Category Archives: observation

Opening speech for Wlodek Brühl’s art

You might remember that I had the honour of giving a speech at the opening of Wlodek Brühl’s art exhibition back in spring. Preparing my presentation for the Science in Public conference in Manchester next week (that I am immensely looking forward to!), I noticed I never posted the speech. Below is what I sent Wlodek in advance to prepare him for what I might say:

Lieber Wlodek, sehr geehrte Damen und Herren,

es ist mir eine große Ehre, die einleitenden Worte auf dieser Vernissage, dieser Eröffnung der Ausstellung von Werken Wlodek Brühls, zu sprechen und Sie hier Willkommen zu heißen.

Obwohl genau das die Wortbedeutung von „Laudatio“ist, ist mir ausdrücklich untersagt worden, den Künstler zu loben – vom Künstler selbst. Also werde ich heute lieber über Physik sprechen. Wenn Sie die Bilder von Herrn Brühl betrachten, denken Sie dann nicht auch sofort und unausweichlich über Physik nach?

Springbrunnen kennen wir zu Genüge, in Pfützen fallende Tropfen auch. Und letztendlich sehen wir hier genau das, wenn auch mit etwas mehr technischem Aufwand umgesetzt, um die entstehende Skulptur ganz genau beeinflussen zu können. Deshalb kommen uns die in diesen Fotografien gezeigten Formen seltsam vertraut vor – richtig gesehen haben wir sie aber noch nie. Auch wenn genau solche Strukturen um uns herum existieren (und dabei ist anzumerken, dass jede dieser Skulpturen einzigartig ist, wie auch keine Schneeflocke exakt einer anderen gleicht), mit bloßem Auge können wir sie nicht erkennen, weil sie nur für Bruchteile von Sekunden bestehen und unser Gehirn schlicht zu langsam dafür ist. Solche Skulpturen trotzdem bildlich festzuhalten gelingt mit vielen technischen Tricks: Mit computergesteuerten Ventilen, die Tropfen so auslösen, dass sie genau mit anderen Ventilen, dem Blitzlicht zur Beleuchtung und dem Auslöser der Kamera abgestimmt sind. Sichtbar werden dann Skulpturen und nicht nur verwischtes Wasser, weil die Skulpturen in einem stockdunklen Raum für ein Bruchteil einer Sekunde von einem Blitz beleuchtet werden, so dass trotz der längeren Belichtungszeiten der Kamera auf dem Bild nur dieser eine, enorm kurze Moment sichtbar wird, in dem es – exakt zum richtigen Augenblick – geblitzt hat.

Aber kommen wir zur Physik. Wenn Sie diese Ausstellung bei – aus physikalischer Sicht – einfacheren Bildern anfangen und sich dann langsam steigern möchten, würde ich empfehlen, in diesem Raum zu beginnen.

My picture of art by Wlodek Brühl, taken and published with kind permission.

Hier drängt sich mir zum Beispiel die Frage auf, warum die Skulpturen von unten aus dem Wasser nach oben zu wachsen scheinen, bevor sie sich ausbreiten, verzweigen? Der Schlüssel hier ist die Oberflächenspannung des Wassers. Die Wasseroberfläche, durch einen fallenden Tropfen nach unten ausgelenkt, schleudert den Tropfen wie ein Trampolin wieder nach oben und wölbt sich selbst hinterher, bäumt sich auf, bevor sie wieder in sich zusammen fällt. In einigen der Bildern kann man diesen nach oben geschleuderten Tropfen sogar noch erkennen.

My picture of art by Wlodek Brühl, taken and published with kind permission.

Und dann sehen wir im oberen Teil vieler der Skulpturen Formen, die wie Schirme oder Leselampen aussehen, oder wie Vasen. Warum sind diese Strukturen manchmal nach oben geöffnet, manchmal nach unten, manchmal voller filigraner kleiner Ärmchen am Rand? Das sind eigentlich schon zwei Fragen in einer. Die Form der Kelche hängt davon ab, wie schnell sich zwei Tropfen aufeinander zu bewegen und ob ein großer auf einen kleinen trifft oder umgekehrt. Die kleinen Ärmchen sind Instabilitäten, die entstehen, kurz bevor der Schirm zerfällt. Schirme ohne Ärmchen sind also genau in dem Moment belichtet und eingefangen worden, als noch alles stabil war. Bruchteile von Sekunden später wären auch sie instabil geworden.

