Why do the seasons of the year exist

The seasons of the year are four: spring, summer, autumn and winter. Each of them has its own characteristics. However, although in our perception they are four well-determined periods, from a physical perspective, the seasons are the natural consequence of the movement of the planet’s axis with respect to its orbit.

Although the movements of the planet Earth best known are that of translation (around the Sun) and rotation (around itself), there are other movements that it performs and, of all of them, one is responsible for the seasons of the year. This movement is what the Earth’s axis makes with respect to the orbit around the Sun. Although we do not perceive it, the Earth’s axis is only perfectly perpendicular to the Sun during the spring and autumn equinoxes (when day and night are just as long). The rest of the year, the axis is inclined, reaching its maximum inclination on the days of the summer and winter solstice (the longest or shortest day and night of the year respectively). This is because the axis is in constant motion in which, when it reaches its extreme (one of the solstices) it returns to its position perpendicular to the orbit (equinoxes). You will then repeat the same tilt, but in the opposite hemisphere.

Although a priori it may seem insignificant, the movement of the Earth is responsible for the fact that the hours of light throughout the year are not the same despite being in the same geographical point. The consequence of these light cycles is that there are longer and shorter days , with their corresponding nights. Consequently, temperatures also vary and, in this way, it is how what we perceive as seasons from the human and biological perspective take place.

This natural movement of the Earth that causes changes in the hours of light and in the temperature that reaches the same geographical region is of fundamental importance for life on Earth . It must be taken into account that these seasonal cycles have existed on our planet practically since its birth and, consequently, life has developed from this previous situation, which has led to it adapting to its existence.

Some examples of the importance of the seasons are the flowering cycle, which begins in spring in most plants, which corresponds to the time when the heat begins and, with it, the presence of pollinating insects such as the bees . Another example is deciduous trees , which lose their leaves when there is not much light and thus use their biological resources more efficiently. Migrations can also be taken as an example of some animals, especially in the case of birds and some insects, which move geographically depending on the climatic conditions, usually, seeking more pleasant temperatures and adapting their reproductive cycles to these conditions.

An easy way to explain how the seasons of the year work to children is by using a globe and the light of a lamp or flashlight. With these two tools, and taking as reference different points on the surface of the globe, the inclination of the spherical map can be changed so that the child himself can check how, by changing the axis, the same place has more or less when we rotate the balloon.

It is a very simple experiment but, at the same time, very illustrative, and it is sure to be of great help when the little ones understand what the seasons of the year are from a global perspective and on a large scale.