When it comes to ice, the optical repertoire of the heavens seems inexhaustible. Ice crystals, shaped variously into stellar snowflakes, hexagonal plates or pencil-shaped columns, can reflect and refract the light, to create a canvas of haloes, arcs, parhelia, paranthelia and anthelia, as well as subsuns and Bottlinger’s Rings. What they are is explained carefully, along with how they got there. It just made me want to rush out and look at the things.

Two Californian astronomers wrote the book, which is obvious from the laid-back yet awestruck style. We are told that David Knight Lynch, for example, has taught courses such as “The Physics of Music”, “High Speed Sailing” and “Extraterrestrial Life and Intelligence”. With a background like that, you’d expect the guy to get excited about the world around him.

This isn’t an easy book for the general reader, though. Heavy on geometry and full of diagrams, it feels rather dry at times. A picture caption about colour-mixing at the confluence of the Amazon and Negro rivers, for example, says, “Although the Negro’s water appears black, a swim in its piranha-infested waters shows that it is actually blood red.” That sounded an exciting piece of empirical research, and here I would have welcomed a little more anecdote.

The dust cover promises us a “portfolio of beautiful and often rare” photographs. Perhaps we are spoilt by the quality of natural history photography, but many of the pictures included here reminded me of school physics books from the 1970s. And a penultimate section deals with the night sky – eclipses, satellites, and so on – in less detail than you’d find in a lay book on astronomy.

A final chapter on the science of observing the effects offers more intriguing tips – for example, to place your eye so close to a dew drop that you cannot focus, to appreciate the reflected colours, instead of “seeing” a bright white pinprick.

So now I know what a blue moon is, though I’ve no idea when the next one is due. And I know all about bishop’s rings, what they mean about pouring oil on troubled water, and even where the Spectre of the Brocken comes from.

Living in the extreme north, spending months of the year in near-darkness,
must do extraordinary things to your imagination. Take, for example, the
various explanations invoked over the centuries for the wispy curtains of
light that stretch across the polar sky in winter – the aurora borealis
– listed in The Northern Lights.

The Danes thought they were caused by lost swans flapping their wings
to free themselves from the northern ice. The Sami, or Lapps, thought they
were unmarried women running around dragging their underwear behind them.
To the Norwegian poet Rolf Jacobsen, the curtains of lights were suggestive
of the clothes of the angels, hanging out to dry.

And, in an exceptionally surreal piece of folklore, the Inuit from the
far east of Greenland thought that the shimmering patterns were caused by
spirits playing football with the afterbirth of stillborn babies. Their
counterparts on Baffin Island, however, thought they were the spirits of
those who had committed suicide playing football with a live walrus head.

This kind of theorising obviously begs more questions than it answers
and it is with some relief that the authors turn to the scientists for
explanation. Plenty of people from Aristotle onwards have puzzled over the
effect, but it wasn’t until the English astronomer Sir Edmund Halley suggested
a link with the Earth’s magnetic field in 1716 that modern research into
the phenomenon began.

The current theory is that the lights are caused by supersonic streams
of ionised particles from the Sun, the solar wind. As it moves through the
Earth’s magnetic field, it generates electricity just like a dynamo. The
current travels along the magnetic field lines towards the poles, where
it ionises atoms and molecules in the upper atmosphere, causing them to
fluoresce.

Writing for the nonscientist, the authors pack into their book all you
could ever want to know about the aurora, including an exhaustive account
of research into the phenomenon up to the present day, with all the basic
physics you need to understand it. They leave the reader in no doubt as
to the crucial rule played by Norwegians in understanding the phenomenon
– so much so that the book sometimes reads like a plea for greater recognition,
and funding, for Norwegian research.

Perhaps this is because it was one of a series of books produced as
part of Norway’s cultural programme to coincide with February’s Olympic
Games in Lillehammer. Maybe the book suffered in the rush to get it out
on time: ‘translated into Engslish (sic) by James Sinclair Anderson’ says
the flyleaf, and there are plenty more typographical errors inside. And
without the benefit of an index you have to concentrate hard as you read
– going go back to check something in this densely packed book takes a lot
of diligent research.

* Grondahl Dreyer, PO Box 1153, Centre 0107 Oslo, Norway

James Bedding is a freelance journalist and travel writer.

