I. Round Earth-Flat Earth
A. Sailing Ships
1. The horizon is where the sky and Earth
appear to meet.
2. Your line of sight is the straight path taken
by light from an object to your eye.
3. Ships sailing out to sea appear to sink on
the horizon.
4. If the Earth were flat, you’d see the entire
ship out on the horizon.
What does the ship appear to be doing?
HORIZON
B. Shadow Evidence
1. Eratosthenes found the circumference of the
Earth using sticks, shadows, some geometry, and
feet!
2. Light rays travel in straight lines.
3. Because the Sun is so large and so far away, all
rays of light hitting anywhere on Earth are parallel
to one another.
4. A pole only casts a shadow when the sun shines
on its side, not on its top.
5. Poles on a curved surface cast shadows of
different lengths.
6. The shadows are longer at higher latitudes.
7. Local noon is when the sun is directly
overhead in the sky (does not mean 12pm
noon!)
8. Shadows in winter are longer than shadows in
summer due to the changes in the angle of
the sun.
II. Day and Night
1. Earth rotates, or spins on its axis in a counterclockwise direction. (West to East)
2. Day and night are a result of rotation.
3. The sun appears to move across the sky from
east to west due to Earth’s rotation.
4. Shadows change during the day due to the
changing position of the sun in the sky.
5. The sun is a source of light that illuminates Earth
during the day.
6. When light falls on a spherical object, like a
planet, exactly half is in the light and half is in
the dark.
7. The Earth rotates on its axis once every 24
hours, giving the illusion of a sun that rises
and sets.
8. One complete rotation of our planet describes
one complete day. One rotation of Earth is one
day, or about 24 hours.
III. Seasons
1. The earth revolves (orbits) around the sun—about
365 1/4 days—one year.
2. The tilted axis –23.5° gives us seasons.
3. The angle of sunlight affects temperature--the
more direct the angle of sunlight the warmer it is.
The angle varies due to Earth's spherical shape.
Ex. It is warmer at the equator because it gets more
direct sunlight, and cooler at the poles because the
sunlight is at an angle.
4. Earth's tilt affects not only the intensity of sunlight
falling on earth, but also the number of daylight
hours.
5. The number of daylight hours changes from
season to season.
The map shows where solar power works best in the United States.
The places in the map that are color blue get the least amount of sun.
The places with red get the most amount. This means that the red
places are the best locations to use solar electricity.
Where would you put your solar panels?
6. In the No. Hemisphere around June 21 is longest day of year. This
is called the Summer Solstice.
7. In the No. Hemisphere around December 21 is the shortest day
of the year. This is called the Winter Solstice.
8. The Vernal Equinox, or Spring is around March 21 and the
Autumnal Equinox, or Fall is around September 21. Sunlight spreads
evenly across equator and there is about 12 hours of day and night
across the globe. The amount of daylight varies due to refraction of
light in the atmosphere.
9. The Earth is actually a little closer to the sun in its orbit during
winter. This is called perihelion.
10. The Earth is a little further from the sun in summer. This is called
aphelion.
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