Tomorrow, 20th March 2010, will be, astronomically speaking, this year’s Spring Equinox, and we will all welcome the first day of spring.
The word “equinox” comes from the Latin and means “equal night”, so this means that tomorrow the length of day and night will be (approximately) the same. This is possible because the sunlight will shine vertically above the Earth equator.
There are two equinoxes in a year: one in spring (20th/21st March) and the other in autumn (22nd/23rd September).
There are some curious facts about the spring equinox.
On this day in fact strange and mysterious things happen in some places of the world.
One of these mysteries belongs to Loughcrew, Ireland, not far from Dublin. In this place there are many megalithic tombs of about 3500 and 3300 BC. One of them, called Cairn T, is “equinox-oriented”. What does this mean? It means that on the Spring and Autumn Equinoxes the light of the sun enters the tomb and reaches a particular stone at the back of the tomb. This stone is carved with many symbols, in particular symbols of the sun. On the equinox days the light of the sun forms a rectangle on this stone. As the sun moves up in the sky, this rectangle slowly becomes smaller and smaller and moves to the right, until it becomes a dot and eventually disappears. You can watch this on the following video from youtube.
Another mystery concerns the Maya pyramid of Chichen Itzà: during the spring equinox (and only on that day!) the light of the sun creates a spectacular effect of light and shadows on the stairs of the pyramid: you have the impression that an enormous snake is moving and coming down the stairs. Can you see it in the picture?
Have a nice spring equinox 😉