The Rites of Spring, the Vernal Equinox

The planetarium show will explore the astronomical events associated with the first day of spring and will demonstrate how the position of the equinox has changed over the millennia with respect to the fixed stars. The vernal equinox which is both a time and a direction in space is called the first point of Aries. Come find out how the Vernal Equinox got to be in Pisces now and when last it was in Aries.  Help us celebrate Noruz the oldest continuously celebrated human holiday. The Vernal equinox was in Taurus when this celebration began 5,000 year ago. Find out when we will really enter the age of Aquarius, when the Vernal Equinox is in Aquarius.

Noruz in the Wikipedia.

Calculating Easter from the Vernal Equinox: The date of Easter from the USNO astronomical applications.  Easter controversy from the Catholic Encyclopedia.

Length of the Seasons:
Winter: 88 days 23 hours 54 minutes
Spring: 92 days 18 hours 26 minutes
Summer: 93 days 15 hours 29 minutes
Autumn: 89 days 89 days 20 hours

Three main types of years
Mean Tropical year: 365 days 5 hours 48 minutes 46 seconds = 365.2422 days
Sidereal year: 365 days 6 hours 9 minutes 10 seconds = 365.2564 days
Anomalistic year from perihelion to perihelion:  365 years 6 hours 13 minutes 53 seconds = 365.2596 days
Greater discussion of types of years in the Wikipedia.

Pope Gregory XIII calendar reform October 5, 1582 = October 15, 1582.
Current Gregorian calendar system 365.2425 days per year will have only a one day error in 3,300 years.  Currently the Gregorian calendar has a leap year every 4 years except on the century boundary unless the century boundary are divisible by 400 so 1700, 1800, and 1900 are not leap years, but 1600 and 2000 are leap years.

Difference between Tropical year and Sidereal year is 20 minutes 24 seconds or approximately 20.5 minutes/year, because of precession.
Crude estimate of the precession time: 365.2422 days/20.5 minutes/year * 24 hours/1 day * 60 minutes/1 hour = 25,700 years.  

Nutation 9.2 seconds of arc/18.6 years of the obliquity of the ecliptic.

PowerPoint presentation shown 3-20-20006 as part of the planetarium show.

Fumocy, Full Moon Cycle in the Wikipedia.

Montgomery College's Planetarium home page

Web page by Dr. Harold Alden Williams.
Last changed 2:10PM on April 3, 2009.