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By Dan Falk

Seven years after experiments at the Large Hadron Collider (LHC) — the world’s largest atom smasher — confirmed the existence of a mysterious subatomic particle known as the Higgs boson, physicists have drawn up plans to build an even bigger collider.

The Future Circular Collider (FCC) would be four times bigger and up to 10 times more powerful than the LHC, the European Organization for Nuclear Research (better known by its French acronym, CERN) announced in a report on Tuesday. An international consortium of 23 member nations, CERN operates the Large Hadron Collider and would run the FCC as well.

“The FCC conceptual design report is a remarkable accomplishment,” CERN Director-General Fabiola Gianotti said in a statement. “It shows the tremendous potential of the FCC to improve our knowledge of fundamental physics and to advance many technologies with a broad impact on society.”

The new collider, to be built near the LHC along the Swiss-French border, would significantly expand scientists’ understanding of matter and the universe, according to CERN. If the project goes as planned, scientists could be using the new collider to hunt for new subatomic particles by midcentury.

A tunnel interior of a particle collider.CERN

The plan for the new collider, developed by more than 1,000 scientists from 150 institutions around the world, calls for a multinational collaboration to build a $24-billion facility consisting of several labs and a circular tunnel with a circumference of 100 kilometers (62 miles).

The plan will now be reviewed by an international panel of scientists before CERN’s governing council decides whether to move forward with it.

Small particles, big machines

Though the particles that make up the universe are small, the machines needed to study them must be large. Only huge colliders can create the enormous energy needed to probe matter at the tiniest scales. The colliders accelerate protons, electrons, and other particles to speeds close to the speed of light, and smash them into one another in the hope of discovering unknown particles among the debris.

Following the discovery of the Higgs boson in 2012, physicists working at the LHC had hoped subsequent experiments there might offer hints of a “new physics” — that is, reveal previously unknown particles that aren’t part of the so-called Standard Model of physics that represents our current understanding of the matter that makes up everything in the universe.

That hasn’t happened. But scientists are hopeful that a bigger accelerator like the Future Circular Collider might succeed where the LHC did not.

Artistic impression of a collision event at the center of a future detector.CERN

“For a century, particle accelerators of ever-increasing energy have pushed forward the frontiers of our understanding of the universe and the fundamental building blocks of everything in it,” Glenn Starkman, a physicist at Case Western Reserve University in Cleveland, told NBC News MACH in an email. “We stand at a moment where our vision of what lies beyond the current frontiers is unfamiliarly hazy; parting that haze requires bold vision and determination.”

Worth the cost?

Other scientists are dubious about the need for a huge new collider.

“Given all we currently know, it would not be a good investment,” Sabine Hossenfelder, a theoretical physicist at the Frankfurt Institute for Advanced Studies in Germany, said in an email. “Of course, it could be that it finds something new, if we are lucky,” she said. But given the uncertainty, she said scientists might get more bang for their buck by investing instead in bigger telescopes, nuclear fusion technology or artificial intelligence research.

David King, a physicist and the U.K.’s former chief scientific adviser, expressed similar doubts. “We have to draw a line somewhere. Otherwise we end up with a collider that is so large that it goes around the equator,” he told the BBC. “And if it doesn’t end there, perhaps there will be a request for one that goes to the moon and back.”

But those who favor pushing ahead with big projects such as the proposed collider point out that fundamental science often brings practical benefits as well as scientific discoveries.

The construction and operation of the LHC have been credited with key advances in radio technology, robotics, computer science, cryogenics and many other fields. And the World Wide Web — the computer network that makes it possible for you to read this article — was invented by an English scientist named Tim Berners-Lee while working at CERN in the late 1980s.

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