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Finding Importance

In the memorial symposium for Peter Molnar, Phillip England suggested that Peters brilliance in many ways was recognizing the next important problem to address. And Phillip asked, how do you know? Is it internal, that you just know what is important? Do other people tell you? What criteria might you use? One possibility is that in opening up a line of research, many other follow you in and the research that follows is long and fruitful. In Peter’s case, it was (initially) continental tectonics. But just how you identify important problems is, though, itself a knotty problem.

Consider two problems: earthquake prediction and paleoelevation. Earthquake prediction has been the subject of decades of research, some of it very productive (being able to recover the history of earthquakes on many faults) and much of it not (as in, virtually every prediction actually put forward). Almost nobody would say that prediction is unimportant–provided it is successful. But how about if it isn’t possible? Is an insoluble problem an important one?

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Passing Thoughts

Recently, Peter Molnar passed away of pancreatic cancer. There are already several solid obituaries and reminiscences of him, and more are on the way. In short, Peter was a leader (if not the leader) in understanding mountain building and its impact on the climate system. He started with seismology, pushed to collect data from some of the most remote and difficult places to work, while also making contributions to plate reconstructions (some of the first with actual uncertainties came from him and Joann Stock). As he recognized the importance of gravitational potential energy in mountain evolution (in part through working with people like Phil England and Greg Houseman) and the continuum nature of deformation within large orogens (in part from work with Paul Tapponnier) he recognized the significance of paleoelevation and began scouting what others were doing in this regard. This led to working with climate scientists and paleontologists to find robust ways of getting around numerous problems in estimating the elevation of ancient mountain belts. This also led to a couple of papers (with Phil England) challenging the inference of surface uplift from erosion. Even as he plunged into unfamiliar regions like paleontology and climate science, he continued to work on instability of mantle lithosphere and its role in continental deformation. As the world of climate science became more familiar, he got interested in some largely climate science type questions such as the cause of northern hemisphere’s Ice Ages (Pleistocene). He was a prolific author with several hundred papers and an h-index over 100. Beyond that, he had an encyclopedic memory for authors and papers, a characteristic that was a huge help in developing personal connections within the field.

I am not here to talk about his contributions (and the many omissions in my summary above should be in indication of that); I list the above to make clear just how successful a scientist Peter was and to provide a hint of the breadth of his interests. I want to talk about how he felt about the scientific enterprise.

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Science Court

Bailiff: “Hear ye, hear ye, court is now in session, the honorable Leonardo da Vinci presiding”.

LdV: “You may sit. The case of Common Sense vs. Newton shall now be heard. The court notes that Galileo was unavailable to hear this case due to a conflict of interest. Prosecution, your case, please.”

Prosecution: “If it may please the court, we call Sir Isaac Newton to the stand.”

LdV: “Very well. As a reminder, in science court, there is no swearing in nor right to avoid self-incrimination. It is ideas on trial, not individuals.”

Sir Isaac Newton enters the witness box.

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Why so emotional?

GG’s spouse made an interesting observation the other day. She noted that a lot of problems in tectonics have a couple of features: they don’t seem to be getting solved, and they produce a lot of raised voices. In other words, lots of heat, little light. In contrast, she finds that the development of new techniques does not seem to produce the emotional outpourings seen in tectonics, so she has been more focused in that area. In pondering this, GG thinks it is in general about right. Why might this be?

Let’s start with the easier end, the development of new techniques. In seismology, for instance, we have seen the creation of ambient noise tomography. GG can still recall seeing one of the early posters at an AGU meeting and thinking, wow, pretty cool. In subsequent years different groups worked on improving and extending the technique. While they differed in some respects on the details of processing, these were never make-or-break disagreements. The technique has continued to be refined and applied widely.

Now some other fields might see a bit more controversy. The origination of U-Th/He dating of apatites had a lot of friction as there were disagreements about the physics of helium loss. And the use of clumped isotopes as a means of getting paleotemperatures and the oxygen isotope ratio of ancient waters has had a bumpy ride as the origin of the carbonates that are the source of measurements has proven to be a challenge. But in these cases too, while different groups emphasize different problems, they are seeking to overcome those problems and so these techniques are very much in the mainstream. No doubt somebody got hot under the collar once or twice about whether their carbonate was pedogenic or lacustrine, but that had a lot more to do with interpreting the measurement than making it.

