[LEAPSECS] Reliability

[Rob Seaman]

Tony Finch wrote:


> What do you mean by "stabilized" here? Atomic time is the basis of  

> our most stable time scales. I don't think perturbing a timescale to  

> follow the erratic slow-down of the earth can reasonably be called  

> "stabilizing" it.


Civil timekeeping (the underlying global timescale that ties all our  
local timescales together into a unified whole) has requirements  
derived from two parent classes - interval timekeeping and Earth  
orientation timekeeping.  In the absence of a full blown rubber second  
implementation, the Earth orientation part of that requires tempering  
to optimize (or perhaps more accurately, satisfice) its utility.

(I could venture into a paean to Ernst Mach and point out that to  
flatlanders living on Earth it is the motions of the celestial sphere  
that are erratic, but I will restrain myself :-)

I've been trying on different terms for this tempering, for instance,  
keeping civil timekeeping "stationary" with respect to diurnal  
trends.  One could compare this (loosely) to the notion of  
"disciplining" a clock as in NTP.

The term "stabilization" I borrowed from work I've been doing with  
numerical compression algorithms for scientific imaging data with a  
Poisson noise model, as in the "generalized Anscombe variance  
stabilization" transform.

Precisely because the Earth's motions are erratic, they benefit from  
enforcing a clock discipline that keeps an arbitrary zero point (some  
shrubbery in the park surrounding the Greenwich Observatory)  
stationary in phase through an arbitrary number of cycles.


> What common-sense inferences do you have in mind?


Simple utilitarian inferences regarding the world around us.


> Most common sense is wrong, especially when it comes to time.


Reference to some study supporting this assertion?  Humans make  
decisions based on mental models.  Those models and the resulting  
decisions do not have to be vetted against quantum chromodynamics or  
magneto-hydrodynamics to be deemed "right".  Again, I'll recommend  
Steven Pinker's book "The Stuff of Thought" for a discussion of the  
basis of an inherent model of physics contained in the structure of  
human language.

Rob

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