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Why are scientists digging a tunnel from Geneva to Annecy?

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Why are scientists digging a tunnel from Geneva to Annecy?
Large Hadron Collider (LHC) at Cern in Geneva. Photo by Fabrice COFFRINI / AFP)

Scientists want to build a 91km tunnel that would pass under the Lake Geneva in Switzerland and loop round to the south near the picturesque French town of Annecy at a cost of 5.5 billion francs (€5.87 billion).


After eight years of study, scientists at the European Council for Nuclear Research (CERN) want to push ahead with a 91-km tunnel that would be submerged deep under the lake’s surface.

Eight technical and scientific sites would be built on the surface.

This is where the tunnel will be built. AFP PHOTO / European Organization for Nuclear Research (CERN) 

What is the purpose of this tunnel?

CERN already has the largest particle accelerator in the world, the Large Hadron Collider (LHC), a ring 27 km in circumference located around 100 metres underground.

However, the problem with accelerators is that “at a given moment, no matter how much data we accumulate, we arrive at a wall of systematic errors,” according to Patrick Janot, physicist at CERN, who estimates that moment will come sometime between 2040-2045. 

“It will then be time to move on to something much more powerful, much brighter, to better see the contours of the physics that we are trying to study,” he added.

What exactly does the Large Hadron Collider do?

To put it simply: its goal is to explore the mysteries of physics.

Scientists use the LHC to test theoretical predictions in particle physics and generally to answer the still unresolved questions about the universe.

For instance, they are using it to learn a lot more than we know today about the structure of space and time, the Big Bang, black holes, and other secrets of the universe.


The tunnel will not be completed until the mid-century. What is happening right now?

CERN said it is consulting with the regions along the route (that is, the cross-border area between Geneva and Haute-Savoie in France) and plans to carry out impact studies on how the tunnel would affect this particular area.

The timeline right now is to start the project in 2033 by digging a tunnel 5.5 metres in diameter.

It would pass 30 metres under the bed of the Rhône river, at least 100 metres under the bottom of Lake Geneva, and up to more than 500 metres under the Borne plateau, in Haute-Savoie.

Do all scientists agree that the new tunnel is a good idea?

No. Some researchers fear that this huge project, estimated to cost about 5.5 billion francs (€5.87 billion), will swallow up funds that could be used for other, less abstract physics research — for instance, in medicine.


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