New definition for the second

[dlangane]

I know what is the current definiton for one second but I just can't understand how can scientists change the definiton to a "better one".
Therefore my question is how the currently used definition cannot be the most accurate one?
Thank you for your time and help!

[swansont]

There is a difference between defining a quantity and realizing it in a measurement. You could define the length of the second in terms of a length of a pendulum and a value for g, and the definition could be as exact as you want, but actually building a pendulum and measuring the length, as a basis of comparison for other timekeeping devices would leave you with a relatively imprecise standard — there's a limit to how well the measurement can do.

Modern frequency standards have to assess their uncertainty for things like external electric and magnetic fields, the blackbody shift from being bathed in thermal radiation, AC Stark shift from other light, how well you know the speed of your atoms because there will be time dilation effects, collision effects, and errors from how the microwave cavities are built. All of these things represent shifts in the frequency of the Cs transition relative to the definition.

Redefining the standard makes sense if you can make those errors/uncertainties significantly smaller.

[geordief]

Is there any time interval associated with virtual particles?

 

Otherwise what is the shortest theoretical (layman's terminology, I think) interval between two well defined events or occurrences that might be used as a basis for measuring time

[scherado]

1 hour ago, dlangane said:

I know what is the current definiton for one second but I just can't understand how can scientists change the definiton to a "better one".
Therefore my question is how the currently used definition cannot be the most accurate one?

I don't understand this. Can you explain how the "definition" of "one second" is being changed? Please keep in mind that it is a duration.

[swansont]

9 minutes ago, scherado said:

I don't understand this. Can you explain how the "definition" of "one second" is being changed? Please keep in mind that it is a duration.

People are discussing changing the definition based on a Cesium microwave transition to an optical transition in a yet-to-be-determined atom or ion. There are a lot of candidates at the moment. It's not obvious to me that there is a clear front-runner.

 

[scherado]

1 hour ago, swansont said:

People are discussing changing the definition based on a Cesium microwave transition to an optical transition in a yet-to-be-determined atom or ion. There are a lot of candidates at the moment. It's not obvious to me that there is a clear front-runner.

From your answer, one might infer that the duration remains the same? Am I correct?

1 hour ago, geordief said:

two well defined events or occurrences

Earth's rotation; Earth's revolution.

Will someone name another two?

[Janus]

1 hour ago, scherado said:

From your answer, one might infer that the duration remains the same? Am I correct?

Earth's rotation; Earth's revolution.

Will someone name another two?

Neither of these are unchanging.  The Earth's rotation is constantly slowing and can even be effected by major earthquakes.  The Earth's orbit also slowly evolves.  While at one time both of these were used as the basis for the definition of the second, they were abandoned in favor for a non-changing standard.

[J.C.MacSwell]

6 hours ago, scherado said:

From your answer, one might infer that the duration remains the same? Am I correct?

 

That would be the intent

[swansont]

7 hours ago, scherado said:

From your answer, one might infer that the duration remains the same? Am I correct?

It seems likely that the length of the second would not be changed.

Your choice of vocabulary suggests you wish to grind your axe. Please don't.