Category Archives: method

Supporting conceptual understanding of the Coriolis force through laboratory experiments

My friend Pierré and I started working on this article when both of us were still working at the Geophysical Institute in Bergen. It took forever to get published, mainly because both of us had moved on to different jobs with other foci, so maybe it’s not a big deal that it took me over a year to blog it? Anyway, I still think it is very important to introduce any kind of rotating experiments by first making sure people don’t harbour misconceptions about the Coriolis effect, and this is the best way we came up with to do so. But I am happy to hear any suggestions you might have on how to improve it :-)

Supporting Conceptual Understanding of the Coriolis Force Through Laboratory Experiments

By Dr. Mirjam S. Glessmer and Pierré D. de Wet

Published in Current: The Journal of Marine Education, Volume 31, No 2, Winter 2018

Do intriguing phenomena sometimes capture your attention to the extent that you haveto figure out why they work differently than you expected? What if you could get your students hooked on your topic in a similar way?

Wanting to comprehend a central phenomenon is how learning works best, whether you are a student in a laboratory course or a researcher going through the scientific process. However, this is not how introductory classes are commonly taught. At university, explanations are often presented or developed quickly with a focus on mathematical derivations and manipulations of equations. Room is seldom given to move from isolated knowledge to understanding where this knowledge fits in the bigger picture formed of prior knowledge and experiences. Therefore, after attending lectures and even laboratories, students are frequently able to give standard explanations and manipulate equations to solve problems, but lack conceptual understanding (Kirschner & Meester, 1988): Students might be able to answer questions on the laws of reflection, yet not understand how a mirror works, i.e. why it swaps left-right but not upside-down (Bertamini et al., 2003).

Laboratory courses are well suited to address and mitigate this disconnect between theoretical knowledge and practical application. However, to meet this goal, they need to be designed to focus specifically on conceptual understanding rather than other, equally important, learning outcomes, like scientific observation as a skill or arguing from evidence (NGSS, 2013), calculations of error propagations, application of specific techniques, or verifying existing knowledge, i.e. illustrating the lecture (Kirschner & Meester, 1988).

Based on experience and empirical evidence, students have difficulties with the concept of frames of reference, and especially with fictitious forces that are the result of using a different frame of reference. We here present how a standard experiment on the Coriolis force can support conceptual understanding, and discuss the function of employing individual design elements to maximize conceptual understanding.

HOW STUDENTS LEARN FROM LABORATORY EXPERIMENTS

In introductory-level college courses in most STEM disciplines, especially in physics-based ones like oceanography or meteorology and all marine sciences, laboratory courses featuring demonstrations and hands-on experiments are traditionally part of the curriculum.

Laboratory courses can serve many different and valuable learning outcomes: learning about the scientific process or understanding the nature of science, practicing experimental skills like observation, communicating about scientific content and arguing from evidence, and changing attitudes (e.g. Feisel & Rosa, 2005; NGSS, 2013; Kirschner & Meester, 1988; White, 1996). One learning outcome is often desired, yet for many years it is known that it is seldomly achieved: increasing conceptual understanding (Kirschner & Meester, 1988, Milner-Bolotin et al., 2007). Under general dispute is whether students actually learn from watching demonstrations and conducting lab experiments, and how learning can be best supported (Kirschner & Meester, 1988; Hart et al., 2000).

There are many reasons why students fail to learn from demonstrations (Roth et al., 1997). For example, in many cases separating the signal to be observed from the inevitably measured noise can be difficult, and inference from other demonstrations might hinder interpretation of a specific experiment. Sometimes students even “remember” witnessing outcomes of experiments that were not there (Milner-Bolotin et al., 2007). Even if students’ and instructors’ observations were the same, this does not guarantee congruent conceptual understanding and conceptual dissimilarity may persist unless specifically addressed. However, helping students overcome deeply rooted notions is not simply a matter of telling them which mistakes to avoid. Often, students are unaware of the discrepancy between the instructors’ words and their own thoughts, and hear statements by the instructor as confirmation of their own thoughts, even though they might in fact be conflicting (Milner-Bolotin et al., 2007).

Prior knowledge can sometimes stand in the way of understanding new scientific information when the framework in which the prior knowledge is organized does not seem to organically integrate the new knowledge (Vosniadou, 2013).The goal is, however, to integrate new knowledge with pre-existing conceptions, not build parallel structures that are activated in context of this class but dormant or inaccessible otherwise. Instruction is more successful when in addition to having students observe an experiment, they are also asked to predict the outcome before the experiment, and discuss their observations afterwards (Crouch et al., 2004). Similarly, Muller et al. (2007) find that even learning from watching science videos is improved if those videos present and discuss common misconceptions, rather than just presenting the material textbook-style. Dissatisfaction with existing conceptions and the awareness of a lack of an answer to a posed question are necessary for students to make major changes in their concepts (Kornell, 2009, Piaget, 1985; Posner et al., 1982). When instruction does not provide explanations that answer students’ problems of understanding the scientific point of view from the students’ perspective, it can lead to fragmentation and the formation of synthetic models (Vosniadou, 2013).

One operationalization of a teaching approach to support conceptual change is the elicit-confront-resolve approach (McDermott, 1991), which consists of three steps: Eliciting a lingering misconception by asking students to predict an experiment’s outcome and to explain their reasons for the prediction, confronting students with an unexpected observation which is conflicting with their prediction, and finally resolving the matter by having students come to a correct explanation of their observation.

HOW STUDENTS TRADITIONALLY LEARN ABOUT THE CORIOLIS FORCE

The Coriolis force is essential in explaining formation and behavior of ocean currents and weather systems we observe on Earth. It thus forms an important part of any instruction on oceanography, meteorology or climate sciences. When describing objects moving on the rotating Earth, the most commonly used frame of reference would be fixed on the Earth, so that the motion of the object is described relative to the rotating Earth. The moving object seems to be under the influence of a deflecting force – the Coriolis force – when viewed from the co-rotating reference frame. Even though the movement of an object is independent of the frame of reference (the set of coordinate axes relative to which the position and movement of an object is described is arbitrary and usually made such as to simplify the descriptive equations of the object), this is not immediately apparent.

Temporal and spatial frames of reference have been described as thresholds to student understanding (Baillie et al., 2012, James, 1966; Steinberg et al., 1990). Ever since its first mathematical description in 1835 (Coriolis, 1835), this concept is most often taught as a matter of coordinate transformation, rather than focusing on its physical relevance (Persson, 1998). Most contemporary introductory books on oceanography present the Coriolis force in that form (cf. e.g. Cushman-Roisin, 1994; Gill, 1982; Pinet, 2009; Pond and Pickard, 1983; Talley et al., 2001; Tomczak and Godfrey, 2003; Trujillo and Thurman, 2013). The Coriolis force is therefore often perceived as “a ‘mysterious’ force resulting from a series of ‘formal manipulations’” (Persson, 2010). Its unintuitive and seemingly un-physical character makes it difficult to integrate into existing knowledge and understanding, and “even for those with considerable sophistication in physical concepts, one’s first introduction to the consequences of the Coriolis force often produces something analogous to intellectual trauma” (Knauss, 1978).

In many courses, helping students gain a deeper understanding of rotating systems and especially the Coriolis force, is approached by presenting demonstrations, typically of a ball being thrown on a merry-go-round, showing the movement simultaneously from a rotating and a non-rotating frame (Urbano & Houghton, 2006), either in the form of movies or simulations, or in the lab as demonstration, or as a hands-on experiment[i]. After conventional instruction that exposed students to discussions and simulations, students are able to do calculations related to the Coriolis force.

Nevertheless, when confronted with a real-life situation where they themselves are not part of the rotating system, students show difficulty in anticipating the movement of an object on a rotating body. In a traditional Coriolis experiment (Figure1), for example, a student launches a marble from a ramp on a rotating table (Figure 2A, B) and the motion of the marble is observed from two vantage points: where they are standing in the room, i.e. outside of the rotating system of the table; and on a screen that displays the table, as captured by a co-rotating camera mounted above it. When asked, before that experiment, what path the marble on the rotating surface will take, students report that they anticipate observing a deflection, its radius depending on the rotation’s direction and rate. After having observed the experiment, students report that they saw what they expected to see even though it never happened. Contextually triggered, knowledge elements are invalidly applied to seemingly similar circumstances and lead to incorrect conclusions (DiSessa & Sherin, 1988; Newcomer, 2010). This synthetic model of always expecting to see a deflection of an object moving on a rotating body, no matter which system of reference it is observed from, needs to be modified for students to productively work with the concept of the Coriolis force.

Figure 1: Details of the Coriolis experiment

Figure 1: Details of the Coriolis experiment

Despite these difficulties in interpreting the observations and understanding the underlying concepts, rotating tables recently experienced a rise in popularity in undergraduate oceanography instruction (Mackin et al., 2012) as well as outreach to illustrate features of the oceanic and atmospheric circulation(see for example Marshall and Plumb, 2007). This makes it even more important to consider what students are intended to learn from such demonstrations or experiments, and how these learning outcomes can be achieved.

Figure 2A: View of the rotating table including the video camera on the scaffolding above the table. B: Sketch of the rotating table, the mounted (co-rotating) camera, and the marble on the table. C: Student tracing the curved trajectory of the marble on a transparency. On the screen, the experiment is shown as captured by the co-rotating camera, hence in the rotating frame of reference. 

Figure 2A: View of the rotating table including the video camera on the scaffolding above the table. B: Sketch of the rotating table, the mounted (co-rotating) camera, and the marble on the table. C: Student tracing the curved trajectory of the marble on a transparency. On the screen, the experiment is shown as captured by the co-rotating camera, hence in the rotating frame of reference.

A RE-DESIGNED HANDS-ON INTRODUCTION TO THE CORIOLIS FORCE

The traditional Coriolis experiment, featuring a body on a rotating table[ii], observed both from within and from outside the rotating system, can be easily modified to support conceptual understanding.

When students of oceanography are asked to do a “dry” experiment (in contrast to a “wet” one with water in a tank on the rotating table) on the Coriolis force, at first, this does not seem like a particularly interesting phenomenon to students because they believe they know all about it from the lecture already. The experiment quickly becomes intriguing when a cognitive dissonance arises and students’ expectations do not match their observations. We use an elicit-confront-resolve approach to help students observe and understand the seemingly conflicting observations made from inside versus outside of the rotating system (Figure 3). To aid in making sense of their observations in a way that leads to conceptual understanding the three steps elicit, confront, and resolve are described in detail below.

Figure 3: Positions of the ramp and the marble as observed from above in the non-rotating (top) and rotating (bottom) case. Time progresses from left to right. In the top plots, the positions are shown in inert space. From left to right, the current positions of the ramp and marble are added with gradually darkening colors. In the bottom plots, the ramp stays in the same position relative to the co-rotating observer, but the marble moves and the current position is always displayed with the darkest color.

Figure 3: Positions of the ramp and the marble as observed from above in the non-rotating (top) and rotating (bottom) case. Time progresses from left to right. In the top plots, the positions are shown in inert space. From left to right, the current positions of the ramp and marble are added with gradually darkening colors. In the bottom plots, the ramp stays in the same position relative to the co-rotating observer, but the marble moves and the current position is always displayed with the darkest color.

2. What do you think will happen? Eliciting a (possibly) lingering misconception

Students have been taught in introductory lectures that any moving object in a counter-clockwise rotating system (i.e. in the Northern Hemisphere) will be deflected to the right. They are also aware that the extent to which the object is deflected depends on its velocity and the rotational speed of the reference frame. In our experience, due to this prior schooling, students expect to see a Coriolis deflection even when they observe a rotating system “from the outside”. When the conventional experiment is run without going through the additional steps described here, students often report having observed the (non-existent) deflection.

By activating this prior knowledge and discussing what students anticipate observing under different conditions before the actual experiment is conducted, the students’ insights are put to the test. This step is important since the goal is to integrate new knowledge with pre-existing conceptions, not build parallel structures that are activated in context of this class but dormant or inaccessible otherwise. Sketching different scenarios (Fan, 2015; Ainsworth et al., 2011) and trying to answer questions before observing experiments support the learning process since students are usually unaware of their premises and assumptions (Crouch et al., 2004). Those need to be explicated and documented (even just by saying them out loud) before they can be tested, and either be built on, or, if necessary, overcome. 

We therefore ask students to observe and describe the path of a marble being radially launched from the perimeter of the circular, non-rotating table by a student standing at a marked position next to the table, the “launch position”. The marble is observed rolling towards and over the center point of the table, dropping off the table diametrically opposite from the position from which it was launched. So far nothing surprising. A second student – the catcher– is asked to stand at the position where the marble dropped off the table’s edge so as to catch the marble in the non-rotating case. The position is also marked on the floor with tape to document the observation.

