What is a Second? - Definition & Explanation

  • Context: High School 
  • Thread starter Thread starter Epsillon
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Discussion Overview

The discussion centers around the definition of a second, exploring its historical context, measurement methods, and the rationale behind its current definition as a unit of time. Participants engage in both conceptual and historical aspects of the topic.

Discussion Character

  • Conceptual clarification
  • Historical

Main Points Raised

  • One participant states that a second is defined as the duration of 9,192,631,770 periods of radiation from the transition between hyperfine levels of the caesium 133 atom.
  • Another participant suggests that the definition is based on a need for a consistent and universally constant measure in nature.
  • There is a question raised about the ability to measure the time it took for radiation or the speed of light before the current definitions were established.
  • A participant mentions that early time measurements were made using pendulums and mechanical clocks, which may have resembled modern grandfather clocks.
  • Reference to historical methods of timekeeping based on the ascension of stars is noted.

Areas of Agreement / Disagreement

Participants express curiosity and share information, but there is no consensus on the historical accuracy of early time measurements or the implications of the definitions provided.

Contextual Notes

Some limitations include the dependence on definitions of time and the historical context of measurement methods, which are not fully resolved in the discussion.

Epsillon
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As the title says what exactly is the defination of a second?

I am very curios about this.
 
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the duration of 9 192 631 770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom

taken from wikipedia. but I remember learning it in physics.

Oh, and its the unit of time...
 
lol why is it that?
 
Well, I guess cause its something consistent that we can measure. They want something that is universally constant in nature.

Its the same with a meter, being defined by distance traveled by light in absolute vacuum in 1⁄299,792,458 of a second.
 
But before could they measure the time it took for the radiation or the speed of light?
 
Well, the first semi-accurate measurement of time came from pendulums. they had second pendumlums and what not. They also had mechanical clocks which showed seconds and minutes and hours like modern clocks. I doubt they were, but they could have beared a resemblance to modern day grandfather clocks. they based there days off of the ascension of stars.

you can read in depth about it here:
http://en.wikipedia.org/wiki/Second#History
 
Thanks :) Interesting article.
 
And the one that you could easily check by yourself before asking...
 

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