A couple of guides are on hand during the summer to show people around. They
are often the only staff there: the ghostly power station is controlled via
a microwave link by engineers 27 kilometres away at another power station at
Wairakei.

The energy is carried to the surface by water, brought up through wells more
than one kilometre deep from a layer of hot rock below. Just below the
Earth’s surface, the water is at such high pressure – around 20 atmospheres
– that it does not boil. With a drop in pressure at the surface, the water
boils, and the resulting steam travels through pipes at more than 200
kilometres an hour to turbines that drive generators to produce 108
megawatts of electrical power.

You can just make out rubber fixings throughout the power station, like
shock-absorbing fastenings in a car. Because the power station is built
along a fault line, it has to be able to withstand earth tremors. Engineers
have built the whole station on a 9-metre concrete block balanced on a steel
ring; in the event of an earthquake, the whole building simply rotates. They
claim it can withstand a quake of 10 on the Richter scale.

Ohaaki’s grandparent is the Wairakei power station, which launched New
Zealand’s geothermal power generation in 1963. An information centre at
Wairakei explains in detail how both power stations work. While Ohaaki uses
about one third of the electricity it generates to pump the condensed steam
back into the ground, Wairakei has simply siphoned off 45 million tonnes of
water a year, discharging into a local river. The result has been that the
surrounding ground has subsided, and the pressure of the hot water at the
head of the wells more than halved.

Other geothermal sites in the area have also become tourist attractions. At
Whakarewarewa, pools of hot mud bubble alongside spouting geysers. And in
the back gardens are superb examples of low-tech geothermal energy
exploitation. Almost every household has an oven, dug into the ground, where
food is steamed for free.

James Bedding is a freelance writer

Visitors can be guided round Ohaaki Power station from 28 December to 28
March, from 10 am to 3.30 pm. The Information Centre at Wairakei is open
all year 9 am to 4 pm.

The polar regions provide a window into space where high-energy solar
particles arriving in the Earth’s atmosphere can cause spectacular effects,
such as the northern lights or aurora borealis.

The high-power radar will illuminate particles in the upper atmosphere
with short, high-energy pulses of radio waves. The reflected signals will
be gathered by sensitive receivers to provide information on the velocity,
ion composition, density and temperature of the particles.

The radar is being built by the EISCAT Association (the name stands
for European Incoherent Scatter), a collaboration between Finland, Norway,
Sweden, France, Germany and Britain. ‘The results will fill a major gap
in our understanding of solar-terrestrial physics,’ says Tudor Jones, professor
of physics at the University of Leicester and a member of the EISCAT council.
‘The project will also be the flagship for British ground-based geophysics
for at least the next decade.’

Building work will begin in the spring and the radar should be ready
by 1995, when the European Space Agency’s CLUSTER satellite system is due
to be launched. Both satellite and radar will investigate the phenomena
that cause the aurora borealis, but from different ends of the magnetic
field lines that lead from space to the Earth’s poles.

The aurora borealis has its origins in processes that occur on the surface
of the Sun. The Sun continuously emits a supersonic stream of particles,
at such high temperatures that the atoms are broken up into a plasma of
ions and electrons. As the plasma stream, known as the solar wind, moves
through the Earth’s magnetic field, electricity is generated. The current
travels along magnetic field lines which converge in a circle around the
poles. The associated charged particles ionise atoms in the atmosphere,
causing them to fluoresce.

While the existing EISCAT transmitter in Norway allows scientists to
study these effects at lower latitudes, the solar wind comes closest to
the Earth much nearer to the pole. Spitsbergen is the mildest and most accessible
point on a ring of places around the pole where the effect of the solar
wind can be observed at close hand.

The research will help researchers to understand the nature of magnetic
storms, of which the northern lights are a manifestation. These storms can
be highly damaging. On 13 March 1989, when the northern lights were seen
as far south as Florida, magnetic storms caused a blackout in the power
supply in northern Canada.

So says the film Arctic Light, showing at the world’s northernmost planetarium
at Tromso, the world’s northernmost university city. Here, way inside the
Arctic Circle, the Land of the Midnight Sun has a darker side. For two months
of the year, the Sun never appears above the horizon. After a day of dusk,
the aurora borealis appears.

