Super excited to share a guest post today: Felipe is writing about his recent #WaveWatching article on “Evaluating shallow water waves by observing Mach cones on the beach”. I came across this article and was going to write a summary, but how much cooler is it to hear from Felipe himself? Thank you for being here! :)
My name is Dr Felipe Veloso1 and I tremendously appreciate Dr Mirjam Glessmer invitation to write this post and letting me contribute to the terrific #WaveWatching collection!!
One of the spectacular things of #WaveWatching is that the observations are ubiquitous. It doesn’t matter if you live in Germany, USA, Japan or Chile. Oscillations and waves are there, whether you observe swimming pools, lakes, sea, or even a relaxing bathtub ready for you. In all cases, the water is always naturally oscillating in a comfortable dance combining up-and-down and back-and-forth movements. If you enjoy these natural phenomena like I do, invest some of your time and take a look to the wonderful #WaveWatchingWednesday and #KitchenOceanography collections that Mirjam has gathered for us. But there are some occasions that these wave phenomena are obscured to our naked-eye observations and a more careful revision is needed to figure out where these oscillations are hidden. A turbulent river coming down of a hill, or the simple passing of fast water flow in front of our eyes are some examples of “waves hidden at first sight”. Such situation occurred to me in the latest family vacations we had as a break from the lockdowns imposed by the pandemia. In particular, this situation became the reason of an article in Physics Education, and also the reason of why I am writing these lines.
In an attempt to run away from the contaminated air of Santiago (the Chilean capital city, surrounded by mountains), we drove ~90 minutes to Viña del Mar city, to enjoy one week in the beach side. In this place, with the appropriate weather and personal calmness, families can enjoy the waves crushing the beach, the rising of children as “sand engineers”, and the “continuous fight” between these children and the ocean waves to avoid the destruction of the sand fortresses by the water. It is in this relaxing and family-friendly environment where my story begins.
My kids are playing in the sand and my feet are partially covered by water. After long time, we are able to come out from our houses after several months of mandatory quarantines, pandemic stress, and online teaching activities. In this particular moment, watching waves looks like a perfect panorama for me. Suddenly, the voice of my daughter Pilar wakes me up and asked me two questions: “Dad, what are you looking in the water?… and dad, why does the water creates those conical shapes at the end of the undertow current?” The first answer was easy. I was #WaveWatching. But the second answer was not so simple. What about those conical shapes?
Before her question, I haven’t thought on that. Rapidly, I realized I was observing a wave phenomena in a different and non-standard way. We were observing shock waves in the shape of Mach cones!! These cones appear when an object moves inside of a fluid with a relative velocity larger than the natural oscillation velocity of the fluid. In these situations, there is a shock occurring in the fluid itself. The tip of the cone (or V-) shape arises from the relative movement of the object, whereas the radial expansion of the wave creates the sides of the cone. This explains the formation of V-shapes in the water when a ship travels in a river, or when ducks swim in the lake. In the case of beach observations, the cones were originated by stationary small seashells or larger grains buried in the sand when the undertow water current returned back to the sea with depth not sufficient to immerse my toes.
Now, I am not really sure if my 8 years-old daughter or my 11 years-old son understood completely my explanations of waves and Mach cones. But, I am sure they understood that observing nature can be a fun and relaxing activity to enjoy in family vacations. As an exercise, I taught them how to compute the wave velocity by measuring these Mach cones. I also show them that we did not need any fancy or expensive equipment to accurately evaluate it. We only require interest and fascination on looking for an explanation of a natural phenomena… a phenomena that they could observe while enjoying the beach, the sand and the family time.
Further details can be found in the paper: Felipe Veloso (2021) “Evaluating shallow water waves by observing Mach cones on the beach” Phys Education 56, 054001.
I’ve been fascinated by gooselings recently, mainly because they are super cute. But I can tell you about what makes wave watching special when the waves are made by geese — it is an extra challenging type of wave watching! (Check out this post for a more general — and likely much more useful — guide to wave watching)
I dug through my phone (all these pictures are from this year, but they aren’t posted chronologically as you’ll see from the size of the gooselings) and found quite a collection. This is for you, Yasmin and Maike!
Let’s start out with a couple of pics that work well for wave watching purposes, but that already show hints of the challenges discussed below.
So why is it so difficult to get good pictures of geese-made waves? Continue reading
I was reading an article on “active learning” by Lombardi et al. (2021), when the sentence “In undergraduate geoscience, Pugh et al. (2019) found that students who made observations of the world and recognized how they might be explained by concepts from their classes were more likely to stay in their major than those who do not report this experience” jumped at me. Something about observing the world and connecting it to ideas from class was so intriguing, that I had to go down that rabbit hole and see where this statement was coming from, and if it might help me as a theoretical framework for thinking about #WaveWatching (which I’ve been thinking about a lot since the recent teaching conversation).
