A less useful but,perhaps, more interesting example of relativity at work is the colour of Gold http://en.wikipedia.org/wiki/Relativistic_quantum_chemistry#Col

A less useful but,perhaps, more interesting example of relativity at work is the colour of Gold http://en.wikipedia.org/wiki/Relativistic_quantum_chemistry#Color_of_gold_and_caesium http://en.wikipedia.org/wiki/Relativistic_quantum_chemistry#... I believe that this has been posted before