Next, the experimental conditions of this thought experiment (Winter, 2015) are varied to reflect on how the result depends on them. The students are asked to predict the behavior of the marble once the table is put into slow rotation. At this point, students typically enquire about the direction of rotation and, when assured that “Northern Hemisphere” counter-clockwise rotation is being applied, their default prediction is that the marble will be deflected to the right. When asked whether the catcher should alter their position, the students commonly answer that the catcher should move some arbitrary angle, but typically less than 90 degrees, clockwise around the table.  The question of the influence of an increase in the rotational rate of the table on the catcher’s placement is now posed. “Still further clockwise”, is the usual answer. This then leads to the instructor’s asking whether a rotational speed exists at which the student launching the marble, will also be able to catch it themselves. Usually the students confirm that such a situation is indeed possible.

2. Did you observe what you expected to see? Confronting the misconception

After “eliciting” student conceptions, the “confront” step serves to show the students the discrepancy between what they expect to see, and what they actually observe. Starting with the simple, non-rotating case, the marble is launched again and the nominated catcher, positioned diametrically across from the launch position, seizes the marble as it falls off the table’s surface right in front of them. As theoretically discussed beforehand, the table is then put into rotation at incrementally increasing rates, with the marble being launched from the same position for each of the different rotational speeds.  It becomes clear that the catcher can – without any adjustments to their position – remain standing diametrically opposite to the student launching the marble – the point where the marble drops to the floor. Hence students realize that the movement of the marble relative to the non-rotating laboratory is unaffected by the table’s rotation rate.

This observation appears counterintuitive, since the camera, rotating with the system, shows the curved trajectories the students had expected; segments of circles with decreasing radii as the rotation rate increases. Furthermore, to add to the confusion, when observed from their positions around the rotating table, the path of the marble on the rotating table appears to show a deflection, too.  This is due to the observer’s eye being fooled by focusing on features of the table, e.g. marks on the table’s surface or the bars of the camera scaffold, relative to which the marble does, indeed, follow a curved trajectory. To overcome this optical illusion, the instructor may ask the students to crouch, diametrically across from the launcher, so that their line of sight is aligned with the table’s surface, i.e. at a zero-zenith angle of observation. From this vantage point, the marble is observed to indeed be moving in a straight line towards the observer, irrespective of the rotation rate of the table. Observing from different perspectives and with focus on different aspects (Is the marble coming directly towards me? Does it fall on the same spot as before? Did I need to alter my position in the room at all?) helps students gain confidence in their observations.

To solidify the concept, the table may again be set into rotation. The launcher and the catcher are now asked to pass the marble to one another by throwing it across the table without it physically making contact with the table’s surface. As expected, the marble moves in a straight line between the launcher and the catcher, whom are both observing from an inert frame of reference. However, when viewing the playback of the co-rotating camera, which represents the view from the rotating frame of reference, the trajectory is observed as curved[iii].

3. Do you understand what is going on? Resolving the misconception

Misconceptions that were brought to light during the “elicit” step, and whose discrepancy with observations was made clear during the “confront” step, are finally resolved in this step. While this sounds very easy, in practice it is anything but. For learning to take place, the instructor needs to aid students in reflecting upon and reassessing previous knowledge by pointing out and dispelling any remaining implicit assumptions, making it clear that the discrepant trajectories are undoubtedly the product of viewing the motion from different frames of reference. Despite the students’ observations and their participation in the experiment this does not happen instantaneously. Oftentimes further, detailed discussion is required. Frequently students have to re-run the experiment themselves in different roles (i.e. as launcheras well as catcher) and explicitly state what they are noticing before they trust their observations.

For this experiment to benefit the learning outcomes of the course, which go beyond understanding of a marble on a rotating table and deal with ocean and atmosphere dynamics, knowledge needs to be integrated into previous knowledge structures and transferred to other situations. This could happen by discussion of questions like, for example: How could the experiment be modified such that a straight trajectory is observed on the screen? What would we expect to observe if we added a round tank filled with water and paper bits floating on it to the table and started rotating it? How are our observations of these systems relevant and transferable to the real world? What are the boundaries of the experiment?

IS IT WORTH THE EXTRA EFFORT? DISCUSSION

We taught an undergraduate laboratory course which included this experiment for several years. In the first year, we realized that the conventional approach was not effective. In the second year, we tried different instructional approaches and settled on the one presented here. We administered identical work sheets before and after the experiment. These work sheets were developed as instructional materials to ensure that every student individually went through the elicit-confront-resolve process. Answers on those worksheets show that all our students did indeed expect to see a deflection despite observing from an inert frame of reference: Students were instructed to consider both a stationary table and a table rotating at two different rates.  They were then asked to, for each of the scenarios, mark with an X the location where they thought the marble would contact the floor after dropping off the table’s surface.  Before instruction, all students predicted that the marble would hit the floor in different spots – diametrically across from the launch point for no rotation, and at increasing distances from that first point with increasing rotation rates of the table (Figure 4). This is the exact misconception we aimed to elicit with this question: students were applying correct knowledge (“in the Northern Hemisphere a moving body will be deflected to the right”) to situations where this knowledge was not applicable: when observing the rotating body and the moving object upon it from an inert frame of reference.

Figure 4A: Depiction of the typical wrong answer to the question: Where would a marble land on the floor after rolling across a table rotating at different rotation rates? B: Correct answer to the same question. C: Correct traces of marbles rolling across a rotating table.

Figure 4A: Depiction of the typical wrong answer to the question: Where would a marble land on the floor after rolling across a table rotating at different rotation rates? B: Correct answer to the same question. C: Correct traces of marbles rolling across a rotating table.

In a second question, students were asked to imagine the marble leaving a dye mark on the table as it rolls across it, and to draw these traces left on the table. In this second question, students were thus required to infer that this would be analogous to regarding the motion of the marble as observed from the co-rotating frame of reference. Drawing this trajectory correctly before the experiment is run does not imply a correct conceptual understanding, since the transfer between rotating and non-rotating frames of references is not happening yet and students draw curved trajectories for all cases. However, after the experiment this question is useful especially in combination with the first one, as it requires a different answer than the first, and an answer that students just learned they should not default to.

The students’ laboratory reports supply additional support of the usefulness of this new approach.  These reports had to be submitted a week after doing the experiment and accompanying work sheets, which were collected by the instructors.  One of the prompts in the lab report explicitly addresses observing the motion from an inert frame of reference as well as the influence of the table’s rotational period on such motion. This question was answered correctly by all students. This is remarkable for three reasons: firstly, because in the previous year with conventional instruction, this question was answered incorrectly by the vast majority of students; secondly, from our experience, lab reports have a tendency to be eerily similar year after year which did not hold true for tis specific question; and lastly, because for this cohort, it is one of very few questions that all students answered correctly in their lab reports, which included seven experiments in addition to the Coriolis experiment. These observations lead us to believe that students do indeed harbor the misconception we suspected, and that the modified instructional approach has supported conceptual change.

CONCLUSIONS

We present modifications to a “very simple” experiment and suggest running it before subjecting students to more advanced experiments that illustrate concepts like Taylor columns or weather systems. These more complex processes and experiments cannot be fully understood without first understanding the Coriolis force acting on the arguably simplest bodies. Supplying correct answers to standard questions alone, e.g. “deflection to the right on the northern hemisphere”, is not sufficient proof of understanding.

In the suggested instructional strategy, students are required to explicitly state their expectations about what the outcome of an experiment will be, even though their presuppositions are likely to be wrong. The verbalizing of their assumptions aids in making them aware of what they implicitly hold to be true. This is a prerequisite for further discussion and enables confrontation and resolution of potential misconceptions. Wesuggest using an elicit-confront-resolve approach even when the demonstration is not run on an actual rotating table, but virtually conducted instead, for example using Urbano & Houghton (2006)’s Coriolis force simulation. We claim that the approach is nevertheless beneficial to increasing conceptual understanding.

We would like to point out that gaining insight from any seemingly simple experiment, such as the one discussed in this article, might not be nearly as straightforward or obvious for the students as anticipated by the instructor. Using an intriguing phenomenon to be investigated experimentally, and slightly changing conditions to understand their influence on the result, is highly beneficial. Probing for conceptual understanding in new contexts, rather than the ability to calculate a correct answer, proved critical in understanding where the difficulties stemmed from, and only a detailed discussion with several students could reveal the scope of difficulties.

ACKNOWLEDGEMENTS

The authors are grateful for the students’ consent to be featured in this article’s figures.

 

RESOURCES

Movies of the experiment can be seen here:

Rotating case: https://vimeo.com/59891323

Non-rotating case: https://vimeo.com/59891020

Using an old disk player and a ruler in absence of a co-rotating camera: https://vimeo.com/104169112

 

REFERENCES

Ainsworth, S., Prain, V., & Tytler, R. 2011. Drawing to Learn in Science Science, 333(6046), 1096-1097 DOI: 10.1126/science.1204153

Baillie, C., MacNish, C., Tavner, A., Trevelyan, J., Royle, G., Hesterman, D., Leggoe, J., Guzzomi, A., Oldham, C., Hardin, M., Henry, J., Scott, N., and Doherty, J.2012. Engineering Thresholds: an approach to curriculum renewal. Integrated Engineering Foundation Threshold Concept Inventory 2012. The University of Western Australia, <http://www.ecm.uwa.edu.au/__data/assets/pdf_file/0018/2161107/Foundation-Engineering-Threshold-Concept-Inventory-120807.pdf>

Bertamini, M., Spooner, A., & Hecht, H. (2003). Naïve optics: Predicting and perceiving reflections in mirrors. JOURNAL OF EXPERIMENTAL PSYCHOLOGY HUMAN PERCEPTION AND PERFORMANCE29(5), 982-1002.

Coriolis, G. G. 1835. Sur les équations du mouvement relatif des systèmes de corps. J. de l’Ecole royale polytechnique15: 144–154.

Crouch, C. H., Fagen, A. P., Callan, J. P., and Mazur. E. 2004. Classroom Demonstrations: Learning Tools Or Entertainment?. American Journal of Physics, Volume 72, Issue 6, 835-838.

Cushman-Roisin, B. 1994. Introduction to Geophysical Fluid DynamicsPrentice-Hall. Englewood Cliffs, NJ, 7632.

diSessa, A.A. and Sherin, B.L., 1998. What changes in conceptual change?. International journal of science education20(10), pp.1155-1191.

Durran, D. R. and Domonkos, S. K. 1996. An apparatus for demonstrating the inertial oscillation, BAMS, Vol 77, No 3

Fan, J. (2015). Drawing to learn: How producing graphical representations enhances scientific thinking. Translational Issues in Psychological Science, 1(2), 170-181 DOI: 10.1037/tps0000037

Gill, A. E. 1982. Atmosphere-ocean dynamics(Vol. 30). Academic Pr.

James, E.L., 1966. Acceleration= v2/r. Physics Education1(3), p.204.

Kornell, N., Jensen Hays, M., and Bjork, R.A. (2009), Unsuccessful Retrieval Attempts Enhance Subsequent Learning, Journal of Experimental Psychology: Learning, Memory, and Cognition 2009, Vol. 35, No. 4, 989–998

Hart, C., Mulhall, P., Berry, A., Loughran, J., and Gunstone, R. 2000.What is the purpose of this experiment? Or can students learn something from doing experiments?,Journal of Research in Science Teaching, 37(7), p 655–675

Kirschner, P.A. and Meester, M.A.M., 1988. The laboratory in higher science education: Problems, premises and objectives. Higher education17(1), pp.81-98.

Knauss, J. A. 1978. Introduction to physical oceanography. Englewood Cliffs, N.J: Prentice-Hall.

Mackin, K.J., Cook-Smith, N., Illari, L., Marshall, J., and Sadler, P. 2012. The Effectiveness of Rotating Tank Experiments in Teaching Undergraduate Courses in Atmospheres, Oceans, and Climate Sciences, Journal of Geoscience Education, 67–82

Marshall, J. and Plumb, R.A. 2007. Atmosphere, Ocean and Climate Dynamics, 1stEdition, Academic Press

McDermott, L. C. 1991. Millikan Lecture 1990: What we teach and what is learned – closing the gap, Am. J. Phys. 59 (4)

Milner-Bolotin, M., Kotlicki A., Rieger G. 2007. Can students learn from lecture demonstrations? The role and place of Interactive Lecture Experiments in large introductory science courses.The Journal of College Science Teaching, Jan-Feb, p.45-49.

