No way no-fly
The theorist behind the idea about equipment meant to keep aircraft out of no-fly zones is surprised that pilots show hostility towards this idea (5 July, p 15). Frankly, I am not. Any such system would be highly complex, probably adding to the danger rather than reducing it, and could even be abused by the very terrorists it is supposed to thwart.
In emergencies, airplanes often land at air force bases around the world, irrespective of no-fly areas. This would be impossible with enforced no-fly zones. Also, the aircraft might try to override the pilots, increasing the danger.
The system works by modifying the avionics so that the plane fights any efforts by the pilot to fly into restricted areas. But anyone with an understanding of aircraft systems knows that you can shut off all avionics and still maintain hydraulic power to the flight controls. In order to maintain the no-fly zone in this instance, the flight controls would have be shut down as soon as power to the avionics was lost. Hardly a viable solution.
Customised hacking
Contrary to what Duncan Graham-Rowe suggests, SCADA programs don’t create a “one attack fits all” scenario that hackers can exploit (5 July, p 38). SCADA programs don’t do anything until an individualised, customised application has been constructed to control a specific process. So, a hacker has to have detailed knowledge of that process being controlled, as well as the specific SCADA application program customised to control it.
On top of this, the developers have built in layers of password protection, biometrics readers and so on, to ensure only authorised operators or staff have access to the application for changing the process parameters. This is not to say that there aren’t serious security issues to discuss. But a malicious hacker would have to take an extremely complex route to negotiate his way from keyboard and mouse to the actuator controlling, for example, fuel rods.
Flat batteries
Your piece about the Italian company that charges batteries contained a serious historical inaccuracy (Feedback, 5 July). This obviously reflects your tender years and therefore can be forgiven.
You did not take your radio to be recharged, just the low-tension (LT) battery. Back in 1952, when I was 10, all the houses in the street where I lived had mains electricity, except for one, owned by an elderly lady, that only had gas. I earned pocket money by taking her LT battery to the local charging station (Abel & Smith’s electrical shop), where I would leave the flat cell and return later to collect a fully charged one.
The lady owned a valve radio that ran off batteries 鈥� note the plural. There was the rechargeable LT battery that heated the filaments of the valves, usually a single-cell, lead-acid accumulator with screw terminals. The other two batteries were non-rechargeable zinc chloride.
This same lady introduced me to electronics by giving me a very early radio (from around 1925) with four valves, crystal detector and headphone audio. It never worked so I dismantled it for the parts. To this day I still have the valves in stock, waiting for a suitable project.
Butterflies' dolls
I’m surprised that Feedback appears to be unaware what butterflies (both male and female) do with dolls (12 July).
During their caterpillar phase, butterflies have the benefit of a broad and classically based education (unlike Feedback, it would seem), and so they usually prefer to use the Latin word for dolls 鈥� pupae.
For the record
鈥� The Natural History of a Garden, reviewed 12 July (p 45), was co-authored by Sir Colin Spedding and his son Geoffrey: apologies to the latter.
Close the markets
We concur with your story on how SARS has shut down live animal markets in China (5 July, p 10). What stuns us, however, is the adamant refusal of US government agencies to take similar action here. Live Chinese food markets abound in those US cities with large numbers of Chinese residents.
American Tortoise Rescue (ATR) and other animal welfare groups have been trying to close down the live food markets where animals are kept in horrendous and unsanitary conditions before they are eaten. Blood and faeces tests on the animals, including rabbits, turtles, frogs, fish, coatis and raccoons, reveal salmonella, tuberculosis, leprosy and a range of other zoonotic diseases easily transmitted to humans. Since 1995, ATR has repeatedly brought hard evidence of this to local, state and federal agencies to no avail.
The California Department of Fish and Game, the US Department of Agriculture, Los Angeles County and the California Department of Health, among others, have deliberately stayed away from this political hot potato because closing the markets would mean angering Chinese voters. The USDA official I spoke to said: “Lady, we don’t inspect fish. Why would we inspect turtles and raccoons?”
Our reason for closing the live markets is twofold: to prevent Chinese and other shoppers contracting serious and sometimes fatal infections, and to prevent the inhumane treatment of helpless animals. Yet we have been labelled racists. Now, with the closing of the live markets in China because of SARS, we call on government officials to close live markets here in the US as well.
Prophets of panspermia
Paul Davies’s article on where we came from disposes of three decades of serious work on this subject by Fred Hoyle and myself in one dismissive sentence (12 July, p 32). The main problem with life on Earth coming from somewhere else in the universe, says Davies, “is the high levels of radiation in space, which could prove lethal to all known microorganisms in fairly short order” (12 July, p 32). I disagree. Panspermia, although unpopular in some circles, is by no means ruled out by any scientific data, and remains a major contender amongst theories of the origins of life.