My picture of art by Wlodek Brühl, taken and published with kind permission.

Und wenn Sie mit diesem Blick durch diese Ausstellung gehen, werden Ihnen noch viele andere Fragen kommen. Manchmal, zum Beispiel, sehen wir Skulpturen, die auf zwei Säulen zu ruhen scheinen. Wie sind diese wohl entstanden? Und dann sind die Skulpturen farbig – und die Farben sind direkt in der Aufnahme entstanden und nicht nachträglich digital eingefärbt. Das wurde in diesem Raum durch farbige Blitze gemacht, in den anderen beiden Räumen durch eingefärbtes Wasser.

My picture of art by Wlodek Brühl, taken and published with kind permission.

Wenn Sie als nächstes dann in den Raum dort hinten weitergehen, sehen Sie Skulpturen, die an der Wasseroberfläche gespiegelt sind. Durch die Spiegelung hat man auf ein mal zwei unterschiedliche Perspektiven auf die Skulptur und kann jetzt Strukturen noch genauer beobachten, um über sie nachzudenken.

My picture of art by Wlodek Brühl, taken and published with kind permission.

Im dritten Raum sehen Sie die neuesten Kunstwerke von Herrn Brühl, die vor wenigen Wochen erst entstanden sind. Hier wird die Physik noch komplexer. Zusätzlich zu all dem, was ich gerade schon über fallende Tropfen erzählt habe, kommen hier noch mit Druckluft angetriebene Fontänen hinzu. Und zwar einfache, die in der Mitte der Skulptur gerade nach oben schießen, und dann auch solche, die aus einer sich drehenden Turbine nach oben und außen geschleudert werden, erst einen Kelch bilden und dann in einzelne Tentakel zerfallen. Und in diesen Bildern sieht man manchmal auch die Schlieren und Pigmente der verwendeten Farben!

Wenn man wollte, könnte man an jedem einzelnen Kunstwerk stundenlang beobachten, grübeln und diskutieren. Wie sähe eine Skulptur wohl aus, wenn ein Tropfen größer gewesen wäre als er war, oder etwas später gefallen, oder vielleicht aus einer anderen Höhe? Oder wenn das Bild Sekundenbruchteile eher oder später gemacht worden wäre und uns damit einen anderen Zeitpunkt der Entwicklung und des Zerfalls der Skulptur gezeigt hätte? Was, wenn anstelle von Wasser zum Beispiel mit Honig gearbeitet würde? An Ihren Gesichtern sehe ich, dass diese Fragen Sie schon jetzt faszinieren. Das ist genau die Physik, die ich speziell bei den Tropfenskulpturen von Herrn Brühl so fesselnd und aufregende finde!

Ich wünsche Ihnen viel Spaß in dieser Ausstellung – dass Sie die beeindruckende Kunst von Herrn Brühl als Kunst genießen können, aber dass Sie sich vielleicht an manchen Stellen auch fragen, wie genau er es wohl geschafft hat, solch ein Meisterwerk entstehen zu lassen. Ich bin mir sicher, dass Herr Brühl Ihnen gerne Rede und Antwort stehen wird! In diesem Sinne: Herzlich Willkommen!

Algae as tracers for currents in Parsteiner See

Remember how I described a breeze creating a wave field on Parchsteiner See?

Well, it did not only cause a wave field, it also set up a circulation! Which I might not have noticed, had nit not also started deforming the algae patches! At first, it looked like above, and we could walk into the lake without having to wade into the green, like so.

But then a little later, there were algae everywhere, and you could see the swirls in the current traced out in green! Pretty cool passive current tracer, aren’t they?

Soap bubble musings

I have too many soap bubble pictures from last weekend’s trip to Kleinwaabs to not write a post about soap bubbles. So let’s get right into it!

First thing I never actually thought about: Why do you want soap to make soap bubbles? Soap lowers water’s surface tension (and see my favourite surface tension experiment here!), so wouldn’t that make bubbles more fragile than just using water? Turns out that without soap, there are hardly any bubbles because water’s surface tension is so high that it tends to lump water together into compact round shapes: so just drops, no bubbles. Which I should have known right away, obviously. So we need the soap as surfactant to keep the insides of the soap bubble apart and prevent collapse into drops.

