On 21 August 2017, millions of Americans drove to a narrow strip of land across the continent where a total solar eclipse could be viewed—an event many termed “The Great American Eclipse”. Three CMI-US staffers were privileged to be able to travel to the zone of totality, and we were rewarded with a glorious sight in a cloudless sky, truly a once-in-a-lifetime experience.
From Oregon to South Carolina, people used special eclipse glasses to watch the moon slowly move in front of the sun over the course of about an hour, culminating in a few minutes of darkness during ‘totality’. The brief period where the moon completely blocks out the sun, leaving only the corona visible and resulting in what looks like twilight across the entire horizon. In the rest of the country, only a partial eclipse was visible.
In the ancient and medieval world, eclipses were thought to be portents of important events, often signifying impending disaster. Part of this fear was because many ancient pagan cultures worshipped the sun and moon as deities. There are also many different types of superstition surrounding eclipses (whether lunar or solar), such as thinking that it is harmful to an unborn child for his or her mother to view the eclipse. Such superstitions are, of course, baseless, though viewing the sun directly at any time, even when mostly covered by the moon, can cause permanent visual damage—to the viewer, not her offspring.
While only North America was treated to the solar eclipse this time, several more will occur in different parts of the world over the next decade. In 2023, parts of North and South America will be able to view an annular eclipse (see below), while the next year a total eclipse will be viewable from Mexico, the United States, and Canada. Australia and New Zealand will experience their next total eclipse in 2028.1
In fact, there is a total eclipse visible from somewhere on the earth approximately every 18 months.2
Types of eclipses
A solar eclipse happens when the moon comes between the earth and the sun, partially or completely blocking the sun’s light.3 If a solar eclipse happens when the moon is at its furthest point from the earth, the moon will appear smaller to us, and will not completely block the sun. This is called an ‘annular’ eclipse, sometimes called a ‘ring of fire’ eclipse, because the rim of the sun is visible behind the moon.4 If the moon is closer to us during the eclipse, the entire sun will be blocked. We call this a ‘total’ eclipse. A partial eclipse occurs when the sun and moon are not quite in the same line of sight, so the moon blocks only part of the disk. E.g. during the latest eclipses, people outside the zone of totality could view this. But they would not notice much darkening, even if 90% were covered.
A lunar eclipse happens when the earth comes between the moon and the sun. In this case, the moon passes through the earth’s shadow. Interestingly, since the earth’s atmosphere absorbs and refracts sunlight, the effect is to make the moon appear not black but red during a lunar eclipse.
There are several other differences between these two eclipse types. While a solar eclipse is only visible over a small portion of the earth, a lunar eclipse is visible to the entire hemisphere that is experiencing night-time. Also, solar eclipses can only happen during a new moon. Lunar eclipses can only happen during a full moon.
A unique view
Even though the sun is 400 times larger than the moon, they appear the same size when viewed from Earth because the sun is also 400 times further away. That is what makes a solar eclipse an amazing sight. If the moon or sun were only a little smaller or larger, or only a little closer or further away, the precise ratios that allow us to see the sun completely and perfectly blocked by the moon—but showing its chromosphere and corona—would not exist. The earth is the only planet from which one can view a perfect, total solar eclipse.5
This makes it rather unlikely that the earth and moon are billions of years old. The moon is slowly receding from earth at a rate of about 4 cm (1.5 in) per year. That in itself is an argument against the 4.6 billion-year alleged age of the earth-moon system;6 but if this recession had been happening for billions of years, for most of Earth’s history there would have been no annular eclipses, and in the distant future, all eclipses would be annular only. In a billions-of-years-old solar system, our epoch would therefore be the only time when the moon and sun were approximately the same size in the sky, which would be a rather curious coincidence.
Scientific importance of eclipses
Eclipses have enabled some important scientific discoveries. In 1868, Pierre Jules César Janssen looked at the sun’s corona with a spectroscope during an eclipse and saw a bright yellow line that did not belong to any then-known element. Later, this element would be named helium, from the Greek word for sun (ἥλιος, hēlios).7 During an eclipse, it is also possible to see stars that are supposed to be behind the sun. The sun’s gravity bends the light from those stars as the light passes close to the sun. This allows us to see just a little bit ‘behind’ the sun. This was a major confirmation of Einstein’s general theory of relativity.
Eclipses first made us aware of the sun’s ‘atmosphere’, including the chromosphere and corona. One mystery is how and why the corona is 1–3 million °C, far hotter than the sun’s surface temperature of 5,500°C. The solution seems to involve the sun’s powerful magnetic field.
Historical eclipses are also important. When an ancient document mentions an eclipse in a specific area, it is possible to know the exact time of the event to which the document refers. This helps us to reconstruct ancient history with greater accuracy. For instance, a solar eclipse in 585 BC, seen as an omen, caused the Lydians and Medes to make peace and end the war they had been waging.8
The heavens declare the glory of God
A total eclipse is a spectacular sight that draws people from hundreds (or even thousands) of miles away, for a phenomenon that lasts only a few minutes. David wrote, “The heavens declare the glory of God, and the sky above proclaims his handiwork” (Psalm 19:1). Even in the modern day when many people reject Scripture’s truth, a total eclipse is a powerful display of God’s glory.
References and notes
- Solar eclipses worldwide, timeanddate.com. Return to text.
- McClure, B., When’s the next U.S. total eclipse? earthsky.org, 22 August 2017. Return to text.
- Eclipse: Who? What? Where? When? and How?, eclipse2017/nasa.gov. Return to text.
- What is an annular solar eclipse? timeanddate.com. One of my colleagues vividly remembers seeing the annular eclipse of 15 January 1991 through his spectroscopic filters in New Zealand’s capital Wellington. Return to text.
- Carter, J., 9 things you should know about solar eclipses, thegospelcoalition.org, 21 August 2017. Return to text.
- Henry, J., The moon’s recession and age, J. Creation 20(2):65–70, 2006; creation.com/moonage. Return to text.
- Guglielmi, G., Three times scientists learned something from solar eclipses—and three times they were tricked, sciencemag.org, 17 August 2017. Return to text.
- Solar eclipses in history, timeanddate.com. Return to text.