Muller, D.A., Bewes, J., Sharma, M.D. and Reimann P. 2007.Saying the wrong thing: improving learning with multimedia by including misconceptions, Journal of Computer Assisted Learning (2008), 24, 144–155

Newcomer, J.L. 2010. Inconsistencies in Students’ Approaches to Solving Problems in Engineering Statics, 40th ASEE/IEEE Frontiers in Education Conference, October 27-30, 2010, Washington, DC

NGSS Lead States. 2013. Next generation science standards: For states, by states. National Academies Press.

Persson, A. 1998.How do we understand the Coriolis force?, BAMS, Vol 79, No 7

Persson, A. 2010.Mathematics versus common sense: the problem of how to communicate dynamic meteorology, Meteorol. Appl. 17: 236–242

Piaget, J. (1985). The equilibration of cognitive structure. Chicago: University of Chicago Press.

Pinet, P. R. 2009. Invitation to oceanography. Jones & Bartlett Learning.

Posner, G.J., Strike, K.A., Hewson, P.W. and Gertzog, W.A. 1982. Accommodation of a Scientific Conception: Toward a Theory of Conceptual Change. Science Education 66(2); 211-227

Pond, S. and G. L. Pickard 1983. Introductory dynamical oceanography. Gulf Professional Publishing.

Roth, W.-M., McRobbie, C.J., Lucas, K.B., and Boutonné, S. 1997. Why May Students Fail to Learn from Demonstrations? A Social Practice Perspective on Learning in Physics. Journal of Research in Science Teaching, 34(5), page 509–533

Steinberg, M.S., Brown, D.E. and Clement, J., 1990. Genius is not immune to persistent misconceptions: conceptual difficulties impeding Isaac Newton and contemporary physics students. International Journal of Science Education12(3), pp.265-273.

Talley, L. D., G. L. Pickard, W. J. Emery and J. H. Swift 2011. Descriptive physical oceanography: An introduction. Academic Press.

Tomczak, M., and Godfrey, J. S. 2003. Regional oceanography: an introduction. Daya Books.

Trujillo, A. P., and Thurman, H. V. 2013. Essentials of Oceanography, Prentice Hall; 11 edition (January 14, 2013)

Urbano, L.D., Houghton J.L., 2006. An interactive computer model for Coriolis demonstrations.Journal of Geoscience Education 54(1): 54-60

Vosniadou, S. (2013). Conceptual change in learning and instruction: The framework theory approach. International handbook of research on conceptual change2, 11-30.

White, R. T. 1996. The link between the laboratory and learning. International Journal of Science Education18(7), 761-774.

Winter, A., 2015. Gedankenexperimente zur Auseinandersetzung mit Theorie. In: Die Spannung steigern – Laborpraktika didaktisch gestalten.Schriften zur Didaktik in den IngenieurswissenschaftenNr. 3, M. S. Glessmer, S. Knutzen, P. Salden (Eds.), Hamburg

Endnotes

[i]While tremendously helpful in visualizing an otherwise abstract phenomenon, using a common rotating table introduces difficulties when comparing the observed motion to the motion on Earth. This is, among other factors, due to the table’s flat surface (Durran and Domonkos, 1996), the alignment of the (also fictitious) centrifugal force with the direction of movement of the marble (Persson, 2010), and the fact that a component of axial rotation is introduced to the moving object when launched. Hence, the Coriolis force is not isolated. Regardless of the drawbacks associated with the use of a (flat) rotating table to illustrate the Coriolis effect, we see value in using it to make the concept of fictitious forces more intuitive, and it is widely used to this effect.

[ii]Despite their popularity in geophysical fluid dynamics instruction at many institutions, rotating tables might not be readily available everywhere. Good instructions for building a rotating table can, for example, be found on the “weather in a tank” website, where there is also the contact information to a supplier given: http://paoc.mit.edu/labguide/apparatus.html. A less expensive setup can be created from old disk players or even Lazy Susans, or found on playgrounds in form of merry-go-rounds. In many cases, setting the exact rotation rate is not as important as having a qualitative difference between “slow” and “fast” rotation, which is very easy to realize. In cases where a co-rotating camera is not available, by dipping the marble in either dye or chalk dust (or by simply running a pen in a straight line across the rotating surface), the trajectory in the rotating system can be visualized. The instructional approach described in this manuscript is easily adapted to such a setup.

[iii]We initially considered starting the lab session by throwing the marble diametrically across the rotating table.  Students would then see on-screen the curved trajectory of a marble, which had never made physical contact with the table rotating beneath it, and which was clearly moving in a straight line from thrower to catcher, leading to the realization that it is the frame of reference that is to blame for the marble’s curved trajectory. However, the speed of a flying marble makes it very difficult to observe its curved path on the screen in real time. Replaying the footage in slow motion helps in this regard.  Yet, replacing direct observation with recording and playback seemingly hampers acceptance of the occurrence as “real”. We therefore decided to only use this method to further illustrate the concept, not as a first step.

 

Bios

Dr. Mirjam Sophia Glessmer, holds a Master of Higher Education and Ph.D. in physical oceanography. She works at the Leibniz Institute of Science and Mathematics Education in Kiel, Germany. Her research focus lies on informal learning and science communication in ocean and climate sciences.

Pierre de Wet is a Ph.D. student in Oceanography and Climatology at the University of Bergen, Norway, and holds a Master in Applied Mathematics from the University of Stellenbosch, South Africa. He is employed by Akvasafe AS, where he works with the analysis and modelling of physical environmental parameters used in the mooring analysis and accreditation of floating fish farms.

Of timeless relevance: the ESWN mentoring map and how you can provide mentoring to others at any career stage

Me realizing that there are three cameras aimed at me simultaneously at some point during my presentation (Picture: Sara Siebert)

This week I had the honor to be invited to give a talk to a network of PhD students of the three Leibniz institutes in Kiel, which is just forming. Being as big a fan of networking as I am, of course I could not say no to this opportunity, especially since I had a really good resource to share: The Earth Science Women’s Network‘s mentoring map.

The mentoring map is a tool that helps you think about what your mentoring needs are and whether you have a strategy in place to get those needs met. And if you realize you don’t — well, then you might want to read our 2013 chapter to get ideas on what strategies you might want to consider to find intellectual community, sponsors, emotional support, or whatever you just realized you are missing.

Even though during that presentation my focus was on conveying the different kinds of mentoring needs you might have at different points during your PhD journey and beyond, and then on identifying people and resources who might help you meet those needs, one point that I tried to make is that mentoring is not a one-way street. In my experience the best networking advice (and, by building an amazing network around you, also the best advice for how to make sure you have your mentoring needs met) is to pay it forward, to provide to others what you would wish that others provide to you.

Be the kind of person that you would love to have in your own network

This last piece of advice at first sounds like it is really difficult to put into action, and almost unattainable if you are just starting out with your PhD. But it is not. There are so many ways in which you can provide value to others around you, and have that become a habit. A couple of examples, in no particular order:

  • Offer to proof-read other people’s writing. Especially when you are just starting out, forcing yourself to read something really carefully, even though it might not be 100% what you need to be reading for your own research, is a great way to widen your horizon and pick up on what you like and don’t like in texts. And if you have to look up grammar rules to make sure your edits are correct — even better, you just learned something for your own writing!
  • Check in on people, ask how they are doing, and actually listen to their response. Sometimes only one person noticing that something is off makes a huge difference to someone
  • If you come across interesting articles, summer schools, blog posts, twitter profiles, … that remind you of something you talked about with someone or that you think might be interesting to them, just forward it. It takes a couple of seconds on your end, and even if they already got that information through some other route, they will appreciate the thought and effort and are a lot more likely to return the favor next time they see something that might be interesting to you
  • Be open about your own ideas, and always give credit to others if you talk about their ideas in front of others
  • If you have a network of any kind that might be interesting to others, offer to share it with them. Bring them with you to your work so they can meet interesting colleagues over coffee, give them your mom’s phone number because she can give advice on a topic they are struggling with (Danke, Joke, es ist nicht vergessen), send introductory messages for them
  • Similarly, if you have visibility in an area where they are trying to build it, ask them if they would like to write a guest post on your blog, or retweet their tweets to expose your followers to this new and interesting person, or ask them if they want to present a workshop with you
  • Follow up with people! Just sending an email saying “Hi! We met at conference x and talked about y and I just wanted to follow up so we can stay in touch” is so much more than most people do, but it has started an interaction that both of you are more likely to remember than if you never followed up
  • Remember that most people you meet feel at least as awkward about not knowing you as you feel about not knowing them. Just introduce yourself and maybe ask if they would like to have a coffee sometime! If you’ve been in your job for two weeks and feel like the complete newbie, chances are you still know so much more than the person whose first day it is today and they’d be super grateful if you took them under your wing and showed them how to operate the photocopy machine

What else are habits you would recommend people develop so they become the kind of person you would like to have in your own network? Let me know in the comments!

P.S.: Just have to show the pictures below because it makes me proud that there is so much social media activity going on now at my former workplace :-)

Need your help! “Wish list” for a student lab for tank experiments?

I’d love your input: If your student lab for GFD tank experiments had to downsize, but you had to present a “wish list” for a smaller replacement, what would be on that list? Below are my considerations, but I would be super grateful for any additional input or comments! :-)

Background and “boundary conditions”

The awesome towing tank that you have come to love (see picture above) will have to be removed to make room for a new cantina. It might get moved into a smaller room, or possibly replaced all together. Here are some external requirements, as far as I am aware of them:

  • the (new) tank should ideally be movable so the (small) room can be used multi-purpose
  • since the new room is fairly small, people would be happy if the new tank was also smaller than the old one
  • the rotating table is kept (and a second, smaller one, exists in the building)
  • There are other, smaller tanks that will be kept for other experiments, dimensions approximately 175x15x40cm and smaller
  • the whole proposal needs to be inexpensive enough so that the likelyhood that it will actually be approved is moderate to fair ;-)

Here are a couple of things I think need to be definitely considered.

Dimensions of the tank

If the tank was to be replaced by a smaller one, how small could the smaller one be?

The dimension of the new tank depend, of course, on the type of experiment that should be done in the tank. Experiments that I have run in the tank that is to be replaced and that in my opinion should definitely be made possible in the new location/tank include

  1. “Dead water”, where a ship creates internal waves on a density interface (instructions)
  2. Internal lee waves & hydraulic jumps, where a mountain is moved at the bottom of the tank (instructions)
  3. Surface imprints of internal waves (example)
  4. Surface waves (example)
  5. Intrusions (example)
  6. Waves in a density stratification (example)
  7. Surface waves running up on a slope (I haven’t blogged about that yet, movies waiting to be edited)

If we want to be able to continue running these experiments, here is why we should not sacrifice the dimensions of the tank.

Why we need the tank length

The first reason for keeping the length of the tank is that the “mountains” being towed to create the lee waves are already 1 and 1.5m long, respectively. This is a length that is “lost” for actual experiments, because obviously the mountain needs space inside the tank on either end (so in its start and end position). Additionally, when the mountain starts to move, it has to move for some distance before the flow starts displaying the features we want to present: Initially, there is no reservoir on the “upstream” side of the mountain and it only builds up over the first half meter or so.

The second reason for keeping the length of the tank are wave reflections once the ship or mountain comes close to the other side of the tank. Reflected surface waves running against the ship will set up additional drag that we don’t want when we are focussing on the interaction between the ship and the internal wave field. Reflected internal waves similarly mess things up in both experiments

The third reason for keeping the length of the tank is its purpose: as teaching tank. Even if one might get away with a slightly shorter tank for experiments when you just film and investigate the short stretch in the middle of the tank where there are no issues with either the push you gave the system when starting the experiment or the reflections when you get near the end, the whole purpose of the tank is to have students observe. This means that there needs to be a good amount of time where the phenomenon in question is actually present and observable, which, for the tank, means that it has to be as long as possible.

Why we need the tank width

In the experiments mentioned above, with exception of the “dead water” experiment, the tank represents a “slice” of the ocean. We are not interested in changes across the width of the tank, and therefore it does not need to be very wide. However, if there is water moving inside the tank, there will be friction with the side walls and the thinner the tank, the more important the influence of that friction will become. If you look for example at the surface imprint of internal wave experiment, you do see that the flow is slowed down on either side. So if you want flow that is outside of the boundary layers on either side, you need to keep some width.

Secondly, not changing the tank’s width has the advantage that no new mountains/ships need to be built.

Another, practical argument for a wide-ish tank (that I feel VERY strongly about) is that the tank will need to be cleaned. Not just rinsed with water, but scrubbed with a sponge. And I have had my hands inside enough tanks to appreciate if the tank is wide enough that my arm does not have to touch both sides at all times when reaching in to clean the tank.

