Stretching String Theory

How accurate is The Big Bang Theory’s String Theory explanation?

When thinking of the smallest unit of matter, many people’s minds immediately jump to the atom, which high school chemistry instills in your mind as the building block of everything. However, atoms consist of protons, neutrons, and electrons, so are they really the smallest units? They would be, if, in 1964, physicists Murray Gell-Man and George Zweig hadn’t discovered the existence of quarks — charged subatomic particles that make up protons and neutrons (1). So surely those have to be the smallest particles. Well, yes and no. 

Quarks and electrons are elementary particles, which are fundamental constituents of indivisible matter (2). Despite this definition, scientists continue to investigate the workings of elementary particles and produce theories about their potential compositions. One of these theories, created in 1969 by Italian physicist Gabriele Veneziano, posited that reality is made up of one-dimensional, infinitesimal vibrating strings (3). Later named String Theory, this unique idea gained popularity because of its creativity and mathematical validity. 

String theory concept seen in different stages of matter.

In the 21st century, the entertainment industry began dramatizing many scientific theories and mysteries to intrigue viewers. One of the biggest hits among science dramas was The Big Bang Theory which aired in 2007 and ran for 12 years. Among the many scientific principles covered in the series, the show tackled String Theory with theoretical physicist Sheldon Cooper working on the particle physics concept for all twelve seasons. The Big Bang Theory’s version of String Theory considers the fundamental particles we perceive in three dimensions as strings embedded in multidimensional spacetime (4). 

Sheldon explaining String Theory to Penny.

Spacetime is a mathematical model that physicists use to fuse the three physical dimensions––length, width, and height––with time into a single four-dimension continuum. Using this framework, scientists can predict the behavior of objects’ interactions with mass and energy. Therefore, for years, scientists have worked with spacetime to develop a deeper understanding of elementary particles and their interactions. String Theory was born out of spacetime calculations as it lined up with some general trends scientists observed, but proving it was quite difficult in reality. 

In the show, String Theory is “solved” by the unique team of brilliant physicist Sheldon Cooper and pharmaceutical sales representative Penny Hofstadter in the eleventh season. Unlike her friends, Penny is not a science expert and many jokes in the show revolve around her cluelessness while surrounded by scientific geniuses. While explaining the basics of String Theory to Penny, Sheldon explains that String Theory expressed in eleven dimensions produces Einstein’s relativity equations, which gives it solid mathematical grounding. This detail is supported by real-life physics research stating that Einstein’s theory of general relativity agrees with the merits of String Theory (5). This mathematical proof convinced many physicists to subscribe to String Theory, notably Stephen Hawking. The scene continues with Penny’s seemingly idiotic suggestion that if there really are tiny strings, they would get tied up into knots. Sheldon initially dismisses her idea claiming that knots cannot exist past the fourth dimension until he is hit with an epiphany — what if they consider the knots as sheets? (6)

While the scene cuts after Sheldon’s discovery, Penny later arrives home and casually drops the phrase, “Sorry, I had to stop at Sheldon’s and help him solve String Theory,” which is played as a joke given her lackluster background in science (6). The scene mainly pokes fun at how someone as clueless as Penny could, in an instant, solve something that had bamboozled Sheldon and every other theoretical physicist for years. After pursuing this theory, Sheldon later publishes a paper about his solution using sheets instead of knots, which wins him a Nobel prize (4). So, was the proof of String Theory as simple as considering knots as sheets? Unfortunately not. While it is true that knots cannot be expressed in more than four dimensions, they also cannot be expressed as sheets because the two shapes’ topologies are completely different (7). While many theoretical physicists accept String Theory as a working understanding of the basic interactions in the universe, it is yet to be proven officially. The theory’s requirement of more than four dimensions is challenging to prove mathematically or even think about experimentally. Therefore, it remains a theory with its merits and limitations. Overall, The Big Bang Theory does a great job sticking to the scientific principles of such a complex theory and is correct in most of the logic and calculations regarding String Theory. However, for dramatic effect, they pay off the ending of the show by having Sheldon Cooper win a Nobel prize for “solving” String Theory, when in reality it is yet to be done. So, once again, we are painfully reminded that not everything we see on TV can be trusted.


  1. O’Luanaigh, Cian. (2014, January 17). Fifty years of Quarks. CERN. Retrieved from,interaction%20symmetry%20in%20particle%20physics.
  2. Simple Science. (n.d.). Particle Physics. Retrieved from,which%20are%20protons%20and%20neutrons
  3.  Wood, Charlie. Stein, Vicky. (2023, May 18). What is string theory? Retrieved from
  4. The Big Bang Theory Wiki Editors. (n.d.). String Theory. Retrieved from
  5. Hugget, Nick. Vistarini, Tiziana. (2014). Deriving General Relativity From String Theory. Retrieved from
  6. Vega, Edgar. (2019). Penny Solves String Theory. Retrieved from
  7. Murphy, Paul Austin. (2022, October 6). Why The Big Bang Theory’s Sheldon Cooper Gave Up on String Theory. Retrieved from