Whats the cause of seasonal changes?

Question

Why is there winter,summer,spring,fall and why does it happen in a cycle?

Answer 1

The sun and the earth's position relative to it.

Answer 2

The planet leans away from the Sun in the winter and leans back in the summer.  It does this twice a year.

Answer 3

Tilt of the earth's axis combined with the effect of the earth orbiting around the sun produces the seasons.

It tilt alone is there(without the orbit),one hemisphere will always be pointing towards the sun and the other hemisphere will be pointing always away from the sun.So,either it will be always summer or winter for a particular hemisphere.

If orbit alone is there(without tilt),the day time and night time will always be equal in all places and hence winter and summer season will not be there.

Answer 4

The way the earth tilts on its axis as it orbits the sun.