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Total eclipse of the brain

Why the 2017 solar eclipse proves the earth is not flat



The Great American Eclipse of 2017 is already one of the most talked-about scientific events of recent memory, and it hasn’t even happened yet. But what is a Christian supposed to make of this? Does not astronomy, with its assumed millions and billions of years, challenge our faith? In this case, absolutely not.

It comes as a surprise to many, but astronomy as a science has long been associated with Christian scholarship and was strongly supported by the Medieval church. Cathedrals were turned into solar observatories and many observations of astronomical events were catalogued. After the Reformation, enough data had been collected for scientists, many of whom were faithful Christians like Johannes Kepler, to conclude that the earth went around the sun. You read that right; it was the work of faithful scientists that led to the rejection of the old geocentric model of the universe.

The belief that the universe was created by God is extremely important for these developments. The Bible describes God as omnipotent, omniscient, and never-changing. If God created the universe, He would not create a universe that operated against His very nature. No, thought these early scientists, He would make the universe to act in ways that were consistent with His nature. The Ultimate Lawgiver would have created a universe that operated according to law. This thought was the spark that led to the discovery of the many scientific laws we know today. But we had to engage our minds to discover these things. As Kepler said of his work, “It was like thinking God’s thoughts after Him.”

NASA, A.T. SinclaiSE2017Aug21T
Figure 1: This animation shows the path of the eclipse across North America. Notice how the shadow morphs as it adjusts to the spherical shape of the earth. The small zone of totality is shown by the small black dot. It also morphs as it adjusts to the shape of the earth, but you would have to zoom in much closer to see the effect. It requires a very specific set of circumstances to produce this effect. Can you figure out what they are?

And yet, many people today do not know about the Christian underpinnings of modern science. Worse, many people, thanks to the unfiltered influence of the Internet, have left reason behind and rejected the scholarship of those who have gone before. Case in point: flat earth theory has risen from the grave over the last few years.

As a fun exercise, we can use the August 2017 solar eclipse to easily test the flat earth model. A lot of people write to us asking why we bother with these people. But there is one, clear reason to address this: we do not want anyone else to fall into the flat-earth error. To do so means to turn off one’s brain, to reject the scholarship of all of Christian history, and to make a mockery of the Bible. This is a serious matter.

But, let’s get back to our exercise. The maximum diameter of the moon’s shadow (the zone of totality, represented by the small black dot) will be 114 km, at Carbondale, IL. The shadow covers much less than 1% of the lit portion of the earth (Figure 1). The shadow will also move quite fast, over 4,000 km/hr (2,400 mi/hr) when it appears in Oregon, and it will be moving more slowly in the middle of the United States than it will be at either coast.1 But there is also a large zone where only a portion of the sun will be hidden (the gray area, called the penumbra) that moves along with the zone of totality. What would it take to create this situation?

To answer this, we are going to have to assume that the moon (not usually visible during the day) is the thing getting in the way of our view of the sun. Many flat-earthers say there is something else up there that is blocking the sun, but think about it: we can track the moon throughout the month, and we know where it should be when the eclipse happens. Guess what? It should be in the same place in the sky where the sun is.

The flat-earth myth is a strange, convoluted thing, but clearly the moon cannot be the same size as the sun. If it was, it would then block out the entire sun across the entire earth. Yet, the moon appears to be the same size as the sun. To appear the same size as the sun to an observer on the earth, the moon has to be somewhere within the dotted lines of Figure 2. And it must be closer to us than the sun. Yet, if the moon is too close, the shadow would be too small, and if it were too far away, the shadow would be too large.

Figure 2: The flat-earth ‘model’ cannot successfully explain solar eclipses. First, the sun and moon appear to be the same size to an observer on the earth at the place where the dotted lines come together. The moon must be somewhere between those two lines. But, the size of the shadow will be a mere 114 km at its maximum extent during the Aug 2017 eclipse. In order to generate a shadow that size, and to appear the same size as the sun, the moon has to be very close to the earth and very small: 12.5 km away and 0.13 km in diameter. This simply cannot be true, so the flat-earth ‘model’ must be wrong.

According to most flat-earth adherents today, the sun is only 5,000 km (3,000 miles) away. To explain both the apparent size of the moon and the observable size of its shadow, there is only one place it could be in the flat-earth model: the “dual-constraint lock point” in Figure 2. It turns out that the moon must be only 12.5 km (7.5 miles) above the earth! And its diameter must be only 0.13 km (about 427 feet)!

Friends, this is not true! Don’t get sucked into the flat-earth nonsense.

Note that we have not dealt with the speed of the shadow (approximately twice as fast as the speed of the sun and moon across the sky), nor the direction of the eclipse shadow (the sun moves in the opposite direction), nor the size of the penumbra. All three of these are exactly consistent with geokinetic (i.e., ‘the earth moves’) model of the solar system that includes a spherical sun, moon, and earth at great distances from each other. I suspect each also contradicts the flat earth ‘model’, but I will leave this fun exercise to others.

But what is the true situation? With some careful reasoning and some observational evidence from a lunar eclipse, Aristarchus of Samos (who died in 230 BC) demonstrated that the earth must be 3.7 times the diameter of the moon (the true value is 3.668).2 This was brilliant work and shows us how careful reasoning and careful observation can be used to figure out some amazing things. From similar experiments over many centuries, we know the distance to the moon and the sun, as well as the size of the sun. The sun is about 1,400,000 km (860,000 mi) in diameter and about 150 million km (93 million miles) from us. The moon is much closer (1/400th the distance), but also much smaller (1/400th the size). This is the reason why the moon appears the same size as the sun. Is this an amazing coincidence, or amazing design?

Figure 3: A 10th century Greek copy of the work of Aristarchus where he is discussing the relative sizes of the sun, earth and moon. In this diagram, the sun is to the left, the earth is in the center, and the moon is to the right and moving through the earth’s shadow.

We cannot tell you what to think, but we can encourage you how to think. We are commanded to study, to think, and to defend our faith. This is one example of how careful study leads to good conclusions that are consistent with our faith and observational science.

Figure 4: The geometric situation that causes solar eclipses has been known for millennia and is the result of critical thinking and careful experimenting.

Get out there and study God’s world, and don’t have a total eclipse of the brain.

Published: 19 August 2017

References and notes

  1. eclipse2017.org/blog/2016/11/27/how-fast-is-the-shadow-moving-across-the-us-during-the-eclipse. Return to text.
  2. eg.bucknell.edu/physics/astronomy/astr101/specials/aristarchus.html. Return to text.