What Causes Day and Night

Before we discuss what causes day and night lets discuss some facts about our earth. Our earth is a spherical planet. The scientists have made many imaginary horizontal and vertical lines on the planet. The horizontal lines are called as latitudes. The vertical lines passing across the surface are called as longitudes. Equator is the imaginary horizontal line that passes across the center of the earth and divided it into two hemispheres.

The upper part is northern hemisphere and the part below the equator is the southern hemisphere. The earth is rotating and revolving continuously. It is the rotation of the earth on its axis that cause day and night. To study the planet more accurately the scientists have invented an imaginary line passing through North and south poles.

This imaginary line is called the axis the scientist say that the earth takes twenty four hours to complete one rotation on its axis. While the earth rotates one part faces the sun. This part facing the sun gets the light and hence the region coming in this part have day. The other part is in the black away from the sunlight and hence this is the part where there is night.

The earth thus takes one whole day to complete one round on its axis. Thus after every twelve hours we have day or night; whatever way you want to say it. As the earth spins on its axis it seems that the sun is moving and causing day and night. But this is not so. Sun is constant and it is the earth that is moving. The movement is form west to east and this is the reason why the sun seems to rise in the east and set in the west.

As the earth is a spherical planet hence there are some places which have few days and night every twenty four hours. As our earth rotates on its axis it also revolves around the sun on an elliptical path. To complete one revolution it takes 365 and one fourth day. The earth is also tilted on its axis at an angle of 23.5 degrees. Thus are the earth is moving around the sun it is always pointing on one side.

This is the reason why we have different seasons. When the axis is pointing towards the sun then there is summer in that hemisphere. When it is pointing away from the sun then it is winter in that hemisphere.

The angle at which the sun rays hit the earth causes the variation in temperatures during the seasons. During summers the earth is farthest from the sun and during winter it is closest to the sun. But during summers the sun ray hit the earth at steep angle. This causes high temperature during summers. The reverse happens in winters.