The Astronomy of the Bible / An Elementary Commentary on the Astronomical References of Holy Scripture

by E. Walter Maunder

This is the legitimate use of the heavenly bodies, just as the worship of them is their abuse, for the division of time—in other words, the formation of a calendar—is a necessity. But as there are many heavenly bodies and several natural divisions of time, the calendars in use by different peoples differ considerably. One division, however, is common to all calendars—the day.

The "day" is the first and shortest natural division of time. At present we recognize three kinds of "days"—the sidereal day, which is the interval of time between successive passages of a fixed star over a given meridian; the apparent solar day, which is the interval between two passages of the sun's centre over a given meridian, or the interval between two successive noons on a sundial; and the mean solar day, which is the interval between the successive passages of a fictitious sun moving uniformly eastward in the celestial equator, and completing its annual course in exactly the same time as that in which the actual sun makes the circuit of the ecliptic. The mean solar days are all exactly the same length; they are equal to the length of the average apparent solar day; and they are each four minutes longer than a sidereal day. We divide our days into 24 hours; each hour into 60 minutes; each minute into 60 seconds. This subdivision of the day requires some mechanical means of continually registering time, and for this purpose we use clocks and watches.

The sidereal day and the mean solar day necessitate some means of registering time, such as clocks; therefore the original day in use must have been the apparent solar day. It must then have been reckoned either from sunset to sunset, or from sunrise to sunrise. Later it might have been possible to reckon it from noon to noon, when some method of fixing the moment of noon had been invented; some method, that is to say, of fixing the true north and south, and of noting that the sun was due south, or the shadow due north. Our own reckoning from midnight to midnight is a late method. Midnight is not marked by the peculiar position of any visible heavenly body; it has, in general, to be registered by some mechanical time-measurer.

In the Old Testament Scriptures the ecclesiastical reckoning was always from one setting of the sun to the next. In the first chapter of Genesis the expressions for the days run, "The evening and the morning," as if the evening took precedence of the morning. When the Passover was instituted as a memorial feast, the command ran—

"In the first month, on the fourteenth day of the month at even, ye shall eat unleavened bread, until the one and twentieth day of the month at even. Seven days shall there be no leaven."

And again, for the sabbath of rest in the seventh month—

"In the ninth day of the month at even, from even unto even, shall ye celebrate your sabbath."

The ecclesiastical "day" of the Jews, therefore, began in the evening, with sunset. It does not by any means follow that their civil day began at this time. It would be more natural for such business contracts as the hiring of servants or labourers to date from morning to morning rather than from evening to evening. Naturally any allusion in the Scriptures to the civil calendar as apart from the ecclesiastical would be indirect, but that common custom was not entirely in agreement with the ecclesiastical formula we may perhaps gather from the fact that in the Old Testament there are twenty-six cases in which the phrases "day and night," "day or night" are employed, and only three where "night" comes before "day." We have a similar divergence of usage in the case of our civil and astronomical days; the first beginning at midnight, and the second at the following noon, since the daylight is the time for work in ordinary business life, but the night for the astronomers. The Babylonians, at least at a late date in their history, had also a twofold way of determining when the day began. Epping and Strassmaier have translated and elucidated a series of Babylonian lunar calendars of dates between the first and second centuries before our era. In one column of these was given the interval of time which elapsed between the true new moon and the first visible crescent.

"Curious to relate, at first all Father Epping's calculations to establish this result were out by a mean interval of six hours. The solution was found in the fact that the Babylonian astronomers were not content with such a variable instant of time as sunset for their calculations, as indeed they ought not to have been, but used as the origin of the astronomical day at Babylon the midnight which followed the setting of the sun, marking the beginning of the civil day."

It may be mentioned that the days as reckoned from sunset to sunset, sunrise to sunrise, and noon to noon, would give intervals of slightly different lengths. This would, however, be imperceptible so long as their lengths were not measured by some accurate mechanical time-measurer such as a clepsydra, sandglass, pendulum, or spring clock.