Tag Archives: sunset

A Christmas Sunrise Surprise

What is it about a spectacular sunrise that captures our imagination so strongly? Here is an article I wrote for the February edition of the Marshwood Vale Magazine inspired by the special sunrise that I witnessed on Christmas morning.

It was still early and I was in the kitchen, making cups of tea and getting some of the food ready for our festive breakfast.  Carols sang out from the radio and I did my best to ignore the news on this very different Christmas morning.

Our kitchen window looks northwards across a narrow valley on the edge of town and there is always much to see even if it is only a storm approaching from the west.  That morning, though, I noticed something different, something special.  The part of the eastern sky that I could see was suffused with orange light suggesting that we might be in for an interesting sunrise.  This doesn’t happen very often here and I knew it wouldn’t last so I told Hazel, grabbed my camera and went into the street to get a better view.   There was an unusual stillness, a rare quiet but, by contrast, the entire eastern sky appeared to be alight with a bright, fiery display that captured the view, transforming telegraph poles and nearby trees into skeletal silhouettes.

It was as though someone had taken a large brush and splashed paint in rough horizontal layers across the thin cloud that hung in the eastern sky that morning – starting with yellow, then switching to orange, then red and finally mauve.  

By now Hazel had joined me and we stood there, neither of us dressed for the occasion but both in awe at the astonishing natural spectacle we were witnessing.  I knew the colours were changing all the time as the sun crept upwards and the cloud cover shifted so I took a few photos as a record.   Suddenly remembering where I was, I looked about and saw thick frost on the parked cars and realised I was getting cold. It was time to go in but I went with renewed optimism.  Even in a pandemic year, perhaps especially in a pandemic year, the non-human world can surprise and thrill. 

The rational part of me knows that there is a good scientific explanation for the extraordinary light show we witnessed but this does not detract from the spectacular nature of that morning’s sunrise.  So, what is it about these displays that we find so captivating?   The colours are surely part of this.  The reds and oranges filling the sky express a certain danger, a wildness that is unpredictable, uncontrollable and ephemeral.  Perhaps we also gain an insight into the power of the sun and a better appreciation of our place in the world as just one small part of the overall ecosystem? 

Impression, soleil levant, Claude Monet 1872 (Public Domain via Wikimedia Commons)

As you might expect, the beauty and mystery of the light at sunrise (and sunset) have inspired artists who have tried to capture some of the effects in their paintings.  Norham Castle, Sunrise, painted by the British artist JMW Turner in 1845 is a depiction of the morning light over this Northumberland landmark.  The painting barely illustrates the castle itself, concentrating more on the light from the rising sun and its reflections across the nearby river.  The French artist, Claude Monet was also fascinated by the effects of light at different times of day and created many artworks trying to capture these effects.  One of his best-known depictions of the morning light is Impression, soleil levant 1872, showing the sunrise over the port at Le Havre with the sun casting red light across the water and orange light across the hazy clouds.   

Science, on the other hand, provides us with a different understanding of the colours we see at sunrise.  Two basic ideas are important here.  Firstly, although the light leaving the sun appears white, it actually consists of light of different wavelengths that we see as a range of colours from red and orange through yellow and green to blue, indigo and violet.  A helpful way to imagine this is to think of a rainbow where these different colours are spread out in the sky. Secondly, the sun’s light is scattered as it passes through the layer of gases, principally nitrogen and oxygen, that constitutes the atmosphere surrounding our planet.   This scattering is wavelength-dependent so that blue wavelengths are scattered more than the red and orange.  

With those two ideas in mind, let’s consider the sun in relation to the earth at different times of day.  When the sun is high in the sky during the day, the sunlight will have a short path through the atmosphere.  Preferential scattering of some of the blue light will occur making the sky appear blue and, because some blue has been removed the sunlight acquires a yellow tinge.  At sunrise, the position of the sun is very different.  Sunrise occurs when the world turns until light from the sun just reaches the part of the planet where we are observing.  With the sun low in the sky and close to the horizon, the sunlight will have to travel a much greater distance across the atmosphere.  As a result, scattering away of blue light is almost complete, allowing the orange and red light to dominate.  An analogous argument can be applied at sunset.

Although this explains how the light becomes orange and red at sunrise (and sunset), it doesn’t account for the variability of the event.  This depends strongly on the particular weather conditions of the day.  The key to a sunrise where orange and red light fills the sky, though, is high level cloud but not too much of it.  This cloud catches the red and orange light, rather like a celestial projector screen, and the result is a memorable sunrise like the one I saw on Christmas morning.

The colours of a Dartmoor Sunset

Last week, on a clear, warmish evening, we went up to Haytor on the south eastern corner of Dartmoor to watch the sunset.  Haytor consists of two huge outcrops of granite, one larger, one smaller, set on a hill some 450 metres above sea level. The two huge outcrops of granite are a local landmark visible for miles around, and the position of the Tor affords panoramic views across the surrounding countryside.