The planetarium’s show runs during the winter, and explains where the
northern lights come from, what they are and how they are being studied.
Our understanding is evolving all the time, and the University of Tromso
is one of the leaders of the research.

The solar wind, the stream of matter that the Sun scatters in the way
that a Catherine wheel shoots out sparks, causes the northern lights. This
matter is so hot that atoms and molecules break up into their constituent
electrons and ions to form a plasma. When an electrical conductor, such
as a plasma, moves through a magnetic field – in this case, that of the
Earth – electricity is generated as in a dynamo. The potential difference
set up discharges along magnetic field lines to the poles, where the high
currents strip electrons off oxygen atoms and other atoms and molecules
more than 100 kilometres above the Earth’s surface, making them glow in
the same way that a current passing through a gas makes a fluorescent lamp
shine.

The colour of the display depends on the gas being ionised. At Tromso,
the lights are mostly green, one of the colours of oxygen atoms. They are
often fringed with red, one of the colours of nitrogen molecules, or a different
shade of red from ionised hydrogen atoms. The lights hang like a curtain,
stretching from one side of the sky to the other, but may break into shorter
segments. This is because the current is discharging along magnetic field
lines, which run almost perpendicular to the surface of the Earth at these
high latitudes, forming a cylinder centred on the magnetic pole.

Arctic Light also touches on research taking place near Tromso that
uses high power radar to bounce signals off the particles of the solar wind
to record their movements. ĐÓ°ÉÔ­´´s have also sent rockets tearing through
the solar wind at speed, recording their journey. For good measure, the
film gives a glimpse of the midnight Sun, as well as debunking some common-sense
platitudes. No, the Sun does not always rise in the east and set in the
west. For a month either side of midsummer, it rises and sets briefly in
the north. On 21 January, the Sun makes its first appearance at Tromso for
two months, rising and setting immediately afterwards in the south.

Do not expect too much serious science on your visit to the planetarium.
Some of the shots in the film are getting long in the tooth: for example,
those of the orange digital counters used for the rocket launches. It does
give a general background to the lights and helps visitors to know what
to look for in the night sky.

February and September tend to be slightly drier months, with less cloud
in the sky from the warm, moist air from the Gulf Stream, and so can be
good times for sightings. Photography is a problem. A long exposure may
be needed even with a fast film and full aperture and, because the lights
flicker, pictures will often show only a blur.

The solar activity that causes sunspots follows an 11-year cycle, as
do the northern lights. The last peak, the best in recent decades, was in
1991, so if you plan a visit, the sooner the better.

James Bedding is a freelance writer.

The 260-year-old astronomical observatory at Jaipur looks like something
between an adventure playground and a sculpture park. To a 20th-century
visitor brought up on the familiar minimalist shapes of the world’s great
optical and radio tele-scopes, Jaipur’s yellow masonry towers, gracefully
curving flights of steps and underground hollows look as if they belong
to religion rather than science.

Then in astronomy, as now, big was beautiful. Dominating the pale yellow
theme park of giant geometrical triangles, circles and cylinders is the
world’s biggest sundial, which towers 27 metres above the jumble of instruments
below.

Physical fitness must have been a necessary qualification for astronomers
in the early 18th century in India. The ones at Jaipur would have had to
clamber up and down the long flights of steps that spiral the sundial and
other instruments, in order to place their eye against the graduated scales
that coil around the structures from which they made their observations.

Jaipur is the biggest and most dramatic of five observatories, or Jantar
Mantars, that the astronomer noble Maharajah Jai Singh II built throughout
northern India in the 1720s so that he could refine the star charts. A Hindu
prince in the court of a Muslim Mogul emperor, he was one of the last of
the great astronomers in the Islamic tradition.

In the same way that schoolchildren learn to calculate the thickness
of a coin accurately by measuring a large pile and finding the mean, Jai
Singh set out to improve the accuracy of his measurements by creating huge
instruments that would slash his observational margin of error.

Jai Singh set up five observatories altogether, starting with the pink
prototype at New Delhi, now within easy walking distance of the main airline
offices in Connaught Circus. After Jaipur, he built Ujjain (known as the
Greenwich of India, as it was the geographical and astronomical reference
point for all calculations in Hindu astronomy), Mathura (which has since
disappeared) and at the holy city of Varanasi (now, sadly, in a state of
neglect).

