An Observer’s Guide to Rainbows + On the Trail of the Fijian Kauri + The Black Marble – Earth at Night + A Torch in the Dark – Light Painting Definition
We love landmarks, so we are very glad to make a round twenty issues as we jump past the winter solstice and into the true grasp of winter. Twenty, perhaps, is not so exciting as ten, or one hundred, but we’ll celebrate nonetheless with your fine and magical articles to explore the world around us.
It’s as colourful as it gets in this issue. We are happy to present you with An Observer’s Guide to Rainbows. It’s been on the site for a while but deserved a cleanup and a feature position. If you read this one carefully, we promise you’ll be able to predict, classify, and appreciate rainbows like never before.
We’ll travel to Fiji with Astrid Tiefholz on a quest for some of the largest forest trees of the South Pacific, the giant Dakua tree. We’ll orbit the planet with NASA and learn about a high resolution night-sky globe that shows us our beautiful planet as a delicate black marble.
Then, we’ll venture into the dark with Jasper Da Seymour, a specialist in light painting. He’s using a torch as a paintbrush, and a camera as a canvas. He’s managed to bring spectacular shapes and designs into existence…shapes never before seen… until now.
As always, we rely on you and your enthusiasm to help us spread the word about these wonderful stories. Tell a friend, if you’d be so kind!
All the best!
– The Editor Southern Hemisphere Winter Solstice 2014
(They do just miss Tasmania in this….but it’s still worth a watch!)
In daylight our big blue marble is all land, oceans and clouds. But the night – is electric.
This view of Earth at night is a cloud-free view from space as acquired by the Suomi National Polar-orbiting Partnership Satellite (Suomi NPP). A joint program by NASA and NOAA, Suomi NPP captured this nighttime image by the satellite’s Visible Infrared Imaging Radiometer Suite (VIIRS). The day-night band on VIIRS detects light in a range of wavelengths from green to near infrared and uses filtering techniques to observe signals such as city lights, gas flares, and wildfires. This new image is a composite of data acquired over nine days in April and thirteen days in October 2012. It took 312 satellite orbits and 2.5 terabytes of data to get a clear shot of every parcel of land surface.
This video uses the Earth at night view created by NASA’s Earth Observatory with data processed by NOAA’s National Geophysical Data Center and combined with a version of the Earth Observatory’s Blue Marble: Next Generation.
We came to Fiji in search of a strange and wonderful tree, but we didn’t know its name. We knew it was a species found only in the South Pacific, and we knew it could live for more than a thousand years. And we knew its name in the obscure language of botanical Latin: Agathis macrophylla.
Our pursuit was filled with good fortune, a journey of serendipity and discovery. We found the magnificent tree, and came to know it by its melodious Fijian name, Dakua. So, how did the Dakua come to Fiji? Where can you find this most amazing of Fijian trees? Retrace our search, from the depths of geological time to the most accessible forests of the Big Island of Viti Levu. You can visit these living trees in the forests of Fiji, and, as you follow your own trail, learn a few pieces of the natural and cultural history of the Fiji Islands.
As visitors to Viti Levu, we were fortunate to find ourselves, literally, on the trail of the Dakua tree. At our lodgings in the centre of Suva, we asked our hostess: “Do you know of the Agathis tree?”
She confessed she did not, but her elderly father, a retired cabinet maker, spoke up from the corner of the room.
“It is Dakua!”
He told us of the massive trees that used to cover the islands, held in awe and reverence by Fijians.
“Go to Colo-i-Suva,” he told us. “There, you will find these trees.”
Dakua, a close relative of New Zealand’s kauri tree, is one of a group of plants with a curious Southern Hemisphere distribution. A quarter of a billion years ago, its botanical family, the Araucariaceae, covered the entire planet. In those long distant times, when dinosaurs walked the Earth, they were a key element of extensive forests that are remembered through their petrified fossils.
Today, these trees are found in the South Pacific, Australia, New Zealand, and, curiously, Chile and Brazil. These monkey-puzzle, hoop pine, and kauri trees are evidence for the ancient existence of Gondwana, the ancient Southern supercontinent- they have survived only on these once-connected land masses. Once, long ago, Dakua’s ancestors grew thrived in Tasmania.
In geological terms, Fiji is a young landscape of rocky volcanic islands. Only eight million years ago, far far younger than the ancestry of the Dakua tree, the islands were born of fiery rock from the ocean depths. Since then, coral has accumulated around these solid anchors of land, forming much younger islands of reef. The Dakua trees must have made their way over the water from the continents to Fiji within this geologically recent timeframe.
