Chasing the Shadow of the Moon

On August 21, 2017, the United States will be treated to a total solar eclipse that will be visible across the entire continent.  That hasn’t happened since 1918!  A solar eclipse happens when the moon passes between the Earth and sun, covering the sun and making the solar corona visible if you’re at the right location of total eclipse.  On August 21, the 70 mile-wide path of totality will sweep from Oregon to South Carolina in about 90 minutes.  Others will see a partial eclipse where the sun is partially covered by the moon.  A solar eclipse results in significant darkening during the day, especially at a location of totality where almost 3 minutes of deep dusk will occur during this eclipse.


Solar eclipses have been observed throughout human history, with existing records of eclipses as old as 4,500 years.  The ominous darkening of the sun during an eclipse has sometimes been interpreted as a sign or omen, usually negative.  However, our understanding of eclipses has increased steadily since the confirmation of the heliocentric solar system in the 1600’s.  And, eclipses have been extensively studied throughout the modern research period.  Let’s look at how our understanding of solar eclipses has developed as revealed using Web of Science Core Collection.


Searching Web of Science Core Collection for the topic “solar eclipse” yielded 1,995 scholarly publications.  The following chart shows the count by publication year for these documents.  Clearly, there’s been significant interest in eclipses throughout the 20th and 21st centuries.  Even in 1900 there was already a steady stream of papers.  As with most research areas, there’s been a dramatic increase in published research since 1970, and especially since 2000.  Another interesting feature is the periodic increases and decreases in publishing over time.  Many fields show a steady increase in scholarly activity over time, but eclipse research has had periods of higher and lower activity.  In part this may be due to variations in interest prompted by especially significant eclipses.  For example, an eclipse occurred very close to the sinking of the Titanic in 1912.  Eclipses in 1919 and 1922 were used to confirm Einstein’s general theory of relativity.  And an eclipse in 1970 was visible to many in North and Central America.  Coincidentally, these time periods showed peaks in eclipse research activity.

Examining the institutions sponsoring the authors of this eclipse research gives both expected and surprising insights.  The following is a list of the top 10 affiliations for authors of these 1,995 documents.  The US National Aeronautics and Space Administration (NASA)  has been the top publisher, which is certainly logical, but their lead is small.  A large amount of eclipse research has come from the Russian/Slovakian/Balkan region with almost 200 combined publications.  Only 1 independent academic institution is in the top 10, but it’s not one of the typical research powerhouses.  It’s Williams College, a small liberal arts school in Williamstown, Massachusetts!  Williams can thank prolific astronomy professor Jay Pasachoff, who’s published frequently in this area throughout his career.

Web of Science Core Collection
can also analyze the research areas of the publications.  The leading research areas are not surprising:  Astronomy, Atmospheric Science, Geology, Physics, Engineering.  However, 5% of the publications come from Social Sciences and Arts & Humanities.  These research areas include history, archaeology, literature, education, and general arts and humanities.  This shows that eclipses affect humanity in ways beyond the merely scientific, and Web of Science makes it easy to explore the many scholarly areas a topic finds its way into.


Getting more specific, we can ask what solar eclipse research has been the most impactful?  The following are the top 3 most highly cited papers in the result set with over 100 citations each.  These papers demonstrate the wide range of insights available from studying solar eclipses.  The 1970 Chimonas paper studied the effect of eclipses on our terrestrial atmosphere, the 1993 Spiller paper reported on equipment used for X-Ray imaging, and the 2007 Wang paper reported on a new feature of the sun’s corona revealed in more recent solar eclipse observations.  These papers provided the foundation for hundreds of later studies that can be easily explored using a true citation database like Web of Science Core Collection.




JOURNAL OF GEOPHYSICAL RESEARCH   Volume: 75   Issue: 4   Pages: 875-&   Published: 1970




JOURNAL OF APPLIED PHYSICS   Volume: 74   Issue: 1   Pages: 107-118   Published: JUL 1 1993



By: Wang, Y. -M.; Sheeley, N. R., Jr.; Rich, N. B.

ASTROPHYSICAL JOURNAL   Volume: 658   Issue: 2   Pages: 1340-1348   Part: 1   Published: APR 1 2007


So, as the denizens of North America journey to the path of totality and throw eclipse parties on August 21, know that researcher worldwide will be studying the eclipse and its effects on us.  Take advantage of the eclipse if you can.  Due to tidal friction, the orbit of the moon is increasing about 3.8 cm per year.  When it gets too far away to block the sun, total eclipses will no longer occur on the Earth’s surface.  And that will happen in just 600 million years.


For more information on the eclipse and how to enjoy it safely, see the special NASA website: .


Images courtesy the US National Aeronautics and Space Administration (NASA).

Header image: S. Habbal, M. Drunckmuller and P. Aniol