![]() ![]() The two hyperfine levels of the ground state of theĬaesium-133 atom. ![]() That new definition wasĪccepted in 1967 and refined in 1997 by the CGPM as being “the duration ofĩ,192,631,770 periods of the radiation corresponding to the transition between Week.) a new, more stable definition had to be found. The earth is slowing down, but I wouldn’t worry about it affecting your work Since this a variable amount of time (the spin of The length of time that takes the earth to go around the sun, or at least for the earth However, this definition of a second is not really good enough, since it is based on Know that this means there are approximately π x 10 7 seconds in a year. Second was 1/31,536,000th of a year, give or take. So, for a long time, a second was simply 1/60th of a minute, which was 1/60th ofĪn hour which was 1/24th of a day, which was 1/365th of a year. Subdivided into 60 divisions called second minutes, but these days we’re lazy and we just Lot in the counting system of the ancient Babylonians). The hour was subdivided into 60 equal divisions called prime minutes (60 was used a Interestingly, since it was originally based on the amount ofĭaylight in a day, its length would vary depending on when in the year it was The division of one-twelfth of a day was the basis of what we Thumb and touching each of your phalanges (look it up if you think that I’mīeing rude.). Have 12 bones in our fingers (3 on each), so you can count to 12 by using your Inches in a foot, 12 months in a year, and 12 zodiacal symbols. Time - which is why we have leftovers still today like 12 eggs in a dozen, 12 Why 12? Well, many counting systems were based on 12 once upon a Similarly the time between sunset and sunrise was also divided In many early civilizations, the time between sunrise and sunset was was divided intoġ2 equal divisions. The sun goes up, you wait a while, the sun goesĭown, you wait a while and the cycle repeats itself. If you think back, way back to a time before clocks and watches, back before we evenĭiscovered fire, and then think about how people would have marked time. That set of measures is called the Syst ème International d’Unit és or SI, although most normal people call it the metric system. This group oversees a standard set of measurements for things like time, mass,Īnd distance, just to name a few. Meeting is called the Conf érence G én érale des Poids et Measures or CGPM. Governments of 51 countries who are part of a group called the Metre Convention. Introduction to Units, Geometry, Math and Calculus 1.1 UnitsĮvery four years there is a meeting held in Paris with representatives of the ![]()
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