Every year the Royal Academy of Arts has its Summer Exhibition. A unique opportunity for amateurs to present their work alongside that of celebrated professionals. It is also a sign of the disconnect in the world of the modern art. Where amateurs tend to produce traditional paintings the professionals appear intent on defying convention and aiming to shock and confuse their audience. Stephen Sackur asks Charles Saumarez Smith, the Chief Executive of the Royal Academy have our ideas about what makes good art changed forever?