David Aguilar/Harvard-Smithsonian Center for Astrophysics/NASA
An illustration shows how the planet Kepler-36c might look from the surface of the neighboring Kepler-36b.
An illustration shows how the planet Kepler-36c might look from the surface of the neighboring Kepler-36b. David Aguilar/Harvard-Smithsonian Center for Astrophysics/NASA
A widespread critique of science is that it tells us that the more we know, the more insignificant we are. It's the famous after-Copernicus blues: everything went downhill ever since Earth was moved from the center of the cosmos. Since then, the Sun was pushed out from the center too, our Milky Way galaxy is but one among hundreds of billions of others in an expanding Universe. Even the atoms we are made of are less that 5 percent of the total stuff out there.
This is the cause of much angst, as these findings relate to the perennial question as to why we are here or, less cliché-like, why we matter. Of course, you can say that we matter because of our social and family ties, because we care and are cared for, because we are active and productive people. Fair enough. But I'm talking here about a more macrocosmic perspective, of our place in a vast and uncaring Universe.
Could we really be that insignificant in the big scheme of things?
Part of the answer depends on our planet and how unique it is. Another part depends on who we are and if there are similar forms of life out there. The Copernican take, as I see it, would say that since the laws of physics and chemistry are the same across the observable Universe, and since there are a multitude of planets and moons out there, it follows that life should be ubiquitous and yes, that we should be typical — read: insignificant — manifestations of how matter gathers together into living things.
So, to address the first part of the question we must find out how unique the Earth is. We then should figure out how unique life, and humans, are. Fortunately, thanks to NASA's Kepler mission, we are making huge progress in the first part of the answer. A key finding is that the majority of stars (around 70 percent) have at least one planet orbiting around them. Based on the data so far (2,740 planet candidates and 115 confirmations), Kepler scientists estimate that some 17 percent of these are Earth-size, meaning with similar mass and rocky composition as the Earth, and possibly close enough to their parent star that water, if present, could be in its liquid state.
More good news arrived on this front earlier this month as NASA authorized the construction of Keplers' successor, TESS (for Transit Exoplanet Survey Satellite). With launch scheduled for 2017, TESS will survey a much wider area of the sky than Kepler, while focusing mostly on stars that are closer. This way, it will use spectroscopy to resolve at least part of the atmospheric composition of the exoplanets. The goal is to find telling signs of life-related compounds such as ozone, water, carbon dioxide and, if we're really lucky, even chlorophyll. Successful detection would be very exciting, as it'd point to what optimists expect, a few fairly close Earth-like planets with metabolizing beings.
But from Earth-like to life-harboring is a very big jump. The large-number-of-worlds hypothesis, plus the amazing versatility of earthly extremophiles, indicate that we have every reason to be confident that simple life exists elsewhere. After all, it showed up within a few hundred million years here and the Universe has many old stellar systems. Even if there are extremely complex and not-understood steps from non-life to life, it would indeed be very bizarre if the recipe worked only here. Plus, there are presumably many different recipes for life, each deeply attuned to its host planet or moon.
However, as we follow the increasing complexity of life on Earth and the many obstacles that had to be overcome to go from simple-celled to complex single-celled, then to multi-celled and complex multi-celled, and then on to intelligent multi-celled life, the odds drop very fast.
Granted, no one knows how to estimate such odds. But, from an evolutionary perspective, life is not interested in getting complicated — only in being. So, if things are OK and no environmental pressure exists, life forms will go on happily without any great change; mutations occur always, of course, but they are mostly deadly or of little help. Case in point, the dinosaurs were here for 150 million years and changed a great deal, as we see in natural history museums. But in all that time they didn't become intelligent or, if they did, certainly not enough to predict their doom and do something about it. (We can barely do that now.)
But when the environment changes drastically, life changes with it. The history of life on Earth and Earth's life history are deeply enmeshed with one another. Play the movie a bit differently and the outcome changes.
We are a one-of-a-kind experiment in evolution.
Which brings us to the second part of the answer. What we know of life here, added to searches in our solar neighborhood, added to the lack of convincing evidence of contact with extraterrestrial intelligence, added to the extreme interstellar distances, lead to a profound reexamination of the Copernican hypothesis: we should be calling our era the humancentric age, a time when science is teaching us that we matter because we are rare.
In a complete reversal of the "we are cosmically insignificant" discourse, the more we learn about the Universe, the more precious we — and all of life — become.
I'd like to dedicate this essay to the victims of the Boston Marathon bombings.
You can keep up with more of what Marcelo is thinking on Facebook and Twitter: @mgleiser