At Jaipur, the 27-metre-high gnomon casts the shadow on the sundial.
The gnomon is in the shape of a right-angled triangle whose hypotenuse is
parallel to the Earth’s rotational axis and so points to the celestial pole.
The shadow falls on two vast quadrants which have a radius of 15 metres,
parallel to the Earth’s equator, and travelling at approximately 1 millimetre
a second.

The shadow is diffuse – because the Sun appears in the sky as a disc
and not a point – but astronomers could still make accurate measurements
by observing the edge of the Sun’s disc emerge from behind the gnomon. At
night, the stars and planets would not cast a visible shadow, but astronomers
could still measure the apparent movement of the stars and planets, to the
nearest second, by ‘placing the eye’ next to the graduated quadrant.

This meant clambering up the giant steps along the side of the graduated
scales. Visitors who have the energy can do this for themselves. The observatory
is great for people who don’t like things in glass cases, for here you climb
all over the exhibits.

It requires quite a bit of imagination to work out what some of the
instruments are for. It took me, a keen amateur, two visits to the observatory
in Delhi and one to Jaipur to get my brain round them. Brief explanations
posted on each instrument hardly help, and none of the other visitors seemed
much wiser.

You can buy guide books on site – the Delhi observatory sells a reprint
of a 1918 text for 45 rupees, while at Jaipur you can buy a shorter but
rather confused guide for 30 rupees. Be prepared to spend a couple of hours
twist-ing your brain around celestial equators, celestial meridians, zeniths,
azimuths and ecliptic obliquity (an exercise not helped by the concise guide
book, which muddles celestial equators and ecliptics.) To really get to
grips with the instruments, you have to wade through pages of three-dimensional
geometry, and try and match the abstract numbers and angles with the yellow
shapes around you.

Even if you cannot work out what everything is for, the instruments
are still fun to explore. Together they involve hundreds of metres of graded
scales laid out in geometrical configurations. The instruments are so large
that astronomers had to crawl inside most of them to be able to ‘place their
eye’ near to the correct scale. This meant there had to be gaps in the scales
for the scientists to crawl around. For this reason, Jai Singh had many
of the instruments built in complementary pairs: if an observation fell
on a gap in one instrument, then it always fell on a scale on the twin.

Jai Singh’s obsession with accuracy was not just an academic interest.
He served under the emperor Mohammed Shah, and the empire was run on the
Muslim calendar. Accurate astronomical information helped to predict the
lunar cycle, which was the basis of the Muslim calendar, including such
important dates as the beginning and end of the holy month of Ramadan. Accurate
star charts also helped travellers locate cities and routes for the pilgrimage
to Mecca.

With these observatories, Jai Singh achieved what he set out to do:
to refine and improve the existing star tables. But on the global scene,
he had ended up in a backwater. Jai Singh, like the Arab and Muslim astronomers
who he followed, focused on making increasingly accurate measurements of
the sky. Meanwhile in Europe, scientists were working out the implications
of the new conception of the Universe based on the discoveries of Copernicus,
Kepler, Galileo and Newton, who Singh was probably unfamiliar with. His
main contact with European science seems to have been through Jesuit priests,
who would probably have been hostile to the new science.

As it was, Jai Singh’s ‘science expired on his funeral pyre’ alongside
his wives, as his biographer remarked, something of a dead end in a rapidly
changing world. Yet he did succeed in his object: to rectify the calendar
and improve the prediction of astronomical events. His observatories remain
as remarkable monuments to his sponsorship of science in an age when astronomical
research was virtually stagnant outside Europe.

The Jantar Mantars are open daily. General information from Government
of India Tourist Office, 88 Janpath, New Delhi (Tel: (010) 91 11 332 0005)
or local tourist offices in Jaipur and Ujjain. One of the best guides is
The Astronomical Observatories of Jai Singh by G. R. Kaye, first published
in 1918 and now available from the Archaeological Survey of India, Janpath,
New Delhi.

James Bedding is a freelance journalist and travel writer.

The colossal cooling towers of the power station at the head of the
Ironbridge Gorge in Shropshire seem at least ten sizes too big. They make
the dainty valley feel like a miniature scale model in a museum.

