[SciPy-Dev] Updating constants

[Charles R Harris]

On Fri, Jun 11, 2010 at 12:46 PM, Vincent Davis <vincent at vincentdavis.net>wrote:

> On Thu, Jun 10, 2010 at 11:29 PM,  <josef.pktd at gmail.com> wrote:
> > On Fri, Jun 11, 2010 at 1:09 AM, Vincent Davis <vincent at vincentdavis.net>
> wrote:
> >> On Thu, Jun 10, 2010 at 10:54 PM, Vincent Davis
> >> <vincent at vincentdavis.net> wrote:
> >>> On Thu, Jun 10, 2010 at 10:38 PM,  <josef.pktd at gmail.com> wrote:
> >>>> On Fri, Jun 11, 2010 at 12:11 AM, Vincent Davis
> >>>> <vincent at vincentdavis.net> wrote:
> >>>>> The current constants in scipy are from 2002, the newest set
> available
> >>>>> are from 2006.
> >>>>> Should they be updated, What are the issues with updating with regard
> >>>>> to notifying users ie documenting the update.
> >>>>
> >>>> I thought these are constants. Did they change the value of Pi
> recently?
> >>>
> >>> They found more digits of Pi :)
> >>> I was referring to "Fundamental Physical Constants"
> scipy.constants.codata
> >>> I don't know, it's not easy to compare. I assume there was a reason
> >>> they updated the list. There is an Uncertainty value on many of them
> >>> so I assume the actual value don't change but our estimate does.
> >>>
> >>> http://physics.nist.gov/cuu/Constants/index.html
> >>> release dates 1986, 1998, 2002, 2006
> >>>
> >>> Vincent
> >>>
> >>>>
> >>>> just curious: What has changed?
> >>>>
> >>
> >> I just relived I can update the constants and then compare them with
> >> the old. Should be quick, I will send out the diff in the morning.
> >
> > quote from the REVIEWS OF MODERN PHYSICS paper:
> >
> > "Although just four years separate the 31 December closing dates of
> > the 2002 and 2006 adjustments, there are a number of important new
> > results to consider. Experimental advances include the 2003 Atomic
> > Mass Evaluation from the Atomic Mass Data Center (AMDC),which provides
> > new values for the relative atomic masses Ar(X) of a number of
> > relevant atoms; a new value of ..."
>
> Ok a few more issues/question about constants.codata.
> Some of the names seem rather messed up because of how the raw text is
>  read. For example
> Loschmidt constant (273.15 K, 101.325 kPa)             2.686 7774 e25
>      0.000 0047 e25        m^-3
>
> The above line gets added to the physical_constants dict with the key
> value 'Loschmidt constant (273.15 K, 101.325 kPa)'.
> codata.value('Loschmidt constant (273.15 K, 101.325 kPa)')
> 2.6867773000000001e+25
>
> Seems like it should be no more that 'Loschmidt constant' and I would
> recommend 'Loschmidt' unless there is a conflict.
>
>
The new codata will need a bit of editing to work, for examples the columns
used to extract the various parts will need modification. I think "Loschmidt
constant" is the right name to use, but this "constant" depends on
temperature and pressure, so that should be noted somewhere, maybe in the
documentation.

Chuck
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