PCBs and PBDEs
The article on “the new PCBs” associated polybrominated diphenyl ethers (PBDEs) and polychlorinated biphenyls (PCBs) (25 May, p 25).
PBDEs themselves are composed of three distinctly different commercial products, penta-BDE, octa-BDE and deca-BDE. PBDEs are not “banned in much of Europe” and widespread environmental findings are limited to the constituents of penta-BDE.
The restrictions are indeed currently limited to penta-BDE, the PBDE that most toxicological studies focus on鈥擡d.
Slippery concept
Steven Reitci raised an interesting point concerning non-lethal weapons that function as “Lubricant and Grease Additives for Immobilizing Machinery” (1 June, p 56). Lubricants have often proved more trouble than they’re worth in battle. After all, one of the major problems faced by the Germans on the Russian front was that, in the winter of 1941-42, the freezing grease on their tank tracks actually immobilised more German tanks than the Red Army did.
What I’d like to know is why the MoD haven’t literally taken a leaf out of Railtrack’s book, and proposed mass bombing raids to sprinkle the wrong kind of leaves in the path of advancing enemy columns. Works a treat against trains, after all.
Correction
An In Brief item “Wolf dogs” credited only the lead author of the study (4 May, p 27). Ettore Randi and Vittorio Lucchini at the National Wildlife Research Institute in Bologna, Italy, did the genetic analysis mentioned.
Good sleep, bad sleep
Thank you for justifying my afternoon kip in your article on siestas (1 June, p 9). I wonder if the performance of the Spanish workforce is deteriorating now the practice is less common.
Letter
Those who take the advice to “sleep with the boss” should be warned that New 杏吧原创 has previously published reports indicating that those who take midday siestas are more likely to suffer from cardiac problems (24 June 2000, p 13).
How likely are you?
The calculation by Charles Lineweaver and Tamara Davis of the probability of life arising on an Earth-like planet, based on how quickly life started here (18 May, p 15), has a fatal flaw.
Our planet is not just any old life-bearing planet. It is a planet that at the age of 4.6 billion years has intelligent life. So it is obvious that life on this planet had to start early, in order to give enough time to get to humankind. This is basically the “weak anthropic principle”, which says, “Well, of course things are special. Otherwise we wouldn’t be here asking the question.”
We really have no idea whether there is other intelligent biological life in the visible Universe. It could be that we are the only example, even though there are millions of other planets just the right distance from the right kind of star and so on. If this is the case, then it might be very surprising that life developed, but given how far life has come here, it is not surprising that it started quickly.
Queen Elizabeth may find it very surprising that she happens to be queen, but given that fact, it’s not a surprise that she was the daughter of a king.
All fished out
You rightly ask for scientific judgement over fishing (8 June, p 4). This is all the more urgent as we have only recently realised that stocks of fish like cod can completely disappear at very low numbers. This used to be thought unlikely since a codfish lays thousands of eggs in the hope that at least two will survive predators to replace her and her mate. So in theory there are always enough eggs to boost the stocks back to abundance.
But in practice it doesn’t work like that. At a certain point, the fewer adult cod there are around, the fewer eggs will survive. If thousands of codfish all lay their eggs at the same time, this keeps the predators busy and substantial numbers survive. Once cod numbers have fallen to a certain level the predators can catch up, eat all the eggs鈥攁nd the fish are “goners”.
Clearly a return is then impossible. It may be difficult to know the exact cut-off point, but at least we can acknowledge its existence鈥攁nd that for some stocks, we may be reaching it.
"Trapped" radiation
The conclusion that cellphone radiation is “trapped” in train carriages (4 May, p 23) was based on a simplistic and unrealistic analysis with no direct relevance to the scenario it purported to explore.
There are well-established international guidelines for assessing safe human exposure to radio waves. The paper that served as the basis for your article veered from these accepted principles and was seriously flawed in: (1) assuming a train car to be a metallic cavity, devoid of contents; (2) assuming that mobile phones could be used in a car devoid of passengers; (3) assuming that the sum of all radio-frequency (RF) sources in the car could have a significant impact on individual exposure; and (4) drawing conclusions about safety from an inappropriate RF “reference level”.
RF emissions are not “trapped” in a train car. They disperse, are absorbed and dissipate in intensity. Moreover, mobile phones are built and tested to meet “basic restriction” exposure limits (expressed in SAR) that protect against any known adverse health effects. Contrary to the assertion of the author, these guidelines do indeed cover settings with multiple sources.
