April 21, 2021

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Here’s what happens when a beam of subatomic particles hits you in the face

6 min read

What would happen if you stuck your body inside a particle accelerator? The scenario seems like the start of a bad Marvel comic, but it happens to shed light on our intuitions about radiation, the vulnerability of the human body, and the very nature of matter.

Particle accelerators allow physicists to study subatomic particles by speeding them up in powerful magnetic fields and then tracing the interactions that result from collisions. By delving into the mysteries of the Universe, colliders have entered the Zeitgeist and tapped the wonders and fears of our age.

As far back as 2008, the Large Hadron Collider (LHC), operated by the European Organization for Nuclear Research (CERN), was charged with creating microscopic black holes that would allow physicists to detect extra dimensions. To many, this sounds like the plot of a disastrous science-fiction movie.

It came as no surprise when two people filed a lawsuit to stop the LHC from operating, lest it produce a black hole powerful enough to destroy the world. But physicists argued that the idea was absurd and the lawsuit was rejected.

Then, in 2012, the LHC detected the long-sought Higgs boson, a particle needed to explain how particles acquire mass. With that major accomplishment, the LHC entered popular culture; it was featured on the album cover of Super Collider (2013) by the heavy metal band Megadeth, and was a plot point in the US television series The Flash (2014-).

Yet, despite its accomplishments and glamour, the world of particle physics is so abstract that few understand its implications, meaning, or use. Unlike a NASA probe sent to Mars, CERN’s research doesn’t produce stunning, tangible images.

Instead, the study of particle physics is best described by chalkboard equations and squiggly lines called Feynman diagrams. Aage Bohr, the Nobel laureate whose father Niels invented the Bohr model of the atom, and his colleague Ole Ulfbeck have even gone as far as to deny the physical existence of subatomic particles as anything more than mathematical models.

Which returns us to our original question: what happens when a beam of subatomic particles traveling at nearly the speed of light meets the flesh of the human body? Perhaps because the realms of particle physics and biology are conceptually so far removed, it’s not only laypeople who lack the intuition to answer this question, but also some professional physicists.

In a 2010 YouTube interview with members of the physics and astronomy faculty at the University of Nottingham, several academic experts admitted that they had little idea what would happen if one were to stick a hand inside the proton beam at the LHC. Professor Michael Merrifield put it succinctly: ‘That’s a good question. I don’t know is the answer. Probably be very bad for you.’

Professor Laurence Eaves was also cautious about drawing conclusions. ‘[B]y the scales of energy we notice, it wouldn’t be that noticeable,’ he said, likely with a bit of British understatement. ‘Would I put my hand in the beam? I’m not sure about that.’

Such thought experiments can be useful tools for exploring situations that can’t be studied in the laboratory. Occasionally, however, unfortunate accidents yield case studies: opportunities for researchers to study scenarios that can’t be experimentally induced for ethical reasons. Case studies have a sample size of one and no control group.

But, as the neuroscientist V S Ramachandran has pointed out in Phantoms in the Brain (1998), it takes only one talking pig to prove that pigs can talk. On 13 September 1848, for example, an iron rod pierced through the head of the US railway worker Phineas Gage and profoundly changed his personality, offering early evidence of a biological basis for personality.

And on 13 July 1978, a Soviet scientist named Anatoli Bugorski stuck his head in a particle accelerator. On that fateful day, Bugorski was checking malfunctioning equipment on the U-70 synchrotron – the largest particle accelerator in the Soviet Union – when a safety mechanism failed and a beam of protons traveling at nearly the speed of light passed straight through his head, Phineas Gage-style.