Which brings us to tectonics. At times it just seems like tong wars erupt with regularity. In the 1980s there was the conflict between “pure shear” and “simple shear” interpretations of metamorphic core complexes that resulted in some fairly heated exchanges both in person and in print. The Baja-BC hypothesis has been around the block so many times it has worn a rut down so deep it isn’t clear anybody can escape it. It isn’t hard to find others (when did plate tectonics start? How high was the Sevier hinterland? Age of the uplift of the Rockies?). Why is this field so stalled out while producing so much controversy?

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Too much sun…

GG enjoys the occasional “huh, that seems wrong” moment. So the fact that the earliest sunset is well before the winter solstice is always good for a chuckle. Or watching where the moon rises through a month and how that sort of recaps the sun’s trip over the year. We’re coming up on another of these moments: the spring equinox and why it isn’t quite as equi- as the name suggests.

So if you got to one of the calculators showing you sunrise and sunset times, over much of the northern hemisphere you’ll see sunrise and sunset at the same time on 17 March, several days before the equinox. So what gives?

There are two main elements here, neither the same as what controlled that too-early sunrise or the lunar recap of the motions of sunrise. One is that we usually define sunrise and sunset by when the edge of the sun peeks over the horizon. But the sun has a finite size, about half a degree. At the equator, with the sun zooming straight up, that means sunrise is about 1/1440th of a day before the center of the sun comes up, which is exactly one minute. Add on the same extra minute at sunset and you can see that on the equinox that you’d expect the time from sunrise to sunset to be 12 hours and 2 minutes. At other latitudes, where the sun comes up at an angle (pretty close to 90°-latitude), the extra time is longer; here in Denver and Boulder, it buys us about another minute. So we should get three minutes more on the equinox.

But on March 20th this year, we get nine minutes of extra sun, not just three. Where are those other six minutes coming from? Well, if you’ve ever been fortunate enough to see a total lunar eclipse at the same time as the Sun was rising or setting, you’ve experienced the answer. Or if you’ve looked up from within a swimming pool. When you look up from within a pool, everything appears to be higher than what you see just above the water. Light gets bent as it enters the water, so objects appear closer to the zenith. Earth’s atmosphere bends light; the rays of light from the sun would be passing far over our heads except that as they hit the atmosphere, they get bent down towards the surface. So we actually can see a bit more than half a hemisphere when we are standing on a totally flat area. This buys us several more minutes of sunshine than we’d get on the Moon (were it rotating as fast).

It turns out that refraction in the atmosphere can be complicated by vertical variations of temperature and humidity, which can lead to the occasional misshapen moon:

Moonrise from near summit of Mt. Washington. CH Jones photo.

In addition, those of us at higher altitude have less atmosphere to play with, so the effect here in Boulder is probably a bit less than for folks on the seashore. So these numbers are closer to suggestions than rigidly precise times.

So there you go. Another little treat to enjoy as the northern hemisphere days get longer. If you want another discussion of this with some pictures, has a decent exposition.

Is parsimony really a guiding principle of science?

Make things simple, but not simpler. Occam’s razor. Reductionist science lives on finding an underlying structure that accounts for the important differences in observations. If you can explain a bunch of observations with one rule, that beats having a special rule for each observation. But is this really a (or the) guiding principle of science?

Well, arguably the most parsimonious explanation for stuff is “God made it that way.” Why did we abandon such a universal explanation for everything? While today we look to science for explanations about why something happens (auroras, shooting stars, earthquakes, tsunamis), it feels like the origin of science was the more prosaic “what will happen if I do this?” Flinging things at enemies was a popular option in warfare for a long time, but the trial-and-error approach isn’t so wonderful if your enemy, seeing where you are firing from, is quicker to lob a shell at you more precisely. Recognizing that there are rules that are quite predictable gives you an edge–you can get things done more efficiently or even do things you previously couldn’t do at all. You don’t need to answer “why is there gravity” to be able to use a theory for it to do things like go to the moon.

So maybe science is being parsimonious while being able to predict things. Yet some theories look less than optimally parsimonious. The Standard Model for physics looks like something Rube Goldberg might have come up with. Is string theory really parsimonious? You get the feeling Occam’s Razor will draw blood on some pretty well established theories.

Earth science really slams into these problems. Say, you want a theory in how mountain ranges are created. You look today and see the Himalaya rising as India hits Asia. OK, maybe mountain ranges are made as two continents collide. Oh, but we have the Andes, too, and mountains in Alaska. Um, OK, well, mountains are made where two plates collide. OK, great. A fairly simple explanation that allows us to look for mountains. (We’ll put aside where plates collide and all we get are a few volcanoes).

