Re: [Celestia-developers] Conversion error

[Christophe T. <ch...@te...>]

Isn't the reference for a light year the julian year rather than the tropic=
al=20
or sideral?

In any case that's what Wikipedia and my units.dat file say.

1 ly =3D 365.25 * 86,400 * 299,792,458 =3D 9,460,730,472,580,800 m



Le Samedi 26 Mars 2005 00:29, Fridger Schrempp a =E9crit=A0:
> Chris,
>
> just for comparison, here are my values that are extracted from our
> professional, global data base for particle & astroparticle physics:
> http://www-theory.lbl.gov/
>
> They largely refer to the Astronomical Almanac.
>
> The speed of light is unanimously: 299 792 458 [km/sec]
> One has to contemplate, however, how many sec's the year has in Celestia:
>
> The year 2005.0 according to the above source has
>
> tropical: 31 556 925.2 sec (equinox to equinox)
> sideral : 31 558 149.8 sec (fixed star to fixed star)
>
> The product gives for the light year in [km]
>
> tropical: 9460528172630.0 km
> sideral : 9460895298470.0 km
>
> So make your choice, please... ;-)
>
> Bye Fridger
>
> Chris Laurel wrote:
> > Fridger,
> >
> > If it's true that there's an error in the conversion, I'll change it.
> > Since there are some other changes that will break some cel: URLs in
> > 1.4.0, this is the right time to make a correction.
> >
> > --Chris
> >
> >>just in case you overlooked the recent forum post (2 days ago!)  by the
> >>user 'tlittle' in Celestia Bugs. I think he is right! Celestia's
> >>conversion of 1 light year into km is significantly incorrect and
> >>probably due to a simple typo (one 9 too many ;-)). I checked all my
> >>scientific resources. They agree with 'tlittle's value. [At first, it is
> >>a little tricky, since there are various differing definitions of '1
> >>year' in astronomy, and thus of the number of seconds /year.]
> >>
> >>The correct revision of this value may have quite some interesting
> >>implications for our precision predictions, like various 'mutual' events
> >>etc.
> >>
> >>I am going to look into it in more detail.
> >>
> >>Bye Fridger
> >>
> >>
> >>
> >>
> >>
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