Re: Yes, I'm back
| From: | James Landau <neurotico@...> |
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| Date: | Monday, January 20, 2003, 19:42 |
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In a message dated 1/19/2003 7:37:43 PM Pacific Standard Time,
himes@CSHORE.COM writes:
> James Landau <Neurotico@...> wrote:
> > I've usually seen [the date of Jesus' birth] given as "4 B.C.". (If you
> > can think of any other way to express the would-be year 0 that marked the
> > transition from B.C. to A.D., tell me). Of course there had to be some
> > significance to "0" too, or else why would anyone have started there if
> > they knew he wasn't born at that point?
>
> There is no year 0 in the BC/AD system. 1 AD is the year following
> 1 BC.
Which is exactly why I called the transition to A.D. "the would-be year 0".
> > Well, when I say a "day", I mean the amount of time it takes for Kankonia
> > to complete one full rotation on its axis.
>
> Not the time from noon to noon? They're not the same. Earth completes
> a full rotation in about 23 hours and 56 minutes.
It does? I guess I'll have to divide from when they can see the sun without
leaving the planet then; it's unlikely that a people who were first measuring
days would already be able to measure rotations and they wouldn't see
themselves moving. (they might not even understand that their planet revolves
around the sun -- the Terrans sure didn't, with the persecution of Galileo,
myths about the sun disappearing because some dragon swallowed it, languages
talking about the sun "rising" and "setting", etc.) It sounds like the little
bit of "displacement" every day would be necessary for the planet to move.
> > (This leads to another question: is there anyone here who knows how to
> > find out how fast a planet will rotate on its axis or complete a year,
> > given its volume, mass and distance from the sun?)
>
> See the Planet Designer at
>
http://www.compulink.co.uk/~vicarage/planets/index.html. I believe the
> speed of rotation is only constrained by not being fast enough to tear the
> planet apart, but the length of year is dependent on the distance from the
> sun and the mass of the sun.