I find it really fascinating to watch waves being bent by objects in their way. See how the wave is spreading out from the little slit?

Or here how waves are coming in with straight wave crests that get bend once they run into the lee of the pier?

Wavelength dependency of wave-object-interactions

Wavelength dependency of wave-object-interactions. What a title! :-) But that is exactly what I observed over the enormous timespan of three full minutes (as shown by the time stamps of my camera) when I went strolling along Kiel Fjord one Saturday morning.

First, I saw this old, overgrown tyre in a wave field that was dominated by small wind waves. We clearly see how they are diffracted around the tyre and how there is a nice interference pattern downwind of the tyre (to the left in the picture below).

Tyre in the Kiel Fjord and diffraction of small wind waves around it, leading to a beautiful interference pattern to the left of the tyre

Also I quite like how there are absolutely no waves inside the tire, where the wind is shaded off by the tyre and the stuff growing on it.

Then, a really short while later, the wave field was dominated by longer waves running in from the distance. Below, we still see remnants of the old interference pattern to the left of the tyre, but also how the longer waves run around it. In the picture below, the wave crest that was broken up by the tyre is about to rejoin.


And then, only an instant later, this is what the wave field looked like. Hardly and ripples caused by local wind, but many short waves. No real interaction between tyre and waves visible any more.


Isn’t that fascinating? And it all happened within three minutes! :-)

P.S.: Still looking for a christmas present for your nephew, your friends’ kid, your geeky friend? Check out my book! :-)

Another wave hunt expedition: Learning to discover ocean physics wherever you go

One of my favourite topics right now: Learning to “see” ocean physics wherever you go. For example here: A visit to my goddaughter in Schleswig, and this time we are practicing all she and her mom read about in MY BOOK (and if you have good ideas for a title for that book, please let me know!). So today I’m showing you pictures of phenomena similar to those in my book, but discovered on this recent visit.

For example diffraction when waves pass this pier:


In the image below, I’m showing what I mean: Waves coming in from the right have straight crests (red). As they pass the pier, they get diffracted and bent around (green).

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In this spot, this phenomenon can be seen on most days. I wrote about it before, but I have more pictures from previous visits, where the same thing happens in the opposite direction, too: Waves propagating in from the left and being bent around the pier to the right.

Or we can see other wave crests, meeting a rock that breaks the water’s surface.


Those waves (shown in red in the image below) get reflected from the rock, and circular waves radiate away from the rock (green).

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A similar thing can also be observed from a flag moored out in the water:


This time, incoming waves are green and the circular waves radiating off the flag are red.

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And we also got to see awesome criss-crossing again, albeit in a different spot:


Here we have the red wave crests coming in, and the green reflections.

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If we look at it from a little more distance, we can also see another phenomenon: The wave crests are refracted towards the shallower shore:


Again the red crests are the original, incoming ones, and the green ones are the reflection:

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And then finally, let’s look at duckies again. And on waves being created by wind:


Below you see the direction of the wind (white): One side of this little channel is shaded from the wind, so hardly any ripples there. But then on the other side, we clearly see ripples and small waves. And we see the wake the ducky made!

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And one last picture: Which direction does this little channel flow in?


Yep. From the left to the right!

If you enjoy discovering this kind of stuff on your walks, or know someone who enjoys it, or want someone to learn to enjoy it, you might want to consider checking out my book. In my book, I show many pictures like those above, but I actually explain what is shown in the pictures rather than assuming (like I do on this blog) that my readers are oceanographers anyway… :-)

Diffraction and reflection of waves

Last night, we saw really nice wave phenomena on the Schlei in Schleswig.

Do you see the waves being diffracted by the pier in the picture below?


Waves are coming in from the right (see the three lines on the right in the picture below) and at the head of the pier they get bent around (all other lines).

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Now look at the line on the very left. What happens where that wave hits the pier?



Awesome criss-crossing of wave crests!


An annotated picture of what happens below: The red lines show the incoming original wave crests, and the green lines show the wave crests of the wave that got reflected by the shore.

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If all those lines are a tad confusing, thankfully a ducky in a fairly wave-less spot made a single wake which also got reflected on the sea wall:


Same picture as above, this time with the original wake marked in red, and the reflected wake marked in green:

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Nice evening, isn’t it?


And since everybody else is asleep, I put together some short video clips into a movie for you:

What I learned from the movie-making? I need to take longer footage and practice my editing-skills! :-)

Wave hunt expedition. You don’t need to live close to the coast to observe all kinds of wave phenomena!

Waves on Aasee in Münster. By Mirjam S. Glessmer

A 1.5 hour walk around a lake — and 242 photos of said lake — later I can tell you one thing: You definitely don’t need to live close to the coast in order to observe wave phenomena!

The idea to go on a “wave hunt expedition” is actually not mine (although it definitely sounds like something I could have come up with!), it’s Robinson’s idea. Robinson had students go on wave hunt expeditions as part of their examination, and present their results in a poster. I was so impressed with that, that I had to do it myself. Obviously. So the second best thing about work travel (right after the best thing, again, obviously!) is that I find myself in a strange place with time on my hand to wander around and explore. Not that Münster might not have been a nice city to explore, but the lake…

Anyway. I only want to show you 53 out of the 242 pictures. I was going to annotate all of them so you actually see what I mean. And I started annotating. But since I am giving a workshop tomorrow (which is all prepared and ready, but I do need my beauty sleep!) I only drew the key features in the pictures, and you will have to come up with the correct keywords all by yourself (have your pick: refraction! diffraction! fetch! interference! :-)) So click through the gallery below and see first the original photo and then one that I drew in. Do you spot the same stuff that I saw, or what else do you see? Let me know!

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If you think it would be useful to see all those pictures with proper annotations and descriptions at some point please let me know. I might still be excited enough to actually do it, who knows…

P.S.: I actually really enjoy work travel for the work parts, too. For example, I went to a great workshop in Dortmund earlier this year to learn about a quality framework for quantitative research, and that workshop was amazing. And a week ago, I went to Stuttgart for a meeting with all the fellows of the Stifterverband für die Deutsche Wissenschaft, which was also great. And now I am giving this workshop in Münster, that I am actually really excited about because I managed to condense pretty much all I know about “active learning in large groups” into a 2.5 hour workshop. Just so you don’t get the wrong idea about my priorities. Obviously water comes first, but then work is a very close second ;-)

Diffraction of light

Today I’m playing with the sun.

As I mentioned in the sun dog post already, I recently went on the ferry from Kiel to Gothenburg. And I had plenty of time to watch the sun rise and set.

One thing that kept me entertained for quite a while is to squeeze the sun through the imaginary eye in the mast:


As the sun moved behind the mast (or as I moved in front of the mast, whatever), the sun seemed to get pinched in while passing.


Watch the video below to see the whole thing in action:

Also highly entertaining: Watching how the sun eats into my finger tips as I bring them together in front of the sun:

Kids. If you try this at home, please make sure you only look at the sun on the display of your camera, never look directly into the sun…