The Large Hadron Collider (LHC) is the world's largest and most powerful particle accelerator. Within its 17-mile loop, beams of particles are slammed into each other at speeds just 3 meters per second shy of the speed of light. By observing these collisions, physicists may be able to explore some of the most nagging questions in the universe, like, "What is the nature of dark matter?" and, "Are there additional dimensions?"
As a machine constructed on the forefront of possibility, the LHC has also raised questions of its own, like, "Will it spawn micro black holes that could swallow the Earth?" or, "Will it create strange matter particles that could overtake the planet?" or, "Will it open a gateway to Hell?" Obviously, the safety concerns at the LHC are a tad more cataclysmic than you'll find at a run-of-the-mill manufacturing plant or science lab. Thankfully, these doomsday scenarios are also unfounded, fomented in the first place by misunderstanding and fear of the unknown, not any sort of fact.
The LHC isn't completely harmless, mind you. All particle accelerators release DNA-damaging radiation during their operation, and those who work in close proximity run the risk of exposure. CERN maintains rigorous procedures to minimize the danger to its employees.
But let's say, completely hypothetically, that all of CERN's stringent safety mechanisms failed (which is highly unlikely to the point of impossibility), and someone managed to climb inside the LHC as it was turned on, and was subsequently struck by the particle beam? What would happen?
"I certainly wouldn't advise doing that," CERN scientist David Barney told the University of Nottingham's Sixty Symbols. "The beam itself is focused down very tightly to less than a millimeter across, extremely intense. The actual energy carried by the beam is like an aircraft carrier in motion."
Another scientist at CERN, Steven Goldfarb, was more blunt and to the point. "It would burn right through you."
Barney explained that a much wider halo of radioactive subatomic particles, mostly electrons and muons, accompanies the "extremely" intense proton beam.
"Your whole body would be irradiated. You'd die pretty quickly."
Barney and Goldfarb's learned estimations are likely the closest we'll ever get to knowing what would happen if a person directly encountered the LHC's particle beam. Quite understandably, nobody with access to CERN and their sanity intact is especially keen on finding out firsthand. But, incredibly, real-world, experimental evidence exists!
Back in 1978, Russian physicist Anatoli Bugorski was struck in the head with a particle accelerator's beam. Moscow journalist Masha Gessen chronicled the event for Wired Magazine in 1997.
Bugorski was working with the U-70 synchrotron at the time (for reference, the U-70 had a comparatively measly 1% of the LHC's maximum power) and stuck his head into the accelerator tube, obviously thinking that the machine was off. It wasn't. He saw "a flash brighter than a thousand suns," but felt no pain. Bugorski was taken to a hospital where he was expected to die of radiation poisoning over the ensuing two to three weeks. Gessen describes what happened next:
Over the next few days, skin on the back of his head and on his face just next to his left nostril peeled away to reveal the path the beam had burned through the skin, the skull, and the brain tissue. The inside of his head continued to burn away: all the nerves on the left were gone in two years, paralyzing that side of his face. Still, not only did Bugorski not die, but he remained a normally functioning human being, capable even of continuing in science. For the first dozen years, the only real evidence that something had gone neurologically awry were occasional petit mal seizures; over the last few years Bugorski has also had six grand mals. The dividing line of his life goes down the middle of his face: the right side has aged, while the left froze 19 years ago.
If there's a lesson to be learned, it's that charged beams of particles should be smashed into other particles, not people.