[SciPy-Dev] Updating constants

[Vincent Davis]

On Fri, Jun 11, 2010 at 12:55 PM, Charles R Harris
<charlesr.harris at gmail.com> wrote:
>
>
> 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.

Thats what I was thinking. I could add an additional item to the list
stored values, "notes", [value, precision, units, notes] and add a
helper function like the others have ie codata.notes(Loschmidt) =
(273.15 K, 101.325 kPa)

Does that sound ok?

Vincent


>
> Chuck
>
>
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