NATIONWIDE — This particular issue of the River Reporter is dated March 14, which in the U.S. is Pi Day.

A celebration of mathematics, one irrational number and pie, Pi Day came into being in 1988 courtesy of Larry Shaw at the Exploratorium in San Francisco. 

What is pi?

The ratio of the circumference of a circle to its diameter. (For more, see “Natural Pi,” below.)

It’s approximately equal to 3.14159 etc. etc. etc.

Etc.?

Because it goes on forever, like that Shari Lewis song, only there’s no pattern, so not like the song at all, really. 

Shari Lewis?

Never mind.

Even big circles?

Yes.

Even small circles?

Yes.

Pi is irrational

An irrational number is a real number that can’t be written as a ratio between integers, aka a fraction. In other words, it goes on and on forever, as noted above. 

Pi is transcendental

If you really want to know (because “transcendental” doesn’t mean what you might think it means), we’re just gonna send you here: web.archive.org/.

NASA celebrates Pi Day

For some people, Pi Day gives them the excuse to eat pizza or pie (or both), but to truly honor this wondrously useful number, according to a news release from NASA, a serving of mathematics is in order, too. 

Continuing a decade-long tradition, the education office at the agency’s Jet Propulsion Laboratory has cooked up a set of illustrated math problems involving real-life NASA science and engineering.

The pi-fascinated can:

Determine where the Deep Space Optical Communications (DSOC) technology demonstration aboard NASA’s Psyche spacecraft should aim a laser message containing a cat video—so that it can reach Earth (and set a NASA record in the process).

Figure out the change in the orbit of the asteroid Dimorphos after NASA intentionally crashed its Double Asteroid Redirection Test spacecraft into its surface.

Measure how much data will be captured by the NASA-ISRO Synthetic Aperture Radar (NISAR) satellite each time it orbits our planet, monitoring Earth’s land and ice surfaces in unprecedented detail.

Calculate the distance a small rover must drive to map a portion of the lunar surface.

Answers to all four challenge questions will be available on March 15.

The NASA Pi Day Challenge is accompanied by other pi-related resources for educators, K-12 students and parents. You’ll find lessons, posters, puzzles and more. 

Learn more about the NASA Pi Day challenge at go.nasa.gov/piday.

Born on a Pi Day

Albert Einstein

Died on a Pi Day

Stephen Hawking

Other mathematical holidays

Pi Approximation Day

July 22. Pi is the fraction 22/7, or 3.14.

Tau Day

The ratio of the circumference to the radius of a circle, which is equal to 2π (6.28318 etc. etc. etc.). Celebrated on June 28. Learn a lot more at tauday.com/.

e Day

e is a constant; it is infinite; it is often given a value of 2.7182818. So e Day is February 7. 

Want to learn more? Visit mathoverflow.net/.

But why Shari Lewis?

Never mind, we said.

Circles, etc.: What is pi good for?

You can, of course, use pi to get info about a circle. Beloved activity in math class!

But pi is also needed for antennae to connect with satellites. (So wifi on airplanes can work.) 

NASA uses pi to “map the moon, measure Earth’s changing surface, receive laser-coded messages from deep space, and calculate asteroid orbits.” 

Pi Day activities

If you’re in San Francisco: www.exploratorium.edu/visit/calendar/pi-p-day

If you’re not:

www.exploratorium.edu/pi/guide-celebrating-pi-day

Pi Day video content

Recreational mathematician, comedian and YouTuber Matt Parker has created a great playlist of videos from his channel related to calculating the value of pi. Find it at www.youtube.com/playlist.

Pi in food

Yes, yes, pie. Obviously pie r round. 

Pizza r2.

Pilish (as in “Pi-lish”)

You can memorize the digits of pi by remembering a series of words. The number of letters in each successive word corresponds to an equally successive digit. 

The famous example is by Sir James Jeans: “How I need a drink, alcoholic in nature, after the heavy lectures involving quantum mechanics!” Do you see? 3.141592…

Michael Keith took the idea a step further and wrote stories, poetry, a book and more in Pilish. 

But Shari Lewis!

Fine. “The Song That Doesn’t End.” Look it up; you’ll thank us later. 

Sources: www.jpl.nasa.gov/, www.honeywell.com/ and  www.mathnasium.com

Natural pi

We asked retired math professor and occasional River Reporter contributor John Pace for his thoughts on pi. He kindly obliged. 

“Pi (π), a noteworthy ‘natural’ constant, famously arises by construction,” he said. “Merely divide the distance around a circle (circumference) by the distance across, measured through the center (diameter). 

But it’s not a new concept. “Thousands of years ago, people in ancient civilizations already knew that this ratio of measurements was roughly 22/7 or, more roughly, 3,” he said.

In the First Book of Kings in the Hebrew Scriptures (7:23) you’ll find a reference (here in part) to a circle “measuring 10 cubits from rim to rim; it took a line of 30 cubits to measure around it.”

In other words: 3, rather than 3.14 et.al., Pace said.

“Of course it may be constructed from any circle. The actual biblical-verse Pi liberally populates advanced mathematical concepts with the often-associated elegant formulae that address them… suffice it to say Pi comes in many surprising flavors!”