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Common-or-garden rainbows, gorgeous as they are, are by no means the only spectra worth looking out for in the sky. A host of of other beautiful, colourful effects await the attentive, caused by the refraction and diffraction of sunlight by water droplets and ice crystals in the atmosphere. Most people will never see them because they so rarely pay any attention to what's going on above their heads. Here are a few which you're quite likely to spot if you keep an eye out, and you'll be glad if you do:

Rainbow
Rainbows are caused by light bouncing once off the insides of raindrops; the colours occur because different colours (wavelengths) of light are refracted by different amounts.

Double Rainbow
Many rainbows have a double on the outside, with the colours the opposite way round from the main bow. This is caused by light bouncing around the inside of water droplets twice. A third bow, caused by light bouncing three times, is easily seen in the lab but almost never in the sky.

Supernumerary Rainbow
Occasionally a rainbow has many extra bands of colour close together on the inside. These supernumerary bows show the interference pattern created by light waves leaving droplets; their visibility depends on how uniformly sized the droplets are.

22º Halo
A coloured ring around the sun, caused by refraction from a cirrostratus.

46º Halo
Like the 22º Halo only bigger, weaker and much rarer.

Sun Dogs
Patches of rainbow at the same elevation as the sun, on top of or just outside the 22º halo depending on how high the sun is in the sky. These are the result of refraction by horizontally-aligned plate-like ice crystals in cirrus clouds. Most of the time they come in pairs, with one either side of the sun.

Circumzenith Arc
A rainbow-arc partway around the zenith of the sky, among the most spectacular of all aerial spectra. These are produced by the same kind of ice crystals as sun dogs, and are therefore likely to occur at around the same time.

Corona
A coloured ring pretty close to the sun or moon, caused by diffraction from water droplets in an altostratus or altocumulus layer. Droplets of different sizes give different-sized coronas, so the effect is smeared out if the sizes of the droplets vary too much. Although beautiful and common, the corona around the sun is usually much too bright to look at, which is why most people have never even noticed it. The night-time version, around the moon, is much less interesting thanks to the narrower spread of wavelengths in moonlight and our reduced sensitivity to colours at low light levels.

Warning: Do not try to look for bright colours in the clouds immediately surrounding the sun without proper sunglasses! Even with strong shades, take great care not to look for too long at a time, and block the sun out of your view.


For more information visit:

www.cloudman.org
www.bbc.co.uk/weather
www.sundog.clara.co.uk/atoptics/phenom.htm

Or read:

The Flying Circus of Physics, by Jearl Walker
Weather Watching, by Mary & John Gribbin

Yellow-billed magpie

The black-billed magpie (Pica pica) occurs across Europe, Asia, North Africa and western North America, an exceedingly common bird.

The yellow-billed magpie (Pica nuttalli), identical in appearance to its black-billed relative except for bill color, occurs only in an area about 500 miles north to south and about 150 miles across, in the central part of California. Within that limited range they are quite common, nesting in colonies in groves of tall trees. They are most numerous in open country and where riverside groves of oaks, cottonwoods and sycamores border upon farmland. They are omnivorous, eating whatever they can get, from acorns to carrion to grasshoppers...whatever is available. Their nests are a bit smaller than those of the black-billed magpie (a domed structure more often two feet in diameter than the three feet of the latter species), and they tend to lay fewer eggs. Black-billed magpies fledge (leave the nest) in 25 - 29 days. The fledging time for yellow-billed magpies is not known.

All magpies are noisy and rather aggressive, from the family Corvidae, which also includes the crows, the jays and the ravens. Like their relatives, intelligent, adaptable birds.

But....what's with the yellow bill? And the other slight but perhaps important differences? How did this come about? Why only in Central California? Was one bird, long ago, a mutant and spread this mutation across this area only? The two, black-billed and yellow-billed, do not occur together. In California, the black-billed magpie is found only in the Sierra Nevada Mountains and to the east (all the way across the center of the continent); the yellow-billed only in the Central Valley.

One of nature's little puzzles. Perhaps DNA studies could answer some of these questions, but in a world of limited funding, where we have far more important (to us) matters to investigate than yellow-billed magpies, the answer may never be known. The magpies, so far as we can tell, don't care.

____________________

For the factual information see Kaufman, Kenn, Lives of North American Birds, Houghton Mifflin Company, Boston, New York, 1996

The Real Science Behind Sex Differences

Delusions of Gender, by Cordelia Fine, is an extended critique of efforts to scientifically study differences between the sexes, and the efforts of many writers to apply alleged science in their writings about such differences. The book is rich in technical detail, which might bog down some readers, but most of those details are fascinating. Fine is a lucid and entertaining writer, especially in her more acerbic moments - of which there are plenty here. She finds a lot of shoddy science and shameless misuse of would-be science that would raise the hackles of any neuroscientist or feminist, let alone someone like her who happens to be both.

