In this photo of a dog-mauled football, we are looking southeast. But why does the football’s shadow appear longer than the patch of frost? Surely, since the sun is rising it should be the other way round?

Useless clue: it doesn’t have anything to do with the dog, who wisely avoids footballs until they are well defrosted.

UPDATE: The patterns of frost we see as the day wears on are shaped by more than one factor.

The areas that have received direct sunlight will of course thaw faster than those that remain in the shade.

The colour of a surface has a huge effect too. Dark earth will thaw faster in the sun than light-coloured stone.

The wind also has a big impact on any day with a light breeze or greater. The air the breeze brings will normally be warmer than the ground that has frozen overnight thanks to the heat that has radiated up during the cold night. This warmer air will thaw places according to their exposure. The next time you are in an airliner crossing over snow-covered mountains notice that the lower limit of the snow, the snowline, is not a perfectly straight line. It undulates. It will typically be slightly higher on the southern side, where the sun can warm the ground, but even on one side the line will move up and down according to gradient, the shape of the land and the prevailing wind direction. Where a valley aligns with the prevailing wind direction, its snowline is often noticeably higher as the snow has thawed to a higher level than the surrounding ones.

In the picture above the small patch of grass that has thawed just to the right of the football’s shadow tip has lost its frost because it is marginally higher than the surrounding grass. The sun may have found it easier to reach this patch, but it is also because the warmer air of the day has already found this grass. The warmer air and sun have failed to melt the frost of the grass that is a few centimetres away because it lies a little lower.

By mid-morning the grass is often a patchwork quilt of frost and green, a mixture of areas that have received direct sunlight or warmer air and those that have not. There are clues to direction in these frost shadows, even when the sun has hidden, and a lot more besides.

Some of the routes used by the pioneers of the Pacific match the migratory routes of the birds exactly.

The route used by the Maori fleet that sailed from Tahiti to New Zealand sometime in the fourteenth century and settled there is the same as that taken by the Long-tailed Cuckoo each September.

I like to think of these earliest navigators. I imagine them gazing up as flocks of birds head uniformly over the horizon in one direction only to repeat the exercised in the opposite direction half a year later. It does not take great leaps of the imagination to deduce that the birds are not doing this great exercise for fun, QED, there must be something in the direction they that travel. All that would be needed to follow them in a boat would be curiosity, desperation or a mixture of both.

I often think back to these times when I see contrails from aircraft high up in the sky. These great tin birds are not ploughing the blue for fun either, they each have their distant destination. And, like all journey patterns, there is nothing random about these lines.

Contrails over the UK are formed in a northwest-southeast direction more often than any other alignment. I took the above photo this morning and it shows a ‘flock’ of northwest/southeast contrails. But I’m sure you knew that already, from the sun in the bottom left corner. 

I took some photos of the results of my moon shadow stick, together with a perfect north-south line, which I will be using on my Beginner’s Guide to Natural Navigation courses. Yes, that is a bit of a tease, but those who come on the courses part with £105 and I make sure that it includes plenty of exclusive material, not least dozens of images that cannot be seen anywhere else.

As compensation, I have posted these photos that I also took yesterday, of snow clinging in long thin strips to the southeast side of the tall beech trees.

Then it was time to look southeast and to watch Virgo melt back into the dawn light as Venus rose above the thin slither of a waning crescent moon. Below them pink and orange light bounced through under the dark blue sky and above the white of the hills.

My kind of music. Probably what Dreyfus was thinking too.

If the sky is clear we will get a very good view of Mars in the east in the early evening. Sitting between the constellations of Leo (easy to find) and Cancer (hard to find), it will be rising about thirty degrees north of east at dusk and pass through due east at 8.30pm. By then Orion, below the high moon, will have moved to occupy a large part of the southern sky. If you follow Orion’s belt down to nearer the horizon then low in the southeast you will see the brightest star of them all, Sirius.

If you do happen to be awake late, then Mars will have moved to be due south and high in the sky by 1am. By this time the moon will have begun its steep descent in the west. If you are enjoying this in fresh air then you will either be very cold, or the owner of some excellent outdoor kit.

This photo is taken looking southeast. The setting sunlight can be seen bouncing off the northwestern edges of the clouds.

This morning’s sun was a strong enough clue, but if we wanted to know which way was southeast then these aircraft contrails are pointing the way to the continent.

It looks like a particularly busy morning for aircraft, but this is just a reflection of atmospheric conditions. The hydrogen-rich jet fuel has mixed with oxygen, reacted in the engines and formed, among lots of other lovely and not so lovely things, water. In certain temperatures and humidity levels this water freezes into ice crystals. The high cirrus clouds that we normally see are also composed entirely of ice.

The length of time that a contrail survives depends on the humidity, if the air is dry it will sublimate away, but if saturated they will last as long as other cirrus clouds.

In my last entry I talked about dawn and dusk colours, these two dawn pictures show the shift in colour quite nicely. There was only one minute between the two shots. Interestingly it appears to have reddened, which is not what we’d usually expect to see – ah, nature, that slippery friend!

Natural navigators will have spotted already the windswept nature of the trees on the shoreline, confirming that we are indeed looking southeast.