Why do we see phases of the Moon?
· The phase of the Moon depends on its position relative to the Sun as it orbits Earth.
· Waxing = Increasing
· Waning = Decreasing
o phases from full moon to new moon
o avg. Earth to Moon Distance is 380,000 KM
o each complete cycle of phases, from 1 new moon to the next new moon, takes approximately 29 1/2 days
§ origin of the word "month" is created
· What causes Eclipses.....
o Sun + Earth + Moon = ___________________ (straight line)
· Lunar Eclipse - occurs when the Earth lies directly between Sun & Moon
o Earth's shadow falls on Moon
· Solar Eclipse - occurs when the Moon lies directly between Sun & Earth
o Moon's shadow falls on Earth
· Nodes - the 2 points in each orbit when Moon crosses the surface
o eclipses can occur during periods when nodes line up with Sun & Earth
o ppl can see eclipses when a full / new moon occurs at one of the points where the Moon's orbit crosses the ecliptic plane
§ ecliptic - the Sun's annual path around the celestial sphere
o lunar eclipse occurs when full moon occurs, at or very near, to one of the nodes
o solar eclipse occurs when a new moon occurs, at or very near, to one of the nodes
· Shadows of Moon / Earth consists of 2 distinct regions:
o central umbra - sunlight is completely blocked
o surrounding penumbra - sunlight is only partially blocked
· Total Lunar Eclipse - Moon passes through Earth's umbra
· Partial Lunar Eclipse - Only part of the Full Moon passes through the umbra
· Penumbral Lunar Eclipse - Moon passes only through Earth's penumbra
· Totality - The time during which the Moon is entirely engulfed in the umbra
· Annular Eclipse - Ring of sunlight surrounding the Moon
· Saros Cycle - Eclipses recur in a cycle of approximately 18 YRS & 11 1/3 DAYS
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