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Why Does Science Keep Changing Its Mind?

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An excellent entry has been posted at NPR's "sciency blog". "The Triceratops Panic: Why Does Science Keep Changing Its Mind?" is a look at how science changes with the time and how we react to these changes. The basic notion can be applied to epsilon Aurigae too.

It's been almost 200 years since the first publication that described the eclipse. And only just now, thanks largely to Brian and Dr. Bob's work, are we getting an idea of what is really happening. And their work would never have been possible without the support for citizen scientists monitoring the star over time and giving them the data needed to propose a model, which they later tested with interferometry.

Read Brian's literature reviews on the history of epsilon Aurigae and you'll see how our theories changed over time. Most of these changes were due to new data acquired thanks to advances in technology. For example, spectrographs provided the first clue that the star was a supergiant. Later, better photometric observations in the 1950's gave rise to the concept of a companion star within a disk. The 1981-83 photometry led to a theory of a Saturnian ring-like structure around epsilon Aurigae. Observations in this current campaign don't support that theory. So it has to be discarded. That's science. 

So where is all the screaming? Since epsilon Aurigae is not taught in school or mentioned in mass media, no one has a personal connection to it. I agree with everything in Robert Krulwich's blog, which is one of the best I've read this year on any topic - science or not (my personal blog reading tends to focus on sports, science and technology - I used to do politics too but gave it up in favor of staying sane). But I think there is something to add about why people are so attached to their scientific knowledge. It's not only because they know so little of it, as he attests, but also because they attribute what they know to specific memories in life.

Science is a little like music in that way. One of the great things about music is how hearing a favorite tune can bring back memories of the first time you heard it (in some people it can be strong enough to evoke memories of smell, taste, etc.). For example, many people associate their knowledge of Pluto as a planet with their first reading of books about the solar system. Or a favorite poster that hung in their wall or classroom. The same goes for the dinosaurs in Krulwich's blog.

Me, I have a strong memory of reading Astronomy magazine on our couch as my mother read her own books on science. In particular, I remember drooling over the Meade LX-series telescopes in the ads. Decades later, I now know that Meade has a terrible reputation for quality in the amateur community. I have owned two LX-200's in the last decade and have mixed feelings about the quality. But I still have an overall positive feeling towards them and get emotional when they are trashed online because I still remember how sexy they looked in those  advertisements. Effective marketing can cast a long shadow.

So what are some scientific ideas/concepts/theories that you hated to let go over the years?

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Hi Aaron "The 1981-83 photometry led to a theory of a Saturnian ring-like structure around epsilon Aurigae. Observations in this current campaign don't support that theory. So it has to be discarded. That's science." What current observations rule out the possibility of ring structure within the disc? Currently unexplained variations during ingress inthe density of neutral potassium surrounding the disc as measured spectroscopically may be due to some non uniformity within the disc. http://arxiv.org/abs/1003.3617 Robin


Hi Robin, I bet he is alluding to the light curve (i.e. Ferluga), rather than the spectroscopic information from this eclipse. If you want to write something up to post here on CSky about your spectroscopic work I'll be happy to promote it to the front page. Brian


"What current observations rule out the possibility of ring structure within the disc? " IIRC the mid-eclipse brightening was predicted by the ring theory and it was not detected in this eclipse. Thus the original theory as outlined in the paper doesn't match current observations. Even if you do have spectroscopic evidence, the predicted light curve evidence isn't there so the theory will need to be updated/changed/replaced/use-your-word-of-choice. That goes into the point of the original blog post: it can be hard to give up theories one has a personal attachment with. But sometimes science requires it. Null results are just as important as they constrain other theories. As Brian said, if you have data that supports the existence of Ferluga's rings, please let us know! Your ArXiv document has many predictions in it for events that have recently passed. How are they holding up so far?