That explain all mountains? It does seem helpful for the Appalachians and Urals and Alps. How about the Sierra Nevada? Assuming the young Sierra story holds water (it is argued), the range has largely risen up with plates not colliding. Seems trouble for our universal mountain-building theory. Or the ranges of the Basin and Range; why is all that going on? Sure seems distant from the plate boundary.

But then we have the Rockies about 1000km from the edge of a plate. Why are the Rockies there instead of where the plates were apparently colliding? Maybe a plate was scraping the bottom of North America. Maybe the Colorado Plateau was really strong. Maybe there was dynamic flow in the mantle. Maybe the Ancestral Rockies had set things up. How universal and parsimonious is our plates-colliding theory if we keep finding troublesome mountains?

In a weird way, earth science almost moves in the opposite direction of, say, particle physics. The physicists are looking for the one equation to rule them all; earth scientists are teasing out all the different ways Earth can do something. Parsimony in earth science is almost backwards from the way a lot of folks regard Occam’s Razor. We will hone an explanation to its bare essentials and then compare with all the examples we have. The ones it explains we can set aside. The ones it cannot we go on to investigate. There are two possibilities: our original explanation was wrong and focused on immaterial aspects, or there is more than one way to achieve some outcome. The great challenge in all this is to somehow sidestep the features that are not important while really nailing the ones that matter.

Consider the Rockies again. A fairly likely candidate for the same process is in South America, the Sierras Pampeanas. A paper some time ago pointed out that the geometry of these ranges (length and width) looked to be about the same as in the Rockies, and the bounding faults are reverse or thrust faults in both places. Is this then the key element that provides the insight into the origin of the Rockies? Some think so, but GG (and some others) have argued this is simply what happens when you squish an area in a continental interior with a thin cover of sedimentary rocks. Kind of like that you can’t really tell if a nail was driven by a hammer or a nailgun; the different tools can make the same outcome. GG argues that it is the source of the compressional stress that we care about and that important differences between the Sierras Pampeanas and the Rockies cannot be dismissed. Which is really right? With so few possible candidates, it is hard to tell. Occam’s Razor has little effect when your choices are so few and potential confounding features are so widespread.

Parsimony is an important tool, but not really the be-all and end-all some make it out to be. There is a temptation to force discrepant cases into a theory’s box when you value parsimony over all. Sometimes it is the right call, sometimes not. Relying on Occam to answer the question can be a big mistake.

What is Peer Review for, anyways?

Every now and then GG encounters things as he dons the different hats of a professional earth scientist that just require revisiting some aspects of the job. And so today’s topic is peer review.

First let’s dispense with the obvious: peer review is not saying “the scientific community has examined this research closely and guarantees it is free from mistakes and blunders and is a true representation of reality.” Yes, many of you are laughing, of course it isn’t! But the public often is led to think this is what it is.

Now, we do often like to say that it is a means of preventing bad science from being published. This is also untrue: with the plethora of journals out there, it is awfully hard to prevent bad science from being published somewhere. GG has had the experience of leading an author point-by-point though mistakes in their work only to have that author claim to agree but leave the same wretched mistakes in the revised manuscript which, once rejected, promptly showed up in another (clearly less discriminating) journal. At most we might prevent bad science from being published in our journal, but unless the AEs and editors are all in lockstep, even that is too strong a statement. A related and fairly uncommon (in GG’s experience) situation is a paper that fails to recognize it isn’t offering anything new; in this case, this might prevent unnecessary duplication within the literature. Of course there are the examples of deceit that we now find occasionally in the literature; these are really outside the pale and not part of the run of the mill execution of the scientific enterprise.

GG’s view is that normal peer review will usually address two things: one, whether the journal in question is appropriate, and two, if or how authors have failed to clearly make their point. There are perfectly fine works that simply are not a good fit for a journal. Ideally the editor catches these and pitches them back, but sometimes it is the reviewers. This is typically a small part of the operation for anything other than the most high profile letter journals. The second point, though, is really where peer review matters most.

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Silencing Comments

A thread on an AGU bulletin board emerged demanding that an AGU journal return to allowing the practice of comments and replies. Many went so far as to call the absence of a comments policy to be an assault on science. The basic argument is that if you find an error in a paper that should be corrected, there is no easy way to point this out without a comment–the error might not itself amount to a new publication.

