AMHERST, Mass. – The public is invited to witness sunrise and sunset associated with the spring equinox among the standing stones of the UMass Amherst Sunwheel on Friday, 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 gatherings, which have attracted more than 10,000 visitors over the past 17 years, UMass Amherst astronomer Christopher Thibodeau will discuss the astronomical cause of the sun’s changing position during the hour-long gatherings. He will also explain the seasonal positions of Earth, the sun and moon, and answer questions about astronomy.
The exact time of the vernal equinox this year is 6:45 p.m. Eastern Daylight Time on March 20. This ushers in the beginning of spring and is also the day the sun rises into the sky to be visible for six months as seen from the North Pole, and the day it sets for six months as seen from the South Pole.
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 observers, except those at the North and South Poles, the sun on the equinox (for equi, “equal” and nox, “night”) rises due east and sets due west and stays up for 12 hours and down for 12 hours. From the Sunwheel in Amherst, observers standing at the center of the standing stones see the Sun rise and set over stones placed to mark the equinoxes.
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.