Primitive Astronomical Notions

Primitive Astronomical Notions
On the astronomical side the most obvious fact is the division of time into periods of light and darkness by the apparent motion of the sun about the earth.

With closer attention it must soon have been observed that the relative length of day and night gradually changes, and that this change is attended by a wide range of remarkable phenomena.

At the time of shortest days, vegetable and animal life (in the north temperate zone) is checked by severe cold.

With gradually lengthening days, however, snow and ice sooner or latter disappear, vegetable is revived birds return from the warmer south, all nature is revived, birds return from the warmer south, all nature is quickened.

The longest days and those which succeed them are a period of excessive heat and of luxuriant vegetation, followed by harvest as the days shorten, towards the completion of the great annual cycle.

In time, closer observers, noting the stars, discovered hat corresponding with this great periodic change are gradual variations in the starry hemisphere visible at night, that in other words the sun’s place among the stars is progressively changing, that it is in fact describing a path completed in a large number of days, which after many years of counting is found to be 365.

It is also found that the midday height of the sun above the southern horizon shares in the annual cycle.

The determination of the number of days on the year is a matter of very gradual approximation, possible only to men who have already attained some command of numbers and the habit of preserving records extending over a long series of years.

For there is now well marked beginning of the year as of the day.

An erroneous determination of the number of days becomes apparent only after a number of years increasing with accuracy of the original approximation.

Still another natural period is introduced by the motion of the moon, which seems like the sin to have a daily motion about the earth, and also to describe a closed path among the stars in a period of about 29 days.

Unlike the sun, however, the moon has during this period a remarkable change of apparent shape and luminosity from “new” to “full” and back again.

The difficulty of expressing the precise length of the month and the year in days, causing the imperfection of of early calendars, has on the other hand reacted to the advantage of mathematical astronomy by demanding more and and more precise both in observation and in the computation based on it.
Primitive Astronomical Notions