Eclipse Mania: Are you In?   4 comments

A diamond ring appears as the sun comes out of total eclipse in 2009.

On this August 21st a shadow will pass across the United States.  At that point on its slow 4-week revolution around the earth, the moon will pass directly between the sun and earth.  Since it’s just the right size and distance from us, making it appear the same size as the sun, the moon will block the entire solar disk.  It will make the normally invisible corona (or atmosphere) of the sun visible, along with a number of other normally hidden features of the sun’s surface.

For a brief few moments day turns to night, confusing animals and causing panic among those humans not aware of what they are seeing.  Stars and planets are visible at noontime.  As the earth spins below the blocked sun, a shadow races east over a narrow sliver of land and sea, making the event a very brief one for anyone along its path but also causing strange atmospheric effects like shadow bands.  It’s a total solar eclipse, one of the strangest and most beautiful natural phenomena a person can see.

The Nature of a Solar (vs. Lunar) Eclipse

A total lunar eclipse happens when the earth lies between the sun and the moon; that is, at new moon.  It’s when the alignment of this monthly event is perfect, allowing the earth to cast a shadow over the moon.  A total solar eclipse, which happens at new moon, is when the moon lies directly between Earth and the sun and casts a shadow on earth.

It’s unlike a total lunar eclipse in two big ways.  First, a lunar eclipse, while beautiful and worthwhile, is simply not as stunning and multi-dimensional as a total solar eclipse.  Second, because of the earth’s much larger shadow, a lunar eclipse is a common thing to see while a total solar eclipse is a very a rare event to witness.

It’s not as if solar eclipses are in general rare.  Most years see two of them in fact.  But they are rare for any given point on earth.  On average the wait for any given point on earth is 375 years.  Some places have been treated to two in a row less than two years apart.  Other places have gone 35 centuries or so between successive eclipses.

During partial eclipse before and after totality, do not look directly at the sun without the right filter. But you can project its image onto any surface, and easily see sunspots. During totality you can look right at an eclipse with your naked eyes.

Why is something that happens every year experienced by us so rarely?  For one thing the path along which the eclipse is total (rather than partial) is very narrow, about 70 miles wide.  For another a solar eclipse may occur anywhere, with no regard for population or whether over land or ocean (remember water covers over 70% of the earth).

Finally, most solar eclipses are not total.  Since 2000 there have been 30 solar eclipses and only 13 of those have been total.  In 2012 I witnessed a solar eclipse in northern California.  It was a cool thing to see and photograph, but it was not total.   It was an annular eclipse (image below), where the moon is just a little too far away to block the entire disk of the sun.  If you didn’t know, the moon varies in distance as it journeys around the earth.  That is, its orbit is elliptical.

Annular eclipse as viewed from Sacramento, CA in May, 2012.

There is no question I will make every effort to see this solar eclipse, and I strongly recommend you do as well.  After all, it’s the first total solar eclipse in the mainland U.S. since 1979 (Hawaii had one in 1991).  The next one in North America is in 2024 (Mexico, U.S. and Canada).

Each total solar eclipse has a unique character, partly due to location and partly the precise nature of the alignment.  They are too special to pass up when the opportunity arises.  Once you’ve seen one you have some idea why some people make a life of chasing them.  So any solar eclipse is worth seeing.  But it is very rare that they limit themselves to a single country.  This one does.  It’s America’s eclipse.

Images do not do justice to the sight of a total solar eclipse. This is in the western Pacific in 2009, during 6 minutes 39 seconds of totality, the longest solar eclipse until 2132!

The Path

The 2017 eclipse, unlike 1979s which only hit the Pacific Northwest, will cross through America’s heartland.  Granted, the first and last people to see it will be in boats far out in the Pacific and Atlantic Oceans respectively.  It begins at sunrise far north of the Hawaiian Islands and ends at sunset south of the Cape Verde Islands in the eastern Atlantic.

Despite the fact that over half of its path lies over ocean, this eclipse will not approach very close to any island.  Lucky for us, the central half of its path, including the point of maximum duration, passes over land.  It will be visible over a wide variety of landscapes, from densely urban to agricultural to coastline to ruggedly mountainous.  The path graces quite a number of the country’s national parks as well as other natural areas.

The moon’s shadow first hits land on the Oregon coast.  At about 10:15 in the morning towns from Pacific City south to Waldport will be plunged into darkness.  Little Depoe Bay is on the path’s centerline, and so is the summit of Mt. Jefferson, one of the high Cascades.  After crossing Oregon and southern Idaho, the shadow passes over the southern part of the Grand Tetons in Wyoming and then speeds out into the Great Plains, crossing Nebraska and Kansas.

A number of cities are either near or in the path of totality.  Residents of Kansas City and St. Louis will see it.  The shadow continues on to Kentucky, passing over beautiful Land between the Lakes.  It then bisects Tennessee, gracing the Music City, Nashville with the show.  The shadow then glides over one more national park, Great Smoky Mtns., before heading out over the Atlantic at the port of Charleston, South Carolina.  It leaves U.S. soil just before 3 in the afternoon local time, having taken just over an hour and a half to traverse the continent.  For a very nicely done interactive map of the eclipse’s path, check out this site.

I hope I’ve gotten you excited about seeing this eclipse.  If you are already an enthusiast you’ve undoubtedly already made plans.  If not, don’t worry that it’s too late to plan a trip.  If there is a will there is a way.  If you’ve never seen one, and especially if you live in North America, there really is no excuse.  Just see it!  So now that we’ve taken care of the why, next time we will get down to the how and the where, the nuts and bolts of seeing the great American Eclipse of 2017!

The silhouetted moon near the end of an annular eclipse.  Note the diffraction effects, especially along the upper left limb of the sun.

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4 responses to “Eclipse Mania: Are you In?

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  1. I so want to do this! It just happens to fall on one of the worst days work-wise, but I’m going to try to finagle my way out of work at all costs. Where I live in North Florida, the sun is supposed to be about 90% eclipsed. Would that still be an impressive sight? Here’s hoping I can sneak up to the Carolina mountains for the event. 🙂

    • You should do it Blake! Sorry to say that 90% won’t cut it. You have to be under the path of totality, preferably as close to the centerline, to see the show properly. If you’re not under the totality path you won’t be able to watch it with your naked eyes. Total and partial eclipses are literally like night and day. So sneak up to the Carolinas.

  2. The path goes directly over St. Louis, where I live. No excuse not to see it.

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