[time-nuts] time-nuts Digest, Vol 61, Issue 77

Lux, Jim (337C) james.p.lux at jpl.nasa.gov
Wed Aug 19 22:06:21 UTC 2009


> -----Original Message-----
> From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
> Behalf Of Jean-Louis Oneto
> Sent: Wednesday, August 19, 2009 2:42 PM
> To: Discussion of precise time and frequency measurement
> Subject: Re: [time-nuts] time-nuts Digest, Vol 61, Issue 77
> 
> I also remember that one of Digital Equipment Corp. (DEC) VMS Operating
> System was defined in microfortnight...
> 
> ----- Original Message -----
> From: "Mark Sims" <holrum at hotmail.com>
> To: <time-nuts at febo.com>
> Sent: Wednesday, August 19, 2009 8:18 PM
> Subject: Re: [time-nuts] time-nuts Digest, Vol 61, Issue 77
> 
> 
> >
> > Alas, yes,  the RCH is no longer politically correct.   It's slightly
> more
> > acceptable cousin is now the RPH.
> >
> > I have a friend that does monomolecular / monoatomic layers.  His
> > definition of a thin film is a gnats ass spread over the Rockies...

Hmm.  50 microns (=1 GA) out of 5000 meters (Height of Rockies) is 10 ppb.
A monolayer of oil on water is on the order of 1 wavelength of light (0.5 micron = 10 mGA), but that's a very thick layer as thin films go.
Let's look at the layer of aluminum on a crystal. I think these are in the few tens of nm range (usually given as hundreds of Angstrom), and are deposited on a slice of quartz a few mm thick (I think.. others on this list know a LOT more about this than I do), or roughly 1 ppm thickness.

But, to relate to our GPS timing question, what should the basis be? Orbital semidiameter of the satellites? Radius of Earth? A wavelength of the carrier frequency?




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