Water Fountain Powered by Sound Waves

We built a water fountain powered by sound waves! There is a little speaker attached to the bottom of the water basin. Warning: the sound frequencies in the video may be unpleasant!

And here we tried the same with sand. Again, warning: the frequencies may be unpleasant to your ear, so make sure you lower the volume on your device.


Microstructures Interfering With Light

What looks like strange planets in dark space are actually glimpses of the microstructures forming the Giant Blue Morpho’s wings, as seen through a microscope. Simon told me about how a Blue Morpho’s wings aren’t actually blue (have no blue pigment) but appear blue as a result of a physical phenomenon called structural coloration — microstructures interfering with light. This is almost the same phenomenon as iridescence (making a surface appear to change colours as the observer’s angle of view or the illumination angle changes, think of the soap film in a bubble).

We had found Blue Morpho’s wings in the street about half a year ago. Someone threw a small butterfly collection away — several butterflies pinned to a stick. It looked very cruel and we would have never killed a Blue Morpho for the sake of an experiment, but since we stumbled upon such a rare treasure, we picked up one wing and stored it in a book.

Why Cookies Get Bigger in the Oven


Simon is baking Dutch traditional “pepernootjes” (“pepper nuts” or spicy cookies) and explains why they get bigger in size after you put them in the oven and what the optimal tiling pattern is to fit a maximal number of cookies on the baking sheet.

Physics Experiments: Capillary Bowl

Simon really wanted to try building a capillary bowl – a version of a perpetual motion machine in which water circulates. Although aware of the fact that perpetual motion was not possible, he is keen on seeing it for himself. Off we were to the hardware store where we got some funnels and hoses. What we observed was Pascal’s law in action: the level of water evened out and there was no way to get the water rise higher at one end of the hose than at the other and thus no way to get the water flow into the funnel.

Eventually, we did manage to get the capillary bowl to work for a split second when we filled it with coke and beer. The pressure of water is higher than that of foam, because liquid has a higher density than foam. We used alcohol free beer, so there wasn’t that much foam.

Photons Trapped in Flemish Woods

Simon isn’t fond of magic or fantasy. Plus, he is not fond of long walks in the woods. Both “not fond of” are understatements. What was I counting on when I dragged him to the 2 kilometer long light installation in a forest close to Antwerp? I expected that seeing multiple fountains with photons trapped in water would make up for all the magic, scary music and the long walk. And it did!


Inertial Reference Frames

Simon is greatly impressed by the fact that if the Charge-Parity-Time (CPT) Symmetry doesn’t hold, the whole special relativity theory would have to be reconsidered. Does general relativity rely on special relativity? — I ask him. — What is special relativity about?

— It’s about inertial reference frames, — Simon answers.

— And what is that?

— It’s about either something static or moving at a constant velocity, — he gives me this big smile. — General relativity applies to accelerating reference frames!

And I am thinking, what a vocabulary he’s got in English, he talks like a grown-up. It strikes me that he doesn’t talk like this in his native Dutch or Russian. In those languages he sounds much younger, less self-assured, and he makes quite a few grammar mistakes in Russian (his little sis correcting his case forms and genders). What if he wasn’t living this trilingual life? Was communication with the outside world easier for him then? Will it become easier outside the English language that he has embraced so wonderfully? I continue to hold on to the idea that multilingualism can be nothing but enriching in the long run.

Simon explaining Interstellar

Simon didn’t want to watch Interstellar (he generally dislikes fiction and often finds it too scary as well), but somehow he did get sucked into the story after his sister and I were watching the movie right next to him for several days in a row and talking about it extensively. It’s one of my favourite films and I so much wanted Simon to see the part about time dilation and the black hole, and hear his thoughts about those scenes. I admit they were quite difficult for me to grasp when watching the film for the first time, especially the scene where the main character finds himself in the tesseract and has multiple visions of his daughter from the past. When we got to the scene, Simon was on fire. He kept walking around the room, euphoric  as he was explaining to me how he understood what was happening on the screen:

“They used the many worlds interpretation! The many worlds interpretation is an interpretation of the collapsing of the wave function. It says that the wave function doesn’t collapse, we just find ourselves in a universe where it collapsed intone particular possibility. And there is theoretically another universe where something else happened and there is another version of us experiencing that. This produces uncontrollably infinitely many universes just to get out of collapsing the wave function. What they use is  a metaverse – the multiverse of the many worlds interpretation!