Haytor contrails
Approaching the larger of the Haytor rocks from the east; contrails in the sky

 

A wide, grassy track led steeply up to Haytor from the car park. The sun was setting directly behind the great granite outcrop that evening so the path and the surrounding countryside were in shadow, bathed in an eerie twilight.  Stands of yellow gorse and vivid purple bell heather lined the path and a few crows pottered about on the track ahead of us.  The rock itself was a flat grey in this light but, behind it, the sky was a luminous pale blue engraved with contrails left by passing aircraft, brilliant white shooting stars.  Turning to look back, there were long but slightly hazy views across rolling countryside to Newton Abbot and on to the sea more than 10 miles away at Teignmouth.  Much of this land was still illuminated by the sun and we could see woodland, small towns and the white scars of clay mine workings.  Increasingly, however, a portion of the land lay in shadow as the sun set.

Eastern view
The view to the east from Haytor towards the sea

 

Heather and gorse
Heather and gorse

 

Under the eastern flank of the larger rock, shadow dominated and the air was cool but upon reaching the western side it was as though we had entered a different, more optimistic world – a world of orange light, brightness and warmth.  The sun was still some distance above the horizon but its low rays created a curious moonscape on the nearby moorland.  Every tussock of grass and every craggy stone were illuminated along with the occasional sheep; every object cast a long shadow.  The rich light lent a warm glow to the grey Haytor stone probing every crack, crevice and fissure.  Two German children and later, several local lads in reverse baseball caps clambered in to an alcove in the rock to enjoy the view.  One or two small birds tracked across the landscape together with a lone bee returning to its burrow. In the distance the western hills acquired an apricot halo.

Dartmoor moonscape
Dartmoor “moonscape”

 

Moonscape on Haytor
The smaller of the Haytor rocks with the “moonscape” created by the setting sun

 

As the earth turned, the sun continued to approach the horizon but for some time, corresponding changes in the landscape were slow.  Looking back to the east, increasing amounts of land were enclosed in shadow, and, around the Tor, shadows lengthened.  The colour of the rock changed slowly from a warm pale brown at 20.00 to a deep reddish brown over the next twenty minutes.

Haytor rock 2002
The larger Haytor rock at 20.02

 

Then events seemed to accelerate and I detected a change in the light level as if someone were turning down a dimmer switch.  I suppose the sun had begun to dip below the horizon but it was difficult to be sure as it was still too bright to look.  Shadows became longer still and the rock took on a pinker almost red hue, not unlike the colour of the stone used in some of south Devon’s older buildings.  For a few minutes, the sun painted the landscape surrounding the rock in the surreal colours of pink and a luminous green.

Haytor rock 2024
The larger Haytor rock at 20.24

 

Haytor rock 2027
The larger Haytor rock at 20.27

 

The colour of the rock continued to change and by 20.25, with the sun about half way below the horizon, (based on a photograph), the colour lost its warmth as if it were being drained away.  By 20.26, grey started to insinuate and a minute later the sun had disappeared.  The rock was now a uniform grey and the sun had set.

Sunset Haytor 2027
The western view at 20.27

 

All that was left on the western horizon was an orange glow above the hills, a memory of the sun, with increasing apricot fringes either side.  Overflying aircraft and their contrails were now tinged with pink and, above all this colour, the sky was a very washed out, pale blue.

Eastern view 2

 

We walked back to the car in the half light, the air cooler now.  Ahead of us and in the distance, the eastern hills were bathed in a hazy dark blue light that extended above the land for a short distance.  Above this blue layer was a distinctive red layer that shaded to orange and yellow before merging with the clear blue sky above.

A white moon, almost full but not quite, now hung in the sky like a ghostly eye.

…………………………..

I’ve seen many impressive sunsets but I don’t recall ever being able to follow the changes so clearly.   What we witnessed that evening was a spectacular natural phenomenon, a celestial light show.

But can we understand how all these colours arise?  The explanation comes from considering the position of the sun at different times of the day and the effect of the earth’s atmosphere on the sun’s light.

Although the light coming from the sun is white, we know from looking at rainbows that it is in fact composed of light of different colours (red, orange, yellow, green, blue, indigo, violet).  These colours of light have different physical properties that mean that they respond differentially when they meet particles in the atmosphere.

For much of the day, the sun is roughly overhead and as its light travels through the earth’s atmosphere it encounters molecules in the air (nitrogen and oxygen mainly) and some of the light is scattered during this encounter.  The blue light, and the violet, are scattered more than the other colours and our eyes preferentially detect this scattered blue light; this gives the sky its colour.  Because a small part of the blue light is lost through this scattering, sunlight appears slightly yellow rather than pure white.

When the sun is very low in the sky, towards the end of the day (sunset) and also near the beginning (sunrise), sunlight has to travel much further through the atmosphere.  Blue light is scattered as before but, because there is so much more atmosphere to traverse, the blue light is eventually lost, so that red and orange colours dominate at sunset and sunrise.

 

But what about the colours in the eastern sky?  The layer I described as “hazy dark blue light” was actually the earth’s shadow, where our planet casts a shadow on the atmosphere as the sun sinks below the horizon.  As the sun falls further, this shadow layer increases, only to disappear eventually in to the deepening blue of the night sky. The red layer goes by the wonderful name of the Belt of Venus and arises from residual sunlight encountering dust particles in the atmosphere.  These particles scatter the light (red by now) backwards.

 

Thanks go to Hazel who had the idea for sunset watching.