English Heritage will welcome people to Stonehenge to celebrate the Spring Equinox on Saturday 21st March.
The Spring Equinox at Stonehenge, England, United Kingdom is on Friday, 20th March 2015 @ 22:45 GMT, however as the astronomical timing is closer to midnight, managed open access will be on the next day (Saturday 21st March). This will be from first light (approximately 05:45am) until 08:30am.
What are Equinoxes?As the Earth travels around the Sun in its orbit, the north to south position of the Sun changes over the course of the year due to the changing orientation of the Earth's tilted rotation axes. The dates of zero tilt of the Earth's equator correspond to the Spring Equinox and Autumn Equinox.
Equinoxes occur when the axis of rotation of the earth (i.e. the line form the N to S poles) is exactly parallel to the direction of motion of the earth around the sun. This happens on just two days of the year, the spring and autumn equinoxes. This means that day length is exactly the same (12 hours) at all points on the earth's surface on these days (except right at each pole, where it will be about to change from permanent light to dark, or vice versa).
Where does the name Equinox come from?
The name is derived from the Latin aequus (equal) and nox (night), because at the equinox the night and day are nearly equally long.
The Spring Equinox
The Spring Equinox is the first day of spring season and occurs when the sun passes the equator moving from the southern to the northern hemisphere. The North Pole begins to lean toward the sun again.
Day and night have approximately the same length.
Spring Equinox is near 20th March.
Equinoxes do not always occur on the same day each year, and generally will occur about 6 hours later each year, with a jump of a day (backwards) on leap years.
Why do the equinoxes not always occur on the same day each year?
The reason is due to the time the Earth takes to go around the Sun and our calendar.
The Earth takes approximately 365.25 days to go around the Sun, yet our year is 365 days. Every 4 years, we have a leap year where another day is added to our calendar to make up for the 4 missing quarters. It is important to do this so that there is not a gradual drift of date through the seasons.
For the same reason the precise time of the equinoxes are not the same each year.
Stonehenge Tour Guide