Going into that Pugh et al. (2019) article, I learned about a concept called “transformative experience”, which I followed back to Pugh (2011): A transformative experience happens when students see the world with new eyes, because they start connecting concepts from class with their real everyday lives. There is quote at the beginning of that article which reminds me very much of what people say about wave watching (except that in the quote the person talks about clouds): that once they’ve started seeing pattern because they understood that what they look at isn’t chaotic but can be explained, they cannot go back to just looking at the beauty of it without questioning why it came to be that way. They now feel the urge to make sense of the pattern they see, everytime they come across anything related to the topic.
This is described as the three characteristics of transformative experiences:
- they are done voluntarily out of intrinsic motivation (meaning that the application of class concepts is not required by the teacher or some other authority),
- they expand peception (when the world is now seen through the subject’s lens and looks different than before), and
- they have experiential value (meaning the person experiencing them perceives them as adding value to their lives).
And it turns out that facilitating such transformative experiences might well be what distinguishes schools with higher student retention from those with lower student retention in Pugh et al.’s 2019 study!
But how can we, as teachers, facilitate transformative experiences? Going another article further down the rabbit hole to Pugh et al. (2010), this is how!
The “Teaching for Transformative Experiences” model consists of three methods acting together:
- framing content in a way that the “experiential value” becomes clear, meaning making an effort to explain the value that perceiving the world in such a way adds to our lives. This can be done by expressing the feelings it evokes or usefulness that it adds. For #WaveWatching, I talk about how much I enjoy the process, but also how making sense of an aspect of the world that first seemed chaotic is both satisfying and calming to me. But framing in terms of the value of the experience can also be done by metaphors, for example about the tales that rocks, trees, or coastlines could tell. Similarly, when I speak about “kitchen oceanography”, I hope that it raises curiosity about how we can learn about the ocean in a kitchen.
- scaffolding how students look at the world by helping them change lenses step by step, i.e. “re-seeing”, for example by pointing out specific features, observing them together, talking through observations or providing opportunities to share and discuss observations (so pretty much my #WaveWatching process!).
- modeling transformative experiences, i.e. sharing what and how we perceive our own transformative experiences, in order to show students that it’s both acceptable and desirable to see the world in a certain way, and communicate about it. I do this both in person as well as whenever I post about #WaveWatching online.
So it seems that I have been creating transformative experiences with #WaveWatching all this time without knowing it! Or at least that this framework works really well to describe the main features of #WaveWatching.
Obviously I have only just scratched the literature on transforming experiences, but I have a whole bunch of articles open on my desktop already, about case studies of facilitating transformative experiences in teaching. And I cannot wait to dig in and find out what I can learn from that research and apply it to improve #WaveWatching! :)
Lombardi, D., Shipley, T. F., & Astronomy Team, Biology Team, Chemistry Team, Engineering Team, Geography Team, Geoscience Team, and Physics Team. (2021). The curious construct of active learning. Psychological Science in the Public Interest, 22(1), 8-43.
Pugh, K. J., Phillips, M. M., Sexton, J. M., Bergstrom, C. M., & Riggs, E. M. (2019). A quantitative investigation of geoscience departmental factors associated with the recruitment and retention of female students. Journal of Geoscience Education, 67(3), 266-284.
Pugh, K. J. (2011). Transformative experience: An integrative construct in the spirit of Deweyan pragmatism. Educational Psychologist, 46(2), 107-121.
Pugh, K. J., Linnenbrink-Garcia, L., Koskey, K. L., Stewart, V. C., & Manzey, C. (2010). Teaching for transformative experiences and conceptual change: A case study and evaluation of a high school biology teacher’s experience. Cognition and Instruction, 28(3), 273-316.
iEarth is currently establishing the new-to-me format of “teaching conversations”, where two or more people meet to discuss specific aspects of one person’s teaching in a “critical friend” setting. Obviously I volunteered to be grilled, and despite me trying to suggest other topics, too (like the active lunch break and the “nerd topic” intro in a workshop), we ended up talking about … #WaveWatching. Not that I’m complaining ;-)
After the conversation, I wrote up the main points as a one-pager, which I am sharing below. Thank you, Kjersti and Torgny, for an inspiring conversation!
I use #WaveWatching in introductory courses in oceanography and in science outreach both on social media and in in-person guided tours. #WaveWatching is the practice of looking at water and trying to make sense of why its surface came to look the way it does: What caused the waves (e.g. wind, ships, animals)? How did the coastline influence the waves (e.g. shelter it from wind in some places, or block entrance into a basin from certain directions, or cause reflection)? What processes must be involved that we cannot directly observe (e.g. interactions with a very shallow area or a current)? Kjersti Daae (pers. comm.) suggests an analogy to explain #WaveWatching: Many people enjoy a stir-fry for its taste, like we enjoy looking at water, glittering in the sun, without questioning what makes it special. But once we start focusing on noticing different ingredients and the ways they are prepared, it is a small change in perspective that changes our perception substantially, and leads to a new appreciation and deeper understanding of all future stir-fries (and possibly other dishes) we will encounter.
