From rockets to cancer research, here's how the number pi is embedded in our lives

TECH

From rockets to cancer research, here's how the number pi is embedded in our lives

2026-03-14 12:01 Last Updated At：12:33

LOS ANGELES (AP) — Math nerds and dessert enthusiasts unite to celebrate Pi Day every March 14, the date that represents the first three digits of the mathematical constant pi.

Representing the ratio of a circle's circumference to its diameter, pi is approximately equal to 3.14159 — but its digits go on forever. In school, you might have used it to calculate the area of a circle or the volume of a cylinder. But the applications of pi are endless and part of every corner of our world.

The holiday was created in 1988 by Larry Shaw, a physicist at the Exploratorium science museum in San Francisco.

“He had a very open and expansive view of the world and saw an opportunity with this number, mathematical concept, to invite people into the joy of mathematical learning,” said Sam Sharkland, program director of public programs at the museum, who worked with Shaw before he died in 2017.

While it began as a small staff celebration featuring pie, it soon turned into a grand procession where hundreds of visitors marched around the pi shrine, each carrying a digit. Attendees often show up early to claim their favorite digit for the parade. One woman who has the symbol tattooed on her neck comes every year and marches near the front with a pi flag, Sharkland said.

The celebration begins at 1:59 p.m., signifying the next three digits of pi.

Here are a few ways pi is being used on the cutting edge of science.

In Artur Davoyan's field of mechanical and aerospace engineering, pi is so fundamental that it would be hard to pinpoint one use case for it, he said.

Pi is part of “literally every single formula that you would use to do any calculation, like for spacecraft motion, for materials and how they work, or propulsion systems,” said Davoyan, a professor at the University of California, Los Angeles.

Anything that is round or has cyclical or repeating properties — such as radio waves — involves pi. Even squares or irregular blobs can be broken down into a series of progressively smaller circles and calculated using pi, Davoyan said.

Davoyan's research looks at how to create new propulsion systems to send spacecrafts more quickly to the far reaches of the solar system to gather and send back information to Earth. He pointed to NASA’s Voyager 1 and 2, which launched in 1977 but didn't reach interstellar space until 2012 and 2018.

To send a signal to those space probes, NASA must calculate Earth's exact position in orbit around the sun and design antennas for communication using pi. Then scientists use pi once more when receiving and breaking down complex signals that are being beamed back to Earth.

“Say aliens send something to us, something that we don’t know how to deal with,” Davoyan said. “So the very first thing that you would do, you would try to split it into simple functions... and turns out that when you do this operation, you will naturally have pis in it.”

Pi also comes up frequently when studying small amounts of fluids.

Dino Di Carlo, chair of the bioengineering department at the UCLA Samueli School of Engineering, conducts research that involves creating little particles out of polymers that act as tiny test tubes for cells. This is used as an important tool to examine cells closely and learn about their functions and what's inside them.

The pi constant is used in calculating how to form those droplets, surface tension calculations that define how droplets can break up, and how researchers can control the size of those volumes, Di Carlo said.

Di Carlo is using this technique to find antibodies — small proteins that fight diseases in your body — that could block signals put out by cancer cells.

Pi is also an important part of calculations when looking at how liquids flow through tubes and barriers. One example is when the fluid sample slowly flows sideways in a take-home COVID-19 test.

Di Carlo used these properties to devise a new test for Lyme disease that can be completed in 20 minutes, rather than days or weeks like previously.

“As an engineer and scientist, (pi) is just a part of life,” Di Carlo said. “Maybe I’ve taken it for granted.”

Vance and Iranian officials arrive in Switzerland to launch talks on Tehran’s nuclear program

OBBUERGEN, Switzerland (AP) — U.S. Vice President JD Vance and senior Iranian officials arrived in Switzerland on Sunday to formally launch negotiations over Tehran’s nuclear program, build out the fragile interim deal to end the war in Iran and keep the Strait of Hormuz open.

The framework was signed last week, and now top American and Iranian negotiators are in a 60-day sprint to reach an agreement on the technical details that hold massive implications for the world economy and global security.

Yet only days after signing the agreement, it is being stress-tested after fighting escalated in Lebanon between Israel and the Iranian-backed militant group Hezbollah — and by the subsequent announcement by Iran’s military that it had again closed the vital waterway that transits one-fifth of the world’s traded oil and natural gas. A renewed ceasefire in Lebanon, brokered on Saturday, appeared to be holding up.

Vance first sat down for talks with Pakistani Prime Minister Shehbaz Sharif and Staff Field Marshall Asim Munir, who has served as a key intermediary between Washington and Tehran throughout the conflict.

“What’s up, man! Good to see you,” Vance said as he warmly greeted Munir, who serves as Pakistan's army chief.

