Atomic Clocks
Scientists discovered some time ago that atoms and molecules have "resonances" and that each chemical element and compound absorbs and emits "electromagnetic radiation" within its own characteristic "frequencies". This we are told is highly accurate even over "Time and Space"。
The development of radar and the subsequent experimentation with high frequency radio communications during the 1930s and 1940s created a vast amount of knowledge regarding "electromagnetic waves", also known as "microwaves". which interact with the atoms. The development of atomic clocks focused firstly on microwave resonances in the chemical Ammonia and its molecules. In 1957. "NIST". the "National Institute of Standards and Technology", completed a series of tests using a "Cesium Atomic Beam" device, followed by a second program of experiments by NIST in order to have something for comparison when working at the atomic level. By 1960, as the outcome of the programs, "Cesium Time Standards" were incorporated as the official time keeping system at NIST。
The "Natural frequency" recognized currently is the measurement of time. used by all scientists, defines the period of "one second" as exactly "9,192,631,770 Oscillations" or "9,192,631,770 Cycles of the Cesium Atom's Resonant Frequency". From the "Macrocosm", or "Planetary Alignment", to the "Microcosm", or "Atomic Frequency", the cesium now maintains accuracy with a degree of error to about "one-millionth of a second per year"。
Much of modern life has come to depend on such precise measurements of time. The day is long past when we could get by with a timepiece(钟)accurate to the nearest quarter hour. Transportation, financial markets, communication, manufacturing, electric power and many other technologies have become dependent on super-accurate clocks. Scientific research and the demands of modern technology continue re drive our search for ever more accuracy, The next generation of Cesium Time Standards is presently under development at NIST's "Boulder Laboratory" and other laboratories around the world。
Something to Remember
The only thing that should be remembered during all this technological development is that we should never lose the ability to tell the time approximately by natural means and the powers of deduction without requiring crutches(拐杖)to lean on。
Our concept of TIME and using it together with TECHNOLOGY still has room for radical reassessment in terms of man's evolutionary thinking regarding our view of the past, our onward journey into the future and our concept of time in relationship to universe。
1. It is suggested that 5,000-6,000 years ago people in the Middle East and North Africa started to allot specific lengths of time to tasks。
2. Ancient Egyptian "shadow clock" or "sundial" discovered around 1500 BC, could measure passage of "hours" automatically and continuously。
3. "Water clocks" was the first device that didn't use the observation of the celestial bodies to calculate the passage of time。
4. Galileo Galilei built the first "pendulum clock" as early as 1656.
5. Water clocks were mostly used to determine ______。
6. Huygens' clock, a mechanical one, had an error of "less than only one minute a day", which was a massive leap in the development of ______。
7. Since Quartz clocks are both inexpensive to produce in mass scale and ______ in performance, they continue to dominate the market。
8. Scientific research and the ______ continue to drive our search for ever more accuracy in time。
9. Of all the clocks introduced in the passage, the one with the most accuracy is ______。
10. No matter how advanced the technology of measuring time will be we should never lose the ability to tell the time approximately by ______。
上一页 [1] [2] [3] [4] [5] [6] [7] [8] 下一页
