Most people regard scientists as explorers; and this is always true: or very nearly always true.

Imagine a handful of people shipwrecked on a strange island and setting out to explore it. One of them cuts a solitary path through the jungle, going on and on until he is exhausted or lost or both. He eventually returns to his companions, and they listen to him with goggling eyes as he describes what he saw; what he fell into, and what bit him. After a rest he demands more supplies and sets off again to explore the unknown. Many of his companions will be doing the same, each choosing his own direction and pursuing his pioneering path.

The shipwrecked explorers of such an unmapped island and the scientific explorers of our strange and unpredictable universe have some characteristics in common. Neither group ever reaches a brick wall where no further advance in knowledge is possible. A scientist may exhaust himself; he frequently exhausts his colleagues, always exhausts his money, but never exhausts his subject. Sighing for new worlds to conquer is not an occupational hazard of his profession. The second common characteristic of both types of explorers is that their narrow paths rarely cross. Spoke-like, their trails into the unknown leave the little hub of common knowledge far behind and their fellow explorers further and further out of touch.