The effects of revolution include are;

• Varying lengths of day and night.
• Changing attitude of the midday sun.
• Changes in season.

• Varying Lengths of Day and Night

Due to the inclination of the earth’s axis, there are changes in the length of days and nights time during the year.

On the 21^st of June the sun is directly on the tropic of cancer in the North Pole at midday. During this period, the length of day light increases as latitude increases. In the south, length of day decreases because the sun does no rise there. This period is called summer solstice.

On March 21^st and September 23^rd at noon, the sun is directly on the equator. During this time, the earth has equal hours of daylight and equal hours of darkness. This period is called Equinox (equal days and nights.)

On the 22^nd of December, the sun is directly on the tropic of Capricorn. This is called winter solstice. During this period, the length of day light in the southern hemisphere increases as latitude increases. In the Northern hemisphere there is darkness.

• Changing Altitude of the Midday Sun

As a result of the earth’s inclination, there are changes in the altitude of the midday sun on the 21^st of June at midday; the sun is directly on the tropic of cancer in the North Pole.

 On the 23^rd of September, the sun is on the equator at midday.

On the 22^nd of December, the sun is on the tropic of Capricorn at midday.

• Changes in Season

Changes in the length of day and night time and the altitude of the midday sun cause a rise and fall in temperature during the year. The period of the year, when temperature rises is called summer while the period when temperature falls is called winter.

In summer, temperature increases the weather is bright and days are longer than nights. From the 23^rd of June to the 23^rd of September, it is summer in the Northern hemisphere. In Cameroon, it is the warm rainy season. The north is directly under the sun.

In winter, from the 22^nd December to 21^st March temperature falls and places are colder. During this time, nights are longer than days and less heat are received. In Cameroon, it is the cold dry season.

From the 23^rd of September to the 23^rd of December, it is autumn in the Northern hemisphere.

Spring season begins from the 21^st of March to 21^st June in the Southern hemisphere. During this period, nights and days are equal.

DAWN AND TWILIGHT

Dawn is a brief period between sunrise and full day.

Twilight is the period between sunset and complete darkness.