Sharif met separately with Iranian Parliament Speaker Mohammad Bagher Qalibaf, who is leading Tehran's delegation, and Foreign Minister Abbas Araghchi.

Mediators from Qatar were also on hand at the mountainside resort near Lake Lucerne.

Rafael Grossi, chief of the U.N. nuclear watchdog, the International Atomic Energy Agency, met with Swiss Foreign Minister Ignazio Cassis on the sidelines of the gathering. The agency had monitored the 2015 nuclear deal negotiated between the U.S. and Iran under the Democratic Obama administration. Trump, a Republican, withdrew the U.S. from the agreement in 2018.

Iran’s main focus during the negotiations will be the ongoing war between Israel and Lebanon, Iranian Foreign Ministry spokesman Esmail Baghaei told Iran’s state news agency.

Iran is insisting that the deal’s implementation start with the part of the deal that calls for a cessation of all wars, including between Israel and Hezbollah. Baghaei said the U.S. “has been unable or unwilling” to hold Israel to the ceasefire.

Iranian officials were to hold their own meetings with Pakistani and Qatari mediators before a planned four-way meeting that would include the U.S. negotiating team.

Iran is cautiously approaching the negotiations given its previous experience with the U.S. negotiations on the nuclear issue, which twice in the past year have been interrupted by massive strikes against the country. “The implementation of any document is more important than its signing,” Baghaei said Sunday.

But Iran’s president added that Iran will maintain its right to a nuclear program.

“What is certain is that we will never back down from the right to enrich uranium, and the other side is also forced to accept it,” Iranian President Masoud Pezeshkian said on Sunday, according to Iran’s state media.

Vance had originally been slated to be on the ground at the Bürgenstock resort near Lucerne on Friday, but his departure from the United States was delayed after fighting escalated in Lebanon and Iranian officials canceled plans to attend the talks.

U.S. Central Command disputed Iran’s claim that it had once again shuttered the strait and said U.S. forces continued to monitor the situation to ensure traffic continues to flow through the waterway. Vance has said that millions of barrels of oil have moved through the strait in recent days.

Vance departed the U.S. just after Iranian state TV said Iran’s negotiators had arrived in Switzerland.

The vice president was joined by special envoy Steve Witkoff and Jared Kushner, President Donald Trump's son-in-law, for Sunday's talks. Witkoff and Kushner were on the ground in Switzerland ahead of Vance to begin sifting through the technical details of the nuclear talks.

Vance and his wife, second lady Usha Vance, arrived at Emmen Air Base outside Lucerne just before 6 a.m. local time, according to his office.

While Vance said he planned to be in Switzerland for just “a day or two,” leaving much of the detailed negotiations to be spearheaded by Witkoff and Kushner, his role in the talks has heightened scrutiny of the vice president at a time when he’s actively considering a 2028 presidential campaign.

Trump and Vance have come under searing criticism from parts of their own party for the deal, with Republican hard-liners unfavorably likening it to a nuclear agreement signed by the Obama administration that Trump and the GOP have insisted did nothing to actually terminate Iran’s nuclear program.

The agreement signed by Trump and Iranian President Pezeshkian immediately allows Tehran to sell its oil freely and paves the way for Iran to tap into billions of dollars in assets that are currently frozen. It also calls for Iran to dilute its stockpile of highly enriched uranium, believed to be buried under nuclear sites that were targeted in U.S. strikes last summer.

The agreement says commercial vessels can pass through the Strait of Hormuz for 60 days without a charge, but does not preclude future fees imposed by Iran. Trump made his own threat on Saturday to levy U.S. tolls on the strait if there is no deal with Iran in 60 days, insisting in a social media post that the money would be for “services rendered as the Guardian Angel to the countries of the Middle East.”

The Trump administration has been working to reassure global markets that the Iran war has been merely a blip on oil prices, as Americans have complained the conflict resulted in hiking gasoline prices ahead of peak summer travel months. After the White House announced the deal a week ago, oil futures dropped almost 8% — and markets are expected to closely track the progress of talks when they open for trading on Sunday evening.

Further complicating matters, neither Israel nor Hezbollah is a signatory to the deal between the U.S. and Iran, and Israeli Prime Minister Benjamin Netanyahu has vowed to keep his forces in southern Lebanon until any threat to Israel is eliminated. Hezbollah has refused to halt its attacks unless Israel commits to withdrawing from Lebanon.

Fighting between Israel and Hezbollah in the initial days after the agreement between the U.S. and Iran killed 47 people in Lebanon, as well as four Israeli soldiers.

Kim reported from Washington. Associated Press writers Munir Ahmed in Islamabad, Amir Vahdat in Tehran, Iran, and Melanie Lidman in Tel Aviv, Israel, contributed to this report.