As many of us may have suspected all along, the entire world is indeed tilted at a 23.5 degree angle. For reasons which should become apparent shortly, this tilting of the planet is the main reason we experience changes of season. It also explains why some of the Earth's inhabitants only mark seasonal changes on calendars while others must prepare for a number of extreme weather conditions. The seasons change as a the result of sunlight striking the Earth's surface at different angles as the Earth revolves around the sun.
Because the Earth is tilted on its axis, the north and south poles each spend time pointed towards and away from the sun. The sun's light and heat energy strike the central portion of the planet most directly, which means inhabitants who live along the equatorial region experience almost no changes of season. The weather conditions along the Earth's equator are almost continually hot and windy, with only occasional rains for relief. In those tropical regions, the tilt of the Earth has little to no effect on their seasons.
In other parts of the world, however, the tilt and relative position of the Earth to the sun have much more profound effects. Surprisingly enough, the distance between the Earth and the sun has little bearing on the changes of season. The Earth is farthest from the sun during the month of July, one of the warmest months in the northern hemisphere. What matters most is the angle of the sun's rays as they reach the planet's surface. When the Earth is tilted away from the sun, the rays strike the northern hemisphere at an angle, which means the heat energy is not as direct. Therefore, the northern and southern hemispheres experience changes of season, with the north experiencing winter and the south experiencing summer.
As the Earth continues to revolve around the sun, the tilt angle is reversed and there is another change of seasons. The seasons known as spring and autumn are transitional phases as the sun's rays become refocused. Many events in nature, such as the appearance of new growth in the spring or the shedding of leaves in autumn, are triggered by the changes in temperature or available daylight as the sun's energy becomes more diffused. The changes of season are also an example of nature's law of conservation at work. The cycle of birth, life, decay and death helps to keep the planet in proper balance, rather than force animals and plants to maintain a constant and exhausting pace of life.