The Northern Lights

Swirling rivers of greenish-blue light against a clear sky, dancing seemingly with a will of their own, sometimes almost static, the Northern Lights (Aurora borealis) are one of nature’s most spectacular displays. For all their beauty, though, they are the product of a violent event high above us, the clash of charged particles from the Sun with the Earth’s magnetic field. 

Solar winds send energised particles from the Sun’s surface, hitting the Earth’s upper atmosphere at speeds of around 45 million mph. Acting as a defensive shield, the Earth’s magnetic field forces the charged particles to move in spirals along the magnetic field lines towards its magnetic poles. Upon hitting the gas atoms and molecules in the Earth’s atmosphere, they transfer their energy which is transformed into photons.

The colour of the Northern Lights is dependent upon three factors at the time of the collision: the amount of energy held in the solar wind’s electrons, the type of gas atoms and molecules they collide into, and the altitude at which it occurs. A red light is produced when high-energy electrons interact with oxygen at an altitude in excess of 290 kilometres in the ionosphere while the more familiar green light is the result of the impact of low-energy electrons and oxygen at lower altitudes. A collision with nitrogen can produce a blue or red hue and other colours such as pink or purple are created when there is a mix of gases.

As the solar wind particles are funnelled towards the Earth’s magnetic poles, aurorae are most likely to be seen in a circular area around them, in the northern hemisphere, principally around the northern coast of Siberia, Scandinavia, Iceland, the southern tip of Greenland, northern Canada, and Alaska. When solar activity is particularly intense, as at the end of February 2023, they are visible much further south. The southern hemisphere has its own lights, the zone passing mostly over Antarctica and the Southern Ocean and are most likely to be seen from land in Tasmania with occasional sightings in southern Argentina and the Falklands.

Aurorae are not intermittent events but happen all the time, a fact brought vividly to life by The Space Weather Prediction Centre’s fascinating interactive forecast of the location and intensity of an aurora in the world over the next thirty to 90 minutes[1]. Whether we see them or not is dependent upon sky conditions and the level of light pollution.

Named Aurora borealis by Galileo in 1619 and explained scientifically by Norwegian physicist, Kristian Birkelan in 1902/3, the Northern Lights have long fascinated mankind, featuring in cave paintings found in South-western France dating to 30,000 BC, and first recorded by an astronomer in the court of the Babylonian king, Nebuchadnezzar II on a tablet from 567 BC. Absent a rational explanation for their cause, they inspired many myths and superstitions.

For the Vikings, they were the shimmering reflections of the armour of the Valkyries sent by Odin to collect the bodies of the warriors slain in battle, while in Finland fire foxes travelled through the sky so quickly that their tails produced sparks as they brushed the mountains. In northern Sweden the lights, created by shoals of herrings, were a harbinger of a plentiful catch.

Elsewhere they represented the souls of the dead, in Greenland of children who had died in childbirth and in Norway of old maids, while for the Sámi they were to be feared and respected. Provoking them by waving or whistling in their presence ran the risk of being snatched away. In Scotland, the lights, known as “Merry” or “Pretty Dancers, were created by fallen angels and warriors who battled it out in the skies, their drops of blood creating the distinctive red specks on the green heliotrope known as bloodstone.

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[1] https://www.swpc.noaa.gov/products/aurora-30-minute-forecast

There Ain’t ‘Alf Some Clever Bastards – Part Eighty Six

Hans Lippershey (1570 – 1619)

“Twinkle, twinkle, little star/ How I wonder what you are” goes the nursery rhyme. There is something mystifying and deeply captivating about the celestial bodies that sparkle and shine above our heads at night-time and from time immemorial Homo sapiens has wanted to get to know them better. Today, of course, we can get a better view of them from terra firma by using a telescope. But who invented this very useful scientific instrument?

Popular theory gives the credit to Galileo Galilei but, inevitably, it is a lot more complicated than that. This is where the latest inductee into our illustrious Hall of Fame, Hans, or Johann, Lippershey, a German-Dutch spectacle maker comes in.

The techniques for making glass and grinding lenses came on leaps and bounds in the 16^th century, making it easier to develop smaller and more powerful lenses. Inevitably, someone would have the bright idea of seeing what would happen if they held up two lenses. Indeed, an apocryphal story suggests that Lippershey conceived his idea of a telescope when two children held up a couple of lenses and made the weather vane of the local church appear closer.

