# Mind Mystery

Our visit to Mind Mystery, a place featuring a few famous optical illusions and math puzzles museum in the Dutch province of Limburg was really impressive.

# Surrounded by the equations that changed the world

At the main entrance to CERN there is an impressive smooth curve of a memorial to the world’s most important equations and scientific discoveries:

# On top of The Shard, the tallest building in the EU

A real victory for Simon, who has had a bit of a fear of heights for years. But what he found most impressive were the noticeable changes in gravity while going up and down with the elevator. When descending from the 72nd floor he could feel the decreased G!

# The Brachistochrone

Simon believes that he has found a mistake in one of the installations at the Technopolis science museum. Or at least that the background description of the exhibit lacks a crucial piece of info. The exhibit that allows to simultaneously roll three equal-weight balls down three differently shaped tracks, with the start and the end at identical height in all the three tracks, supposes that the ball in the steepest track reaches the end the quickest. The explanation on the exhibit says that it is because that ball accelerates the most. Simon has noticed, however, that the middle track highly resembles a cycloid and says a cycloid is known to be the fastest descent, also called the Brachistochrone Curve in mathematics and physics.

In Simon’s own words:

You need the track to be steep, because then it will accelerate more – that’s right. But it also has to be quite a short track, otherwise it takes long to get from A to B – which is not in the explanation. It’s not the steepest track, it’s the balance between the shortest track and the steepest track.

Galileo Galilei thought that it is the arc of a circle. But then, Johan Bernoulli took over, and proved that the cycloid is the fastest.

The (only) most elegant proof I’ve seen so far is in this 3Blue1Brown video: https://www.youtube.com/watch?v=Cld0p3a43fU

There’s also a VSauce1 video, where they made a mechanical version of this (like Technopolis): https://www.youtube.com/watch?v=skvnj67YGmw

We’ve also made some slow motion footage of us using the exhibit (you can see that the cycloid is slightly faster, but as far as I can tell, it’s not precision-made, so it wasn’t the fastest track every time): https://www.youtube.com/watch?v=5Brub0FnpmQ

I hope that you could mention the brachistochrone/ cycloid in your exhibit explanation. I don’t think you can include the proof, because for such a general audience, it can’t fit on a single postcard!

# Red Star Line Museum

An amazing visit to the Red Star Line Museum this weekend! It’s a museum telling the moving story of the exodus from Europe at the turn of the 20th century. Red Star Line was a private passenger liner company that brought over 2 million Europeans to America. Simon enjoyed following the story of a 9 year old girl Basia Cohen who fled the violence and hunger in Ukraine in 1919 (well, maybe it was not the story that actually triggered his interest but the exciting quest involving looking for a suitcase in every hall of the museum and completing the tasks hidden inside the suitcase).

# Salle Pi

Simon talking about his favourite infinite sum at the circular room known as the “pi room” at the Palais de la DÃ©couverte (“Discovery Palace”) in Paris. Inscribed on the walls are 707 digits of the number Ï€. The ratio of coprime pairs of numbers to pairs of numbers is 6/Ï€^2. And 1/1^2 + 1/2^2 + 1/3^2 +â€¦ = Ï€^2/6 So that means that the ratio of coprime pairs of numbers to pairs of numbers equals to 1 over Simon’s favourite infinite sum!

Simon made two more short videos at the pi room:
Proof that Ï€ is irrational: https://youtu.be/CUHgsCLxL0k
Looking for 2019 among the digits of Ï€: https://youtu.be/5qIaA7MwzHY

Daniel Shiffman later showed Simon how to look for any number in the digits of Pi using this amazing project by Ben Fry: http://pi.fathom.info/

# Science Day in Belgium

Yesterday we attended one of the hundreds of Science Days venues open for free all over Belgium. Simon particularly enjoyed chemistry demos, even though he was disappointed that some companies showing their inventions didn’t want to share the actual formulas behind the tricks.

The simple non-newtonian fluid remains a favourite.

Simon dazzled by how insulator foam (polyurethane) is produced as the result of a reaction between two highly viscous substances, an isocyanate and a polyol (polyether). Another fascinating thing about this demo was that the tool mixing the two ingredients actually employed magnets!

A workshop explaining why ships don’t sink and if they do, why:

Exploring 3D printing:

Programmable spheres:

Heat indicator (material changing color depending on water temperature):

The good old baking soda and vinegar demo revisited:

# The Leaning Tower of Lire

Also known as the Book-Stacking Problem. Simon had tried to build this tower at the Fries Museum where we visited a huge Escher exhibition (to the annoyance of the museum staff, to whom I had to explain that it was a serious math experiment and not just a kid dropping bricks), but it only worked with 4 blocks (possibly because the blocks were made of foam and weren’t rigid enough). He tried to stack the blocks on top of one another, shifting every next block first by one eighth, then by one sixth, next by one fourth, and next by one half – in the end, the top block would no longer be positioned above the bottom block.

He repeated the experiment at home, first doing some calculations and then using more rigid wooden blocks and managed to stack a tower of 6 blocks! (The top block still overlapped the bottom one by a bit though) :

# The rest of the trip to London

Simon loved the Science Museum, even though he did not get to see the Klein Bottles from the museum’s permanent collection (none of them was on display). He particularly enjoyed the math and information age spaces. The Original Tour was a success, too – giggling at all the jokes on the English audio guide, he was bubbling with joy that he could follow everything and was actively studying the map, together with Dad. The only thing Simon really hated to tears was The Tower.