This is a book with an agenda, and political agendas tend not to sit comfortably with science - but to pretend that politics never seeps into science while nobody is looking would be disingenuous. In fact, Fine's agenda - to bring out the reasons to doubt science that supposedly demonstrates innate differences between sexes - is at least as much scientific as political, and I think it is legitimate. It is something to bear in mind while reading this book, though, and there are times she goes out of her way to present things in such a way as to minimise the possibility of interpretation in terms of innate differences. As far as I can see she always stops short of misrepresenting the science, though, and the whole approach needs to be seen in the context of discourse which routinely takes essential differences for granted, whether the evidence supports them or not.

The book is divided into three parts. The first is 'Half-changed World', Half-Changed Minds, which largely focuses on the interplay of cultural expectations and attempts to measure sex differences scientifically. This largely consists of accounts of experiments demonstrating the effects of cultural norms on things that people might be interested in measuring, and experiments which fail to take these factors into account. For example, she looks at experiments investigating the effect of telling the subjects what 'the latest science' has to say about the sorts of tests they are about to perform, to show that girls do significantly better on mathematical tasks if they think that science says they should. Even more subtly, females rate their mathematical ability as worse after they have just been reminded of their sex by having to tick a box at the beginning to say they are females. This gives us an interesting lens for looking at gender differences in maths tests which disregard the weight of cultural expectations, and indeed at systematic tendencies for females to choose less mathematical study and career paths.

Having established many profound and subtle ways that social expectations and structures shape behaviours and perfomance, the theme of the second part of the book is Neurosexism - premature efforts to explain differences in behaviour and performance with reference to the brain, rather than society. Fine's most basic point is that it is rather soon to be looking for explanations of most of these things in neuroscience, when societal explanations have not been ruled out, and the relationship between the mind and the brain is still so unclear. More than that, she shows time and again that many authors are disturbingly willing to go way beyond what neurology can tell us, while pretending that they are not. Perhaps the single worst offender here is Louann Brizendine, author of The Female Brain, a serial abuser and inventor of neuroscience to back up her ideas about the differences between males and females - but she is one of many. Fine makes the point that people have been finding 'explanations' for sex differences in the brain for well over a century, from the observation that female brains tend to be a bit lighter than male ones through to modern notions of hardwiring. At the same time, people have routinely assumed that all kinds of observed differences between the sexes are natural and inevitable, when later experience has regularly shown them to be no such thing.

The final section is titled Re-Cycling Gender, and it concerns itself with the future of gender relations and the science of sex. Fine is worried about the cyclical nature of some kinds of self-fulfilling prophecy - about dodgy science being used to teach yet another generation of young men and women that there are certain natural roles that they ought to be filling, certain characteristics they should expect to have. She emphasises again how difficult it is to pick apart innate and culturally conditioned differences, and the importance of keeping an open mind about questions that science has not yet been able to settle. With a better scientific understanding of the role of society in forming the mind and the brain, and a sceptical eye on the interesting but inconclusive findings of neuroscience, we may approach true sexual equality yet. Without such circumspection, as Fine argues, we may find ourselves sliding back to ideas about the sexes which are both unhelpful and ill-founded.

This is an important book, because the trend towards explaining sex differences with impressive-sounding neurological findings has great potential to set back ideas about gender roles, on the basis of evidence which is far flimsier than it might look. Because we are shaped by our ideas, this has major practical, political ramifications - it is not just good science that is at stake here. There is no doubt that some will resist Fine's approach for its politicisation of science, but I would be inclined to see it more as exploring the role of pre-existing, unexamined political bias, rather than introducing politics to the debate. Delusions of Gender is compelling, informative and perhaps most impressively, funny. I recommend this highly to anyone with any interest in neuroscience or gender.

Literally, "hidden life." When an animal or plant becomes so inactive that its life processes almost come to a stop, it is said to enter cryptobiosis. There are a surprising number of organisms which can do this, including plants (as seeds), many kinds of spores, rotifers, nematodes, collembolans, tardigrades, the eggs of some crustaceans, and the larvae of at least one insect, Polypedilum vanderplanki (an African midge).

The phenomenon is best documented among the tardigrades and other minute inhabitants of mosses and lichens, where the water film essential for active life is transient and sporadic. When the film dries out these animals appear to be dead for periods of days, weeks, or even years until moisture returns, when they 'come back to life' and resume their normal activities.

