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Subject: Re: Fwd: Re: [office-formula] Straw poll - slug (and lightyear)
"David A. Wheeler" <dwheeler@dwheeler.com> wrote on 04/06/2010 05:33:46 PM: > > WARNING: Technical nitpick ahead: > The distance light travels in a year, in a vacuum, *is* exact; the > meter is actually defined > in terms of speed of light in a vacuum. And while an Earth year > isn't exactly 365.25 days, for purposes of a > light-year, that's the exact value of the "year". It's not well- > documented, but astronomers > use this "standard year approximation" of 365.25 days when stating > light-years. > And since a day is exactly 24*60*60 seconds, this has an exact value. > I actually had to track that down, and I'm pretty sure I posted my citations > (though I can't remember where they are right now). If anyone knows > differently, > please let us know now. That matches the International Astronomical Union's definition as well, only they say as distance light travels in a vacuum in 1 Julian Year, which is 365.25 days. On the other hand, the IAU says Pluto is not a planet, so I don't know if we can trust them anymore. -Rob
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