“This bird thinks!”

No two physicists could have been more different than Dirac and Feynman. As much as Feynman was an extrovert, so much was Dirac and introvert. The middle child of a Swiss teacher of French, in Bristol, England, young Paul was made to follow his father’s rule to address him only in French, in order that the boy learn that language. Since Paul could not express himself well in French, he chose to remain silent, an inclination that would remain with him the rest of his life. It is said (and may be true) that Niels Bohr, the most famous physicist of his day, and Director of the institute in Copenhagen where Dirac went to work after receiving his Ph.D. at Cambridge, went to visit Lord Rutherford, the British physicist, some time after Dirac’s arrival. He complained about his new young researcher, who had not said anything since his arrival. Rutherford countered by telling Bohr a story along the following lines: A man walks into a store wanting to buy a parrot. The clerk shows him three birds. The first is a splendid yellow and white, and has a vocabulary of 300 words. When asked the price the clerk replies, $5,000. The second bird was even more colorful than the first, and spoke well in four languages! Again the man asked the price, and was told that this bird could be purchased for $25,000. The man then spied the third bird, which was somewhat ragged, sitting in his cage. He asked the clerk how many foreign languages the bird could speak, “none.” Feeling budget conscious, the man expectantly asked how much this bird was. “$100,000” was the response. Incredulous the man said, “What? This bird is nowhere near as colorful as the first, and nowhere near as conversant as the second. How on earth can you see fit to charge so much?” Whereupon the clerk smiled politely and replied, “This bird thinks!”