So let’s look at how soap bubbles form. When someone (Frauke in this case) blows at the soap bubble wand, at first something resembling a wind sock forms (see above). Only after a little while it detaches and closes off bubbles that float away.

Soap in soap bubbles also produces the surface films that make soap bubbles look so pretty. And if you look at them closely, you can even see currents on soap bubbles as water and soap are flowing around on the surface!

Those currents are also one of the mechanisms that will ultimately make the bubbles pop: As gravity pulls the denser water to the bottom of the bubble, the soap concentrates on top. The more soapy the water, the lower its surface tension, so at some point the surface tension becomes too low to keep the bubble together — it pops.

Another mechanism making bubbles pop is just evaporation: As bubbles have a large surface, water evaporates fairly quickly from it, thus leaving more and more soapy water in the bubble. Until, you guessed it, the surface tension becomes so low again that the bubble pops.

A third reason for bubbles popping is also them floating into something which then breaks the surface. If bubbles float into other bubbles, though, this usually doesn’t result into them popping — they stick together and form interesting shapes of round segments and straight dividing walls. Surface tension always tries to minimize the surface area, balancing inside and outside pressure, so these are the energetically best shapes.

Interesting how that sometimes happens, while other times bubbles float nicely their separate ways, sparkling and shimmering in the sun.

And funny how difficult it is to take pictures of soap bubbles. Thanks for your patience, Frauke! :-)

A “Siel” – the valve in a dyke that lets freshwater out but no salt water in

Ok now, after complaining about how I dislike mud and the “no water” (i.e. low water) times in the Wadden Sea yesterday, today I’ll tell you about some stuff I really love about the North Sea coast. For example, the pretty little villages full with shrimp trawlers everywhere!

Picture above is Neuharlingersiel, below is Dornumersiel.

And the pictures below are from my favourite “…siel” so far, Greetsiel. Even though I unfortunately didn’t take any pictures of the village itself! I was so fascinated with all the shrimp fishing vessels.

The boom trawlers with all the colorful nets and ropes and everything are just too pretty, even on an otherwise fairly miserable day!

But what I find fascinating in all the “…siel”s is how they bring together a nautical atmosphere (after all, most of these ships have been out on the open North Sea all night!) and a very inland-pretty-old-town vibe. And here is how they do that: with the “Siel”. The “Siel” is basically a valve that lets freshwater out into the sea, but which doesn’t let salt water come back in. The way that is done by doors that are opened if the pressure on the inside (i.e. the land side) is higher than on the outside, and that close if the pressure on the outside is higher than on the inside. Pretty smart, ey? That way the land gets drained during low water, but no salt water comes inland to mess up the agricultural land. But I find it fascinating how this one little door in a dyke can separate two completely different habitats that coexist peacefully just one step away from each other.

Above, you are looking from the inland on such a “Siel”, which is currently closed because the water is higher on the outside than on the inside.

Oh, and what I always love: Light houses!!!

Yep, so I definitely have to go back. Stay tuned! :-)

Who enjoys playing with water clearly even more than me? An eager beaver!

Work took me to Brodowin (a village northeast of Berlin that is situated in a biosphere reserve and does amazing organic farming). The public transport, however, only took me to Chorin, which is a 1h 5min walk away from Brodowin — if you walk at the pace suggested by my app. Not, however, if you come across stuff like this:

This was the first time I’ve spotted evidence of beavers in the wild, and this time I was just walking all by myself through the forest and couldn’t believe my eyes! When I talked to locals later, they were all like “yeah, it’s a real nuisance around here, they flood acres and are really annoying!” but I was absolutely fascinated seeing their dams, and imagining what even better dam they will be able to build if that tree falls in the right direction, across that little stream. Really hope it does!

The water on the left in the picture above looks so weird, btw, because there is a lot of dust and pollen and stuff floating on it, that is stopped by the dam, while some water clearly manages to filter through. And ideally I should have jumped across the little stream to take better pictures, but there is a limit to what I am willing to do for a good picture. If only they had already gnawed that tree down, there would have been a convenient bridge across… But I will be back to check on their progress! :-)

Roll waves in the sand dunes? Observing erosion

On our trip to the west coast yesterday, I observed something really cool: Sand roll waves (I think!) in the sand dunes!

