by Mary Tyrer

Created on: June 15, 2008   Last Updated: September 17, 2008

A solstice happens two times within a year. However, there a Summer Solstice and a Winter Solstice, and there are two equinoxes. To understand the difference details of both need to be explained in order to understand why and how they are different.

The Summer Solstice is the first day of summer and the longest day of the year. On June 21st in the northern hemisphere the sun is the farthest north and the length of time between Sunrise and Sunset.

An equinox happens two times a year, once on the first day of spring and at the beginning of a long period of sunlight at the Pole. In the northern hemisphere: March 20 when Sun crosses the Equator moving north. In the southern hemisphere this will happen on September 22 when the Sun crosses the Equator and moves south. This is considered to be the spring equinox.

The autumn equinox happens the first day of fall or autumn. This begins a long period of darkness at the Pole. In the northern hemisphere it begins on September 22nd when the Sun crosses the Equator moving south. In the southern hemisphere it begins on March 20th when the Sun crosses the Equator and moves north.

The Solstices

Now to define the differences, there are a few other explinations that will help to understand why the equinox's and the solstices have even more meaning. During an equinox when the Sun is crossing the celestial equator both day and night are equal in length of time. An equinox unlike the summer or winter solstice will not always happen on the same day of the year. This is because a year is in reality 365.25 days long. This is also why leap year occurs every four years. The calander will add a day every four years to correct the calendar days of a year. As most already know a leap year has 366 days a day is added to February to make up the for the .25 portion of the day not accounted for on the calendar.

Midsummer Day is June 24 (each year) and is one of the four Quarter Days in the Legal Calendar. The other Quarter Days are Lady Day (March 25), Michaelmas (29 September) and Christmas Day (25 December).

According to Kepler's Law, the Earth does not orbit the sun in a complete circle, it does so at an eclipse. Knowing it orbits in eclips instead of a complete circle shows that the Earth will be closer to the sun during a point of completion of its' orbit. When the Earth is closest to the sun, it moves at a higher rate of speed and this will cause the sunrise and sunset to be at different times. The same will happen in some the Earth will be further from the sun and will move slower, this will vary the time of sunrise and sunset. The unequal motion will cause variations in the length of the solar day and in the times of sunrise and sunset.

Learn more about this author, Mary Tyrer.
Click here to send this author comments or questions.