Researcher Tsuyoshi Hondou replies: We used a simple model to assess the cumulative effects of electromagnetic fields from mobile phones in trains so that we can clearly show any effects that emerge. We modelled only three parameters: the carriage volume, the dissipation probability and the total output power of each phone. The result revealed some undiscovered phenomena that can now be investigated with more detailed models.
We did not assume that a train car was a completely metallic cavity. We introduced windows as a source of energy dissipation. In a train carriage, there are indeed other contents, like seating. However, I cannot imagine that this is critical. In a microwave oven, there are several things between the target food and the microwave source鈥攕uch as the plastic that covers the source and the cookware. This does not deeply decrease the efficiency of the microwave oven.
As Motorola says, the presence of passengers can indeed change the average exposure level in a train because they absorb the radiation. But as we said in our paper in the Journal of the Physical Society of Japan, the effect of that absorption can form part of the average dissipation probability calculation.
Dawkins and Darwin
If Theodore Roszak had thoroughly read Richard Dawkins’s books, he might not feel quite so puzzled (25 May, p 56). I do not believe that anywhere in his work has Dawkins advocated a Darwinian stance towards “human social and political affairs”. As many readers are aware, Dawkins has said, from the beginning, we can “rebel against the tyranny of the selfish replicators”. It is a tediously common mistake to believe that Dawkins has purported anything else. While our genes may be selfish, it does not necessarily follow that human behaviour must be similarly selfish.
Our innate free will has provided us with the ability to choose. To use Dawkins’s example, many people choose to use contraception, for varying reasons. And each time they do so, they make a choice their genes could not make. There is no fundamental contradiction in accepting the selfish gene theory, and not being an absolute determinist. If anyone (including Roszak) is still unconvinced, they ought to read Dawkins’s second book, The Extended Phenotype.
How we live in Israel
We’ve enjoyed your magazine for years, and have come to respect its balance in presenting opposing views. On reading Michael Bond’s article on what life is (sadly) like for the Palestinians (11 May, p 40), we thus assumed it would be followed by another, describing in equal detail how we live in Israel, where we part company these days with “may you have a quiet day” (meaning “may no one close to you die in the next suicide bombing”). We turned the page 鈥� no second article.
The bias was obvious at a glance: we counted 11 photos showing Palestinians, almost all children, and only 2 of our countrymen, all soldiers. We have children too, you know, every bit as stressed by the terror they face daily. You chose to interview only one Israeli鈥攁nd you picked a Hebron settler, a member of a tiny extremist group. You gave no mouth to countless ordinary Israelis, whose fervent hopes and actions for peace have been shattered.
Our intention with this series of articles was not to take sides. The series principally concerned the roots of terrorism, including a visit to an area that, as we wrote, is the “perfect breeding ground” for “violence and a desire for martyrdom”. Israel is not carrying out acts of terrorism or suicide bombings; that is why we focused more of our article on Gaza and the West Bank. (We could equally have chosen to visit parts of Sri Lanka, or even Northern Ireland).
Our approach was unusual. Rather than examining the past (all the thousands of years of politics and history that led us to this point) we asked “what are the actual conditions on the ground?”, and “how do they perpetuate hate and destroy communication?” As a science magazine, we believe that a rational approach to the understanding of human nature and to the direct causes of terrorism may pay dividends. The message from another article in the same issue was that “even such extreme behaviour is in principle comprehensible”. The message from this one was that there is little hope of peace when there is no communication and only dehumanisation鈥擡d
Religion is the scapegoat of history
One would think, from your correspondents, that the world would not know war if it were not for religion (1 June, p 56). Ownership of land is probably the main cause of war, as can be seen today in the dispute over Kashmir and 11 years ago over Kuwait.
That is not to deny that religion lies at the heart of many wars, but such wars stem from the fear people have of being ruled by those who have a different set of beliefs to themselves. However, not all these beliefs are religious beliefs. Some are political and some are nationalist beliefs. There is the belief in the liberation of the oppressed peoples of the world and the belief in defending the free world against such people. It was the fear of the socio-economic beliefs of the other side that drove the nuclear arms race.
Belief is a basic human imperative and we will no doubt continue to wage wars because of it. Perhaps these wars could be avoided if we were to take responsibility for the diversity of our beliefs instead of making religion the scapegoat of history.