But before I get to that, this is the setting on Sylt. A sandy beach opening up to the North Sea, that is separated from the land by sand dunes which are overgrown with some kind of beach grass.

Yesterday was a windy day as you see from the waves, but neither was the water level very high, nor was the wind anywhere near as strong as it gets here during winter storms, so the erosion happening yesterday is not very strong compared to what it is like during more extreme weather conditions (and the process I am focussing on here is probably one of the least important ones).

In order to prevent erosion of the dunes which protect the inland from storm surges etc, it is crucial that the beach grass growing on the dunes isn’t stepped on by the hundreds of tourists visiting this beach every day (probably thousands during summer). Therefore there are these wooden staircases installed in regular, short intervals to bring people across the dunes without them doing any damage to the vegetation.

Therefore, in most places, the dunes look like this.

In some places, though, there is little or no grass growing on the dunes, so imagine what kind of damage strong winds can do here, let alone a storm surge!

And in one of these open sand areas I observed what I think are roll waves. Do you see what looks like a drag mark a little right of the center in the picture below?

Check it out in the movie below (it zooms in after 5 seconds to show it more clearly) — there is sand surging down this track! To me this looks very similar to roll waves, and I know roll waves have been observed in sediment flows and lots of other places, so why not in the sand of these dunes? What do you think?

A different kind of drop photography today…

After all the professional drop photography I talked about yesterday, here is some of my own from a walk that I took after the amazing and slightly overwhelming experience of giving the laudation speech at the opening of an art exhibition.

Below, I really liked how the wave rings have such different sizes and amplitudes depending on whether they were made by rain drops or ducks (you might have to click the image to enlarge to see what I am talking about).

And below, I love so much about this picture. The long waves with the very small amplitude that are coming into Kiel fjord from some far-away storm. The short waves and small scale turbulence that is created where wave crests just manage to flood a step on the staircase, but the water then flows off it again during the next wave trough. The small speckles made by rain drops. The fact that it seems to almost be summer again because the beach chairs are back! And, of course, that I caught the splash and the flying drops of the wave.

I read this poem by E.E. Cummings on Saturday that really speaks to me. It ends in

“For whatever we lose (like a you or a me)
it’s always ourselves that we find in the sea”
E.E. Cummings

Vernissage of “liquid art”: The perfect opportunity to combine art & physics to do some scicomm!

If you don’t want to “preach to the choir”, how do you, as science communicator, reach new audiences occasionally?

One way that I tried today is to give the (invited, I swear!) laudation at the vernissage of Wlodek Brühl‘s exhibition on “liquid art“. The idea was that visitors would mainly come to the event because they are interested in art itself, but that I will try to give them a new perspective on the art by exposing them to the science behind it. Which I think is a pretty cool concept!

Yesterday, I got a sneak peek into the exhibition which features new art that isn’t even two weeks old! I took pictures of some of the art to show on this blog (with Wlodek’s permission!).

Let’s start with a sculpture that isn’t even part of the actual exhibition but that is displayed in my living room (and I love it!!!): A very simple drop sculpture. A drop fell onto a water surface. Due to surface tension, the water surface deformed, got pulled down, bounced back, overshot, and a drop shot up again, pulling a thin trail behind it. As the drop was flying upwards, it got hit by a second drop which fell straight on it. That second drop splattered into this umbrella, which is starting to disintegrate into small instabilities that form tiny filaments. A fraction of a second later and the whole thing would have collapsed and look totally different.

My picture of art by Wlodek Brühl, taken and published with kind permission.

That’s part of the art of capturing these sculptures: timing. Not only does one need to be super precise in the timing of drop releases, one also needs to capture the exact right moment to light the dark room with a flash, which is a lot shorter than the exposure time of the camera. Of course it’s all controlled by a computer!

But here is an impression of the exhibition itself.

My picture of art by Wlodek Brühl, taken and published with kind permission.

I’d like to start out with some of the older art from 2016 which is easier to explain: “Simple” drops like you see to the right of the door above, then double pillars to the left of the door, and then reflections, before we move on to the kind of art that you saw at the top of this post.

