Astronomical Events Determine Easter Observance

The motion of the heavens is a precise clock and calendar that can be used to determine when to celebrate special events. One doesn’t have to observe the sky for too long a period of time to notice the cyclic phases of the Moon, or the changing position of the Sun relative to the horizon over the course of a year.

It should therefore not be surprising that many religions celebrate special events that are connected to the clockwork of the heavens. For instance, Christians celebrate Easter every year, but the date for the celebration changes. Since we can barely even remember birthdays and anniversaries that always occur on the same date, it’s time for me to enlighten you with the facts of how the date of Easter is determined.

Think back to Easter celebrations of years past. Was it cold or snowy and you had to bundle up? Or, were spring outfits proudly worn amidst warming sunlight and returning songbirds? Why these extremes of weather? Well, if the date for the celebration of Easter occurred on the same Sunday every year, our fickle New England weather could easily account for the differences in attire.

However, in some years Easter can occur as early as March 22 or as late as April 25. Why this range? The varying date for the observance of Easter is determined by astronomical circumstances. And in 2012 Easter is celebrated almost midway between these two dates, on April 8.

The story began many moons ago when the Christian Church first developed. Since this holy day was determined in conjunction with Passover, Easter often fell on a weekday. However, in 352 A.D. the Council of Nicaea declared that it should always fall on a Sunday. They determined that Easter would fall on the first Sunday after the Full Moon on or next after the vernal equinox (spring... March 20 or 21). However, if the Full Moon occurs on a Sunday, Easter is celebrated on the following Sunday. This scenario happened in 2001.

This year the vernal equinox was on Tuesday, March 20, at 1:13 am, EDT. The Full Moon on or after that date occurs on Friday, April 6 (also Good Friday). Therefore, Easter is celebrated on Sunday, April 8.

People aren’t as observant of sky happenings these days as they once were long ago. Light pollution in and surrounding urban areas has blocked all but the brightest stars and planets from view. The Milky Way galaxy, our own island universe, can now be seen to best advantage only from dark rural skies.

Let’s not lose our connection to the stars from which we were born. Proper lighting can promote safety if effectively installed. Keeping stray light from polluting the night sky will allow starlight to shine down from the heavens. Then maybe folks will begin to notice and appreciate the beauty of the starry heavens once again.

Have a happy Easter, and remember to keep your eyes to the skies!

April Meteor Shower

I haven't written about the April Lyrids for a few years now because the shower had been in decline, and the observing conditions were always poor to fair at best. Well, this year the shower peaks at around midnight on the night of April 21-22, and, best of all, the Moon will be New and will not blot out any of the meteors.

The Lyrids appear to radiate outward from an area of sky on the Lyra and Hercules border, which will be about 45 degrees (halfway between the horizon and zenith) above the eastern horizon at midnight and well placed for observing.

These swift and bright meteors disintegrate after hitting our atmosphere at a moderate speed of 29.8 miles per second. They often produce luminous trains of dust that can be observed for several seconds. Predicting the peak number of meteors per hour for this shower would be guesswork at best.

However, unless something unusual happens, you can perhaps expect to see about a dozen meteors during the peak time if you observe well away from city lights.

Good luck. We can only hope that clouds and rain showers won’t spoil the view.

David A. Huestis

David Huestis
David Huestis
Entry Date:
Apr 1, 2012
Published Under:
David Huestis's Columns
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