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"Absence of evidence is not evidence of absence" Ferluga postulated a central opening and a ring structure to explain the shape of the light curve including the unexpected shape of the transition from ingress to totality, the flat bottom shaoe of the curveand the mid eclipse brightenning. The mideclipse brightening is absent in this eclipse at least and the shape of the light curve can probably be explained by the specific geometry ofthe disc relative tothe F star (egwe now know from the CHARAimages that photometric "2nd contact" is notthe traditional point where the eclipsing object reaches the far edge of the F star but occurs much later. It is probably true that the light curve can be explained by the geometry of the object as we see it. (Though this has not been demonstrated formally as far as I am aware.) However itseems unlikely that the the opaque material extends all the way to the surface of the central star and therefore a central opening most likely exists, though it is not visible because the disc is seen almost edge on.(similarly, other structures eggaps may exist but they would not beevident photometricallybecause of the angle at which weview the disc.) What is evident from the spectroscopy though is that the opacity at the 7699A neutral potassium wavelength drops significantly close to mid eclipse and there are variations in opacity throughout the eclipse. Thehypothesis is thatthis could be explained by considering structure within the disc which is mirrored by the Potassium atmosphere above and below the disc. The predictions in the Arxiv paper were speculative as they were calculated based on an ideal circular disc, wherethe pattern of variations which were seen in the first half of the eclipse might be expected to repeat in the second half. Further7699A opacity variations arebeing seenin the second half of the eclipse but the correlation with the predictions to date is poor. There is a lot of evidence in the spectroscopy however that the eclipsing object is not symmetric. The intensity and radial velocity of spectralabsorptionlines which aregenerated within the extended atmosphere of the eclipsing object are significantly different in each half ofthe eclipse. So while we may no longerneed to postulate structure within the disc to explain the photometry, the spectroscopy suggests that it maynevertheless exist. Robin


I dont disagree with anything you are saying. But my point was that a "Saturnian ring-like system" was proposed and data from this eclipse doesn't support it. So the theory needs to be discarded. That's how science works. And sometimes people are personally attached to theories for a variety of reasons and that can make it hard to discard the theory. I do take issue, however, in your allusion that there is an "absense of evidence". That's not true. There is evidence that discounts the Saturnian ring-like model. You described it in your post. "Discarded" may have been too strong of a term, as theories are rarely completely thrown out. What you are now talking about is "structure" within the system, not Saturnian-like rings. That's a different model and a different theory with different predictions we can use to test it. I would not be surprised at all to find that the system has some asymmetric structure, that's quite common in astronomy. Nothing is as clean as the physics used to describe it. And I think it would be awesome beyond belief if your spectroscopic work finds the first evidence of that.


Hi guys, I think a slight distinction has been overlooked. Ferluga claimed that there was a highly INCLINED ring system, which displayed itself photometrically by a series of photometric variations in eclipse. This theory is discounted by more recent evidence. In particular the evidence against this is (1) the interferometric observations show the system as nearly edge-on and without a central clearing we can see in the way Ferluga proposed, and (2) the photometric variations observed during this eclipse are easily assoicated with the out-of-eclipse variations of the F-star (Ferluga knew about these though). Robin's data, on the other hand, does imply that there are some larger scale structures present in the disk. The most obvious thing these could be are rings to me, but one must not discount that the disk is doubly irradiated (i.e. from both internal radiation and external, F-star radiation) which significantly distorts the disk. It is most likely that there are actually two disks: one composed of mostly dust, "the disk," and a second gaseious disk which Robin can prove showed up earlier than the disk, and will likely linger around for months to come. So I'm going to agree with Robin here, there are some large scale structures in a disk that his spectroscopy is probing. Rings? Probably, but we've got to really think about what we are probing and the geometry of the situation. Now that we've read through this, what is discounted then? Quite simply, the disk isn't highly inclined as was proposed by Ferluga. Have a good day guys and keep up the great/spirited discussions! Brian

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Succinctly put Brian, It is the thin inclined disc model (with Ferluga's additional tweak ofgaps to make the light curve fit better) which has to be abandoned in the light of the CHARA evidence. Since we now appear to have a thick almost edge on disc, the CHARAimaging and photometry tell us nothing about thedisc internalsas all we seeis the (possibly flared) outer edge ofthe opaque disc. To my mind,the inclined disc with a central hole to explain thepossible mid eclipse brighteningwas alwayssuspect as, if the disc was sufficiently inclined to allow the central hole to be seen why was the central star not also visible? Robin

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