Do you like pi? Pi is the ratio of a circle's circumference (the distance around it) to its diameter (the distance across it). 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.Celebrating Pi
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.
Your local science museum may have a celebration planned, or you can do some of these activities:
- Explore the Teach Pi website. Be sure to try looking up your phone number in pi (the link is near the bottom left corner) and sing the Pi Day carol (under the “Music” heading).
- 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 a 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.
- 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.
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| (Einstein in Legos, at Legoland.) |
- 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; he was an inspiration for Yoda's eyes (Star Wars), cartoons of “mad scientists,” and "Doc" on Back to the Future; and a famous photo of Einstein sticking out his tongue was sold for more than 70 thousand dollars!
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