Exobiology is the portion of astrobiology that focuses solely upon extraterrestrial life.
Does intelligent life exist in the universe other than on the Earth? So far we have no proof or even evidence of any other civilizations being in existence. In this vast, vast universe, how can it be that we have no indication of at least one other technologically advanced civilization? Perhaps it is because of the huge distances involved coupled with the "universal speed limit" ... the fact that nothing can travel faster than the speed of light. The nearest star is four light years from Earth. So if we could radio some civilization there, each message would take four years in transmit each way. Most of the "local" stars are hundreds or thousands of light years distance from us.
Can it be that the advanced extraterrestrial civilizations in existence are simply too far from us, and spread out from each other, to allow for electromagnetic emanation indications of them such as radio and television to reach us without having dissipated to such an extent that we cannot discern them form the electromagnetic "background noise" of the universe? Or are we indeed aone... the only technological beings in the universe.
Assuming that the universe is far too large for us to be its' only intelligent inhabitants, what might we imagine to be the kind of species that could have advanced to a level of technology simlar to ours? What type of beings could have advanced beyond our technology? What kind of extraterrestrial creatures could be capable of long-distance space travel? These are intrguing questions.
First let us consider the possiblility of the existence of extraterrestrial. civilizations similar in technological prowess to ours. What kind of creatures could have advanced to this level of technology? Have they tried to contact us?
As we ponder the various forms that intelligent life can take in the universe, our own situation serves as a prime example of what is possible, and most probable. Starting with the basics, since carbon and water seem to be abundant throughout the universe, and chemically are suitable as foundational to life, we can surmise that most probably such extraterrestrials will be carbon based, and utilize oxygen and water as do we. As to their form, because advanced technology relies on the basics of chemical reactions in "air", and the use of dexterous extremities by a being with a developed "brain", and since life seems to evolve first in aqueous environments, we can guess that whatever their final form, they came from a watery environment and later inhabited a terrestrial one. Is it feasible for primarily aqueous creatures to reach our evel of technology? Yes, but with great difficulty.
Intelligent extraterrestrials need not seem simian, though, as other life forms can exhibit dexterity. Earthly examples of detrous non-simians include racoons, who are notoriously skillfull in their dexterity. They can climb, hunt, fish and fetch. The cephalopods are another example of non-simian dexterity. Cuttlefish and octopus are not even vertebrates, and yet exhibit keen hunting skills, communication, dexterity, and use tools. Not only are they the most intelligent invertebrates, but they are truly among the most intelligent creatures on Earth.. Could similar invertebrates have dveloped our level of intelligence on other planets?
It is intriguing to attempt to ascertain the exact type of alien creatures of the movie Arrival, but the cephalopod-like, seven-limbed aliens captured our attention.
We might imagine what will become of intelligent Earthly sea creatures if they returned to land and developed dextrous appendages to conjur images of intelligent creatures on other worlds. Think of land-evolved killer whales (orca), dolphins, sea otters, or octupus. What might they become?
Evolution experts beileve that orcas and dolphins were originally land animals that recently evolved to live in the water full time. One of the new adaptations to aquatic life was that their appendages evolved into webbed swimming gear. Might they evolve back into arms, legs, fingers and toes if they returned to living on terra firma? It is also believed that fish slowly developed terrestrial adaptations over time on our planet to evolve into land animals. Did intelligent sea creatures on other worlds evolve into terrestrial creatures to further their intellectual development and enhance their ability to use fire and tools? Or perhaps they remained bound to their seas but built underwater refuges filled with air and in those spaces developed the use of fire and combustion? Or did they learn to harness the energy of the sea to propel their technological development? The movie "Avatar, The Way of Water" provides us with some interesting perspectives on this topic.
Perhaps a creature like them on a distant world has evolved the technology to attempt contacting us?
