Ghostly Particles All About

Mercury, January/February 2006 Table of Contents

Courtesy of AIP's Emilio Segrè Visual Archives.

by James C. White II

Late in the year 1930, a tired-looking fellow named Wolfgang Pauli was sitting at his small, cluttered desk and working on a grand, seemingly intractable problem: what causes radioactivity? Papers were piled around him, and a single lamp illuminated his workspace. Rather than give up on this problem, Pauli’s imagination leaped in that darkness, and our understanding of Nature was propelled forward.

At the time, however, even Dr. Pauli saw his answer to the question of radioactive decay as a "desperate remedy." Indeed, it would be 26 years before his ghostly solution was even verified.

Pauli was later awarded the Nobel Prize in physics for his simply beautiful thoughts about how Nature controls its matter. An atom is a small assembly of teensy electrons (negative charge) that surround a concentrated nucleus of protons (positive charge) and neutrons. Radioactivity refers to the process by which really big nuclei, which are made of large numbers of protons and neutral neutrons—like, say, nuclei of uranium or radium—rid themselves of excess energy. Big nuclei have trouble holding themselves together, and those termed radioactive literally fall apart and release energy. The products of the break-ups are other nuclei and small, quickly moving particles.

The mystery about which Pauli was doing some heavy ciphering involved the remnants of big nuclei. He found that some energy was lost during the decay—or so it appeared from his complicated calculations. But this could not be correct. Nature is a wonderful accountant: there are certain things one does not lose, and energy is at the top of the list. As nature might say, "Energy is never lost…even if one prefers creative accounting!"

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