isomers

You may have noticed that I have not posted much recently. One reason being that I have several interesting books lined up to read. Currently, I am halfway through Abraham Pais' biography of Niels Bohr. This is my favorite quote so far:
"The first thing Bohr said to me was that it would only be profitable to work with him if I understood that he was a dilettante. ... He explained how he had to approach every new question from a starting point of total ignorance. ... I thought of his remarks some years later, when I sat at his side during a colloquium in Princeton. The subject was nuclear isomers. As the speaker went on, Bohr got more and more restless and kept whispering to me that it was all wrong. Finally, he could contain himself no longer and wanted to raise an objection. But after having half-raised himself, he sat down again, looked at me with unhappy bewilderment, and asked, 'What is an isomer?'"