Easter is a religious event, celebrated by Christianity and Judaism. But have you noticed that the Easter date changes every year? That is, it is a mobile date. And, after all, what does this have to do with physics? Look that:

The date of Easter is determined according to a formula that follows some astronomical events. That’s right. This calculation also influences other religious celebrations, but to understand how it happened we must go back a bit in history.

In ancient times, religious believed that the resurrection of Christ (celebrated at Easter) happened on a day near a full moon and near an equinox, which is when the sun crosses the equator and day and night have the same duration . Thus, the Nicaea General Council, the first conference of bishops of the Catholic Church, even when the Julian calendar was still used, created by the Roman Emperor Caio Júlio César, determined that: Easter always happens on the first Sunday after the first Full Moon occurs after the Spring Equinox in the Northern Hemisphere or Autumn in the Southern Hemisphere.

After some time, the Julian calendar started to present some problems and Easter ended up happening closer to the middle of the year. Then a reform was made in the calendar, which became Gregorian. From then on, the rule was defined as: Easter always happens on the first Sunday after the first full moon that occurs after 21 March. Thus, Easter never happens before March 22 or after April 25.

Although there are exact calculations of the date, where the “average” Moon is considered and not the actual Full Moon, among other algorithms, we can understand the rule following the example of the Easter date in this year of 2015. The first Full Moon after 21 March takes place on April 4, which is a Saturday, so the first Sunday will be April 5, the date of Easter.

Did you see how physics is present in everything? Keep following our blog and Happy Easter!