Less charitable souls claim that he stole the idea from a neighbour, fellow eyeglass maker, Zacharias Jansen. The truth is buried in the mists of time but what is certain is that Lippershey developed a rudimentary form of telescope, consisting of a concave eyepiece which was aligned to an objective lens, concave, of course. It boasted a magnification power of three, pretty feeble by modern standards but at least it was a start.

Emboldened by his success, on October 2^nd 1608 Lippershey applied to the States General of the Netherlands for a patent for what he called an instrument “for seeing things far away as if they were nearby” – a rather clumsy description but the word,  telescope, was not coined until three years later, by Giovanni Demisiani. Lippershey did not get a patent granted, perhaps the waters had been muddied by the controversy as to how he got the idea. Another complication was that a few weeks later the Dutch authorities received a patent application for a patent for a similar instrument, this time from Jacob Metius, another Dutch instrument-maker.

The emergence of a rival instrument led the authorities to draw the inevitable conclusion that the device was easy to make and, therefore, difficult to patent. At least Lippershey received a large fee from the Dutch government in return for the use of his design. Poor Metius had to make do with a small reward.

The device created a bit of a stir and was mentioned in a report issued and distributed around Europe of the visit of the embassy of the King of Siam to the court of the Dutch crown prince, Maurice, in Hague. The genie was out of the bottle and a number of eminent scientists began experimenting with the concept of using a pair of lenses to bring the image of something nearer to the viewer.

By the summer of 1609, the English scientist, Thomas Harriott, had produced a telescope with a magnification factor of six. He pointed his telescope at the moon and in August 1609 drew what he saw but never published the results.

And then Galileo got in on the act. His considerable intellect was piqued by reports of the Dutch perspective glasses which reached him in 1609. Within days he had created his own telescope, without seeing a Dutch version, which boasted a magnification power of twenty. With this he observed the moon, discovered the rings of Saturn and four of Jupiter’s moons. Galileo reproduced what he saw in astonishing ink drawings, which were published.

So Harriott drew the moon first and Lippershey can rightly claim to have been the first to develop a telescope. But Galileo scooped the glory.

Such is the fickle finger of fate and why Hans is a worthy inductee into our Hall of Fame.

If you enjoyed, why not try Fifty Clever Bastards by Martin Fone

http://www.martinfone.com/other-works/

 

Eureka

 

It is a truth universally acknowledged that Galileo was a bit of a clever geezer and what troubled him should rightly concern us. Of course, he compounded his problems by developing the telescope so he opened his senses up to things that had never troubled Homo sapiens before. One thing that kept him awake at night, apart from wondering when the Inquisition would next pop up, was why the planet Venus appeared bigger than Jupiter to the naked eye but when viewed through a telescope the reverse was true. I assume he was holding the telescope the right way round at the time. Seemingly, this is a problem that has baffled scientists for more than 400 years.

But no more. When viewed directly with the naked eye Venus appears to have a radiant crown which makes it look eight to ten times bigger than Jupiter, even though Jupiter is four times larger when seen from planet Earth. Galileo thought that this radiant crown was something to do with what he called an impediment of our eyes which was eliminated when we use a telescope. He thought the phenomenon was due to optical interference to the light of the planets as it entered our eyes.

Researchers, led by Jens Kremkov at the State University of New York College of Optometry – the results were published in the Proceedings of the National Academy of Science – have shed new light on to the problem. The effect, it seems, is down to the way the light-sensitive cells at the back of the eye respond to images of different intensity set against a dark background. The light coming from Venus is brighter than that from Jupiter and the retina and brain are finely tuned to respond to the contrast between light objects against a dark background. The brighter light of the smaller plant makes it seem larger than the duller larger planet.

To test their theory the scientists used electrodes to record the electrical signals from neurons in the visual areas of anaesthetised cats, monkeys and human brains whilst the animals and humans were shown dark shapes on a light background, light shapes on a dark background and light and dark shapes on a grey background. They found that white spots on a black background looked bigger than same-sized black spots on a white background. The source of Galileo’s problem is the way neurons are laid out and inter-connected in the retina and brain and, the researchers surmise, it has ever been thus since the development of sight in the photoreceptors of the eye.

The explanation to Galileo’s problem also helps explain why we are more comfortable reading black print on white than white text on black – a fact that users of more adventurous blog templates would do well to remember.

Isn’t science wonderful!