Driving home from our grocery shopping this Saturday, Lisa and I saw a pyrocumulus cloud rising up from the mountains behind San Bernardino. It turned out to be the start of the so-called Sheep fire, which later burnt close to the mountain community of Wrightwood. The above photo, not by me, is a closeup of the source of the pyrocumulus I saw.
Yes, there are enough fires around here that
we learn words like pyrocumulus. Indeed, you can see a picture of a pyrocumulus
cloud on my September 1st
October 11, 2009
I got a nice email in response to my
comment about incipient
type 2 diabetes. Lorenz Borsche is an old acquaintance from the
days when I spent a lot of time on sci.physics and sci.physics.research.
His mail brings back good memories:
There's an interesting critical review of Taubes' book here:
Mancher lehnt eine gute Idee bloss deshalb ab, weil sie nicht von ihm ist. - (Luis Bunuel)
you may remember my name from former times in s.p. and s.p.r. (when one still could read and write there...). Actually I was searching for your crackpot index and came to read lots of your homepage (since it's Sunday morning, raining outside, my wife at the gym etc...).
Finally I read the notice on your high blood sugar. I privately 'researched' the whole subject some three years ago — and didn't come to any other conclusions than are pinned down by Gary Taubes in his absolutely stunning book:
I often think of how you once described how Millikan's oil drop measurement was so off track but the real value was only reached by small steps over generations of laboratry re-runs, where no one dared to exceed the error limits... I can't find that post, which is a pity, as it stands as a vivid example of how things can develop over time even in the precise 'natural sciences' (the posting must have been in the mid/end-90ies in s.p.). Reading Taubes you may often see analogies to the oil drop experiment.
BTW: No need to worry, if you change your food, the high blood sugar will completely go away and no D II will arise.
Mit herzlichen Grüssen / Cordially yours
Lorenz Borsche | http://www.borsche.de
In 2003, while geneticist Svante Pääbo was visiting Novosibirsk, Russia's third-largest city, he decided to look in on a famous experiment run by the Institute of Cytology and Genetics, which is based in the city. Fifty years ago, the then head of the IC&G, geneticist Dmitry Belyaev, had begun breeding silver foxes to see how easily they could be tamed. What Pääbo didn't know, though, is that Belyaev had also set up another experiment in the 1970s involving rats. This time, one line of rats was selected for tameness and another selected for aggression.
When Pääbo saw them, he was stunned. After just 30 years of selection, the IC&G researchers had fashioned two populations that could hardly be more different. "I could take the tame ones out of the cage with my bare hands. They would creep under my shirt and seemed to actually seek and enjoy contact," recalls Pääbo. "The aggressive animals were so aggressive I got the feeling that 10 or 20 of them would probably kill me if they got out of the cages."
The Environmental Protection Agency, or EPA, has released a secret Bush-era document! In December 2007, the EPA concluded that greenhouse gas emissions from motor vehicles were endangering public welfare and needed to be regulated. But the Bush administration covered this up. Until now, only a few members of Congress have been allowed to see this document. See it yourself.
The fun starts on page 7:
Carbon dioxide is the most important GHG [greenhouse gas] directly emitted by human activities, and is the most significant driver of climate change.
Now I can turn all my coffee grounds, banana peels, leaves and weeds into something useful: compost. Instead of feeling vaguely guilty for throwing them out, I now feel virtuous. And I'm actually looking forward to watching them rot!
Composting is a lot of fun, because it lets you watch something very fundamental to life on this planet: the transformation of dead plant matter back into soil. Of course animals and even us people turn back into soil... but don't put animal products into your compost, unless you want to attract critters!
Here's the best quick guide to composting:
Cooler? Yes, decomposition creates heat, and this is important! Below 13°C (55° F) most microbes are almost dormant — not much decomposition will occur. In the range of 13-21°C (55-70°C), the cool-loving psychrophiles will wake up and begin to oxidize the pile, warming it up. This in turn activates the next shift: the mesophiles. These are microbes that do well in the range of 21-32°C (70-90°F). This crew does most of the work... but in an ideal compost pile, they set the stage for their own exit by heating the pile still further. As temperatures rise to 32-60°C (90-140°F), the thermophiles take over. These kill disease germs and weed seeds, and generate humic acids — the brown acids that are major constituents of humus.
