Thursday, April 7, 2011
An Awful Waste of Space
Remember these lines from the movie, Contact?
Eleanor Arroway (as a young girl): "Dad, do you think there's people on other planets?"
Ted Arroway (Ellie's dad): "Don't know, Sparks. But I guess I'd say if it is just us... seems like an awful waste of space."
The idea is that the Universe holds many worlds that support life, including intelligent beings. Carl Sagan, of course, was the scientist and science communicator extraordinaire who promoted this message. The concept is sometimes called the "principle of mediocrity", i.e., that Earth is a common rocky planet in a typical solar system, positioned in a typical galaxy...hence, there are likely many other such planets in many galaxies scattered throughout the Universe. The SETI (Search for Extraterrestrial Intelligence) program featured in the movie Contact exists based on the assumption that someone is out there listening. Of course, this message resonates with the UFO and alien abductee crowd (who never seem to question the wisdom of aliens who return these witnesses to Earth after their "physical exams"....and other illogical alien behavior).
I think something like 50% of Americans believe we have already been visited by aliens, despite the absence of a single piece of evidence. A corollary belief is that when we finally deplete the resources on Earth, we will simply move to some other Earth-like planet...again, despite there being no evidence that such a planet exists. Hollywood (and science fiction) has contributed to these beliefs. Recent films such as Avatar create imaginary worlds so realistic that it's hard for some young viewers to separate fantasy from reality. The idea that there are many civilizations out there in the Universe has become ingrained in our culture.
In this post, I'd like to explore these ideas from the standpoint of how it influences our decisions about protecting the Earth and its resources. In particular, are there other viewpoints that would influence people to be more appreciative of what we have on our little planet.
In fact, there is an opposing hypothesis: the "rare earth hypothesis", which states the alternative that Earth is instead a rare anomaly in the Universe. I've just finished reading "Rare Earth: Why Complex Life Is Uncommon in the Universe" (2000) by Ward and Brownlee. It's been around for a while, but I had never read it. The authors argue that the emergence of complex life, particularly sentient life, has a low probability due to the combination of astrophysical, geological, and evolutionary events required to facilitate it. Obviously, that rare combination can occur...here we are. The point is that life on Earth arose from a series of serendipitous events, without which, complex life would not have evolved or would have been extinguished prematurely (the probability of worlds with microbial-level life is higher).
There are convincing arguments to support both hypotheses. You can read Rare Earth or get the Cliffs Notes version on Wikipedia. (For another viewpoint, see What Does a Martian Look Like? The Science of Extraterrestrial Life).
However, what catches my attention about the rare earth hypothesis is the notion that life can be easily snuffed out by any one of a variety of cosmic occurrences. The geologic record documents at least 5 major events in the Earth's past in which mass extinctions have taken place. Some scientists estimate that 99% of species that once existed are now extinct. Some extinctions are attributed to cosmic collisions; others to huge climate swings. You see where I'm going with this...
At this point in time, we know only one planet that can support life--Earth. There may be others out there, but no evidence so far...and even if there are, we don't have the technology to reach them in the event Earth becomes uninhabitable. We know that mass extinctions are part of Earth's history and that some were caused by climate extremes (Snowball Earth, Runaway Greenhouse). We also know that human activities are altering the Earth's atmosphere and biosphere.
I'm sure that Sagan, in proposing the large estimate of habitable planets, was thinking mostly of supporting space exploration and astrobiology...not about the possible effect such a belief might have on how we view Earth and its resources. Yet here we are facing some serious questions about climate change and other issues.
Hollywood movies typically have happy endings with groups of humans surviving apocalyptic events in subterranean shelters or some other ark-like system (Deep Impact, 2012), humans colonizing other planetary systems (Avatar), or more advanced alien civilizations sending blueprints for transport of humans across the Universe (Contact). These are entertaining stories that convey a compelling message about human resilience and persistence. We naturally identify with the survivors, not those unfortunate people who succumb to the meteor impact. Government plans for response to such events also send the message that these catastrophes are survivable. However, one only needs to consider how we handled lesser events (Hurricane Katrina, the Gulf oil spill, Japan tsunami) to see the reality that our current abilities are insufficient to meet a global-level disaster.
Are there people on other planets? Don't know. But I guess I'd say if it is just us... seems like we should treat our planet (and each other) better.
Image Credits: Film clip (introductory sequence) and modified stills from the movie, Contact (Warner Bros.)