Seasons. What do you KNOW about seasons?. The Big Idea. Students will understand how Earth’s tilt on its axis changes the length of daylight and creates the seasons. Objective 1: Describe the relationship between the tilt of Earth's axis and its yearly orbit around the sun.
A regular change in temperature that repeats itself every year
Axis - imaginary line around which Earth spins, causing day and night, and that is drawn from the north geographic pole through Earth to the south geographic pole
Rotation - spinning of Earth on its axis, which causes day and night; it takes 24 hours for Earth to complete one rotation
Revolution - the motion of Earth around the Sun, which takes about 365 1/4 days, or one year, to complete
Orbit - curved path followed by Earth as it moves around the Sun
The Earth's axis is tilted by 23.5°
As the Earth moves around the Sun, this axis stays always pointing in the same direction.
This means that, during part of the year, the northern part of the Earth will lean more directly to the sun, and during other parts of the year the southern part of the Earth will.
The Earth during one full year as you would see it if you looked straight at it from the Sun.
The part of the Earth that is directly facing the sun changes with the time of the year.
The northern half faces the sun for a while, then moves south of the equator, only to move back to the north again.
When the northern hemisphere is leaning toward the sun, the rays coming from it hit this part of the Earth at a larger angle than on other parts of the world.
This means that the same amount of light is distributed over a smaller surface, and so these places receive more heat than the others.
The southern hemisphere is experiencing Winter, the northern hemisphere has Summer.
The energy that hits the Earth by the Sun changes over the year.
The angle the Sun is above the horizon determines how much heat and light strike each square meter of ground.
In the winter the Sun's energy is weakened because the Sun's ray strike the ground rather indirectly as compared to the summer months when the Sun's rays strike the ground more directly.
This means that the ground receives more energy (more heat) per square meter in the summer than in the winter.
More energy is received by the ground during the summer (high temperatures) and less energy during the winter (lower temperatures).
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So, seasons are caused the tilt of the Earth’s axis
I know this is a repeat, but it is important that you understand this idea. Many Americans, including Harvard graduates, do not know what causes seasons!
Imagine Earth as it revolves around the sun. The table below shows Earth at opposite sides of the sun. These two examples represent Earth's position for summer and winter.