Why can't Pi be expressed as a fraction? -- Edward Lockhart
In one sense it can in the same way that most any number can be translated into a fraction Pi / 1; however that's a cop out and a circumvention of the question. The truth is that we're unable to express it as a fraction because Pi is an irrational number.
Beyond that I can only tell you that irrational numbers are like the drunken friend you brought to your kid brother's wedding that tried to fuck a tree because he was convinced that doing so made him more of an environmentalist than you. In other words: they're fucked up and I don't like them.