The requirement for the operation of interstellar panspermia is that a fraction of 1 in 1021 microbes remains in a viable state at the time when a new comet system condenses from interstellar matter around a fledgling star. Bacteria are easily protected against damaging ultraviolet rays in space by the formation of a thin carbonaceous layer, which is an inevitable consequence of their residence in interstellar clouds.
Doses of ionising radiation that some types of microbes (for example, Micrococcus radiodurans) can tolerate under lab conditions run into tens of thousands of grays. But even normally non-resistant microbes can be seen to have residual fractions after large exposure doses, if the dose response curves are properly (linearly) extrapolated for high dose values.
Oil helps forests
Two corrections are necessary regarding your article about oil wealth helping to conserve forests (5 July, p 6).
First, the author says that according to UN data, Gabon lost around 5 per cent of its forests during the 1990s, which would seem to be at odds with our hypothesis claiming that oil revenues protect forests. But this annual loss of 0.5 per cent is based on outdated statistics. The UN Food and Agriculture Organization (FAO) is the only UN agency producing deforestation data. According to the FAO’s Global Forest Resources Assessment 2000, Gabon’s yearly deforestation is actually 10,000 hectares, or only 0.1 per cent of forest area.
The FAO’s country notes, available at , actually cite our draft Gabon chapter as a main source justifying this major revision. In other words, despite a population growth of about 3 per cent, Gabon has maintained a static land-use pattern and extraordinarily low deforestation by both sub-Saharan and tropical standards. Oil is certainly a principal reason.
Secondly, contrary to what was stated by Ricardo Carrere of the World Rainforest Movement, neither I as the author of the Oil Wealth and the Fate of the Forest report, nor the Center for International Forestry Research as an institution, endorse taking people out of the forests and encouraging oil and mining companies to manage forests.
On the contrary, we strongly encourage modes of forest management that have a high degree of local control. The implications of our study have been misinterpreted. Our aim is to encourage recognition of the fact that some of the activities of some of these companies unwittingly result in forest conservation. How exactly one takes advantage of this fact to benefit society and the environment remains open to debate.
Spotting WMDs
Hazel Morris’s article on the use of satellites to hunt for buried treasure was surprising because it did not mention that the ground-penetrating capacity of P-band imaging radar is obviously relevant to the search for buried caches of weapons of mass destruction in Iraq (12 July, p 12).
NASA and its contractors Boeing and McDonnell Douglas have been investigating P-band potential for over 10 years, and have developed an experimental airborne system. It is reasonable to suppose that this technology is available to the US military and intelligence community, perhaps even on a classified satellite.
As well as having ground-penetrating capability through dry materials, radar images mainly show variations in the texture of the Earth’s surface. Disturbed ground, as over recent excavations, clearly shows up on radar images produced by a wide range of microwave wavelengths.
Such imaging systems, including the commercial Canadian RADARSAT with its 15-metre resolution, have been in use for more than 20 years. This makes it rather odd that the US Secretary of State, Colin Powell, did not submit any imaging radar evidence to the UN Security Council on 5 February 2003.
Predictive talk
I was intrigued to read the statement: “If you want to guess what the 10th word is, the previous nine are of no value”, in your article on interstellar communication (12 July, p 36).
If people are presented with the sentence: “If you want to guess what the 10th word ____”, and told to guess what the 10th word is, I suspect there is a high probability that most would suggest “is”.
I found many more statements in the article where I felt I could predict the 10th word (such as: “The hope is that complexity relates in some way ____”, the word being “to”) but more often than not I couldn’t. So the statement is probably statistically true, even if not actually true to itself.
Letter
The regularities that can be found in a message, and which indicate the complexity of the communication, are precisely the same regularities that are exploited by a good compression algorithm.
It seems likely that any extraterrestrial signals will be compressed to save bandwidth, and hence will look more or less like noise. The only exception is signals that have been broadcast into the sky specifically in the hope that a distant civilisation will pick them up.
However, while the internal communications of an alien species might be directional 鈥� and hence we might, by chance, be in the right place to pick them up 鈥� signals intended for another civilisation will have to be sent out in all directions. Hence the chances of picking up signals which are recognisable as communication relies on extraterrestrials aiming them at us and intending them to be recognised, which, if it happens, will probably be because they broadcast something like a sequence of prime numbers.
So although I found this article fascinating and informative, the chances of it being put to practical use have to be 鈥� as the writer says 鈥� miraculous.