Here Comes the Sun!

What CausesThe Seasons? The Earth The Earth is a sphere in constant motion. The Earth rotates on its axis once every 24 hours. (1 day) The side of the Earth facing the sun experiences day, while the side away from the sun experiences night. Not to scale

What Causes the Seasons? The Earth’s Tilt and Orbit It takes the Earth 365.25 days (one year) to orbit, or revolve, around the sun. The Earth moves around the sun counter-clockwise in an elliptical orbit. Sun Earth

What Causes the Seasons? The Axis of the Earth The Earth spins on its axis, an invisible line going through its core from the North Pole to the South Pole. The axis is not straight up and down, but rather is tilted. The Equator is an invisible line that encircles the widest point of the Earth and is the same distance from each pole. The part of the Earth north of the equator is called the Northern Hemisphere. The part of the Earth south of the equator is called the Southern Hemisphere.

What Causes the Seasons in The Northern Hemisphere The Earth spins, or rotates, counterclockwise on its axis which is actually tilted about 23.5 degrees. When it is summer in the Northern America, the North Pole is tilted toward the sun, giving Texas and the rest of the Northern hemisphere longer hours of daylight. This part of the Earth also receives more direct sunlight, causing increased heat.

What Causes the Seasons In the Southern Hemisphere When the South Pole is tilted toward the sun, the Southern hemisphere has longer hours of daylight and experiences summer. The Northern hemisphere has shorter hours of daylight and winter during this time. The Southern Hemisphere is also warmed by the direct rays of the sunlight during this period of time.

The Earth’s Orbit, Tilt and Seasons As the Earth moves around the sun, it follows an elliptical orbit. The path it takes is more like an oval than a circle. In the diagram below, at Position 1, it is winter in the Northern Hemisphere. At Position 2, the season changes to spring. It is summer in the Northern Hemisphere at Position 3. Finally, autumn occurs when the Earth reaches Position 4.

The Reason for the Seasons If the seasons were caused simply by the Earth’s orbit, people in the northern hemisphere and people in the southern hemisphere would have the same seasons. This is not what happens! Summer in the northern hemisphere occurs at the same time as winter in the south, and vice-versa. Earth’s tilting on its axis and its orbit around the sun work together to create the seasons.