Eclipse News

2017 Total Solar Eclipse: I’m Being Follow By A Moon Shadow



On Monday, August 21st, 2017 all of Canada, the United States, Mexico and Central America will fall under the moon’s penumbral shadowAnyone in this hemispheric swath of land gazing up at the sun, with their Scopedawg Optics solar safety glasses on of course, will see a partial solar eclipse.  Only those within the sixty five mile wide zone of the moon’s umbral shadow – the darker, central heart of the penumbra – will also witness a total solar eclipse.  Within this darkest portion of the moon’s shadow sun, moon and earth align to the delight of those gathered in its path.

In a Penumbrum

If you look up shadow in Mr. Webster’s dictionary two of the many entries seem to be relevant to our discussion (parentheses inserted by the dawgs).

  • Partial darkness or obscurity (moon’s shadow) within  a part of space (earth) from which rays from a source of light (sun) are cut off by an interposed opaque body (moon)


  • The dark figure (moon’s shadow) cast upon a surface (earth) by a body (moon) intercepting the rays from a source of light (sun)

As it circles our planet on its monthly course the moon always has its two-tone shadow in tow, normally tapering off to nothingness in the vastness of space.  Out there, not protected as we are by atmosphere, the moon is constantly bathed in the full and unobscured radiation of our sun.  No wonder it appears as though it has taken a whoopin’ over the years.

From our perch here on earth we observe different portions of our natural satellite as it appears to grow and then shrink in a month’s time.  Although half of the moon is always under direct sunlight we see its phases change night to night because of the earth-moon geometry and the moon’s orbital motion.  If you think about it, the only time the moon is completely in shadow is during a total lunar eclipse, when that same geometry is the exact opposite of what it will be on August 21st.  Our shadow engulfs it.



Phased and Confused

In addition to its changing face the moon also changes position from night to night, about a fist’s width at arm’s length.  If you note a thin crescent in the western sky at sunset (the moon has just passed New Moon) in two weeks you will need to do a 180 to see the Full Moon in the eastern sky at sunset.  The graphic above illustrates the alignment of sun, moon and earth at only these two phases of the moon, New when a solar eclipse is possible and Full when a lunar eclipse is possible.

We have inadvertently stumbled upon the first of three requirements for Da Cosmic Mojo to be workin’.  We will hear about the other two in the next post but, know this, possible becomes certain only when all three have been satisfied.

A solar eclipse may occur only if the moon is a New Moon

As a final thought, consider the motions of sun, moon and in particular our earth.  We cling to its surface as it spins on its axis at 1,000 mph and move with it on its 584 million mile annual trek around the sun at 67,000 mph.  Our solar system orbits the center of our Milky Way galaxy at 515,000 mph.  And you don’t feel a thing.  Fascinating.




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