On 22^nd December, the Tropic of Capricorn receives direct sunrays due to the tilt of South Pole towards it. As the sunrays are vertical on it, hence it has summers. Therefore, Christmas which falls on 25^th December is celebrated in summers in the Southern hemisphere.

On September 22^nd or 23^rd in the Northern Hemisphere, night and day are nearly of the same length as the Sun crosses the Equator, moving southwards. And in the Southern Hemisphere on 20^th or 21^st March, the Sun crosses the Equator, moving northwards it is known as Autumn Equinox.

The shadows are long in the morning and evening and shorter at noon. It is the effect of the slanting and direct rays of the Sun. When the rays of the Sun are overhead in afternoon, shadows are the shortest. The rays of the Sun are slanting during evening and morning hence, the shadows are longer.

The sunrays at noon are the hottest in comparison to the sunrays of the morning and evening. This is because the rays of the Sun are almost vertical at noon. They fall over a small area and hence, give a greater amount of heat that means the heat received at per unit area increase. The rays of the Sun are slanting in the morning and in the evening. They spread over a wider area and hence, they cover larger area but give less amount of heat. That is why, it is hotter when the sunrays are vertical at a place.

The portion of the Earth facing the Sun would always experience day, thus bringing continuous warmth to the region. The other half would remain in darkness and would be freezing cold all the time. Life would not have been possible in such extreme conditions.

The change of seasons is caused due to the revolution of the Earth around the Sun.

Norway is known as the Land of Midnight Sun because:
(i) The Sun does not go below the horizon or come above it on 21^st June.
(ii) The Sun moves at a long elevation from horizon to horizon. Although the attitude is very low, it continues shining longer for all the 24 hours.

The change in seasons is caused due to :
(i) The rotation of the Earth,
(ii) Inclination of the Earth's axis,
(iii) The revolution of the Earth, and
(iv) The parallelism of the Earth's axis

The circle of illumination does not coincide with the axis of the Earth because of the inclination of the axis by 23 1/2°. The circle of illumination divides day from night and the Earth takes 24 hours to complete one rotation around its axis.

On 21st June, the Northern hemisphere is tilted towards the sun. These areas receive more heat because sun rays fall directly on the tropic of Cancer. As the larger portion of Northern hemisphere gets light from the sun, it is summer in the Northern part of equator.

The movement of the Earth on its axis around the sun takes 365 days (one year) and 6 hours to revolve once around the sun. We ignore six hours for the sake of convenience and consider a year consisting of 365 days. Saved six hours are added to make one day (24 hours) over span of four years.
This surplus day is added to the month of February and in every fourth year, February is of 29 days in spite of 28 days.

The North Pole remains inclined towards the sun for six months due to which places beyond the Arctic circle experience continuous daylight for about six months while South Pole remains away from the sun for six months and experiences night for same period. The same condition reverses for the next six months when South Pole inclines towards the sun and experiences day while North Pole experiences night

On 21st March and 23rd September, the whole Earth experiences equal days and equal nights because neither of the poles is tilted towards the sun and the equator receives direct sun rays, this is called an equinox.

Summer Solstice The days are longer with shorter nights in Northern hemisphere in summer while the conditions are reversed in the Southern hemisphere. This position of the Earth is called the summer solstice.
Winter Solstice The Southern hemisphere experiences summer and it is winter in Northern hemisphere. The days are longer with shorter night in Southern Hemisphere. This position of the Earth is called the winter solstice.

Rotation is the movement of the Earth on its axis, while the movement of the Earth around the sun in an orbit (fixed path) is called revolution (second type of motion of the Earth). It takes 365 days (one year) and 6 hours to revolve once around the sun.

The difference between Solstice and Equinox are given below:

The seasons are changed on the Earth because of the inclination of the Earth's axis in a fixed direction and due to the change in the position of the Earth around the sun.
On 21st June, the Northern hemisphere is tilted towards the sun. These areas receive more heat because the sun rays fall directly on the tropic of Cancer.
The tropic of Capricorn receives direct sun rays due to tilting of South Pole towards the sun on 22nd December.
The Northern hemisphere experiences autumn season while Southern hemisphere spring season on 23rd September. On 21st March, itIS spring in Northern hemisphere and autumn in Southern hemisphere.

The difference between the summer solstice and the winter solstice is as follows:
Summer Solstice In the Northern hemisphere the longest day and the shortest night occur on 21st June. The Sunrays fall directly on the tropic of Cancer. All these conditions are opposite in Southern hemisphere and it is winter there. The nights are longer than the days in Southern hemisphere. This position of the Earth is called the summer solstice.
Winter Solstice The tropic of Capricorn receives direct rays due to tilting of South Pole towards the sun on 22nd December. The vertically falling sun rays at the tropic of Capricorn 23 1/2° provide heat to a larger portion of it. Therefore, it is summer in Southern hemisphere. This position of the Earth is called the winter solstice.