Pi is a mathematical constant. It is the ratio of the distance around a circle to the circle's diameter. This produces a number, and that number is always the same. However, the number is rather strange. The number starts 3.14159265... and continues without end. Numbers like this are called irrational numbers.

The diameter is the longest line which can be fitted inside a circle. It passes through the center of the circle. The distance around a circle is known as the circumference. Even though the diameter and circumference are different for different circles, the number pi remains constant: its value never changes. This is because the relationship between the circumference and diameter is always the same.

• Pi is the number of times a circle’s diameter will fit around its circumference
• There is no zero in the first 31 digits of Pi
• Pi has 6.4 billion known digits – it would take a person approximately 133 years to recite all of them without stopping
• At position 763 (known as Feynman Point), there are six nines in a row
• Some people believe Pi contains the answers of the universe. (But on some days, a slice of pie holds all the answers to the universe!)
• It took nine hours for the Memorized-Digits-of -Pi world record holder to recite over 44,000 digits
• Pi Day (March 14) is also Albert Einstein’s birthday!
• Pi is irrational — no, not like my mother. An irrational number is one that cannot be expressed as a ratio of integers
• Johann Lambert proved Pi is irrational in 1768
• The symbol for Pi (π) has been used regularly for 250 years
• Pi has been studied by the human race for 4,000 years
• Many mathematicians claim that it is more correct to say the a circle has an infinite number of coers than to view a circle as coerless. Stop and think about that for a second.
• Pi was first calculated by Archimedes of Syracuse. He was reportedly so engrossed in his work that he did not notice when the Roman soldiers conquered the city of Syracuse. When a Roman soldier approached Archimedes, he yelled in Greek “Do not touch my circles!” The Roman soldier quickly cut off his head and moved on.
• If you printed a billion decimals of Pi in ordinary font it would stretch from New York City to Kansas. We recommend you don’t try and print out Pi!