Why we need the tank depth

The first reason for keeping the height is that for the “dead water” experiment, even the existing tank is a lot shallower than what we’d like from theory (more here). If we go shallower, at some point the interactions between the internal waves and the ground will become so large that it will mess up everything.

Another reason for keeping the depth is the “waves running up a slope” experiment. If you want waves running up a slope (and building up in height as they do), you have the choice between high walls of the tank or water spilling. Just sayin’…

And last not least: this tank has been used in “actual” research (rather than just teaching demonstrations, more on that on Elin’s blog), so if nothing else, those guys will have thought long and hard about what they need before building the tank…

Historical images of research on internal lee waves being done with the tank

Without getting too philosophical here about models and what they can and cannot achieve (and tank experiments being models of phenomena in the ocean), the problem is that scaling of the ocean into a tiny tank does not work, so “just use a mountain/boat half the size of the existing ones!” is actually not possible. Similarly to how if you build the most amazing model train landscape, at some point you will decide that tiny white dots are accurate enough representations of daisies on a lawn, if you go to a certain size, the tank will not be able to display everything you want to see. So going smaller and smaller and smaller just does not work. A more in-depth and scientific discussion of the issue here.

Other features of the tank

When building a new tank or setting up the existing tank in a new spot, there are some features that I consider to be important:

  • The tank needs a white, intransparent back wall (either permanently or draped with something) so that students can easily focus on what is going on inside the tank. Tank experiments are difficult to observe and even more difficult to take pictures of, the better the contrast against a calm background, the better
  • The tank should be made of glass or some other material that can get scrubbed without scratching the surface. Even if there is only tap water in the tank, it’s incredible how dirty tanks get and how hard they have to be scrubbed to get clean again!
  • The tank needs plenty of inlets for source waters to allow for many different uses. With the current tank, I have mainly used an inlet through the bottom to set up stratifications, because it allowed for careful layering “from below”. But sometimes it would be very convenient to have inlets from the side close to the bottom, too. And yes, a hose could also be lowered into the tank to have water flow in near the bottom, but then there needs to be some type of construction on which a hose can be mounted so it stays in one place and does not move.
  • There needs to be scaffolding above the tank, and it needs to be easily modifiable to mount cameras, pulleys, lights, …
  • We need mechanism to tow mountains and ships. The current tank has two different mechanisms set up, one for mountains, one for ships. While the one for the ship is home-made and easily reproducible in a different setting (instructions), the one to tow the mountain with is not. If there was a new mechanism built, one would need to make sure the speeds at which the mountain can be towed matches the internal wave speed to be used in the experiment, which depends on the stratification. This is easy enough to calculate, but it needs to be done before anything is built. And the mechanism does require very securely installed pulleys at the bottom of the tank which need to be considered and planned for right from the start.

“Source” reservoirs

The “source” reservoirs (plural!) are the reservoirs in which water is prepared before the tank is filled. It is crucial that water can be prepared in advance; mixing water inside the tank is not feasible.

There should be two source reservoirs, each large enough to carry half the volume of the tank. This way, good stratifications can be set up easily (see here for how that works. Of course it works also with smaller reservoirs in which you prepare water in batches as you see below. But what can happen then is that you don’t get the water properties exactly right and you end up seeing stuff you did not want to see, as for example here, which can mess up your whole experiment)

Both reservoirs should sit above the height of the tank so that the water can be driven into the tank by gravity (yes, pumps could work, too, more on that below).

“Sink” reservoir

Depending on the kind of dyes and tracer used in the water, the water will need to be collected and disposed of rather than just being poured down the drain. The reservoir that catches the “waste” water needs to

  • be able to hold the whole volume of the tank
  • sit lower than the tank so gravity will empty the tank into the reservoir (or there needs to be a fast pump to empty the tank, more on that below)
  • be able to be either transported out of the room and the building (which means that doors have to be wide enough, no steps on the way out, …) or there needs to be a way to empty out the reservoir, too
  • be able to either easily be replaced by an empty one, or there needs to be some kind of mechanism for who empties it within a couple of hours of it being filled, so that the next experiment can be run and emptied out

If the waste water is just plain clear tap water, it can be reused for future experiments. In this case, it can be stored and there need to be…

Pumps

If reservoirs cannot be located above and below tank height to use gravity to fill and empty the tanks, we need pumps (plural).

  • A fast pump to empty out the tank into the sink reservoir, which can also be used to recycle the water from the sink reservoir into the source reservoirs
  • One pump that can be regulated very precisely even at low flow rates to set the inflow into the tank
  • Ideally, a second pump that can be regulated very precisely, so the double bucket method of setting up a stratification in a tank can be done automated rather than relying on gravity.

Preferable the first and the latter are not the same, because changing settings between calibrating the pump for an experiment, setting it on full power to empty the tank, and calibrating it again will cause a lot of extra work.

Inlets for dyes

Sometimes it would be extremely convenient if there was a possibility to insert dyes into the tank for short, distinct periods of time during filling to mark different layers. For this, it would be great to be able to connect syringes to the inlet

Hoses and adapters

I’ve worked for years with whatever hoses I could find, and tons of different adapters to connect the hoses to my reservoir, the tap, the tank. It would be so much less of a hassle if someone thought through which hoses will actually be needed, bought them at the right diameter and length, and outfitted them with the adapters they needed to work.

Space to run the experiment

The tank needs to be accessible from the back side so the experimenter can run the experiment without walking in front of the observers (since the whole purpose of the tank is to be observed by students). The experimenter also needs to be able to get out from behind the tank without a hassle so he or she can point out features of interest on the other side.

Also, very importantly, the experimenter needs to be able to reach taps very quickly (without squeezing through a tight gap or climbing over something) in case hoses come loose, or the emergency stop for any mechanism pulling mountains in case something goes wrong there.

Space for observers

There needs to be enough room to have a class of 25ish students plus ideally a handful of other interested people in the room. But not only do they need to fit into the room, they also need to be able to see the experiments (they should not have to stand in several rows behind each other, so all the small people in the back get to see are the shoulders of the people in front). Ideally, there will be space so they can duck down to have their eyes at the same height as the features of interest (e.g. the density interface). If the students don’t have the chance to observe, there is no point of running an experiment in the first place.

Filming

Ideally, when designing the layout of the room, it is considered how tank experiments will be documented, i.e. most likely filmed, and there needs to be space at a sufficient distance from the tank to set up a tripod etc..

Lighting

Both for direct observations and for students observing tank experiments, it is crucial that the lighting in the room has been carefully planned so there are minimal reflections on the walls of the tank and students are not blinded by light coming through the back of the tank if a backlighting solution is chosen.

Summary

In my experience, even though many instructors are extremely interested in having their students observe experiments, there are not many people willing to run tank experiments of the scale we are talking about here in their teaching. This is because there is a lot of work involved in setting up those experiments, running them, and cleaning up afterwards. Also there are a lot of fears of experiments “going wrong” and instructors then having to react to unexpected observations. Running tank experiments requires considerable skill and experience. So if we want people using the new room and new tank at all, this has to be made as easy as possible for them. Therefore I would highly recommend that someone with expertise in setting up and running experiments, and using them in teaching, gets involved in designing and setting up the new room. And I’d definitely be willing to be that person. Just sayin’ ;-)

“Continue. Start. Stop.”. An article supporting the usefulness of my favourite method of asking for student feedback on a course!

I’ve been recommending the “Continue. Start. Stop.” feedback method for years an years (at least since my 2013 blog post), but not as a research-backed method but mostly based on my positive personal experience with it. I have used this method to get feedback on courses I’ve been teaching a couple of weeks into the course in order to improve my teaching both within the course as well as over the years. If there was anything that students thought would improve their learning, I wanted to be able adapt my teaching (and also, in a follow-up discussion of the feedback, be able to address student expectations that might not have been explicit before that I might or might not want to follow). I like that even though it’s a qualitative method and thus fairly open, it gives students a structure along which they can write their feedback. Also by asking what should be continued as well as stopped and started, it’s a nice way to get feedback on what’s already working well, too! But when I was asked for a reference for the method today, I didn’t really have a good answer. But then I found one: an article by Hoon et al. (2015)!

Studies on the “continue. start. stop.” feedback vs open feedback

In the first study in the article, two different feedback methods are compared over three different courses: a free form feedback and a structured format, similar to “continue. start. stop.”. From this study, the authors draw pointers for changing the feedback method in the free form course to a more structured feedback. They investigate the influence of this change in a second study.

In that second study, the authors find that using a structured feedback led to an increasing depth of feedback, and that the students liked the new form of giving feedback. They also find indications that the more specific the questions are, the more constructive (as compared to more descriptive texts in the open form; not necessarily more positive or negative!) the feedback is.

My recommendations for how to use the “continue. start. stop.” feedback

If anything, this article makes me like this feedback method even more than I did before. It’s easy and straight forward and actually super helpful!

Use this as formative feedback!

Ask for this feedback early on in the course (maybe after a couple of weeks, when students know what to expect in your course, but with plenty of the course left to actually react to the feedback) and use the student replies to help you improve your teaching. While this method can of course also be used as summative feedback at the end of the course, how much cooler is it if students can benefit from the feedback they gave you?

Ask full questions

One thing that I might not have been clear about before when talking about the “continue. start. stop.” feedback method is that it is important to actually use the whole phrases (“In order to improve your learning in this course, please give me feedback on the following points

  1. Continue: What is working well in this course that you would like to continue?
  2. Start: What suggestions do you have for things that could improve the course?
  3. Stop: What would you like us to stop doing?”

or similar) rather than just saying “continue. start. stop.” and assuming the students know what that means.

Leave room for additional comments

It is also helpful to give an additional field for other comments the students might have, you never know what else they’d like to tell you if only they knew how and when to do it.

Use the feedback for several purposes at once!

In the article’s second study, a fourth question is added to the “continue. start. stop.” method, and that is asking for examples of good practice and highlights. The authors say this question was mainly included for the benefit of “external speakers who may value course feedback as evidence of their own professional development and engagement with education”, and I think that’s actually a fairly important point. While the “continue. start. stop.” feedback itself is a nice addition to any teaching portfolio, why not think specifically about the kind of things you would like to include there, and explicitly ask for them?

Give feedback on the feedback

It’s super important that you address the feedback you got with your class! Both so that they feel heard and know whether their own perception and feedback agrees with that of their peers, as well as to have the opportunity to discuss what parts of their suggestions you are taking on, what will be changing as a result of their suggestions, and what you might not want to change (and why!). If this does not happen, students might not give you good feedback the next time you ask for it because they feel that since it didn’t have an effect last time, why would they bother doing it again?

Now it’s your turn!

Have you used the “continue. start. stop.” method? How did it work for you? Will you continue using it or how did you modify it to make it suit you better? Let me know in the comments below! :-)

Reference:

Hoon, A. and Oliver, E.J. and Szpakowska, K. and Newton, P. (2015) ‘Use of the ‘Stop, Start, Continue’ method is associated with the production of constructive qualitative feedback by students in higher education.’, Assessment and evaluation in higher education., 40 (5). pp. 755-767. [link]

Taking ownership of your own mentoring

Have you ever had questions related to your career development that you didn’t know who to ask for answers for? Or have you ever felt that you would probably profit from having a mentor, but didn’t know who that mentor could be? Or do you have a great mentor but wonder whether you might be relying too heavily on him or her? Then this post is for you!

(This post, and the article referenced at the bottom, are heavily inspired by the work of Kerry Ann Rockquemore, especially this post, and workshops she gave for the Earth Science Women’s Network.)

So. Let’s get started. Do you even know what your current mentoring needs are? In the image below we suggest different kinds of mentoring needs that you will probably all encounter throughout your career, hopefully not all at the same time.

It is really helpful to try and identify a person for each of those fields that might possibly be able to help. If you fill out the blank spaces in the graphic below now, before you actually urgently need someone to fill a specific role, it’ll be very valuable once the time comes!

Mentoring_map_01

A “mentoring map” to help you identify your mentoring needs as well as who might be able to fill those needs.

If you aren’t quite sure what each of the fields above contains, the image below might give you ideas:

Mentoring_map_02

Mentoring map. What exactly are your mentoring needs?

And now that you know what your needs are, how do you actually identify possible mentors for each category? We give some ideas in the image below!

