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The Earth and the Sun

The Earth's Orbit -
The First Great Misconception
The Seasons -
A Popular Misconception
The Seasons - Sunrise and Sunset The Seasons - Solstices and Equinoxes The Seasons - Understood!
The Sun Tracker & Other Activities

The Seasons - Understood!
References: [Arny 2002, Robbins & Jefferys 2003]

The discussions in this section on the Earth and the Sun have (hopefully) demonstrated the truth about how the relative positions of the Earth and Sun throughout the Earth's orbit determine the four seasons - spring, summer, autumn and winter.
  • The Earth's 23.5 degree tilt with respect to the orbital or ecliptic plane causes the Sun to rise higher in the sky during the summer months and lower in the winter months. The Sun's height in turn determines how directly the Sun's rays heat the Earth as well as how long the Sun remains above the horizon on each day. More direct heating and longer daylight hours produce the warm summer temperatures, while less direct heating and shorter daylight hours result in colder winter temperatures.

  • Seasonal effects are experienced in both the Northern Hemisphere and the Southern Hemisphere, but in an "inverted" manner. First, when it is summer in the NH it is winter in the SH, and vice versa. Secondly, while in the NH the Sun is observed each day moving through the southern sky from East to West, while in the Southern Hemisphere the Sun moves through the northern sky from East to West.

  • The Sun's position and path also mark the turning points of the four seasons. The spring and autumnal equinoxes correspond to the two days on which the Sun is positioned directly over the equator and is observed to rise directly in the Eastern sky, resulting in exactly the same amount of daylight and nighttime everywhere on Earth. Between the equinoxes the Sun's rising position in the sky is observed as either gradually moving north or south of East depending upon the hemisphere and the season. The summer and winter solstices correspond to those days on which the rising Sun "stops" its gradual move and reverses direction toward its eastern rising position.

Additional Online Activities

Check Out the Sun Tracker!

The SunTracker is a really nifty simulation that allows you to "observe" the Sun's path as seen from any location on Earth by entering its longitude and latitude and choosing a day of the year! (The simulation is accessed by clicking on the black screen image on the right of the window.) Enter a latitude and longitude or press the "Choose location" button to access a map of the globe, and click the mouse anywhere on the map to return its latitude and longitude. Press "Done" to return to the SunTracker. Press the "Show Sun's movement" and observe how the Sun rises over the hill on the left and sets amongst the trees on the right. Pay attention to the Sun's height in the sky and how the daylight changes as the clock in the upper left marks the hours of the day. This simulation is most useful when comparing "extreme" locations like the poles and the equator, or opposite latitudes in the Northern and Southern hemispheres.

The Sun's Path at the Equator and Poles

Use the USNO Sun or Moon Altitude/Azimuth Table to investigate the Sun's path along the equator (0 degrees latitude) or the poles (90 degrees North or South latitude), or any other location of interest to you. Use "Form B - Locations Worldwide" and enter the longitude and latitude of interest. Make sure to specify east or west longitude and north or south latitude. (Note that although this form allows for city or place names to be entered, not all names and cities will be recognized so you may get nonsensical results.) Enter "0" for the "Time Zone" field to insure that information is returned for each location from 0:00 to 24:00 hours local time.

The Seasons in Ancient Times

Today we have the local TV weatherman and gift calendars to tell remind us when the first day of each season falls, but how did they mark in the seasons in ancient times? For example, how would an ancient observer recognize an equinox as the day on which all points of Earth shared equal day and night? The answer of course is that ancient peoples used the solstices to mark their calendars, because they could see over a period of time how the Sunís path would move northward or southward and then stop and begin to move in the other direction.

These three photos taken in Florida at the top of this webpage from the "Paper Plate Astronomy" website demonstrate how the Sun's position along the horizon changes from solstices to the equinoxes. (Click on each to enlarge.) Note how the two tower-like buildings mark the equinox or East rising position (middle picture) with the summer solstice (first picture) and winter solstice (third picture) indicating the furthest Northeast and Southeast rising positions, respectively.

Itís this very idea of marking the Sunís position in the sky with a permanent building or other edifice that is believed to be the purpose of Englandís famous Stonehenge monument as well as the purpose behind ancient buildings in Egypt and South America. Check out the websites below to learn more about how the ancient cultures marked the seasons of the year, and how important edifices were built to be aligned with key solar positions.


The Earth's Orbit -
The First Great Misconception
The Seasons -
A Popular Misconception
The Seasons - Sunrise and Sunset
The Seasons - Solstices and Equinoxes The Seasons - Understood!
The Sun Tracker & Other Activities



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