A short while ago a mathematician, Bob Palais, posted an article on his blog called Pi Is Wrong!
More recently, a new item appeared online, launching The Tau Manifesto on what they call Tau Day.
Michael Hartl's Tau Day article expands upon the original "Pi Is Wrong!" article, and proposes a new mathematical term and constant, Tau (the Greek letter τ) which equals 2π.
These people make a lot of sense. Read and enjoy the articles. I think they may well open your eyes.