Tuesday, September 20, 2011


The Earth's seasons are not caused by the differences in the distance from the Sun throughout the year (these differences are extremely small). The seasons are the result of the tilt of the Earth's axis.

The Earth's axis is tilted from perpendicular to the plane of the ecliptic by 23.45°. This tilting is what gives us the four seasons of the year - spring, summer, autumn (fall) and winter. Since the axis is tilted, different parts of the globe are oriented towards the Sun at different times of the year.

Summer is warmer than winter (in each hemisphere) because the Sun's rays hit the Earth at a more direct angle during summer than during winter and also because the days are much longer than the nights during the summer. During the winter, the Sun's rays hit the Earth at an extreme angle, and the days are very short. These effects are due to the tilt of the Earth's axis.

Shadow Notes

• Shadows are formed when light cannot pass through an object.

• The position of light affects the direction of the shadow.

• Shadows are created on the side of the object OPPOSITE the light source.

• Shadows change size according to the position of the light source.

• Shadows on the Earth, caused by the Sun during the day, change size and direction due to the Earth’s rotation on its axis.