On Phys.org, David Dickinson highlights next year’s total eclipse. But at the end of his article, he notes that a total eclipse is just a “happy celestial circumstance” instead of a product of intelligent design.
On August 21, 2017, the umbra (the Moon’s shadow on Earth where the Moon completely covers the Sun) of the solar eclipse will move across the United States, tracing a path from Oregon to South Carolina, lasting about two minutes.
In their book, The Privileged Planet: How Our Place in the Cosmos Is Designed for Discovery, astronomer Guillermo Gonzalez and philosopher Jay Richards explain that total eclipses were monumental in science: Einstein’s theory of relativity predicted that gravity bends light and would therefore make stars near the Sun appear at different locations than they actually were during an eclipse — and astronomers observed it. The corona and chromosphere, the light that appears around the edges of the Moon when it is covering the Sun, reveals facts about the atmosphere of the Sun.
They note that observation of a total eclipse requires two elements: the right planetary and celestial conditions for a total eclipse, and a planet hospitable to complex life such as ourselves. Gonzalez and Richards conclude that “our place in the cosmos is designed for discovery.”
Dickinson takes a stab at that argument:
The sun is about 400 times larger than the moon in diameter, but the moon is 400 times closer. We’ve actually heard this fact tossed out as evidence for intelligent design, though it’s just a happy celestial circumstance of our present era. In fact, annular eclipses are now slightly more common than totals in our current epoch, and will continue to become more so as the moon slowly recedes from the Earth. Just under a billion years ago, the very first annular eclipse of the sun as seen from the Earth occurred, and 1.4 billion years hence, the Earth will witness one last brief total eclipse.
It’s true. There is a limited time period in which solar eclipses are visible. Gonzalez and Richards acknowledge this — and actually take it a step further. Not only is the Moon receding, but the Sun is getting bigger. But this does not refute the case for design — in fact, it amplifies it:
These two processes, working together, should end total solar eclipses in about 250 million years, a mere 5 percent of the age of the earth. This relatively small window of opportunity also happens to coincide with the existence of intelligent life. Put another way, the most habitable place in the Solar System yields the best view of solar eclipses just when observers can best appreciate them.
So what is it about the ratio between the sizes of the Sun and the Moon, and the distance between the Moon and Earth, that is so fit not only for eclipses but also for human life?
First, the star. Gonzalez and Richards note that it must be similar to our own, saying:
There are good reasons to believe that a star similar to the Sun is necessary for complex life. A more massive star has a shorter lifetime and brightens more rapidly. A less massive star radiates less energy, so a planet must orbit closer in to keep liquid water on its surface. (The band around a star wherein a terrestrial planet must orbit to maintain liquid water on its surface is called the Circumstellar Habitable Zone.) Orbiting too close to the host star, however, leads to rapid tidal locking, or “rotational synchronization,” in which one side of the planet perpetually faces its host star. (The Moon, incidentally, is so synchronized in its orbit around Earth.) This leads to brutal temperature differences between the day and night sides of a planet. Even if the thin boundary between day and night, called the terminator, were habitable, a host of other problems attend life around a less massive star…
The Sun’s size is important for the habitability of Earth. The distance between the Earth and the Moon, as well as the size of the Moon, must be finely tuned to allow for life. Gonzalez and Richards note:
If a planet’s moon were farther away, it would need to be bigger than our Moon to generate similar tidal energy and properly stabilize the planet. Since the Moon is already anomalously large compared with Earth, a bigger moon is even less likely. A smaller moon would have to be closer, but then it would probably be less round, creating other problems.
Mark your calendar for the 2017 eclipse; I’m certainly planning to go. But humans won’t be observing it due to chance or determinism.
Rather, a designing intelligence evidently had in mind to make a habitable planet hospitable to scientific discovery — and total solar eclipses seem like a very elegant part of this cosmic and terrestrial symphony.