Equator and poles based upon Earth’s daily spin projected onto celestial surroundings.
Divisions from equator to North pole are positive numbered lines of latitude to +90 degrees.
Divisions from equator to South pole are negative numbered lines of latitude to -90 degrees.
Divisions from pole to pole across the equator are 24 lines of longitude matching hours of daily rotation with each hour subdivided by 60 arc minutes each of which is subdivided by 60 arc seconds.
Since Earth’s orbit of the Sun is not an even number of days, leap years and leap centuries are necessary to synchronize timing.
Also, since Earth “wobbles” due
to precession in a cycle of approximately 26,000 years, this grid is redrawn
every 50 years (an epoch) to synchronize
with celestial surroundings.
As we explore space, we also use the stars to calibrate the navigation system of the exploring vehicle. Once beyond the view of the planets outside the Solar System, we too will relearn the galactic reference system.
|©2005 Damon Elkins. Image source information here.|