Exercise, Experiments, Notes on everyday life, Physics, Simon teaching, Together with sis, Trips

A lot of fluid dynamics at Technopolis

Today we celebrated my 40th birthday with a family trip to Technopolis, a mekka for science-minded kids in the Belgian town of Mechelen. (Technically, my real birthday is in two days from now, but I have messed with the arrow of time a little, to speed things up).
The entrance to the museum is adorned with a red lever that anyone can use to lift up a car!
Simon and Neva lifting up the car
The beautiful marble run and math and physics demo in one
Galton’s board and Gaussian distribution
Simon explaining the general relativity demo, which is part of the marble run
This was probably the winner among all the exhibits: a wall to climb with a mission (Simon figured it out rather quickly – one had to turn “mirrors” to change the direction of light (green projection) and have the light rays extinguish the targets.
Simon tried to explain this to other children, but they only seemed to want to climb. It was sad to see how no one cared to listen (well, except for Neva of course).
Simon was already familiar with this optical illusion. Later he saw another version of this on an Antwerp facade.
The logic gates were too easy.
the center of gravity
Huge catenaroids! Something Simon had already demonstrated to us at home, but now in XXL!
cof
And huge vortices! Another passion.
Hydrodynamic levitation! Hydrodynamic levitation!
Look! A standing wave!
And another standing wave!

Here Simon explains one more effect he has played with at home, the Magnus effect.

Coding, Community Projects, Computer Science, Contributing, JavaScript, Murderous Maths, Physics, Simon's Own Code, Simon's sketch book

Simon’s Community Contribution: Variation of 2D Casting Coding Challenge in p5.js

This is Simon’s version of Daniel Shiffman’s 2D Casting code, made on Wednesday last week right after the live session. Link to the live session including the coding challenge.

Code and interactive animation are online at: https://editor.p5js.org/simontiger/sketches/ugHX4yKQC
Play with the animation online at:
https://editor.p5js.org/simontiger/present/ugHX4yKQC
https://editor.p5js.org/simontiger/full/ugHX4yKQC

Simon’s suggestions during a patron-only live session yesterday
a screenshot of Simon’s community contribution published on the Coding Train website

Simon has also made one more, optimized version of this project (with fewer rays, runs faster): https://editor.p5js.org/simontiger/present/F6TCHAZs_
https://editor.p5js.org/simontiger/sketches/F6TCHAZs_

Both of Simon’s versions have been added to the community contributions on the Coding Train website: https://thecodingtrain.com/CodingChallenges/145-2d-ray-casting.html

screenshot of the optimized version
chemistry, Experiments, Physics, Simon teaching, Simon's sketch book, Together with sis

Chemistry Experiments: Polarized light iridizes crystals

Today we have made beautiful rainbow chrystals! Polarized light iridizes sodium thiosulfate crystals, so we made the crystals in between two polarizing films and then observed them through the microscope. In the video, Simon also explains how polarizing film works.

From the scientific description at the MEL Science website: Sodium thiosulfate crystals contain five molecules of water per one unit of sodium thiosulfate Na2S2O3. Interestingly, when heated, the crystals release the water, while sodium thiosulfate dissolves in this water. This solution solidifies rapidly when cooling, forming beautiful crystals. If these crystals are put between polarizing films, they take on an iridescent sheen. This is because the polarizing films only let light with certain characteristics through, and this light in turn “iridizes” the otherwise-colorless sodium thiosulfate crystals.

Astronomy, Milestones, Notes on everyday life, Physics

Black Hole Breakthrough

Simon recorded this video right after the news was announced on April 10

Caught Simon’s reaction to Wednesday’s breaking news on video: the first-ever image of a black hole published, made by the Event Horizon Telescope project team. Simon explains why, if you stood next to the black hole, you would be able to see the back of your own head.

Simon loved this video by Veritasium about how the image of the black hole was made (he had watched this one day prior to the actual publication of the black hole image).

Yesterday, wee also watched this beautiful TEDx contribution by Katie Bouman (one of the leading figures behind the algorithm that helped stitch the M87 black hole image data together). The video is from three years ago, when the project was just getting started. Katie is such an inspiration: a computer scientist helping astrophysicists!

