March 14 - Pi Day! And Einstein's Birthday!

Posted on March 14, 2021

Key Points

This is an update of my post published on March 14, 2010:

Do you like pie?

And do you like pi?

Pi is the ratio of a circle’s circumference (the distance around it) to its diameter (the distance across it).

Remember, the ratio is the same no matter how large or small the circle!

No matter how big or small a circle is, when you carefully measure the circumference and diameter and then divide the first by the second, you come up with the same number:

3.14159265358979323846264338327950288…

The decimal goes on and on—so far, computers have computed pi out to more than two TRILLION digits! The digits never end and never repeat. Any unending, non-repeating decimal like pi is called an irrational number.

Rounding Pi

Physicists use the first 39 digits of pi, but engineers only need pi computed to 5 or 6 “significant figures” (3.1416 or 3.14159). For most purposes, though, people round pi off to 3.14, which is why this date (3-14) is celebrated as Pi Day!

Proving Pi

1. Using non-stretchy string, carefully cut enough string to just go around a circle. This is your circumference string.

2. Now use your circumference string to measure across the circle’s exact middle. Cut it. This is your first diameter string.

3. Continue to measure and cut diameter strings until you run out of circumference string. How many diameter strings were there?

Here are more detailed instructions.

Celebrating Pi

Some years, local science museums and schools plan Pi Day celebrations. (Here is a virtual celebration.) But you can do stuff on your own, too, for sure!

Explore the Teach Pi website. Be sure to check out the Pi Day carols under the “Music” heading.

Read a poem about pi.

Look at the digits of pi. Try clicking “100,” “1,000” and so on, all the way up to a million. It’s interesting to guess what, say, 100,000 digits will look like, or whether there will be a lag for the computer to load (?) or compute (?) a million digits.

Eat pie. Or have a pie-toss or pie-eating contest.

Also on this date...
Happy Birthday, Albert Einstein!

Albert Einstein was born on this day in 1879 in Ulm, Germany. He came to the United States in 1933 to avoid the rising power of the Nazis in Germany.

A theoretical physicist, Einstein is one of the most famous scientists of all time. The special and general theories of relativity are some of his greatest contributions; Einstein predicted the bending of light by gravity (including gravitational lensing) and contributed to the photon theory and quantum theories. He won the 1921 Nobel Prize in Physics for his work on the photoelectric effect.

Did you know…?

In 1952, Einstein was offered the position of President of Israel. He said no. (Hopefully no, thank you.)

Einstein was a member of several civil rights organizations (such as the NAACP) and defended the character of W.E.B. DuBois when he was accused of being a Communist spy.

During his life and ever after, Einstein was so famous that his name pretty much means “genius”; his face has been immortalized on everything from Beatles album covers (Sgt.. Pepper’s Lonely Hearts Club Band) to Israeli money…