Jon Burch Photography
Photograph - Digital Capture
Which is longer, a lunar Synodic month or a lunar Sidereal month? Who cares, you say? The short answer is that a lunar Synodic month is longer - the sidebar is that it took the human population between 2,000 and 3,000 years to figure this out.
To understand the above, one must first realize that anything with the word 'Sidereal' in it, astronomically speaking, refers to aligning with the stars. By the same criteria, anything with the word 'Synodic' in it refers to a coming together to two things. A church synod, for example refers to the 'coming together' of the congregation members and the church. A lunar 'Sidereal' month refers to the time it takes the Earth's Moon to make a complete 360 degree orbit around the Earth and again align with the stars. This happens once every 27.3 days.
However, during the 27.3 days that it takes the Moon to circle the Earth with respect to the stars, the Earth hasn't been sitting still. It has moved in its orbit around the Sun by that same amount. So what, you say? Answer, this additional time causes the lunar Synodic month to be 29.5 days long. It is defined at the time required for the moon to pass through a complete cycle of phases, new moon back to new moon.
The difference between a Synodic month and a Sidereal month is the difference between 29.5 and 27.3 or about 2.2 days. This is the extra required time needed for the Earth to move in its orbit (with the Moon circling) to complete a direct alignment between the Earth, Moon and Sun - new Moon and back to new Moon again. The 'New' phase only happens when the Earth, Moon and Sun are in a straight line with the Moon between the Earth and the Sun. When this happens, it is not visible from Earth, unless the Moon happens to be at perigee - but that's another story...
The location for this image is Cathedral Rock, a famous landmark on the Arizona skyline, and one of the most-photographed sights in the state. This view is from "Oak Creek Crossing" in west Sedona. The Rock is located in the Coconino National Forest in Yavapai County, about a mile west of Arizona Route 179, and about 2.5 miles south of the "Y" intersection of Routes 179 and 89A downtown. The summit elevation of the Rock is 4,921 feet and is a popular short, steep ascent from the Back O' Beyond trailhead to the saddle points or "gaps" at the base of the rock.
Geologically, Cathedral Rock is carved from the Permian Schnebly Hill formation, a red bed sandstone formed from coastal sand dunes near the shoreline of the ancient Pedregosa Sea. Ripple marks are prominent along the lower Cathedral Rock trail, and a black basalt dike may be seen in the first saddle.
Originally called "Court House Rock" on some early maps, Cathedral Rock, like Courthouse Butte or "Church House Rock", has caused endless name confusion to the casual observer.
Photograph copyright Jon Burch Photography
April 8th, 2013
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