Question

student exploration: summer and winter
vocabulary: axis, equator, hemisphere, latitude, season, summer, winter
prior knowledge questions (do these before using the gizmo )

1. when during the year is the sun highest in the sky?
2. when during the year is daylight longest? shortest?
3. why do you think it is colder during the winter than the summer?

gizmo warm - up
the space tab of the summer and winter gizmo shows two different \snapshots\ of earth as it orbits the sun. the earth at left shows june 21. the earth at right shows december 21.

1. the white line going through the north pole and the south pole is earths axis.

does the axis go straight up and down, or is it tilted?

1. your latitude indicates how far you are from the equator, a line around earths middle. the person in the gizmo has the same latitude on each date.

turn on show sun rays and slowly drag the person on the left earth toward the north pole. what do you notice about how the sun rays hit the person as she is moved northward?

1. the half of earth north of the equator (the \top\ half) is called the northern hemisphere (hemisphere means \half a sphere\). the southern half is the southern hemisphere.

a. which hemisphere receives more direct sunlight on june 21?
b. which hemisphere receives more direct sunlight on december 21?

Explanation:

1. In the Northern Hemisphere, the Sun is highest in the sky around the summer - solstice (June 21 or 22). In the Southern Hemisphere, it's around the winter - solstice (December 21 or 22).
2. In the Northern Hemisphere, daylight is longest on the summer - solstice (June 21 or 22) and shortest on the winter - solstice (December 21 or 22). In the Southern Hemisphere, it's the opposite.
3. It is colder in winter because the hemisphere is tilted away from the Sun, receiving less direct sunlight and less heat.
4. Earth's axis is tilted at an angle of about 23.5 degrees.
5. As the person is moved northward towards the North Pole, the Sun rays hit at a more oblique angle.
6. A. On June 21, the Northern Hemisphere receives more direct sunlight. B. On December 21, the Southern Hemisphere receives more direct sunlight.

Answer:

1. In the Northern Hemisphere, around June 21; in the Southern Hemisphere, around December 21.
2. In the Northern Hemisphere, June 21; in the Southern Hemisphere, December 21. Shortest: In the Northern Hemisphere, December 21; in the Southern Hemisphere, June 21.
3. The hemisphere is tilted away from the Sun, receiving less direct sunlight and heat.
4. Tilted.
5. The Sun rays hit at a more oblique angle.
6. A. Northern Hemisphere. B. Southern Hemisphere.