I teach #WaveWatching using a cognitive apprenticeship leaning (Collins et al., 1988) approach*: By drawing on photos of selected wave fields (in the field using a drawing app on a tablet), I model my own sensemaking (Odden & Russ, 2019). I coach students to engage in the process, and slowly fade myself out. Students then engage in #WaveWatching practice anywhere they find water – in the sink, a puddle in the street, a lake, the ocean. Since waves are universally accessible, this works perfectly as hyper-local “excursions” in virtual teaching: Students work “in the field” right outside their homes.
Waves are not an integral part of the general curriculum in physical oceanography. While some wave processes are relevant for specific research questions, for typical large-scale oceanography they are not. And the concepts used in #WaveWatching are not even new to students, they are just an application of high-school optics to a new context.
Nevertheless, #WaveWatching helps work towards several goals that are important to me:
- Using “authentic data” acts as motivation to engage with theory because the connection with the real world makes it feel more interesting and engaging (Kjelvik & Schultheis, 2019).
- Engaging in sensemaking and gaining experience on what can (and cannot!) be concluded from an observation are highly relevant skills and this is an opportunity for practice.
- Building an identity as oceanographer – seeing the world through a new lens, joining a community of practice (Wenger, 2011), but also being able to demonstrate newfound expertise and identity to friends and family outside of that new community by talking about this new lens – are otherwise rare in socially distant times.
After being exposed to #WaveWatching, people tell me that they can’t look at water in the same way they did before. They are now seeing pattern they never noticed, and they try to explain them or ask themselves what I would see. They often send me photos of their observation years after our last interaction, and ask if I agree with their interpretations. #WaveWatching might thus be a threshold concept, “a portal, opening up a new and previously inaccessible way of thinking about something” and where “the change of perspective […] is unlikely to be forgotten” (Meyer & Land, 2003).
- Collins, A., Brown, J. S., & Newman, S. E. (1988). Cognitive apprenticeship: Teaching the craft of reading, writing and mathematics. Thinking: The Journal of Philosophy for Children, 8(1), 2-10.
- Kjelvik, M. K., & Schultheis, E. H. (2019). Getting messy with authentic data: Exploring the potential of using data from scientific research to support student data literacy. CBE—Life Sciences Education, 18(2), es2.
- Meyer, J. H. F., and Land, R. (2003) “Threshold Concepts and Troublesome Knowledge: Linkages to Ways of Thinking and Practising” in Improving Student Learning: Ten Years On. C. Rust (Ed), OCSLD, Oxford.
- Odden, T. O. B., & Russ, R. S. (2019). Defining sensemaking: Bringing clarity to a fragmented theoretical construct. Science Education, 103(1), 187-205.
- Wenger, E. (2011). Communities of practice: A brief introduction.
*more on that in this post (that comes online on 21.5.2021).
You might remember this edge here and the reflection situation.
More details in this recent post, but in a nutshell: The wave crests marked in red are approaching the beach and wooden edge, and where they hit the wooden edge, they get reflected and converted into the green wave crests which propagate away from the edge again.
And this is what the other side of the edge looks like: The reflections end where the edge stops!
Again, the red wave crests are the incoming waves, and the green the reflections. Waves always travel perpendicularly to their crests, so you see how they propagate away from the boundary and appear to be cut on the right side where the boundary suddenly stopped and no reflection could happen any more.
When I look at the picture above, I see basically three different zones on the surface of the lake.
The yellow zone, which is under the direct influence of the wind, where the water is full of small waves, and then two other zones.
In the red zone, the water isn’t under direct influence of the wind any more, we see clear, parallel wave crests propagating towards the shore. I’ve marked some of them below.
While they are still to the left of the wooden edge, not much happens. But once they hit the edge, we enter the “green zone”: The incoming wave crests get reflected at the wooden edge. They start propagating out onto the lake, getting longe and longer over time, while the red wave crests continue running further and further into the green zone, so we get interference between the incoming and reflected wave crests. Pretty cool! :)
How about a little wave watching game to celebrate #WaveWatchingWednesday?
The minute I saw Andrea Lopez Lang’s tweet, where she made a “fortune teller” (no idea that’s what they were called) as going-away and please-remember-what-you-learned gift for her class, I HAD to make something like that!
Unfortunately I’m not teaching a class right now where I could easily see how this could be done, but luckily there is always wave watching!
