The Autumnal Equinox
There are four dates in the year that are important for the natural navigator, and anybody whop wants to live their lives in touch with the seasons – the summer and winter solstices, and the spring and autumn equinoxes.
Due to a 23.5 degree tilt of the Earths rotational axis (imagine the earth is an apple turning on a spit – the spit is the rotational axis) and the orbit around the sun, the sun appears to be a slightly different place in the sky at noon every day. The point at which it rises over the eastern horizon in the UK and sets over the western horizon also seems to change every day, and we can use this changing pattern to help us determine direction and track the changing months.
The summer (21/22 June in the UK) and winter (21/22 December in the UK) solstices are the days when the sun will be at its highest and lowest point above the southern horizon at noon respectively. Around the time of the summer solstice (in the Northern Hemisphere) the sun will rise in roughly the north-east and set in roughly the north-west, and at Midwinter (the winter solstice) the sun will appear over the horizon south of east and set south of west. Between these dates the sun will be rising at different points over the eastern horizon, on a slow march north or south depending on which side of the year we are in.
There are only two dates when the statement: “the sun rises in the east” are true – these are the equinoxes. Equinox is from latin (meaning equal night as there is roughly the same amount of light and dark within the 24hr period), and there are two equinoxes in the calendar – the Spring or Vernal Equinox in March (20/21) and the Autumnal Equinox in September (22/23). These dates are halfway between the solstices, and on these dates the sun will rise pretty much due east – and they also mark the point where we we will either have more day than night, or night than day, in a 24hr period.
If you would like to learn more about the movement of the sun, stars and moon and other natural navigation techniques (and have a clearer, simpler explanation!) you can book on to one of our Natural Navigation courses.
Spring or Vernal Equinox: 20/21st March
Summer Solstice: 21/22 June (‘longest day’)
Autumnal Equinox: 22/23 September
Winter Solstice: 21/22 December (‘shortest day)
There are also the excellent natural navigation books by Tristan Gooley available from Amazon and other retailers: