Pi Day falls on March 14, a date that points to the first digits of the mathematical constant pi, 3.14159. Pi represents the ratio between a circle’s circumference and its diameter, and its digits continue indefinitely. While the holiday can start as a classroom lesson—using pi to calculate areas and volumes—its applications reach into specialized work across engineering and biomedical science, according to examples discussed by researchers at universities including UCLA.
The Exploratorium in San Francisco helped shape the modern celebration. The Associated Press reported that the event was created in 1988 by Larry Shaw, a physicist at the science museum, and that it was built around making mathematics approachable to the public. Sam Sharkland, director of public programs at the Exploratorium, described Shaw’s broad thinking about teaching: “Tenía una visión del mundo muy abierta y amplia y vio una oportunidad con este número, este concepto matemático, para comunicar a la gente la alegría de aprender matemáticas”, señaló Sharkland, director de programas públicos del museo, quien trabajó con Shaw antes de que muriera en 2017.
AP described how the celebration grew from a small internal tradition with cake into a large visitor event. Sharkland said hundreds of visitors participate in a procession that circles the museum’s “pi sanctuary,” with attendees typically holding a digit to match the constant. He also said some arrive early to claim their preferred digit for the parade, and he cited a woman with a pi symbol tattooed on her neck who, according to Sharkland, attends every year and marches near the front with a pi flag. The celebration is set to begin at 1:59 p.m., a time tied to the next three digits of pi.
In science and engineering, Artur Davoyan, a professor at the University of California, Los Angeles, said pi is so central to the field that it is difficult to name a single use. He told AP that pi figures into “literalmente cada fórmula que usarías para hacer cualquier cálculo, como el movimiento de una nave espacial, los materiales y cómo funcionan, o los sistemas de propulsión”. Davoyan said that many systems involve round or repeating patterns, including radio waves, and he added that even shapes that are not perfect circles can be broken into smaller circles for calculation.
Davoyan also described how pi connects to deep-space technology and mission design. AP reported that his research focuses on creating propulsion systems to send spacecraft faster to the edges of the solar system so missions can collect and return information to Earth. He pointed to NASA’s Voyager 1 and Voyager 2, which launched in 1977 but did not reach interstellar space until 2012 and 2018, and he described a role for pi in both planning and analysis. In his explanation, sending signals to those spacecraft requires precise calculations about Earth’s position in its orbit and antenna communication design using pi, and then scientists rely on pi again when receiving and breaking down complex signals transmitted back to Earth.
Davoyan also framed pi as a tool that naturally emerges when scientists try to simplify unfamiliar information. He said, “Digamos que los extraterrestres nos envían algo, algo con lo que no sabemos cómo lidiar”, planteó Davoyan. “Entonces, lo primero que haríamos sería intentar dividirlo en funciones simples… y resulta que, cuando hacemos esta operación, de manera natural tendrámos pi en ello”. The point, as described by AP, was that mathematical structure can appear as researchers try to translate complex inputs into manageable parts.
In biomedical research and lab testing, the AP reporting highlighted the role of pi in work involving fluids and tiny droplets. Dino Di Carlo, head of bioengineering at UCLA’s Samueli School of Engineering, said his department creates small particles out of polymers that act like mini test tubes for cells, a setup used to study cell function and contents. AP reported that pi is used to calculate how such droplets form, including calculations tied to surface tension that influence how droplets break apart and how researchers can control droplet size.
Di Carlo said those droplet-based methods can support cancer-related research by helping find antibodies—small proteins that fight disease—that could block signals emitted by cancerous cells. AP also said pi figures into other fluid-flow calculations, including how liquids move through tubes and barriers. As a practical example, the story described how fluid samples can flow slowly sideways in a home COVID-19 test.
The AP account also connected those physics-and-fluid calculations to diagnostic development. It said Di Carlo used the properties of droplets and related flow behavior to develop a Lyme disease test that can be done in 20 minutes, rather than taking days or weeks as earlier approaches did. AP ended its pi-focused science examples with Di Carlo saying, “Como ingeniero y científico, (pi) es simplemente parte de la vida. Tal vez lo he dado por sentado”, an observation that captures the way a constant sometimes becomes background infrastructure for research rather than a topic students memorize.