Lunar Phases and Eclipses animated GIF created by

Lunar Phases and Eclipses animated GIF created by Antonio Cidadao Barbara Gage PSC 121 Prince George’s Community College

Lunar Phases Because of the rotation of the Earth, the Moon appears to rise and set in the same manner as the Sun does (east to west). n The Moon revolves around the Earth counterclockwise (looking down from the North Pole) while the Earth revolves around the Sun (also counter-clockwise from northern view). n The phase of the Moon that we see from Earth depends upon the alignment of the Sun, Moon, and Earth at any given time as they revolve. n

Here is a web site that allows you to see an animation of the positions of the Earth, Moon, and Sun. It will illustrate the lunar phases as the Moon revolves around the Earth. http: //astro. unl. edu/naap/lps/animations/lps. swf

Aspects of Lunar Phases n One half of the Moon’s surface is always illuminated by the Sun. n When the Moon is in any position in the hemisphere between the Sun and the Earth, less than 50% of the lunar surface we see will be illuminated. During this time we see the new and crescent phases.

Aspects of Lunar Phases Hemisphere between Sun and Earth Hemisphere between Earth and outer space Diagram modified from http: //astro. unl. edu/naap/lps/lunar. Page 2. html

Aspects of Lunar Phases n One half of the Moon’s surface is always illuminated by the Sun. n When the Moon is in any position in the hemisphere between the Earth and outer space, more than 50% of the lunar surface we see will be illuminated. During this time we see the full and gibbous phases.

Aspects of Lunar Phases Hemisphere between Sun and Earth Hemisphere between Earth and outer space Diagram modified from http: //astro. unl. edu/naap/lps/lunar. Page 2. html

Aspects of Lunar Phases n One half of the Moon’s surface is always illuminated by the Sun. n When the Moon is at the cross-over point between these two hemispheres, the phase we see is the quarter phase.

Aspects of Lunar Phases Hemisphere between Sun and Earth Hemisphere between Earth and outer space Diagram modified from http: //astro. unl. edu/naap/lps/lunar. Page 2. html

Aspects of Lunar Phases The illumination and darkening sections seem to “move” from right to left across the Moon’s surface over the course of a lunar cycle. n When the illumination is increasing, we say the phase is waxing. When the illumination decreases it is called waning. n

Lunar Phases Waxing crescent – 1 st quarter – waxing gibbous Waxing gibbous Full – waning gibbous Waning gibbous – waning crescent Waning crescent Photo from: http: //aa. usno. navy. mil/graphics/Moon_phases. jpg

Eclipses n When the Sun or Moon is blocked to an observer on Earth over a short period of time (minutes to hours) an eclipse has occurred. n If the Sun is blocked it is a solar eclipse. n If the Moon is blocked it is lunar eclipse.

Lunar Eclipse When the Moon is in the full moon position, the light from the Sun may be blocked by the Earth which casts a shadow. As the Moon travels into the shadow it is gradually covered. Ancients thought the Moon was being eaten. View from above the Northern Poles http: //www. hermit. org/Eclipse/why_lucnar. html

Lunar Eclipse Shouldn’t there be a lunar eclipse every time we have a full moon?

Lunar Eclipse The Earth revolves around the Sun on a plane called the plane of the ecliptic. The Moon orbits Earth on a plane but that plane is tilted 5 o with respect to the plane of the ecliptic. This means that when the moon is in the full position it may be above or below the shadow of the Earth and no eclipse will occur. Diagrams from http: //www. ap. stmarys. ca/demos/content/astronomy/lunar_eclipse. html

Lunar Eclipse 4 3 1 2 In positions 1 and 2 the Moon’s orbital tilt places the Moon-Earth. Sun in alignment so a lunar eclipse can occur. At positions 2 and 3, even though the lunar phase is full, the Earth’s shadow misses the Moon so no eclipse occurs.

Lunar Eclipse Sequence Passing into the shadow Totality Coming out of the shadow

Solar Eclipse When the Moon passes directly between the Earth and the Sun, the Moon casts a shadow on the Earth. Where the shadow falls, observers will see an eclipse of the Sun, a solar eclipse. As with a lunar eclipse, the shadow of the Moon may fall above or below Earth and no eclipse occurs. If the entire Sun is covered we see a total eclipse; of only part if the surface is blocked we see a partial eclipse. http: //www. hermit. org/eclipse/why_solar. html

Solar Eclipse This is a photo taken from the former Soviet space station MIR. It shows the shadow of the Moon falling on the Earth in 1999. Anyone under the shadow saw a solar eclipse.

Solar Eclipse If the Moon’s shadow falls short, an observer on Earth will see only some of the Sun’s surface blocked. This configuration results in an annular eclipse. http: //www. hermit. org/eclipse/why_solar. html

Solar Eclipse The royal blue line through Africa and Asia shows the path for the March 29, 2006 solar eclipse. Observers on this path saw some stage of the eclipse. http: //sunearth. gsfc. nasa. gov/eclipse/SEmono/TSE 2006. html

The link below will take you to the NASA page that lists all the solar eclipses for the next few years. There will not be another annular eclipse until February 7, 2008. The next total solar eclipse will occur on August 1, 2008. Most of the visible area for these eclipses is ocean. http: //sunearth. gsfc. nasa. gov/eclipse/solar. html