Exercise, Geography, Notes on everyday life, Physics, Together with sis, Trips

Some more London

Taking the Thames Clipper
At London’s olympic pool: Simon and Neva took part in the Ultimate Aquasplash, an inflatable obstacle course for competent swimmers that involved sliding down a 3-meter high slide into deep water – another personal victory
At the Queen Elizabeth Olympic Park
Generating power on a bicycle (you could see how many watt you generate)
At a 3D film for the first time
Back to the Science Museum
Astronomy, Experiments, Geography, history, Milestones, Notes on everyday life, Physics, Space, Together with sis, Trips

We’ve found the real 0° meridian!

And it turned out to be a that little path next to the Royal Observatory in Greenwich, not the Prime Meridian line. The 0° meridian is what the GPS uses for global navigation, the discrepancy results from the fact that the Prime Meridian was originally measured without taking it into consideration that the Earth isn’t a perfect smooth ball (if the measurements are made inside the UK, as it it was originally done, this does’t lead to as much discrepancy as when vaster areas are included).

Simon standing with one foot in the Western hemisphere and the other one in the Eastern hemisphere
The GPS determines the longitude of the Prime Meridian as 0.0015° W
Simon tried to use JS to program his exact coordinates, but that took a bit too long so we switched to the standard Google Maps instead
The Prime Meridian from inside the Royal Observatory building
Looking for the real 0° meridian: this is an open field next to the Royal Observatory. At this point, the SatNav reads 0.0004° W.
And we finally found the 0° meridian! Some 100 meters to the East of the Prime Meridian
The 0° meridian turned out to intersect the highest point on the path behind Simon’s back!
Simon and Neva running about in between the measurements of longitude
Astronomer Royal Edmond Halley’s scale at the Royal Observatory
Halley’s scale is inscribed by hand
Coding, Computer Science, Crafty, Geography, Murderous Maths, Notes on everyday life, Simon's sketch book

Pathfinding algorithms: Dijkstra’s and Breadth-first search

The photos below show Simon playing with Breadth-first search and Dijkstra’s algorithms to find the most efficient path from S to E on a set of graphs. The two more complex graphs are weighed and undirected. To make it more fun, I suggest we pretend we travel from, say, Stockholm to Eindhoven and name all the intermediate stops as well, depending on their first letters. And the weights become ticket prices. Just to make it clear, it was I who needed to add this fun bit with the pretend play, Simon was perfectly happy with the abstract graphs (although he did enjoy my company doing this and my cranking up a joke every now and then regarding taking a detour to Eindhoven via South Africa).

this was an example of how an algorithm can send you the wrong way if it has data of the “right” way being weighted more (due to traffic jams, for example)
Coding, Computer Science, Crafty, Geography, Geometry Joys, Murderous Maths, Simon's sketch book

Dijkstra’s pathfinding algorithm

“I have first built a maze, then I turned it into a graph and applied Dijkstra’s pathfinding algorithm!”

a maze to which Dijkstra’s pathfinding algorithm is applied

Simon learned this from the Computerphile channel. He later also attempted to solve the same maze using another pathfinding algorithm (A-Star).

Electronics, Geography, Logic, Milestones, Murderous Maths, Physics, Simon teaching

Newtonian GPS would place you on the wrong planet!

Simon explains why our modern satellite navigation (the Global Positioning System or GPS) is a great experimental proof for Einstein’s relativity theory and what would happen if the software calculated your car’s location using Newtonian dynamics.

Simon learned about this from Ian Stewart’s awesome book “17 Equations that Changed the World”, Chapter 13 (Relativity).

Geography, history, Murderous Maths, Museum Time, Notes on everyday life, Physics, Together with sis, Trips

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.

Experiments, Geography, Geometry Joys, Milestones, Murderous Maths, Physics, Simon teaching, Simon's sketch book, Trips

The skyscraper that set things on fire

Inspired by Matt Parker’s video  about the uniquely shaped building at 20 Fenchurch Street in London, Simon was very excited to visit this address. In the video below, made on the pavement in front of the skyscraper, Simon shows the geometric proof (he learned from Matt) of why the building’s shape used to let it set things on fire on extremely sunny days.

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