In the picture below, what happened is pretty similar to what happened in the picture above: A drop fell, bounced back up again and was hit by a second drop. The second drop hit the first one when that one was still fairly fast, therefore the vase-like structure. (And don’t you just love the waves that you see on the water surface? I feel like I see the actual dynamic process of the surface rising up!)

My picture of art by Wlodek Brühl, taken and published with kind permission.

Or below, another similar setup, except here the drops collided in such a way that the larger, bottom one formed an umbrella-like shape, whereas the upper one rose as a vase.

My picture of art by Wlodek Brühl, taken and published with kind permission.

It gets more complicated if two drops are released simultaneously as below, and then a third one hits them in the middle with a little time delay to form the umbrella, and a fourth drop is still falling down and hasn’t reached the sculpture yet.

My picture of art by Wlodek Brühl, taken and published with kind permission.

So much for the “simple” structures, now on to more complicated ones. The ones below are similar in their setup to the ones above, but now they are photographed against a black background and in a large, black dish. Therefore we see the reflection of the sculpture on the water surface. This lets us look at different structures within the sculpture from two angles, making it even cooler to think about all the physics going on here!

My picture of art by Wlodek Brühl, taken and published with kind permission.

But now on to stuff done with more fun toys:

These are the newest works of art that Wlodek did only within the last two weeks! I personally prefer the translucent, fragile, light sculptures like the one in my living room, but I can also really appreciate those bouquets of spring flowers for their dynamic and lively shapes.

My picture of art by Wlodek Brühl, taken and published with kind permission.

Below I am showing a larger version of the sculpture to the very right above. In these new sculptures, Wlodek isn’t “only” working with drops, but now he has started to incorporate colored jets that are driven up by pressurised air. See how the yellow central jet broke through the umbrella formed by the orange drop that dripped on it from above?

Additionally, Wlodek is building vases around the bouquets by pushing dyed water through a rotating turbine. This vase breaks up into tentacles when it gets unstable!

The sculpture below is called “sundae with umbrella” and I cannot un-see this!

My picture of art by Wlodek Brühl, taken and published with kind permission.

But mostly I see flowers, specifically orchids. Below, the yellow drop from the top didn’t hit the green-ish jet from below completely center, therefore the latter broke up and seems to be turning towards us, wrapped in the orangey-yellow vase that has become very unstable on one side, but not so much in the back. Don’t you just love how the rims bulge together due to surface tension?

My picture of art by Wlodek Brühl, taken and published with kind permission.

In any case, I had a blast, even though, judging from the picture below that shows me giving the laudation, it doesn’t seem like it. Do I always look this serious? But the feedback I got was that everybody enjoyed looking at Wlodek’s art through a physics lense, at least after they got over their initial shock that they would have to listen to physics on their artsy Sunday morning. So this is definitely a scicomm format I want to explore more!

Me (in stripes) with the artists Regine Hahn (left) and Wlodek Brühl, as well as the host, chairwoman of Kunstkreis Preetz. Picture by Frauke Voitle, used with permission.

Intriguing interference pattern of waves

Do you see those weird traces going away from us, perpendicular to the wave crests, but in parallel to the bright stripes on the sea floor (I talked about those in yesterday’s post), looking almost like waves but not quite? What’s going on there?

Something very cool! :-)

In the gif below, I have drawn in several things. First, in red, the “weird” tracks that we are trying to explain. Then, in green, the crests of two different wave fields that are at a slight angle to each other. I’m first showing one, then the other, then both together. Lastly, I am overlaying the red “tracks”.

So this is what those tracks are: They are the regions where one of the wave fields has a crest and the second one has a trough (i.e. where we are right in the middle between two consecutive crests). What’s happening is destructive interference: The wave crest from one field is canceled out exactly by the wave trough of the other field, so the sea level is in its neutral position. And the wave fields move in such a way that the sea level stays in a neutral position along these lines over time, which looks really cool:

Some more pics, just because they are pretty and I like how they also show total internal reflection :-)

And don’t you just love the play of light on the sea floor?

And even though these weird neutral sea level stripes are parallel to the bright stripes on the sea floor, I don’t think that the latter one is caused by the first. Or are they? Wave lengths seem very different to me, but on the other hand what are those stripes on the sea floor if they aren’t related to the neutral stripes in the surface??? Help me out here! :-)