Re: The transition from heliocentric to the galactic axis

"Oriel36" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> "George Dishman" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> > "Oriel36" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> > > "George Dishman" <[EMAIL PROTECTED]> wrote in message news:<[EMAIL PROTECTED]>...
> > > > "Oriel36" <[EMAIL PROTECTED]> wrote in message news:[EMAIL PROTECTED]
> > > > >
> > > > > to someone else the
> > > > > diagrams in your website look reasonable but unfortunately you place
> > > > > the apical angle at the Sun ...
> > > >
> > > > I had assumed you were familiar with Kepler's Second Law since
> > > > you have brought it up many times. Although the natural days
> > > > vary, in a constant period (say 24h), the line from the Earth
> > > > to the Sun will sweep out a constant area. That area is given
> > > > by (a * r^2)/2 where a is the angle at the Sun and r is the
> > > > radius. (The angle is in radians of course.) Have you ever
> > > > actually used Kepler's Second Law?
> > >
> > > Yes,the Equation of Time reflects Kepler's second law ...
> >
> > I am not asking you about the Equation of Time, I am asking
> > you whether you have ever put Kepler's Second Law in practice.
> >
> > You complained that I "place the apical angle at the Sun".
> > The apex is actually at one focus of the elliptical orbit in
> > Kepler's Law and that lies within the Sun for the Earth/Sun
> > system. It sounds as though you have never used the second
> > law or you would have understood that. I'll happily take you
> > through it if that will help but you need to give me some
> > reason to think that you do understand it. There's little
> > point discussing it otherwise.
>
> The Equation of Time is quite simple, ...

Which part of "I am not asking you about the Equation of Time"
was beyond you? Have you ever calculated Kepler's Second Law?

Gerald, Astronomy involves measuring the stars. The simplest
measurement is to note that any particular star sets about four
minutes earlier each day. That's 12h earlier in a half a year.
You might imagine the Earth is fixed in space and the galaxy
revolves around us.

You can also note that the Sun is high in the sky at noon in the
summer but nearer the horizon at noon in winter (assuming you
live in the northern hemisphere) because of the tilt of the axis.


    summer                      winter
       /*                         */
     (/)          (Sun)          (/)
     /                           /

* = Gerald at noon

That is your clue that the Earth has moved from one side to the
other in half a year. Copernicus put two and two together and
discovered that we orbit _around_ the Sun.

If you want to be an astronomer Gerald, you will have to start
observing for yourself.

George