{"action":"created","issue":{"url":"https://api.github.com/repos/amusecode/amuse/issues/171","repository_url":"https://api.github.com/repos/amusecode/amuse","labels_url":"https://api.github.com/repos/amusecode/amuse/issues/171/labels{/name}","comments_url":"https://api.github.com/repos/amusecode/amuse/issues/171/comments","events_url":"https://api.github.com/repos/amusecode/amuse/issues/171/events","html_url":"https://github.com/amusecode/amuse/issues/171","id":266402499,"number":171,"title":"Units: use IAU 2009 System of Astronomical Constants?","user":{"login":"rieder","id":954870,"avatar_url":"https://avatars3.githubusercontent.com/u/954870?v=4","gravatar_id":"","url":"https://api.github.com/users/rieder","html_url":"https://github.com/rieder","followers_url":"https://api.github.com/users/rieder/followers","following_url":"https://api.github.com/users/rieder/following{/other_user}","gists_url":"https://api.github.com/users/rieder/gists{/gist_id}","starred_url":"https://api.github.com/users/rieder/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rieder/subscriptions","organizations_url":"https://api.github.com/users/rieder/orgs","repos_url":"https://api.github.com/users/rieder/repos","events_url":"https://api.github.com/users/rieder/events{/privacy}","received_events_url":"https://api.github.com/users/rieder/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"assignees":[],"milestone":null,"comments":1,"created_at":"2017-10-18T08:26:22Z","updated_at":"2017-10-19T03:28:51Z","closed_at":null,"author_association":"MEMBER","body":"Related to #170: \r\nIt's not completely clear what the origin is for the units as defined in units.py. Some (like units.AU) deviate (very slightly) from their definition in the IAU 2009 System of Astronomical Constants (http://maia.usno.navy.mil/NSFA/IAU2009_consts.html), probably because they were defined before this was released?\r\n\r\nAstropy also deviates from these definitions for some units, though not all the same as Amuse...\r\n\r\nI think we should certainly (somewhere) cite the origin of constants and units currently used, and maybe allow the use of a specific definition (i.e. do something like `from amuse.units.iau2009 import constants`)."},"comment":{"url":"https://api.github.com/repos/amusecode/amuse/issues/comments/337789570","html_url":"https://github.com/amusecode/amuse/issues/171#issuecomment-337789570","issue_url":"https://api.github.com/repos/amusecode/amuse/issues/171","id":337789570,"user":{"login":"rieder","id":954870,"avatar_url":"https://avatars3.githubusercontent.com/u/954870?v=4","gravatar_id":"","url":"https://api.github.com/users/rieder","html_url":"https://github.com/rieder","followers_url":"https://api.github.com/users/rieder/followers","following_url":"https://api.github.com/users/rieder/following{/other_user}","gists_url":"https://api.github.com/users/rieder/gists{/gist_id}","starred_url":"https://api.github.com/users/rieder/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/rieder/subscriptions","organizations_url":"https://api.github.com/users/rieder/orgs","repos_url":"https://api.github.com/users/rieder/repos","events_url":"https://api.github.com/users/rieder/events{/privacy}","received_events_url":"https://api.github.com/users/rieder/received_events","type":"User","site_admin":false},"created_at":"2017-10-19T03:28:50Z","updated_at":"2017-10-19T03:28:50Z","author_association":"MEMBER","body":"Just changing constants would be a terrible idea - many simulations would probably be non-reproducible.\r\nBut it would be nice to be able to specify which definition of units is to be used. Many non-SI units may change as they are measured more accurately. These changes will be small, but for full compatibility with e.g. Astropy-based scripts it would be good to be able to use the exact same values for units (and constants).\r\nAnd I think it's important to specify which definition of units we currently have, even if it's just as comments in the units.py file.\r\nI see that constants are taken from http://physics.nist.gov/constants."}}
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