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Published: 2019-02-05 08:41:00
Updated: 2019-02-05 12:51:16
By Tony Rice, WRAL contributor/NASA Ambassador
Spring may be more than three weeks away on the astronomical calendar, but the spring festival begins Tuesday with a new year (4717) on the Chinese calendar.
There are essentially three types of calendars: lunar, solar and lunisolar. As the names suggest, they are based on the movements of the moon, the sun, or a combination of the two, through the sky.
The Gregorian calendar in use worldwide is a solar calendar, designed to align with the tropical year, or the time it takes the Earth to orbit around the sun, 365.2421896698 days on average. That nearly quarter day is accounted for periodically as with the addition of a leap day.
Lunar calendars, such as the Islamic calendar, follow the phases of the moon to determine months (this is where the word month comes from), 29.530588 days on average. The lunar calendar needs no adjustment because it is based on actual observations of the moon.
Lunisolar calendars, such as the Hebrew, Hindu and Chinese calendars, also focus on the phases of the moon to determine months. But with the synodic or lunar month being just shy of a day shorter than a “solar month”, an 11-day difference builds between a lunar year and a solar year. To bring the lunisolar calendar into alignment, an intercalary or leap month is added.
The Hebrew calendar adds a second month of Adar in the middle of its calendar. The Chinese calendar adds its thirteenth month as needed to ensure the spring festival doesn’t drift into winter. The last Chinese leap month began on October 24, 2014 with the end of month nine and beginning of intercalary month nine.
The next will be added after month four in 2020.
Beginning the new year in February may seem a bit arbitrary, but astronomically speaking, it is the Gregorian calendar that is unusual.
This calendar starts in January, not because of any astronomical or religious significance, but because of a political one. Julius Caesar marked Jan. 1 in his Julian calendar to align with the Roman equivalent of inauguration day. In the 1500s, Pope Gregory would cement January’s starting position in his Gregorian calendar that we continue to use today ending England’s late March new year celebrations.
The Chinese calendar and its attempt to begin the year closer to spring aligns better with the definition of a topical year which is measured from vernal equinox to vernal equinox. Regardless of the calendar you keep, the vernal equinox will arrive Wednesday, March 20, at 5:58 p.m. eastern.