AMHERST – The public is invited to witness sunrise and sunset associated with the spring equinox among the standing stones of the UMass Amherst Sunwheel on Sunday, March 20 at 6:45 a.m. and 6 p.m. These Sunwheel events mark the astronomical change of seasons when days and nights are nearly equal in length in the Northern Hemisphere.
At the hour-long gatherings, which have attracted more than 10,000 visitors over the past 18 years, UMass Amherst astronomers will discuss the astronomical cause of the sun’s changing position. They will explain the seasonal positions of Earth, the sun and moon, and answer questions about astronomy. A nearly full moon will be rising before sunset, and telescopes to observe both the sun and moon will be available at the evening session, weather permitting.
On the equinox, an observer located on the Earth’s equator will see the sun pass directly overhead at local noon, and that person will cast no shadow at noon. On any day other than the equinox, either the Earth’s Northern or Southern Hemisphere is tilted towards the sun. For someone at the North Pole, the equinox marks the start of six months that the sun stays above the horizon, and for someone at the South Pole it marks the start of six months of dark.
The exact time of the vernal equinox in western Massachusetts this year is 12:30 a.m. Eastern Daylight Time on March 20. This ushers in the astronomical beginning of spring when the sun rises due east and sets due west and stays up for 12 hours and down for 12 hours giving an “equal night,” which is the origin of the word “equinox.”
One of the most ancient spring equinox celebrations was observed by the Mayans at their main pyramid at Chichen Itza, Mexico. The main pyramid has a staircase built at such an angle that at the equinox, sunlight looks like a giant snake descending the stairs. From the Sunwheel in Amherst, observers standing at the center of the standing stones see the sunrise and set over stones placed to mark the equinox positions of the sun on the horizon.
The UMass Amherst Sunwheel is located south of McGuirk Alumni Stadium, just off Rocky Hill Road (Amity St.) about one-quarter mile south of University Drive. Visitors to the Sunwheel should be prepared for especially wet footing this year. Rain or blizzard conditions cancel the events. Donations are welcomed and will be used to help with the cost of additional site work at the Sunwheel and future events.