Scientists report ‘groundbreaking’ black hole findings from the Event Horizon Telescope: link to the actual press conference.

Electricity, Experiments, Physics

Physics Experiments: Using an LED backwards

We have tried using an LED backwards: not get it to shine by letting an electric current pass through it but produce electricity by shining light on an LED (this is how solar panels work). It’s important to use a sensitive LED for this experiment, and as we have observed, it also seems to be important to use light photons of the same frequency as the colour of the LED (red laser didn’t work on a white LED, but it may have to do with the fact that red light is weaker than white light anyway, i.e. has a lower frequency). The picture below shows us measuring the voltage of the current produced by the LED.

shining a light at the diode produces voltage
the same experiment setting but with the light source turned off produces no voltage
red light not strong (energetic) enough to produce voltage, also when shined on a red LED

We’ve have learned this and a a lot more from Steve Mould’s video on How diodes, LEDs and solar panels work: Photovoltaic cells and LEDs are both made of diodes. Diodes are designed to allow electricity to flow in one direction only but the way we make them (out of semiconductors) means that can absorb and emit light.

In the video, Steve shows how the semiconductor atoms share elctrons. Semiconductors are crystal structures of atoms are replaced by the atoms of neighboring elements, for example a structure where some silicon (Si) atoms are replaced by phosphorus (P) or boron (B) atoms, thus providing for free electrons inside the structure (N-type conductor) or for free “holes” unoccupied by electrons (P-type conductor). A diode is basically two semiconductors pushed together. With enough voltage, the electrones are able to jump from the N-type semiconductor across the depletion zone and into the P-type semiconductor, emitting light (photons) as they fill the holes and go from a high energy state into the low energy state.

If you shine a light at a diode, you can kick some electrons from their shells and thus create free electrons and holes that will move (because of the electric field in the depletion zone) and generate voltage.


Experiments, Physics

Physics Experiments: Stroboscopic Effect

Simon showed us this amazing hing with a fidget spinner. It’s called stroboscopic effect. It’s a visual phenomenon that occurs when continuous motion is represented by a series of short or instantaneous samples (like camera shots), distinct from a continuous view.

In the video below, Simon also demonstrates the rolling shutter effect with the same fidget spinner and camera.

Experiments, Physics, Together with sis

Physics Experiments: Double Slit

We have wanted to do the Double-Slit experiment for a long time. Finally, last Friday, armed with a suitable box, we ventured outside. To our common disappointment, light just wouldn’t behave as a wave this time, even though we had no detectors to check which slit the photons actually passed through. What we observed inside the box looked like two perfect stripes. No interference.

No interference: light behaving like particles

Simon looking inside the double-slit experiment box to check for the interference
Simon’s sister Neva dragging the box down the stairs

Experiment failure aside, we were in for a pleasant surprise, too: the box suddenly turned into a huge camera obscura! This is a picture of me and the blue sky as seen from inside the box!

An image of me, the buildings and the sky above as it appears inside the camera obscura

When we got home, and tried to look inside the box again in the dimmer light in the living room, we were finally rewarded with this beautiful interference pattern:

The interference pattern that the light coming inside the box through the double slit creates (proving that light is also a wave)

We can only guess why it didn’t work outside. The wrong angle of the light beams (the sun being high in the sky above our heads)? Or maybe the light wat too bright, too many photons got in? The slits being too wide? We’ll be repeating this experiment for sure.

Experiments, Geometry Joys, Physics, Together with sis

Physics Experiments: Making Holes in Soap Membrane

This demo is inspired by a recent video on Steve Mould’s channel. It’s about creating a movable hole in soap film with a loop of cotton thread (the photo shows Simon sticking a pencil through such a hole). Once in the soap membrane, the cotton thread forms a perfect circle. It’s because the soap film tries to minimise its area and compress as much as it can. The only way that can happen is to maximise the area of the hole. And as we know, with a fixed perimeter, the biggest area that you can make with it is if you form that perimeter into a circle, Simon explains as I’m writing this.