|
by
Doug Ward |
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."
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On 03 May 2024, 16:05.
