Ward: The gift of solar eclipses


On April 8 I joined a crowd at Miami University’s intramural athletic field to watch the total eclipse of the sun. As the moon blocked more and more of the sun from view, the temperature dropped and shadows spread across the field. Applause erupted from the group when the sun disappeared completely at 3:08 PM.

Solar eclipses provide memorable experiences for casual observers like me, but they have been even more important for scientific research. During the few minutes of an eclipse’s totality, we can directly view the chromosphere and corona, the outer layers of the sun’s atmosphere. Scientists have made some major discoveries using observations gathered during these brief periods of time.

For example, during an eclipse on August 18,1868, French astronomer Pierre Janssen used a spectroscope to observe light from the chromosphere, producing evidence that the sun contains hydrogen gas. This launched a line of research that led to the discovery of the element helium and eventually to detailed information on the composition of the sun and other stars.

A second example involves Einstein’s theory of general relativity, which predicts that gravity bends light. Beginning in 1919, this aspect of the theory has been tested and verified repeatedly by photographs taken during solar eclipses.

Since solar eclipses can only be seen at precise times and places, knowledge of these times and places has helped us to estimate how the period of the earth’s rotation has changed over time. Such knowledge makes it possible to situate events from different points in history on a common timeline.

The existence of the solar eclipses that make this research possible is a blessing not to be taken for granted. Total eclipses occur because the sun and moon appear to us to be about the same size. The sun is about 400 times as large as the moon, but it is also about 400 times further away from us. Moreover, because the sun and moon have the same round shape and the moon has no atmosphere, we can see more of the sun’s chromosphere and corona during an eclipse than would be visible otherwise.

It turns out that we live in the best place in our solar system in which to watch an eclipse. In the book The Privileged Planet, astronomer Guillermo Gonzalez reports that the only other moon in the solar system appearing to be about the same size as the sun is Prometheus, a moon of Saturn. It would not be worthwhile, however, to travel to Saturn for an eclipse. First of all, the sun appears smaller in Saturn’s sky than it does in ours. Furthermore, Prometheus orbits Saturn much faster than our moon orbits Earth, leading to eclipses that last less than a second. In addition, Prometheus is not round, so its eclipses reveal less of the sun’s chromosphere.

To people of faith, all of this suggests that the cosmos may have been designed to give us on earth the greatest possible opportunity to observe and study the sun and stars. We are thus able to affirm, along with Psalm 19:1, that “the heavens declare the glory of God.”

Dr. Doug Ward is an elder at Church of the Messiah in Xenia and an avid reader.

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