Entering cryptobiosis involves various processes. The animal typically retracts its legs and other appendages, or curls up into a ball to minimize its surface area. Biochemical changes in the cuticle or the secretion of wax ensure that at least some water is retained, although this may be only some 5% of the normal content, and the body and the internal organs contract and shrivel. Sugars manufactured by the body cells protect the integrity of the cell membranes and also convert the cytoplasm to a glasslike state. Absorbing water reverses these processes.

Besides allowing survival during dry periods, the overall lifespan of the organism may be hugely increased by lengthy periods of cryptobiosis; also the dry form may be easily carried by the wind to a new environment, allowing the spread of these mostly tiny organisms which would otherwise have very limited mobility.

"Give me a half a tanker of iron and I'll give you the next ice age."
-- Oceanographer John Martin (Joking), in a 1991 speech.


Iron fertilization is a theoretical but not promising type of geoengineering that attempts to stimulate carbon sequestration in the ocean by way of algal blooms.

Because iron is insoluble in salt water, and because it is a necessary nutrient for photosynthesis in plants, adding iron to the sea will stimulate an algal bloom. The theory is that plankton will absorb atmospheric carbon dioxide while they grow, and upon their death will sink to the ocean floor, where the carbon in their corpses will be ensconced safely in the collecting sediment of the sea-floor.

The general mechanics of this process have been known for decades, but what really set things off was the 1991 eruption of Mount Pinatubo in the Philippines. It ejected about ten cubic kilometers of material, much of which fell into the oceans as ash. This included perhaps 18,000 cubic meters of iron dust, and did indeed stimulate algal blooms; over the next year the expected increase in atmospheric carbon dioxide fell significantly short, by the greatest amount seen in the 35-year history of the NOAA Mauna Loa Earth System Research Laboratory. This was accompanied by an increase in atmospheric oxygen equal to what you would expect if the carbon deficit had been caused by an oceanic algal bloom. (It is worth noting that the eruption of Mount Pinatubo also cooled the Earth by 0.9 degrees Fahrenheit by releasing light-colored sulfur particles and other aerosols into the atmosphere, reflecting the sun's rays back into space; this is called atmospheric seeding, and is another possible method of geoengineering).

Experimentation has had mixed results. It appears that the basic theory is sound enough, but getting things to work in practice is difficult. For iron fertilization to be effective at reducing atmospheric carbon, it has to take into account the other nutrients present (diatoms are best at sequestering carbon, but require silicic acid), the probability that the dead phytoplankton will rest in situ and not be eaten -- while at the same time, hopefully, keeping the existing ecosystems healthy. We also, obviously, have limited data on the long term effects.

And on the flip side, iron fertilization is cheap and easy enough that private citizens can do it themselves. The Haida Salmon Restoration Corp. recently made international news when they dumped "100 tonnes of an iron-rich dirt-like material" into the waters off of British Columbia's north coast in order to produce a plankton bloom in order to feed local salmon, in an attempt to increase the salmon populations. This was funded, in part, by American businessman Russ George, founder of the geoengineering firm Planktos Inc. He has undertaken similar projects in the past, in the hopes that he may help reverse climate change. Critics point out that we don't know what these sorts of actions might be doing to the ecosystem, and that the risk is not worth the payoff. They have a point -- the recent dump in British Columbia is considerably larger than any formal experiment ever undertaken.

This isn't completely uncharted territory, however. Natural iron fertilization occurs when an upwelling of nutrient-rich water brings iron to the surface of the ocean. This may happen when ocean currents come up against a seamount or a shoal; rivers feeding into the sea, dust-rich winds, and volcanic eruptions may also be the cause of iron fertilization. Regular sources of iron fertilization create stable and rich ecosystems; it is not the existence of iron that is the problem, only the introduction of large amounts of it suddenly into new areas. Because there are a number of naturally iron-rich zones in the oceans, most iron fertilization experiments take place in High Nitrate, Low Chlorophyll (HNLC) zones.



References:
Wikipedia: Iron Fertilization
Wikipedia: Iron Hypothesis
Metal Ions in Biological Systems by Astrid Sigel
Duke University: Nicholas School of the Environment: Assessing the Pros and Cons of Geoengineering to Fight Climate Change
AWI: LOHAFEX: An Indo-German iron fertilization experiment
Huffington Post: Iron Sulfate Haida Gwaii Dump Defended
CBC News: Iron fertilization project stirs West Coast controversy
Wikipedia: Russ George