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    Beware of Promises of New Earths

    I had a secret, and it was pretty Earth-shattering.

    A few months before tomorrow’s NASA planned annoucement about an intriguing planetary system, a friend passed along this rumor: NASA’s Kepler space telescope had discovered a host of Earth-like planets out in a small slice of the universe.

    If you have an active imagination, “Earth-like” and “planet” are words that immediately conjure up images of water, place to live, of other civilizations even. From an astronomy perspective, the sensation of discovering another planet like our own might feel like being at a strange party, without any friends, surrounded by icy, hostile types, or fat, gaseous ones, when suddenly, someone you recognize — deeply recognize — walks into the room. It would rock your world.

    I sat on this news not just because it wasn’t official (blabbering before data is published is a big no-no in science writing) but for the same reason that Kepler’s astronomer caretakers announced they would be staying mum, because further analysis needed to be done. Although early findings were in, the Kepler team decided they would keep quiet until next February, by which time they would have made more sense of the data.

    To confirm what kind of planets had been found would require the help of other telescopes on Earth. And given the importance of discovering other Earths, the investigators wanted to be sure they had really found some, not, say, just a binary star.

    But then, last month, the Internet blew up with news that we had found 140 “Earth-like” planets, which indicated there could be millions more where those came from. The “news” came courtesy of Dimitir Sasselov, one of Kepler’s co-investigators, during a TED talk in England. That is, an overseas lecture to an elite audience, broadcast on video to the public only weeks later.

    How to Talk About New Earths

    The talk wasn’t just premature, jumping the gun on Kepler’s potential findings: it was kinda wrong.

    Here’s why: “Earth like planet” is a very specific term, referring not to the climate of a planet, but merely to its size. And there’s literally a world of difference between a planet that is like Earth and a planet that’s the size of Earth. The Kepler telescope determines only an exoplanet’s size and, given more observing time, the distance from its star.

    “Kepler cannot tell whether [a candidate exoplanet] is Earth-like or not,” William Borucki, the lead investigator for Kepler, who wrote a heated little letter about this, told “‘Earth-like’ is a term common among astrophysicists, but it’s not appropriate for the public.”

    In other words, the planets Sasselov referred to aren’t necessarily places where we could live, but are merely, quite literally, the shadows of planets that are twice the size of Earth or smaller.

    Those shadows are registered on the face of stars; if Kepler spots a “transit” of a planet in front of the star it’s looking at (and that’s a big “if,” because planets won’t necessarily be orbiting their stars in Kepler’s field of vision), and if that planet is hard (as opposed to made up of gas) and if it is within the habitable distance from its star, and if it’s the right size, then Kepler has discovered a candidate planet.

    And Kepler has certainly found a host of Earth-sized planets. That’s amazing, but not really surprising, given the vast size of this universe, at least hundreds of billions of stars big.

    Come Back in Five Years

    But among those candidates, the number and kind of planets that Kepler has found that are very close to Earth-size – one and a half times the size of Earth and smaller – still remains very low. Those within the “habitable zone,” not too close to their suns? Zero. While Kepler will help us focus our search for planets that could harbor life, the telescope’s data alone won’t reveal if those candidates are covered in oceans or are just parched orbs of rock.

    “We like to err on the side of caution,” John Geary, one of the Kepler co-investigators based at Harvard, told me. “Too often people get carried away and announce things that don’t hold up in the end, and it gives everybody a black eye. Things like cold fusion had an enormous splash in all kinds of media several years ago. It’s never been shown to have actually occurred. For Kepler data, it just takes time to evaluate the raw data, to get processed data.”

    Exactly how long will it take to find an Earth analog? Because the best candidates for such planets are small and emit only a very faint signal, and typically require a sun like ours, much more investigation would need to be done, even if such a candidate were found. And none has been found yet.

    “But we fully expect to find one,” says Geary. “It’s a five or six year mission. It takes that many years to get enough signal. We cannot possibly see them in the first year.”

    Thinking about science

    I had to try hard not to be a little peeved at Sasselov. It’s not just because he ruined our wonderful little secret, or beat us journalists, and the rest of his (somewhat disapproving) colleagues, to it. (Still, shouldn’t this have been done right, with a big parade or fireworks or cake?)

