Are We Alone?

Orion Nebula (Messier 42)


With all the media attention and controversy surrounding the putative “discovery” of superluminal neutrinos, the search for extraterrestrial intelligence (SETI) has received increased attention. If faster-than-light (FTL) travel is able to be independently demonstrated, this would render Einstein’s theory of special relativity incomplete and open up an unimaginable number of possibilities for cosmological discovery. A revisitation of Nick Bostrom’s classic piece — Where Are They? — seems appropriate. In it, N. Bostrom philosophizes about the fatalistic implications of discovering life, or evidence of past life, on Mars or other relatively close-proximity planets.

On August 4, 2007, the NASA-sponsored Phoenix space probe was launched for a final mission to Mars, our nearest neighbor in the solar system. After the Mars rover discovered water on the planet’s surface in 2004, speculation increased regarding the existence of life at some point in Mars’ deep history. Scheduled to arrive in May 2008, the goal of the Phoenix endeavor was to find evidence of microbial life or other elements and characteristics that could support carbon-based life forms.


NASA Rover

Image courtesy of NASA


Amid the excitement and enthusiasm for this mission at the time, there were others who engaged (and continue to engage) the more ominous implications of discovering that life once existed, but now does not. The argument typically proceeds in the following fashion: If we were to discover life, simple or complex, on Mars, this would suggest that abiogenesis (life from non-life) is not at all uncommon. After all, it was found twice in our own backyard, one system amid billions of others. This points to the likelihood of an infinite number of other sapient civilizations dotting the cosmos.

If we assume that intelligent life will generally value space exploration and colonization, some percentage of these other civilizations must have both achieved intergalactic travel at some stage in their timeline and and — as we have — made SETI a priority. Perhaps it takes on average one million years for advanced civilizations to acquire the knowledge and technological wherewithal for such travel.

However, a problem arises herein that isn’t immediately obvious. Since we have had no contact from other planets beyond our own, the discovery of past existence of life on Mars or other nearby planets increases the chance the “Great Filter” is ahead of us. That is to say, some existential disaster must occur which filters a planet of all life forms once technological advancements reach intergalactic travel capacity. The circumstances such an advancement engenders must be incompatible with the perpetuation of life as we know it.

There are, of course, several counterarguments to this theory, namely that the Great Filter could be behind us. The catalyst for the extinction of advanced life may have escaped our kind. For example, one such Filter could be the evolution from simple to complex life. Perhaps it is exceedingly rare for organic forms to reach the complexity observed on Earth, or that sexual reproduction ceased to exist after some time, or any number of other paradigmatic leaps as have unfolded here.

Other counterpoints suggest there is no Great Filter at all. That the reason we’ve not been contacted by other life is that there has been no intergalactic travel. Maybe other life forms are isolationist; intergalactic exploration is economically prohibitive; other life forms’ methods of communication lay beyond the reach of our current capacity for detection; or perhaps there is life out there, but the distance between our worlds is so vast that we have simply not been contacted yet. In the latter case, a District 9-esque scenario might be forthcoming.

The reality is that we have yet to see any signs whatsoever of extraterrestrial life. The missions to Mars failed to discover anything reminiscent of microbial or other life. This could mean that we are in fact alone and thus have no reference to account for our future. Or it could just as easily mean that the Great Filter extinction event removes every trace of life, rendering us incapable of its detection. Regardless, whatever probabilities that are thrown around regarding the existence of life beyond the Earth’s surface are ultimately moot. We have no apprehension of how probable or improbable abiogenesis is, nor of the evolutionary stages on both sides of it. We are only able to assess the probability because we exist to comment. We are able to engage these questions because it could not be any other way — otherwise known as the anthropic principle.

Our present knowledge of the cosmos is as incomprehensibly small as the universe is large. Thus, it remains unclear how the probability of extraterrestrial life can weigh more heavily in either direction. There may be carbon-based or other sustained life forms elsewhere in our expanding universe, but there just as easily might not be. It’s difficult to say which reality would be more comforting, moreover. If we are alone, then our future is entirely without precedent, with no model civilization to learn from that we might avoid its mistakes. If we are not alone, then the “others” might not be so welcoming upon first contact. Or, as the Great Filter theory posits, the easier it was for life to evolve to our stage, the bleaker our prospects probably are.

Bostrom closes this way:

“So this is why I’m hoping that our space probes will discover dead rocks and lifeless sands on Mars, on Jupiter’s moon Europa, and everywhere else our astronomers look. It would keep alive the hope of a great future for humanity. In the absence of any evidence, I conclude that the silence of the night sky is golden, and that in the search for extraterrestrial life, no news is good news.”


External Link: Where Are They?

Feature image: “Orion Nebula in the Infrared” by user Chris