How drawing a penguin can help cure cancer: physics diagrams as modern hieroglyphs and their applications

If you are a fan of The Big Bang Theory tv series you are used to laugh at Penny and Sheldon’s interactions, especially those when Doctor Cooper tries to explain physics to his blond friend.

 Sheldon and Penny during a discussion about particle physics; drawn on the blackboard, besides formulae, are pictograms known as Feynman diagrams, after their inventor Richard Feynman, physicist and Nobel Prize winner in 1965.

Sheldon and Penny during a discussion about particle physics; drawn on the blackboard, besides formulae, are pictograms known as Feynman diagrams, after their inventor Richard Feynman, physicist and Nobel Prize winner in 1965.

One such instance is captured in the picture above. If you look at it you can easily figure Sheldon say something like: “see, Penny: this equation accounts for the branching ratio of a top quark decaying into a W boson and a bottom quark, as depicted by the upper-left diagram”. Do you think Sheldon got into drawing to put himself in Penny’s shoes? Not at all: the pictograms on the blackboard are some serious piece of physics! They are known under the name of Feynman diagrams, after their inventor Richard Feynman, who first proposed their adoption in 1948 and later won the Nobel Prize thanks to, among other things, this visual handle on particle physics.

You don't get a postal stamp after you unless you've done something notable.

You don’t get a postal stamp after you unless you’ve done something notable.

Feynman was as much of an eccentric as his fictional colleague of The Big Bang Theory tv series: do you remember the episode “The Werewolf Transformation”, when 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’s probably where the authors of the series have taken inspiration from). However, quite differently from Doctor Cooper, Professor Feynman could drive a vehicle: this allowed him to have his van decorated with his own diagrams … how bloody cool!

Professor Feynman poses with his family in front of his van, which he decorated with instances of his very own visual handle on particle physics.

Professor Feynman poses with his family in front of his van, which he decorated with instances of his very own visual handle on particle physics.

But why would a scientist propose drawings to his colleagues? did they all get bored with their minds wandering? On the contrary: in the late 1940’s 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 proved to be crucial: his diagrams provided the tools of a new language to formulate a new discourse.

Owing to their graphical character, Feynman diagrams bear resemblance to Egyptian hieroglyphs: just like that ancient pictogram system encoded a wealth of information in a single sign, a Feynman diagram encapsulates the description of an interaction among particles in a very clear and economic fashion; by means of this virtue, it is possible to streamline the computation of the measurable effect that a certain physical process has. Knowing what to compute and how were very much needed features at the time Feynman introduced his idea: the non-trivial advantage of adopting a common vocabulary lies in the univocal and universal standard of the naming this vocabulary provides; those who speak the same language are able to understand each other and, then, to communicate among themselves, sharing meaningful information.

Egypt Hieroglyphe4.jpg
Example of an Egyptian Hieroglyphe ” (licensed under CC BY-SA 3.0 via Wikimedia Commons).

As time passed, something very down-to-earth happened with Feynman diagrams and their adopters: when pondering about physical interactions, physicists began dubbing the configurations that particles assumed once arranged in a diagram, just like what we all 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!

The Feynman diagram resembling a penguin.

The Feynman diagram resembling a penguin.

All this theoretical fun has brought physicists down the path recently crowned by the discovery of the Higgs boson, a.k.a. the God particle. Besides invaluable ideas, 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.

A picture worth a thousand words. Radio-therapy employs X-ray photons, that is to say the same particles that make up visible light but with endowed higher energy. In their path to the tumor, X-rays deposit a non-negligible fraction of their radiation dose to healthy tissues. On the contrary, we can see from the picture that protons, the positively-charged constituents of atomic nuclei, are much more effective in reaching the deep-lying tumor, without damaging other body parts.

A picture worth a thousand words. Radio-therapy employs X-ray photons, that is to say the same particles that make up visible light but with endowed higher energy. In their path to the tumor, X-rays deposit a non-negligible fraction of their radiation dose to healthy tissues. On the contrary, we can see from the picture that protons, the positively-charged constituents of atomic nuclei, are much more effective in reaching the deep-lying tumor, without damaging other body parts.

More than sixty years after their proposal, Feynman diagrams are still largely employed in particle physics but not only: for example they are allowing new insight and better precision in calculating both the astrophysical signal to be expected when black holes collide and the modeling of molecular dynamics. Next time you see Penny trying to interpret some murky hieroglyph on Sheldon’s blackboard, think about these deep connections … after you have laughed, of course.

FURTHER READING

If you would like to know more about how the machinery of Feynman diagrams works you can take a look at the following references:
let’s draw Feynman diagams;
Physics and Feynman Diagrams.

For more fun, less mainstream uses of Feynman diagrams see:
– the ParticleZoo Feynman Diagram magnet set;
– the PhDComics’ Feynman Diagrams on Academic Interactions;
– the result of a Google search
art inspired by Feynman diagrams;
and much more …

A very passionate follower of Feynman diagrams chose to have one tattoed on his arm.

A very passionate follower of Feynman diagrams chose to have one tattoed on his arm.

One thought on “How drawing a penguin can help cure cancer: physics diagrams as modern hieroglyphs and their applications

  1. Pingback: Up to speed with TBBT | Doctor Cinnamon

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