Word: massless
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...have waited a long time, at least in puny human terms. In 1964, Higgs theorized a mechanism to explain how two types of particle, massless like everything else immediately after the Big Bang, came to acquire different masses as the universe cooled. Using this mechanism, which two Belgian physicists simultaneously posited, scientists were able to extrapolate how all particles get their mass. Higgs thus plugged a major hole in the Standard Model, the far-reaching set of equations on the interaction of subatomic particles that is the closest modern physics comes to a testable "theory of everything...
...particles. Theorists struggled for decades to understand why; finally, in the late 1990s, Koshiba?s Super-Kamiokande detector in Japan proved that the missing neutrinos had really just converted into another form, undetectable by Davis's machine (for complex reasons, this also implied that neutrinos, long thought to be massless, actually do have a tiny mass...
...idea behind solar sailing is simple. Although light is made of massless particles called photons, such ephemeral things exert real pressure, especially when they flow from so close a source as the sun. Attach a sail of lightweight Mylar or other material to a spacecraft, set it up in the path of that outrushing energy, and you ought to be able to move in almost any direction...
...Perhaps some electron neutrinos were switching identities, changing by a process called oscillation into muon or tau neutrinos (the two other varieties) en route to Earth. If so, existing detectors could never see them. And while some of the fine print in the laws of physics says that a massless neutrino can't change its stripes, a neutrino with even a tiny bit of mass might. If neutrinos have mass, they can change; conversely, if they can change, they must have mass, despite what textbooks have been saying for decades...
...simply as possible. The model holds that nearly all the matter we know of, from garter snakes to galaxies, is composed of just four particles: two quarks, which make up the protons and neutrons in atomic nuclei; electrons, which surround the nuclei; and neutrinos, which are fast-moving, virtually massless objects that are shot out of nuclear reactions. These particles of matter are, in turn, acted upon by four forces: the strong nuclear force, which binds quarks together in atomic nuclei; the weak nuclear force, which triggers some forms of radioactive decay; electromagnetism, which builds atoms into molecules and molecules...