[AstroPy] Wrong earth mass in astropy.constants

Demitri Muna demitri.muna at gmail.com
Mon Nov 28 10:56:20 EST 2016


On Nov 28, 2016, at 10:44 AM, Thomas Robitaille <thomas.robitaille at gmail.com> wrote:

> The main problem we are facing in Astropy is that if we update constants from one release to the next, results might then change, which might not be acceptable for some users. Therefore, we need to make sure we have a mechanism for users to import a 'fixed/frozen' version of constants that will not change in future releases of Astropy, and this is why there are delays currently in updating some of the constants.

Taking the devil's advocate position-

1) Those that are worried about things like the Earth’s mass to the precision of the edge of current research (or similar constants) probably are putting in their own value and not relying on a library. That seems like the right thing to do in that case.

2) While a tiny of change of a constant at the most precise level would change a person's calculation from one release to another, they should be checking equivalence to a certain precision, not an exact value when using constants like these.

I would argue for always adopting the most current "trusted" value (where "trusted" can be defined as JPL, IAU, etc.). Changes in a user's output because of changes in constants like these is a reflection of a bad software test, not the library.


Demitri Muna

Center for Cosmology and AstroParticle Physics
& Department of Astronomy
Le Ohio State University

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