Strange, then, to think that 200 years ago this valley was the most
industrialised corner of the world. The tourist guides trumpet it as the
birthplace of the Industrial Revolution, for it was in the iron foundries
of the area that pioneers produced technological innovations which made
modern industry possible.

The kindling for the revolution was lit by Abraham Darby in Coalbrookdale,
next to Iron-bridge, when he experimented in 1709 with smelting iron ore
with coke instead of charcoal. At the time the growth of the iron industry
was limited by the shortage of charcoal-already most of the country’s forests
had been chopped down. Using coke, made from local coal, meant that the
foundries could start producing iron cheaply on a vast scale.

You can make the pilgrimage to where it all began, the original furnace
where Darby first used coke. The guide book says solemnly it is ‘the most
important industrial monument in the world’. Industrial archaeol-ogists
have protected it under a modern pyramid, of metal and glass, that makes
it feels like a shrine. Inside the dark, silent cavern are the ruins of
the furnace; you can climb up on top and look into the black hollow where
red-hot iron ore was reduced to molten metal. Even with the hype, it feels
awesome.

The furnace is one of a group of archaeological sites and museums along
the gorge which try to make the early Industrial Revolution come alive.
They are impressive, though you have to be selective-to visit the lot would
take a couple of days.

Next door to the furnace is the museum of iron, which shows how the
expertise of the Shropshire ironmasters inspired other great innovators,
such as Thomas Telford, Richard Trevithick and John Nash. Trevithick ordered
the cylinders for the first steam locomotive to be cast in the Coalbrookdale
foundries in 1802.

But most people in the mid-18th century needed convincing as to the
potential of the heavy material. As a publicity stunt, Darby’s grandson
built the world’s first large iron bridge in 1781. A single 100-foot span
across the foaming Severn resting on elegant semicircles of steel, it gave
the gorge its new name and acted as a spectacular advertisement for how
far iron technology had developed.

It cannot have been a pleasant place for most people to live, though.
To find out how life used to be, visit the open air museum at Blists Hill,
which tries to recreate the atmosphere of a working town of about 1905 to
1910. Most of the buildings have been taken from other sites and carefully
reassembled brick by brick.

Blists Hill is the liveliest place to visit, especially for kids, and
is worth a good half day. One family could barely cope with their nostalgia.
‘Progress!’ Dad scoffed. ‘Now that’s a machine you could rely on!’ he said
pointing to the David and Samson, a double steam-driven bellows that pumped
a houseful of air into the iron furnace every minute.

The staff, dressed in period clothes, tell you about life in the community
as they work. They admit some of the materials are not authentic: the candlemaker
now uses paraffin instead of animal tallow. At the turn of the century they
made the tallow by leaving animal fat to fester in the rat-and maggot-infested
roof for about six weeks.

The pharmacy doubled as the opticians and dentist. Behind a glass screen,
engraved with ‘Teeth carefully removed’, is a primitive foot-powered dentist’s
drill and a reclining chair covered in velvet the colour of congealed blood.
‘That was called a jaw-breaker,’ the pharmacist said, pointing to something
like a gimlet with a vicious-looking hook on the end. ‘They used to extract
teeth with it,’ she explained in a jaunty Welsh accent, ‘only sometimes
the jaw would break.’

Down the hill is the squatters cottage-so called because it was a simple
house built on employer’s or common land so that a worker could be close
to work. An old woman was living in the two-room hovel until 1977. In 1861,
though, it was home to a cobbler, his wife, three coal-miner sons, two daughters
who worked picking iron ore on pit banks, a schoolboy son Matthew, and a
10-year-old visitor called William.

At that point the nostalgic Dad stooped under the low wooden doorway
and squeezed into the living room the size of a bus stop. ‘That’s cosy,’
he said. ‘I wish we could have a real fire at home.’

The Ironbridge Gorge Museum (which also includes a china museum, a tile
museum, a restored ironmaster’s home and other sites) is open every day
except Christmas Day, although some sites close during winter. A passport
ticket, valid indefinitely and which allows you to visit all the sites,
costs ÂŁ6.95 and ÂŁ4.50 for children. Tel: 0952 4535622.

You can reach Ironbridge via the M54, turning off for Telford which
is also the nearest railway station. As the museum sites are spread over
nearly 6 square miles, check first with Shropshire Travel Line (0345 056785)
if you want to use local buses from Telford.