As the thermophile's food runs out, the pile will cool, and the mesophiles and psychrophiles move back in from the cooler edges.
I don't know any of this from experience — I just read it.
But hopefully in a few months or years it'll be familiar and intuitive.
This reminds me of my father, who could never resist a bad pun: he
said that as a soil scientist, he had a good sense of humus.
October 23, 2009
Speaking of compost, San Francisco recently
passed a law that
gives householders, apartments and businesses just 6 weeks to start throwing
their food waste and plant trimmings into a
cart, where it's taken away to be composted. The compost is then
sold to Bay area farms and vineyards:
San Francisco already manages to recycle 72% of its waste. Now that may go up to 90%!
And now some bad news — or at least a warning, which I hope comes in time:
As we approach the Egyptian border, we are 20 days' ride from our starting point west of Omdurman, across the Nile from Sudan's capital, Khartoum. We're bound for the place all camel herds go from Western Sudan, the camel market in Daraw, north of Aswan, Egypt, a journey of 1250 kilometers (775 miles). From there, the camels will be loaded onto trucks and shipped to Cairo, home of the largest camel market in the Middle East.
The trail arcs gently northwest through Sudan and then curves northeast into Egypt, along the palm-lined Nile. Starting in savanna covered with dry grass and acacia trees on which the camels feed, the trail reaches pure sand desert in the northernmost third of the country. The traveler does not see vegetation again until the trail joins the Nile.
Sudan has nearly three million camels, the second-largest national herd in the world, after Somalia's. Nearly one and a half million square kilometers (580,000 sq mi) of territory is suitable for their grazing — an area more than twice the size of Texas and three times as large as Spain. Approximately a third the size of the United States, Sudan is the largest country in Africa, sparsely populated with 27 million people.
Kharga Oasis - photo by Hanne Siegmeier
The journey from Omdurman to Daraw takes approximately 30 days, yet herders still refer to this route as Darb al-Arba'in, the Forty Days' Road. The historic Forty Days' Road connected the el-Fasher area of Sudan with Assiut in Egypt, via the Selima and Kharga Oases. This was the path followed by the great ancient camel caravans of old, a trade route dating back at least 700 years.
I urge you to read the full story — and try the version with pictures! My mother subscribes to Saudi Aramco World in part for the remarkable photos. It's a propaganda magazine put out by an Saudi oil company — that's why you can get a free subscription. But it has lots of informative articles on Islamic culture and history, which tend to lean strongly in the positive direction. For example, the above story doesn't mention that the Forty Days' Road was famous for the transportation of slaves.
There's a book by Angela Stephens and Lorraine Chittock that goes into a lot more detail, with lots of great photos:
The founding principles of efficient-market theory are easily described. The assumption on which all else rests is that, unless one has private knowledge, there is no way to profit from financial markets without risk. Admittedly, some securities are as safe as humans can make them, and they do pay returns, notably bonds issued by the U.S. Treasury. (Whatever else he does, Uncle Sam pays his debts.) The rates of return on these next-to-riskless instruments are, however, extremely low. Other kinds of securities pay returns that are, on average, higher, but these returns are more variable.there is some nontrivial risk of getting back less than the amount one has invested, or getting back nothing at all. The basic idea of efficient-market theory is that anything that pays higher returns than the risk-free rate must also be more risky. There should be no opportunities for arbitrage (making money from riskless trades that exploit price discrepancies between markets). Moreover, the trade-off between risk and return must be the same across different assets: If stock A was as risky as stock B, but A paid lower returns than B, people would sell A, lowering its price and raising its rate of return, and buy B, with the opposite effect — arbitrage in which the arbitrageurs put themselves out of business.The second tackles the game-theoretic notion that people act rationally to maximize their happiness:
Classically, there is a very specific idea — the "capital asset pricing model" — about how the risk-reward trade-off is supposed to go, at least for stocks. The return on a portfolio of several stocks is an average of those stocks' returns. More diversified portfolios are less exposed to the risks peculiar to individual companies, leaving only the risks common to the whole corporate sector. The returns for each stock, then, are supposed to combine a firm-specific term, alpha, and the firm's correlation with the economy as a whole, beta. Higher returns, in this scheme, compensate for higher betas — that is, for risk that cannot be mitigated by diversification.
