Matryoshka World

Friday, February 3, 2012

Fermi's Paradox, the Great Silence and the Great Filter

Recently, thanks in large part to the Kepler space telescope, new planets have been discovered outside of the solar system at an ever increasing rate. Currently, over 750 planets are known to exist outside of the solar system, and Kepler has identified many hundreds of other possible planets that have not been confirmed yet. Further, several planets have already been identified that could possibly support life, including one planet discovery announced yesterday.

It is now generally accepted that planets are plentiful throughout the galaxy and almost certainly throughout the observable universe. This discovery, along with other discoveries (for example the abundance of the materials necessary for life throughout the universe) have greatly increased the odds that life is common. Of course, it is still not completely understood exactly what triggered the first complex molecules to begin replicating and from there evolving, but life arose very soon after it first became possible for life to exist on earth, suggesting that perhaps the starting process was not an exceptionally improbable event, and would occur anywhere that the conditions are right.

This line of thinking leads inevitably to a quandary: if life is in fact common throughout the universe, where are they? Where are the alien visitors welcoming us to the neighborhood? This mystery is known as Fermi's Paradox. The lack of evidence of other intelligent life in the universe has also sometimes been referred to as the Great Silence. A comprehensive (and highly recommended) recent book on the subject by Paul Davies was titled The Eerie Silence. Regardless of what it is called, the lack of any evidence of alien intelligence is mystifying to many who believe all of the trends of discovery in science are moving in the direction of support for the concept that life should not be that uncommon.

But even if it is assumed that life is common, should we really consider it a great mystery we have not discovered life yet in the universe? Of course, before moving on to consider this question it must be acknowledged that there are some who claim earth is currently being visited, and numerous eye witness accounts have been offered supported by photos and videos of alien spacecraft. However, no evidence has been produced that from a scientific point of view would be considered to carry significant weight. Therefore, while such claims can be interesting, they do not constitute evidence of alien intelligence unless something more substantive develops from the supposed visitations. That returns us to the original questions: Where are they and is it a mystery that we haven't heard from anyone yet?

A Great Filter?

One consideration that has been raised is the possibility that despite the fact that planets and the ingredients for life appear to be plentiful throughout the universe, perhaps there is some filter process that keeps life from evolving into stable, advanced civilizations that then spread through the galaxy. Without such a filter, the aliens would surely be here (the argument goes), as once a civilization becomes space faring, it could colonize the galaxy within a relatively short period of time. This line of thinking is somewhat speculative, as will be addressed further below.

Assuming there were a filter, this could potentially have tremendous implications for our own future. There are two basic possibilities- one being that the filter was in our past, and we have already made it through, the other being that the filter lies waiting for us in our future. It is possible that there is some evolutionary step that is highly improbable, or perhaps the initial beginning of life is highly improbable, and we just happened to win the lottery. If this is the case, the filter is behind us and we may have little to worry about.

A far more disturbing possibility is that the filter is in front of us. If this is the case, perhaps every advanced civilization inevitably develops some type of technology that leads to certain and total destruction. Looking at our own future horizon genetic engineering, nanotechnology and artificial intelligence loom as potentially dangerous near term technologies, and there are certain to be many others. Maybe any sufficiently advanced civilization becomes powerful enough to destroy itself completely and this is never avoided. Out of concern of this possibility, some have suggested we should hope to not find any other life, particularly more advanced life, because this would mean the filter is ahead of us and our destruction is virtually assured.

It seems safe to say that the universe can be a fairly hostile place for complex life, and there are any number of things that may stop the advancement of life before it reaches the stage of an advanced civilization. In our own past it seems likely that asteroid impacts, climate changes, and other large scale disasters c
reated enormous extinctions of life on Earth. So there is no doubt that even if life is relatively commonplace, things would often happen to create setbacks, or even end it completely. Mars may end up being one example of many for this outcome.

However, as discussed below it is too early to know if we really need to evoke the concept of a Great Filter in more absolute terms given our current state of knowledge in order to explain our observations.

Our Exploration So Far

A common misconception is that we have searched
a significant chunk of our galaxy for extraterrestrial life, and have not found anything. In fact, the search has been very limited to date. We have just begun to discover planets around other stars in recent years, and we can only spot planets that our orbiting in a path between us and the host star. Also, very few stars have actually been searched for planets. Regardless, even the results we obtain from the systems we have checked for planets can not tell us much about intelligent life there. We can get some sense of whether any of the planets we see might be a potential candidate for life as we know it, but our detection abilities are very limited. These systems could have a Death Star from Stars Wars or other products of an advanced civilization and we would have no way of seeing it or knowing it with our present technology.

The search for radio transmissions from an alien civilization has been a little better but until very recently only a few thousand nearby stars had been searched thoroughly, and larger searches would look only within a very narrow frequency range. Technology is expanding the search, however, the case remains that a very, very small fraction of our galaxy has been searched for alien transmissions. It also is important to keep in mind that we will only detect any possible signals if an alien civilization is trying to communicate with us. If they don't care to talk to us it is unlikely we would hear their transmissions. For instance, any radio transmissions using compression algorithms or encryption would simply look like background noise to us.

So it is not at all clear that, even if the galaxy is teaming with life, that we would necessarily have looked enough to know about it yet. And of course we are making assumptions about alien intelligence that may be completely off. Maybe aliens have a far better technology to communicate with than radio transmission. That may be the equivalent to smoke signals to them. SETI has attempted to anticipate this and has considered other options, including looking for optical transmissions. However, the reality is we have no idea what a civilization 1 million or 100 million years advanced from us would use to communicate.

Considering how rapidly technology is evolving on our planet, it seems a futile effort to anticipate what an advanced civilization may send as a signal, or how they could be detected. Outside from confirming they are not engaged in mega-scale projects like building shells around stars or things of that nature, it is impossible to know even what we are supposed to be looking for in an attempt to discover if alien intelligence exists. Many suggest that if they were out there they would already be here. However, again, we would only know of them being here if they want us to know, and it seems plausible they would choose not to interfere with the development of life on earth. The universe is plenty big enough to allow an alien civilization to bypass a system that already has life, and our planet has had life for billions of years.

Of course, returning to the idea of the problem detecting a far advanced technology. They could be nearby and simply not be detectible to us due to the use of technology we can not even comprehend. Ultimately the problem is we simply do not have enough information, either in terms of the amount of the galaxy we have searched or in terms of even having an idea what we should be looking for, to be able to draw any vast conclusions from the apparent absence of clear evidence of extraterrestrial intelligence in our galaxy.


Fermi's Paradox simply highlights our bias to expect other life to be like us, and our lack of understanding of how advanced intelligent life would likely develop. We should not expect to detect other life similar to our own as our current level of technology will be very short lived, and without knowing what comes after we do not know what to look for. We can not form conclusions about the prevalence of alien life based on our current knowledge and what some consider an absence of evidence of alien life.

1 comment:

Randy Knudson said...

great article! If you had a facebook share button, I would share it.