PGCC PSC 121 Gage The Earth and Sun Shedding Some Light on the System

PGCC PSC 121 Gage Earth’s Rotation… Earth’s rotation on its axis generates periods of daylight and night. Earth’s rotation on its axis generates periods of daylight and night. ces/observingsky/motion1.htm ces/observingsky/motion1.htm

PGCC PSC 121 Gage Earth’s Rotation… The amount of daylight/nighttime is also determined by the amount of Earth’s tilt. The Earth’s axis is tilted 23.5 o from the plane of the Earth’s orbit around the Sun. The amount of daylight/nighttime is also determined by the amount of Earth’s tilt. The Earth’s axis is tilted 23.5 o from the plane of the Earth’s orbit around the Sun.

PGCC PSC 121 Gage Earth’s Rotation… The amount of daylight/nighttime is also determined by the amount of Earth’s tilt. The Earth’s axis is tilted 23.5 o from the plane of the Earth’s orbit around the Sun. The amount of daylight/nighttime is also determined by the amount of Earth’s tilt. The Earth’s axis is tilted 23.5 o from the plane of the Earth’s orbit around the Sun.

PGCC PSC 121 Gage Earth’s Revolution… The motion of the Earth in its orbit around the Sun is an ellipse, not a circle. That means that at some points in the orbit the Earth is closer to the Sun than at others. Circle Ellipse

PGCC PSC 121 Gage Earth’s Revolution… When the Earth is closest it is at perihelion. When it is farthest, it is at aphelion. The difference in distance is about 3.5%...not enough to account for the seasonal changes!

PGCC PSC 121 Gage Earth’s Revolution… So what causes the daily and seasonal changes? Earth’s curvature And its tilt !

PGCC PSC 121 Gage Earth’s Revolution…

PGCC PSC 121 Gage Earth’s Revolution…

PGCC PSC 121 Gage Earth’s revolution

PGCC PSC 121 Gage Earth’s Revolution LengthofDay.swf Since Earth’s tilt always points in the same direction, at a given point on the Earth the rays change in directness and duration.

PGCC PSC 121 Gage Earth’s Revolution Since Earth’s tilt always points in the same direction, points on the Earth will experience seasonal changes.