One corollary is important enough to count as a principle itself. Legend relates that J. P. Morgan, when asked what the stock market would do the next day, replied, "It will fluctuate". Someone who could predict these fluctuations (or their absence) could increase their returns with no extra risk. Therefore, says efficient-market theory, securities prices are unpredictable. Current prices are supposed to be optimal forecasts, on the basis of currently available data, of the present value of future returns, because changes in optimal forecasts are, themselves, unpredictable. (If you know that tomorrow your forecast of next year's gasoline price will be higher than today's forecast by $1, you should raise your current forecast.) As Paul Samuelson put it, "properly anticipated prices fluctuate randomly". The efficient-market hypothesis, as a technical term, is the claim that market prices cannot be predicted, either from past prices alone or from past prices combined with other publicly available information. One of the early triumphs of the school was the demonstration that stock prices look very much indeed like random walks.
By now it is clear that the efficient-market school has been interestingly ambivalent about arbitrage and arbitrageurs. On the one hand, the assumption that there are no opportunities for arbitrage is the basis for all calculations. On the other hand, for all prices to be exactly right at all times is too much to ask, and arbitrageurs have been invoked as the restoring force pulling prices back to equilibrium. There is something almost Taoist about the assertion that arbitrage is so powerful and ubiquitous that it cannot be seen. Alas for paradoxes, this view is actually incoherent, as the effort that goes into figuring out what prices should be can only be compensated if prices are not fully efficient. But this leaves open the possibility that prices are close to efficient, without systematic deviations.
A vast superstructure was erected on these foundations, beginning in the 1950s and really taking off in the 1960s and 1970s. Particularly impressive wings of that edifice were devoted to the design of portfolios to balance risk against return and to the valuation of derivative securities ("contingent claims" or bets on the value of other securities), especially options to buy or sell stocks at given prices by given dates. As Fox notes, scholars of finance achieved acclaim, and were awarded substantial consulting fees, for solving pricing problems that by hypothesis were already being solved by the markets themselves! (Donald Mackenzie's An Engine, Not a Camera explores this paradox in depth.)
By the 1980s and 1990s, these ideas had led to changes in the way the investment industry worked, new concepts of corporate governance and new kinds of financial firms, which aimed to systematically identify arbitrage opportunities — deviations from what the theory said prices should be — and to earn a profit even as they eliminated those opportunities. More diffusely, the academic prestige of efficient-market theory provided, at the least, rhetorical support for deregulating markets, especially financial markets, and delegating more and more authority to them. This was aided by a conflation — subscribed to by many scholars — between those markets having informationally efficient prices (that is, unpredictable ones) and those markets allocating capital efficiently (directing savings to where the money can be used most profitably). The latter is the more usual economic notion of efficiency, but informationally efficient prices are neither necessary nor sufficient for efficient allocation.
The whole edifice, however, has turned out to be built, if not on sand, then at best on loose fill. More rigorous testing on larger data sets has shown that the capital asset pricing model does not fit the data...
This is a great blog for armchair adventurers like me. Starting in January 2006, Carolyn McIntyre undertook to retrace the journeys of the Moroccan scholar Ibn Battuta, which lasted from 1326 to 1354 and covered North Africa, West Africa, Southern and Eastern Europe, the Middle East, India, Central Asia, Southeast Asia and China! For a nice tale of his journey, try this:
And then there's this:
From Timbuktu I sailed down the Nile on a small boat, hollowed out of a single piece of wood. - Ibn Battuta
© 2009 John Baez