Experiments, Geography, Milestones, Physics, Together with sis, Trips

CERN Open Days September 14 – 15, 2019

The most important experience was actually simply to see how huge the Large Hadron Collider is. We totally didn’t expect the site of every experiment on the 27km ring to resemble an industrial town in its own right, scattered miles across a desert-like terrain with the Mont Blanc and the Jura mountains as the scenic back drop. It was a challenge to walk between the activities we had carefully planned in advance only to find out that some of the were full or required an hour of waiting in line. But the kids have withstood these challenges heroically and were rewarded with a few unforgettable impressions.

In front of the CMS experiment
A schematic of the LHC
It all begins with simple hydrogen protons…
the waiting
Magnet levitation above superconductive material used at CERN to create strong magnetic field to bend the path of the particles
Cloud chamber: we have actually seen energetic charged particles leave traces in the alcohol vapor in real time, in the form of a trail of ionized gas! What we saw were mainly alpha particles and electrons, we were told, judging by the character of the trail they left. Cloud chamber detectors used to play an important role in experimental physics, this is how the positron was discovered! Simon was a bit sad he didn’t get to actually build a cloud chamber as part of a workshop (they didn’t allow anyone younger than 12 to do the workshop), but he was lucky to get a personal tour at another site, where a couple of cloud chambers were available for exploration.
Our wonderful guide computer scientist George Salukvadze showing us around at DUNE, the Deep Underground Neutrino Experiment. George told us the detectors they are building will be employed at Fermilab in the U.S. Among other things, George has done the programming for the live website (screen with liquid Argon).
Playing the particle identity game
Geography, history, Milestones, Murderous Maths, Museum Time, Notes on everyday life, Physics, Together with sis, Trips

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:

Simon pointing to the Fourier transform function
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).