World Globe

Principles of Science: Earth’s Orbit and Tilt

This model of the earth is tilted on its axis exactly like our planet. When the sun shines, see where the sun is falling at that time on the earth. The World Globe also illustrates the parts of the earth that are in shadow–night.

The Earth is tilted at 23.5 degrees and this tilt is responsible for the seasons. Depending on the location of the Earth in its orbit around the sun, in other words, the time of year, the northern hemisphere may be tilted towards the sun, or away. When the northern hemisphere is pointed towards the sun, it receives more direct sunlight than the southern hemisphere. This direct sunlight causes warmer temperatures: summer. The southern hemisphere, at that time, would experience winter; it does not receive as much direct sunlight because it is tilted away from the sun.

In the Northern Hemisphere, June 21 is the longest day of the year—the summer solstice. Conversely, June 21 is the shortest day of the year in the Southern Hemisphere – the winter solstice. When it’s the beginning of summer here in Illinois, it’s wintertime in Australia. On December 22, the shortest day of the year in the Northern Hemisphere, it’s the longest day in the Southern Hemisphere.

The same concept applies to the spring (March 21) and autumn (September 23) equinoxes. During an equinox, the earth is neither tilted towards or away from the sun. Day and night occur for equal amounts of time. Spring here in the Northern Hemisphere is autumn in the Southern Hemisphere, and vice versa.