THE SEASONS: Solstices and equinoxes.

The Earth's axis is gently inclined (about 23º) but always points in the same direction (in the direction of the Polar Star, because of that the Axis orientation do not change even though the Earth is rotantig around the Sun but its position in relation to the Sun does.

Inclination of the Earth's Axis.

The seasons of the year.
As a consequence, during different moments of the year the quantity of light and heat that the different parts of the Earth receive from the Sun is going to change during the year:

During summer and winter, the rays of Sun falls directly on one hemisphere while the others reveives them with a strong inclination, making it winter. Nevertheless, during spring and autumn, the rays fall on both hemispheres wiht the same inclination.

When the rays of the Sun are inclined, the same amount of heat is projected onto a larger area, and there is less concentration of heat.

Equinox and solstice.

Equinox: is the time of the year when the Sun's rays falls perpendicular to the Equator. The Sun iluminates the North Pole and the South Pole for the same number of hours. There are two equinox:

1. The spring equinox (March 21), it is spring in the Northern Hemisphere and autumn in the Southern Hemisphere.
2. The autumn equinox (September 21). it is autum in the Southern Hemisphere and spring in the Southern Hemisphere.

Solstice: is the time of the year when the Sun's rays fall perpendicular to one of the tropics.

There are two solstices:

1. The Summer solstice (June 21): the Sun is facing the Tropic of Cancer. It is summer in the Northern Hemisphere and winter in the Southern Hemisphere.
2. The Winter solstice (december 21): the Sun is facing the Tropic of Capricorn. It is summer in the Southern Hemisphere and winter in the Northern Hemisphere.