Things Ain’t What They Seem to Be

I recently read an intriguing book on astronomy, written way back in 1985. One must be cautious about reading an astronomy book that’s nearly 25 years old—there have been a multitude of new discoveries since then. Stellar knowledge quickly becomes outdated. But archaic sky watching was exactly the subject of this book: Astronomy and the Imagination by Norman Davidson.

The book appealed to me, because it describes the cosmos as the ancients saw it: from an Earth-centered perspective. That’s very passé… but wait, it’s how we see it too, when we look up with our naked eye. The ceaseless march of science (along with its amazing telescopes) has helped us to retire the old idea that the Earth is at the center of the universe. This is a belief that the church had seized upon, and like a dogmatic bulldog, didn’t want to let go. A few folks even suffered for their revolutionary ideas to the contrary.

From 400 years of advances in astronomy we know that our beautiful little planet circles the sun, which circles the Milky Way’s center, which is pushed and pulled by countless other galaxies. In fact, there may be no definite center! And yet, when we sit down at night (or I repose in my outdoor tub) and gaze at the sky for awhile, we have the same experience that our ancestors did: the Earth does not seem to move, while everything out there seems to revolve around us. We still perceive ourselves to be at the center of the universe. Intellectually we know it’s an illusion, but it’s what we see, it’s what we experience.

This experience has three qualities to it, as described by Davidson: (1) we perceive the sky as a dome above us, (2) the dome meets the “flat” Earth at the horizon, and (3) the observer is at the center of it all. We also have the illusion that the stars are projected onto that dome; they all appear to be the same distance away. In fact, since the stars directly overhead appear closer to us than those near the horizon, that dome is more like a flattened bowl. The same illusion occurs in the daytime, as clouds near the horizon seem to be farther away than those above.

The flattened-bowl illusion may be why we think the full moon, when we see it near the horizon, seems larger than when it climbs higher in the sky. We unconsciously expect the moon to be smaller when it’s close to the horizon, since everything seems to be farther away there. But our objective eye says it’s the same size, so our subjective brain compensates and tells us it must be larger. There are other theories why this illusion occurs—some even having been put forth by the ancient Greeks. Here we are in the 21st century and we’re still not sure why the full moon seems so fat when it first rises. Why? Because our mind’s eye is so complex and elusive.

So we’re in this fascinating place today, when we view the sky with our naked eye: although we know so much about the universe, we still visually experience it the same way our distant ancestors did. May we not lose their wonder of it all.