Mentoring_map_03

Mentoring map and where to find possible mentors for the different mentoring needs

Do you feel like you are taking unfair advantage of your mentors? Then maybe think about paying it forward. Be a sponsor to the student that stands out in your class and recommend her for a scholarship. Be the safe space your friend needs. Give substantial feedback on your office mate’s paper. Even if you feel you are nowhere near ready to “be someone’s mentor”, that is probably not true. Give back when the opportunity arises, and don’t feel bad to ask for the mentoring you need!

For more details, check out our article:

Glessmer, M.S., A. Adams, M.G. Hastings, R.T. Barnes, Taking ownership of your own mentoring: Lessons learned from participating in the Earth Science Women’s Network, published in The Mentoring Continuum: From Graduate School Through Tenure, Syracuse University Graduate School Press, ed. Glenn Wright, 2015.

Pdf of the chapter here.

P.S.: This text originally appeared on my website as a page. Due to upcoming restructuring of this website, I am reposting it as a blog post. This is the original version last modified on November 4th, 2015.

I might write things differently if I was writing them now, but I still like to keep my blog as archive of my thoughts.

Enabling backchannel communication between a lecturer and a large group

Using technology to enable active engagement with content in a large lecture.

In 2014, I presented the paper “Enabling backchannel communication between a lecturer and a large group” at the SEFI conference in Birmingham. That paper is based on work that I have done with two colleagues – the instructor of a large lecture, and the teaching assistant at the time.

Now if oceanographers hear something about “large lectures”, they typically envision a couple dozen students. In this case, it was a couple of hundred students in a lecture theatre that sits about 700.

The challenge

When sitting in on the class the year before, I noticed that there were a lot of questions that students were discussing around me that never made it to the instructor’s attention. This is not very surprising given the large number of students and that there were only two instructors in the room. But when talking about it afterwards, we decided that we wanted to find a way to channel student questions to make sure they reached the instructor. The “backchannel” was born.

We met up to discuss our options. It became clear very quickly that even though there are a lot of nice methods out there to invite feedback of the sort we wanted (for example through “muddiest point” feedback), this was not feasible with the number of students we were dealing with. So instead we decided to go for an online solution.

Twitter has been propagated for use in instruction for a while, and there are many other tools out there that enable backchannel communication. But we realized that we had very specific requirements which none of the existing tools were meeting simultaneously:

  • anonymous communication, to keep the threshold as low as possible
  • no special hardware or software requirements
  • easy to use
  • communication student to instructor, but not student-student
  • possibility of moderation

The solution

 In the end, Patrick coded a “backchannel” tool that could do all that. On a webpage, students enter text in a text field. They click a button to submit the text, and a moderator then, in real time, decides whether to forward the text to the instructor. The instructor then gets the text on a screen and can decide whether and when to incorporate it in their teaching.
We’ve found that this works really well from an operational point of view. The instructor has been really happy with the quality of questions he has been getting, and sometimes students even send links that they think should be shared with the class.

Students seem to like it, too, even though they aren’t engaging with the tool as much as we had anticipated. But there are a couple of reasons for that which we all name in our paper. Ultimately, we liked the tool enough to continue using it this year. The new semester has just started, so let’s see how it goes!

Thanks to my co-authors for a very interesting and enjoyable collaboration!

Enabling backchannel communication between a lecturer and a large group
M.S. Glessmer, M.-A. Pick and P. Göttsch
In Proceedings of the 42nd SEFI Conference. Birmingham, UK (2014)
http://www.sefi.be/conference-2014/0101.pdf

P.S.: This text originally appeared on my website as a page. Due to upcoming restructuring of this website, I am reposting it as a blog post. This is the original version last modified on November 4th, 2015.

I might write things differently if I was writing them now, but I still like to keep my blog as archive of my thoughts.

Outreach activity: How do we make climate predictions?

This text was written for GeoEd, the education column of EGU’s blog, and first appeared there on Nov 27th, 2015.

In my second year studying physical oceanography, I got a student job in an ocean modelling group. When I excitedly told my friends and family about said job, most of them did not have the slightest idea what I might be doing. Aside from the obvious and oh-so-funny “you are a model now?!”, another common reaction was “modelling – with clay?” and the picture in those people’s head was that of an ocean model resembling the landscape in a miniature train set, except under water. And while there are many groups seeking to understand the ocean by using simplified versions of the ocean or ocean regions, simplified geometries, selected forcings acting on it, etc – this is not the kind of model I was supposed to be working with.

Talking about climate models with the general public

Explaining to a laymen audience what a climate model is a daunting task. We have all seen the images of a region divided into smaller and smaller squares as a visualization of boxes which represent a grid on which a set of differential equations is solved, yielding a solution for each of the boxes (See Figure 1). But do we really expect everybody we show this to grasp the idea of how this might help to understand climate if they don’t have the background to understand what a differential equation is, let alone how it has been discretised and programmed and is now being solved? From my experience it is very difficult to keep people interested and captivated using this approach and, unless they already have a pretty solid background, it is unlikely they will actively engage in the topic and ask clarifying questions.

Image01_cropped

Figure 1: Modelled sea surface temperature of the ocean off Mauritania, North-West Africa. Depending on the model resolution, smaller and smaller features in the sea surface temperature are resolved by the model. Still, even the most complex model is still nowhere near as complex as reality.

A new approach: Let them experience the process of building a model!

I therefore suggest we use a different approach. Instead of concentrating on explaining the mechanics of an ocean model, let us focus on letting people experience the idea behind it by using a “mystery tube” to represent the climate (or whatever process we want to model) and have the audience build their own “models”.

The mystery tube is all over the internet. I have not been able to find the original source but let’s look at what it is:

Basically, we have a tube that is closed off at the top and at the bottom (See Figure 2). Four pieces of string come out of it. When you pull one out, another one gets pulled into the tube. So far, so good. But the pattern of which string gets pulled in when another one gets pulled out suggests that there is something more going on inside the tube than just two pieces of string going in on one side and coming out at the other. So, how do we figure out what is going on? Some of you may have already seen a possible solution to the problem. Others might find one as soon as they’ve gotten their hands on a mystery tube and pulled on the strings a couple of times. Others might need their own tube and pieces of string to play around with before they are reasonably confident that they have an idea of how the mystery tube works.

Image02

Figure 2: A very non-fancy mystery tube: A paper kitchen towel roll with two pieces of curly ribbon going through. But what goes on inside? Still a mystery!

If you were to use mystery tubes in outreach (or with your friends and family, or – always a hit – with your colleagues), it is in fact a good idea to have a couple of “blank” tubes and pieces of string ready and let everyone have a go at building their own mystery tube that reproduces the functionality of the original one. Ideally, as you will see below, you would have more than just the bare necessities ready and also offer flat washers, springs, paper clips or any other distracting material that might or might not be inside the mystery tube.

Why offer “distractor” materials? Because we are trying to understand how people come up with climate models, remember? The original mystery tube represents the process we want to model. We do not know for sure all the important components of that process, and therefore do not know what needs to be included in the model, either.

— SPOILER BELOW! If you want to solve the mystery tube mystery yourself, do not read on! —

Now, in the instructions on the internet the two pieces of string are connected inside the tube by way of a ring through which they are both fed. When I first build my own mystery tube, I was too lazy to search for a ring to connect the pieces of string, so I just crossed the two threads over. After all, the ring wouldn’t be visible in the final product, and the function would remain the same anyway!

From empty cardboard kitchen towel rolls to climate models

Which brings me to the main point of this blog post, first made by my friend and fellow outreach enthusiast, Dr. Kristin Richter (http://kristinrichter.info, currently University of Innsbruck, Austria), who is always my first stop when wanting to bounce ideas for demonstrations or experiments off: This is exactly why modelling climate is so difficult! We can build a perfectly working mystery tube but unless we cut open the original one we will never know whether our solution is the same as the one in the original mystery tube, i.e. whether there is a ring inside, or a paper clip, or the two pieces of string are just crossed.

You might argue we could find out what is inside the original mystery tube by other means, for example by shaking it and listening for rattling, by weighing it, or by many other methods. Yet, can we ever be sure we know exactly what is inside? And more importantly, would we even think of shaking or weighing the mystery tube if we weren’t specifically looking for what connects the two pieces of string? And are we really sure we are reproducing the full functionality of the original mystery tube? Maybe the original ring has a blade on the inside, so after a certain number of experiments one of the strings will be cut? Or maybe there is something else inside that will happen eventually, but that we cannot yet predict because our mystery tube, while reproducing what we observed from the original tube, just does not include that element.

The same goes for climate models, of course. We can reproduce what we observe reasonably well. Assuming we know of all “parts” of the climate and how they work together, we can make a prediction. But the climate is a lot more complex than a mystery tube. Of course, climate models are based on physical principles and laws and not just best fits to observations. Yet, in many places decisions have to be made for or against including details, or for representing them by one parameterisation and not another.

Can we ever know for sure what the future will bring?

So does that mean we should give up on making models of the climate because, while we might be able to reproduce the status quo, prediction is impossible? Absolutely not! But we need to be aware of the possibility of feedback mechanisms that might become important once a threshold has been crossed or tipping points (like when a hypothetical blade inside the ring will have cut through one of the pieces of string). If we are aware that there might be more to the mystery tube than just the pattern of how strings move which we observed at the beginning of this post, we can watch out for signs of other components. Like listen intently to the noise the string makes when gliding through the mystery tube, or listening for rattling when you shake the tube, or monitor the strings for wear indicating there might be a hidden sharp edge somewhere.

And the same obviously goes for climate. We need to monitor all observations and look closely at any deviation of the observations from our model. We need to come up with ideas of processes, which might become important under different conditions and look out for signs that they might already start to occur. We need to be aware that processes we haven’t seen evidence for yet might still be important at a different parameter range.

Once we have gone through all this with our audience, I bet they have a better idea of what a modeller does – even though they still might not have a clue what that means for the average day at work. But typically, people find the mystery tube intriguing, and you should definitely be prepared to answer a lot of questions about what your model does, how you know whether it is right, what processes are included and what are not, and voilà! We are talking about how to make climate predictions.

P.S.: This text originally appeared on my website as a page. Due to upcoming restructuring of this website, I am reposting it as a blog post. This is the original version last modified on November 27th, 2015.

I might write things differently if I was writing them now, but I still like to keep my blog as archive of my thoughts.

Four steps to great hands-on outreach experiences

Part 1 and 2 of this post were first posted on the EGU’s blog on Jan 29, 2016, and Feb 29, 2016, respectively.

Part 1 gives four steps to outreach activities, part 2 uses an example to further illustrate those four steps.

Part 1: For the best hands-on outreach experiences, just provide opportunities for playing!

 

“For the best hands-on outreach experiences, just provide opportunities for playing!” I claim. Seriously? You wonder. We want to spark the public’s curiosity about geosciences, engage the public in thinking about topics as important as sea level rise or ocean acidification, and provide learning experiences that will enable them to take responsibility for difficult decisions. And you say we should just provide opportunities for them to play?

Yes. Hear me out. Playing does not necessarily equal mindlessly killing time. Kids learn a lot by playing, and even grown ups do. But if you prefer, we can use the term “serious play” instead of just “play”. Using the term “serious play” makes it clear that we are talking about “improvising with the unanticipated in ways that create new value”, which is exactly what outreach should be doing: getting people intrigued and wanting to understand more about your topic.

So how would we go about if we wanted to create outreach activities which gave the public opportunity to play in order to lure them into being fascinated by our field of science? There are several steps I recommend we take.

  1. Identify the topic nearest and dearest to your heart

Even if your aim is to educate the public about climate change or some other big picture topic, pick the one element that fascinates you most. If you are really fascinated by what you are showing, chances are that the excitement of doing the activity will carry over to your audience. Plus, once you have this really great activity, you will likely be asked to repeat it many times, so you had better pick one that you love! J

Me, I am a physical oceanographer. I care about motion in the ocean: Why and how it happens. Consequently, all of my outreach activities have people playing with water. Sometimes at different temperatures, sometimes at different salinities, sometimes frozen, sometimes with wind, but always with water.

  1. Find an intriguing question to ask

Questions that intrigue me are, for example, “do ice cubes melt faster in fresh water or in salt water?”, “how differently will ice look when I freeze salt water instead of fresh water?” or “what happens if a stratification is stable in temperature and unstable in salt?”. Of course, all these questions are related to scientific questions that I find interesting, but even without knowledge of all the science around them, they are cool questions. And they all instantly spark follow-up questions like “what would happen if the ice cubes weren’t floating, but moored to the ground?”, “what if I used sugar instead of salt?”, “wait, does the food dye influence what happens here?”. And all of those questions can be investigated right then and there. As soon as someone asks a question, you hand them the materials and let them find the answer themselves. That is why we talk about hands-on outreach activities and not demonstrations: It is about actively involving everybody in the exploration and wonder of doing scientific experiments!

