Aaah she wondered. The big Jovian has two moons
revolving in opposite directions. Life? he quipped

Concept 1.14 : A Rotation about the Solar system
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Idea:
=====
To draw a sun, the first five planets and 
moons (one for the earth, two for jupiter)
Use the left mouse button to click anywhere
in the rendering window to start our solar system.
Approach
========
Draw the sun at the origin, and then use the
modelling transformations to position and
render the planets and the moons.

Details for drawing mercury & earth with moon
=============================================
Command				Action Taken
-------				------------
glutSolidSphere(1.75,30,30);	Draw the sun
glPushMatrix();			Remember my position
glRotatef(myear, 0, 1.0, 0.0);	Find the direction of
				mercury
glTranslatef(2.75, 0, 0);	Go 2.75 units along the
				direction of mercury
glRotatef(mday, 0.0, 1.0, 1.0);	Rotate mercury about its
				axis by mday degrees
glutSolidSphere(0.5, 20, 20);	Draw a sphere for mercury
glPopMatrix();			Go back to where I came
				from i.e position of the sun.

The earth is drawn in a similar fashion.  To draw the moon
we memorize the position of the earth, rotate the moon, 
translate to the position of the moon draw the moon and 
then return to the position of the earth.  

The revolve() function which starts the animation merely
updates the values for the rotations values of various 
planets and moons.  It is much like the spinDisplay() 
routine we saw in Concept1.13

There is a mouse routine and a keyboard routine.  The 
keyboard routine allows the user to toggle between 
wireframe mode and filled polygon mode (by pressing 
the w key)