Overbye’s teaching moment about scientific discovery and uncertainty

In my humble opinion (alright:  IMHO), the best science writing combines reporting on current advances in science — the knowledge or content — with insights into the process of science — how the new knowledge was acquired, and with what certainty.

Thus, I was delighted to read a recent article by Dennis Overbye in the New York Times about the kerfuffle over the claimed discovery of a so-called Goldilocks planet — aka, Gliese 581g — in the far-away Libra constellation (my favorite, astrologically).  The “g” planet would be of interest because the proposed orbit around Gliese 581 would be at a distance optimal for life as we know it.  However, as reported by Overbye, the discovery of the g planet announced by an American group in 2010, and reasserted with new data analyses just published, is still being contested by Swiss astronomers who do not think the data warrant addition of a 5th planet to the four that they originally discovered in 2007.  And a number of other astronomers, observing from the sidelines, agree, including a former student of the American group leader.  So, at this point, the existence of Gliese 581g is uncertain.  It is not settled knowledge.

As a biologist not particularly well versed in astronomy, I learned quite a bit from this article about the techniques of planetary discovery.  Overbye’s brief but specific reference to the use of spectrography, i.e., color measurement, on high-resolution telescopes in Chile and Hawaii, including Chile’s HARPS instrument, and a short, but detailed description of the “wobble method” used to detect “gravitational tugs” between a planet and its star, were just enough to guide a Google search for more information.  (A more casual reader might have been satisfied, indeed way satisfied.)  I eventually learned that the spectrographs used with the two telescopes in question — the HARPS in Chile and the HIRES at the Keck Observatory in Hawaii — both measure the radial velocity of the star using color (spectral) shifts known as the Doppler effect.  (At this point, I was in more familiar territory, as I knew something about the Doppler effect, which is commonly invoked in physiology to account for shifts in sound frequency by a passing siren, to explain bat and dolphin echolocation, and to measure blood flow using ultrasound.)

With these common techniques in hand, astronomers begin to collect data on these Doppler shifts.  Data collection takes a long time, often over many years, and is followed by extensive statistical analysis, based on certain assumptions about the data, such as the shape of the orbit (circular or elliptical) and other factors.  In the end, this gives the scientific team a basis for estimating the mass and orbital period (# of days per complete orbit) of a candidate planet believed to be “tugging” on its star during orbit, together with a level of confidence (so-called “false alarm probabilities“).

And that’s the rub:  Different teams use slightly different statistical approaches that involve different assumptions, and can lead to small differences in outcome that are then subject to different interpretations based on different confidence thresholds, but sometimes having huge consequences, like whether or not we say a new planet exists.  Overbye nicely captured the nuance of this back-and-forth scientific struggle, with quotes from various parties and observers that gave evidence of general collegiality, despite the contentiousness.  Clearly, though, this research sits at a point where there is no consensus and, hence, no advance in knowledge, at least none that is settled and reliable, beyond reasonable doubt.

I have to say, as a biological scientist, I found this all too familiar.  And it should be a theme familiar to anyone who has read previous posts over the short life of this blog.  Why were the physicists who were looking for the Higgs boson so hesitant in their statements this summer about the discovery of a Higgs-like particle?  And why did it take so many years to get to this point?  Well, because a lot is on the line — only a full understanding of the basis for our existence in the universe — and those folks wanted to get it right, with a solid consensus among experts, to the fullest level of certainty — no chance of false alarms.  On the other hand, look where we are with the nature-nurture debate and IQ.  The publisher of The American Conservative, who is scientifically trained, but not in the field of socioeconomics, analyzes somebody else’s socioeconomic data and comes to an entirely different interpretation.  Talk about lack of consensus.

Undoubtedly, this is frustrating to the non-scientist, who expects one truth to come out of each study that is publicized.  As an interested private citizen, it gets especially frustrating for me, too, when medical researchers can’t seem to make up their minds about what a drug does or how a disease is transmitted.  This is often information I could use.  Today.

But, uncertainty and doubt and lack of consensus are part of the process of doing science. The best strategy is simply to look for the level of certainty and consensus in any data set that interests you.  Don’t just act according to the 1st report you see.  Do some homework, and find out as much as you can about the phenomenon.

One should also expect that, even in a settled area of science, where there is consensus among credentialed experts (e.g., evolution, global warming, vaccines and autism), there may also be occasional challenges to that consensus.  Nothing is ever certain.  Nothing is ever truly proven in science.  While the challenges may sound reasonable, and they may come from folks you judge have authority, like a Nobel prize winner or a large foundation, treat them provisionally.  Look to see if a new consensus emerges over time.  As Carl Sagan said, paraphrasing Truzzi (noted by Ford and quoted by Overbye):  “Extraordinary claims require extraordinary evidence.”  Don’t give up on evolution just because a bunch of white guys in suits at a debate say, “I dunno.”

As for Gliese 581g, one comes away from this story not quite sure of the scientific advance to be claimed, perhaps hopeful for an emerging consensus in the not too distant future, but deeply enriched by Dennis Overbye in how science works.


About Tom Schoenfeld

I am an olfactory neurobiologist who practices his science at Fitchburg State University, Fitchburg, MA, in the Department of Biology and Chemistry. I have created "dissectingpublicscience.com" to help educate both my science students and the interested non-scientist about the process of science, by focusing discussions on how science is presented and misrepresented in the public media.
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