Over the past eight million years, other plants and animals have immigrated from the larger bodies of land, especially New Guinea, to these volcanic islands. These make up the native, pre-human biodiversity of Fiji, a dynamic array of changing species. New arrivals came to Fiji: some adapted and thrived, while others perished.
The biggest event in Fiji’s biological history was the arrival of human explorers on epic oceanic voyages, some 3,000 years ago. Archaeological excavations show the early presence of a people known as the Lapita, but little remains of their legacy but bones and pottery. Modern Fijians trace their ancestry to the courageous expedition led by Chief Lutunasobasoba. The new settlers modified the natural landscape, seeking living space, building materials, and food to eat. They brought plants and animals to the islands, including yams, taro, cassava, bananas, poultry, pigs, dogs, and that most intrepid of animal travellers, the rat. Some native wildlife, including giant iguanas and pigeons, became extinct around this time. The Dakua tree doubtlessly had arrived to Fiji far earlier than the human settlers, and must have already been a component of the forests when the first explorers entered into the jungle.
The Dakua was soon recognised as a fine source of timber. Master craftsmen of wooden boats and buildings, the Fijians distinguished two types of Dakua tree: the taller, straighter Dakua balavu, and the shorter, branchier Dakua leku. Like the Polynesian Maori of New Zealand, they saw both the divine and practical aspects of these massive trees. It was valued as a sacred totem, a structural timber, and a prized canoe hull.
Awed by such immense history, we followed our host’s instructions into the steep green hills of Colo-i-Suva. This forest is the first of Fiji’s National Parks, in the hills just above the capital city, and here, you will find these trees. Although armed with the tree’s Fijian name, we were still unsure of ourselves. With so many species in the tropical rainforest, how would we recognise the tree when we encountered it?
At Colo-i-Suva, we walked downhill from the lakeside tourist lodge. We were looking for the Forestry Department, hoping to find more information. On the roadside, a young man in a traditional sulu waved to us, and with shining smiles, we exchanged greetings- “Bula!”
We took a moment to ask him if he knew the location of the Forestry Office. By sheer luck, we discovered that this kind man, Maleli, worked for the Forestry Department. He told us the Forestry offices were just these buildings here; yes, he knew about Dakua; indeed, it was his family totem; and – look over there – that tree just there, towering on the edge of the forest, was Dakua.
It was instantly recognisable. Its thick branches were solid against its stout trunk, and it grew in the ramrod-straight way of other cone-bearing trees. Maleli walked with us to the tree, and, standing beneath its fern covered branches, we gleefully captured the tree in photographs, gazing at it from all angles.
This Dakua was large and impressive, but it was obviously planted by humans. Where could we find an ancient forest giant? we asked. Were there any in the forest here? Again, Maleli had the perfect answer for us.
“Yes, you can follow the forest path named ‘Big Dakua Trail’, and it will lead you to Big Dakua, one of the last remaining elder trees.”
He pointed toward the beginning of the trail, and, before we parted, invited us to return to the Forestry Office.
We headed down the steep pathway into the thick, emerald rainforest, and found the wooden sign towards the Big Dakua tree. The conveniently named trail was easy to follow. A narrow ridge, tumbled with volcanic rocks, picked its way up from the liquid pools and splashing waterfalls of the ravine. We climbed higher and higher, and, dozens of metres before we reached it, spotted the mottled grey trunk and emerging top of the Big Dakua. Here was a venerable forest elder, a tree with a memory measured in centuries. It stood above, and separate from, the tangled forest beneath its branches; it was an ambassador from the ancient times and forgotten continents, before the Fijian islands had been born from the underwater volcanoes.
Humbled and inspired, we returned to the office. Maleli introduced us to scientists and caretakers who shared their passion for the forest with us over hot tea and warm bread rolls. We were especially happy to learn that we had science-friends in common: the Colo-i-Suva Park has worked with many international collaborators over the years. On the wall, a calendar showed the seasons of fruiting plants. It was June, the Fijian month of Vulaiwerewere, the month of Dakua.
Our search ended in success. Not only had we learned about the Dakua tree, but we had seen it in the wild, and befriended the people devoted to protecting the forest. But Maleli had one more surprise in store for us. He took us back across the road, and towards a large greenhouse. Inside, thousands and thousands of Dakua seedlings were flourishing in cups of black, fertile soil as part of Fiji’s Million Trees Project. He told us about what it meant to him to be replanting these once-numerous trees into forests altered by human activities. He told us of his family’s totemic link to the Dakua tree, and how he shared our enthusiasm for these magical trees. And with that, he handed us a shovel, and two seedlings, and we went outside into the sunshine.
