The natural Navigation: The Right Course, Naturally

This photo of the roof of my home tells a story of the sun’s journey.

The morning shadow from the dormer window is retreating and the sun is reaching more of the roof with each minute. The frost from the night before is thawing in the warm light. It is also forming a very simple shadow compass. At this time of year the sun rises very close to east and the direction that the frost is retreating will be west to east. The protruding ‘nose’ of frost near the top of the roof can be joined to the jutting part of the shadow to form a near perfect west-east line.

This effect can be seen in so many places at this time of year, as we get closer to the spring equinox (20 March). It will also work close to the autumnal equinox (23 September this year), but not in summer or…

Read More...

Just back from a little research in the New Forest. While I gather my thoughts about all the natural clues to wayfinding that the Forest revealed I just thought I’d let you know about a great website from a different part of our island. Stonesofwonder.com is a very informative guide to the prehistoric sites of stone monuments of Scotland, all arranged with celestial observation or inspiration in mind. There is information about the location of sites like  Ardachearanbeg, Clochkell, Cultoon, Finlaggan, Drumtroddan, Clava, Callanish and Stillaig, to name a few, and details about their relationship with moments like the equinoxes, solstices and lunar standstills. The website is well worth a visit, and much more accesible than the real things at this time of year.

An engaging group for the Beginner’s Guide to Natural Navigation course at the Royal Geographical Society yesterday. Diverse in age and interests as always. When we were discussing the difference in the sun’s behaviour between the solstices and equinox it felt more poignant that we are so close to the autumnal equinox itself. We looked at a model of the Earth orbiting the sun, then shifted our attention to shadows. A couple of days ago I took advantage of the sunshine to practice what I preach.

This chalk line in this picture shows the shadow tips joined over a period of a few hours on the morning of the 21st September. The line comes very close to a straight line, but even on the equinox it is never a perfectly straight line – unless you happen to be standing on the equator when the sun would rise due east, pass directly…

Read More...

Another cracking dawn. There were four Roe deer in our neighbouring field, but sadly they scarpered before I got to my camera. I don’t actually have a brilliant lens for wildlife, so you have been spared a photo of four brown smudges in a brown field.

Only a few days of this solar season left, the autumnal equinox is on 22 September. This means that in the UK there are only four more days when the sun will have any north in it at all for another six months. At times like this, close to the equinox, the point on the horizon that the sun rises changes by more each day than at any other time in the year.

Nice article on the Beeb website about the Saturn equinox. A succinct definiton of ‘equinox’ in the article too:

‘Equinox is the moment when the Sun crosses a planet’s equator, making day and night the same length.’

I forgot to mention that I delivered the manuscript of my book to my publishers, Virgin Books, three weeks ago. It is an exciting moment, a good line in the sand, but far from a terminal one. Work will continue on it until about November probably.

During a private course yesterday we spent some time looking at the effect of the wind on trees and grass. We also looked at the lee effect, when leaves and other natural drifting materials accumulate on the lee side of obstacles.

This is something that I am both more sensitive to and wary of since my trip to the Sahara in March. The lee effect there puzzled me for several days until a sandstorm blew in and blotted out the sky. Ironically it clarified things mentally. There is a difference between a prevailing wind and wind that has a huge short-term impact. The sand that was deposited in some areas that I crossed in Libya indicated a wind direction that clashed with the direction that both the trees and the dunes were suggesting. It became clear that this was caused by a sandstorm blowing in from a different direction to the…

Read More...

In this photo you can see the dew that the sun has not yet burnt off. The shadow itself is mostly moving right to left in this picture, leaving the thin band of wet wood in the shade all the time. This thin band is a rough east-west line at all times of the year, but quite an accurate one at times like this, close to the spring and autumnal equinoxes.

The small patch of moisture that is in the sun reveals the direction that the shadow is shortening, a crude north-south line as we near the middle of the day.

As we move on away from the equinox I thought I would post this photo of the lines made by the shadow tip from a stick (or in this case a kids swingball!).

These two lines are from the shadows approaching noon and only one day apart. Since it is the equinox, they are near exact east/west lines. The gap between the chalk lines is at its greatest at the equinox and closes to near zero at the solstices.

On a slight tangent, it was a very similar method, ie. measuring the length of the shadows that helped the ancient Greeks come up with their first estimates of the size of the earth.

It is the morning after the equinox and not a bad one either. The sun rises due east on the equinox, but the daily difference is at its greatest at this time too so we have already moved north of east.

In this picture the horizon is well above sea level because of the hill, so we have to bear in mind that the angle the sun makes to the horizon will be 90 degrees minus our latitude, ie. our colatitude.

Although I occasionally get labelled as Mr. Anti-anything-modern-and-would-rather-eat-a-pair-of-hemp-pants-than-use-a-GPS*, the truth is different. I do use a GPS, quite regularly in fact and always take one on serious walks, even if I don’t use it. I was able to use it to test natural navigation skills in the Libyan Sahara recently.

Soon I am hoping to use technology to solve a riddle that is proving elusive to both natural observation and thought. That is the shape of the a shadow stick’s arc as it goes from one side of an equinox to another. It is too subtle for me to gauge from stick and chalk efforts in my back garden. The answer is not in any of the many books and articles that I have on astronomy, ancient or modern. I have put this little riddle to dozens of good minds over recent months, some of them professional scientists, and no-one has…

Read More...