Countdown to the Eclipse: Two Weeks Out!

Nearly everyone understands that a solar eclipse occurs when the moon passes between the sun and earth, blocking the sun’s light from reaching the earth. The sun is 400 times larger than the moon, but the sun is also 400 times farther away than the moon is. Therefore, the sun and moon appear nearly the same size in the sky, about ½ degree across. So, when the moon passes in front of the sun, it just barely covers the sun. And the path of totality, the region where the sun is completely blocked, producing a total solar eclipse is narrow—no more than 200 miles across, and often much narrower than that. For instance, the path of totality in August 2017 was only 70 miles across, and on April 8, the path of totality will be about 120 miles wide.

The moon and sun having the same apparent size in the sky makes for spectacular total solar eclipses. If the moon were a little smaller or a little farther away, there would be no total solar eclipses. If the moon were larger or closer to the earth, solar eclipses would be over total, which would not permit us to see the prominences and the inner part of the corona.

The sun and the moon having the same apparent size also results in total solar eclipses being rare. While a total solar eclipse occurs somewhere in the world about every year and a half, the path of totality is so small that only a relatively small part of the earth experiences each eclipse. Consequently, at any given location on earth, on average, it is about four centuries between total solar eclipses. To give you an idea of the rarity of total solar eclipses, the United States won’t experience another total solar eclipse for 20 years.

Other planets have natural satellites, or moons (at the time of this writing, the total number of known natural satellites in the solar system is nearly 300). Many of those natural satellites produce solar eclipses. For instance, some of the rovers on Mars have captured solar eclipses caused by Mars’ two small natural satellites. Here is a video of Phobos, Mars’ larger and closer natural satellite, passing in front of the sun as seen from the Martian surface. Notice that Phobos is too small and/or too far from Mars to completely cover the sun. Rather than an eclipse, it is more proper to call this a transit of Phobos in front of the sun. Most of the natural satellites of the solar system appear too small to produce total solar eclipses on their planets, resulting in transits. However, some of the larger natural satellites of other planets in the solar system appear much larger in the sky than the sun does, resulting in grossly over-total eclipses. A good example of this is the Galilean satellites, the four largest moons of Jupiter. Several times through a telescope I have watched the shadow of one of the Galilean satellites move across the face of Jupiter. But unlike on earth, these eclipses are not rare, and given how grossly over total they are, they aren’t spectacular either.

Throughout the solar system, only on earth do total solar eclipses combine rarity and spectacular appearance. And the earth is the only place in the solar system where this matters because only on earth are there humans to appreciate this fact. One could chalk this up as a fortunate coincidence, but how many coincidences is one allowed to have before one must realize that they are not coincidences at all? In many other ways, the earth is a wonderfully unique thing, not only ideally suited for our existence but also for us to enjoy.

These facts about eclipses, along with the incredible awe that total solar eclipses stir in people demonstrate that God is not only an exquisite engineer, but he is a very creative artist as well.

These facts about eclipses, along with the incredible awe that total solar eclipses stir in people demonstrate that God is not only an exquisite engineer, but he is a very creative artist as well. The experience of totality causes those who know God to reflect upon Psalm 19:1: “The heavens declare the glory of God, and the sky above proclaims his handiwork.”