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.

Horizontal force

Going for a walk quickly turns into yet another Physics experiment. “Here’s a challenge: what if you can force the ball down so much and induce so much horizontal motion (when the ball bounces off of a wooden wedge) into the system that it goes all the way to the other side?” Simon shouts as he runs after a small bouncy ball in a large space that once used to be a tram depot. “With a back spin the ball goes horizontally! “

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.

Serious answers

Simon told me this morning that he has found the answer to a question that bothered him so much lately -why photons (and gluons) violate E = mc². “It’s because photons are not real particles, they are virtual! That means that you cannot directly detect them. You need a photon to bounce off of an object to detect it. And gluons you cannot detect at all!”

Photons also don’t satisfy Eistein’s more complicated and less well-known equation about energy momentum relation: E² = (c²) + p²c², he added enthusiastically.

No Limit

Mom, did you know there’s a density limit? Density is mass divided by size! If an object reaches the density limit it will become a black hole. If you have an object that is not homogeneous it can be more than the density limit in some places and less than the density limit in other places, and then in some places it’ll be a black hole and in others not. And so the object will swallow up itself!

(exactly what we are talking about when the picture was taken)

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!


Impressions on Newton’s mechanics.

“Are you impressed?” – Simon asks, laughingly, and I can see it must be a pun. We are in bed, reading up on Newton’s laws of motion that talk of forces being “impressed” upon bodies.

Simon continues: “Newton’s mechanics says that the speed limit is infinite, which says that matter doesn’t exist, which says that Physics doesn’t exist, which says that Newton’s mechanics doesn’t exist. Newton’s mechanics contradicts itself!”

The book we are reading (17 Equations that Changed the World by Ian Stewart) goes on to describe how in Newton’s laws, calculus peeps out from behind the curtains and how the second law of motion specifies the relation between a body’s position, and the forces that act on it, in the form of a differential equation: second derivative of position = force/mass. To find the position, the book says, we have to solve this equation, defusing the position from its second derivative. “Do you get it?” – I ask, “Because I don’t think I do”. — “I’ll need a piece of paper for this”, – Simon quickly comes back dragging his oversized sketchbook. Then he quickly writes down the differential equation (where the x is the position) to explain to me what the second derivative is. And then he solves it: