The Sun's path

This applet models the Sun's path in a geocentric view, it calculates and visualizes the position of the Sun based on the latitude and the time. It allows to simulate the Sun's position and path during an hour, a day, a month and a year.

For a more precise calculation of the Sun's position, more data are needed that the program does not use, for example longitude, time zone, daylight savings time and the year.

The program simplifies the calculations and uses the average interval between two successive crossings of the Sun over the same meridian. The calculations are referred to the center of the solar disk.

There are some other data to keep in mind for a better compriention of the Sun's path.  

• The Sun is much bigger than the Earth - about 330,000 times its mass - but appears relatively small in the sky because it is so far away - about 149,600,000 kilometers on the average.
 
• The Earth average speed of revolution around the Sun is 29.8 kilometers per second, and it makes one complete revolution in 365.242199 days.
 
• The Earth spins on its axis and completes one rotation in 23 hours 56 minutes and 4 seconds; this is a sideral day and is slightly different from the familiar 24 hour day.
 
• If you are looking at the times of sunrise and sunset as calculated in the applet, some consideration for a correct understanding are necessary:
 
• The Sun is not a point, it takes about two minutes to move over the horizon at the sunrise and below it at sunset.
 
• The light rays are bent by a process known as refraction as they propagate through the atmosphere.
 
• In any case sunrise is defined as that istant when the tip of the Sun appears on the sea-level horizon and sun set is defined as the instant when the upper tip of the Sun disappears below the sea-level horizon.

   The Cover

   The SunPath User's Guide.

   The Solar Irradiation.

   Educational Bookmarks.

This page was updated: 3 december 2002