Monday, January 28, 2013

Seasons



Seasons occur because of Earth's changing distance from the Sun





Earth experiences seasons because our planet tilts 23.5° with respect to its orbital plane. During summer Earth's North Pole tilts toward the Sun.
At the same time, however, the South Pole tilts away from the Sun. That means winter is at the southern hemisphere, and summer at the northern hemisphere.


And, regarding distances, Earth is approximately 3 million miles (5 million km) closer to the Sun in early January than it is in early July. That works out to a bit more than a 3 percent swing from Earth's nearest approach to the Sun to its farthest. Although small, 3 percent is not insignificant. The different distances mean the Southern Hemisphere receives more solar energy during its summer than the Northern Hemisphere does in its summer.




Summer and winter occur on dates called the solstices, which mark the highest and lowest points the Sun reaches in our sky. In the Northern Hemisphere, the Sun stands 47° (our planet's 23.5° tilt times two) higher in the sky June 21 than it does December 21. So, around June 21 of each year, summer begins north of the equator, and winter begins south of that line. For this reason, it's incorrect to call June 21 the "summer" solstice. Summer begins on that date only in the Northern Hemisphere. Here at the magazine, we use the terms June solstice and December solstice to signify these dates.

Activity:Match the questions and the answers!

Exercise 1: Quiz

http://www.neok12.com/quiz/SEASON01

Exercise 2: Quiz

http://www.neok12.com/quiz/SEASON02

Exercise 3: Lable the diagram

http://www.neok12.com/diagram/Seasons-01.htm


Exercise 4: Vocabulary practice


http://www.neok12.com/vocabulary/Seasons-01.htm




Were you able to complete all the exercises?
 Do not worry even if you cannot get the correct answer from the first try.
The more you practice the better you become!

Wednesday, January 23, 2013

Movements of the Earth

Movements of the Earth :  Revolution and Rotation of the Earth



The earth revolves around the sun. Besides this it also rotates on its own axis. Thus the earth has two motions, the rotation and the revolution.
Rotation
The earth rotates on its axis from west to east. The axis is an imaginary line passing through the northern and the southern poles of the earth. The rotation of the earth is completed in about 24 hours and it is called the daily motion of the earth. This motion is responsible for the occurrence of day and night.
As a result of the apparent motion of the sun, the appearance of the night sky as seen from the earth changes from day to day. 
Revolution
The movement of the earth around the sun in its orbit is called revolution. This movement of the earth is also from west to east. The period of revolution is one year (365 1/4 days). The orbit of the earth around the sun is elliptical and not circular. 

An interactive animation demonstrating the rotation of the Earth and how day and night arise. Two views are shown, illustrating how a point on the Earth experiences day and night, with the time and sunrise and sunset indicated.

ACTIVITY

Click the following link to see the animation of the moving earth. 

Remember to take the quiz!