TOPIC #1:Chapter 22Origin of Modern Astronomy

Section 2: The Earth, Moon, Sun System• Earth has two forms of motion:

• Rotation, which is the turning of an object on an axis.

• Revolution, which is the motion of a planet or moon along its orbit.

Section 2: The Earth, Moon, Sun System• The Earth rotates on a tilted axis. (This gives us the seasons.)

• It takes the Earth about 24 hours to make one rotation.

Section 2: The Earth, Moon, Sun System• The Earth makes one orbital revolution in about 365 days.

• When the earth is farthest from the sun it is at its apihelion• About July 4 each year.

• When the earth is closest to the sun it is at its perihelion• About January 3 each year.

Section 2: The Earth, Moon, Sun System• The direction of the tilt of Earths axis determines the seasons.

Section 2: The Earth, Moon, Sun System• The moon rotates around the earth in a similar way to the

earth rotating around the sun.

• When the moon is closest to the earth it is at perigee.

• When the moon is farthest from the earth it is at apogee.

Section 2: The Earth, Moon, Sun System• Due to this rotation we witness phases of the moon on a

monthly basis.

Section 2: The Earth, Moon, Sun System• A waxing moon is when the

moon appears to be growing in visibility.

• A wanning moon is when the moon appears to be shrinking in visibility

• A crescent moon is a moon that is less than half visible.

• A gibbous moon is a moon that is more than half visible

Section 2: The Earth, Moon, Sun System• During the full moon and new moon phases the moon must

pass in line with the earth and the sun.

• At the correct angle Solar and Lunar eclipses may occur.

• Solar Eclipse, when the moon moves directly between the earth and the sun blocking the sun from view.

• Lunar Eclipse, when the earth moves directly between the moon and the sun shadowing the moon from the suns light.