What is a "unit of time"?

JeffDG

JeffDG

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JeffDG
Header said:
9.852435E-18 units of time remaining until the 6Y9 Fly-In!
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0.000000000000000009852435 of something is pretty small...
 
JeffDG said:
0.000000000000000009852435 of something is pretty small...
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Well that is relative!

If it was 0.000000000000000009852435 of the universe that could still be immense! What is infinity divided by 0.000000000000000009852435 ??


:rofl::rofl:

But to answer the question what is the basic unit of time? On this planet that would be the second. According to NIST:

[FONT=Myriad Roman,Syntax,Gill,Gill Sans,Arial,Helvetica]The unit of time, the second, was defined originally as the fraction 1/86 400 of the mean solar day. The exact definition of "mean solar day" was left to astronomical theories. However, measurement showed that irregularities in the rotation of the Earth could not be taken into account by the theory and have the effect that this definition does not allow the required accuracy to be achieved. In order to define the unit of time more precisely, the 11th CGPM (1960) adopted a definition given by the International Astronomical Union which was based on the tropical year. Experimental work had, however, already shown that an atomic standard of time-interval, based on a transition between two energy levels of an atom or a molecule, could be realized and reproduced much more precisely. Considering that a very precise definition of the unit of time is indispensable for the International System, the 13th CGPM (1967) decided to replace the definition of the second by the following (affirmed by the CIPM in 1997 that this definition refers to a cesium atom in its ground state at a temperature of 0 K): [/FONT]
  • [FONT=Myriad Roman,Syntax,Gill,Gill Sans,Arial,Helvetica]The second is 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.
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  • [/FONT]


    [FONT=Myriad Roman,Syntax,Gill,Gill Sans,Arial,Helvetica]http://physics.nist.gov/cuu/Units/second.html
    [/FONT]
 
Last edited:
ScottM said:
Well that is relative!

If it was 0.000000000000000009852435 of the universe that could still be immense! What is infinity divided by 0.000000000000000009852435 ??


:rofl::rofl:
Click to expand...

True...

The best candidate for a universal unit of time would probably be Planck's Time (the time it takes light to travel Planck's Length or ~10^-44s), and 10^-18 of that is incredibly small (10^-62 s)
 
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