How a Drawing Could Cure Cancer: Physics Diagrams as Modern Hieroglyphs

Written by: Umberto Cannella

If you’re a fan of the TV series, The Big Bang Theory you’re probably used to laughing at Penny and Sheldon’s interactions, especially when Dr. Cooper tries to explain physics to his loveable blonde neighbor.

One such instance is captured in the picture below.  If you look at it, you could easily imagine Sheldon saying something like: “See, Penny, this equation accounts for the branching ratio of a top quark decaying into a W boson and bottom quark, as depicted by the upper-left diagram.”

Do you think Sheldon took up drawing simply so he could flirt with Penny?

Not at all — the pictograms on the whiteboard are a serious part of physics! They are known as Feynman diagrams, named after their inventor Richard Feynman, who first proposed their adoption in 1948 and later won the Nobel Prize for his work, including this invention, which provides a visual representation of particle physics.

Feynman was as much of an eccentric as his fictional colleague on the TV series.  Do you remember the episode “The Werewolf Transformation”?  In that episode, Sheldon goes “nuts” and wakes up Leonard by playing bongos in the middle of the night. Well, Feynman used to play bongos, too (in fact, that could be where the show’s writers got the idea).

 But why would a scientist propose drawings to his colleagues? Were they bored? Did their minds wander?  On the contrary, in the late 1940s, physicists were kind of stuck in their path to gain a better understanding of how the natural world works at an ever deeper level.

Roughly speaking, they needed to know where to go next and how to reach their destination. That’s where the novelty of Feynman’s genius was crucial.  His diagrams provided the tools of a new language, making it easier for physicists to communicate with each other.

At a glance, Feynman diagrams bear a resemblance to Egyptian hieroglyphs.  Just as hieroglyphs represented a wealth of information in a single sign, a Feynman diagram encapsulates the description of an interaction among particles in a very clear and concise fashion, making it possible to streamline the computation of the measurable effect that a certain physical process has. Knowing what to compute and how to do it were badly needed pieces of information at the time Feynman introduced his idea. The non-trivial advantage of adopting a common vocabulary lies in the universal standard of naming that this vocabulary provides; those who speak the same language are able to understand each other and then communicate among themselves, sharing meaningful information.

As time went by, something very interesting happened with Feynman diagrams and their adopters.  As physicists discussed and studied possible interactions, they began to name configurations and diagrams of particles, just like what we do when we search for images of animals in the clouds. There are indeed particle interaction processes whose Feynman diagram resembles a bell, a sunrise, a tadpole, a seagull, or even a penguin! All this theoretical fun led physicists to the recent discovery of the Higgs boson, a.k.a., the God particle. This endeavor was also made possible by the Large Hadron Collider, a machine whose name is inextricably linked to hadron-therapy, a branch of medicine that can accurately cure tumors lying deep in the human body.

More than sixty years after their invention, Feynman diagrams are still largely employed in particle physics.  They allow new insight and better precision in calculating both the astrophysical signal to be expected when black holes collide and the modeling of molecular dynamics. So, the next time you see Penny trying to interpret some enigmatic hieroglyph on Sheldon’s whiteboard, think about these deep connections … after you have laughed, of course.You can find more information about Feynman diagrams here or here.

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