[fitsbits] Output array type when BZERO is an integer {External}

[Barrett, Paul]

Yes, time requires a large number of bits. Current atomic clocks (i.e.,
frequency standards that run 27x7) are accurate to 10 femtoseconds (~1e-14
s). High precision frequency standards are accurate to ~1e-18 s. In the
future, optical and nuclear clocks will be accurate to ~1e-21 s. At this
point clocks cannot be synchronized, because GR makes them their own time
standards. To the point, it will require >30 digits to represent time
accurately. It is possible that optical and nuclear clocks will be
available commercially in about a decade. We might want to prepare for this
situation.

 -- Paul

On Wed, Mar 13, 2024 at 5:43 AM Richard J. Mathar via fitsbits <
fitsbits at listmgr.nrao.edu> wrote:

> rs> Date: Tue, 12 Mar 2024 22:00:49 +0000
> rs> From: "Seaman, Robert Lewis - (rseaman)" <rseaman at arizona.edu>
> rs> To: "Dubois-Felsmann, Gregory P." <gpdf at ipac.caltech.edu>, "Barrett,
> rs>         Paul" <pebarrett at email.gwu.edu>
> rs> Cc: "fitsbits at listmgr.nrao.edu" <fitsbits at listmgr.nrao.edu>
> rs> Subject: Re: [fitsbits] Output array type when BZERO is an integer
> rs>         {External}
> rs> ...
> rs> As a matter of curiosity, do Rubin operations depend on 64-bit
> unsigned integers? What are example use cases for 64-bit integers (signed
> or unsigned) in the community?...
> rs>
>
> It's difficult to imagine that any data taken from a real
> instrument need 64 bits (20 decimal digits), i.e. more than 32 bits.
> ADC's in the MHz range can produce 16bit data (10 decimal digits).
> We can measure temperatures to 0.01K or perhaps better.
>
> The exception are time stamps, if "stamped" by computers
> that can resolve milliseconds reliably and set the origin
> at some arbitrary J2000-alike or MJD references. (But clock synchronization
> is not easy, so in reality only time differences matter to resolve
> GRBs etc...) See https://en.wikipedia.org/wiki/Year_2038_problem .
> Atomic clocks and frequency combs are high-resolution data.
>
> Astronomers are the only group of physics to generate data in FITS
> (photographers/artists use the fact at PNG, TIFF etc also can store
> metadata);
> so that time stamp or 64bit representation has probably not surfaced
> anywhere.
>
> Richard Mathar
>
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