The Open Door Web Site
Part X : The Environment
Environmental Factors Appropriate for Life
THE SEASONS AND THE SUN
The Seasons and the Sun
The Earth is in fact tilted on its own axis. As the Earth rotates around the Sun, the northern hemisphere will be tilted slightly more towards the Sun in the summer months than in the winter months. This makes it warm in Europe in June, July, and August.
The diagram above shows the position of Paris (indicated by the Eiffel Tower) at noon at different seasons of the year. At which position (A or B) would you expect it to be colder in Paris? What do "x" and "y" represent?
At the same time of the year in the southern hemisphere, it is colder because the south pole is tilted away from the Sun. So in Australia, the months of June, July, and August are the coldest months of the year. These annual temperature changes in the different hemispheres are referred to as seasons.
At the equator, the effects of the tilt of the Earth's axis are less intense. The Sun seems to be directly overhead at all times of the year. The result is that the climate remains more or less the same throughout the year.
Each year, in the northern hemisphere there are four days with an astronomical importance:
Keep in mind that the winter solstice happens when the north pole is pointing away from the Sun. At the same time, the other pole will be experiencing the longest day because it is tilted towards the Sun. The spring equinox marks the beginning of springtime and the autumn equinox marks the beginning of the fall. It should be obvious that the solstices and the equinoxes are six months apart.
Many countries have adopted a system whereby clocks are turned back an hour in autumn and set ahead an hour in the spring. This is called daylight savings and it has allowed countries to save money on electricity.
How the Seasons Influence the Biosphere
Seasonal changes greatly influence the plants and animals living on Earth. At different times of year, the numbers and types of organism found in different places will differ greatly according to the time of the year as indeed they differ during the day time and the night time. Plants make their food during the daytime using energy from the Sun. At night, plants cannot make food.
Some animals prefer the night time to feed. Mice and other rodents feed at night so that they can hide in the dark from other animals who want to eat them. Good mice hunters like owls can fly and catch mice at night. Most birds prefer the daytime, however, and so do many animals. Many living organisms depend on the heat from the Sun to keep them warm.
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