This conundrum emerged gradually in the late 1950s and early 1960s. To explain how the known elementary particles could possibly have mass at allrequired fresh ideas. And when they looked at how the weak nuclear force affected electrons and quarks and neutrinos, they discovered that the old way of putting in the electron mass by hand wouldn’t work anymore it too would break the equations. Unfortunately, the physicists found they could not put masses for the W and Z particles by hand into their equations the resulting equations gave nonsensical predictions. However, the W and Z differ from the photon, in that they do have a mass - they are as massive as an atom of tin, over a hundred thousand times heavier than are electrons. The physicists already knew that electric forces are related to photons, and then they realized further that the weak nuclear force is related, similarly, to so-called “W” and “Z” particles. But as they began to learn more about the weak nuclear force, one of the four known forces of nature, a serious problem emerged. Even though they didn’t know where the electron’s mass came from, they found it easy to put the mass, by hand, into their equations, figuring that a full explanation of its origin would turn up later. In the middle of the last century, physicists learned how to write equations that predicted and described how electrons behaved. And so the question about the electron became subsumed in larger questions: Why do particles like electrons, quarks and neutrinos have mass, while photons do not? First it was learned that light is made from particles too, called photons, that have no mass at all then it was learned that atomic nuclei are made from particles, called quarks, that do have mass and recently we found strong indications that neutrinos, elusive particles that stream from the sun in droves, have masses too, albeit very small ones. Complicating and enriching the puzzle are the many discoveries, over the past century, of other apparently elementary particles. The mass of the electron, and its origin, has puzzled and troubled physicists since it was first measured. And so the very structure and survival of ordinary materials is tied to a seemingly esoteric question: why does the electron have a mass at all? Reduce the electron’s mass by more than a factor of a thousand or so, and atoms would be so delicate that even the leftover heat from the Big Bang that launched our universe could break them apart. If you managed somehow to decrease the mass of the electron, you’d find atoms would grow larger, and much more fragile. But what most of us didn’t learn, unless we took a college class in physics, is that an atom’s size - the distance across it - depends mainly on the electron’s mass. We learned in school that the mass of an atom comes mostly from its tiny nucleus the electrons that form a broad cloud around the nucleus contribute less than a thousandth of an atom’s mass. Some of these blurry areas may soon become clearer, revealing details about the world that we cannot yet discern. And the “Higgs boson” hullabaloo that you’ve been hearing about has everything to do with these deep questions at the heart of our own existence. Puzzles dating back a century still remain unresolved. Only around 1900, when the actual size of atoms could finally be inferred from multiple lines of reasoning, and the electron, the subatomic particle that inhabits the outskirts of atoms, was discovered, did the atomic picture of the world come into focus.īut even today, some lines in this picture are still fuzzy. Such facts about the world we take almost for granted, but they were still hotly debated late into the 19th century. These come in about 100 types, called “the chemical elements”, and are typically found arranged into molecules, as letters can be arranged into words. Most of us learned in school, or from books, that all the materials around us - everything we eat, drink and breathe, all living creatures, and the very earth itself - are made from atoms.
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