  Radioactive tracers and radiation sources have become indispensable to all phases of agricultural research. They have helped answer questions that seemed unanswerable. But there will always be more questions to put to Nature. The physicists-philosophers of 1890 were confident that they had obtained all significant knowledge of the physical universe. Discoveries of the next twenty years revealed the immaturity of that conviction. The modern poet Archibald MacLeish has dramatized the meagerness of knowledge: I will tell you all we have learned ... the lights in the sky are stars We think they do not see we think also The trees do not know nor the leaves of the grasses hear us.... Perhaps the most characteristic realization of the scientist today is that the universe is too complex to be fully described, that concepts must change repeatedly to absorb new findings, and that the recurring miracle of life is more majestic than any formula, any computer, or any rocket that man’s brain can devise. |
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