  1. Test with family, friends and colleagues

Many, if not all, the outreach activities I am using and promoting have been tested on family, friends and colleagues before. You know that you have found an intriguing question when your friends sacrifice the last bit of red wine they brought at a Norwegian mountain cabin, to use as stand in for food dye in an experiment you just told them about, because they absolutely have to see it for themselves!

By the way, this is always good to aim at with outreach activities: always try to keep them easy enough to be recreated at a mountain cabin, in your aunt’s kitchen, at the beach or anywhere anyone who saw it or heard about it wants to show their friends. People might occasionally have to get a little creative to replace some of the materials, but that’s part of the charm and of the inquiry we want!

  1. Bring all the materials you need, and have fun!

And then, finally, Just Do It! Bring all your materials and start playing and enjoying yourself!

But now they can play with water and dye. That doesn’t mean they understand my research!

True, by focussing on a tiny aspect you won’t get to explain the whole climate system. But you will probably change the mindset of your audience, at least a little bit. Remember, you studied for many years to come to the understanding you have now, it is not a realistic expectation to convey all that in just one single outreach occasion. But by showing how difficult it is to even understand one tiny aspect (and how much there is still to discover), they will be a lot more likely to inquire more in the future, they will ask better questions (to themselves or to others) and they will be more open to learning about your science. Your activity is only the very first step. It’s the hook that will get them to talk to you, to become interested in what you have to say, to ask questions. And you can totally have backup materials ready to talk in more depth about your topic!

But what if it all goes horribly wrong during my activity?

The good thing is that since you are approaching the whole hands-on outreach as “get them to play!” rather then “show them in detail how the climate system works”, there really isn’t a lot that can go wrong. Yes, you can mess up and the experiment can just not show what you wanted to show. But every time I have had that happen to me, I could “save” the situation by engaging the participants in discussing how things could work better, similar to what Céline describes. People will continue to think about what went wrong and how to fix it, and will likely be even more intrigued than if everything had worked out perfectly.

But what if I am just not creative enough to come up with new ideas?

First, I bet once you start playing, you will come up with new ideas! But then of course, we don’t need to always create outreach activities from scratch. There are many awesome resources around. EGU has its own large collection in the teacher’s corner. And of course, Google (or any websearch of your choice) will find a lot. And if you were interested in outreach activity in physical oceanography specifically, you could always check out my blog “Adventures in Oceanography and Teaching”. I’m sure you’ll find the one activity that you will want to try yourself on a rainy Sunday afternoon. You will want to show your friends when they comes over to visit, and you’ll tell your colleagues about it. And there you are – you found your outreach activity!

 

Part 2: One example of how playing works in outreach activities!

 

In part 1, I talked about hands-on outreach in very general terms, and identified four steps to great outreach. Today, I want to talk about those four steps in more detail, using one of my favourite outreach activities as an example.

Step 1. Identify the topic nearest and dearest to your heart

Me, I am a physical oceanographer. I care about motion in the ocean: Why and how it happens. Consequently, all of my outreach activities have to do with water. Sometimes at different temperatures, sometimes at different salinities, sometimes frozen, sometimes with wind, sometimes with ships, but always with water.

Today, let’s concentrate on thermohaline circulation as the topic we want to get people interested in. That sounds like a lot, so lets break it down: we want to know how oceanic circulation is influenced by both heat and salt in the ocean. To boil this down to one short activity, let’s take away the ocean (and with that all the complicating influences of Earth’s rotation, or topography of ocean basins) and only look at what heat and salt do with water in a tank. In fact, let us focus on different temperatures at first. The easiest way to do this is to introduce water of one temperature into a volume at a different temperature, this way we don’t have to deal with the heating or cooling processes.

Introducing water can mean pouring it into the larger tank, which will lead to some kind of stratification (provided your temperatures are different enough). In order to see the stratification, it always helps to have food dye in the water you are introducing (always put food dye in the smaller volume of water, makes it a lot easier to see the contrast!). To make things most interesting, it might be nice to show two cases simultaneously: pouring hot water and cold water into a lukewarm tank. And, since we see that the hot water forms a layer on top of the lukewarm water and the cold water at the bottom, wouldn’t it be much more fun to introduce them both somewhere at medium height and see what happens?

2_Slide1

Two bottles, one filled with hot water (dyed red) and one filled with cold water (dyed blue) in a larger container of lukewarm water.

Step 2. Find an intriguing question to ask

Depending on who you want to reach as your main audience, you might need to ask different questions. For some audiences, the focus needs to clearly be on your activity’s connection to climate. For other audiences, the questions can be a simple “Wow, that looks weird. Can you figure out what is going on here?”. Depending on the context I was doing my activity in, I could for example ask:

  • Why is the bottle with the red water “pouring up”? The audience I might ask this question are for example kids in a school setting that I am wanting to get excited in science in general. 2_Slide2
  • How can I fill the green cup with hot water without touching it? Audience here could be the general public at a science fair, and if someone manages to fill the green cup, they win a sticker. This questions definitely makes people want to give it a try!2_Slide3
  • What can these fingers tell us about how water mixes in the ocean? This question is for an audience that already knows a lot about the ocean and physical processes in it, for example university students, or a very interested general public.2_Slide4
  • In the subtropical gyres you have a strong salinity stratification. How can nutrients get to the surface ocean? This question is closely related to the one before, but here the element of play isn’t as prominent. So this would be for an audience that knows a lot about ocean physics and biogeochemistry already, like university students or even colleagues at scientific conferences.2_Slide5
  • What drives global ocean currents? This is again a question that you might ask the general public since on one hand not a lot of knowledge about ocean physics is required, and it is on the other hand very easy to see the connection between your activity and the ocean.

    2_Slide6

    Map modified after free-world-maps.com

Step 3. Test with family, friends and colleagues

This step is important for several reasons.

First, you want to work out (most of) the kinks in the activity before using it in front of a large audience. This includes

  • knowing what kind of materials you actually need to run it (For example, I tend to forget that I not only need large containers of water that are prepared at the right temperatures and salinities for several repeats of the experiment, but that in order to set up the experiment for repeats, I need somewhere to get rid of the water from previous experiments),
  • seeing people get really excited about the activity (which is a good memory to calm you down when you get nervous about doing the activity in public for the first time), or, if the aren’t, a good time to tweak the activity a little.
Step 4. Bring all the materials you need, and have fun!

And there you are – ready to do your outreach activity! For your big day, this is what I would recommend:

  • It sounds lame, but you should have a good packing list that includes not only stuff that you need to run the activity, but also stuff that you need to store stuff in on your way home, when everything is wet and full of food dye.
  • If you are about to play with a lot of food dye or other staining substances, consider not wearing your favourite pair of white jeans. Consider also whether your scarf will be constantly hanging in your water tank getting wet, and whether your hair might get caught somewhere.
  • Bring a friend to do the activity with you. It’s more fun, and it really takes away a lot of stressors if there are two people there (Run out of water? No worries, one of you can run and fetch more water while the other talks to people who still want to know what is going on. Question you have no idea how to answer? She will know, or you can look it up together later. Need the loo? How great is it that you don’t have to pack all your stuff and take it with you? ;-))
  • Have someone you know for sure is interested in your activity show up early on to look at it and talk to you about it. Nothing makes it easier for other people to approach and join you in your conversation and activity as someone who is already there and obviously excited. (You can also use your friend mentioned above to play this role until things get going)
  • Bring “backup materials”. Even if your activity is only very vaguely related to your research, bring a current poster of your research (maybe not the A0 version, but A3 or A4) and anything you typically show when talk about your research (Maps? Figures? Instrumentation?). When you get talking to people, chances are you will get talking about how your activity is related to bigger research questions, and you will want to be able to talk about them.
  • And bring a different kind of “backup materials”: Bring pictures and/or movies of your experiment to show what it should have looked like in case the freezer that was supposed to have turned your ice cube tray full of water into ice cubes over night turns out to be a cold room.
  • Take pictures. This one is super important, and I always forget about it in the heat of the moment. You constantly need that picture with you and a bunch of kids looking at your activity for grant proposals or for end-of-year reports!
  • Last but not least: Have fun and take this as a great opportunity to play! Discover features in your activity that you have never noticed before, and, together with your audience, “improvise with the unanticipated in ways that create new value” – I guarantee that it will happen!

Do you have stories of your outreach to share? Any experiments we should all know about? I’d love to hear from you, please leave a comment below!

P.S.: This text originally appeared on my website as a page. Due to upcoming restructuring of this website, I am reposting it as a blog post. This is the original version last modified on February 1st, 2016.

I might write things differently if I was writing them now, but I still like to keep my blog as archive of my thoughts.

Experiment: Demystifying the Coriolis force

Mirjam S. Glessmer & Pierré D. de Wet

Abstract

Even though experiments – whether demonstrated to, or personally performed by students – have been part of training in STEM for a long time, their effectiveness as an educational tool are sometimes questioned. For, despite students’ ability to produce correct answers to standard questions regarding these laboratory exercises, probing deeper often reveals a lack of conceptual understanding.

One way to help students make sense of experiments is to use them in combination with an elicit-confront-resolve approach. With this approach, before the experiment demonstrating a specific concept is run, students are asked to discuss the expected outcome in groups. In so doing, should (specific) misconceptions be harbored about the underlying concept, these are elicited. Incorrect student feedback (feedback illustrating that a misconception is present) is not corrected at this stage. As the demonstration plays out, a mismatch between observation and hypothesis confronts students with their misconceptions. Finally, repetition of the experiment and peer discussion as well as discussion with the instructor lead to resolving of the misunderstandings.

Here, we apply the elicit-confront-resolve approach to a standard demonstration in introductory dynamics, namely the interplay of a rotating frame of reference, movement of particles observed from outside that frame of reference and the resulting fictitious forces. The efficacy of the elicit-confront-resolve approach for this purpose is discussed. Additionally, recommendations are given on how to modify instruction to further aid students in interpreting and understanding their observations.

Key words

Coordinate system, frame of reference, fictitious force, hands-on experiment, elicit-confront-resolve

Introduction

In many STEM disciplines, demonstrations and hands-on experimentation have been part of the curriculum for a long time. However, whether students actually learn from watching demonstrations and conducting lab experiments, and how their learning can be best supported by the instructor, is under dispute (Hart et al, 2000). There are many reasons why students might fail to learn from demonstrations (Roth et al, 1997). For example, separating the signal to be observed from the inevitable noise can be difficult, and inference from other demonstrations might hinder interpretation of a specific experiment. Sometimes students even “remember” witnessing outcomes of experiments that were not there (Milner-Bolotin, Kotlicki, and Rieger (2007)).

Even if students’ and instructors’ observations were the same, this does not guarantee congruent conceptual understanding and conceptual dissimilarity may persist unless specifically treated. However, helping students overcome deeply rooted notions is not simply a matter of telling them which mistakes to avoid. Often they are unaware of the discrepancy between the instructors’ words and their own thoughts (Milner-Bolotin, Kotlicki, and Rieger (2007)).

One way to address misconceptions is by using an elicit-confront-resolve approach (McDermott, 1991). Posner et al. (1982) suggested that dissatisfaction with existing conceptions, which in this method is purposefully created in the confront-step, is necessary for students to make major changes in their concepts. As shown by Kornell (2009), this approach enhances learning by confronting the student with their lack of an answer to a posed question. Similarly, Muller et al. (2007) find that learning from watching science videos is improved if those videos present and discuss common misconceptions, rather than just presenting material textbook-style.

In this article we look at how an elicit-confront-resolve approach can further student engagement and learning. This is done by using a typical introductory demonstration in geophysical fluid dynamics, namely the effect of rotation on the movement of a ball as seen from within and from outside the rotating system. The motivation for the choice of experiment is dual: the rising popularity of rotating tables in undergraduate oceanography instruction (Mackin et al, 2012), and the difficulties students display in anticipating the movement of an object on a rotating body when they themselves are not part of the rotating system.

 

The Coriolis force as example for the instructional method

On a rotating earth, all large-scale motion is subject to the influence of the fictitious Coriolis force, and without a solid understanding of the Coriolis force it is impossible to understand the movement of ocean currents or weather systems. Furthermore, the Coriolis force forms an important part of classical oceanographic theories, such as the Ekman spiral, inertial oscillations, topographic steering and geostrophic currents. A thorough understanding of the concept of fictitious forces and observations in rotating vs. non-rotating systems is thus essential in order to gain a deeper understanding of these systems. Therefore, most introductory books on oceanography, or more generally geophysical fluid dynamics, present the concept in some form or other (cf. e.g. Cushman-Roisin (1994), Gill (1982), Pinet (2009), Pond and Pickard (1983), Talley et al. (2001), Tomczak and Godfrey (2003), Trujillo and Thurman (2013)). Yet, temporal and spatial frames of reference have been described as thresholds to student understanding (Baillie et al., 2012).