Those grids of shelves are the multiverses! And then there’s a grid of those grids of shelves and that’s a metaverse. A metaverse of all of the multiverses of the many worlds interpretation at every single point in time!

I know why it’s 5-dimensional! It’s the 3 dimensions of space, the 4th number indicates what universe it is in the multiverse, and the last number is which multiverse it is in the metaverse! Which is a time dimension, because it’s metaverse of all the multiverses of the many worlds interpretation at every single point in time. And notice, these are all real numbers! Even the 4th and the 5th dimension can be any real number because there are only countably infinitely many natural numbers, integers and even rational numbers”.

Physics Experiments: Slime for Science

We had such a genuinely rewarding homeschooling experience yesterday when we took up Physics Girl’s challenge to recreate the Weissenberg effect – a phenomenon that occurs when a spinning rod is inserted into a solution of elastic (non-newtonian) liquid.

Our first attempts to make slime following Physics Girl’s recipe (1/2 cup PVA glue, 1/2 water plus 1/4 tsp borax dissolved in another 1/2 warm water) failed so we returned to the department store to get starch, a different type of glue and anything else that might help. Did we use the wrong glue? What is borax (originally, we thought it was the same as the salt used to clean the dishwasher)?

After we started asking around, the shop assistants threw in a couple of handy tips (like getting some fluid used for cleaning your contact lenses as it contains something like borax, borate buffers, and mixing that with glue and shaving cream). At the drug store, we got warned about the dangers of pure borax powder if used in large quantities (skin burns), but did manage to get a tiny bottle of the stuff after we assured that it was for an adult supervised experiment. With all this useful info and terribly tired, but fully equipped we returned home and resumed our attempts at mixing perfect slime. You can see for yourself in this unlisted video how we went about it.

Eventually, we ended up adding twice (in not thrice) the amount of borax to finally froth up the right consistency non-newtonian fluid and it just worked!

(Instead of being thrown outward, the solution is drawn towards the rod and rises up around it. This is a direct consequence of the normal stress that acts like a hoop stress around the rod).

Simon wrote: In this video, I make slime “climb” up! It’s because of the “viscoelasticity” of the slime.

Correction: I’ve made a mistake when I said “times H2O”. The dot in the formula didn’t mean “times”, it meant ion.

The borax formula was indeed what Simon called “a mouthful”: Na2[B4O5(OH)4]·8H2O where the dot refers to the elements in square brackets all forming the [B4O5(OH)4]2− ion.

So what is borax? It’s a mineral, a salt of boric acid, also called (di)sodium tertaborate, usually possessing a crystal water content (although the commercially available borax is partially dehydrated).

Thanks to more borax, check out how high our fluid rose – it came out the other side of the straw!

Chemistry Experiments: Colors (surface active agents and pH indicator)

Our new MEL Chemistry box arrived, containing tons of color fun! We have already tried two experiments. In the Color changing milk experiment, the soap touches the milk creating a very thin film of soap on the milk’s surface and causing the colors to spread along with it, producing a mesmerising effect. Molecules of soap and other similar substances lower the surface tension of different liquids and thus are called surface-active agents (SAA). Simon took it a notch further and created antibubbles that glide on the film of soap:



We thought this one looked like a nuclear explosion:


The second experiment we did was called Magic Liquid and felt like performing a magic trick: a yellowish liquid poured in five different cups turned five different colors, almost all the colors of the rainbow! The secret was putting a tiny bit of a different chemical substance on the bottom of every cup beforehand. The yellowish stuff was actually Thymol blue, also known as thymolsulfonephthalein (chemical formula C27H30O5S ), a pH indicator, and changed color according the acidity of the substances that were already in the cups. The larger the quantity of protons H+, the higher the acidity of the medium, while the OH ions are responsible for the basic medium:


Thymol blue molecule visible on the iPad screen:

We also checked the pH of the substances using indicator standard teststrips:

The pH rainbow:

Schermafbeelding 2018-10-14 om 19.11.46

Simon had already been busy with colors for a few days, revisiting his Magformers collection to build this gorgeous color wheel:

We later repeated the MEL Science demos for Simon and Neva precocious friend: