astropy/astropy — pull request #21 by astrofrog (2011-10-15 16:57:28+00:00)
Title: Constants

**Note:** this module is not ready for merging. I am opening this pull request so that we can review the current code and iterate on it first (with the ultimate goal of merging).

A few notes:

* I decided to always use ``_`` for subscripts and to use lowercase and uppercase as is usually conventional - but we can also switch to all lowercase if you think that would be best

* I decided to spell out sun, jup, and earth to avoid a possible conflict between electron mass and earth mass (let me know if you have a better idea!).

* The S.I. constants re-use the values from the cgs module so that we only need to change constants in one place.

* There are no tests yet, as I'm not sure what tests would consist of in the case of constants. Maybe we can check for example that a certain dimensionless combination of constants in cgs is equal to that in S.I. (which would test the c.g.s to S.I conversion).

* I need to double check the constants values, and we'll need several other people to vet them, since this is obviously very important to get right.