Nonsense Equations

A physicist has been conducting experiments and has worked out a set of equations which seem to explain his data. He asks a mathematician to check them. A week later, the mathematician calls "I'm sorry, but your equations are complete nonsense."

"But these equations accurately predict results of experiments. Are you sure they are completely wrong?"

"To be precise, they are not always a complete nonsense. But the only case in which they are true is the trivial one where the field is Archimedean..."