spring equinox
The sun rises over Stonehenge as druids celebrate the Spring Equinox at Stonehenge on March 20 2009 near Amesbury, Wiltshire, England.Photo by Matt Cardy/Getty Images

Around a 100 druids and pagans are expected to descend on Stonehenge tomorrow (20 March) to mark the first day of spring and the date of the vernal equinox, as it is known in the northern hemisphere.

Spring equinox
During an equinox, the Earth's North and South poles are not tilted toward or away from the Sun and the length of the day is the same at all points on Earth's surfaceWikipedia

The Earth will be perpendicular to the sun's rays (usually the Earth's axis tilt at an angle either away or towards the sun). It means night and day are nearly exactly the same length of 12 hours all over the world. The term equinox, derived from Latin, meaning "equal night".

However, it could last longer as sunrise and sunset are defined from the moment we see the upper edge of the sun appearing above the horizon and disappearing below it.

It is the first equinox of the year, the second being the September Equinox which takes place around 22 September. It is the Southern Hemisphere's Spring Equinox and the Northern Hemisphere's Autumnal Equinox in the Northern Hemisphere. Find the times of the equinox happening in locations across the world.

Tour organisers at Stonehenge are expecting the new age crowds to witness the magnificent sunset over the stones around 10.45pm (GMT) on Friday.

The Pagans consider this to be the time of the ancient Saxon goddess, Eostre, representing new beginnings and fertility. This is why she is symbolised by eggs (new life) and rabbits/hares (fertility). Her name is also where we get the female hormone, oestrogen.

druids stonehenge
Druids wait for the sun to rise as they celebrate the Spring Equinox at Stonehenge on March 20 2009 near Amesbury, Wiltshire, England.Matt Cardy/Getty Images

From Eostre also come the names "Easter" and "Esther" the Queen of the Jews, heroine of the annual celebration of Purim which was held on 15 March. At Easter, Christians rejoice over the resurrection of Jesus after his death.

It is also time to renew your immune system. In Wiltshire as in the rest of rural Britain in the past it was tradition to drink dandelion and burdock cordials to cleanse the blood, described as a good tonic after a harsh winter.

spring equinox
Matt Cardy/ Getty Images

This year the equinox coincides with the once-in-a-life opportunity to witness a near total solar eclipse. The next total solar eclipse will take place in the UK in 2090 and in 2081 in central Europe. So it's not to be missed. Check when it is happening across Britain.

For more information about the Druid Ceremony and festivities this year visit stonehengetours.com.