Have we been contacted by extraterrestrials? The most promising potential contact we have had occured in 1977 and is known as the Wow! Signal. Where did the Wow! Signal come from? Possibly a Sun-like star known as 2MASS 19281982- 2640123. This star was detected within the zone of space from which the signal emanated.
Prior to this correlation, little was known of this seemingly insignificant star, except that it is so much like our own sun that it has been called a sister star to our sun. The potential source of the famous signal lies 1800 light years from us. Could it be that 1845 years ago, beings from that solar system were sending strong radio beams towards their sister star and others that they thought might harbor intelligent life? Are they patiently awaiting a response?
The Breakthrough Listen project is studying the region of this star for signs of technological emanations. What are the chances that we can detect the random electromagnetic emanations form a distant planet that is not directing high powered signals to us on purpose? Scholars have made estimations.
One way to contemplate this problem is to estimate the distance from which our Earth's currrent random emanations (radio, tv, radar etc) can be detected by extraterrestrials. How far away from us would we be detectable by a civilization with our current methods of detection? Experts give that distance as approximately five parsecs. One parsec equals 3.26 light years, so that we may currently be detectable out to a distance of about 16.3 light years.
How many stars are there within that distance from us?
Experts estimate that there are about forty stars within that distance. The Trappist-1 system, at about 40 ly from Earth, is thought to have as many as seven planets within the habitable zone of that star.
SETI engages in ever more intensive searches for electromagnetic signals from advanced extraterrestrial civilizations, such as the COSMIC program.
The COSMIC program employs a huge array of radio astronomy assets in the search. "COSMIC is a collaboration between the SETI Institute and the National Radio Astronomy Observatory (NRAO), which operates the VLA, to bring a state-of-the-art search for extraterrestrial intelligence to the VLA for the first time. As the VLA conducts observations, COSMIC will enable SETI Institute scientists to access that data to analyze for evidence of technosignatures, signs of technology not caused by natural phenomena."
Extraordinary Means of Communication
As our search for interstellar signals from alien civilizations fails, year after year, to find any such communications, scholars are speculating as to the reasons why this may be so.
Are we failing to recognize communications from alien civilizations because we have not yet discovered the modes of communication used by advanced extraterrestrials? Perhaps this is why we have not "heard" from anyone yet.
So far we have been searching the modes of communication of which we are aware. These include radio and laser. But what if the best methods of extremely long distance communication are ones we hae yet to discover? Methods in which the communications travel faster than the speed of light...perhaps even instantaneously?
How could communications faster than the speed of light occur? A few such scenarios have been proposed.
The speed at which light travels in a vacuum is the highest speed possible in our physical universe, as far as we know. Such "superluminal communication" is currently thought impossible. However, some wonder if quantum entanglement can allow for superluminal communications. Thus far, no one has found a way to use quantum entanglement for such rapid communications.
What are the possible habitats of the aliens?
If we were to be contacted, what type of environment will be the most likely living spot for the extraterrestrials? Or maight they transmit from somewhere that is not where they live? Most seem to conjecture a planetary body to be the most likely place from which extraterrestrials will try to reach out to others. Others deem moons likely candidates.
But what of the possibility of huge alien-crafted space environments, suited to their physiology? Or as platforms on which they do not reside, but from which they choose to send out messages? If this is a real possibility, then we might want to look at communicative emanations from areas of open space rather than from planets and moons. Perhaps we should even consider habitable or technologically convenient environs in interstellar space as places to monitor for communication attempts.
Extraterrestrials might use safe, gravitationally stable regions of space to live, or to place platforms that can send and receive interstellar messages. These areas of open, unoccupied space would tend to be free of dust clouds and debris. They might be in areas of space that have net-zero graviatational pull, so as to minimize the need for constant realignment of their position. It is also plausible that such areas for the placement of communication platforms will tend to be close enough to their home world to make their access to it convenient. However, the platforms might also be far enough away from the home world to protect them from easy discovery by malign aliens who might trace their communications back to its source.