The frame of reference is the chosen set of coordinate axes relative to which the position and movement of an object is described. The choice of axes is arbitrary and usually made such as to simplify the descriptive equations of the object under regard. Any object can thus be described in relation to different frames of reference. When describing objects moving on the rotating Earth, the most commonly used frame of reference would be fixed on the Earth (co-rotating), so that the motion of the object is described relative to the rotating Earth. Alternatively, the motion of the same object could be described in an inert frame of reference outside of the rotating Earth. Even though the movement of the object is independent of the frame of reference used to describe it, this independence is not immediately apparent. Objects moving on the rotating Earth seemingly experience a deflecting force when viewed from the co-rotating reference frame. Comparison of the expressions for the movement of a body on the rotating Earth in the inert versus rotating coordinate systems, shows that the rotating reference frame requires additional terms to correctly describe the motion. One of these terms, introduced to convert the equations of motion between the inert and rotating frames, is the so-called Coriolis term (Coriolis, 1835).

Ever since its first mathematical description in 1835 (Coriolis, 1835) this concept is most often taught as a matter of coordinate transformation, rather than focusing on its physical relevance (Persson, 1998). Students are furthermore taught that the Coriolis force is a “fictitious” force, resulting from the rotation of a system and that its influence is not visible when observed from outside the rotating frame of reference. It is therefore often perceived as “a ‘mysterious’ force resulting from a series of ‘formal manipulations’” (Persson, 2010).

In many oceanography programs, the difficult task of helping students gain a deeper understanding of these systems is approached by presenting demonstrations, either in the form of videos or simulations (e.g. a ball being thrown on a merry-go-round, showing the movement both from a rotating and a non-rotating frame, Urbano & Houghton (2006)), or in the lab as demonstration, or as a hands-on experiment. While helpful in visualizing an otherwise abstract phenomenon, using a common rotating table introduces difficulties when comparing the observed motion to the motion on Earth. This is, among other factors, due to the table’s flat surface (Durran and Domonkos, 1996), the alignment of the (also fictitious) centrifugal force with the direction of movement of the ball (Persson, 2010), and the fact that a component of axial rotation is introduced to the moving object when launched. Hence, the Coriolis force is not isolated. Regardless of the drawbacks associated with the use of a (flat) rotating table to illustrate the Coriolis effect, we see value in using it to make the concept of fictitious forces more intuitive, and it is widely used to this effect.

During conventional instruction, students are exposed to simulations and after instruction, students are able to calculate the influence of the Coriolis term. Nevertheless, they have difficulty in anticipating the movement of an object on a rotating body when confronted with a real-life situation where they themselves are not part of the rotating system. When asked, students report that they are anticipating a deflection depending on the rotation direction and rate. Contextually triggered, these knowledge elements are invalidly applied to seemingly similar circumstances and lead to incorrect conclusions. Similar problems have been described for example in engineering education (Newcomer, 2010).

 

The Coriolis demonstration

A demonstration observing a body on a rotating table from within and from outside the rotating system was run as part of the practical experimentation component of the “Introduction to Oceanography” semester course. Students were in the second year of their Bachelors in meteorology and oceanography at the Geophysical Institute of the University of Bergen, Norway. Similar experiments are run at many universities as part of their oceanography or geophysical fluid dynamics instruction.

 

Materials:

  • Rotating table with a co-rotating video camera (See Figure 1. For simpler and less expensive setups, please refer to “Possible modifications of the activity”)
  • Screen where images from the camera can be displayed
  • Solid metal spheres
  • Ramp to launch the spheres from
  • Tape to mark positions on the floor

folie1

Figure 1A: View of the rotating table. Note the video camera on the scaffolding above the table and the red x (marking the catcher’s position) on the floor in front of the table, diametrically across from where, that very instant, the ball is launched on a ramp. B: Sketch of the rotating table, the mounted (co-rotating) camera, the ramp and the ball on the table. C: Student tracing the curved trajectory of the metal ball on a transparency. On the screen, the experiment is shown as filmed by the co-rotating camera, hence in the rotating frame of reference.

 

 

Time needed:

About 45 minutes to one hour per student group. The groups should be sufficiently small so as to ensure active participation of every student. In our small lab space, five has proven to be the upper limit on the number of students per group.

 

Student task:

In the demonstration, a metal ball is launched from a ramp on a rotating table (Figure 1A,B). Students simultaneously observe the motion from two vantage points: where they are standing in the room, i.e. outside of the rotating system of the table; and, on a screen that displays the table, as captured by a co-rotating camera mounted above it. They are subsequently asked to:

  • trace the trajectory seen on the screen on a transparency (Figure 1C),
  • measure the radius of this drawn trajectory; and
  • compare the trajectory’s radius to the theorized value.

The latter is calculated from the measured rotation rate of the table and the linear velocity of the ball, determined by launching the ball along a straight line on the floor.

 

Instructional approach

In years prior to 2012, the course had been run along the conventional lines of instruction in an undergraduate physics lab: the students read the instructions, conduct the experiment and write a report.

In 2012, we decided to include an elicit-confront-resolve approach to help students realize and understand the seemingly conflicting observations made from inside versus outside of the rotating system (Figure 2). The three steps we employed are described in detail below.

folie2

Figure 2: Positions of the ramp and the ball as observed from above in the non-rotating (top) and rotating (bottom) case. Time progresses from left to right. In the top plots, the position in inert space is shown. From left to right, the current position of the ramp and ball are added with gradually darkening colors. In the bottom plots, the ramp stays in the same position, but the ball moves and the current position is always displayed with the darkest color.

  1. Elicit the lingering misconception

1.a The general function of the “elicit” step

The goal of this first step is to make students aware of their beliefs of what will happen in a given situation, no matter what those beliefs might be. By discussing what students anticipate to observe under different physical conditions before the actual experiment is conducted, the students’ insights are put to the test. Sketching different scenarios (Fan (2015), Ainsworth et al. (2011)) and trying to answer questions before observing experiments are important steps in the learning process since students are usually unaware of their premises and assumptions. These need to be explicated and verbalized before they can be tested, and either be built on, or, if necessary, overcome.

 

1.b What the “elicit” step means in the context of our experiment

Students have been taught in introductory lectures that in a counter-clockwise rotating system (i.e. in the Northern Hemisphere) a moving object will be deflected to the right. They are also aware that the extent to which the object is deflected depends on its velocity and the rotational speed of the reference frame.

A typical laboratory session would progress as follows: students are asked to observe the path of a ball being launched from the perimeter of the circular, not-yet rotating table by a student standing at a marked position next to the table, the “launch position”. The ball is observed to be rolling radially towards and over the center point of the table, dropping off the table diametrically opposite from the position from which it was launched. So far nothing surprising. A second student – the catcher – is asked to stand at the position where the ball dropped off the table’s edge so as to catch the ball in the non-rotating case. The position is also marked on the floor with insulation tape.

The students are now asked to predict the behavior of the ball once the table is put into slow rotation. At this point, students typically enquire about the direction of rotation and, when assured that “Northern Hemisphere” counter-clockwise rotation is being applied, their default prediction is that the ball will be deflected to the right. When asked whether the catcher should alter their position, the students commonly answer that the catcher should move some arbitrary angle, but typically less than 90 degrees, clockwise around the table. The question of the influence of an increase in the rotational rate of the table on the catcher’s placement is now posed. “Still further clockwise”, is the usual answer. This then leads to the instructor’s asking whether a rotational speed exists at which the student launching the ball, will also be able to catch it him/herself. Ordinarily the students confirm that such a situation is indeed possible.

 

  1. Confronting the misconception

2.a The general function of the “confront” step

For those cases in which the “elicit” step brought to light assumptions or beliefs that are different from the instructor’s, the “confront” step serves to show the students the discrepancy between what they stated to be true, and what they observe to be true.

 

2.b What the “confront” step means in the context of our experiment

The students’ predictions are subsequently put to the test by starting with the simple, non-rotating case: the ball is launched and the nominated catcher, positioned diametrically across from the launch position, seizes the ball as it falls off the table’s surface right in front of them. As in the discussion beforehand, the table is then put into rotation at incrementally increasing rates, with the ball being launched from the same position for each of the different rotational speeds. It becomes clear that the catcher need not adjust their position, but can remain standing diametrically opposite to the student launching the ball – the point where the ball drops to the floor. Hence students realize that the movement of the ball relative to the non-rotating laboratory is unaffected by the table’s rotation rate.

This observation appears counterintuitive, since the camera, rotating with the system, shows the curved trajectories the students had expected; circles with radii decreasing as the rotation rate is increased. Furthermore, to add to their confusion, when observed from their positions around the rotating table, the path of the ball on the rotating table appears to show a deflection, too. This is due to the observer’s eye being fooled by focusing on features of the table, e.g. cross hairs drawn on the table’s surface or the bars of the camera scaffold, relative to which the ball does, indeed, follow a curved trajectory. To overcome this latter trickery of the mind, the instructor may ask the students to crouch, diametrically across from the launcher, so that their line of sight is aligned with the table’s surface, i.e. at a zero zenith angle of observation. From this vantage point the ball is observed to indeed be moving in a straight line towards the observer, irrespective of the rate of rotation of the table.

To further cement the concept, the table may again be set into rotation. The launcher and the catcher are now asked to pass the ball to one another by throwing it across the table without it physically making contact with the table’s surface. As expected, the ball moves in a straight line between the launcher and the catcher, who are both observing from an inert frame of reference. However, when viewing the playback of the co-rotating camera, which represents the view from the rotating frame of reference, the trajectory is observed as curved.

 

  1. Resolving the misconception

3.a The general function of the “resolve” step

Misconceptions that were brought to light during the “elicit” step, and whose discrepancy with observations was made clear during the “confront” step, are finally corrected in the “resolve” step. While this sounds very easy, in practice it is anything but. The final step of the elicit-confront-resolve instructional approach thus presents the opportunity for the instructor to aid students in reflecting upon and reassessing previous knowledge, and for learning to take place.

 

3.b What the “resolve” step means in the context of our experiment

The instructor should by now be able to point out and dispel any remaining implicit assumptions, making it clear that the discrepant trajectories are undoubtedly the product of viewing the motion from different frames of reference. Despite the students’ observations and their participation in the experiment this is not a given, nor does it happen instantaneously. Oftentimes further, detailed discussion is required. Frequently students have to re-run the experiment themselves in different roles (i.e. as launcher as well as catcher) and explicitly state what they are noticing before they trust their observations.

 

Possible modifications of the activity:

We used the described activity to introduce the laboratory activity, after which the students had to carry out the exercise and write a report about it. Follow-up experiments that are often conducted usually include rotating water tanks to visualize the effect of the Coriolis force on the large-scale circulation of the ocean or atmosphere, for example on vortices, fronts, ocean gyres, Ekman layers, Rossby waves, the General circulation and many other phenomena (see for example Marshall and Plumb (2007)).

Despite their popularity in geophysical fluid dynamics instruction at the authors’ current and previous institutions, rotating tables might not be readily available everywhere. Good instructions for building a rotating table can, for example, be found on the “weather in a tank” website, where there is also the contact information to a supplier given: http://paoc.mit.edu/labguide/apparatus.html. A less expensive setup can be created from old disk players or even Lazy Susans. In many cases, setting the exact rotation rate is not as important as having a qualitative difference between “fast” and “slow” rotation, which is very easy to realize. In cases where a co-rotating camera is not available, by dipping the ball in either dye or chalk dust (or by simply running a pen in a straight line across the rotating surface), the trajectory in the rotating system can be visualized. The method described in this manuscript is easily adapted to such a setup.

Lastly we suggest using an elicit-confront-resolve approach even when the demonstration is not run on an actual rotating table. Even if the demonstration is only virtually conducted, for example using Urbano & Houghton (2006)’s Coriolis force simulation, the approach is beneficial to increasing conceptual understanding.

Discussion

The authors noticed in 2011 that most students participating in that year’s lab course, despite having participated in performing the experiment, still harbored misconceptions. Despite having taken part in performing the demonstration, misunderstanding remained as to what forces were acting on the ball and what the movement of the ball looked like in the different frames of reference. This led to the authors adopting the elicit-confront-resolve approach for instruction, as described above, in 2012.

