1. Lesson 3: Seasons on earth notes

2. Lesson Three Vocabulary
Atmosphere: A thin layer of gases that surround the Earth and help to absorb solar energy from the Sun.
Latitude: How many degrees North or South a location is from the equator.
Angle of Separation: Distance between two objects, for example distance of Polaris from an observer on Earth.
Polaris: Our current North Star. A bright, easily spotted star in our sky; the last star on the handle of the “Little Dipper”.
Horizon: Where the sky and Earth’s surface seem to meet.

3. Inquiry 3.1: Investigating Seasons on Earth
Seasons are caused by the tilt of the Earth, the shape of the Earth, and the Earth’s revolution around the Sun. These change the amount of solar energy that hits the Earth.
The tilt of Earth on its axis affects the angle at which the Sun’s rays pass through the atmosphere.
The higher the Sun’s angle= The less atmosphere the rays must go through, which increases the solar radiation (warmer temperatures).
The lower the Sun’s angle= The more atmosphere the rays must pass through, which decreases the solar radiation (colder temperatures).

4. Seasons and the sun

5. Summer and Winter Solstice/ Autumnal (fall) and Vernal (spring) Equinox:
When a hemisphere is tilted toward the Sun, it experiences summer and longer day lengths.
When a hemisphere is tilted away from the Sun, it experiences winter and shorter day lengths.
Autumnal (fall) and Vernal (spring) Equinox: On two days of the year, the Sun is over Earth’s equator and neither hemisphere is tilted towards the Sun. On those two days, the surface of Earth in both hemispheres receives equal amounts of energy from the Sun. Also, night and day are almost equal in length all over the world except at the poles.
The equinoxes occur on or around March 21 and September 21 depending on the hemisphere.
Helpful Hint: The Three E’s- Equinox, Equator, and Equal

6. Summer and Winter Solstice/ Autumnal (fall) and Vernal (spring) Equinox:
Sumer and Winter Solstice: When the Sun reaches its northernmost point- longest day of the year and the first day of summer. When the Sun reaches its southernmost point- shortest day of the year and the first day of winter.
The solstices occur on or around December 21 and June 21 depending on the hemisphere.

8. Inquiry 3.2: Observing the North Star
The north of Earth’s axis currently points to Polaris, our North Star.
Since Earth rotates on its axis, the stars seen in the Northern Hemisphere appear to circle around Polaris.
On Starry Night, Polaris appeared to stay in the same spot.
The altitude of the North Star above the horizon in the Northern Hemisphere is equal to the latitude of the observer.
Since we live at a latitude of 40 degrees North, Polaris appears to be 40 degrees above the horizon.

9. Inquiry 3.3: Investigating Seasons at Different Latitudes
Shadows change according to the time of day (where Earth is positioned in its rotation).
Shadows change according to the time of year (where Earth is positioned in its orbit).
The length of daylight and the apparent path of the Sun for each season vary at different latitudes. The further North you get, the longer the hours of daylight.