What is a Second? - Definition & Explanation

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In summary, a second is defined as 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. It is used as a unit of time because it is a consistent and universally constant measurement in nature. The idea of measuring time came from pendulums and mechanical clocks, which were based on the ascension of stars. This concept has evolved over time and is now defined by the distance light travels in 1⁄299,792,458 of a second.
  • #1
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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  • #2
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...
 
  • #3
lol why is it that?
 
  • #4
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.
 
  • #5
But before could they measure the time it took for the radiation or the speed of light?
 
  • #6
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
 
  • #7
Thanks :) Interesting article.
 
  • #8
And the one that you could easily check by yourself before asking...
 

FAQ: What is a Second? - Definition & Explanation

What is a Second?

A second is a unit of time equal to 1/60th of a minute or 1/86,400th of a day. It is the base unit of time in the International System of Units (SI) and is commonly used to measure the duration of events or the intervals between them.

How is a second defined?

A second is currently defined as 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 cesium-133 atom. This definition was adopted in 1967 by the 13th General Conference on Weights and Measures and is the internationally accepted definition of a second.

Can a second be measured with precision?

Yes, a second can be measured with precision using highly accurate atomic clocks that are based on the definition of a second. These clocks can measure time intervals to within a few billionths of a second. However, due to variations in the Earth's rotation, the length of a day can vary slightly, resulting in occasional adjustments to atomic timekeeping systems.

What are some common everyday examples of a second?

Some common examples of a second include a heart beat, a blink of an eye, a snap of fingers, and a tick of a clock. It is also used to measure the duration of activities such as cooking, exercising, and watching TV.

How is a second related to other units of time?

A second is a smaller unit of time than a minute, hour, day, week, month, and year. It is also equal to 1/60th of a minute, 1/3,600th of an hour, and 1/31,536,000th of a year. It is often used in combination with other units of time to measure longer periods, such as hours and minutes.

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