Name: ___________________________________ Date: _______________ Period:____
The Sun-Earth System
Background Information:
Earth revolves around the sun in an elliptical orbit, averaging 107,000 kilometers (66,000miles)
per hour. Its average distance from the sun is 150 million kilometers (93 million miles), but
because its orbit is an ellipse (oval circle), earth’s distance from the sun varies throughout the
year as it revolves around the sun.
The amount of solar radiation received at a particular place depends on two factors:
1) The rotation of Earth on its axis, and revolution around the sun.
2) The fact that Earth is tilted 23.5 on its axis. Consequently, the most direct rays
change positions on a daily basis throughout the year. The change in intensity
(direct rays) and daylight hours produce the seasons.
Solstice refers to the earth having unequal days
and nights. On June 21-22, we celebrate the
summer solstice in the Northern Hemisphere
and the winter solstice in the Southern Hemisphere. This means in June, the Northern
Hemisphere receives energy that is more direct and longer daylight hours than the Southern
Hemisphere. During the summer solstice in the Northern Hemisphere, north of the Arctic
Circle receives 24 hours of daylight, but the rays are at a low angle. The opposite is true on
December 21-22 when the Arctic Circle is in complete darkness with no sunlight.
Equinox refers to equal day and night. All across the globe on March 21 and September 22, the
Earth receives 12 hours of daylight and 12 hours of darkness. The most direct sunlight is
received on the equator on both days. In the Northern Hemisphere, March 21 is called the
vernal equinox and on September 22, it is called the autumnal equinox. The dates would be
reversed for the Southern Hemisphere.
Interpreting Diagrams: Earth-Sun Relationships
Analysis Questions:
1. On the diagram, label the “perihelion” (closest to the sun) and “aphelion” (furthest from the
sun).
2. Analyze the diagram. Describe the direction the Earth travels around its orbit?
3. Besides revolution, what other major movement is the occurring for the planet Earth? What
does this motion cause?
4. Approximately what date will Earth reach it’s perihelion?
Aphelion?
5. What is the difference in kilometers between Earth’s aphelion and perihelion?
6. What is the angle in which Earth rotates on its axis? How long does this take to fully rotate?
7. How long does the Earth’s revolution take to travel around the sun?
8. Why are the dates of January 3rd and July 4th significant?
9. Please estimate the distance from the Earth to the sun during the first day of fall and spring.
10. Do you think the distance from the sun causes Earth’s seasons? Explain why or why not
using evidence to support your claim.
11. In a paragraph, explain thoroughly how the seasons occur. You must be very explicit and
detailed!