read einstein's clocks, poincaré's maps: empires of time by peter galison
einstein wrote: "newton, forgive me"
light, einstein said, always travels by us at the same measured speed - 300,000 kilometers per second - no matter how fast the light source is traveling. this was certainly not how everyday objects behaved. a train approaches and the conductor throws a mailbag forward toward a station; it goes without saying that someone standing on the station platform sees the bag approach at the speed of the train plus the speed at which the conductor habitually hurls mail. einstein insisted that light was different: stand, your lantern raised, at a fixed distance from me and i see the light travel by me at 300,000 kilometers per second. hurtle toward me on a train, even one moving at 150,000 kilometers per second (half the speed of light), and i still see the light from your lantern go by me at 300,000 kilometers per second..the speed of the source does not matter to the velocity of light
for reasonable source speeds, the speed of sound does not depend on the velocity of the source: once a sound wave is started, it moves through air at a fixed speed
across the street from his bern patent office was the old train station
when sailors or geographers determine longitude..they must, without being in paris, calculate parisian time..if the north star is straight overhead, you are on the north pole; if it is halfway to the horizon, you are at the latitude of bordeaux; if it is on the horizon, you are at the latitude of ecuador
jovian eclipses
miners upstream of an explosion in the air supply are usually burned, while those downstream are asphyxiated
"as for the geodesic origin of the metric system," that pride of the french revolution..upon its adoption in 1799, the meter was supposed to be exactly one ten-millionth of a quarter of the earth's circumference
in paris and vienna during the late 1870s, industrial steam plants injected subterranean pipes with compressed air, then modulated that pressure to set clocks pneumatically around the city
before the nineteenth century, clocks normally did not even have minute hands
will you have the goodness to inform me whether the time furnished at the w[estern] u[nion] telegraph office boston from your observatory is actual cambridge time, or boston time
russia, with its 180-degree longitudinal expanse
happily, he reported, the british antimeridian (the line 180 degrees removed from greenwich) ran through the bering strait
from the mid-1860s to the 1890s, france, britain, and the united states raced to establish simultaneity over a sprawling network of undersea telegraph cables to fix longitudes and redraw the global map
in 1867 these older techniques fell by the way as the first cable spanned the atlantic ocean, closing the longitudinal gap between england (greenwich observatory) and the united states (naval observatory, washington)
navigators had been using total eclipses for centuries; columbus used one to fix his longitude on his transatlantic explorations
a small group of reconnaissance topographers joined general sherman on his march
the duodecimal system
the sexigesimal second (1/3,600 of an hour)..lay in the crosshairs of this decimal revival
the entire instrumentarium of navigators, moreover, would be rendered obsolete overnight. sailors might as well throw their chronometers, pendula, watches, theodolites, and sextants into the briny deep
seconds..corresponded so closely to the typical adult heartbeat, our "natural" small temporal unit
the whole human organism made the second special..a time unit that was approximately a heartbeat long
hume, whose treatise of human nature i had studied avidly and with admiration shortly before discovering the theory of relativity
time cannot be absolutely defined, and there is an inseparable relation between time and signal velocity
plato's cave scene in the republic..a prisoner, constrained to view but the shadows of objects dancing on the walls, would find it painful to learn to peer directly at the full three-dimensional objects behind the prisoner's head, much less at the light that lit them
four-dimensional physics
the eiffel tower began broadcasting simultaneity on 23 may 1910, its distinctive tones available to be plucked out of the ether (so to speak) from canada to senegal. at first the signals followed paris time; only the next year, on 9 march 1911, did france agree to reset its (and algeria's) clocks by the 9 minutes and 21 seconds that riveted them to greenwich
"now he has also taken leave of this strange world a little before me. this means nothing. for us devout physicists, the division between past, present, and future is only an illusion, if a stubborn one"
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