Those dazzling colours that bring everyone joy, the palette of colours splashed across the sky, the awesome power of the Celestial Dragon, the deadly bow of Indra the Hindu rain god, and the reminder from Allah that the Great Flood would never happen again: these are rainbows. These are the most splendid and gentle of aerial splendours. Rainbows have all of the energy and magic of lightning, but none of the terror. They symbolize the relief of a storm’s aftermath, and the anticipation of the warm sun.
But where do you find them? Not metaphorically, but literally? And what is on the other side of the rainbow? Would you like to know where to look, when to look, and what type of rainbows there are? Do you love those dazzling colours? If you are a seeker dreaming of a rainbow, some days you’ll find it by just stumbling upon them. When you are really connected with rainbows, like the lovers, dreamers, and meteorologists, then you’ll know when rainbows are most likely to be spotted, what causes them, and, most importantly, exactly where to look. It’s easy. The magic number is 42.
What is a rainbow?
When conditions are right, sunlight hits water droplets in the air and forms an optical illusion, relative to the eye of the observer. The white colours of sunlight are scattered and divided into the portions of the spectrum- red, orange, yellow, green, blue, indigo, violet- in a continuous flow. It is the interpretation of our eyes that makes the colours look different. Some other animals, and human-made sensors, can also perceive infrared colours (beyond red) and ultraviolet colours (beyond violet). On different planets, in different atmospheres with different mists, rainbows may appear in different colours. But the familiar spectrum of a rainbow is consistent throughout our Planet Earth.
When both sunshine and rainclouds are present, the sky may be right for a rainbow. When dark clouds are visible from the side, to the opposite direction of a low sun, when you are underneath bright clear skies, are best for spotting rainbows. With a bit of conscious observation, you will be able to identify good conditions and know to be on the lookout.
Where can you find rainbows?
The familiar rainbow arc is only the visible section of a complete circle found opposite the sun, at a 42 degree angle from the anti-solar point. Imagine a line from the sun to your eyes continuing through you to a point below the horizon, and that point is the anti-solar point. The circular rainbow encircles the anti-solar point at a distance of 42 angular degrees from the line between your eye and the anti-solar point. Red is on the outside, and violet is on the inside of the arc. At ground level, you will only see the upper portion of the circle. Below the horizon line, there is usually not enough distance for there to be enough water droplets to catch the light.
A fainter, secondary rainbow is found at 50 degrees from the anti-solar point. In this second, larger rainbow, the colours are reversed- red is inside and violet is outside. The dimmer area of eight degrees in between the two arcs is known as Alexander’s Dark Band, named after the Greek philosopher who wrote about it 1800 years ago. Tertiary and quaternary rainbows are exceptionally rare, and appear on the opposite side of sky to the familiar rainbow arc.
So if you are seeking the mythical leprechaun’s pot of gold at the end of the rainbow, where can you expect it to be? Let’s presume that you are standing on the ground. In the Southern Hemisphere, the sun moves to the north at noon, and in the Northern Hemisphere, to the south. You will therefore find a Southern hemisphere rainbows in the southern half of the sky, and Northern Hemisphere rainbows in the northern half of the sky. You will never find an Indonesian rainbow if you are looking north, and you will never find a rainbow in Russia looking south.
In the mornings, rainbows are to the west, and in the evening, rainbows are to the east. The lower the sun is in the sky, the more of the arc will be visible above the horizon, as the anti-solar point is less angular distance below the horizon. Midday rainbows will be shallower, and when you are on the equator, non-existent. People in temperate or extreme latitudes will find more opportunities to spot spectacular rainbows than those in the tropics, because the sun spends more time at low elevations. When the sun is low in the sky, and shines in a red or orange tint at dawn or sunset, the colours of the rainbow will also be tinted.
Varieties of Rainbows
There are several kinds of rainbows. The standard rainbow is a segment of a colourful halo centred on the anti-solar point, found at 42 degrees. But different conditions of water, ice, and lighting can create different rainbows.
The brightness of the moon can produce rainbows, as well. Lunar rainbows, or moonbows, are dimmer than sunbows, because the light is so much less intense. They are similar to rainbows- found at 42 degrees, but around the antilunar point.
Stacked rainbows, or supernumary rainbows, can be especially brilliant. When conditions are excellent for bright rainbows, a complex interference pattern can result in rainbows having extra bands of colour.
