GEOG 103 - Week 1 (solar energy to Earth and the seasons)

150 million kilometers

Perihelion: Earth is closest to the Sun on January 3rd (peri-heel-yun)

Aphelion: earth is farthest from the Sun on July 4th (a-feel-yun)

Plane of the ecliptic

Solar wind is clouds of electrically charged particles

Sunspots are caused by magnetic storms on the Sun and have activity cycles of 11 years

A group of a hypotheses that have been verified. It remains valid as long as there is no evidence to dispute it.

• A generalized rule to explain a body of observations. Usually verbal or mathematical statements (equations).
• It implies a cause-and-effect situation

• 1. Revolution of the Earth around the Sun once every year.
• 2. Rotation of the earth on its axis once every 24 hours
• 3. Tilt of the Earth's axis at 23.5° from the plane of the ecliptic
• 4. Axial parallelism : the axis maintains its alignment during orbit around the Sun
• *The North Pole always points toward the North Star (Polaris).
• 5. Sphericity

Counterclockwise: from West to East

Is the point at which the Sun is directly overhead. Moves westward circling the globe once today and also moves north and south between the tropics during the year. The movement of the subsolar point is called declination.

During the December solstice the subsolar point is on the Tropic of Capricorn and during the June solstice it is on the Tropic of Cancer.

During the March and September equinoxes, the subsolar pointi is on the equator

The tropics receive 2.5 times the amount of energy from the Sun than the poles do.

• Winter / December solstice : December 21-22.
• Subsolar point: Tropic of Capricorn 23.5°S

• Vernal / March equinox: March 20-21
• Subsolar point: Equator 0°

• Summer / June solstice: June 20-21
• Subsolar point: Tropic of Cancer 23.5°N

• Autumnal / September equinox: September 22-23
• Subsolar point: Equator 0°

Impact theory states that Earth had a sister planet named Theia which collided into the Earth, creating Earth's tilt. The debris from Theia orbited Earth and eventually formed the moon.