Sunday, August 22, 2010

Will we ever meet aliens? (part 2)

Intelligent alien life

In the last post I talked about primitive alien life and how it may turn out to be abundant throughout the Universe. But what about intelligent alien life? Again we are dealing with 2 different questions: 'what are the odds of intelligent life evolving someplace other than Earth?' and 'what are the odds of us encountering intelligent extraterrestrials?'.
To answer the first question we must, yet again, look at our own planet, and study the origin of intelligent life here. As mentioned in part 1, life exists on Earth for 3.5 billion years, but humans have been around for only a fraction of that time (200,000 years). From this statement alone we can see that even on a planet teaming with a large variety of organisms the emergence of sentience and intelligence is quite rare.
The conditions that led to the existence of humans are numerous, and if just one of these conditions were different we wouldn't have existed. Let's consider an example: for over 160 million years, dinosaurs were the dominant species on the planet. Had it not been for the cataclysm that wiped them out 65 million years ago it's entirely possible that mammals would have never taken over.
We know of no other species from Earth's history that achieved our level of intelligence. This also enforces the idea that it is a rare event, one might even call it an accident. Unfortunately this means that it isn't very likely to happen often.
In 1961, a scientist named Frank Drake, formulated an equation called 'the Drake equation' to estimate the number of potential extraterrestrial civilizations. The logic behind the equation is simple: life appears in solar systems (so we need to know the rate of star formation in our galaxy), not just any solar systems but the ones that have planets (fraction of planetary systems), out of these life can only appear on certain planets with the right conditions (number of potentially habitable planets), and will appear only on some of these planets (fraction of the previous on which life actually appears), and some lifeforms will achieve sentience and intelligence (fraction of the previous on which intelligent life develops), and some will evolve and create technology that is detectable from space (fraction of the previous which creates technology) but they will exist only for a certain amount of time (length of time a civilization is detectable). Sadly most of the terms in the equation are unknown and scientists can only estimate or guess their possible values. For this reason the result can vary a lot and until we actually meet another civilization or start exploring other solar systems we won't be able to make more realistic estimates.
Still, we could ask ourselves: why hasn't anyone contacted us? Why have we seen no signs of other intelligent beings out there?
It has been estimated that an advanced civilization could expand throughout the entire galaxy in a timescale on the order of millions of years. Considering that our galaxy has been around for about 13 billion years and our own planet has been present only the past 4.5 billion years there has been enough time for another civilization to conquer the galaxy. And yet, we see no signs of this whatsoever. You could say that maybe there are old civilizations out there but they just don't want to expand. This is highly unlikely since expansion is an imperative for any species for 2 very important reasons:
- first of all a condition necessary for the continued existence of a species is reproduction. As the civilization's population grows in number it will need more and more space
- any advanced civilization requires resources and energy and once it consumes the ones which exist in its local environment it will need to expand in search of other resources
This is actually quite concerning since it could mean that if aliens come here they might try to colonize our planet and take our solar system's resources. And since we would try to oppose them they would most likely destroy us. Well-known theoretical physicist Stephen Hawking has expressed his concern on this matter, saying "If aliens visit us, the outcome would be much as when Columbus landed in America, which didn't turn out well for the Native Americans".
For now we have nothing to worry about. All the techniques we've employed to find signs of extraterrestrial intelligence have turned up nothing. This is referred to as 'the Fermi paradox', the contradiction between the theoretical high probability of the existence of alien civilizations and the lack of evidence. Although interstellar travel is very difficult (currently our fastest probes would still take thousands of years to reach the nearest star) there is still the question of why we haven't received any radio signals. There are many possible answers: maybe we haven't been listening at the right time and now broadcasting civilizations are using some other means of communication (or have ceased broadcasting in outer space), perhaps the distances are so great the signals are too weak for us, maybe we're not listening on the right frequencies, compressed data streams are impossible to distinguish from white noise, aliens could be using modulation techniques unknown to us etc.
Detecting extraterrestrial civilizations may prove so difficult it could not happen for another 1000 years. We currently employ the SETI (Search for Extraterrestrial Intelligence) program to detect radio signals which could be of alien origin. While it's a good idea, it has had little success (apart from the controversial 'Wow signal') and sadly it's possible that we will never detect any such signals. Our own planet is becoming more and more 'quiet'. With the advancement of communication technology, low-power directional-guided transmission is expanding, meaning less 'leakage' of radio signals into space thus making it harder for us to be discovered.
Of course, there are other search methods such as looking for Dyson spheres. Physicist Freeman Dyson hypothesized that a highly advanced civilization would try to harness most of the power radiated by a star and therefore construct a giant sphere around it. The sphere could be formed out of a swarm of satellites. In order to locate such a mega-structure, scientists have restricted their search to Sun-like stars and assumed that the satellites would be constructed out of heavy elements. If this is the case, it has been calculated that the sphere would reradiate energy absorbed from the star in the infrared part of the electromagnetic spectrum. Therefore SETI is searching for 'infrared heavy' spectra from Sun-like stars. Although some candidates were found, they could all be explained as natural phenomena.
New Scientist published an article once in which it talked about how the IceCube Neutrino Observatory may be able to detect neutrino emissions from alien nuclear reactors. Personally I think it's more likely to find a Dyson sphere.
As we can see, all attempts at detecting intelligent aliens have focused on finding civilizations more advanced than us. It's entirely possible that we are the most advanced species in our galaxy or that we are the only intelligent species. But, as mentioned in the movie Contact, if we are alone it would be a giant waste of space.
What would happen if we did actually make contact with an alien civilization or they came to visit us?
Our society would never be the same. It would probably be the single most important event in human history, affecting all aspects of our culture. It would stir a mixed reaction from the population, as many people would be extremely happy and many would be terrified. Astronomer Carl Sagan believed that regardless of the aliens' intent, the knowledge of their existence would unite the nations of the world, as they would realize that their internal conflicts are insignificant compared to the challenges of first contact. Assuming they're not hostile, one of these challenges would be communication. Unless they have observed us enough to decipher one of our languages, communication will probably be based on mathematics, something which is truly universal. All messages sent intentionally into space to be discovered by advanced civilizations have taken on a mathematical form relating to base 2 arithmetic, prime numbers and universal constants.
After we have established a means of communication we would need to carefully negotiate with the aliens, something which will be most difficult considering we would know nothing about their culture. This process must be handled with great care, people would have to cooperate and agree on what decisions to take in order to act in the benefit of all mankind. Our initial fear must not determine us to act irresponsibly but we must also be vigilant and make sure the aliens aren't harboring evil intentions.
All in all, first contact could prove to be humanity's greatest challenge, although it does depend on when it happens. Many believe we are unprepared for such an event until we solve the major problems we have here on Earth. I believe we are unprepared for contact with an advanced space-faring civilization until we ourselves develop the means for interstellar travel. As it stands, we are fragile, our existence is tied to this planet and this solar system and we can't control either of them. If we could travel to other planets and other stars our chances of survival, even in the face of an advanced hostile alien species, would be greatly increased. It could even mean that we might be the advanced civilization that initiates first contact by travelling to an inhabited alien solar system, in which case things will go along a lot easier for us.

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