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Equinoctial hours
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Equinoctial hours
An equinoctial hour is one of the 24 equal parts of the full day (which includes daytime and nighttime).
Its length, unlike the temporal hour, does not vary with the season, but is constant. The measurement of the full day with equinoctial hours of equal length was first used about 2,400 years ago in Babylonia to make astronomical observations comparable regardless of the season. Our present hour is an equinoctial hour, freed only from its seasonal variation and from the small error due to some uniform Earth rotation[clarification needed], and realized by modern technical means (atomic clock, satellite and VLBI-Astrometry).
When the temporal hour was used, the daytime and nighttime, whose lengths vary greatly throughout the year, were each divided into 12 hours. This corresponded to the earlier sentiment and custom of not grouping the night with the daytime.
The name equinoctial hours refers to the fact that the temporal hours of the daytime (daylight hours) and those of the night are of equal length at each of the equinoxes.
Equinoctial hours (Ancient Greek: ὥραι ἰσήμεραι, romanized: hōrai isēmerai) are found, in distinction to the Greek: ὥραι καιρικαί, romanized: horai kairikai, the 'unequal' hours, at least in Ancient Greece.
Geminos of Rhodes reported the observation of Pytheas of Massalia that the duration of the night depended on the geographical latitude of the place in question. However, it is not clear from his explanations whether he meant equal or equinoctial hours. Otto Neugebauer cites this account as the oldest testimony to the concept of hour (¹ra)[clarification needed] as a defined measure of time.
The Babylonian calendar knew no division of the day into 24 time units, so Ancient Egyptian influence for this system can be considered probable. The period of its origin can be dated to the 4th century BC, since Pytheas of Massalia refers to the terminus[clarification needed] G¨j perÐodoj introduced by Eudoxus of Cnidus.
The use of equinoctial hours was already familiar in the work of Hipparchus of Nicaea. In the appendix to his commentary on Aratos of Soloi and Eudoxos of Knidos, he uses the well-known 24-hour circles and names stars whose rises are separated from each other by about one equinoctial hour in certain seasons.[citation needed]
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Equinoctial hours AI simulator
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Equinoctial hours
An equinoctial hour is one of the 24 equal parts of the full day (which includes daytime and nighttime).
Its length, unlike the temporal hour, does not vary with the season, but is constant. The measurement of the full day with equinoctial hours of equal length was first used about 2,400 years ago in Babylonia to make astronomical observations comparable regardless of the season. Our present hour is an equinoctial hour, freed only from its seasonal variation and from the small error due to some uniform Earth rotation[clarification needed], and realized by modern technical means (atomic clock, satellite and VLBI-Astrometry).
When the temporal hour was used, the daytime and nighttime, whose lengths vary greatly throughout the year, were each divided into 12 hours. This corresponded to the earlier sentiment and custom of not grouping the night with the daytime.
The name equinoctial hours refers to the fact that the temporal hours of the daytime (daylight hours) and those of the night are of equal length at each of the equinoxes.
Equinoctial hours (Ancient Greek: ὥραι ἰσήμεραι, romanized: hōrai isēmerai) are found, in distinction to the Greek: ὥραι καιρικαί, romanized: horai kairikai, the 'unequal' hours, at least in Ancient Greece.
Geminos of Rhodes reported the observation of Pytheas of Massalia that the duration of the night depended on the geographical latitude of the place in question. However, it is not clear from his explanations whether he meant equal or equinoctial hours. Otto Neugebauer cites this account as the oldest testimony to the concept of hour (¹ra)[clarification needed] as a defined measure of time.
The Babylonian calendar knew no division of the day into 24 time units, so Ancient Egyptian influence for this system can be considered probable. The period of its origin can be dated to the 4th century BC, since Pytheas of Massalia refers to the terminus[clarification needed] G¨j perÐodoj introduced by Eudoxus of Cnidus.
The use of equinoctial hours was already familiar in the work of Hipparchus of Nicaea. In the appendix to his commentary on Aratos of Soloi and Eudoxos of Knidos, he uses the well-known 24-hour circles and names stars whose rises are separated from each other by about one equinoctial hour in certain seasons.[citation needed]
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