    While those points are important, and related, his announcement raises another concern. It runs counter to the way that science – literally the gathering of knowledge – tends to work. With the potential for excitement over this “news,” comes not just the need to thoroughly analyze it, but it’s evil twin: the potential for widespread misinterpretation. The discovery of other Earths is sensational pop science gold, right up there with other hotly debated science topics, like cold fusion, the manufacture of synthetic DNA and, most famously, climate change.

    Even amidst its landmark discoveries, science doesn’t proceed by bold pronoucements, and doesn’t offer rock-hard knowledge: it offers the processes and models and theories that slowly transform the landscape. Sometimes those processes lead to developments that push things forward faster; sometimes there are watershed moments. But all along, our understanding evolves. Only rarely, if at all, does our knowledge get blown out of the water by a set of findings, and we shouldn’t let it just because thousands of blog posts suggest it should.

    That’s why in a follow-up post, Sasselov ate his words

    Two weeks ago, I gave a talk at TED Global 2010 which was very well received, but caused confusion…Earth-size and Earth-like are certainly not the same. Take the example of Venus, an Earth-size planet whose surface will melt lead. I understand that the term “Earth-like” was misleading to most of the media coverage. The Kepler Mission is designed to discover Earth-size planets but it has not yet discovered any; at this time we have found only planet candidates.

    Adding to the confusion, Sasselov acknowledged that in reproducing a figure from a Kepler paper he accidentally lumped the majority of candidate exoplanets into a size category he labeled “like Earth.” (See below.) But says Borucki, “there are no Earth-size planets in my figure.”

    Sasselov meant no harm by any of this. As a co-investigator, he (or one of his grad students) was familiar with the data that had been collected, but perhaps not so familiar with the plan for its release. He was certainly excited too, and who could fault him for that?

    But that he released some of Kepler’s findings at TED might highlight some of his motivations for talking – and the reasons for the Kepler team’s guardedness over it’s data. It’s hard to overstate the significance and enormity of discovering a planet a lot like ours. Sasselov has, intentionally or not, linked himself with that mission more publically than any other investigator on the Kepler project. Imagine how many more scientists who sit on prestigious science prize committees – now know his name.

    Attempts to clarify the situation aside, the cat’s out of the bag. Developments like this are probably going to spark another round of discussion about extraterrestrials and the habitation of other worlds. Just take a peek at the trove of user comments on TED’s site. It’s a testament to how much a single announcement can activate the public’s wonder around space and science, a wonder that’s persisted for thousands of years.

    But – to be scientific about this – at what cost? What if that discussion misses the point about the actual findings, the subtlety of the data, and the complexity of the search? What if the excitement over some initial data distracts from the really exciting stories – of how these planets are being discovered, what their discovery might mean, and how we’ll keep making more discoveries? As an astronomer interested in atmospheres and biology (he heads the Origin of Life initiative at Harvard) his pursuits depends upon careful development on top of the work of planetary science, Sasselov knows the importance of integrating findings like Kepler’s into a larger field of knowledge.

    What would Kepler say?

    But what if Powerpoints and TED lectures don’t help us think better about this stuff? What if those big announcements aren’t properly contextualized? In our excitement for the rare planets, we might miss the whole sky.

    And if excited announcements turn out to be wrong, or just rumors (remember when we discovered the Higgs particle last month?), will science start to tire out the public rather than excite it? That’s dangerous to say the least, considering that when it’s inconvenient, science gets ignored. Finding planets may be exhilarating to nearly everyone, global warming not so much.

    Rather than searching for facts, can we have a way of talking about science in public that keeps imaginations open and curious, in a way that pushes forward thinking and research? Can we have sensible discussion that is less inflected with political or ideological beliefs and more imbued with a sense of excitement or curiosity? The kind of science talk that leads us not to pronouncements, spread online through lecture videos or comments, but to the questions that push the conversation forward, the way science always has?

    The impulse to get excited about scientific “news” like this is kinda like the impulse to search for Earth-like planets to begin with: we yearn to learn about new worlds. But to send and receive the right signals, we need to turn down some of the noise.

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