The Billy Lids

The multicoloured aurora borealis and aurora australis - the Northern Lights and Southern Lights - represent some of Earth’s most dazzling natural displays.

Scientists using data from five NASA satellites have learned what causes frequent auroral flare-ups that make this green, red and purple lightshow that shimmers above Earth’s northernmost and southernmost regions even more spectacular.

Writing in the journal Science, the scientists said that explosions of magnetic energy occurring a third of the way between Earth and the moon drive the sudden brightening of the Northern Lights and Southern Lights. There had been debate among scientists dating back decades about what triggers these auroral flare-ups.

The findings from the THEMIS satellites and a network of 20 ground observatories in Canada and Alaska confirmed that it is due to a process called “magnetic reconnection.” THEMIS stands for Time History of Events and Macroscale Interactions during Substorms mission.

Auroral displays are associated with the solar wind - electrically charged particles continuously spewing outward from the sun. Earth’s magnetic field lines reach far out into space as they store energy from the solar wind.

The researchers said that as two magnetic field lines come close together due to the storage of energy from the sun, a critical limit is reached and the lines reconnect, causing magnetic energy to be turned into kinetic energy and heat. The release of this energy sparks the auroral flare-ups.

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Icebergs in the Antarctic area sometimes have stripes, formed by layers of snow that react to different conditions.

Blue stripes are often created when a crevice in the ice sheet fills up with meltwater and freezes so quickly that no bubbles form.

When an iceberg falls into the sea, a layer of salty seawater can freeze to the underside. If this is rich in algae, it can form a green stripe.

Other coloured stripes, such as black, brown and yellow, are created by sediment collected by the ice as it moves down a hillside towards the sea. The icebergs can take hundreds or even thousands of years to form.

The iceberg photographs were taken by Norwegian sailor Oyvind Tangen from aboard a research vessel and were snapped in an area several hundred miles north of the Antarctic.

The “ice wave” formation is created by glaciation, melting and refreezing, and other natural forces, over very long periods of time.

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According to an article on the National Geographic News website, this particular fire rainbow was caught on film on June 3 2006 in northern Idaho not far from the Washington State border. A fire rainbow is more technically called a "circumhorizontal arc" or "circumhorizon arc" by weather scientists.

A circumhorizontal arc only appears when a specific set of atmospheric conditions occur. The display is caused when light entering hexagonal ice crystals in the clouds is refracted. But, for a fire rainbow to appear, the sun must be very high in the sky, the clouds must be high altitude cirrus clouds and the ice crystals must be shaped like thick plates and aligned with their faces parallel to the ground. Thus, fire rainbows are indeed quite rare, although it is probably an exaggeration to describe them as "the rarest of all naturally occurring atmospheric phenomena".

A Scienceline article discussing another fire rainbow photograph taken on the same day as the one shown above notes that even diligent weather watches in the United States might only see one or two circumhorizontal arcs in a given year.

A list of relative frequency for rare atmospheric halos published on the Atmospheric Optics website shows that circumhorizon arcs (circumhorizontal arcs) occur very infrequently. However, others such as the Kern Arc and the Lowitz Arc may be even more infrequent.

Another spectacular shot of a circumhorizontal arc taken in Canada in 2003 is available on the Atmospheric Optics website.

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Birds are the only animals today that grow feathers. Most birds have different kinds of feathers. The most visible are the overlapping contour feathers, which give birds their smooth, aerodynamic shape. Contour feathers include the wing and tail feathers, which are vital to flight. A hummingbird may have fewer than 1,000 such feathers, and a swan more than 25,000.

Feathers are a marvel of design. The central shaft, called the rachis, is flexible and remarkably strong. Extending out from it are rows of interlocking barbs that form the smooth vane of the feather. The barbs attach to one another by means of several hundred tiny barbules, which hook onto neighbouring barbules, forming a kind of zipper. When barbules unzip, the bird simple zips them back together by preening itself.

Wing flight feathers in particular are asymmetrical - the vane is narrower on the leading edge than on the trailing edge. This classic airfoil design enables each flight feather to act like a tiny wing in itself. Also, if you look closely at a major flight feather, you will see a groove running along the underside of the rachis. This simple design element strengthens the shaft, allowing it to bend and twist without buckling.

Besides their other functions, feathers protect birds from heat, cold, and ultraviolet light. Sea ducks, for example seem to thrive despite bitterly cold ocean winds. Under their nearly impenetrable coat of contour feathers lies a dense layer of soft, fluffy feathers called down, which may be up to 1.7 cm thick and cover most of the duck's body. Natural down is so efficient an insulator that no synthetic material yet devised equals it.

Feathers eventually wear out, so birds replace them by moulting - shedding old feathers and growing new ones. Most birds moult their wing and tail feathers in a predictable, balanced order so that they always retain their ability to fly.

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When springtime comes around, bees get busy and pollen fills the air. For people who suffer from allergies, pollen seems to be a curse rather than a blessing. But before we dismiss pollen as just a nuisance of nature, we should keep in mind the role this unique dust plays. We may be surprised to learn how much our lives depend on it.

Plants produce pollen in order to reproduce. Many plants depend on the air to transport their pollen after it is released from catkins or cones when they are jostled by the wind. Water also serves to transport the pollen of some water plants. Since wind is a hit-and-miss affair, trees and plants that depend on this method of pollination produce astronomical quantities of pollen. Pollen from flowering plants and grasses is dispatched to other like plants by bats, birds and insects.

Flowers have to attract potential pollinators as well as feed them. The pleasing smell and appearance attracts some pollinators, while a smell of putrefaction attracts flies. Some plants resort to trickery to ensure successful pollination. Bee orchids look like bees, and that fools amorous bees into visiting. Certain flowers capture insects and release them only when the insects have performed their pollination duty.

Thanks to pollination, plants thrive and produce the food on which we depend. True, pollen may cause discomfort to some of us, but we should all be thankful for the busy pollinators that distribute this dust of life. Successful harvests depend to a large extent on this marvelous natural process.

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