We initially considered starting the lab session on the Coriolis force by throwing the ball diametrically across the rotating table. Students would then see on-screen the curved trajectory of a ball, which had never made physical contact with the table rotating beneath it. It was thought that initially considering the motion from the co-rotating camera’s view, and seeing it displayed as a curved trajectory when direct observation had shown it to be linear, might hasten the realization that it is the frame of reference that is to blame for the ball’s curved trajectory. However the speed of the ball makes it very difficult to observe its curved path on the screen in real time. Replaying the footage in slow motion helps in this regard. Yet, removing direct observation through recording and playback seemingly hampers acceptance of the occurrence as “real”. It was therefore decided that this method only be used to further illustrate the concept once students were familiar with the general (or standard) experimental setup.

In 2012, 7 groups of 5 students each conducted this experiment under the guidance of both authors together. The authors gained the impression that the new strategy of instruction enhanced the students’ understanding. In order to test this impression and the learning gain resulting from the experiment with the new methodology, in 2013 identical work sheets were administered before and after the experiment. These work sheets were developed by the authors as instructional materials to make sure that every student individually went through the elicit-confront-resolve process even when, with future cohorts, this experiment might be run by other instructors (who might not be as familiar with the elicit-confront-resolve method) and with larger student groups (where individual conversations with every student might be less feasible for the instructor). However, it turned out to be useful for quantifying what we had previously only qualitatively noticed: That a large part of the student population did indeed expect to see a deflection despite observing from an inert frame of reference.

In total, 8 students took the course in 2013, and all agreed to let us talk about their learning process in the context of this article. One of those students did not check the before/after box on the work sheet. We therefore cannot distinguish the work done before and after the experiment, and will disregard this student’s responses in the following discussion. This student however answered correctly on one of the tests and incorrectly on the other.

In the first question, students were instructed to consider both a stationary table and a table rotating at two different rates. They were then asked to, for each of the scenarios, mark with an X the location where they thought the ball would contact the floor after dropping off the table’s surface. In the work sheet done before instruction, all 7 students predicted that the ball would hit the floor in different spots – diametrically across from the launch point for no rotation, and at increasing distances from that first point with increasing rotation rates of the table (Figure 3). This is the same misconception we noticed in earlier years and which we aimed to elicit with this question: students were applying correct knowledge (“In the Northern Hemisphere a moving body will be deflected to the right”) to situations where this knowledge was not applicable (when observing the rotating body and the moving particle upon it from an inert frame of reference).

folie3

Figure 3A: Depiction of the typical wrong answer to the question where a ball would land on a floor after rolling across a table rotating at different rotation rates. B: Correct answer to question in (A). C: Correct trajectories of balls rolling across a rotating table.

In a second question, students were asked to imagine the ball leaving a dye mark on the table as it rolls across it, and to draw these traces left on the table. In this second question students were thus required to infer that this would be analogous to regarding the motion of the ball as observed from the co-rotating frame of reference. Five students drew them correctly and consistently with the direction of rotation they assumed in the first questions, while the remaining two did not attempt to answer this question.

After the experiment had been run repeatedly and discussed until the students signaled no further need for re-runs or discussion, the students were asked to redo the work sheet. This resulted in 6 students answering both questions correctly. The remaining student answered the second question correctly, but repeated the same incorrect answer to the first question that they gave in their earlier worksheet.

Seeing as the students had extensively discussed and participated in the experiment immediately prior to doing the work sheet for the second time, it is maybe not surprising that the majority answered the questions correctly during the second iteration. In this regard it is important to note that our teaching approach was not planned as a scientific study, but rather developed naturally over the course of instruction. Had we set out to determine the longer-term impact of its efficacy, or its success in abetting conceptual understanding, we should ideally have tested the concept in a new context. As a teaching practice this is advisable.

However, the students’ laboratory reports supply additional support of the claimed usefulness of our new approach. These reports had to be submitted within seven days of originally doing the experiment and accompanying work sheets. One of the questions in their laboratory manual explicitly addresses observing the motion from an inert frame of reference as well as the influence of the table’s rotational period on such motion. This question was answered correctly by all 8 students. This is remarkable for two reasons: firstly, because in the previous year without the elicit-confront-resolve instruction, this question was answered incorrectly by the vast majority of students; and secondly, because for this specific cohort, it is one of the few questions that all students answered correctly in their laboratory reports.

Seven students most certainly make for an insufficient sample size to claim these results have any statistical significance, and this discussion only scratches the surface of what and how students understand frames of reference. However, there is preliminary indication that a) students do indeed harbor the misconception we suspected, and b) that an elicit-confront-resolve approach helped resolve the misunderstanding.

Conclusions

In the suggested instructional strategy, students are required to explicitly state their expectations about what the outcome of an experiment will be, even though their presuppositions are likely to be wrong. The verbalizing of their assumptions aids in making them aware of what they implicitly hold to be true. This is a prerequisite for further discussion and enables confrontation and resolution of potential misconceptions.

This elicit-confront-resolve approach has implications beyond instruction on the Coriolis force or frames of reference. Being able to correctly calculate solutions to textbook problems does not necessarily imply a correct understanding of a concept. Generally speaking, when investigating the roots of student misconceptions, the problem is often located elsewhere than initially suspected. The instructor’s awareness hereof goes a long way towards better understanding and better supporting students’ learning.

We would also like to point out that gaining (the required) insight from a seemingly simple experiment, such as the one discussed in this paper, might not be nearly as straightforward or obvious for the students as anticipated by the instructor. Again, probing for conceptual understanding rather than the ability to calculate a correct answer proved critical in understanding where the difficulties stemmed from, and only a detailed discussion with several students could reveal the scope of difficulties. We would encourage every instructor not to take at face value the level of difficulty your predecessors claim an experiment to have!

Acknowledgements

The authors are grateful for the students’ consent to present their worksheet responses in this article.

Supplementary materials

Movies of the experiment can be seen here:

Rotating case: https://vimeo.com/59891323

Non-rotating case: https://vimeo.com/59891020

References

Ainsworth, S., Prain, V., & Tytler, R. (2011). Drawing to Learn in Science Science, 333 (6046), 1096-1097 DOI: 10.1126/science.1204153

 

Baillie, C., MacNish, C., Tavner, A., Trevelyan, J., Royle, G., Hesterman, D., Leggoe, J., Guzzomi, A., Oldham, C., Hardin, M., Henry, J., Scott, N., and Doherty, J. 2012. Engineering Thresholds: an approach to curriculum renewal. Integrated Engineering Foundation Threshold Concept Inventory 2012. The University of Western Australia, < http://www.ecm.uwa.edu.au/__data/assets/pdf_file/0018/2161107/Foundation-Engineering-Threshold-Concept-Inventory-120807.pdf>

 

Coriolis, G. G. 1835. Sur les équations du mouvement relatif des systèmes de corps. J. de l’Ecole royale polytechnique 15: 144–154.

 

Cushman-Roisin, B. 1994. Introduction to Geophysical Fluid DynamicsPrentice-Hall. Englewood Cliffs, NJ, 7632.

 

Durran, D. R. and Domonkos, S. K. 1996. An apparatus for demonstrating the inertial oscillation, BAMS, Vol 77, No 3

 

Fan, J. (2015). Drawing to learn: How producing graphical representations enhances scientific thinking. Translational Issues in Psychological Science, 1 (2), 170-181 DOI: 10.1037/tps0000037

 

Gill, A. E. 1982. Atmosphere-ocean dynamics (Vol. 30). Academic Pr.

 

Kornell, N., Jensen Hays, M., and Bjork, R.A. (2009), Unsuccessful Retrieval Attempts Enhance Subsequent Learning, Journal of Experimental Psychology: Learning, Memory, and Cognition 2009, Vol. 35, No. 4, 989–998

 

Hart, C., Mulhall, P., Berry, A., Loughran, J., and Gunstone, R. 2000. What is the purpose of this experiment? Or can students learn something from doing experiments?, Journal of Research in Science Teaching, 37 (7), p 655–675

 

Mackin, K.J., Cook-Smith, N., Illari, L., Marshall, J., and Sadler, P. 2012. The Effectiveness of Rotating Tank Experiments in Teaching Undergraduate Courses in Atmospheres, Oceans, and Climate Sciences, Journal of Geoscience Education, 67–82

 

Marshall, J. and Plumb, R.A. 2007. Atmosphere, Ocean and Climate Dynamics, 1st Edition, Academic Press

 

McDermott, L. C. 1991. Millikan Lecture 1990: What we teach and what is learned – closing the gap, Am. J. Phys. 59 (4)

 

Milner-Bolotin, M., Kotlicki A., Rieger G. 2007. Can students learn from lecture demonstrations? The role and place of Interactive Lecture Experiments in large introductory science courses. The Journal of College Science Teaching, Jan-Feb, p.45-49.

 

Muller, D.A., Bewes, J., Sharma, M.D. and Reimann P. 2007. Saying the wrong thing: improving learning with multimedia by including misconceptions, Journal of Computer Assisted Learning (2008), 24, 144–155

 

Newcomer, J.L. 2010. Inconsistencies in Students’ Approaches to Solving Problems in Engineering Statics, 40th ASEE/IEEE Frontiers in Education Conference, October 27-30, 2010, Washington, DC

 

Persson, A. 1998. How do we understand the Coriolis force?, BAMS, Vol 79, No 7

 

Persson, A. 2010. Mathematics versus common sense: the problem of how to communicate dynamic meteorology, Meteorol. Appl. 17: 236–242

 

Pinet, P. R. 2009. Invitation to oceanography. Jones & Bartlett Learning.

 

Posner, G.J., Strike, K.A., Hewson, P.W. and Gertzog, W.A. 1982. Accommodation of a Scientific Conception: Toward a Theory of Conceptual Change. Science Education 66(2); 211-227

 

Pond, S. and G. L. Pickard 1983. Introductory dynamical oceanography. Gulf Professional Publishing.

 

Roth, W.-M., McRobbie, C.J., Lucas, K.B., and Boutonné, S. 1997. Why May Students Fail to Learn from Demonstrations? A Social Practice Perspective on Learning in Physics. Journal of Research in Science Teaching, 34(5), page 509–533

 

Talley, L. D., G. L. Pickard, W. J. Emery and J. H. Swift 2011. Descriptive physical oceanography: An introduction. Academic Press.

 

Tomczak, M., and Godfrey, J. S. 2003. Regional oceanography: an introduction. Daya Books.

 

Trujillo, A. P., and Thurman, H. V. 2013. Essentials of Oceanography, Prentice Hall; 11 edition (January 14, 2013)

 

Urbano, L.D., Houghton J.L., 2006. An interactive computer model for Coriolis demonstrations. Journal of Geoscience Education 54(1): 54-60

 

P.S.: This text originally appeared on my website as a page. Due to upcoming restructuring of this website, I am reposting it as a blog post. This is the original version last modified on January 24th, 2017.

I might write things differently if I was writing them now, but I still like to keep my blog as archive of my thoughts.

A tool for planning online teaching units

Nicole Podleschny & Mirjam Glessmer, 2015

In our recent workshop on “supporting self-organized learning with online media”, Nicole Podleschny and I came up with a morphological box to help plan online teaching units. The morphological box is basically a list of criteria that we thought might be relevant, and then we suggest different values for each of the criteria and leave plenty of space for participants’ own ideas. By providing a very broad overview over the many parameters and possibilities, we hoped to get participants away from the prevailing understanding that “online learning” is necessarily the same as multiple-choice e-assessment, and to get them think more broadly about what options might be most appropriate for whatever their goals might be.

The very important first step in planning of any kind of teaching unit has to be — as always! — to think about what learning outcomes the instructor wants to achieve. Only when this is really clear, appropriate methods and tools can be chosen!

Then we can have a look at the morphological box:

morphological_box

Morphological box for planning of online learning units (Podleschny & Glessmer, 2015)

Now we can go through the different criteria and have a look at what value seems to make sense. Of course, there are many more options possible than those we suggest here – please feel free to fill in whatever suits your needs best!

Sometimes it is really helpful to just be aware of different options. Even though you might not want to pick any of the options given in the morphological box, maybe just reading them and deciding against them will spark an idea of what actually works best for your case.

The morphological box can also be used to design different scenarios and discuss them against each other in order to figure out which criteria are more relevant to you than others.

If you would like to give it a try, you can download our morphological box below.

Morphological box [pdf English | pdf German]

P.S.: This text originally appeared on my website as a page. Due to upcoming restructuring of this website, I am reposting it as a blog post. This is the original version last modified on December 26th, 2015.

I might write things differently if I was writing them now, but I still like to keep my blog as archive of my thoughts.