Why do you have four seasons every year?

Answer 1

The seasons are a result of the fact that the Earth orbits the Sun once every year and the fact that the Earth's axis of spin in inclined 23 degrees to the plane of the Earths orbit of the sun.
The tilt means that once year the north and south polar regions are tilted towards the sun (causing the Northern and Southern summers and winters) and for one day in spring and autumn the Sun to be overhead at the equator.

Days are therefore shortest during a winter season, longest during the summers season and equal in spring and autumn.

For areas of the Earth within the tropics, the variation between the seasons is less marked than further towards the poles. One will normally see the seasons expressed in times of heavier rainfall twice a year and a slight variation in temperature. If you concentrate on the temperature you will only mark 2 seasons a year but if you mark the rainfall you should have 4 seasons, 2 wet and two dry.

Answer 2

The tilt of the Earth's AXIS is the most important reason why seasons occur. We have hot summers and cold winters because of the tilt of the Earth's axis. The tilt of the Earth means the Earth will lean towards the Sun (Summer) or lean away from the Sun (Winter) 6 months later.

The earth orbits the sun, completing one orbit every (approx) 365.25 days. But whilst it spins on its North-South axis (causing day and night) it also tilts slightly, causing the North Pole to 'lean' towards the sun for part of it's orbit, then the South Pole for the other part. This has the effect of giving more concentrated sunlight on the hemisphere which is tilted towards the Sun.

During Winter in the Northern Hemisphere, because the North Pole is leaning away from the sun, the sun itself appears to be very low in the sky (about 13 degrees, in mid winter, in the mid UK - 53 degrees latitude,) whereas in mid summer, the sun appears high in the sky (approx 60 degrees at the same latitude,) giving a far longer day and a shorter night. The effect (i.e. the difference between summer and winter) becomes more pronounced, the nearer one gets to the poles. In mid summer, at the North Pole, because it is leaning towards the sun, the sun never sets, and there exists, for a few weeks, 24 hour daylight. At the South pole at that time, 24 hour darkness prevails. Therefore the further North, or South one travels, away from the equator, the more pronounced the seasons become.

Conversley at the equator, there is no perceptible difference in daylight/night times, nor summer and winter (from the perspective of sunlight.) In Singapore, for instance, (quite near the equator) there is only about 8 minutes difference in day/night times, from June to December. In effect (barring the effect of weather systems) they have no seasons, 12 hour days and 12 hour nights the whole year round.

Around March and September, (the Equinoxes) neither pole 'leans' towards the sun, and the days and nights are of more or less equal length. This is Spring and Autumn.

It has nothing to do with the distance from the Earth to the sun, as some people believe. On midsummer day 2012 for instance, the Sun will be 4.86 million km more distant than it was on 21st of December 2011 (mid winter,) because the Earth's orbit is slightly eliptical. But it will still be a lot warmer (we hope!) than it was in December.

the tilt of the earth around the sun

Answer 3

maybe because its warm there then here