
This is another installment in a series that has been adapted from my 11-part CD teaching series on A. W. Tozer’s spiritual classic, The Pursuit of God.
“Be thou exalted, O God, above the heavens; let thy glory be above all the earth.” (Psalm 57:5)
Before the days of Global Positioning Satellite devices, ships on the open sea could only ascertain their exact location by using a sextant and a chronometer. The instruments we use today differ little from the ones available to Columbus and Magellan.
A sextant is composed of two tubes, each resembling a telescope and joined with a hinge. Each tube must be sighted on something fixed. For instance, one tube could be sighted on the waterline and the other tube sighted on the top of a mountain. When the two images converge in the eyepiece, the operator locks in the hinge and reads the exact angle off the sextant. With some basic geometric calculations the user can determine the height of a mountain or the distance from the ship to land. Thus, a ship sailing near a shoreline is able to determine its exact location.
However, it is a different matter for a ship sailing beyond the sight of land. In open water, there are only two things that are fixed: the horizon at all times and a certain star at a given time. On a clear day, the horizon is the only fixed point available, for no stars can be seen. And on a clear night, a star provides the only fixed points available, but the horizon can no longer be seen. The only time that both the horizon and a particular star are visible is during two brief moments: one at dawn and the other at dusk.
Just before dawn, the navigator fixes one tube on a visible star and waits. As the rising sun begins to illuminate the horizon, the navigator fixes the other tube on the line between earth and sky. He must be ready, for both are only visible for one brief instant. When the sailor has them sighted, he then locks in the hinge, reads the precise angle on the sextant, notes the exact time, and consults a chronometer for that particular star, at that particular time, according to that particular angle. Thus the position of the ship can be precisely known, because at only one place on earth can that angle to that star be measured at that particular instant in time.
The process would be reversed at dusk. This time the crewmember would first fix one tube on the horizon, sharp as a ruler’s edge, and wait for the first star to appear. As soon as it was sighted, the other tube would be focused on the star, the mirror that converged the two images flipped down, the hinge locked in, the angle read, the time noted, and the chronometer consulted for position.
All during the day the horizon was clearly visible and all during the night the stars looked close enough to reach out and touch. But only as day was fading into night, and again as night was dawning into day, could heaven and earth be brought together. Thus each day, twice a day, an ocean-going ship could stay on course by means of celestial navigation.
• We learn to navigate by fixing our gaze on something that does not move.
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