Word: second
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Dates: during 1930-1939
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Last week The Times published the second volume of its history.* (Volume I, the story of Bohemian Thomas Barnes, its first great editor, whose blasts against the aristocracy won The Times its cherished nickname, "The Thunderer," was published three years ago.) Volume II is the story of the triumvirate that shaped The Times's policies between...
...great Galileo Galilei (1564-1642) tried to measure the velocity of light by means of lantern signals between mountain tops. Naturally he failed. Light travels about 186,270 miles (more than seven times the circumference of Earth) in one second. In modern physics, light is regarded as the fastest thing in the universe, and its velocity in empty space as a fundamental constant of nature...
...through the teeth of a spinning cogwheel. The light struck a mirror, bounced back to the wheel. The wheel had been timed to move just enough in the brief interim for the teeth of the wheel to intercept the light as it was reflected. By timing the revolutions per second of the cogwheel and measuring the distance to the mirror, it was easy to calculate the speed of the light...
...Abraham Michelson, in his final experiments, reflected light back & forth ten times in a mile-long vacuum tube from the faces of a rapidly spinning, 3 2-sided mirror. Velocity measurements completed by his successors after Michelson's death yielded an average figure of 186,270.75 miles per second. But in individual runs there were unexplained, periodic variations up to twelve miles a second. At first this caused excitement over possibility that the speed of light might not be constant (TIME, Dec. 25, 1933). The clamor was quieted by attributing the variations to "experimental error." So the velocity...
...principle is that of cutting a light beam up into a certain number of sections per second, then measuring the length of one section. This is like clocking a freight train when you know the length of the cars. If the cars are 30 feet long and you see that two of them pass a given point every second, you know the speed is 60 feet per second...