen, or without sunlight, or in searing hot
temperatures, when it comes to making do with what is available, life certainly
seems up to the challenge. The problem of course is determining what
constitutes a crack big enough for the foot of life to get through. A callous
survey of our own planet and the solar system may cause us to conclude a
goldilocks criteria: if conditions are not just right, life cannot arise. Even
then we narrow the field further by assuming that the only way to achieve these
restrictive conditions is in the same way our own planet has. Take for example
the assumption that life requires liquid water. Water is a remarkable and an
abundant substance, but its incredible properties have about as much to do with
the amount we have studied it as they do the substance itself. Accepting liquid
water as a requirement for life, it would seem reasonable that a planet must be
within the goldilocks zone of its parent star. Each star has a certain stellar
radius and luminosity, and a given orbital radius will yield a planet's black
body temperature. But a planet's true temperature can be cooler than it's black
body temperature owing to its albedo, and it can be much hotter due to the
greenhouse effect. Allowing for these factors, the goldilocks zone around a
given star increases. But a planet can further modify its temperature with
internal heating, such as a high amount of tectonic activity owing to a large
planetary mass or tidal forces from neighbouring bodies, or radioactive decay of
elements in its core. So much so in fact that Jupiter's moon Europa remains a
candidate for liquid water under its surface despite being far past the frost
line of our sun. The goldilocks zone is then not so well defined, for our own
solar system it could well extend from Venus to Jupiter, a distance of approximately
6.5 AU, hardly the narrow band existing between Venus and Mars that
rare-earther's would have you believe. When we look at our planet we will find
conditions are always "just right" because they have been fine tuned
over millennia to be so. When we consider the variety of places we find life,
and its persistence in the face of natural disasters, it seems life is actually
fairly robust and resilient, not some tenuous wispy almost ethereal force that
with the slightest change in parameters collapses like some wave function into
non-existence. At the same time, all life on our planet is interacting as part
of a system, so highly divergent forms of life would be competing with the
composition of the planet, so much so that they could not co-exist. Further,
once one life-form has carved out a niche, the path of least resistance for
subsequent life-forms will no doubt exploit that life-form in some way.
In the search for extra-terrestrial intelligence it has been
said that when we hear from E.T.s they won't be Neanderthal or even comparable
to our current technology level, but far more advanced. This is a reasonable
assumption. Our civilization has only been capable of broadcasting radio
signals powerful enough to leave the solar system as more than random noise in
less than a hundred years. On a galactic scale we have been dark up until that
point. We would be unable to detect a race less advanced than our own. Further
it stands to reason that if we are going to pick up any signals they should be
strong signals, which requires further technological advancement. And no doubt
these signals would need to be sent continuously and for a long duration of
time for us to have a reasonable chance of picking them up. So a
technologically advanced civilization has to send continual high strength
broadcast signals advertising their presence over a long period of time. Such a
civilization would have been broadcasting at higher power than we have up until
now and for a longer period of time than we have been broadcasting. Therefore
the expectation that they are more technologically advanced than ourselves is
the most reasonable. However, these broadcasts would need to be purposeful,
intended to advertise the presence of intelligent life to other intelligent
life. Knowing that competition is fundamental not only to all life that we know
of but to the basic building blocks, the molecules that form the essential
ingredients of life, it is by no means a stretch to consider that competition
between life forms is integral to all life that could possibly exist. That
being the case it is reasonable to assume that life must be wary of the
presence of other life. E.T. enthusiasts often seem out of touch with reality
when they excitedly picture advanced post-war civilizations that are so bold as
to advertise their location and relative technological advancement to all who
care to look simply in the pursuit of further knowledge. If technological
civilizations have existed in our galaxy for long, there may already be
histories of civilizations colliding and subsequent devastation for one or
both. An advanced civilization might even be imagined to be a survivor of such
a conflict and therefore wise to the foolishness of advertising. Advanced
civilizations may simply listen, waiting for foolhardy early civilizations to
send their first signals, and then pounce on them, perhaps exploiting the
planet's biology and effectively silencing the broadcasts. It would only take a
few long-lived such civilizations within reasonable proximity to make the
airwaves dark, even if the neighbourhood was teeming with advanced
civilizations. We would be extremely lucky to catch a short-lived broadcast in
such a case. In the Drake equation this scenario is represented by a low value
for L, the length of time for which a technologically advanced broadcasting
civilization releases detectable signs into space. It might be imagined that
only a naive civilization would expose themselves with such broadcasting, or a
veteran interstellar civilization confident that it held dominant position. Any
mid-tier civilizations would be dark either through being silenced or by being
resourcefully paranoid.