If you are above the ground looking downwards, you may be fortunate to see the fully circular rainbow known as a glory. To the wonder of mountain climbers and airplane travellers, this is recognizable immediately as a small rainbow around the anti-solar point, with the shadow of the observer in the centre. This is known as the Light of Buddha, recognised by the Chinese as a signal of wisdom.
For air travellers viewing a glory, the shadow of the airplane may be distinctly recognizable in silhouette at the centre of the halo. For a mountaineer, a large dark form may be seen extending from their feet into the very centre of the glory. It is the shadow of the observer themselves combined with the mountain upon which they are standing. This eerie figure is the Spectre of Brocken, after the highpoint of the German Hartz Mountains.
The sun halo is formed by the hexagonal ice crystals in high icy cirrus clouds and is observed as a ring at 22 degrees angular distance around the sun. While not as colourful as a true rainbow arc, it can display colours trending from a red inside to a violet outside. This can also be seen around the moon, as a moon halo (not to be confused with a lunar rainbow)
A related phenomenon occurs when the crystals of a sun halo are guided by the wind into a vertical orientation: the whimsically named arcs known as sundogs, or parhelia. These are segments of sun haloes that appear as arcs to the left and right of the sun.
A circumhorizon arc is part of a giant solar halo 46 degrees in angular size. They do not actually circle the horizon, but the lower parts may appear almost parallel to the horizon. Usually, there is not enough cloud cover to see the entire halo, and only some segment are visible.
In cold weather, with clouds of ice crystals floating in the air, snowbows can be seen around the anti-solar point. It is actually a normal rainbow, but it is exciting and special to see in the frigid air.
Cloud shimmers, or iridescences, are rare and beautiful colourations seen on the underside of a cloud. Usually spotted on high, thin, cumulus clouds, these spectra form in surreal shapes, rather than predictable arcs.
Fogbows, seadogs, or white rainbows, are rainbows with muted colours seen in thick, low water vapours. They appear around the anti-solar point. Cloudbows are fogbows within clouds- if you travel by airplane, keep your eyes open and you may see one.
All of these optical phenomena are wondrous combinations of cloud, vapour, and sun. But perhaps the most magical of all are the wavebows. If you are on a coastline facing westwards to the ocean, you may be fortunate to see rainbows dancing on the waves at the earliest moments of the sunrise. If you are on the east coast, look carefully at the waves in the last moments of the day, and perhaps you will see the colour spectrum. These rare wavebows are actually found at slightly smaller angles that those in the sky. The saltwater splits light at a different angle than the freshwater found in clouds and mist. Pay close attention to the waves, these are rare and magical rainbows!
How to conjure a rainbow
We’ve looked at the conditions to form rainbows, the directions you must look to see them, and the types of rainbows that you may find. But what about conjuring them, and capturing them?
You can conjure rainbows with the help of a garden hose or spray bottle in the midday sun. Direct the water away from the sun. You can use the reflection of a CD, or a cut glass prism, to create compact disk rainbows and prism spectra. One of the simplest ways to rainbow is to fill a glass of water and place it in a dark, shady place where the sun reaches it from one direction only. The edge of the water divides the white light creates a colourful glass of water spectrum.
To capture a rainbow, one needs only a camera and the knowledge of where to look. The well-equipped rainbow seeker will find themselves, with a camera ready, on high ground or a mountain peak, with the morning or evening sun to their back, and dark clouds ahead. When a rainbow is spotted, the photographer can try to move to a location that will make the rainbow appear to land at a point of interest.
To conjure a truly wild rainbow, visit a misty waterfall on a sunny day. For a tamer rainbow, try a large fountain shooting water upwards. Depending on where you are relative to the cascade- above, below, or to the side, you may find different shapes and intensities of spectra. You have conjured a rainbow!
Experimentations with your camera settings, to make the picture darker and the colours more vivid, can yield more impressive photographic images. If there is a subject of interest in the foreground, such as another human being, using the flash on the camera can fill in the details of the closer environment, which would otherwise be silhouetted. Two colourful, yet unwanted phenomena, which can be used for dramatic effect, are the scratched lens shimmer and the dirty lens flare, which show up unpredictably in damaged or dirty camera equipment. If you wear eyeglasses, you may be all too familiar with these special rainbows.
The other side
So what is on the other side of the rainbow? This question has been famously asked by philosophers and dreamers, astronomers and cloudspotters. The answer is: the sun! It is our planet’s life-giving star that is on the other side of the rainbow.
As you predict, identify, conjure, and capture these optical arcs, you will find life all the more colourful when you appreciate them. Rainbows are natural phenomena that you can actively seek out, rather than simply stumbled upon it. On some days, we’ll just simply find them, but on other days, we will know exactly where to look.