This is kind of an interesting conundrum. On many public-facing websites and publications, the comments section is proof of a lowest possible level of discussion with ad hominem attacks and irrelevant discussion [not here, of course!], so it is kind of amusing to see such a venue desired in the scientific community. Except, of course, the scientific comments are not off-the-cuff challenges to the intelligence of the authors, but are instead carefully written documents that point out an issue in a published article. As such, these are usually reviewed at minimum by the editor of the journal and often are sent out for mail review. So what’s not to like?

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Pronouns and Papers

Over the past few years, it has become standard practice in many universities to list preferred pronouns for individuals.This allows individuals to be characterized in a manner consistent with their desires. It might be time to carry this into the scientific literature, but probably not the way you are thinking.

Consider the following from one of GG’s papers:

Some numerical experiments by O’Driscoll et al. (2009) explored concepts relevant to this hypothesis; they found that the presence of a lithospheric root will lead to… 

Jones et al.., Geosphere; February 2011; v. 7; no. 1; p. 183–201; doi: 10.1130/GES00575.1

This is pretty standard usage, yet what really is the antecedent for “they”? It happens to be O’Driscoll et al. (2009). Which is a single paper, not a group of people. This is exceptionally common usage in the literature, in that we assign to the authors the results of the paper. Part of this is avoiding personifying an inanimate object (the paper didn’t “find” anything any more than your water glass “found” the water in it). But occasionally when people change their minds, you can find some things that might look silly. For instance, it would be fair to write “Jones (1994) felt that the Isabella anomaly came from the lithosphere under the Tehachapis, while Jones et al. (2014) argued it came from under the Sierra Nevada.” Now that is the same Jones, yet the interpretations are different. And this is because the earlier paper doesn’t change meaning as the author revises interpretations. So would you really want to write the same information this way? “Jones (1994) used an early seismic array to image the Isabella anomaly. He argued it came from under the Tehachapis, while Jones et al. (2014) argued it came from under the Sierra.” This Jones fellow seems pretty slippery, no?

This might seem silly; after all, the meaning is still pretty clear; author Jones changed his mind somewhere between 1994 and 2014. But the thing is, by personalizing the paper–making the association between the author(s) and the paper so strong that they are interchangeable–we make it that much harder for readers to separate a specific product of a specific study with the individual(s) who wrote up the study. Once we release a paper into the wild, it is gone, not to be fixed by a later change of heart. It is the paper that will continue to make a claim long after its author has moved on. So maybe we should use pronouns other than “his” or “hers” and move on to “its” to make clear that it isn’t the current state of the authors that we are looking at, it is the material presented in the paper.

There would still be instances where referring to the author(s) instead of the papers might make sense. Consider this (from the same paper):

Only Bird’s (1988) specific geodynamic version of the flat slab has provided quantitative predictions at a lithospheric scale from trench to foreland; it is based on a review of the physical relations of several aspects of the hypothesis (Bird, 1984). In developing his model, Bird sought to not only produce deformation far to the east of earlier shortening…

In this case, the text in the last sentence is stepping out from the two papers cited to consider motivations driving the development of the published papers. Now this might not be fair, but it is exploring what the person was doing from the 1984 paper to the 1988 paper. There is still some ambiguity of timing, but in this case it isn’t quite the papers per se being considered but the person doing the work.

Anyways, for more straightforward examples, would the use of more generic pronouns for scientific publications be kind of annoying for us fossils? Sure, but then we’ve had to deal with personal pronouns of “they/them” that just produce cognitive dissonance as our internal English teacher lashes out from years ago. If we can deal with that, maybe we could depersonalize the presentation and discussion of science in a way that makes it easier for authors to later revise their views without seeming to be contradictory.

In Need of Hypotheses

GG wrote something about this awhile back, but it feels worthy of a revisit. Just why is it that geologists still like this “multiple working hypotheses” ideas?

What reminded GG of this was reading Naomi Oreskes’s book on the rejection of continental drift (or Amazon link). In there, it sort of seems as though multiple working hypotheses comes across as something of an excuse used by twentieth century American geoscientists to dance past the evidence for continental drift. It kind of comes across as a dated approach for pre-quantitative science. GG would argue that in studying complex phenomena that it is an important tool–one perhaps worthy of keeping in mind in dealing with the current pandemic.

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