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If you want to build a particle accelerator -- the biggest particle accelerator ever -- you're going to need a really long tunnel. One that's about 100 kilometers (around 64 miles) in length, in fact.

And Elon Musk, CEO of SpaceX and Tesla, who's never one to shy away from an opportunity, is in the tunnel-digging game, leading the charge at The Boring Company.

In response to a tweet from MIT Technology Review on Monday detailing the Future Circular Collider, a new particle accelerator project conceived by the team that operates the Large Hadron Collider, Musk hinted that he'd already spoken to CERN's Director-General Fabiola Gianotti.

Director of CERN asked me about Boring Co building the new LHC tunnel when we were at the @royalsociety. Would probably save several billon Euros. — Elon Musk (@elonmusk) January 21, 2019

At the moment, CERN's Large Hadron Collider is shut down for two years to receive upgrades, but researchers are looking further ahead at new conceptual designs, including the FCC. That collider, which would be four times bigger than the LHC, is estimated to cost around $5.7 billion just for the tunnel. If Musk could save several billion euros, that sure would leave some weight in the wallet.

Arnaud Marsollier, head of media relations at CERN, confirmed that Musk and Gianotti "had recently the opportunity to informally meet at the Royal Society," stating that they "briefly discussed ... upcoming projects and that Elon Musk introduced the Boring Company" to Gianotti.

With that, CERN didn't exactly shoot down the idea of a Musk-built particle accelerator tunnel, with the organization's press account tweeting on Monday that the organization is "open to new, cost-effective technologies that could lead to their implementation, including the tunnels that will be needed."

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Musk revealed Boring Company's first test tunnel, underneath the earth at SpaceX's Hawthorne headquarters in California, back on Dec. 18. That one is a proof-of-concept, but a finished tunnel would be able to zip cars through at about 150 miles per hour (around 240km/h) using special "skates" that help track the car through the tunnel. That inspired some to question whether Musk might be able to help them.

Earlier in January, Musk was asked by Jeremy Buckingham, an independent politician from Sydney, Australia, how expensive it would be to build a 50-kilometer tunnel under Sydney's Blue Mountain region to get to the west of the city. Musk suggested he'd be able to excavate that section of earth for around $750 million, at $15 million per kilometer.

About $15M/km for a two way high speed transit, so probably around $750M plus maybe $50M/station — Elon Musk (@elonmusk) January 16, 2019

One engineer called that estimate "Alice In Wonderland" talk, according to the Australian Broadcasting Corporation, while the state transport minister said Musk's proposal "isn't a reality at this time."

A representative of the Boring Company did not expand on any of Musk's potential tunnel plans.

While Musk has been quick to propose cheap tunnels, the last month has seen many employees at his three companies laid off. SpaceX announced 10 percent of its workforce would be cut, Tesla will lay off 7 percent, and the Boring Company fired five employees in the past week, reports Recode.

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