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.• Describe the yearly revolution (orbit) of Earth

around the sun.

• Explain that Earth's axis is tilted relative to its yearly orbit around the sun.

• Investigate the relationship between the amount of heat absorbed and the angle to the light source.

Objective 2: Explain how the relationship between the tilt of Earth's axis and its yearly orbit around the sun produces the seasons.

• Compare Earth’s position in relationship to the sun during each season.

• Compare the hours of daylight and illustrate the angle that the sun's rays strikes the surface of Earth during summer, fall, winter, and spring in the Northern Hemisphere.

• Use collected data to compare patterns relating to seasonal daylight changes.

• Use a drawing and/or model to explain that changes in the angle at which light from the sun strikes Earth, and the length of daylight, determine seasonal differences in the amount of energy received.

• Use a model to explain why the seasons are reversed in the Northern and Southern Hemispheres.

Seasons

A regular change in temperature that repeats itself every year

Words to know: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

http://vortex.plymouth.edu/sun/axis.gif

Words to know:

Rotation - spinning of Earth on its

axis, which causes day and night; it

takes 24 hours for Earth to complete

one rotation

http://vortex.plymouth.edu/sun/rot8_an.gif

Words to know:

Revolution - the motion of Earth around the Sun, which takes about 365 1/4

days, or one year, to complete

http://www.usoe.k12.ut.us

Words to know:

Orbit - curved path followed by Earth as it moves around the Sun

http://www.vt-2004.org/mt-2003/mt-mercury-orbit.jpg

• http://www.youtube.com/watch?v=DuiQvPLWziQ&feature=player_embedded

The Earth’s Tilt

The Earth's axis is tilted by 23.5°

http://www.crh.noaa.gov/fsd/astro/season.htm

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.

Seasons - Changing Day Length

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.

http://inkido.indiana.edu/a100/celestialsphere5.html

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.

http://inkido.indiana.edu/a100/celestialsphere5.html

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).

Go to this Website for Instructions on assignment #3

http://www.uen.org/core/science/sciber/sciber6/stand-2/angle.shtml

Seasons - I'm Spinning and I Can't Stop!

Activity #4Please click on the link below

http://www.uen.org/core/science/sciber/sciber6/stand-2/revolves.shtml

Activity #5 Worksheet

• Sunrise, Sunset

Activity #6 Worksheet

• Changing Shadows

So, seasons are caused the tilt of the Earth’s axis

Remember:

• The seasons are the result of this tilt of the Earth's axis. • If the tilt of the Earth's axis was 0°

there would be no difference in how the rays from the sun hit its different regions, and there would be no seasons.

The Earth's seasons are not caused by the differences in the distance from the Sun throughout the year.

The seasons are the result of 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!

ReviewLook closely at where the Sun is hitting the Earth during each season:

http://Search.Lycos.com/setup.asp?r=5&src=clear2&query=weather+savvy

http://www.enchantedlearning.com/subjects/astronomy/planets/earth/Seasons.shtml

http://www.nmm.ac.uk/uploads/gif/seasons-full.gif

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.Example A

Example B

Congratulations we have finished this Unit

• Make sure you study for the test using the study guide