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Subject: RE: [office-formula] Straw poll - slug (and lightyear)
Here is another reference that may be quite valuable in this context, <http://physics.nist.gov/cuu/Constants/index.html>. Although the only one that crosses over to anything material, here, is the speed of light in a vacuum, there is this interesting assumption that it is exact (whereas it is only exact because of the way the meter and second are standardized as SI units) and that it is a non-SI unit. With regards to actual measurements, the way that uncertainties and relative uncertainties are carried is very useful. Also, exact here is not meant as exactly-known, but exact by definition (see for example, how the standard acceleration of gravity is described), so when the speed of light in a vacuum is described as exact, they do not mean the speed of light is exactly known as something that has been exactly measured in some independent way. -----Original Message----- From: Dennis E. Hamilton [mailto:dennis.hamilton@acm.org] Sent: Friday, April 09, 2010 11:33 To: robert_weir@us.ibm.com Cc: office-formula@lists.oasis-open.org Subject: RE: [office-formula] Straw poll - slug (and lightyear) +1 I think the SI folks have done what they can with regard to how the standard measures have been arrived at. Of course, if one determines the distance light travels in one second just a little bit more accurately, we may find that the standard meter is a bit off and we have no idea what will happen then. Odds are the increase in accuracy will not contradict the value previously in use, simply have it be more accurate but within the measurement tolerance of the previous estimate. What it looks like we should do is rely on the standard base units and then use the *defined* relationships among the base units (see 4.1 in the BIPM brochure that David Wheeler cites). We should not make up derived conversions but only specify the fixed relationships (e.g., 1 foot = 12 inches) that have been set and the inter-unit ones that have been fixed by authorities (e.g., meters in feet). Any intermediate calculations should not be supplied or simplified by us. - Dennis -----Original Message----- From: robert_weir@us.ibm.com [mailto:robert_weir@us.ibm.com] Sent: Friday, April 09, 2010 08:36 To: office-formula@lists.oasis-open.org Subject: Re: [office-formula] Straw poll - slug (and lightyear) > > PS: I can also insert more exact measurements for Astronomical Unit, > Parsec and Megaparsec if anyone is interested. > Table 5 here: http://www.iau.org/science/publications/proceedings_rules/units/ This is cited from "IAU Style Manual" by G.A. Wilkins, Comm. 5, in IAU Transactions XXB (1989) But the problem will be that some units, like the astronomical unit (au) are known only empirically. So a new scientific paper can come out tomorrow and change the value at the 8th decimal place. So do we mandate a specific value, based on the latest determinations? Or leave it floating? Treat it like a registry? From a end-user perspective, I think I'd expect to use the latest values. -Rob. --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. Follow this link to all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php --------------------------------------------------------------------- To unsubscribe from this mail list, you must leave the OASIS TC that generates this mail. Follow this link to all your TCs in OASIS at: https://www.oasis-open.org/apps/org/workgroup/portal/my_workgroups.php
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