Motion and Phases of the Moon 4.02-3. The Moon appears to rise in the East and set in the West. This apparent motion of the moon is caused by the rotation.

Motion and Phases of the Moon

4.02-3

• The Moon appears to rise in the East and set in the West.

• This apparent motion of the moon is caused by the rotation of the Earth.

• The Moon revolves or orbits around the Earth with an orbital period of 29.5 days, hence the origins of “Months” of the year.

• As it orbits the Earth, the Moon always has the same side facing towards us.

• Sometimes the Moon’s orbit is such that it comes directly between the Sun and the Earth, blocking the path of sunlight to part of the Earth.

• This is called a solar eclipse.

The moon’s shadow only falls on a small part of the Earth, and only people

standing there can see the total eclipse.

In the eclipse of 2005 above, who saw the total eclipse, people in Nunavut or people in Guyana (South America)?

• In a full solar eclipse, all that can be seen of the Sun is its corona.

• It is dangerous to look directly at a solar eclipse, because it may damage the retinal cones of your eye.

Note on the side:

Solar eclipses only last a few minutes, but must be observed though special filters to reduce the Sun’s powerful radiation.

The next total solar eclipse seen in

Canada will occur in 2024!

• In a lunar eclipse, the Earth blocks the Sun’s light from reaching the moon, so the Earth casts a shadow on the Moon.

Recap:

• Lunar Eclipses: When the earth blocks sunlight from reflecting off of the moon.

•Solar Eclipses: When the moon comes between the sun and us, allowing only a halo to be seen.

Sun From Earth Earth From Space

• We are able to see the Moon because it reflects the Sun’s light.

• Only half of the moon’s surface can be illuminated at any one time.

Sun’s light rays

• As the relative position of the Moon, Sun and Earth change over the period of one month, the amount of the Moon’s surface that can be seen from the Earth varies.

Stop frame animation over a whole month

• This results in the various

phases of the Moon. The Phases of the Moon (6:02 min) http://www.youtube.com/watch?v=0vXWXqGmPCk&feature=related

History Channel (3:16 min): http://www.youtube.com/watch?v=nXseTWTZlks&feature=related

Good recap: Why does the moon look like it changes? (2:10 min) http://www.youtube.com/watch?v=YdI1aDjWLlY&feature=related

Note: Good explanation, but backwards (moon goes counterclockwise, not clockwise) Phases of moon (2:25 min): http://www.youtube.com/watch?v=2aFGNGEcDOk

• (The expression “once in a blue moon” refers to something that happens rarely. A blue moon occurs when the Moon’s phases are timed so that there are two full moons in one month.)

Phases of the Moon, What do we see from Earth?

Closest to the Sun

~7 Days

~14 or 15 Days

~22 Days

Think before you copy, look at how many days into the lunar cycle each image represents.

Phases of the Moon