This is the story of a pilot ship, merrily sailing along on a beautiful day, making waves.
Since it’s windy and Kiel fjord is a little choppy, the waves break and both side of the V-shaped wake with the pilot ship at its tip are visible. See the foam of the breaking waves? And in the middle of both sides of the V, visible as a lighter-colored stripe, there is the turbulent wake where the ship’s propeller has set the water into chaotic motion.
Both constituents of the wake — the V-shaped feathery waves and the turbulent wake — stay visible for quite some time after the ship has passed!
Can you spot the one side of the V approaching the shore?
A little while later, the pilot ship returns. nice bow wave (where its bow is breaking the water apart) and all. Also note the wave field inshore of the floating wave breaker — it is a lot calmer than on the outside!
Ok, let’s start with something simple to warm you up: A duck’s wake.
And wind waves (coming in from the top right) hitting a patch of moss on the side of this little pier, and then radiating away as half circles.
Here is a movie of that because it’t pretty cool, actually.
Are you ready for the cool stuff? A water strider making waves in the movie below! It hops happily on the water, and every time it lands, capillary waves radiate outward from its point of impact.
And in the movie below, there is another water popping up after a couple of seconds. But what I find fascinating about the movie below: In the beginning, there are these smooth waves running through that were created by a breeze further upwind on the lake. But over the course of the movie, the texture of the surface changes: It gets rougher and ripples appear as the breeze moves in where I am filming. So within half a minute the lake looks substantially different!
And below a movie clip that should be used in physics classes because it illustrates so nicely that waves transport energy, not matter. How do we see that?
Can you spot the long waves going through right to left, and the small ripples that seem to, if anything, move from left to right? (Not true, that’s an optical illusion! They are moving right to left, too, only so much slower than the longer ones)
But if water was moving with the longer waves, the small waves would have to be transported with it, just riding on the other wave field. Clearly that is not the case! And that’s because only energy and the shape of the waves is transported, not the actual water the waves consist of.
And below is the picture that I would use to open my hypothetical wave photography exhibition with. Or maybe have it printed in a size to fill a whole wall if I ever had to furnish a large house.
What do you do the night before the most important three days of your whole work year? Yep — some wave watching with friends!
On Thursday night, we went to cool down and relax after preparing for GEO-Tag der Natur all day long. Don’t these images make you feel much more calm instantly?
And look at the waves in the atmosphere that only become visible because, as air is moved up and down by the waves, conditions change such that clouds form in the troughs but disappear at the peaks of the waves. Contemplating these things is so relaxing to me! Especially when looking at them both in the sky and in their reflection on the water.
And if you look carefully at the picture above, you see tiny little wave rings in the lower right corner. That’s small fish touching the lake’s surface from below, creating disturbances that propagate away from where the surface was deformed.
Other things make similar pattern, albeit on a larger scale. My colleagues K and K, for example, are creating wave rings, too. Theirs are much larger and propagate all the way across the lake!
And thanks to K&K’s waves, the reflections of the atmospheric waves on the water becomes even more interesting as they are deformed by surface waves on the lake.
Is there any better way to calm down any worries you might have?
And, btw, the GEO-Tag der Natur turned out a blast. I’ll update you on that once I’ve had A LOT OF SLEEP! Until then — go and do some wave watching! :-)
So today (and tomorrow and the day after) is the big event that I have been working towards all year in my not-so-new-anymore job: The GEO-Tag der Natur! If you are curious about what’s going on there, check out our Instagram account @geo.tag.der.natur that Kati is doing an amazing job with!
As you can imagine, the weeks running up to this weekend were quite busy and a little stressful, too. So last Sunday I went to the beach to hang out with friends and do some wave watching! Because nothing has a more calming effect on me than watching water…
For example below we see nicely the effect of the wave (and wind) breakers on the wave field. In the lee of the wave breaker, the water is completely calm, whereas towards the right of the bay waves form and grow larger and larger.
And below we see a pretty cool “diffraction at slit” example: Straight wave fronts reach the slit between two wave breakers, and as they propagate through the slit, they become half circles.
But to relax and get my thoughts away from my job, I tried something new: I created and posted my first ever Instagram story! I’m not quite sure it’s my format, but I definitely had fun! What do you think? Would you like to see more of those? (I only just realized the story is in german and my blog in English. Posting anyway… Would anyone like to see this kind of stuff in English? Then please let me know and I’ll see what I can do…)
(P.S.: Since I made this for Instagram, the format of the video was optimized for viewing on a mobile phone. Therefore it looks crap embedded in a blog. But some you win, some you loose…)
What do you do to relax and get your mind off of work? Wave watching and posting about it on social media? Have you ever tried that? Or what else would you recommend?
This is a #friendlywaves challenge, where I try to explain other people’s wave photos and they tell me how I did.
I love it when my friends see waves, think of me, whip out their cameras, take pictures, and send them to me! In this case, Nena even used a telephoto lens and took the amazing pictures below that she allowed me to share with you!
They are the perfect example for talking about wakes when a ship doesn’t just go straight ahead. Because, of cause, ships going straight ahead are the easiest case, like the one we see below.
Picture by Nena Weiler, used with permission
Here, we see the two different constituents of a wake: The turbulent wake that is the white stripe right behind the boat, that turns blue a little way behind the boat but stays a lighter color than the surrounding water.
And then there is the V-shaped wake with the boat at its tip. This V-shaped wake consists of very many individual waves that are fairly short in the direction parallel to their crests, and that are shifted slightly so the further away from the boat you look, the wider the V opens. I usually call this the “feathery” wake, since it consists of all these little “feathers”, but since I need the “feather” image for something else today, I’ll just call it the V-shaped wake here.
