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. Schedule 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 did not. The argument typically proceeds as follows:

If we were to discover life (simple or complex) on Mars, then this would indicate that abiogenesis (life from non-life) is not at all uncommon. After all, it was found twice in our own solar system, our very back yard. Thus, there are likely an infinite number of other sapient civilizations across the cosmos.

If we assume that all intelligent life values space exploration and colonization like our own, then one or more of these other sapient civilizations must have reached a point in the last 10+ billion years in which inter-galaxy travel was possible and thus made SETI a priority as well. At the rate that present technology advances, most experts believe inter-galaxy travel will be easily possible within the next one million years.

Therefore since we have had no contact from other planets beyond our own, if we were to discover the past existence of life on Mars or on other nearby planets, there is a good chance the “Great Filter” is ahead of us. That is, some existential disaster must occur which filters a planet of all life forms once technological advancements reach intergalactic travel capability. 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 sapient life may have escaped our kind. For example, one such Filter could be the evolution from simple to complex life. Perhaps other life forms never reached complex life and sexual reproduction and thus ceased to exist after some time, something with which our world triumphed.

Other counterarguments suggest there is no Great Filter. The reason we’ve not been contacted by other life is that there has been no intergalactic travel, for one reason or another. 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. These arguments suggest a District 9-esque experience might be forthcoming.

The reality is that we have not seen any signs whatsoever of extraterrestrial life. The missions to Mars failed to discover anything remotely 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 really 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.

Most cosmologists would agree that our present knowledge of the cosmos is as incomprehensibly small as the universe is large. Thus, I don’t see how the probability of extraterrestrial life can weigh more heavily in either direction. There may be carbon-based or other sustained life elsewhere in the exponentially expansive universe, but there just as easily might not be. It’s difficult to say which reality would be more comforting, however. If we are alone, then our future is entirely without precedence, with no model civilization to learn from or, more importantly, 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 future chances 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