The value of pi is the ratio of the circumference of a circle to its diameter. Therefore, you can determine the value of pi by drawing ANY perfect circle (either physically or in a computer program simulation), then measure it's circumference and diameter, take the ratio and that's it!

The value of pi correct to seven decimal places is: 3.1415926. Pi is an irrational number, i.e. it cannot be expressed by a whole number or a common fraction. According to Encarta Encyclopedia pi has been worked out to a million decimal places by a computer without coming to a whole fraction.
Answered by: Doris Thomas and Anton Skorucak

'The strength and weakness of physicists is that we believe in what we can measure. And if we can't measure it, then we say it probably doesn't exist. And that closes us off to an enormous amount of phenomena that we may not be able to measure because they only happened once. For example, the Big Bang. ... That's one reason why they scoffed at higher dimensions for so many years. Now we realize that there's no alternative... '