And Kjersti had a great idea for how this could be used right away: To send students out with these toys and ask them to discover one example for each of the waves shown on the toy. Plus then of course document it, and share on social media… ;-)
Waves are traditionally taught in a theoretical and very dry manner, and the transfer to the real world is hardly happening at all (especially since the large tank in the basement at GFI has been demolished, which still breaks my heart), so this is a fun way to get students outside and try & find contents from their lecture in real life.
P.S.: It’s not as difficult as it might seem at first once you start observing and get a little creative. Nobody said that the rock that makes the ring waves had to have been there when you got there, and wakes can be created by ships or bird or even if you pull a stick through the water…
Even though I haven’t done a #WaveWatchingWednesday in a looong time, there has of course been a lot of wave watching going on. But the longer I wait with copying all the Instagram posts into a blog post, the more work it gets, the longer I put it off. Vicious circle! But here we go today. Plenty of interesting and plenty of beautiful pics! Enjoy!
It doesn’t feel like it, but today marks the 7-year-anniversary of my first blog post on my “Adventures in Oceanography and Teaching”! To celebrate, I sent out this call to action (and please feel free to respond, no matter when you are reading this):
Below, I am sharing the pictures that people sent me plus my thoughts on them, newest on top. Pictures that reached me after August 28th 2020 will be posted in follow-up posts! (Keep them coming, I love it!)
23:58 — Kristina
21:55 — Phil (San Francisco)
21:06 — Clark (Bay of Fundy)
Clark wrote an entire thread explaining this awesome observation in the Bay of Fundy. You should totally check out the whole thread & explanations on Twitter, but I had to share this video so you can see what an exciting situation it is!
20:51 — Elin (Bergen)
18:14 — Simone (Hamburg)
15:43 — Dong
15:18 — Nena (Bodensee)
15:13 — Jeffrey (Boulder)
Wow, this video is super tricky! Please check it out — volume up!
At first, I thought that the periodicity was set by eddies shedding periodically after water had washed over the obstacle. But after about the 50th time I looked at the video, the obstacle (is it driftwood?) seemed to start moving. If it is actually moving, the periodicity makes sense: The wood is trapped in place (you see that on the far side of the river) but it can move a little. It’s bopping on the water, floating at whatever height the waterlevel is at, but at the same time acting as a dam and trapping water on its upstream side, thus influencing the waterlevel. So this is basically a recharge-discharge oscillator. Maybe. Or maybe not. Any ideas, anyone? This is really tricky!
12:38pm — Gabriela (Lüneburg)
11:49am — Gabriela (Lüneburg)
11:39am — Gabriela (Lüneburg)
11:20am — Katharina (Hamburg)
I guess I said I liked a challenge… Screenshots with comments below! And check out the sound in the movie! Volume up!
10:46am — Astrid (Hamburg)
10:38am — Sara (Klein Waabs)
10:37am — Florian (all over the world!)
9:09am — Gabriela (Lüneburg)
Honestly, what jumps at me most is my ADORABLE niece who’s saying Kaffefoto (“coffee pic”). But then there is also the puzzle of why the coffe coming out of the machine looks so much lighter than when it’s in the mug (underneath the foam)? Well, the foam is the clue here! When there are a lot of airbubbles in the coffee still, they reflect light differently (i.e. from all different directions, making it look white, rather than directional, showing either the color of the coffee or a reflection) than when the coffee has settled down and the air bubbles have gone away.
9:01am — Kristin (hiking somewhere near Bergen)
9:01am — Siddharth (Sadashivnagar)
Oh I love this! I think that what Sid doesn’t show us on the very right is a narrow connection to a second body of water, on which waves are generated by wind. (Alternatively, there might be something there at the very right just outside the frame that is making waves, such as a bird or a fountain, but I don’t think that’s the case. Birds usually don’t move this regularly for long enough to generate this wave field even before you started filming and then throughout the whole movie. Fountains usually generate concentric waves (unless there are several fountains, in which case this would be a trick question ;-))) So let’s assume that wind-generated waves from a second body of water pass through a narrow inlet onto this pond. As they pass the narrowest part, they start spreading to all directions, forming concentric waves that grow over time. Well, almost concentric, because the narrowest part isn’t a perfect point source. Therefore we don’t see diffraction at a slit, but rather at a wider opening.
8:58am — Torge (Kiel)
Not a picture, but even better: He managed to fix the problem we had been having with the co-rotating video of our rotating tank. Super excited! If I wasn’t so busy today (slightly underestimated how many pics my dear friends would send me!) I would go try it out right away!
8:51am — Sam (Manchester)
8:28am — Ronja (Nordsee)
8:13am — Elsa (Bergen)
7:26am — Kati (Schönbrunn, Wien)
7:07am — Marisa (Hamburg)
6:26am — Désirée (Möhnestausee)
6:17am — FrozenBike (Khajoo Bridge in Isfahan)
I’m posting a couple of screenshots from that video to make it easier to discuss…