From the back row of the room, a young man with a lean build and a gaunt face, with an enormous unruly quiff and two lively eyes, stood up.

In very rough German and with a rather surprising manner, he said:

"What Professor Einstein said is not stupid, but the second equation he wrote does not follow from the first. In fact, it requires additional assumptions that have not been made and, what is worse, it does not satisfy a criterion of invariance, as it should".

A glacial silence fell in the room and everyone turned to stare in disbelief and amazement at that bizarre and bold little boy.

Everyone except Einstein, who began to stare absorbedly at the blackboard, stroking his moustache with his hand.

After a minute he turned and, acknowledging his mistake, said:

"The observation of that young man over there is perfectly correct. I therefore ask you to forget everything I have said to you today."

That intrepid young man of 22 years was Lev Davidovich Landau, destined to become the leading theoretical physicist of the Soviet Union, one of the greatest geniuses of all time.

Prof. Vincenzo Giordano

The anecdote is told by Otto Robert Frisch in his autobiography "What little I remember"