Now when the boat takes a turn, this messes up the structures of the waves making up the V-shaped wake (or makes them more interesting, depending on your point of view). Below, the boat has taken a right turn, which you can see from the turbulent wake that starts right behind the boat as a white stripe that then changes color to a lighter blue than the surrounding water (with a darker stripe to each side, and then the V further out).
Picture by Nena Weiler, used with permission
Now looking at the individual waves of the V-shaped wake, we see that they get bunched up on the right side of the boat’s trajectory, while they are getting fanned out on the left side.
Now imagine the boat’s trajectory as the shaft of a feather. If you have ever bent a feather, you will have observed that on the side the shaft is bent towards, the individual barbs (I looked this up: barbs are the little thingies that spread outwards from the feather’s shaft) get bunched together, while on the other side they fan open.
So far, so good. Still with me?
Now what happens as time goes on is that the V opens up — the two sides move away from each other. We don’t usually notice this because we are used to focussing on the wake relative to the ship rather than to some fixed vantage point. But if we looked at a fixed point while a ship going past, we’ll see the wake spreading over time until one side of the V reaches us.
Picture by Nena Weiler, used with permission
And this spreading of the V is what’s making interpretation of the picture below a little difficult. The picture below is showing almost the same part of the ocean as the one above (see the little white and blue moored boats in the bottom right corner of the lower picture? They are the same boats that are visible at the left of the bottom right corner above), only a little later. During the time between the two pictures, the ship moved further towards the bottom left corner, but also the wake spread further apart.
Above, you see that some “barbs” start running into each other (the ones where the bend is strongest, where there is foam on breaking waves because the waves suddenly become a lot steeper due to interference). So some time later, they have grown longer and are now crossing each other, which leads to the checkerboard pattern located right inside the bend of the boat’s trajectory. If you follow the V-shaped wake from the boat backwards, you can still make it out, even though it’s been deformed by the ship turning around.
Picture by Nena Weiler, used with permission
Tell me, Nena, is your family happy with this explanation? :-)
A week ago already, Frauke and I went on an evening walk in Kiel Holtenau. Beautiful wave watching to be done there as always! Here you see the one side of a ship’s V-shaped wake approaching our vantage point. You can see the individual “feathers” of the wake: Short wave crests, all parallel to each other, but slightly shifted to the side to form a straight line (well, two straight lines to form a V with the ship at its tip, but the other side of the V is not visible on this picture).
And this is what it looks like when the wake has moved past us: Looking on the back of the feathery shapes. The ship that made all these waves has long sailed away.
Anyone who has ever read my blog, seen my Instagram, or met me in person knows: The ocean is hugely important for me. The ocean is important for my mental health, looking at water just makes me happy and calm and content. The ocean is also the foundation of life on this planet: It supplies more than half the oxygen we breathe, it moderates temperatures such that I am happy to go swimming in Kiel fjord all year round (ok, that’s also because I am slightly insane), it provides us with food, work, goods.
Today, on World Oceans Day, let’s celebrate the ocean by looking at one specific aspect in which it is amazing, and that is in how much energy it contains. In heat that is stored in it. In dissolved salts. In its movement. You know I am addicted to wave watching, but there is so much more you can do with waves than just watch them, even though that’s not as easy at it seems.
One of my favourite wave watching spots is a broken prototype of a wave power plant close to my friend Elin’s cabin on an island off Bergen. The location was chosen for the enormous wave power that slams up on the coast here most days, and that’s also why the prototype unfortunately didn’t last very long.
In the movie below you see the spot where a turbine used to sit which would be powered by water pressing air up by being funneled into a sub-sea reservoir, and then sucking air back out when the wave retreats. And you see how, by the way the funnel is built, the not-so-enormous waves outside get translated into quite a change inside that hole. Wait for the splash! Can you imagine the movement of the air column above, where the turbine used to sit?
We weren’t even there on a particularly wavy day, so imagine the powers at work here on days with a lot of waves! The forces at work here are enormous. And just because we haven’t figured out yet how to make wave power work well in the ocean’s harsh environment, that doesn’t mean that it isn’t figureoutable!
Picture by Elsa du Plessis, used with permission
Even looking at these pictures and the movie I feel the effect the ocean has to me — giving me a sense of calm purpose and inspiration. Enjoy your World Ocean Day, and make sure to appreciate some water somewhere today! :-)
On our work trip to Brodowin to prepare the GEO-Tag der Natur (which will take place here only a little more than a week from now! Crazy!), I had the chance to do some cool wave watching on different lakes.
Above, for example, you see wind waves coming in from the right, and their very distinct reflection on the left row boat.
Below, at the stern of the left row boat, you see a sudden gust of wind, causing lots of capillary waves, and thus high surface roughness.
And below, what would you guess is the secret to the ring waves radiating away from the end of the pier? It’s a surf board, bobbing up and down in the incoming wind waves!
I just love looking at water, it has such a calming effect on me, even in 35 degrees heat (which I am really not good with).
I love to see how the more lively wave field offshore gets calmed down as only longer wave lengths make it through the water lily frequency filter! And how the wave crests get bend as they reach the shallow shore.
Now, different lake. This one is 38 m deep! Would you have guessed that?
Here you see that we are standing on the downwind side of the lake: Smooth water on the other edge in the lee of the land, then, after sufficiently large fetch, waves that grow more and more the further they have progressed over the lake.
Same lake, same phenomenon, different view.
And the last bit of the lake just to give you an impression of the glacial landscape it is situated in, explaining the very steep slopes and the 38 m depth.
This would be such a lovely place to sit at and enjoy the view, if only there was a little shade…
I find it fascinating how the shape of the waves doesn’t change as they approach the shore. That’s because the shore is so steep that when, at last, the waves start feeling the bottom, they have already reached the edge of the lake and didn’t have time to change their shape.